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9273f9d8464274c994ecb8f65231c11e6fb2a7a851ea8da71e04dce597acf905
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2026-01-23T00:00:00-05:00
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Existence and Non-Uniqueness of Ergodic Leray-Hopf Solutions to the Stochastic Power-Law Flows
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arXiv:2412.08622v2 Announce Type: replace Abstract: We study long time behavior of shear-thinning fluid flows in $d \geq 3$ dimensions, driven by additive stochastic forcing of trace class, with power-law indices ranging from $1$ to $ \frac{2d}{d+2}$. We particularly focus on Leray-Hopf solutions, i.e. on analytically weak solutions satisfying energy inequality. Introducing a new kind of energy related functional into the technique of convex integration enables the construction of infinitely many such solutions that are probabilistically strong for a certain initial value. Furthermore, we provide global i time estimates which lead to the existence of infinitely many stationary and even ergodic Leray--Hopf solutions. These results represent the first construction of Leray-Hopf solutions in the framework of stochastic shear-thinning fluids within this range of power-law indices.
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https://arxiv.org/abs/2412.08622
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9f14808bf4a72037b1408cc503db49d0a50b0dfa9f0c83fd52e6ac6402cad8b9
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2026-01-23T00:00:00-05:00
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$N=1$ super Virasoro tensor categories
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arXiv:2412.18127v3 Announce Type: replace Abstract: We show that the category of $C_1$-cofinite modules for the universal $N=1$ super Virasoro vertex operator superalgebra $\mathcal{S}(c,0)$ at any central charge $c$ is locally finite and admits the vertex algebraic braided tensor category structure of Huang-Lepowsky-Zhang. For central charges $c^{\mathfrak{ns}}(t)=\frac{15}{2}-3(t+t^{-1})$ with $t\notin\mathbb{Q}$, we show that this tensor category is semisimple, rigid, and slightly degenerate, and we determine its fusion rules. For central charge $c^{\mathfrak{ns}}(1)=\frac{3}{2}$, we show that this tensor category is rigid and that its simple modules have the same fusion rules as $\mathrm{Rep}\,\mathfrak{osp}(1\vert 2)$, in agreement with earlier fusion rule calculations of Milas. Finally, for the remaining central charges $c^{\mathfrak{ns}}(t)$ with $t\in \mathbb{Q}^\times$, we show that the simple $\mathcal{S}(c^{\mathfrak{ns}}(t),0)$-module $\mathcal{S}_{2,2}$ of lowest conformal weight $h^{\mathfrak{ns}}_{2,2}(t)=\frac{3(t-1)^2}{8t}$ is rigid and self-dual, except possibly when $t^{\pm 1}$ is a negative integer or when $c^{\mathfrak{ns}}(t)$ is the central charge of a rational $N=1$ superconformal minimal model. As $\mathcal{S}_{2,2}$ is expected to generate the category of $C_1$-cofinite $\mathcal{S}(c^{\mathfrak{ns}}(t),0)$-modules under fusion, rigidity of $\mathcal{S}_{2,2}$ is the first key step to proving rigidity of this category for general $t\in\mathbb{Q}^\times$.
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https://arxiv.org/abs/2412.18127
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d1a1f86db3b7c818f8b3745b1f478dae83a34f1143543564aec91fc02651b7b1
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2026-01-23T00:00:00-05:00
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Categorical Diffusion of Weighted Lattices
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arXiv:2501.03890v2 Announce Type: replace Abstract: We introduce a categorical framework for diffusion on network-structured data valued in weighted lattices, extending the Laplacian paradigm beyond the category of Hilbert spaces. Central to our approach is the Lawvere Laplacian, an endofunctor on the category of cochains of a cellular sheaf enriched in a commutative unital quantale. We establish the Tarski-Lawvere Fixed Point Theorem, generalizing Tarski's classical result to show that the suffix and prefix points of a quantale-enriched endofunctor form complete weighted lattices. Leveraging this, we prove the Hodge-Lawvere Theorem, which identifies the suffix points of the Laplacian with weighted global sections, providing a geometric characterization of equilibria. Finally, we derive a discrete-time harmonic flow that evolves data toward these sections, offering a constructive method for information aggregation in systems ranging from discrete event processes to preference dynamics.
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https://arxiv.org/abs/2501.03890
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22829a5ed96837daadd8cfed0ddd4540be54230f45beab2d9074c612f8d01d0a
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2026-01-23T00:00:00-05:00
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Geometrization of the local Langlands correspondence, motivically
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arXiv:2501.07944v2 Announce Type: replace Abstract: Based on the formalism of rigid-analytic motives of Ayoub--Gallauer--Vezzani, we extend our previous work with Fargues from $\ell$-adic sheaves to motivic sheaves. In particular, we prove independence of $\ell$ of the $L$-parameters constructed there.
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https://arxiv.org/abs/2501.07944
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735f151f2fd412b3a3eb5963aafd51f96dc2dcb0f0f65dca1755d8fb201d6167
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2026-01-23T00:00:00-05:00
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Explosive appearance of cores and bootstrap percolation on lattices
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arXiv:2501.18976v2 Announce Type: replace Abstract: Consider the process where the $n$ vertices of a square $2$-dimensional torus appear consecutively in a random order. We show that typically the size of the $3$-core of the corresponding induced unit-distance graph transitions from $0$ to $n-o(n)$ within a single step. Equivalently, by infecting the vertices of the torus in a random order, under two-neighbour bootstrap percolation, the size of the infected set transitions instantaneously from $o(n)$ to $n$. This hitting time result answers a question of Benjamini. We also study the much more challenging and general setting of bootstrap percolation on two-dimensional lattices for a variety of finite-range infection rules. In this case, powerful but fragile bootstrap percolation tools such as the rectangles process and the Aizenman-Lebowitz lemma become unavailable. We develop a new method complementing and replacing these standard techniques, thus allowing us to prove the above hitting time result for a wide family of threshold bootstrap percolation rules on the $2$-dimensional square lattice, including neighbourhoods given by large $\ell^p$ balls for $p\in[1,\infty]$.
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https://arxiv.org/abs/2501.18976
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656f1673d2726e8056624a5625b5cae932f64f3e57b4e5644ef1498536e26099
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2026-01-23T00:00:00-05:00
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Local geometry of high-dimensional mixture models: Effective spectral theory and dynamical transitions
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arXiv:2502.15655v3 Announce Type: replace Abstract: We study the local geometry of empirical risks in high dimensions via the spectral theory of their Hessian and information matrices. We focus on settings where the data, $(Y_\ell)_{\ell =1}^n \in \mathbb{R}^d$, are i.i.d. draws of a $k$-Gaussian mixture model, and the loss depends on the projection of the data into a fixed number of vectors, namely $\mathbf{x}^\top Y$, where $\mathbf{x}\in \mathbb{R}^{d\times C}$ are the parameters, and $C$ need not equal $k$. This setting captures a broad class of problems such as classification by one and two-layer networks and regression on multi-index models. We provide exact formulas for the limits of the empirical spectral distribution and outlier eigenvalues and eigenvectors of such matrices in the proportional asymptotics limit, where the number of samples and dimension $n,d\to\infty$ and $n/d=\phi \in (0,\infty)$. These limits depend on the parameters $\mathbf{x}$ only through the summary statistic of the $(C+k)\times (C+k)$ Gram matrix of the parameters and class means, $\mathbf{G} = (\mathbf{x},\boldsymbol{\mu})^\top(\mathbf{x},\boldsymbol{\mu})$. It is known that under general conditions, when $\mathbf{x}$ is trained by online stochastic gradient descent, the evolution of these same summary statistics along training converges to the solution of an autonomous system of ODEs, called the effective dynamics. This enables us to connect the training dynamics to the spectral theory of these matrices generated with test data. We demonstrate our general results by analyzing the effective spectrum along the effective dynamics in the case of multi-class logistic regression. In this setting, the empirical Hessian and information matrices have substantially different spectra, each with their own static and even dynamical spectral transitions.
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https://arxiv.org/abs/2502.15655
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95b47e7a4a9a189260d9308bf559479f83bee3cf67e842549f04b78253830277
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2026-01-23T00:00:00-05:00
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Integer-valued valuations
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arXiv:2502.21144v2 Announce Type: replace Abstract: We obtain a complete characterization of planar monotone $\sigma$-continuous valuations taking integer values, without assuming invariance under any group of transformations. We further investigate the consequences of dropping monotonicity or $\sigma$-continuity and give a full classification of line valuations. We also introduce a construction of the product for valuations of this type.
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https://arxiv.org/abs/2502.21144
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1231a907b984aca8c52f39b1334df96b688632d8b105b3d47476b8d5aa8db609
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2026-01-23T00:00:00-05:00
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Uniqueness of gauge covariant renormalisation of stochastic 3D Yang-Mills-Higgs
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arXiv:2503.03060v2 Announce Type: replace Abstract: Local solutions to the 3D stochastic quantisation equations of Yang-Mills-Higgs were constructed in (arXiv:2201.03487), and it was shown that, in the limit of smooth mollifications, there exists a mass renormalisation of the Yang-Mills field such that the solution is gauge covariant. In this paper we prove uniqueness of the mass renormalisation that leads to gauge covariant solutions. This strengthens the main result of (arXiv:2201.03487), and is potentially important for the identification of the limit of other approximations, such as lattice dynamics. Our proof relies on systematic short-time expansions of singular stochastic PDEs and of regularised Wilson loops. We also strengthen the recently introduced state spaces to allow finer control on line integrals appearing in expansions of Wilson loops.
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https://arxiv.org/abs/2503.03060
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f928766b379788507a87c52620eda4239f0a8fb0a9e3b5281c66f76514440fa0
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2026-01-23T00:00:00-05:00
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An isoperimetric inequality for lower order Neumann eigenvalues in Gauss space
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arXiv:2503.15813v5 Announce Type: replace Abstract: We prove a sharp isoperimetric inequality for the harmonic mean of the first $m-1$ nonzero Neumann eigenvalues for bounded Lipschitz domains symmetric about the origin in Gauss space. Our result generalizes the Szeg\"o-Weinberger type inequality in Gauss space, as proved in [8, Theorem 4.1].
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https://arxiv.org/abs/2503.15813
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6a4cb409ee9be604469dd15c06fac5944139c92ac26988cd57e44bf47a75d4be
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2026-01-23T00:00:00-05:00
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The rationality problem for multinorm one tori
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arXiv:2504.04078v3 Announce Type: replace Abstract: In this paper, we study the rationality problem for multinorm one tori, a natural generalization of norm one tori. For multinorm one tori that split over finite Galois extensions with nilpotent Galois group, we prove that stable rationality and retract rationality are equivalent, and give a criterion for the validity of the above two conditions. This generalizes the result of Endo (2011) on the rationality problem for norm one tori. To accomplish it, we introduce a generalization of character groups of multinorm one tori. Moreover, we establish systematic reduction methods originating in work of Endo (2001) for an investigation of the rationality problem for arbitrary multinorm one tori. In addition, we provide a new example for which the multinorm principle holds.
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https://arxiv.org/abs/2504.04078
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03ca97465f0e798ca7e78a4712d34b57433553fd78af8fa3fe3e6038947127a7
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2026-01-23T00:00:00-05:00
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On manifolds with almost non-negative Ricci curvature and integrally-positive $k^{th}$-scalar curvature
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arXiv:2504.06865v3 Announce Type: replace Abstract: We consider manifolds with almost non-negative Ricci curvature and strictly positive integral lower bounds on the sum of the lowest $k$ eigenvalues of the Ricci tensor. If $(M^n,g)$ is a Riemannian manifold satisfying such curvature bounds for $k=2$, then we show that $M$ is contained in a neighbourhood of controlled width of an isometrically embedded $1$-dimensional sub-manifold. From this, we deduce several metric and topological consequences: $M$ has at most linear volume growth and at most two ends, it has bounded 1-Urysohn width, the first Betti number of $M$ is bounded above by $1$, and there is precise information on elements of infinite order in $\pi_1(M)$. If $(M^n,g)$ is a Riemannian manifold satisfying such bounds for $k\geq 2$, then we show that $M$ has at most $(k-1)$-dimensional behavior at large scales. If $k=n={\rm dim}(M)$, so that the integral lower bound is on the scalar curvature, assuming in addition that the $(n-2)$-Ricci curvature is non-negative, we prove that the dimension drop at large scales improves to $n-2$. From the above results we deduce topological restrictions, such as upper bounds on the first Betti number.
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https://arxiv.org/abs/2504.06865
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591f142b2e8fc981f787505363b55c00fca05b3fa2d2f551c246c9bb185d49ad
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2026-01-23T00:00:00-05:00
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Morita equivalences, moduli spaces and flag varieties
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arXiv:2504.09293v2 Announce Type: replace Abstract: Double Bruhat cells in a connected complex semisimple Lie group $G$ emerged as a crucial concept in the work of S. Fomin and A. Zelevinsky on total positivity and cluster algebras. These cells are special instances of a broader class of cluster varieties known as generalized double Bruhat cells, which can be studied collectively as Poisson subvarieties of $\widetilde{F}_{2n} = \mathcal{B}^{2n-1} \times G$, where $\mathcal{B}$ is the flag variety of $G$. The spaces $\widetilde{F}_{2n}$ are Poisson groupoids over $\mathcal{B}^n$ and were introduced by J.-H. Lu, V. Mouquin, and S. Yu in the study of configuration Poisson groupoids of flags. In this work, we describe the spaces $\widetilde{F}_{2n}$ as decorated moduli spaces of flat $G$-bundles over a disc. This perspective yields the following results: (1) We explicitly integrate the Poisson groupoids $\widetilde{F}_{2n}$ to symplectic double groupoids, which are complex algebraic varieties. Furthermore, we show that these integrations are symplectically Morita equivalent for all $n$. (2) Using this construction, we integrate the Poisson subgroupoids of $\widetilde{F}_{2n}$ formed by unions of generalized double Bruhat cells to explicit symplectic double groupoids. As a corollary, we obtain integrations for the top-dimensional generalized double Bruhat cells contained therein. (3) Finally, we relate our integration to the work of P. Boalch on meromorphic connections. We lift the torus actions on $\widetilde{F}_{2n}$ to the double groupoid level and show that they correspond to the quasi-Hamiltonian actions on the fission spaces of irregular singularities.
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https://arxiv.org/abs/2504.09293
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20ea6697366b7202fc822ba24d3db0c1846424f26e7aeac1dc96f4bcafa6bbcb
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2026-01-23T00:00:00-05:00
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Deza graphs and regular polyhedra
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arXiv:2504.19204v2 Announce Type: replace Abstract: We classify all regular polyhedra according to their type i.e., the collection of numbers of common neighbours that any pair of distinct vertices may have (polyhedra are planar, $3$-connected graphs). As an application, we recover the classification of planar Deza graphs. Next, we focus on the class of quartic polyhedral Deza graphs, and completely characterise it in terms of medial graphs of certain specific cubic polyhedra. Furthermore, within the aforementioned class of quartic polyhedral Deza graphs, we study the extremal graphs with respect to the ratio of number of triangular faces to the total. In the maximal extreme, these notably coincide with the class of line graphs of cubic polyhedra of girth $5$. We also fully characterise the quartic polyhedra of type $\{0,1,2,3\}$, and in particular we prove that none of them are medial graphs. On one hand our findings fit within the novel research area of common neighbours in graphs. On the other hand, our findings imply general properties of regular planar graphs and regular polyhedra.
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https://arxiv.org/abs/2504.19204
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d525e08f8c4a0c390ba969c3c61270a614c30a507d13a2f35c5ef8057632da56
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2026-01-23T00:00:00-05:00
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Towards the Colmez Conjecture
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arXiv:2505.06541v2 Announce Type: replace Abstract: We prove a collection of results involving Colmez's periods and the Colmez Conjecture. Using Colmez's theory of periods of CM abelian varieties, we propose a definition for the height of a partial CM-type and prove that the Colmez conjecture follows from an arithmetic period formula for surfaces. We give an explicit conjecture for the form of this period formula, which relates the height of special points on a Shimura surface with special values of $L$-functions. Further, we relate the heights of periods given by Colmez to arithmetic degree of Hermitian line bundles and thus give a formulation of Colmez's full conjecture in geometric terms.
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https://arxiv.org/abs/2505.06541
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823885322b3c6b4fb0d57056faac9c2147bed458d69a639abbf7bf172aa44b26
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2026-01-23T00:00:00-05:00
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Configurations, Tessellations and Tone Networks
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arXiv:2505.08752v5 Announce Type: replace Abstract: The Eulerian tonnetz, which associates three minor chords to each major chord and three major chords to each minor chord, can be represented by a bipartite graph with twelve white vertices denoting major chords and twelve black vertices denoting minor chords. This so-called Levi graph determines a configuration of twelve points and twelve lines in $\mathbb R^2$ with the property that three points lie on each line and three lines pass through each point. Interesting features of the tonnetz, such as the existence of the four hexatonic cycles and the three octatonic cycles, crucial for the understanding of nineteenth-century harmony and voice leading, can be read off directly as properties of this configuration $\{12_3\}$ and its Levi graph. Analogous tone networks together with their Levi graphs and configurations can be constructed for pentatonic music and twelve-tone music. These and other new tonnetze offer the promise of new methods of composition. If the constraints of the Eulerian tonnetz are relaxed so as to allow movements between major and minor triads with variations at exactly two tones, the resulting bipartite graph has two components, each generating a tessellation of the plane, of a type known to Kepler, based on hexagons, squares and dodecagons. When the same combinatorial idea is applied to tetrachords of the 'Tristan' genus (dominant sevenths and half-diminished sevenths) the cycles of the resulting bipartite graph are sufficiently ample in girth to ensure the existence of a second configuration $\{12_3\}$, distinct from the Eulerian tonnetz as an incidence geometry, which can be used for a new approach to the analysis of the rich tetradic harmonies of the nineteenth century common practice.
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https://arxiv.org/abs/2505.08752
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f77fdffac21094ab4a91e659f5a15e6c335511d3e84421c040daeb96400eae90
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2026-01-23T00:00:00-05:00
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Determining $t$-motives and dual $t$-motives in Anderson's theory
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arXiv:2505.12779v2 Announce Type: replace Abstract: Anderson t-modules are analogs of abelian varieties in positive characteristic. Associated to such a t-module, there are its t-motive and its dual t-motive. When dealing with these objects, several questions occur which one would like to solve algorithmically. For example, for a given t-module one would like to decide whether its t-motive is indeed finitely generated free, and determine a basis. Reversely, for a given object in the category of t-motives one would like to decide whether it is the t-motive associated to a t-module, and determine that t-module. In this article, we positively answer such questions by providing the corresponding algorithms. As it turned out, the main part of all these algorithms stem from a single algorithm in non-commutative algebra, and hence the first part of this article doesn't deal with Anderson's objects at all, but are results on finitely generated modules over skew polynomial rings.
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https://arxiv.org/abs/2505.12779
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94d98bd3a49bce2819d6bc4d13f20ddced32e1f9143677a6e14d8a3396813b98
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2026-01-23T00:00:00-05:00
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Stack-sorting preimages and 0-1-trees
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arXiv:2505.18295v2 Announce Type: replace Abstract: We define a class of partially labeled trees and use them to find simple proofs for two recent enumeration results of Colin Defant concerning stack-sorting preimages of permutation classes.
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https://arxiv.org/abs/2505.18295
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34a75f565828fe82ca9ed5edaa23effd3142dfbd0c9bc7e135a3f1163d5d8236
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2026-01-23T00:00:00-05:00
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On the Markoff spectrum on the Hecke group of index six
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arXiv:2506.08358v2 Announce Type: replace Abstract: The discrete part of the Markoff spectrum on the Hecke group of index 6 was determined by A.~Schmidt. In this paper, we study its Markoff and Lagrange spectra after the smallest accumulation point $4/\sqrt3$. We show that both the Markoff and Lagrange spectra below $4/\sqrt{3} + \epsilon$ have positive Hausdorff dimension for any positive $\epsilon$. We also find maximal gaps and an isolated point in the spectra.
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https://arxiv.org/abs/2506.08358
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8fa8510804c4602e33e1fc3061e7ae49d3ae06ff1d42cf162852937a0766d45a
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2026-01-23T00:00:00-05:00
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Vector bundles on bielliptic surfaces: Ulrich bundles and degree of irrationality
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arXiv:2506.10696v2 Announce Type: replace Abstract: This paper deals with two problems about vector bundles on bielliptic surfaces. The first is to give a classification of Ulrich bundles on such surfaces $S$, which depends on the topological type of $S$. In doing so, we study the weak Brill-Noether property for moduli spaces of sheaves with isotropic Mukai vector. Adapting an idea of Moretti, we also interpret the problem of determining the degree of irrationality of bielliptic surfaces in terms of the existence of certain stable vector bundles of rank 2, completing the work of Yoshihara.
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https://arxiv.org/abs/2506.10696
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f75c10ef6eb547dd80a9c6d4eb68e1c1e7f35b4adc391b31d854cf0cefa62d78
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2026-01-23T00:00:00-05:00
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Fare Game: A Mean Field Model of Stochastic Intensity Control in Dynamic Ticket Pricing
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arXiv:2506.13088v2 Announce Type: replace Abstract: We study the dynamic pricing of discrete goods over a finite selling horizon. One way to capture both the elastic and stochastic reaction of purchases to price is through a model where sellers control the intensity of a counting process, representing the number of sales thus far. The intensity describes the probabilistic likelihood of a sale, and is a decreasing function of the price a seller sets. A classical model for ticket pricing, which assumes a single seller and finite time horizon, is by Gallego and van Ryzin (1994) and it has been widely utilized by airlines, for instance. Extending to more realistic settings where there are multiple sellers, with finite inventories, in competition over a finite time horizon is more complicated both mathematically and computationally. We introduce a dynamic mean field game of this type, and some numerical and existence results. In particular, we analyze the associated coupled system of Hamilton-Jacobi-Bellman and Kolmogorov differential-difference equations, and we prove the existence and uniqueness results under certain conditions. Then, we demonstrate a numerical algorithm to find this solution and provide some insights into the macroeconomic market parameters. Finally, we present a qualitative comparison of our findings with airfare data.
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https://arxiv.org/abs/2506.13088
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047efb32dbe4a5159abab42766d20be580283f71cc7eaa3189f2607ed86b01e9
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2026-01-23T00:00:00-05:00
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Asymptotic Velocity Profiles for Homoenergetic Rayleigh-Boltzmann Flows under Dominant Shear
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arXiv:2506.15449v2 Announce Type: replace Abstract: In this paper, we study a particular class of solutions to the Rayleigh--Boltzmann equation, known in the nonlinear setting as \emph{homoenergetic solutions}. These solutions take the form $ g(x, v, t) = f(v - L(t)x, t),$ where the matrix $L(t)$ represents a shear flow deformation. We began our analysis in \cite{MNV}, where we rigorously proved the existence of a stationary non-equilibrium solution and established different behaviours of the solutions depending on the size of the shear parameter, for cut-off collision kernels with homogeneity parameter $0 \leq \gamma < 1$, thus including Maxwell molecules and hard potentials. In the present work, we focus on the regime in which the deformation term dominates the collision term for large times (hyperbolic-dominated regime). This scenario occurs for collision kernels with $\gamma < 0$; in particular, we focus on the range $\gamma \in (-1, 0)$. In this regime, it is challenging to obtain a clear and direct description of the long-time asymptotic behaviour of the solutions. Here we present a formal analysis of the velocity distribution's long-time asymptotics and derive for the first time the explicit form of the corresponding asymptotic profile. We also discuss the different asymptotic behaviour expected in the case of homogeneity $\gamma < -1$. In addition, we provide a probabilistic interpretation involving a stochastic process combining collisions with shear flow. The tagged particle velocity $\{v(t)\}_{t\geq 0}$ is a Markov process that arises from the combination of free flights in a shear flow along with random jumps caused by collisions.
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https://arxiv.org/abs/2506.15449
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f3c68186a5b832100f93951c086322a8e7c850832062b3f3180c0b0686da4173
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2026-01-23T00:00:00-05:00
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Direct reconstruction of general elastic inclusions
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arXiv:2507.04831v2 Announce Type: replace Abstract: The inverse problem of linear elasticity is to determine the Lam\'e parameters, which characterize the mechanical properties of a domain, from pairs of pressure activations and the resulting displacements on its boundary. This work considers the specific problem of reconstructing inclusions that manifest themselves as deviations from the background Lam\'e parameters. The monotonicity method is a direct reconstruction method that has previously been considered for domains only containing positive (or negative) inclusions with finite contrast. That is, all inclusions have previously been assumed to correspond to a finite increase (or decrease) in both Lam\'e parameters compared to their background values. We prove the general outer approach of the monotonicity method that simultaneously allows positive and negative inclusions, of both finite and extreme contrast; the latter refers to either infinitely stiff or perfectly elastic materials.
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https://arxiv.org/abs/2507.04831
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27b49e59c1bab65894b6cfc39174a9a7afaa25628d0d6f70aed654bdd74a0025
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2026-01-23T00:00:00-05:00
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Extension Operators for Fractional Sobolev Spaces on Lipschitz Submanifolds
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arXiv:2507.04869v2 Announce Type: replace Abstract: A well-known result is that any Lipschitz domain is an extension domain for $W^{s,p}$. This paper extends this result to Lipschitz subsets of compact Lipschitz submanifolds of $\mathbb{R}^n$. We adapt the construction of an extension operator for Lipschitz domains in arXiv:1104.4345v3 to manifolds via local coordinate charts. Furthermore, the dependence on the size of the extension domain is explicit in all estimates. This result is motivated by applications in numerical analysis, most notably geometry simplification, where the explicit dependence of the continuity constant on the domain size is essential.
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https://arxiv.org/abs/2507.04869
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1474a21ba580761710fd51d6b337d8281df3680dab6de34873e75cbe75919355
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2026-01-23T00:00:00-05:00
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Rigorous dense graph limit of a model for biological transportation networks
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arXiv:2507.15829v2 Announce Type: replace Abstract: We rigorously derive the dense graph limit of a discrete model describing the formation of biological transportation networks. The discrete model, defined on undirected graphs with pressure-driven flows, incorporates a convex energy functional combining pumping and metabolic costs. It is constrained by a Kirchhoff law reflecting the local mass conservation. We first rescale and reformulate the discrete energy functional as an integral `semi-discrete' functional, where the Kirchhoff law transforms into a nonlocal elliptic integral equation. Assuming that the sequence of graphs is uniformly connected and that the limiting graphon is 0-1 valued, we prove two results: (1) rigorous Gamma-convergence of the sequence of the semi-discrete functionals to a continuum limit as the number of graph nodes and edges tends to infinity; (2) convergence of global minimizers of the discrete functionals to a global minimizer of the limiting continuum functional. Our results provide a rigorous mathematical foundation for the continuum description of biological transport structures emerging from discrete networks.
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https://arxiv.org/abs/2507.15829
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786925e5b40b587b9c20d0a0706c679a4fa5efa3f716850e26705f2855835d98
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2026-01-23T00:00:00-05:00
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Large-Amplitude Steady Electrohydrodynamic Solitary Waves with Constant Vorticity
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arXiv:2508.01336v2 Announce Type: replace Abstract: This paper investigates solitary water waves propagating on the surface of a two-dimensional dielectric fluid subject to an electric field. The system is formulated as a nonlinear free boundary problem, with interfacial dynamics governed by the strong coupling between the Euler equations with constant vorticity and the electric potential equations. We aim to explore the effects of the electric field and constant vorticity on the nonlinear wave interactions in such a system, specifically examining whether large-amplitude solitary waves analogous to those in reference \cite{SVHMHW2023} exist. Although the inclusion of the electric field considerably complicates the analysis, we establish the existence of a continuous branch of large-amplitude solitary wave solutions. Moreover, along the global bifurcation curve, one of the following must occur: (i) the formation of an equilibrium stagnation point, (ii) the degeneration of the conformal mapping, (iii) the onset of flow stagnation, or (iv) an unbounded increase in the dimensionless wave speed.
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https://arxiv.org/abs/2508.01336
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c92533e1b435bfaa5fc6b541a955cda24b349858d2ceae8567658023f91af2e4
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2026-01-23T00:00:00-05:00
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The approach of cluster symmetry to Diophantine equations
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arXiv:2508.02005v3 Announce Type: replace Abstract: This paper aims to employ a cluster-theoretic approach to provide a class of Diophantine equations whose solutions can be obtained by starting from initial solutions through mutations. We establish a novel framework bridging cluster theory and Diophantine equations through the lens of cluster symmetry. On the one hand, we give the necessary and sufficient condition for Laurent polynomials to remain invariant under a given cluster symmetric map. On the other hand, we construct a discriminant algorithm to determine whether a given Laurent polynomial has cluster symmetry and whether it can be realized in a generalized cluster algebra. As applications, we solve Markov-cluster equations, describe some invariant Laurent polynomial rings, and resolve the questions posed by Gyoda and Matsushita.
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https://arxiv.org/abs/2508.02005
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1161e4ebe487e38077b930eea28bbac289cc28d5454a37081164d117734b0110
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2026-01-23T00:00:00-05:00
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Cup product of inhomogeneous Tate cochains, and application to tori over local fields that split over cyclic extensions
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arXiv:2508.07288v3 Announce Type: replace Abstract: In this note we give formulas for cup product in Tate cohomology in terms of inhomogeneous cochains. Using one of these formulas, for a torus T defined over a non-archimedean local field K and splitting over a cyclic extension of K, we compute explicit cocycles representing all cohomology classes in H^1(K,T).
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https://arxiv.org/abs/2508.07288
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97427cbdf0f073110de259413f4f07fc4f2549c8a69b687f919b5a5b5694abff
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2026-01-23T00:00:00-05:00
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Some generalizations of Camina pairs and orders of elements in cosets
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arXiv:2508.13056v2 Announce Type: replace Abstract: In this paper, we investigate certain generalizations of Camina pairs. Let $H$ be a nontrivial proper subgroup of a finite group $G$. We first show that every nontrivial irreducible complex character of $H$ induces homogeneously to $G$ if and only if for every $x\in G\setminus H$, the element $x$ is conjugate to $xh$ for all $h\in H$. Furthermore we prove that if $xh$ is conjugate to either $x$ or $x^{-1}$ for all $h\in H$ and all $x\in G\setminus H$, then the normal closure $N$ of $H$ in $G$ also satisfies the same condition, and $N$ is nilpotent. Finally, we determine the structure of $H$ under the assumption that for every element $x\in G\setminus H$ of odd order, the coset $xH$ consists entirely of elements of odd order.
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https://arxiv.org/abs/2508.13056
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3a44f15bbee5e0d8665778028c5f971e89329657774b9f0c4f5153a755bec089
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2026-01-23T00:00:00-05:00
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GW/DT invariants and 5D BPS indices for strips from topological recursion
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arXiv:2508.15459v2 Announce Type: replace Abstract: Topological string theory partition function gives rise to Gromov-Witten invariants, Donaldson-Thomas invariants and 5D BPS indices. Using the remodeling conjecture, which connects Topological Recursion with topological string theory for toric Calabi-Yau threefolds, we study a more direct connection for the subclass of strip geometries. In doing so, new developments in the theory of topological recursion are applied as its extension to Logarithmic Topological Recursion (Log-TR) and the universal $x$-$y$ duality. Through these techniques, our main result in this paper is a direct derivation of all free energies from topological recursion for general strip geometries. In analyzing the expression of free energy, we shed some light on the meaning and the influence of the $x$-$y$ duality in topological string theory and its interconnection to GW and DT invariants as well as the 5D BPS index.
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https://arxiv.org/abs/2508.15459
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0c4259a92453ab7423e625f842085f334c468d16858dde09999f22d644282e45
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2026-01-23T00:00:00-05:00
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Residual finiteness properties of some of Halls groups
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arXiv:2508.16452v3 Announce Type: replace Abstract: In this article we study a class of central extensions of $\mathbb{Z}\wr\mathbb{Z}$, as first described by Hall. On the one hand, we consider groups of this type with cyclic centre, our construction yields a rich class of groups. In particular we obtain a group that is conjugacy separable with solvable word problem but unsolvable conjugacy problem, we obtain a group with large conjugacy separability growth but small conjugator length function and residual finiteness growth, and we also obtain both a class of groups that for most functions $f:\mathbb{N}\rightarrow\mathbb{N}$ larger then $n^3$, contain a group $G$ such that the conjugator length of $G$ is given by $f$, as well as a group where the conjugator length is superlinear but subquadratic. On the other hand we also consider a different group with larger centre. This is the first example of a group where the residual finiteness growth is faster than any polynomial but slower than any exponential.
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https://arxiv.org/abs/2508.16452
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a1c631f2dad7b60add8c5c54adc7a8f4d6831967a61e8869a1cb0d7fc5b86057
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2026-01-23T00:00:00-05:00
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Dynamics from iterated averaging
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arXiv:2508.21416v3 Announce Type: replace Abstract: We prove that for a standard Lebesgue space $X$, the strong operator closure of the semigroup generated by conditional expectations on $L^\infty(X)$ contains the group of measure-preserving automorphisms. This is based on a solution to the following puzzle: given $n$ full water tanks, each containing one unit of water, and $n$ empty ones, how much water can be transferred from the full tanks to the empty ones by repeatedly equilibrating the water levels between pairs of tanks?
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https://arxiv.org/abs/2508.21416
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9f805e83602b51509e234e3b9e3ed5055863d507d6364096aed5101e62b65acd
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2026-01-23T00:00:00-05:00
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Time-inconsistent reinsurance and investment optimization problem with delay under random risk aversion
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arXiv:2509.15506v2 Announce Type: replace Abstract: This paper considers a newly delayed reinsurance and investment optimization problem incorporating random risk aversion, in which an insurer pursues maximization of the expected certainty equivalent of her/his terminal wealth and the cumulative delayed information of the wealth over a period. Specially, the insurer's surplus dynamics are approximated using a drifted Brownian motion, while the financial market is described by the constant elasticity of variance (CEV) model. Moreover, the performance-linked capital flow feature is incorporated and the wealth process is formulated via a stochastic delay differential equation (SDDE). By adopting a game-theoretic approach, a verification theorem with rigorous proofs is established to capture the equilibrium reinsurance and investment strategy along with the equilibrium value function. Furthermore, analytical or semi-analytical equilibrium reinsurance and investment strategies, together with their equilibrium value functions, are obtained under the CEV model for the exponential utility and derived under the Black-Scholes model for both exponential and power utilities. Finally, several numerical experiments are conducted to analyze the behavioral characteristics of the freshly-derived equilibrium reinsurance and investment strategy.
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https://arxiv.org/abs/2509.15506
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c936c56029230a95911c11fce4a1fc98e01bb2d972997155fc76f2a95a09d257
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2026-01-23T00:00:00-05:00
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A non-linear Roth theorem for thick Cantor sets
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arXiv:2509.17880v3 Announce Type: replace Abstract: We prove that for any function $f$ satisfying certain mild conditions and any Cantor set $K$ with Newhouse thickness greater than $1$, there exists $x\in K$ and $t>0$ such that \[ \{x-t,x,x+f(t)\}\subset K. \] This is an extension of previous work on the existence of three-term arithmetic progressions in Cantor sets to the non-linear setting.
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https://arxiv.org/abs/2509.17880
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b5931db159d7d106c67a0b7556faddd2dbe8c0c193a10d4f6dc94e1d9be5e8bd
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2026-01-23T00:00:00-05:00
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On the torsion-free nilpotent fundamental groups of smooth quasi-projective varieties of rank up to seven
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arXiv:2510.09026v2 Announce Type: replace Abstract: Let $X$ be a smooth quasi-projective variety. Assume that the (topological) fundamental group $\pi_1(X, x)$ is torsion-free nilpotent. We show that if the first Betti number $b_1(X) \le 3$, then $\pi_1(X, x)$ is isomorphic to either $\mathbb{Z}^n$ for $n = 1, 2, 3$, a lattice in the Heisenberg group $H_3(\mathbb{R})$ or $\mathbb{R} \times H_3(\mathbb{R})$. Moreover, we prove that $\pi_1(X, x)$ is abelian or $2$-step nilpotent if its rank is less than or equal to seven. More precisely, we determine the real nilpotent Lie groups in which torsion-free nilpotent fundamental groups can be embedded as lattices for ranks up to six and seven, respectively. Our main results are a partial positive answer to a question on nilpotent (quasi-)K\"ahler groups posed by Aguilar and Campana.
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https://arxiv.org/abs/2510.09026
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cd08cafb1dc08ea0ada217e9ecaf4f2b788758fd14663adeb2c09c180ddfa996
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General Casorati inequalities and implications for Riemannian maps and Riemannian submersions
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arXiv:2510.12760v2 Announce Type: replace Abstract: This paper presents general forms of Casorati inequalities for Riemannian maps and Riemannian submersions between Riemannian manifolds. Using these general forms, we obtain Casorati inequalities for Riemannian maps (resp. submersions) whose target (resp. source) spaces are generalized complex and generalized Sasakian space forms. As a consequence, we give Casorati inequalities for Riemannian maps (resp. submersions) when the target (resp. source) spaces are real, complex, real K\"ahler, Sasakian, Kenmotsu, cosymplectic, and almost $C(\alpha)$ space forms. To support these general forms, in the particular cases when the target or source spaces are real, complex, Sasakian, and Kenmotsu space forms, we verify known Casorati inequalities for Riemannian maps and Riemannian submersions. Further, we give Casorati inequalities for invariant and anti-invariant Riemannian maps (resp. submersions) whose target (resp. source) spaces are generalized complex and generalized Sasakian space forms. Toward information on geometric characteristics, we discuss the equality cases. We also exemplify the general forms.
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https://arxiv.org/abs/2510.12760
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71b77d6194057c59e72a2f13c4e6ade959b608c03d7df46f3419be5ea39a0018
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2026-01-23T00:00:00-05:00
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A Generalization of the Fox H-function
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arXiv:2510.15920v2 Announce Type: replace Abstract: In this paper we present a generalization of the Fox H-function called Fox-Barnes J-function. Like the Fox H-function, it is defined as a contour integral in the complex plane, but instead of an integrand given by a ratio of products of gamma functions involving several parameters, we use a ratio of products of double gamma functions. We study the conditions for its existence and how to choose a contour of integration based on the involved parameters. We discuss how the Fox H-function appears as a particular case and prove some properties of the Fox-Barnes J-function. As an application, we show how the Laplace transform of the Kilbas-Saigo function can be conveniently written in terms of the Fox-Barnes J-function, even in cases where the usual series representation is not convergent.
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https://arxiv.org/abs/2510.15920
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27160db9ec351b031f78bdffbe408caca694da72c29b602fa6d4d7f6f67719a0
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2026-01-23T00:00:00-05:00
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Through the Grapevine: Vineyard Distance as a Measure of Topological Dissimilarity
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arXiv:2510.24472v2 Announce Type: replace Abstract: We introduce a new measure of distance between datasets, based on vineyards from topological data analysis, which we call the vineyard distance. Vineyard distance measures the extent of topological change along an interpolation from one dataset to another, either along a pre-computed trajectory or via a straight-line homotopy. We demonstrate through theoretical results and experiments that vineyard distance is less sensitive than $L^p$ distance (which considers every single data value), but more sensitive than Wasserstein distance between persistence diagrams (which accounts only for shape and not location). This allows vineyard distance to reveal distinctions that the other two distance measures cannot. In our paper, we establish theoretical results for vineyard distance including as upper and lower bounds. We then demonstrate the usefulness of vineyard distance on real-world data through applications to geospatial data and to neural network training dynamics.
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https://arxiv.org/abs/2510.24472
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483bbc94332f4748ada3924a2812561c09b3110153b670fea09ae9750ff1fdf3
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2026-01-23T00:00:00-05:00
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Six-Functor Formalisms
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arXiv:2510.26269v2 Announce Type: replace Abstract: These are lecture notes for a course in Winter 2022/23, updated and completed in October 2025. The goal of the lectures is to present some recent developments around six-functor formalisms, in particular: the abstract theory of 6-functor formalisms; the 2-category of cohomological correspondences, and resulting simplifications in the proofs of Poincar\'e--Verdier duality results; the relation between 6-functor formalisms and ``geometric rings''; many examples of 6-functor formalisms, both old and new.
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https://arxiv.org/abs/2510.26269
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3b8abaecc1c520c1f742269eece159a37cea404961d6cd320d59e354fc17fda1
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2026-01-23T00:00:00-05:00
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On Singular Integrals and Quantitative Rectifiability in Parabolic Space and the Heisenberg Group
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arXiv:2510.26934v2 Announce Type: replace Abstract: David and Semmes proved that if all CZOs (of suitable dimension) are bounded with respect to an Ahlfors regular measure, then the measure is uniformly rectifiable. We extend this theorem to the parabolic space and the first Heisenberg group.
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https://arxiv.org/abs/2510.26934
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934e059a15881d7da0ead2853bb083e54f724d10c4c52371d4f55e86578e59d4
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2026-01-23T00:00:00-05:00
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Fundamental Lemma for Rank One Spherical Varieties of Classical Types
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arXiv:2511.05377v2 Announce Type: replace Abstract: According to the relative Langlands functoriality conjecture, an admissible morphism between the $L$-groups of spherical varieties should induce a functorial transfer of the corresponding local and global automorphic spectra. Via the relative trace formula approach, two basic problems are the local transfer and the fundamental lemma on the geometric side of the relative trace formulae. In this paper, we consider the rank one spherical variety case, where the admissible morphism between the $L$-groups is the identity morphism, in which case, Y. Sakellaridis has already established the local transfer. We formulate the statement of the fundamental lemma for the general rank one spherical variety case and prove the fundamental lemma for the rank one spherical varieties of classical types.
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https://arxiv.org/abs/2511.05377
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9e2c6955d48357c3f8b527a3f3ee4c01ff973514a473db0308aaf93aedb45082
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2026-01-23T00:00:00-05:00
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Poncelet Triangles and Tetragons over Finite Fields
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arXiv:2511.06347v3 Announce Type: replace Abstract: In the projective plane over a finite field of characteristic not equal to 2, we compute the probability that a randomly selected pair of distinct conics $(\mathscr{A},\mathscr{B})$, with $\mathscr{A}$ smooth or singular and $\mathscr{B}$ smooth, in a fixed pencil of conics will admit a triangle or a tetragon inscribed in $\mathscr{A}$ and circumscribed about $\mathscr{B}$. We do this for all pencils, classified up to projective automorphism, with at least one smooth conic; effectively allowing the case where our conic pairs intersect non-transversally.
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https://arxiv.org/abs/2511.06347
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277d9658d4afa8daa91458dbe4e2af424f88d34f4a00274b9b6e7a3da97d9e16
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2026-01-23T00:00:00-05:00
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Geometrically vertex decomposable open neighborhood ideals
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arXiv:2512.12886v2 Announce Type: replace Abstract: In this paper, we prove that the open neighborhood ideal of a TD-unmixed tree is geometrically vertex decomposable. This result implies that the associated Stanley-Reisner complex is vertex decomposable. We further demonstrate that Cohen-Macaulay open neighborhood ideals of trees are special cases of Cohen-Macaulay facet ideals of simplicial trees. Finally, we investigate open neighborhood ideals of chordal graphs and establish that almost all square-free monomial ideal can be realized as the open neighborhood ideal of a chordal graph.
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https://arxiv.org/abs/2512.12886
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e4016edeaa826c6da89225f4741396bf4fd7eb3cfdec5988afcdf6347b0c7ff9
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2026-01-23T00:00:00-05:00
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Erd\H{o}s-Wintner theorem for linear recurrent bases
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arXiv:2512.20882v2 Announce Type: replace Abstract: Let $(G_n)_{n\geqslant 0}$ be a linear recurrence sequence defining a numeration system and satisfying mild structural hypotheses. For real-valued G-additive functions (additive in the greedy G-digits), we establish an Erd\H{o}s-Wintner-type theorem: convergence of two canonical series (a first-moment series and a quadratic digit-energy series) is necessary and sufficient for the existence of a limiting distribution along initial segments of the integers. In that case, the limiting characteristic function admits an explicit infinite-product factorization whose local factors depend only on the underlying digit system. We also indicate conditional extensions of this two-series criterion to Ostrowski numeration systems with bounded partial quotients and to Parry $\beta$-expansions with Pisot-Vijayaraghavan base $\beta$.
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https://arxiv.org/abs/2512.20882
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2026-01-23T00:00:00-05:00
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Piecewise Smooth Dynamical Systems Regularized by Convolution
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arXiv:2601.00697v2 Announce Type: replace Abstract: We present a general regularization procedure for piecewise smooth vector fields whose discontinuity locus is a variety of normal crossings type. We show that such regularization can be smoothed through a finite sequence of blowings-up, thereby reducing the problem to study of the dynamics of a smooth vector field in a manifold with corners. The procedure will be illustrated in the cases of piecewise smooth vector fields on $\mathbb{R}^2$ with discontinuity locus $x=0$ or $xy=0$, and on $\mathbb{R}^3$ with discontinuity locus $xyz=0$. We will see that some unexpected dynamical phenomena may arise even in the case of piecewise constant vector fields.
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https://arxiv.org/abs/2601.00697
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2026-01-23T00:00:00-05:00
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Two algebraic proofs of the transcendence of $\mathrm{e}$ based on formal power series
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arXiv:2601.01019v5 Announce Type: replace Abstract: We remind the classical analytical proof of the transcendence of $\mathrm{e}$ due to Hilbert. Then, using formal power series, we give two algebraic semiformal proofs of this result. The first proof is a specialization of the proof of the Lindemann-Weierstrass theorem found by Beukers, B\'ezivin and Robba [2]. The second proof uses improper integrals of formal power series and is due to this author. We explain what ``semiformal'' means.
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https://arxiv.org/abs/2601.01019
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e1c4bcf4e9d0dfcd9c8502aa0000706c5bafb0a67afe65b22b871110b4e4be38
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Distributional Limits for Eigenvalues of Graphon Kernel Matrices
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arXiv:2601.04584v2 Announce Type: replace Abstract: We study the fluctuation behavior of individual eigenvalues of kernel matrices arising from dense graphon-based random graphs. Under minimal integrability and boundedness assumptions on the graphon, we establish distributional limits for simple, well-separated eigenvalues of the associated integral operator. A sharp probabilistic dichotomy emerges: in the non-degenerate regime, the properly normalized empirical eigenvalue satisfies a central limit theorem with an explicit variance, whereas in the degenerate regime the leading stochastic term vanishes and the centered eigenvalue converges to a weighted chi-square law determined by the operator spectrum. The analysis requires no smoothness or Lipschitz conditions on the kernel. Prior work under comparable assumptions established only operator convergence and eigenspace consistency; the present results characterize the full distributional behavior of individual eigenvalues, extending fluctuation theory beyond the reach of classical operator-level arguments. The proofs combine second-order perturbation expansions, concentration bounds for kernel matrices, and Hoeffding decompositions for symmetric statistics, revealing that at the $\sqrt{n}$ scale the dominant randomness arises from latent-position sampling rather than Bernoulli edge noise.
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https://arxiv.org/abs/2601.04584
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On the effects of protection zone and directed population flux in prey-predator dynamics
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arXiv:2601.05054v2 Announce Type: replace Abstract: We study a spatial predator-prey model in which prey can enter a protection zone (refuge) inaccessible to predators, while predators exhibit directed movement toward prey-rich regions. The directed movement is modeled by a far-sighted population flux motivated by classical movement rules, in contrast to the more commonly analyzed near-sighted chemotaxis-type mechanisms. We first establish local-in-time well-posedness for the corresponding nonstationary problem under Neumann boundary conditions, despite the discontinuity induced by the refuge interface. We then investigate the stationary problem, focusing on how the coexistence states emerge and organize globally in parameter space. In particular, we identify the bifurcation threshold for positive steady states from semitrivial predator-only equilibria, and describe the global continuation of the resulting branches. Our analysis reveals that strong directed movement can induce turning-point structures and multiplicity of coexistence steady states, highlighting a nontrivial interplay between spatial protection and predator movement behavior.
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https://arxiv.org/abs/2601.05054
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2026-01-23T00:00:00-05:00
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Foundations and Fundamental Properties of a Two-Parameter Memory-Weighted Velocity Operator
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arXiv:2601.05122v2 Announce Type: replace Abstract: We introduce and analyze a **memory-weighted velocity operator** \(\mathscr{V}_{\alpha,\beta}\) as a mathematical framework for describing rates of change in systems with time-varying, power-law memory. The operator employs two independent continuous exponents \(\alpha(t)\) and \(\beta(t)\) that separately weight past state increments and elapsed time scaling, motivated by physical systems where these memory aspects may evolve differently -- such as viscoelastic materials with stress-dependent relaxation or anomalous transport with history-dependent characteristics. We establish the operator's foundational properties: an explicit integral representation, linearity, and **continuous dependence** on the memory exponents with respect to uniform convergence. Central to the analysis are **weighted pointwise estimates** revealing how the exponent difference \(\beta(t)-\alpha(t)\) modulates \(\mathscr{V}_{\alpha,\beta}[x](t)\), leading to conditions under which \(\mathscr{V}_{\alpha,\beta}\) defines a bounded linear operator between standard function spaces. These estimates exhibit a natural compensation mechanism between the two memory weightings. For the uniform-memory case \(\alpha=\beta\equiv1\), we prove that \(\mathscr{V}_{\alpha,\beta}[x](t)\) **asymptotically recovers** the classical derivative \(\dot{x}(0)\) as \(t\to 0^{+}\), ensuring consistency with local calculus. The mathematical framework is supported by self-contained technical appendices. By decoupling the memory weighting of state increments from that of elapsed time, \(\mathscr{V}_{\alpha,\beta}\) provides a structured approach to modeling systems with independently evolving memory characteristics, offering potential utility in formulating evolution equations for complex physical processes with non-stationary memory.
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https://arxiv.org/abs/2601.05122
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4e7c12f22e48b0de00a408874f1f0c1e2261220d4b782a0846f20c23016b99ec
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2026-01-23T00:00:00-05:00
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Computational Evidence Against Quadratic-Cubic Factorization for the Second Cuboid Quintic
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arXiv:2601.07899v2 Announce Type: replace Abstract: Let $Q_{p,q}(t)\in\mathbb{Z}[t]$ be Sharipov's even monic degree-$10$ second cuboid polynomial depending on coprime integers $p\neq q>0$. Writing $Q_{p,q}(t)$ as a quintic in $t^{2}$ produces an associated monic quintic polynomial. After the weighted normalization $r=p/q$ and $s=r^{2}$ we obtain a one-parameter family $P_s(x)\in\mathbb{Q}[x]$ such that \[ Q_{p,q}(t)=q^{20}\,P_s\!\left(\frac{t^{2}}{q^{4}}\right)\qquad\text{with}\qquad s=\left(\frac{p}{q}\right)^{2}. \] Assuming a quadratic divisor $x^{2}+ax+b$ with $a,b\in\mathbb{Q}$, we reduce divisibility of $P_s(x)$ to the vanishing of an explicit remainder \[ R(x)=R_{1}(s,a,b)\,x+R_{0}(s,a,b). \] A key structural observation is that $R_1$ and $R_0$ are quadratic in $b$ and that, on the equation $R_1=0$, the second condition becomes linear in $b$. This yields a one-direction elimination to a plane obstruction curve $F(s,a)=0$ with $F\in\mathbb{Z}[s,a]$, without any lifting-back issues: when the linear coefficient is nonzero, the parameter $b$ is forced to be the rational value $b=C/L$. We isolate the degenerate locus $L=C=0$ and show it produces only $s=\pm 1$ (hence only $s=1$ in the cuboid domain $s>0$). Let $\overline{C}\subset\mathbb{P}^{2}$ be the projective closure of $F(s,a)=0$. Using Magma we perform a height-bounded search for rational points on $\overline{C}$. With bound $H=10^{9}$, the search returns $8$ rational points, whose affine part has $s\in\{-1,0,1\}$. In particular, no affine rational point with $s>0$ and $s\neq 1$ is found up to this bound. This provides strong computational evidence that for rational $s>0$, $s\neq 1$, the quintic $P_s(x)$ admits no quadratic factor over $\mathbb{Q}$ (equivalently, no $2+3$ (quadratic-cubic) factorization over $\mathbb{Q}$), and yields a conditional exclusion assuming completeness of the rational-point enumeration on $\overline{C}$.
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https://arxiv.org/abs/2601.07899
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e28fa24f85c8a11ae290cefc94c796a9ba6a343b4eda90c8fc44109e0c1bf668
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2026-01-23T00:00:00-05:00
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From carbon management strategies to implementation: Modeling and physical simulation of CO2 pipeline infrastructure -- a case study for Germany
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arXiv:2601.15090v2 Announce Type: replace Abstract: Carbon capture and storage or utilization (CCUS) will play an important role to achieve climate neutrality in many economies. Pipelines are widely regarded as the most efficient means of CO2 transport; however, they are currently non-existent. Policy-makers and companies need to develop large-scale infrastructure under substantial uncertainty. Methods and analyses are needed to support pipeline planning and strategy development. This paper presents an integrated method for designing CO2 pipeline networks by combining energy system scenarios with physical network simulation. Using Germany as a case study, we derive spatially highly resolved CO2 balances to develop a dense-phase CO2 pipeline topology that follows existing gas pipeline corridors. The analyzed system includes existing sites for cement and lime production, waste incineration, carbon users, four coastal CO2 hubs, and border crossing points. We then apply the multiphysical network simulator MYNTS to assess the technical feasibility of this network. We determine pipeline diameters, pump locations, and operating conditions that ensure stable dense-phase transport. The method explicitly accounts for elevation and possible impurities. The results indicate that a system of about 7000 km pipeline length and a mixed normed diameter of DN700 on main corridors and of DN500/DN400 on branches presents a feasible solution to connect most sites. Investment costs for the optimized pipeline system are calculated to be about 17 billion Euros. The method provides a reproducible framework and is transferable to other countries and to European scope.
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https://arxiv.org/abs/2601.15090
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Academic Papers
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6adb05b19609d7809226c7744d60d93235e51cd57f10fec02bf77f236dca90a3
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2026-01-23T00:00:00-05:00
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On the number of permutation-twisted dot products
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arXiv:2601.15276v2 Announce Type: replace Abstract: For distinct real numbers $a_1, \ldots, a_n$ and distinct real numbers $b_1, \ldots, b_n$, consider the sum $S=\sum_{i=1}^n a_i b_{\pi(i)}$ as $\pi$ ranges over the permutations of $[n]$. We show that this sum always assumes at least $\Omega(n^3)$ distinct values, which is optimal. This ``support'' bound complements recent work of Do, Nguyen, Phan, Tran, and Vu, and of Hunter, Pohoata, and Zhu on the anticoncentration properties of $S$ when $\pi$ is chosen uniformly at random.
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https://arxiv.org/abs/2601.15276
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6bc81a79f17c4b5784b077429e5bd040ab176d62ee767a3ecae1f68f285c39b4
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2026-01-23T00:00:00-05:00
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Utility maximization under endogenous pricing
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arXiv:2005.04312v5 Announce Type: replace-cross Abstract: We study the expected utility maximization problem of a large investor who is allowed to make transactions on tradable assets in an incomplete financial market with endogenous permanent market impacts. The asset prices are assumed to follow a nonlinear price curve quoted in the market as the utility indifference curve of a representative liquidity supplier. Using generalized subgradients, we show that optimality can be fully characterized via a system of coupled forward-backward stochastic differential equations (FBSDEs) which corresponds to a non-linear backward stochastic partial differential equation (BSPDE). We show existence of solutions to the optimal investment problem and the FBSDEs in the case where the driver function of the representative market maker grows at least quadratically or the utility function of the large investor falls faster than quadratically or is exponential. Furthermore, we derive smoothness results for the existence of solutions of BSPDEs. Examples are provided when the market is complete, the driver is positively homogeneous or the utility function is exponential.
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https://arxiv.org/abs/2005.04312
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66edfa7395a082d94cfc3c138ab90136dfd7be1fbba026b97c46558f4454cb50
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2026-01-23T00:00:00-05:00
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Black holes in the expanding Universe
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arXiv:2405.16673v3 Announce Type: replace-cross Abstract: The McVittie metric does not describe a physical black hole in an expanding Universe because the curvature scalar and pressure at its event horizon are infinite. We show that extending this metric to an inhomogeneous scale factor, which depends on both the time and radial coordinate, removes those infinities by imposing at the horizon the constancy of the Hubble parameter and a particular constraint on the gradient of the scale factor. We consider a special case of this metric, and show that the Hubble parameters at the event horizons of all centrally symmetric black holes are equal to the same constant $H_\textrm{hor}=(\Lambda/3)^{1/2}$. Because of this equality and the equivalence to the Kottler metric near the horizon, black holes do not grow with the Universe expansion.
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https://arxiv.org/abs/2405.16673
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ccd98ef7bf089e4d55aafe0095327295608fa4cf517d7a89994d0f2fa88afaa5
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2026-01-23T00:00:00-05:00
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New Insights into Population Dynamics from the Continuous McKendrick Model
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arXiv:2504.21103v3 Announce Type: replace-cross Abstract: This article presents a comprehensive study of the continuous McKendrick model, which serves as a foundational framework in population dynamics and epidemiology. The model is formulated through partial differential equations that describe the temporal evolution of the age distribution of a population using continuously defined birth and death rates. In this work, we provide rigorous derivations of the renewal equation, establish the appropriate boundary conditions, and perform a detailed analysis of the survival functions. The central result demonstrates that the population approaches extinction if and only if the net reproduction number $R_{n}$ is strictly less than unity. We present two independent proofs: one based on Laplace transform techniques and Tauberian theorems, and another employing a reformulation as a system of ordinary differential equations with eigenvalue analysis. Additionally, we establish the connection between the deterministic framework and stochastic process formulations, showing that the McKendrick equation emerges as the fluid limit of an individual-based stochastic model.
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https://arxiv.org/abs/2504.21103
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8743ccb0645fa36e4f2f12597d4b653aebda1d08ae8a63cf7708de0f25d1ae96
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2026-01-23T00:00:00-05:00
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Erasure cost of a quantum process: A thermodynamic meaning of the dynamical min-entropy
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arXiv:2506.05307v4 Announce Type: replace-cross Abstract: The erasure of information is fundamentally an irreversible logical operation, carrying profound consequences for the energetics of computation and information processing. We investigate the thermodynamic costs associated with erasing (and preparing) quantum processes. Specifically, we analyze an arbitrary bipartite unitary gate acting on logical and ancillary input-output systems, where the ancillary input is always initialized in the ground state. We focus on the adversarial erasure cost of the reduced dynamics -- that is, the minimal thermodynamic work cost to erase the logical output of the gate for any logical input, assuming full access to the ancilla but no access to any purifying reference of the logical input state. We determine that this adversarial erasure cost is directly proportional to the negative min-entropy of the reduced dynamics, thereby giving the dynamical min-entropy a clear operational meaning. The dynamical min-entropy can take positive and negative values, depending on the underlying quantum dynamics. The negative value of the erasure cost implies that the extraction of thermodynamic work is possible instead of its consumption during the process. A key foundation of this result is the quantum process decoupling theorem, which quantitatively relates the decoupling ability of a process with its min-entropy. This insight bridges thermodynamics, information theory, and the fundamental limits of quantum computation.
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https://arxiv.org/abs/2506.05307
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27bc431c1ea530c83f60ad37e56fed3551310dd4e524b498f8bb050453705d66
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2026-01-23T00:00:00-05:00
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Einstein Electron and Local Branching: Unitarity without Many Worlds --Local Hilbert spaces, boundaries, and quantum nonlocality
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arXiv:2507.16123v2 Announce Type: replace-cross Abstract: Traditional interpretations of quantum mechanics often present a dichotomy: either the wavefunction collapses upon measurement (Copenhagen), violating unitarity, or the entire universe branches into countless parallel worlds (Many-Worlds), with significant ontological proliferation. The Branched Hilbert Subspace Interpretation (BHSI) resolves this tension by introducing branching strictly within local Hilbert spaces. This framework reinterprets scenarios such as the Einstein 1927 electron-diffraction thought experiment, in which all quantum events are confined to a local Hilbert space, allowing the Born rule to emerge naturally from branch weights. Crucially, BHSI treats branching as a dynamical process tied to information recording. This leads to a testable proposal: a dual-layer experiment in which the particle transit time between layers is shorter than the sensor response time, enabling a direct probe of measurement timing and mismatched or uncommitted outcomes. We argue that a quantum system behaves as a unified whole, an island of coherence, within which unitary branching is confined to the system boundary, without observable correlations with distant, unentangled systems. Finally, we show that quantum nonlocality (e.g., in Bell tests or tunneling) arises naturally from the intrinsic vector-space structure of local Hilbert spaces, rather than from superluminal signaling.
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https://arxiv.org/abs/2507.16123
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7611edcf8f2e4b359b22c08778d3afbd0c3679b40ec6dfd62818950cd3e08e04
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2026-01-23T00:00:00-05:00
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Inference in pseudo-observation-based regression using (biased) covariance estimation and naive bootstrapping
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arXiv:2510.06815v2 Announce Type: replace-cross Abstract: The pseudo-observation method is regularly applied to time-to-event data. However, to date such analyses have relied on not formally verified statements or ad-hoc methods regarding covariance estimation. This paper strives to close this gap in the literature. To begin with, we demonstrate that the usual Huber-White estimator is not consistent for the limiting covariance of parameter estimates in pseudo-observation regression approaches. By confirming that a plug-in estimator can be used instead, we obtain asymptotically exact and consistent tests for general linear hypotheses in the parameters of the model. Additionally, we confirm that naive bootstrapping can not be used for covariance estimation in the pseudo-observation model either. However, it can be used for hypothesis testing by applying a suitable studentization. Simulations illustrate the good performance of our proposed methods in many scenarios. Finally, we obtain a general uniform law of large numbers for U- and V-statistics, as such statistics are central in the mathematical analysis of the inference procedures developed in this work.
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https://arxiv.org/abs/2510.06815
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a59b18fe6c63fe071db33987813a25b5b02b85578872004a9b1628cdeac0b447
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2026-01-23T00:00:00-05:00
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Thermodynamics of quantum processes: An operational framework for free energy and reversible athermality
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arXiv:2510.12790v3 Announce Type: replace-cross Abstract: We explore the thermodynamics of quantum processes (quantum channels) by axiomatically introducing the free energy for channels, defined via the quantum relative entropy with an absolutely thermal channel whose fixed output is in equilibrium with a thermal reservoir. This definition finds strong support through its operational interpretations in designated quantum information and thermodynamic tasks. We construct a resource theory of athermality for quantum processes, where free operations are Gibbs preserving superchannels and golden units are unitary channels with respect to absolutely thermal channel having fully degenerate output Hamiltonian. We exactly characterize the one-shot distillation and formation of quantum channels using hypothesis-testing and max-relative entropy with respect to the absolutely thermal channel. These rates converge asymptotically to the channel free energy (up to a multiplicative factor of half the inverse temperature), establishing its operational meaning and proving the asymptotic reversibility of the athermality. We show the direct relation between the resource theory of athermality and quantum information tasks such as private randomness and purity distillation, and thermodynamic tasks of erasure and work extraction. Our work connects the core thermodynamic concepts of free energy, energy, entropy, and maximal extractable work of quantum processes to their information processing capabilities.
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https://arxiv.org/abs/2510.12790
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83865cc3ed82ea72a87eccd4dfa49d2e24416605b2c0c11417020f325afd0579
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2026-01-23T00:00:00-05:00
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An $\Omega(\log(N)/N)$ Lookahead is Sufficient to Bound Costs in the Overloaded Loss Network
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arXiv:2601.14538v2 Announce Type: replace-cross Abstract: I study the simplest model of revenue management with reusable resources: admission control of two customer classes into a loss queue. This model's long-run average collected reward has two natural upper bounds: the deterministic relaxation and the full-information offline problem. With these bounds, we can decompose the costs faced by the online decision maker into (i) the \emph{cost of variability}, given by the difference between the deterministic value and the offline value, and (ii) the \emph{cost of uncertainty}, given by the difference between the offline value and the online value. \cite{Xie2025} established that the sum of these two costs is $\Theta(\log N)$, as the number of servers, $N$, goes to infinity. I show that we can entirely attribute this $\Theta(\log N)$ rate to the cost of uncertainty, as the cost of variability remains $O(1)$ as $N \rightarrow \infty$. In other words, I show that anticipating future fluctuations is sufficient to bound operating costs -- smoothing out these fluctuations is unnecessary. In fact, I show that an $\Omega(\log(N)/N)$ lookahead window is sufficient to bound operating costs.
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https://arxiv.org/abs/2601.14538
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57df3c1e7e0125b60ff3fc233576b71276441a4e3bee66c91a7ca3b513f632a6
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2026-01-23T00:00:00-05:00
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LISA and the LISA Science Team
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arXiv:2601.15365v1 Announce Type: new Abstract: LISA, the Laser Interferometer Space Antenna, due to launch mid-2035, is a large class space mission by the European Space Agency (ESA). In partnership with NASA and ESA-member states, ESA is on track to launch what is expected to be the first space-based gravitational wave detector. By hosting detectors in space, one gains access to a lower frequency band of gravitational wave sources and with them, a plethora of new science. To maximise this scientific gain, ESA and NASA selected 20 scientists for the LISA Science Team, to carry out and/or lead necessary actions on the run up to LISA launch. We give a short overview and update of the LISA mission, some of its science objectives and related waveforms, as well as the work of the LISA Science Team as of December 2025.
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https://arxiv.org/abs/2601.15365
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84c1c533f4d2d279dcd64bb1ebc6914c167b8cb0527694c8ec02216a4bb173a6
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2026-01-23T00:00:00-05:00
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Non-uniform Antenna Loading Effect on Embedded Element Patterns and Application to Fault Detection
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arXiv:2601.15367v1 Announce Type: new Abstract: A new, iterative algorithm is presented to calculate the Embedded Element Pattern (EEP) tranformation from a set of patterns computed for a uniform antenna port loading (scaled identinty matrix) to a set of those computed for a non-uniform one (arbitrary diagonal matrix). This method proves particularly useful when inverting the computations to derive the non-uniform entries of the arbitrary load, given the minimum number of EEPs necessary, which disposes of the redundancy of other matrix-based computations and leads to numerically stable impedance fault calculation. As the EEPs are envisioned to be obtained primarily through measurement, our method is also tested with the inclusion of various noise components and its convergence is evaluated, suggesting the minimum SNR and fading level of the measurement apparatus, as well as the optimal choice of reference antenna to minimise the estimation error.
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https://arxiv.org/abs/2601.15367
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6035c6632f4fee276e5f9750ce8a9fedacda12db9e4b6973ef6d69251718f8a3
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2026-01-23T00:00:00-05:00
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Digging into the Interior of Hot Cores with ALMA (DIHCA). VII. Disk candidates around high-mass stars and evidence of anisotropic infall
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arXiv:2601.15371v1 Announce Type: new Abstract: We study the kinematics of condensations in 30 fields forming high-mass stars with ALMA at a high-resolution of ~0.08'' on average (~230 au). The presence of disks is important for feeding high-mass stars without feedback halting growth as their masses increase. In the search for velocity gradients resembling rotation that can reveal the presence of disks, we analyze the emission of gas tracers in 49 objects using CH$_3$OH, CH$_3$CN, and tentative detections of HNCO and cis-HCOOH. Most of the velocity distributions show velocity gradients indicative of rotation. We reveal a total of 32 disk candidates, the largest sample to date that has been uniformly analyzed at a few hundred au scales in the high-mass regime. Their position-velocity maps are generally asymmetric with one side brighter than the opposite. We successfully fit a power law to the position-velocity maps of the disk candidates and find indices between -0.5 (Keplerian rotation) and -1 (rotation under specific angular momentum conservation) with a median of -0.7. Under Keplerian rotation assumption, we estimate central masses, uncorrected for inclination, ranging between 7 to 45 M$_\odot$. Excluding outliers, the disk candidates are relatively more compact (<200 au) and less massive (<5 M$_\odot$) than previous results at coarser angular resolution. We calculate an average Toomre-$Q$ parameter and find that most are gravitationally unstable (median of 0.5). We conclude that these observations offer the first opportunity to separate the disk and envelope components of hot cores on a statistically significant sample, and confirm that anisotropic collapse plays an role in feeding high-mass (proto)stars.
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https://arxiv.org/abs/2601.15371
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18c5f49d7a0f138802db04e0edae452837917d1614c1d1f8633bcb74ab65438e
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2026-01-23T00:00:00-05:00
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Hierarchical bayesian inference: constraining population distribution of dark matter halo shapes via stellar streams
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arXiv:2601.15373v1 Announce Type: new Abstract: Stellar streams, the debris of tidally disrupted satellites, trace their host's gravitational potential and thus probe dark matter halo structure. While six-dimensional phase-space data of Galactic streams enable precise dark matter halo modelling in the Milky Way, streams around external galaxies are typically available only as low surface brightness features without kinematics (i.e. two-dimensional photometric data), providing only weak constraints when considered individually. We present a hierarchical Bayesian framework that infers the population distribution of halo flattening using only projected stream tracks. Streams are forward-modelled in StreaMAX, a new JAX-accelerated particle-spray package that achieves orders of magnitude faster stream generation when compared to traditional methods. For each stream we fit an axisymmetric dark matter halo model and obtain a posterior on the flattening. These posteriors are then combined through hierarchical reweighting to constrain the population distribution. Using mock data, we show that individual fits recover the correct flattening with modest precision and exhibit projection-induced multi-modalities. Nevertheless, aggregating these fits yields accurate and confident constraints on the underlying population distribution of dark matter halo morphologies, clearly distinguishing between oblate, spherical, and prolate populations. The total computational cost scales linearly with sample size. Our results demonstrate that ensembles of purely photometric streams carry sufficient information to constrain dark matter halo shapes in external galaxies at the population level. With the forthcoming samples from Euclid and Rubin/LSST, this approach offers a practical path to population-level inferences of halo morphology without any kinematic measurements.
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https://arxiv.org/abs/2601.15373
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cc0ec0b1800f33f93d69c6084cb31623741badc54662ed421e48cb7969d291be
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2026-01-23T00:00:00-05:00
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What factors shape the radio luminosity of star-forming galaxies? A new calibration from LoTSS-DR2
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arXiv:2601.15374v1 Announce Type: new Abstract: Radio observations offer a dust-unobscured view of galaxy star formation via the radio continuum-star formation rate (RC--SFR) relation. Emerging evidence of a stellar mass dependence in the RC--SFR relation raises the broader question of how other galaxy properties may influence this relation. In this work, we study the dependence of the global RC--SFR relation on galaxy properties in local ($z\,\leq$\,0.3) star-forming galaxies (SFGs) using the second data release of the LOFAR Two-Metre Sky Survey (LoTSS-DR2). Employing a non-parametric decision-tree regression algorithm, we identify the most important galaxy properties for estimating the radio luminosity using a sample of 18,828 emission-line-classified SFGs based on spectroscopic data from the SDSS-DR8. Along with the spectroscopically obtained SFRs and stellar mass values, we also use SFRs and stellar masses derived using photometric SED-fitting from the \textit{GALEX}--SDSS--\textit{WISE} Legacy Catalogue (GSWLC) for the same sample. We find that a galaxy's SFR is most important for predicting the radio luminosity, followed by the stellar mass, at $>5\sigma$ significance. Complementing the LoTSS catalogue 150\,MHz flux densities with aperture photometry for the rest of the emission-line classified sample (35,099 galaxies in total), we obtain a new calibration of the RC--SFR relation, which does not change significantly whether we use spectroscopic or photometrically derived SFRs and stellar masses, despite the fact that the methods probe star formation on different characteristic timescales. Our results highlight the utility of decision-tree algorithms for handling censored radio-selected galaxy samples, which will be useful for future spectroscopic surveys of radio sources.
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https://arxiv.org/abs/2601.15374
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658fad2e17d3efee21771e0d45b8037a6edce9879814f38cf4ae4dfba9564ad2
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2026-01-23T00:00:00-05:00
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The Back-in-time Void Finder: dynamical identification of cosmic voids through optimal transport reconstruction
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arXiv:2601.15378v1 Announce Type: new Abstract: Cosmic voids have increasingly emerged as a powerful cosmological probe. However, their large spatial extent and intrinsically underdense environments make their identification highly sensitive to shot noise, redshift-space distortions (RSD), and observational systematics, particularly for topological and density-based void definitions. We introduce the Back-In-Time Void Finder (BitVF), a novel dynamical and physically motivated algorithm that identifies cosmic voids as regions of negative divergence of the Lagrangian displacement field reconstructed from the present-day tracer distribution. The reconstruction relies on an optimized discrete optimal transport algorithm that recovers the backward-in-time dynamics of tracers, naturally accounting for tracer bias without relying on cosmological assumptions. We validate BitVF against the widely used topological void finder REVOLVER using high-resolution N-body simulations, showing that it produces void catalogs with smoother and more physically motivated density profiles, as well as abundances that are more stable under tracer subsampling and shot noise. We further apply it to realistic DESI-like mock light-cone galaxy catalogs, demonstrating that it intrinsically mitigates redshift-space systematic effects, preserving real-space void size functions more faithfully than topological methods. Modeling RSD, the reconstruction can be combined with a fiducial cosmology and an assumed tracer bias within a bias-corrected Kaiser framework, yielding reconstructed-space void catalogs consistent with real-space statistics across redshift. Its performance is characterized as a function of the main internal parameters, showing an optimal balance between accuracy, computational efficiency, and applicability to stage IV galaxy surveys. BitVF will be publicly released within the CosmoBolognaLib.
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https://arxiv.org/abs/2601.15378
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b12634bfb0107be5df41543617b65ec9d761dd23db53b400524723c04ecfe049
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2026-01-23T00:00:00-05:00
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Optimizing Optical Searches for Supermassive Black Hole Binaries in AGN Light Curves: Fourier versus Bayesian Periodicity Detection
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arXiv:2601.15379v1 Announce Type: new Abstract: Simulations predict that supermassive black hole binaries (SMBHBs) will exhibit periodic brightness variations that may exceed the stochastic variability intrinsic to active galactic nuclei (AGN). In this paper, we simulate SMBHBs with damped random walk (DRW) AGN variability and an added sinusoidal signal from the orbital motion, and test three methods -- the Generalized Lomb Scargle Periodogram (GLSP), the nested Bayesian sampler (NBS), and the Weighted Wavelet Z-Transform (WWZ) -- to determine which is best at recovering the periodicity. Our simulated light curves follow the properties of the Catalina Real-Time Transient Survey (CRTS), Legacy Survey of Space and Time (LSST), and Zwicky Transient Facility (ZTF) to best inform current and future SMBHB searches. We map a broad range of parameter space and identify which DRW-only light curves best mimic periodicity and pass each method's model selection. The NBS performs best at detecting periodicity and filtering out DRW-only light curves. Combined candidate selection with both the NBS and GLSP significantly reduces false positive rates with marginal impact to true positive rates. With this joint model selection pipeline, we find the lowest false positive rates in ZTF-like simulations and the highest detection rates in LSST-like simulations. Using a modified computation of the False Alarm Probability (FAP) with GLSP, we efficiently triage LSST AGN light curves (~10^7 light curves in ~10-30 hours) and achieve true- and false- positive rates of ~40% and ~0.5%, respectively.
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https://arxiv.org/abs/2601.15379
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6f8c0f850827f50d638d08998ea1ab7ec2ee684cab9277ab280323d3123070cf
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2026-01-23T00:00:00-05:00
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Blazars define a stable celestial reference frame
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arXiv:2601.15381v1 Announce Type: new Abstract: Recent work has shown that optical-radio position offsets and radio position variability are inversely correlated with the photometric variability of active galactic nuclei (AGN). A key prediction of these findings is that a reference frame constructed using highly photometrically variable AGN should be more stable than a frame that does not account for variability and that variability can be used to optimally weight all sources in order to maximize frame stability. Using ICRF3 matched to Gaia DR3, we employed a bootstrap method to estimate the multi-epoch stability of frames constructed using AGN selected at varying levels of photometric variability. We fit vector spherical harmonics to the coordinate differences between the three ICRF3 frames (S/X, K, and X/Ka) and Gaia and quantified the statistical dispersion as a function of blazar-like (high variability), quasar-like (low variability), and intermediate-variability class. An S/X reference frame constructed using blazars exceeds the stability of a frame constructed with quasars by a factor of 6 and is twice as stable as the ICRF3 defining sources. At K and X/Ka, a blazar-based frame matches or exceeds the stability of the defining sources by a factor of 1.4 in the case of X/Ka and exceeds the stability of a frame based on quasars by over a factor of 2 in both cases. The smaller improvement at K and X/Ka is likely because sources selected at higher frequency are more likely to be blazars. We derived a variability-based astrometric covariance scaling method that results in factor of 2 reduction in frame distortions and instabilities between S/X and Gaia, with a mild improvement for K but no difference for X/Ka, which is dominated by known distortions. Our results confirm the prediction that an optimal weighting of the link between the optical and radio celestial reference frames is enabled by accounting for photometric variability.
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https://arxiv.org/abs/2601.15381
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4f5a1d4f92af8b0ac9da69102b715c5fb43c968510fa0050e4040aef150284ea
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2026-01-23T00:00:00-05:00
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A Stratification in Magnetic Field Structures: The Radio Outflow in NGC 4151
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arXiv:2601.15382v1 Announce Type: new Abstract: The nature of radio outflows in radio-quiet AGN remains poorly understood. In this study, we present kpc-scale polarization observations of the Seyfert galaxy NGC\,4151 using the Karl G. Jansky Very Large Array (VLA) in B-array at 3 and 10 GHz. We find that the inferred magnetic (B-) field structures show a stratification: a `spine-sheath'-like structure, with fields perpendicular to the jet direction in the `spine' and parallel in the `sheath', is observed in the higher resolution (0.5 arcsec) image at 10 GHz. In addition, a `wind'-like component with B-fields perpendicular to the radio outflow is observed in the 3 GHz image (resolution 2 arcsec); this feature is prominent along the `receding' (eastern) jet direction. Rotation measure (RM) ranges from $-230$ to 250 rad m$^{-2}$ over the polarized regions, indicating a low-electron-density ($10^{-2}-10^{-3}$ cm$^{-3}$) tenuous medium surrounding the source causing Faraday rotation. A {tentative} RM gradient of $+75$ to $-25$ rad m$^{-2}$ is observed transverse to the northern `wind' component, while a similar gradient with opposite sign is seen across the southern `wind' component, suggestive of a helical magnetic field threading the outflow. Based on an analysis of the available radio and X-ray data, we conclude that the stratified radio outflow in NGC 4151 is magnetically-driven. The bi-conical radio `wind' is found to be massive ($1050-3200 M_\odot$) with a high mass outflow rate ($0.01-0.03$ M$_\odot$ yr$^{-1}$) but low in kinetic power ($<0.01$% of L$_{\rm{bol}}$), making it less impactful for galactic-scale feedback. Our study suggests that radio-quiet AGN may also host magnetically dominant jets and winds, even while their jets are smaller and weaker compared to radio-loud AGN.
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https://arxiv.org/abs/2601.15382
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0e105f3be67996a370e8ee9f58ed1506db73f672a995c41d8d839cc0cfe23a3f
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2026-01-23T00:00:00-05:00
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An Investigation of 5-year Simultaneous X-ray and Radio Light Curves of the Dwarf Seyfert Galaxy UGC 6728
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arXiv:2601.15383v1 Announce Type: new Abstract: We present serendipitous simultaneous radio and X-ray light curves of the dwarf Seyfert galaxy UGC 6728 spanning 5 years. The X-ray light curve exhibits a flaring period, followed by a gradual rise and decline. Throughout these events, the X-ray hardness ratio and spectrum do not change significantly. The radio flux is constant, as far as can be determined from its sparse sampling, until the end of the X-ray flare, then decreases by a factor of two by the midpoint of the gradual X-ray rise before returning to baseline at the end of the X-ray decline. We interpret this behavior in light of a similar event recently reported in NGC 2992, in which there is a temporary obscuration of the radio source by a blob of plasma ejected by a magnetic reconnection in the accretion disk. The energetics of the X-ray flare are consistent with those expected from magnetic disk activity. As in NGC 2992, the X-ray spectrum does not evolve during the obscuration event. We also discuss the possibility that the observed phenomena are due to normal AGN coronal flaring and variability, which is plausible but unlikely given the lack of spectral variation.
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https://arxiv.org/abs/2601.15383
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7cb4091a450fc4163146d688e750e593a0381b83eba959c7fad6ec61e651094d
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2026-01-23T00:00:00-05:00
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An Analysis of AGN Feedback in the Compact Galaxy Group Stephan's Quintet
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arXiv:2601.15384v1 Announce Type: new Abstract: Compact galaxy groups are ideal laboratories for studying the effects of interactions between AGN and multiple nearby galaxies. Recent JWST observations of the nearby compact group Stephan's Quintet highlight tidal flows between the interacting galaxies as well as outflows from the active galaxy NGC 7319. To study the kinematics on a large scale throughout the group, we obtained spatially-resolved long-slit spectra of Stephan's Quintet at multiple slit positions with Apache Point Observatory's Kitt Peak Ohio State Multi-Object Spectrograph. We fit multiple Gaussians to the H$\alpha$ $\lambda$6563 \r{A} and [N II] $\lambda\lambda$6548, 6583 \r{A} emission lines to isolate the different kinematic components. We used the kinematics to develop the first biconical outflow model of the narrow-line region of NGC 7319. Using a combination of galactic rotation models, biconical outflow models, and kinematic maps of the ionized gas, we disentangled the outflows, rotation, and tidal flows in the group. We found outflow radial velocities up to 550 km s$^{-1}$ peaking at 2.6 kpc from the central supermassive black hole, and a transition from AGN-powered outflows to gravitationally-powered tidal flows at a projected distance between 2.4 -- 6.3 kpc. We performed a line ratio analysis and determined the gas shows Seyfert-like ionization out to 6.3 kpc (projected), which supports our finding that gas outside this radius is predominantly powered by tidal flows. Our separation of kinematic components in Stephan's Quintet will enable future studies of the physical conditions and dynamical forces in the ionized gas to better quantify the feeding and feedback processes of AGN in compact groups.
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https://arxiv.org/abs/2601.15384
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a6221a15f165439f41de6766535ef602140fc230f93440c2d71d1388f76d9b81
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2026-01-23T00:00:00-05:00
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Solar twins in Gaia DR3 GSP-Spec I. Building a large catalog of Solar twins with ages
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arXiv:2601.15387v1 Announce Type: new Abstract: [Abbreviated] Context. Solar twins, stars whose stellar parameters (Teff, log g, and [M/H]) are very close to the Solar ones, offer a unique opportunity to investigate Galactic archaeology with very high accuracy and precision. However, most previous catalogs of Solar twins contain only a small number of objects (typically a few tens), and their selection functions are poorly characterized. Aims. We aim at building a large catalog of Solar twins from Gaia DR3 GSP-Spec, providing model-driven, rather than data-driven, stellar parameters including ages, together with a well-characterized selection function. Methods. Using stellar parameters from the Gaia DR3 GSP-Spec catalog, we selected Solar-twin candidates whose parameters lie within +- 200 K in Teff, +- 0.2 in log g, and +- 0.1 dex in [M/H] of the Solar values. Candidates unlikely to be genuine Solar twins were removed using Gaia flags and photometric constraints. We determined accurate ages for individual twins with a Bayesian isochrone-projection method, considering three combinations of parameters: Teff, [M/H], and either log g, M_G, or M_Ks. We also constructed a mock catalog to characterize the selection function. Results. Our final GSP-Spec Solar-twin catalog contains 6,594 stars. The mock catalog consisting of 75,588 artificial twins well reproduces the main characteristics of the observed catalog, especially for ages determined with M_G or M_Ks. To demonstrate the usefulness of our catalog, we compared chemical abundances [X/Fe] with age. We statistically confirmed the age--[X/Fe] relations for several species (e.g., Al, Si, Ca, and Y), demonstrating that trends previously identified in small but very high-precision samples persist in a much larger, independent sample. Conclusions. Our study bridges small high-precision Solar-twin samples and large data-driven ones, enabling demographic studies of Solar twins.
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https://arxiv.org/abs/2601.15387
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d03256b80bf91915810bc63b018c3b0ac9e74b4ebddd8be93b7f76122624c853
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2026-01-23T00:00:00-05:00
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Dynamic shocks powered by a wide, relativistic, super-Eddington outflow launched by an accreting neutron star in the mid-20th century
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arXiv:2601.15400v1 Announce Type: new Abstract: Accreting systems can launch powerful outflows which interact with the surrounding medium. We combine new radio observations of the accreting neutron star X-ray binary (XRB) Circinus X-1 (Cir X-1) with archival radio observations going back 24 years. The $\sim3$ pc scale wide-angle radio and X-ray emitting caps found around Cir X-1 are identified as synchrotron emitting shocks with significant proper motion and morphological evolution on decade timescales. Proper motion measurements of the shocks reveal they are mildly relativistic and decelerating, with apparent velocity of $0.14c\pm0.03c$ at a propagation distance of 2 pc. We demonstrate that these shocks are likely powered by a hidden relativistic ($\gtrsim0.3c$) wide-angle conical outflow launched in $1972\pm3$, in stark contrast to known structures around other XRBs formed by collimated jets over 1000s of years. The minimum time-averaged power of the outflow required to produce the observed synchrotron emission is $\sim0.1L_\text{Edd}$, while the time-averaged power required for the kinetic energy of the shocks is $\sim40 \left(\frac{n}{10^{-2} \text{cm}^{-3}}\right)L_\text{Edd}$, where $n$ is the average ambient medium number density. This reveals the outflow powering the shocks is likely significantly super-Eddington. We measure significant linear polarisation up to $52\pm6\%$ in the shocks demonstrating the presence of an ordered magnetic field of strength $\sim200~\mu\text{G}$. We show that the shocks are potential PeVatrons, capable of accelerating electrons to $\sim0.7~\text{PeV}$ and protons to $\sim20~\text{PeV}$, and we estimate the injection and energetic efficiencies of electron acceleration in the shocks. Finally, we predict that next generation gamma-ray facilities may be able to detect hadronic signatures from the shocks.
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https://arxiv.org/abs/2601.15400
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e841de849bc1e39f76852f5125e5c79e84da88e7687572edda60fda8ce52cf5e
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2026-01-23T00:00:00-05:00
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The age sequence of young clusters in Perseus: Estimating ages from mass distributions
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arXiv:2601.15413v1 Announce Type: new Abstract: Establishing ages for young clusters is key for properly tracking the star formation history of a region. In this paper we investigate a new approach to estimating ages for young populations, based on the well-founded assumption that the initial mass function is the same throughout a star forming cloud. We trial this method for six young clusters in the Perseus star forming region. For all six clusters, we construct new member samples in a homogeneous way using Gaia DR3. We estimate masses by comparing 2MASS photometry to theoretical isochrones, including Monte Carlo simulations to propagate the errors. We compare the mass distributions of the clusters for a range of plausible ages, looking for a combination of ages that results in indistinguishable mass distributions across the region. We find the best fit for ages of 1 Myr for NGC1333+Autochthe, 2 Myr for IC348, 2-3 Myr for Heleus, 3-4 Myr for Mestor, 4-5 Myr for Electryon+Cynurus, and 5-8 Myr for Alcaeus. All other combinations of ages are ruled out by this criterion. The established age sequence is consistent with the relative ages inferred from disc fractions, and broadly aligns with the age sequence determined in previous studies using isochrone fitting. We suggest that this approach can be a useful complement and cross-check to established methods to estimate ages in young populations.
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https://arxiv.org/abs/2601.15413
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62ab285a010ff3808c373e31a2f89a355ab05eb60871478ef9473d7fed54d0bd
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2026-01-23T00:00:00-05:00
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Spin-down changes in PSR B0540-69 induced by a drift of the magnetic axis
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arXiv:2601.15425v1 Announce Type: new Abstract: The dynamics of the solid crust + magnetic field lines of pulsars is a much debated issue, and remains unsettled after 50 years. Some pieces of evidence have emerged to complete and confirm theoretical calculations and expectations. We discuss in the present work an interpretation of the behavior of the ''Crab Twin'' pulsar PSR B0540-69 in terms of the evolution of the magnetic field/quakes, connecting the behavior of the braking index with the underlying platelet drift and sudden discontinuous rearrangement (fast-slip) and long-term ones (slow-slip events), suggested by analogy with existing theoretical picture observed in the Earth's crust. The relationship of this scenario with permanent torque-changing glitches seen in the Crab and other young pulsars, and a set of similar events in the same object and others is addressed. We conclude that this physical approach is in principle consistent with all these sudden events, and point out future work to clarify the whole picture.
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https://arxiv.org/abs/2601.15425
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ecd39d031fe274c3f6a5129522d012d2500dae76511d1b4d043644ed24e5d340
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2026-01-23T00:00:00-05:00
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Supernova interactions with aspherical circumstellar material I: calculations of light curves, AB magnitudes, spectra, and polarisation
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arXiv:2601.15428v1 Announce Type: new Abstract: We present an upgraded detailed numerical calculations of supernova (SN) interactions with significantly aspherical circumstellar matter (CSM), primarily formed as a disc or bipolar lobes. The circumstellar disc can arise as a result of, for example, mass transfer in a binary, while bipolar lobes can be the result of a violent pre-explosive ejection of matter, similar to the iconic cases of luminous blue variable stars (LBVs). We numerically simulate the radiation-hydrodynamic (RHD) behaviour of interaction processes using a 2D cylindrical version of the RHD code CASTRO. We then calculate light curves, spectral patterns, and polarisation profiles, all up to a relatively long time of two years after an SN shock breakout and from different directions, using the multidimensional Monte Carlo radiation transfer (MC-RT) codes SEDONA and SIROCCO. We calculated a total of five models for the two aforementioned configurations of the surrounding CSM, for stratified density levels, comparing the simulated hydrodynamic behaviour and differences in their observable properties. RHD models exhibit similar behaviour to previous adiabatic models, but with a significantly slower expansion velocity. The calculated light curves show a relatively smooth evolution in SN-disc interaction, and declines and brightening in SN-lobes interaction. Comparing models with real events with a presumed similar physical process provides guidance for selecting a more accurate CSM configuration when simulating real situations.
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https://arxiv.org/abs/2601.15428
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f1089ed079d7b613d5936eee2c982e0ecf90b0fdad53c77ca0aa04fb6289f261
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2026-01-23T00:00:00-05:00
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The role of gas stripping in the quenching of satellite galaxies using SHARK v2.0
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arXiv:2601.15435v1 Announce Type: new Abstract: Observational studies have made substantial progress in characterizing quenching as a function of stellar mass and environment, but they are often limited in their ability to constrain quenching timescales and to determine the dominant environmental process responsible for the shutting down of star formation. To address this, we combine recent Sloan Digital Sky Survey (SDSS) observations with the SHARK v2.0 semi-analytic model to study the quenching of satellite galaxies in groups and clusters. We generate mock SDSS-like observations to calibrate the hot halo and cold interstellar medium (ISM) gas stripping prescriptions against observed satellite quenched fractions, finding that the previously adopted stripping prescriptions in SHARK v2.0 are too aggressive and overestimate the quenched fraction of satellite galaxies. Reducing the efficiency of both hot and cold gas stripping yields excellent agreement with observations for low- and intermediate-mass satellite galaxies. We use the calibrated model to investigate quenching timescales and find that satellites quench more quickly in clusters compared to groups, with timescales that generally decrease with increasing stellar mass. The long (>2 Gyr) timescales we measure favour hot halo gas removal as the dominant driver of satellite quenching.
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https://arxiv.org/abs/2601.15435
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ae32f82842ab1541715d03181636c490fb5843928619f3bd6a25dd67f09fe3f2
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2026-01-23T00:00:00-05:00
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Perihelion Asymmetry in the Water Production Rate of the Interstellar Object 3I/ATLAS
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arXiv:2601.15443v1 Announce Type: new Abstract: 3I/ATLAS is an interstellar object whose activity provides critical insights into its composition and origin. However, due to its orbital geometry, the object is too close to the Sun near perihelion to be observed from the ground, and space-based measurements are therefore required. Here we characterize the water production rate of 3I/ATLAS using SOHO/SWAN Lyman-$\alpha$ observations from 2025 November to December (heliocentric distances 1.4 to 2.2 au) with 3D Monte Carlo modeling. We report a peak post-perihelion water production rate of $Q_{\mathrm{H_2O}} \approx 4 \times 10^{28}$ mol s$^{-1}$, corresponding to a minimum active fraction of $\sim$30\% (assuming a maximum nucleus radius of 2.8 km). Comparison of our post-perihelion measurements with published pre-perihelion results reveals a heliocentric asymmetry, with an $r_h^{-5.9 \pm 0.8}$ scaling for the inbound rise, followed by a shallower $r_h^{-3.3 \pm 0.3}$ scaling during the outbound decline, where $r_h$ is heliocentric distance. The post-perihelion behavior indicates that the water production of 3I/ATLAS was driven primarily by the varying solar insolation acting on a stable active area. Combined with other evidence, including comparison with the hyperactive comet 103P/Hartley 2, our findings suggest that its water production is likely dominated by a distributed source of icy grains. Furthermore, it displayed remarkable stability in the activity with no signs of outbursts or rapid depletion of water production.
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https://arxiv.org/abs/2601.15443
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8bd958170b51bcf3e6b23a841756bd35aee749ee19b6e6bf74ea1f49b899bb27
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2026-01-23T00:00:00-05:00
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The long quest for vacuum birefringence in magnetars: 1E 1547.0-5408 and the elusive smoking gun
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arXiv:2601.15452v1 Announce Type: new Abstract: Magnetars are now known to be among the most strongly polarized celestial sources in X-rays. Here we report on the $500\,\mathrm{ks}$ observation of the magnetar 1E 1547.0-5408 performed by the Imaging X-ray Polarimetry Explorer (IXPE) in March 2025. The IXPE spectrum is well reproduced by a single thermal component with blackbody temperature $kT_\mathrm{BB}\sim 0.67\,\mathrm{keV}$ and emission radius $R_\mathrm{BB}\sim 1.2\,\mathrm{km}$. The source exhibits a high linear polarization degree in the $2$--$6\,\mathrm{keV}$ band ($\mathrm{PD}=47.7\pm2.9\%$) with polarization angle $\mathrm{PA}=75^\circ.8 \pm 1.^\circ8$, measured West of celestial North. While $\mathrm{PA}$ does not appear to vary with energy, there is some evidence (at the $1\sigma$ confidence level) of a minimum in $\mathrm{PD}$ between $3$ and $4\,\mathrm{keV}$, compatible with what is expected by partial mode conversion at the vacuum resonance in a magnetized atmosphere. Phase-resolved spectral and polarimetric analyses reveal that X-ray thermal radiation likely originates from a single, fairly small hot spot with a non-uniform temperature distribution. Fitting the phase-dependent $\mathrm{PA}$ measured by IXPE with a rotating vector model (RVM) constrains the source geometry and indicates that both the dipole axis and line-of-sight are misaligned with respect to the spin axis. Under these conditions, the high polarization of the source cannot be regarded as compelling evidence for the presence of vacuum birefringence in the star magnetosphere. Nevertheless, the fact that the RVM successfully reproduces the modulation of the X-ray polarization angle and the behavior of $\mathrm{PD}$ with the energy hint once more to the presence of QED effects in magnetars.
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https://arxiv.org/abs/2601.15452
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24962850f0994426500b90b0b3eb23913245cf8c9606e1803e6ed3d34837ad23
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2026-01-23T00:00:00-05:00
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Constraining nonminimal f(T) gravity from Primordial Nucleosynthesis to Late-Universe observations
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arXiv:2601.15460v1 Announce Type: new Abstract: We present a multi-epoch test of f(T) gravity with nonminimal torsion-matter coupling, combining early- and late-Universe observations. At the MeV scale, Big-Bang Nucleosynthesis constrains the fractional variation of the weak freeze-out temperature, |{\delta}{\tau}_f/{\tau}_f|, thereby mapping light-element abundances into limits on deviations from the standard expansion history. At low redshift, we confront the model with type Ia supernovae, baryon acoustic oscillations, and cosmic-chronometer data, which respectively probe distances, the late-time standard ruler, and the Hubble rate. Independent analyses highlight the complementary roles of each dataset, while a joint SNe Ia + BAO + CC fit breaks degeneracies and yields the tightest combined bounds. As an illustration, we examine two representative torsion-modified gravity scenarios: BBN strongly limits large departures from standard cosmology, whereas late-time probes remain compatible with a near-{\Lambda}CDM background. This unified approach demonstrates the power of linking early-Universe nuclear physics with precision cosmological observables in assessing torsional extensions of gravity.
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https://arxiv.org/abs/2601.15460
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386ee7849873a4e55976cc63c22d7c26ff8746dbc3ebb29f48af94d5d1f79bc7
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2026-01-23T00:00:00-05:00
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Two Fluid Quantum Bouncing Cosmology I: Theoretical Model
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arXiv:2601.15542v1 Announce Type: new Abstract: Bouncing cosmologies offer an alternative to inflation by resolving the initial singularity through a contracting phase followed by a bounce into expansion. In many such models, the contracting phase is dominated by a single matter component, typically pressureless dust, which leads to an almost scale-invariant spectrum of scalar cosmological perturbations with a slight blue tilt, so that generating the observed red-tilted spectrum within this framework was challenging. In this work, we consider a more realistic scenario in which the contracting phase includes both matter and radiation, as required on physical grounds. We show that the presence of radiation can naturally induce a red tilt in the spectrum of curvature perturbations seeded by quantum vacuum fluctuations in the remote past of the contraction. Since the perturbations of the two fluids are coupled via gravity, vacuum initial conditions must be carefully defined. We demonstrate that, without fine-tuning, the resulting entropy perturbations are subdominant with respect to curvature perturbations. This suggests that a minimal two-component bounce model, involving only ordinary matter and radiation, can connect to the standard expanding cosmology with observationally viable initial conditions.
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https://arxiv.org/abs/2601.15542
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544ab183f0f9c6f7e44ea0dde1ccbeb9add01bf60af25d405905bad5246c8bf8
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2026-01-23T00:00:00-05:00
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Source identification for the Swift-BAT 150-month hard X-ray catalog using soft X-ray observations
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arXiv:2601.15577v1 Announce Type: new Abstract: We present a comprehensive catalog of 251 potential counterparts for 250 unassociated hard X-ray sources detected in the Swift Burst Alert Telescope (BAT) 150-month hard X-ray survey. Over 150 months of observation, BAT has detected 2339 sources in the 15-150 keV energy range. Among these, 344 do not have a previously identified low-energy counterpart. Our study focuses on the analysis of soft X-ray observations at energies below 10 keV, spatially overlapping with these new Swift-BAT hard X-ray sources. Such observations were taken with Chandra, Swift-XRT, eROSITA, and XMM-Newton. Within the sample of 251 potential counterparts, 94 (37 percent) are identified as active galactic nuclei and 58 (23 percent) as galaxies. The remaining 99 sources (40 percent) include pulsars, cataclysmic variables, and unclassified soft X-ray counterparts in the 0.5-10 keV band. Redshift information is available for 139 out of the 251 sources, and its distribution is in close agreement with the redshift distribution of previous BAT catalogs. We also present the results of a small optical spectroscopy campaign of 9 out of 58 galaxies. The majority of these are classified as Seyfert 2 galaxies at redshifts slightly larger than the median of the BAT AGN sample.
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https://arxiv.org/abs/2601.15577
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8e0f5283e28a2fd466b714c9e89d18e7f84fbf6740af03965d874684cfe25a6d
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2026-01-23T00:00:00-05:00
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Mapping dark matter and the emergence of large-scale structure
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arXiv:2601.15583v1 Announce Type: new Abstract: We discuss a potential survey to map dark matter and the emergence of large-scale structure to redshift z ~ 1.5 (baseline) or z~3.5 (with near-IR extension) using a massively multiplexed spectrograph on a 10m-class telescope, such as the proposed Widefield Spectroscopic Telescope.
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https://arxiv.org/abs/2601.15583
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71ebca9bf1a94e3eec37d2f94ea7f70496f307633e70db5748ad0ef30d3fa15c
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2026-01-23T00:00:00-05:00
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Multi-band Reconstruction of Sixteen Gravitational Lens Systems using PISCO data
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arXiv:2601.15585v1 Announce Type: new Abstract: Next-generation surveys such as the Euclid survey, the Legacy Survey of Space and Time (LSST), and the China Space Station Telescope (CSST) survey are expected to discover ~10^5 galaxy-galaxy scale strong gravitational lenses. This motivates the development of scalable and robust lens modeling approaches that can efficiently and reliably learn from wide-field survey datasets before high-resolution follow-up. We design a scalable, Bayesian, Lenstronomy-based pipeline and apply it to a sample of sixteen lens candidates observed with the Parallel Imager for Southern Cosmology Observations (PISCO) on the Magellan telescope. PISCO provides four-band imaging (z, i, r, g) with colours, depth and seeing conditions comparable to LSST. To fully exploit the constraining power of this dataset, our pipeline performs simultaneous multi-band modeling, using a common mass profile across all four bands while allowing independent light profiles in each. This approach leverages color information to provide joint constraints on the lens mass and yields reduced uncertainties compared to single-band analyses. Fifteen out of sixteen PISCO lens candidates are successfully recovered with interpretable lensing configurations, including DESJ0533-2536, the first reported hyperbolic-umbilic galaxy-galaxy scale strong lensing candidate. We further assess how much model complexity can be reliably constrained given the resolution and seeing of PISCO-like data. Overall, our results demonstrate that scalable, multi-band lens modeling of ground-based data can extract meaningful constraints on mass and source morphology, providing a practical pathway to maximize the scientific return from large samples in upcoming surveys.
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https://arxiv.org/abs/2601.15585
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91d03479d403e804d3fe21b0e6f3b50b14515531253fcfe189e3ce8e1fbbd063
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2026-01-23T00:00:00-05:00
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A compact object with a K type star companion in the solar neighborhood: a wide post common envelope binary with a white dwarf candidate
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arXiv:2601.15619v1 Announce Type: new Abstract: Post-common envelope binaries (PCEBs) consisting of a white dwarf (WD) plus a main-sequence (MS) star can constrain current prescriptions of common envelope evolution (CEE) and calibrate theoretical models of binary formation and evolution. Most PCEBs studied to date have typical orbital periods of hours to a few days and can be well explained by assuming inefficient CEE to expel the envelope. However, there are currently several systems with relatively wide orbital periods ($>$18 days). To explain these wide PCEBs, additional sources of energy have been suggested to be taken into account. Here, we present the discovery and observational characterization of a compact object ($M\,\geq\,0.58\,\rm M_{\odot}$) with a K-type star companion in the solar neighborhood ($d\sim 112$ pc) and an orbital period of $P_{\rm orb}\sim 14$ days. The compact object binary is likely to be a system consisting of a WD and a barium dwarf. Such a system with an orbital period within the gap between tight and wide binaries provides a test of whether additional energy sources are required to explain its formation. Using binary evolution models, we investigate the evolutionary history of this wide PCEB system and find that the observed properties of this source can be explained without invoking any extra energy source.
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https://arxiv.org/abs/2601.15619
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cfd67a138860834aed745183aeb7fcfcc45aa7db8c628fe4f770d73c301671fa
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2026-01-23T00:00:00-05:00
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The initial spin matters: the impact of rapid rotation on magnetic-field amplification at merger
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arXiv:2601.15650v1 Announce Type: new Abstract: A couple of milliseconds after the merger of a binary system of neutron stars can play a fundamental role in amplifying the comparatively low initial magnetic fields into magnetar strengths. The basic mechanism responsible for this amplification is the Kelvin-Helmholtz instability (KHI) and we here report the first systematic study of the impact of rapid rotation on the KHI-amplification process exploiting general-relativistic magnetohydrodynamic simulations at very high-resolutions of $35\,{\rm m}$. Concentrating on four different spinning configurations, we find that aligned, anti-aligned, and mixed (aligned/anti-aligned) spin configurations lead to markedly different growth rates of the electromagnetic (EM) energy, field topologies, and vortex properties when compared to the irrotational case. These differences arise from intrinsic variations in the system dynamics, such as tidal deformation, collision strength, and contact surface area, with the anti-aligned configuration producing the largest vorticity and growth in EM energy. Importantly, while different spin configurations lead to significantly different initial growth rates of the poloidal/toroidal components, all systems converge to a specific topological partition. Our simulations are confined to a short window in time, but the different EM energies produced as a result of spin will imprint the EM emission at merger and provide information on the spinning state at merger.
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https://arxiv.org/abs/2601.15650
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fb0705b272c8c354fef18dea9a65598752ec5729ee8d110f3369e348d5d3344e
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2026-01-23T00:00:00-05:00
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K-DRIFT Science Theme: Galactic Cirrus Clouds and Circumgalactic Medium
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arXiv:2601.15665v1 Announce Type: new Abstract: In this paper, we review the extended halo material and the circumgalactic medium (CGM), including both dust and gas, and discuss promising science cases that could be realized using the KASI Deep Rolling Imaging Fast Telescope (K-DRIFT). Scattered starlight from cirrus clouds in our Galaxy poses one of the major challenges to studying the low surface brightness features of extragalactic sources. Therefore, it is essential to investigate how to discriminate extragalactic sources from the cirrus cloud features. At the same time, interstellar dust clouds themselves are fundamental to understanding dust properties and the interstellar radiation field, both of which are essential for studies of chemical evolution and star formation in our Galaxy. Measuring the reddening of background sources, such as quasars, with K-DRIFT, which benefits from its broad field of view and accurate background subtraction, allows for effective detection of extended dust in galactic halos, the CGM, and intracluster space. Observations of the H-alpha emission lines can be used to identify signatures of star formation activity within galaxies, as well as the environmental effects acting on them. Galactic winds driven by active galactic nuclei and starbursts can be traced through H-alpha emission. Strong ram pressure stripping effectively removes the interstellar medium (ISM) from galaxies. The stripped ISM becomes ionized or dissociated through mixing with the hot intracluster medium (ICM), forming H-alpha tails. The surface brightness of these H-alpha tails correlates not only with the presence of star formation in the tails but also the mixing stage of the stripped ISM and ICM. The H-alpha survey with K-DRIFT will enable the investigation of the evolutionary stages of ram pressure stripped galaxies in cluster environments, as well as the multiphase gas reservoir around galaxies and in the CGM.
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https://arxiv.org/abs/2601.15665
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d2d4f792b1558772210caacd2b9f3d06d279afb1b6a73f07fbf2a71d6b65ea18
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2026-01-23T00:00:00-05:00
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The reason for the occurrence of W-type contact binaries
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arXiv:2601.15672v1 Announce Type: new Abstract: For more than half a century, the puzzling W-type phenomenon in contact binaries has challenged astrophysicists. In these systems, the less massive component exhibits a higher surface temperature than its more massive companion, which is a reversal of the typical A-type configuration, where the more massive star is hotter. This counterintuitive temperature inversion defies the basic stellar physics and still lacks a widely accepted explanation. In this study, we assembled a sample of over 3,000 extensively observed contact binaries and derived their complete set of physical parameters. Our statistical analysis revealed a strong positive correlation between the occurrence of W-type contact binaries and the intensity and frequency of magnetic activities. This result strongly supports the hypothesis that magnetic activities are the primary driver of the W-type phenomenon and offers a compelling explanation for the observed transitions between the W-type and A-type.
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https://arxiv.org/abs/2601.15672
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fed3baafb0d0ca75e2a4e4975f170e4b0155bc03f7f279021854e16f1a1c5290
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2026-01-23T00:00:00-05:00
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Development of an early warning method incorporating pre-supernova neutrino light curves
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arXiv:2601.15691v1 Announce Type: new Abstract: Massive stars ($M>8\mathrm{M_\odot}$) emit neutrinos known as pre-supernova (pre-SN) neutrinos through thermal and nuclear interactions for cooling the stellar core during the final stage of stellar evolution. Real-time monitoring of their pre-SN neutrino interaction rate offers a crucial opportunity to issue an early warning to a core-collapse supernova. Some neutrino detectors, including KamLAND and Super-Kamiokande already operate pre-SN alarm systems based on a statistically significant excess of the observed event rate over the expected background. To improve alarm sensitivity, we propose an alarm method which incorporates the time evolution of the observed pre-SN neutrino event rate. The method uses a log likelihood ratio test that references multiple theoretical stellar-evolution models and treats the core collapse time as a nuisance parameter to be profiled over. The performance of the proposed method was evaluated using simulated data for the KamLAND, Super-Kamiokande with dissolved Gadolinium (SK-Gd) and their combined analysis. The results demonstrate a significant improvement in the warning time compared to the conventional rate-only method, while maintaining the same false alarm rate.
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https://arxiv.org/abs/2601.15691
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2cff9a0e913dda8c4b0797c3752728660d3065ef482e00b55bf7675626982ce7
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2026-01-23T00:00:00-05:00
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Evidence for stellar contamination and water absorption in NGTS-5b's transmission spectra with GTC/OSIRIS
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arXiv:2601.15704v1 Announce Type: new Abstract: Transmission spectroscopy serves as a valuable tool for probing atmospheric absorption features in the terminator regions of exoplanets. Stellar surface heterogeneity can introduce wavelength-dependent contamination that complicates the interpretation of planetary spectra. We aim to investigate the atmosphere of the warm sub-Saturn NGTS-5b through optical transmission spectroscopy. Two transits were observed with the low-resolution Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) on the 10.4 m Gran Telescopio Canarias (GTC). Chromatic transit light curves were modeled to derive optical transmission spectra and multiple Bayesian spectral retrievals were performed to characterize the atmospheric properties. Model comparisons provide strong evidence for contamination from unocculted stellar spots. A joint retrieval of the transmission spectra, assuming equilibrium chemistry, indicates a relatively clear atmosphere with a sub-solar C/O ratio of $<$0.22 (90% upper limit) and a low metallicity of $0.10^{+0.34}_{-0.05} \times$ solar. Retrievals assuming free chemistry yield strong evidence for the presence of $\rm H_2O$, with its abundance constrained to $\log X_{\mathrm{H_2O}} = -0.79^{+0.14}_{-0.17}$. However, the abundances of other species remain unconstrained due to the limited optical wavelength coverage. The discrepancies between the two NGTS-5b transit spectra can be attributed to varying levels of stellar contamination. NGTS-5b thus appears to host a relatively clear, water-rich atmosphere, pending confirmation from additional observations of molecular bands in the infrared.
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https://arxiv.org/abs/2601.15704
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Academic Papers
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8e15d8bb4298832c360c0527d898837726d4bdc4eea9988fbe3372a192ee4fec
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2026-01-23T00:00:00-05:00
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Hydrodynamic simulations of the recurrent nova T Coronae Borealis: Nucleosynthesis predictions
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arXiv:2601.15713v1 Announce Type: new Abstract: T Coronae Borealis (T CrB) is one of the eleven known recurrent novae in our Galaxy. It was observed in outburst in 1866 and 1946, with additional likely eruptions recorded in 1217 and 1787. Given its predicted recurrence period of approximately 80 yr, the next outburst is anticipated to occur imminently, thus motivating a thorough examination of the main characteristics of this system. We present new hydrodynamic models of the explosion of T CrB for different combinations of parameters (i.e., the mass, composition, and initial luminosity of the white dwarf, the metallicity of the accreted matter, and the mass-transfer rate). We show that mass-accretion rates between 10-8 - 10-7 Msun yr-1 are required to trigger an outburst after 80 yr of accretion of solar-composition material onto white dwarfs with masses about 1.30 - 1.38 Msun. For lower white dwarf luminosities, less massive white dwarfs, or reduced metallicity in the accreted material, higher mass-accretion rates are required to drive an explosion within this timescale. A decrease in metallicity or initial white dwarf luminosity leads to higher accumulated masses and ignition pressures, resulting in more violent outbursts. These outbursts exhibit higher peak temperatures, higher ejected masses, and greater kinetic energies. Models computed for different white dwarf masses but identical initial luminosities reveal significant differences in the elemental abundances of a wide range of species, including Ne, Na, Mg, Al, Si, P, S, Ar, K, Ca, and Sc. These compositional differences offer a potential diagnostic tool for constraining the parameter space and discriminating between the various T CrB models reported in this study.
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https://arxiv.org/abs/2601.15713
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Academic Papers
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07d5c4095e299bc39cd507bd1b8191f954b29010435c924b6d12f4ec608c9df3
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2026-01-23T00:00:00-05:00
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Fuzzy dark matter soliton core hosting a supermassive black hole as a dense low-mass perturber in strong gravitational lensing
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arXiv:2601.15718v1 Announce Type: new Abstract: Recent high-resolution imaging observations of strong lens systems reveal dense low-mass perturbers. We propose a soliton core, whose central density is boosted by a supermassive black hole (SMBH), in the fuzzy dark matter (FDM) model as an efficient perturber in strong gravitational lensing. The higher central density makes it less efficient in the tidal mass loss, and leads to the higher impact in gravitational lensing. We show that the mass profile of a $\sim 10^6M_\odot$ perturber in JVAS B1938+666, which does not resemble any known astronomical object, can be wel explained by a soliton core in the FDM model with the mass of $4\times 10^{-21}$eV hosting an SMBH with the mass of $4\times 10^5M_\odot$. The high mass of the SMBH may be explained by several scenarios that predcit heavy SMBH seeds such as the direct collapse black hole formation and primordial black holes.
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https://arxiv.org/abs/2601.15718
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5836d16dd1f1b13e53f7f8d497a8fc880348de80c42d21bf7e68514be7889a1d
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2026-01-23T00:00:00-05:00
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Interaction between the ejecta, the accretion disk, and the secondary star in the recurrent nova system U Sco
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arXiv:2601.15725v1 Announce Type: new Abstract: Most efforts in the modeling of recurrent novae have centered on the initial phases of the explosion and ejection, overlooking the subsequent interaction of the ejecta, first with the accretion disk orbiting the white dwarf and ultimately with the secondary star. To address this gap, a series of 3D smoothed-particle hydrodynamics simulations was conducted. These simulations explored the dynamic interactions between the nova ejecta, accretion disk, and stellar companion within the framework of the recurrent nova system U Sco. Notably, the simulations incorporate rotation around the system's center of mass. The primary goal of these simulations was to qualitatively examine the impact of various model parameters, including ejecta mass, velocity, and density, as well as the mass and geometry of the accretion disk. Simulations reveal complete disruption and sweeping of the accretion disk orbiting the white dwarf star for models with flared disks and Mejecta/Mdisk larger than 1. In contrast, V-shaped disks with a (constant) high initial density and Mejecta/Mdisk < 1 partially survive the impact with the nova ejecta. A very minor chemical contamination of the secondary star is anticipated in the U Sco case based on the limited impact of nova ejecta particles on the subgiant in all simulations. Minor mass ejection from the subgiant's outer layers is observed during the late-stage collision with ejecta and disk material, with some particles ejected from the binary system and some accreted by the white dwarf.
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https://arxiv.org/abs/2601.15725
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Academic Papers
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651afd5d53ea0d9f902d472599389e1ddcf9db172f90ca93739303ce8392e031
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2026-01-23T00:00:00-05:00
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GRB~250704B/EP250704a a Short Gamma-Ray Burst Powered by a Magnetar
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arXiv:2601.15732v1 Announce Type: new Abstract: GRB~250704B/EP250704a, identified as a short gamma-ray burst (sGRB), exhibited prolonged X-ray emission following the prompt phase and, in optical and infrared (IR) bands, an unusual one-day plateau succeeded by a rapid decline. This sGRB was observed by multiple satellites and ground-based observatories across the electromagnetic spectrum. This study presents temporal and spectral analyses from radio to gamma-ray frequencies, spanning several observation periods beginning after the trigger and continuing for nearly 2 days. The results of the temporal and spectral analyses of the prompt episode, the extended X-ray component, and the afterglow phase are consistent with a millisecond magnetar undergoing accretion. The long-lasting X-ray emission is attributed to the internal energy dissipation of the magnetar spin-down power, governed by the magnetization parameter; the extended optical/IR plateau to synchrotron afterglow emission with energy injection; and the steep decay to changes in microphysical parameters during the post-jet break phase. The X-ray observations are consistent with the superposition of spin-down luminosity and synchrotron afterglow scenario. These findings suggest that the compact-object remnant is most likely a long-lived magnetar.
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https://arxiv.org/abs/2601.15732
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b84474ef4722743ccca31c3d7523077d3264cb963b9ab9dd5a47368d60283492
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2026-01-23T00:00:00-05:00
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Nucleosynthesis in Type Ia Supernovae, Classical Novae, and Type I X-Ray Bursts. A Primer on Stellar Explosions
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arXiv:2601.15740v1 Announce Type: new Abstract: Nuclear astrophysics aims at unraveling the cosmic origins of chemical elements and the physical processes powering stars. It constitutes a truly multidisciplinary field, that integrates tools, advancements, and accomplishments from theoretical astrophysics, observational astronomy, cosmochemistry, and theoretical and experimental atomic and nuclear physics. For instance, the advent of high-energy astrophysics, facilitated by space-borne observatories, has ushered in a new era, offering a unique, panchromatic view of the universe (i.e., allowing multifrequency observations of stellar events); supercomputers are also playing a pivotal role, furnishing astrophysicists with computational capabilities essential for studying the intricate evolution of stars within a multidimensional framework; cosmochemists, through examination of primitive meteorites, are uncovering tiny fragments of stardust, shedding light on the physical processes operating in stars and on the mechanisms that govern condensation of stellar ejecta into solids; simultaneously, nuclear physicists managed to measure nuclear reactions at (or close to) stellar energies, using both stable and radioactive ion beam facilities. This paper provides a multidisciplinary view on nucleosynthesis accompanying stellar explosions, with a specific focus on thermonuclear supernovae, classical novae, and type I X-ray bursts.
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https://arxiv.org/abs/2601.15740
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Academic Papers
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e6c7e0ac8113cfb53c6f8ef892a2c92358faddeafc351677fc43dfc56012aa75
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2026-01-23T00:00:00-05:00
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Redshift-Binned Constraints on the Hubble Constant under $\Lambda$CDM, CPL, and Pad\'e Cosmography
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arXiv:2601.15765v1 Announce Type: new Abstract: Motivated by recent claims of a possible redshift dependence in late-Universe determinations of the Hubble constant ($H_0$), we test the robustness of this behaviour using multiple cosmological probes. We perform a joint redshift-binned analysis of $H_0$ across eight bins using late-Universe probes -- Pantheon+ SNe~Ia, DESI BAO, cosmic chronometers, and water megamasers -- under three cosmological frameworks: flat $\Lambda$CDM, CPL, and Pad\'e cosmography. Under a common baseline scheme, all three models show a qualitatively similar, low-amplitude variation in the per-bin $H_0$ estimates. A simple Fourier-like parametrization captures this behaviour, but the amplitude differs from zero only at a marginal significance of about $1.71$--$1.94\,\sigma$, with similar behaviour observed across all three cosmological frameworks. We then investigate the robustness and possible origin of this feature. Alternative binning schemes preserve its qualitative form, whereas single-probe per-bin fits (SNe-only, CC-only, BAO-only) yield ratios $H_{0,i}/H_{0,\mathrm{global}}$ mostly consistent with unity and do not reproduce the pronounced drift seen in the joint baseline constraints. Finally, by comparing different global versus piecewise-constant configurations for $\{H_0,\Omega_m,M,r_d\}$, we find that a baseline-like oscillatory pattern re-emerges only when multiple degenerate parameter combinations are allowed to vary across bins, while it is strongly suppressed when only $H_0$ is bin-dependent. Taken together, these results indicate that the apparent oscillatory behaviour of $H_0(z)$ in late-time arises from known parameter degeneracies and does not constitute robust evidence for a genuine redshift evolution.
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https://arxiv.org/abs/2601.15765
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Academic Papers
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3431103524d4c743fc80cc0660b25e8d1157e69bfcf4ca0b11c54d69855899e1
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2026-01-23T00:00:00-05:00
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Deuteration of HC3N and CH3CCH in the pre-stellar core L1544
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arXiv:2601.15791v1 Announce Type: new Abstract: Deuterated molecules are a useful diagnostic tool to probe the evolution and the kinematics in the earliest stages of star formation. Due to the low temperatures and high densities in the centre of pre-stellar cores, the deuterium fraction is enhanced by several orders of magnitude. We study the distribution of the emission and the deuteration of the two carbon chains HC3N and CH3CCH throughout the pre-stellar core L1544. We analyse emission maps of CH3CCH, CH2DCCH, CH3CCD, HC3N, HCC13CN, and DC3N, observed with the IRAM 30m single-dish radio telescope. We use non-LTE radiative transfer calculations, combined with chemical modelling of the molecular abundances, to constrain physical parameters of the observed species. Following this, we derive the column density and deuteration maps. We find D-fractions of N(DC3N)/N(HC3N)=0.04-0.07, N(CH2DCCH)/N(CH3CCH)=0.09-0.15, and N(CH3CCD)/N(CH3CCH)=0.07-0.09. The deuteration of HC3N appears homogeneous across the core, with widespread D-fraction values above 0.06, tracing intermediate-density gas in the outer layers of the core. CH3CCD is most efficiently formed in the higher-density regions towards the core centre, while the D-fraction of CH2DCCH traces a local density enhancement in the north-east of the core, coinciding with the CH3OH emission peak. The results suggest that gas-phase reactions dominate the formation and deuteration of both HC3N and CH3CCH in L1544, with spatial variations driven by physical structure, density and external radiation. The significantly higher D-fraction of CH2DCCH compared to CH3CCD and a tentative gradient with higher values in the north suggest different deuteration mechanisms for the two functional groups. Similarities between the CH2DCCH emission and CH2DOH might indicate an additional deuteration pathway of CH3CCH on the surfaces of dust grains, as observed for H2CO.
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https://arxiv.org/abs/2601.15791
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Academic Papers
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6411740069c1fddfd886e94c8ed246053964b527661fef858ff430b16d19a1db
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2026-01-23T00:00:00-05:00
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Failed ejection and oscillations of a current-carrying filament balanced by gravity
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arXiv:2601.15823v1 Announce Type: new Abstract: In this study, we investigate the post-destabilization evolution of a filament in a gravity-balanced model. We adopt the filament model proposed by Solov'ev (2010), in which a dense filament is supported against gravity by the repulsive force between the filament current and its sub-photospheric image. We first performed an analytical investigation of this model. For the numerical study, we use a two-dimensional magnetohydrodynamic (MHD) model that solves the MHD equations with the Lare2d numerical code. Results: In this filament model, analytical expressions are derived for the electric current density, plasma density, and their spatial distributions as functions of the model parameters. The total electric current and the filament weight are also calculated. For the numerical simulations, we constructed an equilibrium filament characterized by a magnetic field of $B_0$ = $10^{-3}$ T, mass density $\rho_0$ ~ 1.3 x $10^{-9}$ kg m$^{-3}$, and temperature T ~ 13000 K. The system was destabilized either by increasing the currents or by reducing the filament density, and its evolution was computed. In both destabilization regimes, the filament was ejected, then halted at a certain altitude, and subsequently fell back, repeating this cycle with a period of about 600 s. The maximum filament ejection velocity was approximately 80 and 40 km $s^{-1}$, respectively. Beneath the ejected filament a current sheet forms, where magnetic reconnection occurs. The maximum ejection altitudes were determined as functions of both the destabilizing currents and the degree of filament plasma dilution. Finally, we compared results of this MHD model with those of an ideal vacuum model and discussed all results.
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https://arxiv.org/abs/2601.15823
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01d98c2ba43e50a2b0a3311e00ecff5e496bed5e909992477ab4914277661c46
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2026-01-23T00:00:00-05:00
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Radio-Interferometric Image Reconstruction with Denoising Diffusion Restoration Models
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arXiv:2601.15844v1 Announce Type: new Abstract: Reconstructing images of the radio sky from incomplete Fourier information is a key challenge in radio astronomy. In this work, we present a method for radio interferometeic image reconstruction using a data-driven prior for the radio sky based on denoising diffusion probabilistic models (DDPMs). We first train a DDPM on radio galaxy observations from the VLA FIRST survey. We create simulated VLA, EHT, and ALMA observations of radio galaxies, then use an unsupervised posterior sampling method called Denoising Diffusion Restoration Models (DDRM) to reconstruct the corresponding images, using our DDPM as a prior. Our approach is agnostic to the measured radio interferometric data and naturally incorporates the physics of the measurement process. We are able to reconstruct images with very high fidelity PSNR>60, a marked improvement over CLEAN and similar image reconstruction methods using conditional DDPMs
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https://arxiv.org/abs/2601.15844
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07423fc3bc33bf7d54ee8760f527059e338bd41582a6a171eba0e7abdab65dd5
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2026-01-23T00:00:00-05:00
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Intrinsic alignments in the FLAMINGO simulations with two-point statistics
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arXiv:2601.15851v1 Announce Type: new Abstract: Intrinsic alignments are a major astrophysical contaminant for next generation large-sky surveys like Euclid and LSST. Large hydrodynamic simulations are crucial for informing the alignment modelling for these surveys. We measure position-position and position-shape correlations of a Luminous Red Galaxy sample from the FLAMINGO suite of hydrodynamical simulations, measuring the alignment signal for more than 4.9 million galaxies at redshift 0. We jointly model the clustering and alignment correlations to provide the tightest constraints on the alignment amplitude to date from a hydrodynamic simulation. We find that both the Non-Linear Alignment (NLA) and the more complex Tidal Alignment Tidal Torquing (TATT) models provide good fits to the data. We compare the measured $A_1$ amplitude to observational data and find good agreement. We measure the dependence of the NLA and TATT free parameters on halo mass. We also introduce a mass-dependent TATT model, TATT-M, by finding empirical relations between the halo mass and the TATT parameters. This allows us to fit TATT with only one parameter, $A_1$, with $A_2/A_1$ being a constant and $A_{1\delta}/A_1$ being a function of halo mass. Using a Bayesian approach, we find that TATT-M is very strongly preferred by the data over NLA. Using the baryonic feedback variations of the FLAMINGO simulation suite, we test whether the TATT parameters are sensitive to feedback. Variations in AGN and supernova feedback do not significantly change the alignment amplitude beyond the change associated with the dependence of galaxy stellar mass on the strength of feedback. Our results inform the IA modelling for upcoming surveys by providing guidance on model choices, priors and sensitivities to feedback.
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https://arxiv.org/abs/2601.15851
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Academic Papers
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31f249a6f5a5d3e68034cadee81f4fb60f16a62d2950dd1dbf91b25b84c488b7
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2026-01-23T00:00:00-05:00
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Does the solar oxygen abundance change over the solar cycle? An investigation into activity-induced variations of the O I infrared triplet
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arXiv:2601.15919v1 Announce Type: new Abstract: The determination of the solar oxygen abundance remains a central problem in astrophysics, as its accuracy is limited not only by models but also by systematics. While many of these factors have been thoroughly characterized, the effect of the solar activity cycle has so far remained unexplored. Due to its relative strength and accessibility, the O I infrared triplet is typically the primary choice for abundance studies. However, previous investigations have shown that abundances inferred from this triplet tend to be higher than expected on active stars, whereas such an overabundance effect is not observed for the much weaker forbidden O I 6300 \r{A} line. This raises the question of whether a similar trend can be found for the Sun. To address this question, we analyze two decades' worth of synoptic disk-integrated Sun-as-a-star datasets from the FEROS, HARPS-N, PEPSI, and NEID spectrographs, focusing on the infrared triplet (7772, 7774, 7775 \r{A}) and the forbidden O I 6300 \r{A} line. The excellent signal-to-noise ratio of the PEPSI observations allows us to detect a weak but significant variation in the equivalent widths of the infrared triplet, corresponding to about 0.01 dex difference in abundance between activity minimum and maximum. This value is significantly smaller than the typical uncertainties on the solar oxygen abundance. Due to higher scatter, no comparable trend is found in the other data sets. Based on these results, we conclude that within the typical uncertainties presented in other works, we can assume the inferred solar oxygen abundance to be stable across the solar cycle, but that this effect may be significant for other, more active stars.
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https://arxiv.org/abs/2601.15919
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Academic Papers
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