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arxiv_dataset-37001209.2836 | The homogeneous Sobolev metric of order one on diffeomorphism groups on
the real line
math.AP math.DG
In this article we study Sobolev metrics of order one on diffeomorphism
groups on the real line. We prove that the space
$\operatorname{Diff}_{1}(\mathbb R)$ equipped with the homogenous Sobolev
metric of order one is a flat space in the sense of Riemannian geometry, as it
is isometric to an open subset of a mapping space equipped with the flat
$L^2$-metric. Here $\operatorname{Diff}_{1}(\mathbb R)$ denotes the extension
of the group of all either compactly supported, rapidly decreasing or
$H^\infty$-diffeomorphisms, that allows for a shift towards infinity. In
particular this result provides an analytic solution formula for the
corresponding geodesic equation, the non-periodic Hunter-Saxton equation. In
addition we show that one can obtain a similar result for the two-component
Hunter-Saxton equation and discuss the case of the non-homogenous Sobolev one
metric which is related to the Camassa-Holm equation.
| arxiv topic:math.AP math.DG |
arxiv_dataset-37011209.2936 | Universality and intermittency in relativistic turbulent flows of a hot
plasma
astro-ph.HE gr-qc physics.flu-dyn
With the aim of determining the statistical properties of relativistic
turbulence and unveiling novel and non-classical features, we resent the
results of direct numerical simulations of driven turbulence in an
ultrarelativistic hot plasma using high-order numerical schemes. We study the
statistical properties of flows with average Mach number ranging from $\sim
0.4$ to $\sim 1.7$ and with average Lorentz factors up to $\sim 1.7$. We find
that flow quantities, such as the energy density or the local Lorentz factor,
show large spatial variance even in the subsonic case as compressibility is
enhanced by relativistic effects. The velocity field is highly intermittent,
but its power-spectrum is found to be in good agreement with the predictions of
the classical theory of Kolmogorov. Overall, our results indicate that
relativistic effects are able to significantly enhance the intermittency of the
flow and affect the high-order statistics of the velocity field, while leaving
unchanged the low-order statistics, which instead appear to be universal and in
good agreement with the classical Kolmogorov theory. To the best of our
knowledge, these are the most accurate simulations of driven relativistic
turbulence to date.
| arxiv topic:astro-ph.HE gr-qc physics.flu-dyn |
arxiv_dataset-37021209.3036 | Busemann functions and infinite geodesics in two-dimensional
first-passage percolation
math.PR
We study first-passage percolation on Z2, where the edge weights are given by
a translation-ergodic distribution, addressing questions related to existence
and coalescence of infinite geodesics. Some of these were studied in the late
90's by C. Newman and collaborators under strong assumptions on the limiting
shape and weight distribution. In this paper we develop a framework for working
with distributional limits of Busemann functions and use it to prove forms of
Newman's results under minimal assumptions. For instance, we show a form of
coalescence of long finite geodesics in any deterministic direction. We also
introduce a purely directional condition which replaces Newman's global
curvature condition and whose assumption we show implies the existence of
directional geodesics. Without this condition, we prove existence of infinite
geodesics which are directed in sectors. Last, we analyze distributional limits
of geodesic graphs, proving almost-sure coalescence and nonexistence of
infinite backward paths. This result relates to the conjecture of nonexistence
of "bigeodesics."
| arxiv topic:math.PR |
arxiv_dataset-37031209.3136 | Quantum Zeno effect in an unstable system with NMR
quant-ph cond-mat.mes-hall
We theoretically propose a scheme for verification of quantum Zeno effect
(QZE) to suppress a decay process with Nuclear Magnetic Resonance (NMR).
Nuclear spins are affected by low frequency noise, and so one can naturally
observe non-exponential decay behavior, which is prerequisite in observing QZE.
We also describe that a key component for QZE, namely measurements on the
nuclear spin, can be realized with NMR in the current technology
| arxiv topic:quant-ph cond-mat.mes-hall |
arxiv_dataset-37041209.3236 | A note on "Folding wheels and fans."
math.CO cs.DM
In S.Gervacio, R.Guerrero and H.Rara, Folding wheels and fans, Graphs and
Combinatorics 18 (2002) 731-737, the authors obtain formulas for the clique
numbers onto which wheels and fans fold. We present an interpolation theorem
which generalizes their theorems 4.2 and 5.2. We show that their formula for
wheels is wrong. We show that for threshold graphs, the achromatic number and
folding number coincides with the chromatic number.
| arxiv topic:math.CO cs.DM |
arxiv_dataset-37051209.3336 | Spin down of the core rotation in red giants
astro-ph.SR
The space mission Kepler provides us with long and uninterrupted photometric
time series of red giants. We are now able to probe the rotational behaviour in
their deep interiors using the observations of mixed modes. We aim to measure
the rotational splittings in red giants and to derive scaling relations for
rotation related to seismic and fundamental stellar parameters. We have
developed a dedicated method for automated measurements of the rotational
splittings in a large number of red giants. Ensemble asteroseismology, namely
the examination of a large number of red giants at different stages of their
evolution, allows us to derive global information on stellar evolution. We have
measured rotational splittings in a sample of about 300 red giants. We have
also shown that these splittings are dominated by the core rotation. Under the
assumption that a linear analysis can provide the rotational splitting, we
observe a small increase of the core rotation of stars ascending the red giant
branch. Alternatively, an important slow down is observed for red-clump stars
compared to the red giant branch. We also show that, at fixed stellar radius,
the specific angular momentum increases with increasing stellar mass. Ensemble
asteroseismology indicates what has been indirectly suspected for a while: our
interpretation of the observed rotational splittings leads to the conclusion
that the mean core rotation significantly slows down during the red giant
phase. The slow-down occurs in the last stages of the red giant branch. This
spinning down explains, for instance, the long rotation periods measured in
white dwarfs
| arxiv topic:astro-ph.SR |
arxiv_dataset-37061209.3436 | A search for Wilson primes
math.NT cs.DS
A Wilson prime is a prime p such that (p-1)! = -1 mod p^2. We report on a
search for Wilson primes up to 2 * 10^13, and describe several new algorithms
that were used in the search. In particular we give the first known algorithm
that computes (p-1)! mod p^2 in average polynomial time per prime.
| arxiv topic:math.NT cs.DS |
arxiv_dataset-37071209.3536 | R-matrices for quantum affine algebras and Khovanov-Lauda-Rouquier
algebras, I
math.RT math.QA
Let us consider a finite set of pairs consisting of good $U'_q(g)$-modules
and invertible elements. The distribution of poles of normalized R-matrices
yields Khovanov-Lauda-Rouquier algebras We define a functor from the category
of finite-dimensional modules over the KLR algebra to the category of
finite-dimensional $U_q'(g)$-modules. We show that the functor sends
convolution products to tensor products and is exact if the KLR albera is of
type A, D, E.
| arxiv topic:math.RT math.QA |
arxiv_dataset-37081209.3636 | Top quark physics in the Vector Color-Octet Model
hep-ph
We study and constrain the parameter space of the vector color-octet model
from observed data at Tevatron by studying top quark pair production and
associated observables afbt and spin-correlation. In particular we study
invariant mass and rapidity dependence of afbt at Tevatron. In addition to FC
couplings we extend our study to include FV coupling involving first & third
generation quarks for both these processes. In order to ensure that we remain
within the constraints imposed by LHC data, we analyze the charge asymmetry,
p_T spectrum & invariant mass in t\bar t production data at LHC. The
constraints from dijet resonance searches performed by LHC are also considered.
We also explore the contribution of this model to single top quark production
mediated by charged & neutral color-octet vector bosons. FV couplings
introduced then induce same-sign top-pair production process which is analyzed
for both hadron colliders. We have incorporated effect of finite decay width of
color octets on these processes. We find that it is possible to explain the
observed afbt anomaly in color-octet vector model without transgressing
production cross sections of all these processes both through FC and FV
couplings at Tevatron. We predict best point sets in model parameter space for
specific choices of color-octet masses corresponding to chi^2_min evaluated
using mttb and dyy spectrum of afbt from observed data set at Tevatron (8.7
fb-1). We find that single top quark production is more sensitive to FC and FV
couplings in comparison to top-pair production. We provide 95% exclusion
contours on the plane of FV chiral couplings from recent data at Tevatron, CMS
and ATLAS corresponding to nonobservability of large same-sign dilepton events.
The four observed point sets are consistent with the cross section, charge
asymmetry and spin-correlation measurements for t\bar t production & dijet
searches at LHC.
| arxiv topic:hep-ph |
arxiv_dataset-37091209.3736 | Security and Efficiency analysis of Fully Homomorphic Encryption (FHE)
algorithm ZK111
cs.CR
This is a summarized follow up of the unconditional security and quadratic
time O(n^2) efficiency of ZK111.
| arxiv topic:cs.CR |
arxiv_dataset-37101209.3836 | Degeneration scheme of 4-dimensional Painlev\'e-type equations
math.CA nlin.SI
Four 4-dimensional Painlev\'e-type equations are obtained by isomonodromic
deformation of Fuchsian equations: they are the Garnier system in two
variables, the Fuji-Suzuki system, the Sasano system, and the sixth matrix
Painlev\'e system. Degenerating these four source equations, we systematically
obtained other 4-dimensional Painlev\'e-type equations. If we only consider
Painlev\'e-type equations whose associated linear equations are of unramified
type, there are 22 types of 4-dimensional Painlev\'e-type equations: 9 of them
are partial differential equations, 13 of them are ordinary differential
equations. Some well-known equations such as Noumi-Yamada systems are included
in this list. They are written as Hamiltonian systems, and their Hamiltonians
are neatly written using Hamiltonians of the classical Painlev\'e equations.
| arxiv topic:math.CA nlin.SI |
arxiv_dataset-37111209.3936 | Topological Entropy Conjecture
math.DS math.AT
In 1974, M. Shub stated Topological Entropy Conjecture, that is, the
inequality $\log\rho\leq ent(f)$ is valid or not, where $f$ is a continuous
self-map on a compact manifold $M$, $ent(f)$ is the topological entropy of $f$
and $\rho$ is the maximum absolute eigenvalue of $f_*$ which is the linear
transformation induced by $f$ on the homology group
$H_{*}(M;\mathbb{Z})=\bigoplus\limits_{i=0}^n{H_{i}(M;\mathbb{Z})}$. In 1986,
A. B. Katok gave a counterexample such that the inequality $\log\rho\leq
ent(f)$ is invalid. In this paper, we define $f$-\v{C}ech homology group
$\check{H}_{i}(X,f;\mathbb{Z})$ and topological fiber entropy $ent(f_L)$ on
compact Hausdorff space $X$ for which there is $n=n(J)$ such that
$\check{H}_*(X;\mathbb{Z})$ exists, where $f\in C^0(X)$ and $J$ is the set of
all covers. Then we prove that $\log\rho\leq ent(f_L)$ is valid.
| arxiv topic:math.DS math.AT |
arxiv_dataset-37121209.4036 | Novel States of Classical Light and Noncontextuality
quant-ph physics.optics
A new criterion, based on noncontextuality, is derived to discriminate
between separable and nonseparable states in classical wave optics where no
discreteness is involved. An experiment is proposed to test the violation of
noncontextuality by a nonseparable state. Such states have only recently begun
to be explored. The significance of their nonseparability or entanglement as
well as their similarities with and differences from entangled quantum states
are discussed.
| arxiv topic:quant-ph physics.optics |
arxiv_dataset-37131209.4136 | The Rohlin property for coactions of finite dimensional $C^*$-Hopf
algebras on unital $C^*$-algebras
math.OA
We shall introduce the approximate representability and the Rohlin property
for coactions of a finite dimensional $C^*$-Hopf algebra on a unital
$C^*$-algebra and discuss some basic properties of approximately representable
coactions and coactions with the Rohlin property of a finite dimensional
$C^*$-Hopf algebra on a unital $C^*$-algebra. Also, we shall give an example of
an approximately representable coaction of a finite dimensional $C^*$-Hopf
algebra on a simple unital $C^*$-algebra which has also the Rohlin property and
we shall give the 1-cohomology vanishing theorem for coactions of a finite
dimensional $C^*$-Hopf algebra on a unital $C^*$-algebra and the 2-cohomology
vanishing theorem for twisted coactions of a finite dimensional $C^*$-Hopf
algebra on a unital $C^*$-algebra. Furthermore, we shall introduce the notion
of the approximately unitary equivalence of coactions of a finite dimensional
$C^*$-Hopf algebra $H$ on a unital $C^*$-algebra $A$ and show that if $\rho$
and $\sigma$, coactions of $H$ on a separable unital $C^*$-algebra $A$, which
have the Rohlin property, are approximately unitarily equivalent, then there is
an approximately inner automorphism $\alpha$ on $A$ such that
$\sigma=(\alpha\otimes\id)\circ\rho\circ\alpha^{-1}$.
| arxiv topic:math.OA |
arxiv_dataset-37141209.4236 | Estimation of Radio Interferometer Beam Shapes Using Riemannian
Optimization
astro-ph.IM cs.CE
The knowledge of receiver beam shapes is essential for accurate radio
interferometric imaging. Traditionally, this information is obtained by
holographic techniques or by numerical simulation. However, such methods are
not feasible for an observation with time varying beams, such as the beams
produced by a phased array radio interferometer. We propose the use of the
observed data itself for the estimation of the beam shapes. We use the
directional gains obtained along multiple sources across the sky for the
construction of a time varying beam model. The construction of this model is an
ill posed non linear optimization problem. Therefore, we propose to use
Riemannian optimization, where we consider the constraints imposed as a
manifold. We compare the performance of the proposed approach with traditional
unconstrained optimization and give results to show the superiority of the
proposed approach.
| arxiv topic:astro-ph.IM cs.CE |
arxiv_dataset-37151209.4336 | Corners of Cuntz-Krieger algebras
math.OA
We show that if $A$ is a unital $C^*$-algebra and $B$ is a Cuntz-Krieger
algebra for which $A\otimes\mathbb{K} \cong B\otimes\mathbb{K}$, then $A$ is a
Cuntz-Krieger algebra. Consequently, corners of Cuntz-Krieger algebras are
Cuntz-Krieger algebras.
| arxiv topic:math.OA |
arxiv_dataset-37161209.4436 | Morita contexts as lax functors
math.CT
Monads are well known to be equivalent to lax functors out of the terminal
category. Morita contexts are here shown to be lax functors out of the chaotic
category with two objects. This allows various aspects in the theory of Morita
contexts to be seen as special cases of general results about lax functors. The
account we give of this could serve as an introduction to lax functors for
those familiar with the theory of monads. We also prove some very general
results along these lines relative to a given 2-comonad, with the classical
case of ordinary monad theory amounting to the case of the identity comonad on
Cat.
| arxiv topic:math.CT |
arxiv_dataset-37171209.4536 | Collisional Excitation of the [CII] Fine Structure Transition in
Interstellar Clouds
astro-ph.GA
We analyze the collisional excitation of the 158 micron (1900.5 GHz) fine
structure transition of ionized carbon (C+) in terms of line intensities
produced by simple cloud models. The single C+ fine structure transition is a
very important coolant of the atomic interstellar medium and of photon
dominated regions in which carbon is partially or completely in ionized form.
The [CII] line is widely used as a tracer of star formation in the Milky Way
and other galaxies. Excitation of the [CII] fine structure transition can be
via collisions with hydrogen molecules, atoms, and electrons. Velocity-resolved
observations of [CII] have become possible with the HIFI instrument on Herschel
and the GREAT instrument on SOFIA. Analysis of these observations is
complicated by the fact that it is difficult to determine the optical depth of
the [CII] line due to the relative weakness and blending of the components of
the analogous transition of 13C$+. We discuss the excitation and radiative
transition of the [CII] line, deriving analytic results for several limiting
cases and carry out numerical solutions using a large velocity gradient model
for a more inclusive analysis. We show that for antenna temperatures up to 1/3
of the brightness temperature of the gas kinetic temperature, the antenna
temperature is linearly proportional to the column density of C+ irrespective
of the optical depth of the transition, which can be referred to as the
effectively optically thin (EOT) approximation. We review the critical
densities for excitation of the [CII] line by various collision partners. We
briefly analyze C+ absorption and conclude with a discussion of C+ cooling and
how the considerations for line intensities affect the behavior of this
important coolant of the ISM.
| arxiv topic:astro-ph.GA |
arxiv_dataset-37181209.4636 | The unbiased measurement of UV spectral slopes in low luminosity
galaxies at z=7
astro-ph.CO
The Ultraviolet (UV) continuum slope beta, typically observed at z=7 in
Hubble Space Telescope (HST) WFC3/IR bands via the J-H colour, is a useful
indicator of the age, metallicity, and dust content of high-redshift stellar
populations. Recent studies have shown that the redward evolution of beta with
cosmic time from redshift 7 to 4 can be largely explained by a build up of
dust. However, initial claims that faint z=7 galaxies in the Hubble Ultra Deep
Field WFC3/IR imaging (HUDF09) were blue enough to require stellar populations
of zero reddening, low metallicity and young ages, hitherto unseen in
star-forming galaxies, have since been refuted and revised. Here we revisit the
question of how best to measure the UV slope of z=7 galaxies through source
recovery simulations, within the context of present and future ultra-deep
imaging from HST. We consider how source detection, selection and colour
measurement have each biased the measurement of beta in previous studies. After
finding a robust method for measuring beta in the simulations (via a power law
fit to all the available photometry), we remeasure the UV slopes of a sample of
previously published low luminosity z=7 galaxy candidates. The mean UV slope of
faint galaxies in this sample appears consistent with an intrinsic distribution
of normal star-forming galaxies with beta=-2, although properly decoding the
underlying distribution will require further imaging from the ongoing HUDF12
programme. We therefore go on to consider strategies for obtaining better
constraints on the underlying distribution of UV slopes at z=7 from these new
data, which will benefit particularly from the addition of imaging in a second
J-band filter: F140W. We find that a precise and unbiased measurement of beta
should then be possible.
| arxiv topic:astro-ph.CO |
arxiv_dataset-37191209.4736 | Quasi-exact solvability, resonances and trivial monodromy in ordinary
differential equations
math-ph hep-th math.MP quant-ph
A correspondence between the sextic anharmonic oscillator and a pair of
third-order ordinary differential equations is used to investigate the
phenomenon of quasi-exact solvability for eigenvalue problems involving
differential operators with order greater than two. In particular, links with
Bender-Dunne polynomials and resonances between independent solutions are
observed for certain second-order cases, and extended to the higher-order
problems.
| arxiv topic:math-ph hep-th math.MP quant-ph |
arxiv_dataset-37201209.4836 | Relationship between low and high frequencies in Delta Scuti stars:
Photometric Kepler and spectroscopic analyses of the rapid rotator KIC
8054146
astro-ph.SR
Two years of Kepler data of KIC 8054146 (delta Sct/gamma Dor hybrid) revealed
349 statistically significant frequencies between 0.54 and 191.36 c/d (6.3
microHz to 2.21 mHz). The 117 low frequencies cluster in specific frequency
bands, but do not show the equidistant period spacings predicted for gravity
modes of successive radial order, n, and reported for at least one other hybrid
pulsator. The four dominant low frequencies in the 2.8 to 3.0 c/d (32 to 35
microHz) range show strong amplitude variability with timescales of months and
years. These four low frequencies also determine the spacing of the higher
frequencies in and beyond the delta Sct pressure-mode frequency domain. In
fact, most of the higher frequencies belong to one of three families with
spacings linked to a specific dominant low frequency. In the Fourier spectrum,
these family regularities show up as triplets, high-frequency sequences with
absolutely equidistant frequency spacings, side lobes (amplitude modulations)
and other regularities in frequency spacings. Furthermore, within two families
the amplitude variations between the low and high frequencies are related. We
conclude that the low frequencies (gravity modes, rotation) and observed high
frequencies (mostly pressure modes) are physically connected. This unusual
behavior may be related to the very rapid rotation of the star: from a
combination of high and low-resolution spectroscopy we determined that KIC
8054146 is a very fast rotator (v sin i = 300 +/- 20 km/s) with an effective
temperature of 7600 +/- 200 K and a surface gravity log g of 3.9 +/- 0.3.
Several astrophysical ideas explaining the origin of the relationship between
the low and high frequencies are explored.
| arxiv topic:astro-ph.SR |
arxiv_dataset-37211209.4936 | Continuum Percolation Thresholds in Two Dimensions
cond-mat.stat-mech cond-mat.dis-nn cs.CG
A wide variety of methods have been used to compute percolation thresholds.
In lattice percolation, the most powerful of these methods consists of
microcanonical simulations using the union-find algorithm to efficiently
determine the connected clusters, and (in two dimensions) using exact values
from conformal field theory for the probability, at the phase transition, that
various kinds of wrapping clusters exist on the torus. We apply this approach
to percolation in continuum models, finding overlaps between objects with
real-valued positions and orientations. In particular, we find precise values
of the percolation transition for disks, squares, rotated squares, and rotated
sticks in two dimensions, and confirm that these transitions behave as
conformal field theory predicts. The running time and memory use of our
algorithm are essentially linear as a function of the number of objects at
criticality.
| arxiv topic:cond-mat.stat-mech cond-mat.dis-nn cs.CG |
arxiv_dataset-37221209.5036 | Proof of Church's Thesis
cs.LO
We prove that if our calculating capability is that of a universal Turing
machine with a finite tape, then Church's thesis is true. This way we
accomplish Post (1936) program.
| arxiv topic:cs.LO |
arxiv_dataset-37231209.5136 | Complete Ionisation of the Neutral Gas in High Redshift Radio Galaxies
and Quasars
astro-ph.CO
Cool neutral gas provides the raw material for all star formation in the
Universe, and yet, from a survey of the hosts of high redshift radio galaxies
and quasars, we find a complete dearth of atomic (HI 21-cm) and molecular (OH,
CO, HCO+ & HCN) absorption at redshifts z > 3. Upon a thorough analysis of the
optical photometry, we find that all of our targets have ionising ultra-violet
continuum luminosities of logL > 23 W/Hz. We therefore attribute this deficit
to the traditional optical selection of targets biasing surveys towards the
most ultra-violet luminous objects, where the intense radiation excites the
neutral gas to the point where it cannot engage in star formation. However,
this hypothesis does not explain why there is a critical luminosity, rather
than a continuum where the detections gradually become fewer and fewer as the
harshness of the radiation increases. We show that by placing a quasar within a
galaxy of gas there is always a finite ultra-violet luminosity above which all
of the gas is ionised. This demonstrates that these galaxies are probably
devoid of star-forming material rather than this being at abundances below the
sensitivity limits of current radio telescopes.
| arxiv topic:astro-ph.CO |
arxiv_dataset-37241209.5236 | Rigorous elimination of fast stochastic variables from the linear noise
approximation using projection operators
cond-mat.stat-mech physics.chem-ph q-bio.MN
The linear noise approximation (LNA) offers a simple means by which one can
study intrinsic noise in monostable biochemical networks. Using simple physical
arguments, we have recently introduced the slow-scale LNA (ssLNA) which is a
reduced version of the LNA under conditions of timescale separation. In this
paper, we present the first rigorous derivation of the ssLNA using the
projection operator technique and show that the ssLNA follows uniquely from the
standard LNA under the same conditions of timescale separation as those
required for the deterministic quasi-steady state approximation. We also show
that the large molecule number limit of several common stochastic model
reduction techniques under timescale separation conditions constitutes a
special case of the ssLNA.
| arxiv topic:cond-mat.stat-mech physics.chem-ph q-bio.MN |
arxiv_dataset-37251209.5336 | Constructing quasi-equilibrium initial data for binary neutron stars
with arbitrary spins
gr-qc astro-ph.SR
In general neutron stars in binaries are spinning. Recently, a new
quasi-equilibrium approximation that includes a rotational velocity piece for
each star has been proposed to describe binary neutron stars with arbitrary
rotation states in quasi-circular orbits. We have implemented this
approximation numerically for the first time, to generate initial data for
neutron star binaries with spin. If we choose the rotational velocity piece
such that it equals the Newtonian rigid rotation law, we obtain stars with
fluid 4-velocities that have expansion and shear of approximately zero, as one
would expect for quasi-equilibrium configurations. We also use the new approach
to construct and study initial data sequences for irrotational, corotating and
fixed rotation binaries.
| arxiv topic:gr-qc astro-ph.SR |
arxiv_dataset-37261209.5436 | Structural, chemical and electronic properties of the Co2MnSi(001)/MgO
interface
cond-mat.mtrl-sci
The performance of advanced magnetic tunnel junctions build of ferromagnetic
(FM) electrodes and MgO as insulating barrier depends decisively on the
properties of the FM/insulator interface. Here, we investigate interface
formation between the half-metallic compound Co2MnSi (CMS) and MgO by means of
Auger electron spectroscopy, low energy electron diffraction and low energy
photoemission. The studies are performed for different annealing temperatures
TA and MgO layer coverages (4, 6, 10, 20 and 50 ML). Thin MgO top layers
(t_MgO<=10 ML) show distinct surface crystalline distortions, which can only be
partly healed out by annealing and furthermore lead to distinct adsorption of
carbon species after the MgO surface is exposed to air. For t_MgO> 10 ML the
MgO layer surface exhibits clearly improved crystalline structure and hence
only marginal amounts of adsorbates. We attribute these findings to MgO misfit
dislocations occurring at the interface, inducing further defects throughout
the MgO layer for up to at least 10 ML. Furthermore, spin-polarized
photoemission spectra of the CMS/MgO interface are obtained for MgO coverages
up to 20 ML, showing a clear positive spin polarization near the Fermi energy
in all cases.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-37271209.5536 | Implicit Phonon Shifts and Thermodynamical Properties of Rigid Carbon
Nanotube Ropes
cond-mat.mes-hall
We calculate phonon shifts of external modes of a bunch of carbon nanotubes.
A simple model based on atom-atom potential has been used to calculate the
implicit anharmonicity in the phonons of carbon nanotube bundles having rigid
tubes, with the assumption that under hydrostatic pressure only the intertube
distance in the bunch varies. Such a model is important as long carbon nanotube
ropes will be an extension of a fixed length ropes as is done here. Various
bulk and thermodynamic properties like thermal expansion, bulk modulus and the
Gruneisen constants and external phonon shifts which naturally enter into the
calculation are also described and compared with the available data. The
specific heat capacity has also been calculated.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-37281209.5636 | Heavy Flavour Measurements in pp and Pb--Pb Collisions with the ALICE
Experiment at LHC
hep-ex nucl-ex
Heavy flavour is mainly produced during the initial hard partonic
interactions in a heavy ion collision, and is well-suited to probe the early
phases of the evolution of the system. This contribution will focus on Pb--Pb
analyses at a centre-of-mass energy per nucleon pair of 2.76 TeV, with some
hints at the $\pp$ data at 7 and 2.76 TeV. Results of open heavy flavour
analyses will be shown for various decay channels, including electrons, muons,
and hadronic charm decays, together with results obtained for heavy quarkonia
at both central and forward rapidities.
| arxiv topic:hep-ex nucl-ex |
arxiv_dataset-37291209.5736 | Quantum Metrology Assisted with Abstention
quant-ph
The main goal of quantum metrology is to obtain accurate values of physical
parameters using quantum probes. In this context, we show that abstention,
i.e., the possibility of getting an inconclusive answer at readout, can
drastically improve the measurement precision. We focus on phase estimation and
quantify the required amount of abstention for a given precision. We also
develop analytical tools to obtain the asymptotic behavior of the precision and
required rate of abstention for arbitrary pure qubit states.
| arxiv topic:quant-ph |
arxiv_dataset-37301209.5836 | Investigation of Hill Cipher Modifications Based on Permutation and
Iteration
cs.CR
Two recent Hill cipher modifications which iteratively use interweaving and
interlacing are considered. We show that strength of these ciphers is due to
non-linear transformation used in them (bit-level permutations). Impact of
number of iterations on the avalanche effect is investigated. We propose two
Hill cipher modifications using column swapping and arbitrary permutation with
significantly less computational complexity (2 iterations are used versus 16).
The proposed modifications decrease encryption time while keeping the strength
of the ciphers. Numerical experiments for two proposed ciphers indicate that
they can provide a substantial avalanche effect.
| arxiv topic:cs.CR |
arxiv_dataset-37311209.5936 | The Old New Frontier: Studying the CERN-SPS Energy Range with NA61/SHINE
hep-ex nucl-ex
With the Large Hadron Collider entering its third year of granting us insight
into the highest collision energies to date, one should nevertheless keep in
mind the unexplored physics potential of lower energies. A prime example here
is the NA61/SHINE experiment at the CERN Super Proton Synchrotron. Using its
large-acceptance hadronic spectrometer, SHINE aims to accomplish a number of
physics goals: measuring spectra of identified hadrons in hadron-nucleus
collisions to provide reference for accelerator neutrino experiments and
cosmic-ray observatories, investigating particle properties in the large
transverse-momentum range for hadron+hadron and hadron+nucleus collisions for
studying the nuclear modification factor at SPS energies, and measuring
hadronic observables in a particularly interesting region of the phase diagram
of strongly-interacting matter to study the onset of deconfinement and search
for the critical point of strongly-interacting matter with nucleus-nucleus
collisions. This contribution shall summarise results obtained so far by
NA61/SHINE, as well as present the current status and plans of its experimental
programme.
| arxiv topic:hep-ex nucl-ex |
arxiv_dataset-37321209.6036 | Search for Metal Pollution in 81 DA White Dwarfs
astro-ph.SR
A total of 81 DA white dwarfs have been observed with the Cosmic Origins
Spectrograph on the Hubble Space Telescope in a snapshot program. The targets
were selected to be in the $T_{\rm eff}$ range from 17000 - 25000 K, where
optical metal lines become weak and difficult to detect. Because of the strong
Si, C, and O resonance lines in the UV, this survey has a sensitivity that is
comparable to that of the Keck/VLT searches for CaII K in cooler white dwarfs.
These objects also have no convection zone and thus very short diffusion
timescales, assuring that accretion is currently ongoing. The spectra have high
resolution and in most cases fairly good S/N. About 60% of them show
photospheric metal pollution, predominantly of Si, but in some cases additional
metals are present. We report the results of a preliminary analysis and discuss
the sources of the accreted matter and the possible r\^ole of radiative
levitation.
| arxiv topic:astro-ph.SR |
arxiv_dataset-37331209.6136 | Strongly Interacting Matter at Finite Chemical Potential : Hybrid Model
Approach
hep-ph nucl-th
Search for a proper and realistic equation of state (EOS) for strongly
interacting matter used in the study of the QCD phase diagram still appears as
a challenging problem. Recently, we constructed a hybrid model description for
the quark gluon plasma (QGP) as well as hadron gas (HG) phases where we used an
excluded volume model for HG and a thermodynamically consistent quasiparticle
model for the QGP phase. The hybrid model suitably describes the recent lattice
results of various thermodynamical as well as transport properties of the QCD
matter at zero baryon chemical potential ($\mu_{B}$). In this paper, we extend
our investigations further in obtaining the properties of QCD matter at finite
value of $\mu_{B}$ and compare our results with the most recent results of
lattice QCD calculation.
| arxiv topic:hep-ph nucl-th |
arxiv_dataset-37341209.6236 | T1 theorem on product Carnot-Caratheodory spaces
math.FA
Nagel and Stein established $L^p$-boundedness for a class of singular
integrals of NIS type, that is, non-isotropic smoothing operators of order 0,
on spaces $\widetilde{M}=M_1\times...\times M_n,$ where each factor space $M_i,
1\leq i\leq n,$ is a smooth manifold on which the basic geometry is given by a
control, or Carnot--Carath\'eodory, metric induced by a collection of vector
fields of finite type. In this paper we prove the product $T1$ theorem on
$L^2,$ the Hardy space $H^p(\widetilde{M})$ and the space
$CMO^p(\widetilde{M})$, the dual of $H^p(\widetilde{M}),$ for a class of
product singular integral operators which covers Journ\'e's class and operators
studied by Nagel and Stein.
| arxiv topic:math.FA |
arxiv_dataset-37351209.6336 | Parametricity in an Impredicative Sort
cs.LO
Reynold's abstraction theorem is now a well-established result for a large
class of type systems. We propose here a definition of relational parametricity
and a proof of the abstraction theorem in the Calculus of Inductive
Constructions (CIC), the underlying formal language of Coq, in which
parametricity relations' codomain is the impredicative sort of propositions. To
proceed, we need to refine this calculus by splitting the sort hierarchy to
separate informative terms from non-informative terms. This refinement is very
close to CIC, but with the property that typing judgments can distinguish
informative terms. Among many applications, this natural encoding of
parametricity inside CIC serves both theoretical purposes (proving the
independence of propositions with respect to the logical system) as well as
practical aspirations (proving properties of finite algebraic structures). We
finally discuss how we can simply build, on top of our calculus, a new
reflexive Coq tactic that constructs proof terms by parametricity.
| arxiv topic:cs.LO |
arxiv_dataset-37361209.6436 | Frustration induced disordered magnetism in Ba3RuTi2O9
cond-mat.str-el
The title compound Ba3RuTi2O9 crystallizes with a hexagonal unit cell. It
contains layers of edge shared triangular network of Ru4+ (S=1) ions. Magnetic
susceptibility chi(T) and heat capacity data show no long range magnetic
ordering down to 1.8K. A Curie-Weiss (CW) fitting of chi(T) yields a large
antiferromagnetic CW temperature theta_CW=-166K. However, in low field, a
splitting of zero field cooled (ZFC) and field cooled (FC) chi(T) is observed
below ~30K. Our measurements suggest that Ba3RuTi2O9 is a highly frustrated
system but only a small fraction of the spins in this system undergo a
transition to a frozen magnetic state below ~30K.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-37371209.6536 | Kelvin-Helmholtz instability of kink waves in photospheric twisted flux
tubes
astro-ph.SR
We investigate conditions under which kink magnetohydrodynamic waves
propagating along photospheric uniformly twisted flux tubes with axial mass
flows become unstable as a consequence of the Kelvin-Helmholtz instability. We
employed the dispersion relations of kink waves derived from the linearised
magnetohydrodynamic equations. We assumed real wave numbers and complex angular
wave frequencies, namely complex wave phase velocities. The dispersion
relations were solved numerically at fixed input parameters and several mass
flow velocities. We show that the stability of the waves depends upon four
parameters, the density contrast between the flux tube and its environment, the
ratio of the background magnetic fields in the two media, the twist of the
magnetic field lines inside the tube, and the value of the Alfven-Mach number
(the ratio of the jet velocity to Alfv\'en speed inside the flux tube). At
certain densities and magnetic field twists, an instability of the
Kelvin-Helmholtz type of kink (m = 1) mode can arise if the Alfven-Mach number
exceeds a critical value. The observed mass flows may trigger the
Kelvin-Helmholtz instability of the kink (m = 1) mode in weakly twisted
photospheric magnetic flux tubes at critical Alfven-Mach numbers lower that
those in untwisted tubes if the magnetic field twist lies in the range
0.36--0.4 and the flow speed exceeds a critical value. A weak external magnetic
field (with a ratio to the magnetic field inside the tube in the range
0.1--0.5) slightly increases that critical value.
| arxiv topic:astro-ph.SR |
arxiv_dataset-37381210.0006 | Viscosity Solutions of Fully Nonlinear Parabolic Path Dependent PDEs:
Part I
math.PR
The main objective of this paper and the accompanying one \cite{ETZ2} is to
provide a notion of viscosity solutions for fully nonlinear parabolic
path-dependent PDEs. Our definition extends our previous work \cite{EKTZ},
focused on the semilinear case, and is crucially based on the nonlinear optimal
stopping problem analyzed in \cite{ETZ0}. We prove that our notion of viscosity
solutions is consistent with the corresponding notion of classical solutions,
and satisfies a stability property and a partial comparison result. The latter
is a key step for the wellposedness results established in \cite{ETZ2}. We also
show that the value processes of path-dependent stochastic control problems are
viscosity solutions of the corresponding path dependent dynamic programming
equation.
| arxiv topic:math.PR |
arxiv_dataset-37391210.0106 | Brownian Motion and Quantum Dynamics of Magnetic Monopoles in Spin Ice
cond-mat.other
Spin ice illustrates many unusual magnetic properties, including zero point
entropy, emergent monopoles and a quasi liquid-gas transition. To reveal the
quantum spin dynamics that underpin these phenomena is an experimental
challenge. Here we show how crucial information is contained in the frequency
dependence of the magnetic susceptibility and in its high frequency or
adiabatic limit. These measures indicate that monopole diffusion is strictly
Brownian but is underpinned by spin tunnelling and is influenced by collective
monopole interactions. We also find evidence of driven monopole plasma
oscillations in weak applied field, and unconventional critical behaviour in
strong applied field. Our results resolve contradictions in the present
understanding of spin ice, reveal unexpected physics and establish adiabatic
susceptibility as a revealing characteristic of exotic spin systems.
| arxiv topic:cond-mat.other |
arxiv_dataset-37401210.0206 | Computing symmetry groups of polyhedra
math.CO math.GR math.MG
Knowing the symmetries of a polyhedron can be very useful for the analysis of
its structure as well as for practical polyhedral computations. In this note,
we study symmetry groups preserving the linear, projective and combinatorial
structure of a polyhedron. In each case we give algorithmic methods to compute
the corresponding group and discuss some practical experiences. For practical
purposes the linear symmetry group is the most important, as its computation
can be directly translated into a graph automorphism problem. We indicate how
to compute integral subgroups of the linear symmetry group that are used for
instance in integer linear programming.
| arxiv topic:math.CO math.GR math.MG |
arxiv_dataset-37411210.0306 | Enumerating topological $(n_k)$-configurations
cs.CG math.CO
An $(n_k)$-configuration is a set of $n$ points and $n$ lines in the
projective plane such that their point-line incidence graph is $k$-regular. The
configuration is geometric, topological, or combinatorial depending on whether
lines are considered to be straight lines, pseudolines, or just combinatorial
lines. We provide an algorithm for generating, for given $n$ and $k$, all
topological $(n_k)$-configurations up to combinatorial isomorphism, without
enumerating first all combinatorial $(n_k)$-configurations. We apply this
algorithm to confirm efficiently a former result on topological
$(18_4)$-configurations, from which we obtain a new geometric
$(18_4)$-configuration. Preliminary results on $(19_4)$-configurations are also
briefly reported.
| arxiv topic:cs.CG math.CO |
arxiv_dataset-37421210.0406 | Degree of non-K\"ahlerianity for 6-dimensional nilmanifolds
math.DG
We use Bott-Chern cohomology to measure the non-K\"ahlerianity of
6-dimensional nilmanifolds endowed with the invariant complex structures in M.
Ceballos, A. Otal, L. Ugarte, and R. Villacampa's classification, [Invariant
Complex Structures on 6-Nilmanifolds: Classification, Fr\"olicher Spectral
Sequence and Special Hermitian Metrics, J. Geom. Anal. (2014)]. We investigate
the existence of pluriclosed metric in connection with such a classification.
| arxiv topic:math.DG |
arxiv_dataset-37431210.0506 | A wide-band, active antenna system for long wavelength radio astronomy
astro-ph.IM
We describe an "active" antenna system for HF/VHF (long wavelength) radio
astronomy that has been successfully deployed 256-fold as the first station
(LWA1) of the planned Long Wavelength Array. The antenna system, consisting of
crossed dipoles, an active balun/preamp, a support structure, and a ground
screen has been shown to successfully operate over at least the band from 20
MHz (15 m wavelength) to 80 MHz (3.75 m wavelength) with a noise figure that is
at least 6 dB better than the Galactic background emission noise temperature
over that band. Thus, the goal to design and construct a compact, inexpensive,
rugged, and easily assembled antenna system that can be deployed many-fold to
form numerous large individual "stations" for the purpose of building a large,
long wavelength synthesis array telescope for radio astronomical and
ionospheric observations was met.
| arxiv topic:astro-ph.IM |
arxiv_dataset-37441210.0606 | Small data blow-up for a system of nonlinear Schr\"odinger equations
math.AP
We give examples of small data blow-up for a three-component system of
quadratic nonlinear Schr\"odinger equations in one space dimension. Our
construction of the blowing-up solution is based on the Hopf-Cole
transformation, which allows us to reduce the problem to getting suitable
growth estimates for a solution to the transformed system. Amplification in the
reduced system is shown to have a close connection with the mass resonance.
| arxiv topic:math.AP |
arxiv_dataset-37451210.0706 | Approximate Dynamic Programming based on High Dimensional Model
Representation
math.OC
This article introduces an algorithm for implicit High Dimensional Model
Representation (HDMR) of the Bellman equation. This approximation technique
reduces memory demands of the algorithm considerably. Moreover, we show that
HDMR enables fast approximate minimization which is essential for evaluation of
the Bellman function. In each time step, the problem of parametrized HDMR
minimization is relaxed into trust region problems, all sharing the same
matrix. Finding its eigenvalue decomposition, we effectively achieve estimates
of all minima. Their full-domain representation is avoided by HDMR and then the
same approach is used recursively in the next time step. An illustrative
example of N-armed bandid problem is included. We assume that the newly
established connection between approximate HDMR minimization and the trust
region problem can be beneficial also to many other applications.
| arxiv topic:math.OC |
arxiv_dataset-37461210.0806 | Producing baryons from neutralinos in small H2 clumps over cosmological
ages
astro-ph.CO
Extreme scattering events in quasars suggest the existence of dark $\rm H_2 $
clumps of mass $\rm \sim 10^{-3} M_\odot$ and size $\rm \sim 10 AU$. Such
clumps are extremely dense compared to WIMPs clumps of the same mass obtained
by N-body simulations. A WIMP clump gravitationally attracted by a central $\rm
H_2 $ clump would experience a first infall during which its density increases
by $\rm 10^6$ in $\rm \sim 1 Myr$. In this poster I begin to explore the
phenomenology of mixed clumps made with $\rm H_2 $ and WIMPs. Molecular clouds
built with clumps are efficient machines to transform smooth distributions of
WIMPs into concentrated networks. If WIMPs are neutralinos gravitationally
attracted in clumps of such molecular clouds, they may either enrich the baryon
sector over cosmological ages, or remain mixed with cold $\rm H_2 $ clouds
until the clumps evaporate either by collision or by stellar UV heating. A
phenomenological model based on an hypothetic dark baryonic component (DBC)
that was invoked in the past to explain one of the main drawbacks of CDM
profiles, their overly dense cores, is briefly revisited in this context. The
DBC is replaced by a mix of $\rm H_2 $ and WIMPs, with a small fraction of HI
produced by internal $\rm H_2 $ collisions, in slightly dispersive clumpy
clouds that may migrate from the halo towards inner parts of a galaxy and disk.
| arxiv topic:astro-ph.CO |
arxiv_dataset-37471210.0906 | On the Higgs Fit and Electroweak Phase Transition
hep-ph astro-ph.CO hep-ex
We consider the Higgs portal through which light scalars contribute both to
the Higgs production and decay and Higgs effective potential at finite
temperature via quantum loops. The positive Higgs portal coupling required by a
strongly first order electroweak phase transition is disfavored by the current
Higgs data if we consider one such scalar. We observe that by introducing a
second scalar with negative Higgs portal coupling, one can not only improve the
Higgs fits, but also enhance the strength of first order EWPT. We apply this
mechanism to the light stop scenario for electroweak baryogenesis in the MSSM
and find a light sbottom could play the role as the second scalar, which allows
the stop to be relatively heavier. Non-decoupled effects on the Higgs or
sbottom self-interactions from physics beyond MSSM is found to be indispensable
for this scenario to work. A clear prediction from the picture is the existence
of a light sbottom (below 200 GeV) and a light stop (can be as heavy as 140
GeV), which can be directly tested in the near future.
| arxiv topic:hep-ph astro-ph.CO hep-ex |
arxiv_dataset-37481210.1006 | QCD Evolutions of Twist-3 Chirality-Odd Operators
hep-ph
We study the scale dependence of twist-3 distributions defined with
chirality-odd quark-gluon operators. To derive the scale dependence we
explicitly calculate these distributions of multi-parton states instead of a
hadron. Taking one-loop corrections into account we obtain the leading
evolution kernel in the most general case. In some special cases the evolutions
are simplified. We observe that the obtained kernel in general does not get
simplified in the large-$N_c$ limit in contrast to the case of those twist-3
distributions defined only with chirality-odd quark operators. In the later,
the simplification is significant.
| arxiv topic:hep-ph |
arxiv_dataset-37491210.1106 | Form factor and width of a quantum string
hep-lat
In the Yang-Mills theory, the apparent thickness of the confining string is
known to grow logarithmically when its length increases. The same logarithmic
broadening also happens to strings in other quantum field theories and domain
walls in statistical physics models. Even in quantum field theories, the
correlators used to measure and characterise this phenomenon are analogous to
those in statistical physics. In this paper we describe it using the string
form factor which is a meaningful quantum observable, obtainable in principle
from scattering experiments. We show how the form factor can be obtained from
field correlation functions calculated in lattice Monte Carlo simulations. We
apply this method to 2+1-dimensional scalar theory in the strong coupling
limit, where it is equivalent to the 3D Ising model, and through duality also
to 2+1-dimensional $\mathbb{Z}_2$ gauge theory. We measure the string form
factor by simulating the Ising model, and demonstrate that it displays the same
logarithmic broadening as observed by other quantities.
| arxiv topic:hep-lat |
arxiv_dataset-37501210.1206 | Weighted convolution inequalities for radial functions
math.CA
We obtain convolution inequalities in Lebesgue and Lorentz spaces with power
weights when the functions involved are assumed to be radially symmetric. We
also present applications of these results to inequalities for Riesz potentials
of radial functions in weighted Lorentz spaces and embedding theorems for
radial Besov spaces with power weights.
| arxiv topic:math.CA |
arxiv_dataset-37511210.1306 | On the possibility of a measurement of the CP Majorana phase in the
0\nu\beta\beta-decay
hep-ph
In view of recent measurements of the mixing angle \theta_{13} a possibility
to determine the difference of two CP Majorana phases of the neutrino mixing
matrix from the study of neutrinoless double-beta decay is investigated. We
show that in the case of the inverted hierarchy of neutrino masses it might be
possible if neutrinoless double-beta decay will be observed. The required
experimental accuracies and uncertainty in the calculated nuclear matrix
elements of the process are discussed.
| arxiv topic:hep-ph |
arxiv_dataset-37521210.1406 | Relativistic new Yukawa-like potential and tensor coupling
nucl-th math-ph math.MP
We approximately solve the Dirac equation for a new suggested generalized
inversely quadratic Yukawa (GIQY) potential including a Coulomb-like tensor
interaction with arbitrary spin-orbit coupling quantum number In the framework
of the spin and pseudospin (p-spin) symmetry, we obtain the energy eigenvalue
equation and the corresponding eigenfunctions, in closed form, by using the
parametric Nikiforov-Uvarov (NU) method. The numerical results show that the
Coulomb-like tensor interaction, removes degeneracies between spin and p-spin
state doublets. The Dirac solutions in the presence of exact spin symmetry are
reduced to Schr\"odinger solutions for Yukawa and inversely quadratic Yukawa
potentials.
| arxiv topic:nucl-th math-ph math.MP |
arxiv_dataset-37531210.1506 | New spinorial particle model in tensorial space-time and interacting
higher spin fields
hep-th math-ph math.MP
The Maxwell-covariant particle model is formulated in tensorial extended D=4
space-time (x_mu, z_{mu nu}) parametrized by ten-dimensional coset of D=4
Maxwell group, with added auxiliary Weyl spinors lambda_alpha, y^alpha. We
provide the Hamiltonian quantization of the model and demonstrate that first
class constraints modify the known equations obtained for massless higher spin
fields in flat tensorial space-time. We obtain the Maxwell-covariant field
equations for new infinite dimensional spin multiplets. The component fields
assigned to different spin values are linked by couplings proportional to
rescaled electromagnetic coupling constant \tilde e = em, where m is the
mass-like parameter introduced in our model. We discuss briefly the geometry of
our tensorial space-time with constant torsion and its relation with the
presence of constant electromagnetic background.
| arxiv topic:hep-th math-ph math.MP |
arxiv_dataset-37541210.1606 | Geons and Spin-2 Condensates in the AdS Soliton
hep-th
We construct geons starting with gravitational perturbations of the AdS
soliton. Previous studies of a charged scalar field in the soliton background
showed a holographic insulator/superconductor transition at a critical chemical
potential. We explore the possibility that dimensional reduction of the geon
could model a transition to a d-wave superconductor. We find that although one
does get a charged spin-2 condensate, it has higher free energy than the state
without the condensate, so there is no phase transition.
| arxiv topic:hep-th |
arxiv_dataset-37551210.1706 | Optical and radio properties of giant radio quasars: Central black hole
characteristics
astro-ph.CO
We analysed the optical and radio properties of lobe-dominated giant-sized (>
0.72 Mpc) radio quasars and compared the results with those derived for a
sample of smaller radio sources to determine whether the large size of some
extragalactic radio sources is related to the properties of their nuclei. We
compiled the largest (to date) sample of giant radio quasars, including 24 new
and 21 previously-known objects, and calculated a number of important
parameters of their nuclei such as the black hole mass and the accretion rate.
We conclude that giant radio quasars have properties similar to those of
smaller size and that giant quasars do not have more powerful central engines
than other radio quasars. The results obtained are consistent with evolutionary
models of extragalactic radio sources which predict that giant radio quasars
could be more evolved (aged) sources compared to smaller radio quasars. In
addition we found out that the environment may play only a minor role in
formation of large-scale radio structures.
| arxiv topic:astro-ph.CO |
arxiv_dataset-37561210.1806 | Interparticle correlations in the production of J/\psi pairs in
proton-proton collisions
hep-ph
We focus on the problem of disentangling the single (SPS) and double (DPS)
parton scattering modes in the production of \J pairs at the LHC conditions.
Our analysis is based on comparing the shapes of the differential cross
sections and on studying their behavior under imposing kinematical cuts. On the
SPS side, we consider the leading-order ${\cal O}(\alpha_s^4)$ contribution
with radiative corrections (taken into account in the framework of the \ktf
approach) and the subleading ${\cal O}(\alpha_s^6)$ contribution from \pd
~gluon-gluon scattering represented by one gluon exchange and two gluon
exchange mechanisms. We come to the conclusion that disentangling the SPS and
DPS modes is rather difficult on the basis of azimuthal correlations, while the
rapidity difference looks more promising, provided the acceptance of the
experimental detectors has enough rapidity range.
| arxiv topic:hep-ph |
arxiv_dataset-37571210.1906 | Resummation of jet-veto logarithms in hadronic processes containing jets
hep-ph hep-ex
We derive a factorization theorem for production of an arbitrary number of
color-singlet particles accompanied by a fixed number of jets at the LHC. The
jets are defined with the standard anti-$k_T$ algorithm, and the fixed number
of jets is obtained by imposing a veto on additional radiation in the final
state. The formalism presented here is useful for current Higgs boson analyses
using exclusive jet bins, and for other studies using a similar strategy. The
derivation uses the soft-collinear effective theory and assumes that the
transverse momenta of the hard jets are larger than the veto scale. We resum
the large Sudakov logarithms $\alpha_s^n \log^{2n-m}(p_T^{J}/p_T^{veto})$ up to
the next-to-leading-logarithmic accuracy, and present numerical results for
Higgs boson production in association with a jet at the LHC. We comment on the
experimentally-interesting parameter region in which we expect our
factorization formula to hold.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-37581210.2006 | Three s-wave interacting fermions under anisotropic harmonic
confinement: Dimensional crossover of energetics and virial coefficients
cond-mat.quant-gas
We present essentially exact solutions of the Schroedinger equation for three
fermions in two different spin states with zero-range s-wave interactions under
harmonic confinement. Our approach covers spherically symmetric, strictly
two-dimensional, strictly one-dimensional, cigar-shaped, and pancake-shaped
traps. In particular, we discuss the transition from quasi-one-dimensional to
strictly one-dimensional and from quasi-two-dimensional to strictly
two-dimensional geometries. We determine and interpret the eigenenergies of the
system as a function of the trap geometry and the strength of the zero-range
interactions. The eigenenergies are used to investigate the dependence of the
second- and third-order virial coefficients, which play an important role in
the virial expansion of the thermodynamic potential, on the geometry of the
trap. We show that the second- and third-order virial coefficients for
anisotropic confinement geometries are, for experimentally relevant
temperatures, very well approximated by those for the spherically symmetric
confinement for all s-wave scattering lengths.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-37591210.2106 | The Laplace transform, mirror symmetry, and the topological recursion of
Eynard-Orantin
math.QA math-ph math.MP
This paper is based on the author's talk at the 2012 Workshop on Geometric
Methods in Physics held in Bialowieza, Poland. The aim of the talk is to
introduce the audience to the Eynard-Orantin topological recursion. The
formalism is originated in random matrix theory. It has been predicted, and in
some cases it has been proven, that the theory provides an effective mechanism
to calculate certain quantum invariants and a solution to enumerative geometry
problems, such as open Gromov-Witten invariants of toric Calabi-Yau threefolds,
single and double Hurwitz numbers, the number of lattice points on the moduli
space of smooth algebraic curves, and quantum knot invariants. In this paper we
use the Laplace transform of generalized Catalan numbers of an arbitrary genus
as an example, and present the Eynard-Orantin recursion. We examine various
aspects of the theory, such as its relations to mirror symmetry, Gromov-Witten
invariants, integrable hierarchies such as the KP equations, and the
Schroedinger equations.
| arxiv topic:math.QA math-ph math.MP |
arxiv_dataset-37601210.2206 | Disentangling the NIR/optical emission of the black hole XTE J1650-500
during outburst
astro-ph.HE
While the sources of X-ray and radio emission in the different states of
low-mass X-ray binaries are relatively well understood, the origin of the
near-infrared (NIR) and optical emission is more often debated. It is likely
that the NIR/optical flux originates from an amalgam of different emission
regions, because it occurs at the intersecting wavelengths of multiple
processes. We aim to identify the NIR/optical emission region(s) of one such
low-mass X-ray binary and black hole candidate, XTE J1650-500, via photometric,
timing, and spectral analyses. We present unique NIR/optical images and
spectra, obtained with the ESO-New Technology Telescope, during the peak of the
2001 outburst of XTE J1650-500. The data suggest that the NIR/optical flux is
due to a combination of emission mechanisms including a significant
contribution from X-ray reprocessing and, at early times in the hard state, a
relativistic jet that is NIR/radio dim compared to similar sources.The jet of
XTE J1650-500 is relatively weak compared to that of other black hole low-mass
X-ray binaries, possibly because we observe as it is being "turned off" or
quenched at the state transition. While there are several outliers to the
radio--X-ray correlation of the hard state of low-mass X-ray binaries, XTE
J1650-500 is the first example of an outlier to the NIR/optical--X-ray
correlation.
| arxiv topic:astro-ph.HE |
arxiv_dataset-37611210.2306 | Bi-photon propagation control with optimized wavefront by means of
Adaptive Optics
quant-ph physics.optics
We present an efficient method to control the spatial modes of entangled
photons produced through SPDC process. Bi-photon beam propagation is controlled
by a deformable mirror, that shapes a 404nm CW diode laser pump interacting
with a nonlinear BBO type-I crystal. Thanks to adaptive optical system, the
propagation of 808nm SPDC light produced is optimized over a distance of 2m.
The whole system optimization is carried out by a feedback between deformable
mirror action and entangled photon coincidence counts. We also demonstrated the
improvement of the two-photon coupling into single mode fibers.
| arxiv topic:quant-ph physics.optics |
arxiv_dataset-37621210.2406 | Quick Search for Rare Events
cs.IT math.IT
Rare events can potentially occur in many applications. When manifested as
opportunities to be exploited, risks to be ameliorated, or certain features to
be extracted, such events become of paramount significance. Due to their
sporadic nature, the information-bearing signals associated with rare events
often lie in a large set of irrelevant signals and are not easily accessible.
This paper provides a statistical framework for detecting such events so that
an optimal balance between detection reliability and agility, as two opposing
performance measures, is established. The core component of this framework is a
sampling procedure that adaptively and quickly focuses the
information-gathering resources on the segments of the dataset that bear the
information pertinent to the rare events. Particular focus is placed on
Gaussian signals with the aim of detecting signals with rare mean and variance
values.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-37631210.2506 | Enabling Reusability in Agile Software Development
cs.SE
Software Engineering Discipline is constantly achieving momentum from past
two decades. In last decade, remarkable progress has been observed. New process
models that are introduced from time to time in order to keep pace with
multidimensional demands of the industry. New software development paradigms
are finding its place in industry such as Agile Software Development, Reuse
based Development and Component based Development. But different software
development models fail to satisfy many needs of software industry. As aim of
all the process models is same, i.e., to get quality product, reduce time of
development, productivity improvement and reduction in cost. Still, no single
process model is complete in itself. Software industry is moving towards Agile
Software Development. Agile development does not obviously fit well for
building reusable artifacts. However, with careful attention, and important
modifications made to agile processes, it may be possible to successfully adapt
and put on agile methods to development of reusable objects. The model being
proposed here combines the features of Agile Software Development and
reusability.
| arxiv topic:cs.SE |
arxiv_dataset-37641210.2606 | Polarized Neutron Laue Diffraction on a Crystal Containing Dynamically
Polarized Proton Spins
cond-mat.mtrl-sci
We report on a polarized-neutron Laue diffraction experiment on a single
crystal of neodynium doped lanthanum magnesium nitrate hydrate containing
polarized proton spins. By using dynamic nuclear polarization to polarize the
proton spins, we demonstrate that the intensities of the Bragg peaks can be
enhanced or diminished significantly, whilst the incoherent background, due to
proton spin disorder, is reduced. It follows that the method offers unique
possibilities to tune continuously the contrast of the Bragg reflections and
thereby represents a new tool for increasing substantially the signal-to-noise
ratio in neutron diffraction patterns of hydrogenous matter.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-37651210.2706 | Optimality Gap of Asymptotically-derived Prescriptions with Applications
to Queueing Systems
math.PR math.OC
In complex systems, it is quite common to resort to approximations when
optimizing system performance. These approximations typically involve selecting
a particular system parameter and then studying the performance of the system
as this parameter grows without bound. In such an asymptotic regime, we prove
that if the approximation to the objective function is accurate up to
$\mathcal{O}(1)$, then under some regularity conditions, the prescriptions that
are derived from this approximation are $o(1)$-optimal, i.e., their optimality
gap is asymptotically zero. A consequence of this result is that the well-known
square-root staffing rules for capacity sizing in $M/M/s$ and $M/M/s+M$ queues
to minimize the sum of linear expected steady-state customer waiting costs and
linear capacity costs are $o(1)$-optimal. We also discuss extensions of this
result for the case of non-linear customer waiting costs in these systems.
| arxiv topic:math.PR math.OC |
arxiv_dataset-37661210.2806 | Risk-Sensitive Mean Field Games
math.OC cs.GT cs.SY
In this paper, we study a class of risk-sensitive mean-field stochastic
differential games. We show that under appropriate regularity conditions, the
mean-field value of the stochastic differential game with exponentiated
integral cost functional coincides with the value function described by a
Hamilton-Jacobi-Bellman (HJB) equation with an additional quadratic term. We
provide an explicit solution of the mean-field best response when the
instantaneous cost functions are log-quadratic and the state dynamics are
affine in the control. An equivalent mean-field risk-neutral problem is
formulated and the corresponding mean-field equilibria are characterized in
terms of backward-forward macroscopic McKean-Vlasov equations,
Fokker-Planck-Kolmogorov equations, and HJB equations. We provide numerical
examples on the mean field behavior to illustrate both linear and McKean-Vlasov
dynamics.
| arxiv topic:math.OC cs.GT cs.SY |
arxiv_dataset-37671210.2906 | Scheduling Resources for Executing a Partial Set of Jobs
cs.DS
In this paper, we consider the problem of choosing a minimum cost set of
resources for executing a specified set of jobs. Each input job is an interval,
determined by its start-time and end-time. Each resource is also an interval
determined by its start-time and end-time; moreover, every resource has a
capacity and a cost associated with it. We consider two versions of this
problem. In the partial covering version, we are also given as input a number
k, specifying the number of jobs that must be performed. The goal is to choose
k jobs and find a minimum cost set of resources to perform the chosen k jobs
(at any point of time the capacity of the chosen set of resources should be
sufficient to execute the jobs active at that time). We present an O(log
n)-factor approximation algorithm for this problem.
We also consider the prize collecting version, wherein every job also has a
penalty associated with it. The feasible solution consists of a subset of the
jobs, and a set of resources, to perform the chosen subset of jobs. The goal is
to find a feasible solution that minimizes the sum of the costs of the selected
resources and the penalties of the jobs that are not selected. We present a
constant factor approximation algorithm for this problem
| arxiv topic:cs.DS |
arxiv_dataset-37681210.3006 | Spectral curves and the Schroedinger equations for the Eynard-Orantin
recursion
math-ph hep-th math.MP math.QA
It is predicted that the principal specialization of the partition function
of a B-model topological string theory, that is mirror dual to an A-model
enumerative geometry problem, satisfies a Schroedinger equation, and that the
characteristic variety of the Schroedinger operator gives the spectral curve of
the B-model theory, when an algebraic K-theory obstruction vanishes. In this
paper we present two concrete mathematical A-model examples whose mirror dual
partners exhibit these predicted features on the B-model side. The A-model
examples we discuss are the generalized Catalan numbers of an arbitrary genus
and the single Hurwitz numbers. In each case, we show that the Laplace
transform of the counting functions satisfies the Eynard-Orantin topological
recursion, that the B-model partition function satisfies the KP equations, and
that the principal specialization of the partition function satisfies a
Schroedinger equation whose total symbol is exactly the Lagrangian immersion of
the spectral curve of the Eynard-Orantin theory.
| arxiv topic:math-ph hep-th math.MP math.QA |
arxiv_dataset-37691210.3106 | Effect of bubble deformability on the vertical channel bubbly flow
physics.flu-dyn
This article describes the fluid dynamics video: "Effect of bubble
deformability on the vertical channel bubbly flow". The effect of bubble
deformability on the flow rate of bubbly upflow in a turbulent vertical channel
is examined using direct numerical simulations. A series of simulations with
bubbles of decreasing deformability reveals a sharp transition from a flow with
deformable bubbles uniformly distributed in the middle of the channel to a flow
with nearly spherical bubbles with a wall-peak bubble distribution and a much
lower flow rate.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-37701210.3206 | Diabatic quantum gates
quant-ph
At present, several models for quantum computation have been proposed.
Adiabatic quantum computation scheme particularly offers this possibility and
is based on a slow enough time evolution of the system, where no transitions
take place. In this work, a new strategy for quantum computation is provided
from the opposite point of view. The objective is to control the non-adiabatic
transitions between some states in order to produce the desired exit states
after the evolution. The model is introduced by means of an analogy between the
adiabatic quantum computation and an inelastic atomic collision. By means of a
simple two-state model, several quantum gates are reproduced, concluding the
possibility of diabatic universal fault-tolerant quantum computation. Going a
step further, a new quantum diabatic computation model is glimpsed, where a
carefully chosen Hamiltonian could carry out a non-adiabatic transition between
the initial and the sought final state.
| arxiv topic:quant-ph |
arxiv_dataset-37711210.3306 | Gravitational anomalies and entropy
gr-qc hep-th
A derivation of entropy from the expressions for two dimensional gravitation
anomalies is given. Starting from the near horizon anomalous energy-momentum
tensors corresponding to particular anomalies, the Virasoro algebra with
central extension is obtained. The central charge is identified by comparing
with the standard form of the algebra. Then the conserved charge in the ground
state is computed. Finally, using the Cardy formula the entropy is obtained.
Here both the vector and chiral theories are discussed.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-37721210.3406 | Estimation of solar illumination time on the earth by an analytical
model: a fertile scenery for to teach physics
astro-ph.EP
We proposed an analytical model for the calculus of illumination time of the
Earth for any time of year and any latitude, this model assumes the obliquity
of the ecliptic as constant, the light beams as parallels, the Earth as
spherical, the movement of translation of Earth as uniform circular, also this
model showed a context of the astronomy whereby the teachers can teach the
basic physics.It was built through a relationship between the movement of
translation and of rotation of the wave front light, then we found the of
illumination zone on the Earth and the illumination time is estimated in a
particular latitude with the uniform circular movement of Earth. Present model
was confronted with the numerical results of the Geoscience Australia Agency
and it is found a maxim perceptual error of 1,6%, this value was assigned
primarily to the difference between the circular trajectory, in this model, and
the elliptical trajectory that is the real. Without the use of spherical
trigonometry was obtained an analytical model that estimates very close the
solar illumination time at any time of year and any latitude on earth, the
model provides an authentic context for studying basic aspects of physics.
| arxiv topic:astro-ph.EP |
arxiv_dataset-37731210.3506 | The 3D structure of turbulent channels up to $\mathrm{Re}_\tau=4000$
physics.flu-dyn
Several time-resolved fluid dynamics videos of turbulent channels from
$\mathrm{Re}_\tau=180$ to $\mathrm{Re}_\tau=4000$ are presented. The videos
show the temporal evolution of sweeps (bluish) and ejections (reddish) in one
half of the channel (only the bottom wall is shown). The color changes from
dark for points close to the wall, to bright for those reaching the center of
the channel. As the Reynolds number increases the scale separation becomes more
clear and the complexity of the dynamics observed rises.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-37741210.3606 | Superconducting LaAlO3/SrTiO3 Nanowires
cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.supr-con
We report superconductivity in quasi-1D nanostructures created at the
LaAlO3/SrTiO3 interface. Nanostructures having line widths w~10 nm are formed
from the parent two-dimensional electron liquid using conductive atomic force
microscope lithography. Nanowire cross-sections are small compared to the
superconducting coherence length in LaAlO3/SrTiO3 (w<<xi~100 nm), placing them
in the quasi-1D regime. Broad superconducting transitions with temperature and
finite resistances in the superconducting state well below Tc~200 mK are
observed. V-I curves show switching between the superconducting and normal
states that are characteristic of superconducting nanowires. The four-terminal
resistance in the superconducting state shows an unusual dependence on the
current path, varying by as much as an order of magnitude.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.supr-con |
arxiv_dataset-37751210.3706 | Promising ferrimagnetic double perovskite oxides towards high spin
polarization at high temperature
cond-mat.mtrl-sci
We predict through our first-principles calculations that four double
perovskite oxides of Bi2ABO6 (AB = FeMo, MnMo, MnOs, CrOs) are half-metallic
ferrimagnets. Our calculated results shows that the four optimized structures
have negative formation energy, from -0.42 to -0.26 eV per formula unit, which
implies that they could probably be realized. In the case of Bi2FeMoO6, the
half-metallic gap and Curie temperature are predicted to reach to 0.71 eV and
650 K, respectively, which indicates that high spin polarization could be kept
at high temperatures far beyond room temperature. It is believed that some of
them could be synthesized soon and would prove useful for spintronic
applications.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-37761210.3806 | Thickness-dependent polarization of strained BiFeO3 films with constant
tetragonality
cond-mat.mtrl-sci
We measure the remnant polarization of ferroelectric domains in BiFeO3 films
down to 3.6 nm using low energy electron and photoelectron emission microscopy.
The measured polarization decays strongly below a critical thickness of 5-7 nm
predicted by continuous medium theory whereas the tetragonal distortion does
not change. We resolve this apparent contradiction using first-principles-based
effective Hamiltonian calculations. In ultra thin films the energetics of near
open circuit electrical boundary conditions, i.e. unscreened depolarizing
field, drive the system through a phase transition from single out-of-plane
polarization to a nanoscale stripe domains, giving rise to an average remnant
polarization close to zero as measured by the electron microscopy whilst
maintaining the relatively large tetragonal distortion imposed by the non-zero
polarization state of each individual domain.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-37771210.3906 | Design of Multiple-Edge Protographs for QC LDPC Codes Avoiding Short
Inevitable Cycles
cs.IT math.IT
There have been lots of efforts on the construction of quasi-cyclic (QC)
low-density parity-check (LDPC) codes with large girth. However, most of them
are focused on protographs with single edges and little research has been done
for the construction of QC LDPC codes lifted from protographs with multiple
edges. Compared to single-edge protographs, multiple-edge protographs have
benefits such that QC LDPC codes lifted from them can potentially have larger
minimum Hamming distance. In this paper, all subgraph patterns of multiple-edge
protographs, which prevent QC LDPC codes from having large girth by inducing
inevitable cycles, are fully investigated based on graph-theoretic approach. By
using combinatorial designs, a systematic construction method of multiple-edge
protographs is proposed for regular QC LDPC codes with girth at least 12 and
also other method is proposed for regular QC LDPC codes with girth at least 14.
A construction algorithm of QC LDPC codes by lifting multiple-edge protographs
is proposed and it is shown that the resulting QC LDPC codes have larger upper
bounds on the minimum Hamming distance than those lifted from single-edge
protographs. Simulation results are provided to compare the performance of the
proposed QC LDPC codes, the progressive edge-growth (PEG) LDPC codes, and the
PEG QC LDPC codes.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-37781210.4006 | The Perturbed Variation
cs.LG stat.ML
We introduce a new discrepancy score between two distributions that gives an
indication on their similarity. While much research has been done to determine
if two samples come from exactly the same distribution, much less research
considered the problem of determining if two finite samples come from similar
distributions. The new score gives an intuitive interpretation of similarity;
it optimally perturbs the distributions so that they best fit each other. The
score is defined between distributions, and can be efficiently estimated from
samples. We provide convergence bounds of the estimated score, and develop
hypothesis testing procedures that test if two data sets come from similar
distributions. The statistical power of this procedures is presented in
simulations. We also compare the score's capacity to detect similarity with
that of other known measures on real data.
| arxiv topic:cs.LG stat.ML |
arxiv_dataset-37791210.4106 | Non-Gaussianity in the Cosmic Microwave Background Induced by Dipolar
Dark Matter
gr-qc astro-ph.CO
In previous work [L. Blanchet and A. Le Tiec, Phys. Rev. D 80, 023524
(2009)], motivated by the phenomenology of dark matter at galactic scales, a
model of dipolar dark matter (DDM) was introduced. At linear order in
cosmological perturbations, the dynamics of the DDM was shown to be identical
to that of standard cold dark matter (CDM). In this paper, the DDM model is
investigated at second order in cosmological perturbation theory. We find that
the internal energy of the DDM fluid modifies the curvature perturbation
generated by CDM with a term quadratic in the dipole field. This correction
induces a new type of non-Gaussianity in the bispectrum of the curvature
perturbation with respect to standard CDM. Leaving unspecified the primordial
amplitude of the dipole field, which could in principle be determined by a more
fundamental description of DDM, we find that, in contrast with usual models of
primordial non-Gaussianities, the non-Gaussianity induced by DDM increases with
time after the radiation-matter equality on super-Hubble scales. This
distinctive feature of the DDM model, as compared with standard CDM, could thus
provide a specific signature in the CMB and large-scale structure probes of
non-Gaussianity.
| arxiv topic:gr-qc astro-ph.CO |
arxiv_dataset-37801210.4206 | Pseudogap and zero-bias anomaly due to fluctuation suppression of
quasiparticle tunneling
cond-mat.supr-con
We study the effect of superconducting fluctuations on the tunnel
current-voltage characteristics of disordered superconducting films placed in a
perpendicular magnetic field, $H$, in the whole $H$-$T$ phase diagram outside
the superconducting region. This tunnel-current is experimentally accessible by
STM measurements. In the domain of temperatures $T\geq T_{c0}$ and relatively
weak fields $H\ll H_{c2}(0)$ we reproduce existing results for the zero-voltage
tunneling conductance, but also discover an important nonlinear contribution,
which appears due to dynamic fluctuation modes and results in the formation of
a strong zero-bias anomaly (ZBA) on the scale $eV\sim
k_{\mathrm{B}}(T-T_{c0})$. At large voltages ($eV\sim k_{\mathrm{B}}T_{c0}$)
these modes, together with the contribution from static fluctuations, form a
pseudogap maximum. At low temperatures, with magnetic field values near
$H_{c2}(0)$, fluctuations acquire quantum character and the general picture of
the voltage dependent tunneling conductance resembles that one close to
$T_{c0}$, where the role of temperature and magnetic field are exchanged. In
particular, a gap-like structure appears with maximum at $eV_{\max}\sim
\Delta_{\mathrm{BCS}}$ and a sharp ZBA on the scale $eV\sim
\Delta_{\mathrm{BCS}}(H/H_{c2}(0)-1)$. The complete expression for the
tunneling current at arbitrary fields and temperatures can be evaluated only
numerically, which is presented in detail.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-37811210.4306 | Giant spin torque in systems with anisotropic exchange interaction
cond-mat.mes-hall
Control of magnetic domain wall movement by the spin-polarized current looks
promising for creation of a new generation of magnetic memory devices. A
necessary condition for this is the domain wall shift by a low-density current.
Here I show that a strongly anisotropic exchange interaction between mobile
heavy holes and localized magnetic moments enormously increases the
current-induced torque on the domain wall as compared to systems with isotropic
exchange. This enables one to control the domain wall motion by current density
10^4 A/cm^2 in ferromagnet/semiconductor hybrids. The experimental observation
of the anisotropic torque will facilitate the integration of ferromagnetism
into semiconductor electronics
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-37821210.4406 | A Classical Framework for Nonlocality and Entanglement
quant-ph physics.class-ph
Based on our model of quantum systems as emerging from the coupled dynamics
between oscillating "bouncers" and the space-filling zero-point field, a
sub-quantum account of nonlocal correlations is given. This is explicitly done
for the example of the "double two-slit" variant of two-particle
interferometry. However, it is also shown that the entanglement in two-particle
interferometry is only a natural consequence of the fact that already a
"single" two-slit experiment can be described on a sub-quantum level with the
aid of "entangling currents" of a generally nonlocal nature.
| arxiv topic:quant-ph physics.class-ph |
arxiv_dataset-37831210.4506 | Spin-flip transitions induced by time-dependent electric fields in
surfaces with strong spin-orbit interaction
cond-mat.mes-hall cond-mat.mtrl-sci
We present a comprehensive theoretical investigation of the light absorption
rate at the Pb/Ge(111) surface with strong spin-orbit coupling. Our
calculations show that electron spin-flip transitions cause as much as 6% of
the total light absorption, representing one order of magnitude enhancement
over Rashba-like systems. Thus, it is demonstrated that a substantial part of
the light irradiating this nominally non-magnetic surface is attenuated in spin
flip processes. Remarkably, the spin-flip transition probability is structured
in well defined hot spots within the Brillouin zone where the electron spin
experiences a sudden 90 degree rotation. This mechanism offers the possibility
of an experimental approach to the spin-orbit phenomena by optical means.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-37841210.4606 | The Tetrahedral Property and a new Gromov-Hausdorff Compactness Theorem
math.DG math.MG
We present the Tetrahedral Compactness Theorem which states that sequences of
Riemannian manifolds with a uniform upper bound on volume and diameter that
satisfy a uniform tetrahedral property have a subsequence which converges in
the Gromov-Hausdorff sense to a countably $\mathcal{H}^m$ rectifiable metric
space of the same dimension. The tetrahedral property depends only on distances
between points in spheres, yet we show it provides a lower bound on the volumes
of balls. The proof is based upon intrinsic flat convergence and a new notion
called the sliced filling volume of a ball.
| arxiv topic:math.DG math.MG |
arxiv_dataset-37851210.4706 | Analytical methods of asymmetry double sine-Gordon equation in infinite
one-dimensional system
math-ph math.MP
Traditionally, Double Sine-Gordon Equation (DSGE) is seen as a nonintegrable
equation. That means we cannot find general solutions in asymmetry DSGE. In
this paper, we develop analytical method to solve this equation by Mobius
transformation. And finally, this can reduce the problem to find roots of
polynomial of four degree in one element. We have known this can be solved by
square formally because its degree less than five. Although complexity as a
solution, but in this sense, we can say we formally solve this nonintegrable
equation.
| arxiv topic:math-ph math.MP |
arxiv_dataset-37861210.4806 | The field of definition of affine invariant submanifolds of the moduli
space of abelian differentials
math.DS
The field of definition of an affine invariant submanifold M is the smallest
subfield of the reals such that M can be defined in local period coordinates by
linear equations with coefficients in this field. We show that the field of
definition is equal to the intersection of the holonomy fields of translation
surfaces in M, and is a real number field of degree at most the genus. We show
that the projection of the tangent bundle of M to absolute cohomology H^1 is
simple, and give a direct sum decomposition of H^1. Applications include
explicit full measure sets of translation surfaces whose orbit closures are as
large as possible, and evidence for finiteness of algebraically primitive
Teichm\"uller curves. The proofs use recent results of Artur Avila, Alex Eskin,
Maryam Mirzakhani, Amir Mohammadi, and Martin M\"oller.
| arxiv topic:math.DS |
arxiv_dataset-37871210.4906 | Efficient MRF Energy Minimization via Adaptive Diminishing Smoothing
cs.AI cs.DS
We consider the linear programming relaxation of an energy minimization
problem for Markov Random Fields. The dual objective of this problem can be
treated as a concave and unconstrained, but non-smooth function. The idea of
smoothing the objective prior to optimization was recently proposed in a series
of papers. Some of them suggested the idea to decrease the amount of smoothing
(so called temperature) while getting closer to the optimum. However, no
theoretical substantiation was provided. We propose an adaptive smoothing
diminishing algorithm based on the duality gap between relaxed primal and dual
objectives and demonstrate the efficiency of our approach with a smoothed
version of Sequential Tree-Reweighted Message Passing (TRW-S) algorithm. The
strategy is applicable to other algorithms as well, avoids adhoc tuning of the
smoothing during iterations, and provably guarantees convergence to the
optimum.
| arxiv topic:cs.AI cs.DS |
arxiv_dataset-37881210.5006 | Modeling the Accretion Structure of AU Mon
astro-ph.SR
AU Mon is a long-period (11.113 d) Algol-type binary system with a persistent
accretion disk that is apparent as double-peaked H-alpha emission. We present
previously unpublished optical spectra of AU Mon which were obtained over
several years with dense orbital phase coverage. We utilize these data, along
with archival UV spectra, to model the temperature and structure of the
accretion disk and the gas stream. Synthetic spectral profiles for lines
including H-alpha, H-beta, and the Al III and Si IV doublets were computed with
the Shellspec program. The best match between the model spectra and the
observations is obtained for an accretion disk of inner/outer radius 5.1/23
R_sun, thickness of 5.2 R_sun, density of 1.0e-13 g/cm^3, and maximum
temperature of 14000 K, along with a gas stream at a temperature of ~8000 K
transferring ~2.4e-9 M_sun/yr. We show H-alpha Doppler tomograms of the
velocity structure of the gas, constructed from difference profiles calculated
through sequentially subtracting contributions from the stars and accretion
structures. The tomograms provide independent support for the Shellspec
modeling, while also illustrating that residual emission at sub-Keplerian
velocities persists even after subtracting the disk and stream emission.
Spectral variability in the H-alpha profile beyond that expected from either
the orbital or the long-period cycle is present on both multi-week and
multi-year timescales, and may reflect quasi-random changes in the mass
transfer rate or the disk structure. Finally, a transient UV spectral
absorption feature may be modeled as an occasional outflow launched from the
vicinity of the disk-stream interaction region.
| arxiv topic:astro-ph.SR |
arxiv_dataset-37891210.5106 | Stabilization of carbon nanotubes by filling with inner tubes: An
optical spectroscopy study on double-walled carbon nanotubes under
hydrostatic pressure
cond-mat.mes-hall cond-mat.mtrl-sci
The stabilization of carbon nanotubes via the filling with inner tubes is
demonstrated by probing the optical transitions in double-walled carbon
nanotube bundles under hydrostatic pressure with optical spectroscopy.
Double-walled carbon nanotube films were prepared from fullerene peapods and
characterized by HRTEM and optical spectroscopy. In comparison to single-walled
carbon nanotubes, the pressure-induced redshifts of the optical transitions in
the outer tubes are significantly smaller below $\sim$10 GPa, demonstrating the
enhanced mechanical stability due to the inner tube already at low pressures.
Anomalies at the critical pressure P$_d$$\approx$12 GPa signal the onset of the
pressure-induced deformation of the tubular cross-sections. The value of P$_d$
is in very good agreement with theoretical predictions of the pressure-induced
structural transitions in double-walled carbon nanotube bundles with similar
average diameters.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-37901210.5206 | Imaginary cone and reflection subgroups of Coxeter groups
math.RT math.GR
The imaginary cone of a Kac-Moody Lie algebra is the convex hull of zero and
the positive imaginary roots. This paper studies the imaginary cone for a class
of root systems of general Coxeter groups W. It is shown that the imaginary
cone of a reflection subgroup of W is contained in that of W, and that for
irreducible infinite W of finite rank, the closed imaginary cone is the only
non-zero, closed, pointed W-stable cone contained in the pointed cone spanned
by the simple roots. For W of finite rank, various natural notions of faces of
the imaginary cone are shown to coincide, the face lattice is explicitly
described in terms of the lattice of facial reflection subgroups and it is
shown that the Tits cone and imaginary cone are related by a duality closely
analogous to the standard duality for polyhedral cones, even though neither of
them is a closed cone in general. Some of these results have application, to be
given in sequels to this paper, to dominance order of Coxeter groups,
associated automata, and construction of modules for generic Iwahori-Hecke
algebras.
| arxiv topic:math.RT math.GR |
arxiv_dataset-37911210.5306 | ALMA Temporal Phase Stability and the Effectiveness of Water Vapor
Radiometer
astro-ph.IM
Atacama Large Millimeter/submillimeter Array (ALMA) will be the world largest
mm/submm interferometer, and currently the Early Science is ongoing, together
with the commissioning and science verification (CSV). Here we present a study
of the temporal phase stability of the entire ALMA system from antennas to the
correlator. We verified the temporal phase stability of ALMA using data, taken
during the last two years of CSV activities. The data consist of integrations
on strong point sources (i.e., bright quasars) at various frequency bands, and
at various baseline lengths (up to 600 m). From the observations of strong
quasars for a long time (from a few tens of minutes, up to an hour), we derived
the 2-point Allan Standard Deviation after the atmospheric phase correction
using the 183 GHz Water Vapor Radiometer (WVR) installed in each 12 m antenna,
and confirmed that the phase stability of all the baselines reached the ALMA
specification. Since we applied the WVR phase correction to all the data
mentioned above, we also studied the effectiveness of the WVR phase correction
at various frequencies, baseline lengths, and weather conditions. The phase
stability often improves a factor of 2 - 3 after the correction, and sometimes
a factor of 7 improvement can be obtained. However, the corrected data still
displays an increasing phase fluctuation as a function of baseline length,
suggesting that the dry component (e.g., N2 and O2) in the atmosphere also
contributes the phase fluctuation in the data, although the imperfection of the
WVR phase correction cannot be ruled out at this moment.
| arxiv topic:astro-ph.IM |
arxiv_dataset-37921210.5406 | Plerionic Supernova Remnants
astro-ph.GA astro-ph.HE
Plerions represent ideal laboratories for the search for neutron stars, the
study of their relativistic winds, and their interaction with their surrounding
supernova ejecta and/or the interstellar medium. As well, they are widely
believed to represent efficient engines for particle acceleration up to the
knee of the cosmic ray spectrum (at about 1E15 eV). Multi-wavelength
observations from the radio to the highest TeV energies, combined with
modelling, have opened a new window to study these objects, and particularly
shed light on their intrinsic properties, diversity, and evolution.
High-resolution X-ray observations are further revealing the structure and
sites for shock acceleration. The missing shells in the majority of these
objects remain puzzling, and the presence of plerions around highly magnetized
neutron stars is still questionable. I review the current status and statistics
of observations of plerionic supernova remnants (SNRs), highlighting combined
radio and X-ray observations of a growing class of atypical, non Crab-like,
plerionic SNRs in our Galaxy. I will also briefly describe the latest
developments to our high-energy SNRs catalogue recently released to the
community, and finally highlight the key questions to be addressed in this
field with future high-energy missions, including Astro-H in the very near
future.
| arxiv topic:astro-ph.GA astro-ph.HE |
arxiv_dataset-37931210.5506 | A dual of MacMahon's theorem on plane partitions
math.CO
A classical theorem of MacMahon states that the number of lozenge tilings of
any centrally symmetric hexagon drawn on the triangular lattice is given by a
beautifully simple product formula. In this paper we present a counterpart of
this formula, corresponding to the {\it exterior} of a concave hexagon obtained
by turning 120 degrees after drawing each side (MacMahon's hexagon is obtained
by turning 60 degrees after each step).
| arxiv topic:math.CO |
arxiv_dataset-37941210.5606 | Finite type minimal annuli in $\mathbb{S}^2 \times \mathbb{R}$
math.DG
We study minimal annuli in $\mathbb{S}^2 \times \mathbb{R}$ of finite type by
relating them to harmonic maps $\mathbb{C} \to \mathbb{S}^2$ of finite type. We
rephrase an iteration by Pinkall-Sterling in terms of polynomial Killing
fields. We discuss spectral curves, spectral data and the geometry of the
isospectral set. We consider polynomial Killing fields with zeroes and the
corresponding singular spectral curves, bubbletons and simple factors. We
investigate the differentiable structure on the isospectral set of any finite
type minimal annulus. We apply the theory to a 2-parameter family of embedded
minimal annuli foliated by horizontal circles.
| arxiv topic:math.DG |
arxiv_dataset-37951210.5706 | The construction of characteristic matrixes of dynamic coverings using
an incremental approach
cs.IT math.IT
The covering approximation space evolves in time due to the explosion of the
information, and the characteristic matrixes of coverings viewed as an
effective approach to approximating the concept should update with time for
knowledge discovery. This paper further investigates the construction of
characteristic matrixes without running the matrix acquisition algorithm
repeatedly. First, we present two approaches to computing the characteristic
matrixes of the covering with lower time complexity. Then, we investigate the
construction of the characteristic matrixes of the dynamic covering using the
incremental approach. We mainly address the characteristic matrix updating from
three aspects: the variations of elements in the covering, the immigration and
emigration of objects and the changes of attribute values. Afterwards, several
illustrative examples are employed to show that the proposed approach can
effectively compute the characteristic matrixes of the dynamic covering for
approximations of concepts.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-37961210.5806 | Multi-Stage Multi-Task Feature Learning
stat.ML
Multi-task sparse feature learning aims to improve the generalization
performance by exploiting the shared features among tasks. It has been
successfully applied to many applications including computer vision and
biomedical informatics. Most of the existing multi-task sparse feature learning
algorithms are formulated as a convex sparse regularization problem, which is
usually suboptimal, due to its looseness for approximating an $\ell_0$-type
regularizer. In this paper, we propose a non-convex formulation for multi-task
sparse feature learning based on a novel non-convex regularizer. To solve the
non-convex optimization problem, we propose a Multi-Stage Multi-Task Feature
Learning (MSMTFL) algorithm; we also provide intuitive interpretations,
detailed convergence and reproducibility analysis for the proposed algorithm.
Moreover, we present a detailed theoretical analysis showing that MSMTFL
achieves a better parameter estimation error bound than the convex formulation.
Empirical studies on both synthetic and real-world data sets demonstrate the
effectiveness of MSMTFL in comparison with the state of the art multi-task
sparse feature learning algorithms.
| arxiv topic:stat.ML |
arxiv_dataset-37971210.5906 | Nonlinear sigma models with AdS supersymmetry in three dimensions
hep-th
In three-dimensional anti-de Sitter (AdS) space, there exist several
realizations of N-extended supersymmetry, which are traditionally labelled by
two non-negative integers p>=q such that p+q=N. Different choices of p and q,
with N fixed, prove to lead to different restrictions on the target space
geometry of supersymmetric nonlinear sigma-models. We classify all possible
types of hyperkahler target spaces for the cases N=3 and N=4 by making use of
two different realizations for the most general (p,q) supersymmetric
sigma-models: (i) off-shell formulations in terms of N=3 and N=4 projective
supermultiplets; and (ii) on-shell formulations in terms of covariantly chiral
scalar superfields in (2,0) AdS superspace. Depending on the type of N=3,4 AdS
supersymmetry, nonlinear sigma-models can support one of the following target
space geometries: (i) hyperkahler cones; (ii) non-compact hyperkahler manifolds
with a U(1) isometry group which acts non-trivially on the two-sphere of
complex structures; (iii) arbitrary hyperkahler manifolds including compact
ones. The option (iii) is realized only in the case of critical (4,0) AdS
supersymmetry.
As an application of the (4,0) AdS techniques developed, we also construct
the most general nonlinear sigma-model in Minkowski space with a non-centrally
extended N=4 Poincare supersymmetry. Its target space is a hyperkahler cone
(which is characteristic of N=4 superconformal sigma-models), but the
sigma-model is massive. The Lagrangian includes a positive potential
constructed in terms of the homothetic conformal Killing vector the target
space is endowed with. This mechanism of mass generation differs from the
standard one which corresponds to a sigma-model with the ordinary N=4 Poincare
supersymmetry and which makes use of a tri-holomorphic Killing vector.
| arxiv topic:hep-th |
arxiv_dataset-37981210.6006 | Atlas and wavenumber tables for visible part ($419 \div 696$ nm) of the
rovibronic multiline emission spectrum of the $D_2$ molecule measured with
moderate resolution
physics.optics physics.chem-ph
The visible part ($\approx 419 \div 696$ nm) of the multiline
electronic-vibro-rotational emission spectrum of the $D_2$ molecule was
recorded with moderate resolution (line widths $\approx 0.013$ nm). The
resolution was limited by Doppler broadening of spectral lines. After numerical
deconvolution of the recorded intensity distributions and proper calibration of
the spectrometer the new set of wavenumber values was obtained. The results are
reported in the form of an atlas divided into 158 sections (each section covers
about 1.5 nm) containing pictures of images in the focal plane of the
spectrometer, intensity distributions in linear and logarithmic scales and the
table containing wavenumber and relative intensity values for 11990 spectral
lines together with existing line assignments.
| arxiv topic:physics.optics physics.chem-ph |
arxiv_dataset-37991210.6106 | Determining the area of convergence in Bloodstain Pattern Analysis: a
probabilistic approach
physics.class-ph
A complete procedure for identifying the area of convergence of blood drops
originated from a single static source is presented. Both for bloodstains lying
on an horizontal and on a vertical plane a complete study is developed, based
on error analysis and on an opportunely defined joint probability density for
the orientation of the horizontal projections of the trajectories of the drops.
The method generates a probabilistic map for the area of convergence, directly
linking the angles of impact, and their uncertainties, to the projection on the
ground of the point of origin. One of the objectives consists in providing a
statistical definition of area of convergence, extending to this topic the
mathematical accuracy of the calculation of the angle of impact in bloodstain
pattern analysis (BPA).
| arxiv topic:physics.class-ph |
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