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arxiv_dataset-30001111.1764 | A Well-Posed Kelvin-Helmholtz Instability Test and Comparison
astro-ph.IM physics.comp-ph
Recently, there has been a significant level of discussion of the correct
treatment of Kelvin-Helmholtz instability in the astrophysical community. This
discussion relies largely on how the KHI test is posed and analyzed. We pose a
stringent test of the initial growth of the instability. The goal is to provide
a rigorous methodology for verifying a code on two dimensional Kelvin-Helmholtz
instability. We ran the problem in the Pencil Code, Athena, Enzo, NDSPHMHD, and
Phurbas. A strict comparison, judgment, or ranking, between codes is beyond the
scope of this work, though this work provides the mathematical framework needed
for such a study. Nonetheless, how the test is posed circumvents the issues
raised by tests starting from a sharp contact discontinuity yet it still shows
the poor performance of Smoothed Particle Hydrodynamics. We then comment on the
connection between this behavior to the underlying lack of zeroth-order
consistency in Smoothed Particle Hydrodynamics interpolation. We comment on the
tendency of some methods, particularly those with very low numerical diffusion,
to produce secondary Kelvin-Helmholtz billows on similar tests. Though the lack
of a fixed, physical diffusive scale in the Euler equations lies at the root of
the issue, we suggest that in some methods an extra diffusion operator should
be used to damp the growth of instabilities arising from grid noise. This
statement applies particularly to moving-mesh tessellation codes, but also to
fixed-grid Godunov schemes.
| arxiv topic:astro-ph.IM physics.comp-ph |
arxiv_dataset-30011111.1864 | Observers can always generate nonlocal correlations without aligning
measurements by covering all their bases
quant-ph
Quantum theory allows for correlations between the outcomes of distant
measurements that are inconsistent with any locally causal theory, as
demonstrated by the violation of a Bell inequality. Typical demonstrations of
these correlations require careful alignment between the measurements, which
requires distant parties to share a reference frame. Here, we prove, following
a numerical observation by Shadbolt et al., that if two parties share a Bell
state and each party randomly chooses three orthogonal measurements, then the
parties will always violate a Bell inequality. Furthermore, we prove that this
probability is highly robust against local depolarizing noise, in that small
levels of noise only decrease the probability of violating a Bell inequality by
a small amount. We also show that generalizing to N parties increases the
robustness against noise. These results improve on previous ones that only
allowed a high probability of violating a Bell inequality for large numbers of
parties.
| arxiv topic:quant-ph |
arxiv_dataset-30021111.1964 | The Urge to Merge: When Cellular Service Providers Pool Capacity
cs.NI
As cellular networks are turning into a platform for ubiquitous data access,
cellular operators are facing a severe data capacity crisis due to the
exponential growth of traffic generated by mobile users. In this work, we
investigate the benefits of sharing infrastructure and spectrum among two
cellular operators. Specifically, we provide a multi-cell analytical model
using stochastic geometry to identify the performance gain under different
sharing strategies, which gives tractable and accurate results. To validate the
performance using a realistic setting, we conduct extensive simulations for a
multi-cell OFDMA system using real base station locations. Both analytical and
simulation results show that even a simple cooperation strategy between two
similar operators, where they share spectrum and base stations, roughly
quadruples capacity as compared to the capacity of a single operator. This is
equivalent to doubling the capacity per customer, providing a strong incentive
for operators to cooperate, if not actually merge.
| arxiv topic:cs.NI |
arxiv_dataset-30031111.2064 | Tropical decomposition of Young's partition lattice
math.CO math.AC math.RT
Young's partition lattice $L(m,n)$ consists of unordered partitions having
$m$ parts where each part is at most $n$. Using methods from complex algebraic
geometry, R. Stanley proved that $L(m,n)$ is rank-symmetric, unimodal, and
strongly Sperner. Moreover, he conjectured that $L(m,n)$ has a stronger
property called symmetric chain decomposition. Despite many efforts, this
conjecture has only been proved for $\min(m,n)\leq 4$. In this paper, we
decompose $L(m,n)$ into level sets for certain tropical polynomials derived
from the secant varieties of the rational normal curve in projective space, and
we find that the resulting subposets have an elementary raising and lowering
algorithm. As a corollary, we obtain a symmetric chain decomposition for the
subposet of $L(m,n)$ consisting of "sufficiently generic" partitions.
| arxiv topic:math.CO math.AC math.RT |
arxiv_dataset-30041111.2164 | Integral equations in MHD: theory and application
physics.flu-dyn
The induction equation of kinematic magnetohydrodynamics is mathematically
equivalent to a system of integral equations for the magnetic field in the bulk
of the fluid and for the electric potential at its boundary. We summarize the
recent developments concerning the numerical implementation of this scheme and
its applications to various forward and inverse problems in dynamo theory and
applied MHD.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-30051111.2264 | Free Bosonic Vertex Operator Algebras on Genus Two Riemann Surfaces II
math.QA
We continue our program to define and study $n$-point correlation functions
for a vertex operator algebra $V$ on a higher genus compact Riemann surface
obtained by sewing surfaces of lower genus. Here we consider Riemann surfaces
of genus 2 obtained by attaching a handle to a torus. We obtain closed formulas
for the genus two partition function for free bosonic theories and lattice
vertex operator algebras $V_L$. We prove that the partition function is
holomorphic in the sewing parameters on a given suitable domain and describe
its modular properties. We also compute the genus two Heisenberg vector
$n$-point function and show that the Virasoro vector one point function
satisfies a genus two Ward identity. We compare our results with those obtained
in the companion paper, when a pair of tori are sewn together, and show that
the partition functions are not compatible in the neighborhood of a two-tori
degeneration point. The \emph{normalized} partition functions of a lattice
theory $V_L$ \emph{are} compatible, each being identified with the genus two
theta function of $L$.
| arxiv topic:math.QA |
arxiv_dataset-30061111.2364 | Generic Pseudogroups on (C,0) and the Topology of Leaves
math.DS
We show that generically a pseudogroup generated by holomorphic
diffeomorphisms defined about $0 \in \mathbb{C}$ is free in the sense of
pseudogroups even if the class of conjugacy of the generators is fixed. This
result has a number of consequences on the topology of leaves for a (singular)
holomorphic foliation defined on a neighborhood of an invariant curve. In
particular in the classical and simplest case arising from local foliations
possessing a unique separatrix that is given by a cusp of the form
$\{y^2-x^{2k+1}=0\}$, our results allow us to settle the problem of showing
that a generic foliation possesses only countably many non-simply connected
leaves and that this countable set is, indeed, infinite.
| arxiv topic:math.DS |
arxiv_dataset-30071111.2464 | Regularity of weak solutions of the compressible barotropic
Navier-Stokes equations
math.AP
Regularity and uniqueness of weak solutions of the compressible barotropic
Navier-Stokes equations with constant viscosity coefficients is proven for
small time in dimension $N=2,3$ under periodic boundary conditions. In this
paper, the initial density is not required to have a positive lower bound and
the pressure law is assumed to satisfy a condition that reduces to
$P(\rho)=a\rho^{\gamma}$ with $\gamma>1$ (in dimension three, additional
conditions of size will be ask on $\gamma$). The second part of the paper is
devoted to blow-up criteria for slightly subcritical initial data for the
scaling of the equations when the viscosity coefficients $(\mu,\lambda)$ are
assumed constant provided that their ratio is large enough (in particular
$0<\lambda<(5/4)\mu$). More precisely we prove that under the condition $\rho$
belongs to $L^{\infty}((0,T)\times\T^{N})$ then we can extend the unique
solution beyond $T>0$. Finally, we prove that weak solutions in the torus
$\mathbb{T}^{N}$ turn out to be smooth as long as the density remains bounded
in $L^{\infty}(0,T,L^{(N+1+\e)\gamma}(\mathbb{T}^{N}))$ with $\e>0$ arbitrary
small. This result may be considered as a Prodi-Serrin theorem (see
\cite{prodi} and \cite{serrin}) for compressible Navier-Stokes system.
| arxiv topic:math.AP |
arxiv_dataset-30081111.2564 | Scattering from incipient stripe order in the high-temperature
superconductor Bi2Sr2CaCu2O8+d
cond-mat.str-el cond-mat.supr-con
Recently we have used spectroscopic mapping with the scanning tunneling
microscope to probe modulations of the electronic density of states in single
crystals of the high temperature superconductor Bi2Sr2CaCu2O8+d (Bi-2212) as a
function of temperature [C. V. Parker et al., Nature (London) 468, 677 (2010)].
These measurements showed Cu-O bond-oriented modulations that form below the
pseudogap temperature with a temperature-dependent energy dispersion displaying
different behaviors in the superconducting and pseudogap states. Here we
demonstrate that quasiparticle scattering off impurities does not capture the
experimentally observed energy- and temperature-dependence of these
modulations. Instead, a model of scattering of quasiparticles from short-range
stripe order, with periodicity near four lattice constants (4a), reproduces the
experimentally observed energy dispersion of the bond-oriented modulations and
its temperature dependence across the superconducting critical temperature, Tc.
The present study confirms the existence of short-range stripe order in
Bi-2212.
| arxiv topic:cond-mat.str-el cond-mat.supr-con |
arxiv_dataset-30091111.2664 | A Collaborative Mechanism for Crowdsourcing Prediction Problems
cs.LG cs.GT
Machine Learning competitions such as the Netflix Prize have proven
reasonably successful as a method of "crowdsourcing" prediction tasks. But
these competitions have a number of weaknesses, particularly in the incentive
structure they create for the participants. We propose a new approach, called a
Crowdsourced Learning Mechanism, in which participants collaboratively "learn"
a hypothesis for a given prediction task. The approach draws heavily from the
concept of a prediction market, where traders bet on the likelihood of a future
event. In our framework, the mechanism continues to publish the current
hypothesis, and participants can modify this hypothesis by wagering on an
update. The critical incentive property is that a participant will profit an
amount that scales according to how much her update improves performance on a
released test set.
| arxiv topic:cs.LG cs.GT |
arxiv_dataset-30101111.2764 | The Assembly of the Halo System of the Milky Way as Revealed by
SDSS/SEGUE -- The CEMP Star Connection
astro-ph.GA
In recent years, massive new spectroscopic data sets, such as the over half
million stellar spectra obtained during the course of SDSS (in particular its
sub-survey SEGUE), have provided the quantitative detail required to formulate
a coherent story of the assembly and evolution of the Milky Way. The disk and
halo systems of our Galaxy have been shown to be both more complex, and more
interesting, than previously thought. Here we concentrate on the halo system of
the Milky Way. New data from SDSS/SEGUE has revealed that the halo system
comprises at least two components, the inner halo and the outer halo, with
demonstrably different characteristics (metallicity distributions, density
distributions, kinematics, etc.). In addition to suggesting new ways to examine
these data, the inner/outer halo dichotomy has enabled an understanding of at
least one long-standing observational result, the increase of the fraction of
carbon-enhanced metal-poor (CEMP) stars with decreasing metallicity.
| arxiv topic:astro-ph.GA |
arxiv_dataset-30111111.2864 | The formation of shell galaxies similar to NGC 7600 in the cold dark
matter cosmogony
astro-ph.GA astro-ph.CO
We present new deep observations of 'shell' structures in the halo of the
nearby elliptical galaxy NGC 7600, alongside a movie of galaxy formation in a
cold dark matter universe (available at
http://www.virgo.dur.ac.uk/shell-galaxies). The movie, based on an ab initio
cosmological simulation, shows how continuous accretion of clumps of dark
matter and stars creates a swath of diffuse circumgalactic structures. The
disruption of a massive clump on a near-radial orbit creates a complex system
of transient concentric shells which bare a striking resemblance to those of
NGC 7600. With the aid of the simulation we interpret NGC 7600 in the context
of the CDM model.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-30121111.2964 | Fano Hypersurfaces in Positive Characteristic
math.AG
We prove that a general Fano hypersurface in a projective space over an
algebraically closed field of arbitrary characteristic is separably rationally
connected.
| arxiv topic:math.AG |
arxiv_dataset-30131111.3064 | Hamiltonian formalism of fractional systems
physics.class-ph math-ph math.MP
In this paper we consider a generalized classical mechanics with fractional
derivatives. The generalization is based on the time-clock randomization of
momenta and coordinates taken from the conventional phase space. The fractional
equations of motion are derived using the Hamiltonian formalism. The approach
is illustrated with a simple-fractional oscillator in a free state and under an
external force. Besides the behavior of the coupled fractional oscillators is
analyzed. The natural extension of this approach to continuous systems is
stated. The interpretation of the mechanics is discussed.
| arxiv topic:physics.class-ph math-ph math.MP |
arxiv_dataset-30141111.3164 | Lifts of convex sets and cone factorizations
math.OC
In this paper we address the basic geometric question of when a given convex
set is the image under a linear map of an affine slice of a given closed convex
cone. Such a representation or 'lift' of the convex set is especially useful if
the cone admits an efficient algorithm for linear optimization over its affine
slices. We show that the existence of a lift of a convex set to a cone is
equivalent to the existence of a factorization of an operator associated to the
set and its polar via elements in the cone and its dual. This generalizes a
theorem of Yannakakis that established a connection between polyhedral lifts of
a polytope and nonnegative factorizations of its slack matrix. Symmetric lifts
of convex sets can also be characterized similarly. When the cones live in a
family, our results lead to the definition of the rank of a convex set with
respect to this family. We present results about this rank in the context of
cones of positive semidefinite matrices. Our methods provide new tools for
understanding cone lifts of convex sets.
| arxiv topic:math.OC |
arxiv_dataset-30151111.3264 | Equilibrium, fluctuation relations and transport for irreversible
deterministic dynamics
math.DS cond-mat.stat-mech
In a recent paper [M. Colangeli \textit{et al.}, J.\ Stat.\ Mech.\ P04021,
(2011)] it was argued that the Fluctuation Relation for the phase space
contraction rate $\Lambda$ could suitably be extended to non-reversible
dissipative systems. We strengthen here those arguments, providing analytical
and numerical evidence based on the properties of a simple irreversible
nonequilibrium baker model. We also consider the problem of response, showing
that the transport coefficients are not affected by the irreversibility of the
microscopic dynamics. In addition, we prove that a form of \textit{detailed
balance}, hence of equilibrium, holds in the space of relevant variables,
despite the irreversibility of the phase space dynamics. This corroborates the
idea that the same stochastic description, which arises from a projection onto
a subspace of relevant coordinates, is compatible with quite different
underlying deterministic dynamics. In other words, the details of the
microscopic dynamics are largely irrelevant, for what concerns properties such
as those concerning the Fluctuation Relations, the equilibrium behaviour and
the response to perturbations.
| arxiv topic:math.DS cond-mat.stat-mech |
arxiv_dataset-30161111.3364 | SSOS: A Moving Object Image Search Tool for Asteroid Precovery at the
CADC
astro-ph.IM astro-ph.EP
While regular archive searches can find images at a fixed location, they
cannot find images of moving targets such as asteroids. The Solar System Object
Search (SSOS) at the Canadian Astronomy Data Centre allows users to search for
images of moving objects. SSOS accepts as input either a list of observations,
an object designation, a set of orbital elements, or a user-generated ephemeris
for an object. It then searches for observations of that object over a range of
dates. The user is then presented with a list of images containing that object
from a variety of archives. Initially created to search the CFHT MegaCam
archive, SSOS has been extended to other telescope archives including Gemini,
Subaru/SuprimeCam, HST, and several ESO instruments for a total of 1.6 million
images. The SSOS tool is located on the web at:
http://www.cadc.hia.nrc.gc.ca/ssos
| arxiv topic:astro-ph.IM astro-ph.EP |
arxiv_dataset-30171111.3464 | Extensions and applications of ACF mappings
math.OC
Using a definition of ASF sequences derived from the definition of asymptotic
contractions of the final type of ACF, we give some new fixed points theorem
for cyclic mappings and alternating mapping which extend results from T.Suzuki
and X.Zhang.
| arxiv topic:math.OC |
arxiv_dataset-30181111.3564 | Universal Order Statistics of Random Walks
cond-mat.stat-mech cond-mat.dis-nn math.PR
We study analytically the order statistics of a time series generated by the
successive positions of a symmetric random walk of n steps with step lengths of
finite variance \sigma^2. We show that the statistics of the gap
d_{k,n}=M_{k,n} -M_{k+1,n} between the k-th and the (k+1)-th maximum of the
time series becomes stationary, i.e, independent of n as n\to \infty and
exhibits a rich, universal behavior. The mean stationary gap (in units of
\sigma) exhibits a universal algebraic decay for large k,
<d_{k,\infty}>/\sigma\sim 1/\sqrt{2\pi k}, independent of the details of the
jump distribution. Moreover, the probability density (pdf) of the stationary
gap exhibits scaling, Proba.(d_{k,\infty}=\delta)\simeq (\sqrt{k}/\sigma)
P(\delta \sqrt{k}/\sigma), in the scaling regime when \delta\sim
<d_{k,\infty}>\simeq \sigma/\sqrt{2\pi k}. The scaling function P(x) is
universal and has an unexpected power law tail, P(x) \sim x^{-4} for large x.
For \delta \gg <d_{k,\infty}> the scaling breaks down and the pdf gets cut-off
in a nonuniversal way. Consequently, the moments of the gap exhibit an unusual
multi-scaling behavior.
| arxiv topic:cond-mat.stat-mech cond-mat.dis-nn math.PR |
arxiv_dataset-30191111.3664 | Is mathematics invading human cells? Impressions from a collaboration
with diabetes doctors
math.HO math-ph math.AP math.MP q-bio.OT
The author describes some of his experiences as a mathematician cooperating
with diabetes specialists.
| arxiv topic:math.HO math-ph math.AP math.MP q-bio.OT |
arxiv_dataset-30201111.3764 | Baryon and Sunyaev-Zel'dovich effect properties of MareNostrum and
MultiDark simulated clusters (MUSIC)
astro-ph.CO
We report the first results of the MUSIC project. It consists of two data
sets of resimulates clusters extracted from two large dark matter only
simulations: Marenostrum Universe and Multidark. In total, the MUSIC contains
more than 400 clusters resimulated with high resolution both with radiative and
non-radiative physics included. Here we present the first results on the
properties of the baryon content and the Sunyaev Zeldovich scaling relations.
| arxiv topic:astro-ph.CO |
arxiv_dataset-30211111.3864 | Self consistent, absolute calibration technique for photon number
resolving detectors
quant-ph physics.ins-det physics.optics
Well characterized photon number resolving detectors are a requirement for
many applications ranging from quantum information and quantum metrology to the
foundations of quantum mechanics. This prompts the necessity for reliable
calibration techniques at the single photon level. In this paper we propose an
innovative absolute calibration technique for photon number resolving
detectors, using a pulsed heralded photon source based on parametric down
conversion. The technique, being absolute, does not require reference standards
and is independent upon the performances of the heralding detector. The method
provides the results of quantum efficiency for the heralded detector as a
function of detected photon numbers. Furthermore, we prove its validity by
performing the calibration of a Transition Edge Sensor based detector, a real
photon number resolving detector that has recently demonstrated its
effectiveness in various quantum information protocols.
| arxiv topic:quant-ph physics.ins-det physics.optics |
arxiv_dataset-30221111.3964 | Constraining Sources of Ultra High Energy Cosmic Rays Using High Energy
Observations with the Fermi Satellite
astro-ph.HE
We analyze the conditions that enable acceleration of particles to ultra-high
energies, ~10^{20} eV (UHECRs). We show that broad band photon data recently
provided by WMAP, ISOCAM, Swift and Fermi satellites, yield constraints on the
ability of active galactic nuclei (AGN) to produce UHECRs. The high energy (MeV
- GeV) photons are produced by Compton scattering of the emitted low energy
photons and the cosmic microwave background or extra-galactic background light.
The ratio of the luminosities at high and low photon energies can therefore be
used as a probe of the physical conditions in the acceleration site. We find
that existing data excludes core regions of nearby radio-loud AGN as possible
acceleration sites of UHECR protons. However, we show that giant radio lobes
are not excluded. We apply our method to Cen A, and show that acceleration of
protons to ~10^{20} eV can only occur at distances >~ 100 kpc from the core.
| arxiv topic:astro-ph.HE |
arxiv_dataset-30231111.4064 | Characterization of Zero-point Vibration in One-Component Crystals
cond-mat.stat-mech cond-mat.mtrl-sci quant-ph
We study the magnitude of zero-point vibration in one-component crystals. For
the crystals whose constituent atoms share the same bonding geometry, we prove
the existence of a characteristic temperature, T0, at which the magnitude of
zero-point vibrations equals to that of the excited vibrations. Within the
Debye model T0 is found to be ~1/3 of the Debye temperature. The results are
demonstrated in realistic systems.
| arxiv topic:cond-mat.stat-mech cond-mat.mtrl-sci quant-ph |
arxiv_dataset-30241111.4164 | Non-extremal Reissner-Nordstrom black hole: Do asymptotic quasi-normal
modes carry information about the quantum properties of the black hole?
gr-qc
We analyze the largely accepted formulas for the asymptotic quasi-normal
frequencies of the non-extremal Reissner-Nordstr\"om black hole, (for the
electromagnetic-gravitational/scalar perturbations). We focus on the question
of whether the gap in the spacing in the imaginary part of the QNM frequencies
has a well defined limit as n goes to infinity and if so, what is the value of
the limit. The existence and the value of this limit has a crucial importance
from the point of view of the currently popular Maggiore's conjecture, which
represents a way of connecting the asymptotic behavior of the quasi-normal
frequencies to the black hole thermodynamics. With the help of previous results
and insights we will prove that the gap in the imaginary part of the
frequencies does not converge to any limit, unless one puts specific
constraints on the ratio of the two surface gravities related to the two
spacetime horizons. Specifically the constraints are that the ratio of the
surface gravities must be rational and such that it is given by two relatively
prime integers N, M, whose product is an even number. If the constraints are
fulfilled the limit of the sequence is still not guaranteed to exist, but if it
exists its value is given as the lowest common multiplier of the two surface
gravities. At the end of the paper we discuss the possible implications of our
results.
| arxiv topic:gr-qc |
arxiv_dataset-30251111.4264 | On Quantum Integrable Systems
quant-ph physics.acc-ph
Many quantum integrable systems are obtained using an accelerator physics
technique known as Ermakov (or normalized variables) transformation. This
technique was used to create classical nonlinear integrable lattices for
accelerators and nonlinear integrable plasma traps. Now, all classical results
are carried over to a nonrelativistic quantum case.
| arxiv topic:quant-ph physics.acc-ph |
arxiv_dataset-30261111.4364 | Limits on Self-Interacting Dark Matter
astro-ph.CO hep-ph
We impose new severe constraints on the self-interactions of fermionic
asymmetric dark matter based on observations of nearby old neutron stars. WIMP
self-interactions mediated by Yukawa- type interactions can lower significantly
the number of WIMPs necessary for gravitational collapse of the WIMP population
accumulated in a neutron star. Even nearby neutron stars located at regions of
low dark matter density can accrete sufficient number of WIMPs that can
potentially collapse, form a mini black hole, and destroy the host star. Based
on this, we derive constraints on the WIMP self-interactions which in some
cases are by several orders of magnitude stricter than the ones from the bullet
cluster (which are currently considered the most stringent).
| arxiv topic:astro-ph.CO hep-ph |
arxiv_dataset-30271111.4464 | Comments on: "Starting solutions for some unsteady unidirectional flows
of a second grade fluid," [Int. J. Eng. Sci. 43 (2005) 781]
physics.flu-dyn
A significant mathematical error is identified and corrected in a recent
highly-cited paper on oscillatory flows of second-grade fluids [Fetecau &
Fetecau (2005). Int. J. Eng. Sci., 43, 781--789]. The corrected solutions are
shown to agree identically with numerical ones generated by a finite-difference
scheme, while the original ones of Fetecau & Fetecau do not. A list of other
recent papers in the literature that commit the error corrected in this Comment
is compiled. Finally, a summary of related erroneous papers in this journal is
presented as an Appendix.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-30281111.4564 | On the Generalized Hill Process for Small Parameters and Applications
stat.ME
Let $X_{1},X_{2},...$ be a sequence of independent copies (s.i.c) of a real
random variable (r.v.) $X\geq 1$, with distribution function $df$
$F(x)=\mathbb{P}% (X\leq x)$ and let $X_{1,n}\leq X_{2,n} \leq ... \leq
X_{n,n}$ be the order statistics based on the $n\geq 1$ first of these
observations. The following continuous generalized Hill process {equation*}
T_{n}(\tau)=k^{-\tau}\sum_{j=1}^{j=k}j^{\tau}(\log X_{n-j+1,n}-\log X_{n-j,n}),
\label{dl02} {equation*} $\tau >0$, $1\leq k \leq n$, has been introduced as a
continuous family of estimators of the extreme value index, and largely studied
for statistical purposes with asymptotic normality results restricted to $\tau
> 1/2$. We extend those results to $0 < \tau \leq 1/2$ and show that asymptotic
normality is still valid for $\tau=1/2$. For $0 < \tau <1/2$, we get non
Gaussian asymptotic laws which are closely related to the Riemann function $%
\zeta(s)=\sum_{n=1}^{\infty} n^{-s},s>1$
| arxiv topic:stat.ME |
arxiv_dataset-30291111.4664 | Homotopy invariance of non-stable K_1-functors
math.AG math.GR math.KT
Let G be reductive algebraic group over a field k, such that every semisimple
normal subgroup of G has isotropic rank >=2. Let K_1^G be the non-stable
K_1-functor associated to G (also called the Whitehead group of G in the field
case). We show that K_1^G(k)=K_1^G(k[X_1,...,X_n]) for any n>= 1. This implies
that K_1^G is A^1-homotopy invariant on the category of regular k-algebras, if
k is perfect. If k is infinite perfect, one also deduces that K_1^G(R)->
K_1^G(K) is injective for any regular local k-algebra R with the fraction field
K.
| arxiv topic:math.AG math.GR math.KT |
arxiv_dataset-30301111.4764 | Saying Hello World with Epsilon - A Solution to the 2011 Instructive
Case
cs.SE
Epsilon is an extensible platform of integrated and task-specific languages
for model management. With solutions to the 2011 TTC Hello World case, this
paper demonstrates some of the key features of the Epsilon Object Language (an
extension and reworking of OCL), which is at the core of Epsilon. In addition,
the paper introduces several of the task-specific languages provided by Epsilon
including the Epsilon Generation Language (for model-to-text transformation),
the Epsilon Validation Language (for model validation) and Epsilon Flock (for
model migration).
| arxiv topic:cs.SE |
arxiv_dataset-30311111.4864 | Anisotropic Magnetoresistance Effects in Fe, Co, Ni, Fe_4N, and
Half-Metallic Ferromagnet: A Systematic Analysis
cond-mat.mtrl-sci cond-mat.mes-hall cond-mat.other
We theoretically analyze the anisotropic magnetoresistance (AMR) effects of
bcc Fe (+), fcc Co (+), fcc Ni (+), Fe$_4$N (-), and a half-metallic
ferromagnet (-). The sign in each ( ) represents the sign of the AMR ratio
observed experimentally. We here use the two-current model for a system
consisting of a spin-polarized conduction state and localized d states with
spin--orbit interaction. From the model, we first derive a general expression
of the AMR ratio. The expression consists of a resistivity of the conduction
state of the $\sigma$ spin ($\sigma=\uparrow$ or $\downarrow$), $\rho_{s
\sigma}$, and resistivities due to s--d scattering processes from the
conduction state to the localized d states. On the basis of this expression, we
next find a relation between the sign of the AMR ratio and the s--d scattering
process. In addition, we obtain expressions of the AMR ratios appropriate to
the respective materials. Using the expressions, we evaluate their AMR ratios,
where the expressions take into account the values of $\rho_{s
\downarrow}/\rho_{s \uparrow}$ of the respective materials. The evaluated AMR
ratios correspond well to the experimental results.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall cond-mat.other |
arxiv_dataset-30321111.4964 | Sampling and Squeezing Electromagnetic Waves through Subwavelength
Ultranarrow Regions or Openings
cond-mat.mtrl-sci
Here, we investigate the physical mechanisms that may enable squeezing a
complex electromagnetic field distribution through a narrow and/or partially
obstructed region with little amplitude and phase distortions. Following our
recent works, such field manipulations may be made possible by a procedure in
which the incoming wave is first "sampled" "pixel by pixel" using an array of
metallic waveguides, and in a second step the energy corresponding to each
individual pixel is "squeezed" through a very narrow channel filled with a
permittivity-near zero material. In this work, we study in detail these
processes in scenarios where the electromagnetic wave is compressed along a
single direction of space, and present theoretical models that enable the
analytical modeling of such phenomena. Full-wave results obtained with an
electromagnetic simulator, demonstrate the possibility of compressing an
incoming wave several folds through ultranarrow channels filled with silicon
carbide. The "sampling and squeezing" concept may enable unparalleled control
of electromagnetic waves in the nanoscale.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-30331111.5064 | Generic Modules for string algebras
math.RT math.AG
We describe the generic modules in each component of the spaces of
representations of certain string algebras. In so doing, we calculate the
dimensions of higher self-extension groups for generic modules. This algorithm
lends itself for use in determining tilting modules over gentle string
algebras.
| arxiv topic:math.RT math.AG |
arxiv_dataset-30341111.5164 | Massless, String Localized Quantum Fields for Any Helicity
math-ph math.MP
For any massless, irreducible representation of the covering of the proper,
orthochronous Poincar\'e group we construct covariant, free quantum fields that
generate the representation space from the vacuum and are localized in
semi-infinite strings in the sense of commutation or anti-commutation of the
field operators at space-like separation of the strings.
| arxiv topic:math-ph math.MP |
arxiv_dataset-30351111.5264 | LAGRANGE: LAser GRavitational-wave ANtenna at GEo-lunar Lagrange points
astro-ph.IM gr-qc
We describe a new space gravitational wave observatory design called LAGRANGE
that maintains all important LISA science at about half the cost and with
reduced technical risk. It consists of three drag-free spacecraft in the most
stable geocentric formation, the Earth-Moon L3, L4, and L5 Lagrange points.
Fixed antennas allow continuous contact with the Earth, solving the problem of
communications bandwidth and latency. A 70 mm diameter AuPt sphere with a 35 mm
gap to its enclosure serves as a single inertial reference per spacecraft,
which is operated in "true" drag-free mode (no test mass forcing). This is the
core of the Modular Gravitational Reference Sensor whose other advantages are:
a simple caging design based on the DISCOS 1972 drag-free mission, an all
optical read-out with pm fine and nm coarse sensors, and the extensive
technology heritage from the Honeywell gyroscopes, and the DISCOS and Gravity
Probe B drag-free sensors. An Interferometric Measurement System, designed with
reflective optics and a highly stabilized frequency standard, performs the
inter-test mass ranging and requires a single optical bench with one laser per
spacecraft. Two 20 cm diameter telescopes per spacecraft, each with in-field
pointing, incorporate novel technology developed for advanced optical systems
by Lockheed Martin, who also designed the spacecraft based on a multi-flight
proven bus structure. Additional technological advancements include the
drag-free propulsion, thermal control, charge management systems, and
materials. LAGRANGE sub-systems are designed to be scalable and modular, making
them interchangeable with those of LISA or other gravitational science
missions. We plan to space qualify critical technologies on small and nano
satellite flights, with the first launch (UV-LED Sat) in 2013.
| arxiv topic:astro-ph.IM gr-qc |
arxiv_dataset-30361111.5364 | Quantum Locality?
quant-ph
Robert Griffiths has recently addressed, within the framework of a
'consistent quantum theory' that he has developed, the issue of whether, as is
often claimed, quantum mechanics entails a need for faster-than-light transfers
of information over long distances. He argues that the putative proofs of this
property that involve hidden variables include in their premises some
essentially classical-physics-type assumptions that are fundamentally
incompatible with the precepts of quantum physics. One cannot logically prove
properties of a system by establishing, instead, properties of a system
modified by adding properties alien to the original system. Hence Griffiths'
rejection of hidden-variable-based proofs is logically warranted. Griffiths
mentions the existence of a certain alternative proof that does not involve
hidden variables, and that uses only macroscopically described observable
properties. He notes that he had examined in his book proofs of this general
kind, and concluded that they provide no evidence for nonlocal influences. But
he did not examine the particular proof that he cites. An examination of that
particular proof by the method specified by his 'consistent quantum theory'
shows that the cited proof is valid within that restrictive version of quantum
theory. An added section responds to Griffiths' reply, which cites general
possibilities of ambiguities that make what is to be proved ill-defined, and
hence render the pertinent 'consistent framework' ill defined. But the vagaries
that he cites do not upset the proof in question, which, both by its physical
formulation and by explicit identification, specify the framework to be used.
Griffiths confirms the validity of the proof insofar as that framework is used.
The section also shows, in response to Griffiths' challenge, why a putative
proof of locality that he has described is flawed.
| arxiv topic:quant-ph |
arxiv_dataset-30371111.5464 | The Origin of Type I Spicule Oscillations
astro-ph.SR
We use images of high spatial and temporal resolution, obtained with the
Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar
Telescope, to reveal how the generation of transverse waves in Type I spicules
is a direct result of longitudinal oscillations occurring in the photosphere.
Here we show how pressure oscillations, with periodicities in the range 130 -
440 s, manifest in small-scale photospheric magnetic bright points, and
generate kink waves in the Sun's outer atmosphere with transverse velocities
approaching the local sound speed. Through comparison of our observations with
advanced two-dimensional magneto-hydrodynamic simulations, we provide evidence
for how magnetoacoustic oscillations, generated at the solar surface, funnel
upwards along Type I spicule structures, before undergoing
longitudinal-to-transverse mode conversion into waves at twice the initial
driving frequency. The resulting kink modes are visible in chromospheric
plasma, with periodicities of 65 -220 s, and amplitudes often exceeding 400 km.
A sausage mode oscillation also arises as a consequence of the photospheric
driver, which is visible in both simulated and observational time series. We
conclude that the mode conversion and period modification is a direct
consequence of the 90 degree phase shift encompassing opposite sides of the
photospheric driver. The chromospheric energy flux of these waves are estimated
to be approximately 300,000 W/m^2, which indicates that they are sufficiently
energetic to accelerate the solar wind and heat the localized corona to its
multi-million degree temperatures.
| arxiv topic:astro-ph.SR |
arxiv_dataset-30381111.5564 | Siphon flow in a cool magnetic loop
astro-ph.SR
We investigate the properties of a structure in the solar chromosphere in an
active region to find out whether the feature is consistent with a siphon flow
in a magnetic loop filled with chromospheric material.
| arxiv topic:astro-ph.SR |
arxiv_dataset-30391111.5664 | Dynamical Degrees, Arithmetic Degrees, and Canonical Heights for
Dominant Rational Self-Maps of Projective Space
math.NT math.DS
Let F : P^N --> P^N be a dominant rational map. The dynamical degree of F is
the quantity d_F = lim (deg F^n)^(1/n). When F is defined over a number field,
we define the arithmetic degree of an algebraic point P to be a_F(P) = limsup
h(F^n(P))^(1/n) and the canonical height of P to be h_F(P) = limsup
h(F^n(P))/n^k d_F^n for an appropriately chosen integer k = k_F. In this
article we prove some elementary relations and make some deep conjectures
relating d_F, a_F(P), and h_F(P). We prove our conjectures for monomial maps.
| arxiv topic:math.NT math.DS |
arxiv_dataset-30401111.5764 | Back Reaction from Walls
astro-ph.CO gr-qc
We study the distance-redshift relation in a universe filled with 'walls' of
pressure-less dust separated by under dense regions. We show that as long as
the density contrast of the walls is small, or the diameter of the under dense
regions is much smaller than the Hubble scale, the distance-redshift relation
remains close to what is obtained in a Friedmann universe. However, when
arbitrary density contrasts are allowed, every prescribed distance-redshift
relation can be reproduced with such models.
| arxiv topic:astro-ph.CO gr-qc |
arxiv_dataset-30411111.5864 | On Metric Dimension of Functigraphs
math.CO
The \emph{metric dimension} of a graph $G$, denoted by $\dim(G)$, is the
minimum number of vertices such that each vertex is uniquely determined by its
distances to the chosen vertices. Let $G_1$ and $G_2$ be disjoint copies of a
graph $G$ and let $f: V(G_1) \rightarrow V(G_2)$ be a function. Then a
\emph{functigraph} $C(G, f)=(V, E)$ has the vertex set $V=V(G_1) \cup V(G_2)$
and the edge set $E=E(G_1) \cup E(G_2) \cup \{uv \mid v=f(u)\}$. We study how
metric dimension behaves in passing from $G$ to $C(G,f)$ by first showing that
$2 \le \dim(C(G, f)) \le 2n-3$, if $G$ is a connected graph of order $n \ge 3$
and $f$ is any function. We further investigate the metric dimension of
functigraphs on complete graphs and on cycles.
| arxiv topic:math.CO |
arxiv_dataset-30421111.5964 | Teleporting the one-qubit state via two-level atoms with spontaneous
emission
quant-ph
We study quantum teleportation via two two-level atoms coupled collectively
to a multimode vacuum field and prepared initially in different atomic states.
We concentrated on influence of the spontaneous emission, collective damping
and dipole-dipole interaction of the atoms on fidelity dynamics of quantum
teleportation and obtained the region of spatial distance between the two atoms
over which the state can be teleported nonclassically. Moreover, we showed
through concrete examples that entanglement of the channel state is the
prerequisite but not the only essential quantity for predicting the
teleportation fidelity.
| arxiv topic:quant-ph |
arxiv_dataset-30431111.6064 | Two-potential theory of electric and magnetic charges via duality
transformation
hep-th
Dirac, Schwinger and Zwanziger theories of electric and magnetic charges are
obtained via duality transformation. Analogous construction for three Euclidean
dimensions, with magnetic charges interacting with electric currents, is also
done. The role of Dirac strings as dislocations in the configurations of gauge
potential is emphasized.
| arxiv topic:hep-th |
arxiv_dataset-30441111.6164 | Standing genetic variation and the evolution of drug resistance in HIV
q-bio.PE q-bio.GN
Drug resistance remains a major problem for the treatment of HIV. Resistance
can occur due to mutations that were present before treatment starts or due to
mutations that occur during treatment. The relative importance of these two
sources is unknown. We study three different situations in which HIV drug
resistance may evolve: starting triple-drug therapy, treatment with a single
dose of nevirapine and interruption of treatment. For each of these three cases
good data are available from literature, which allows us to estimate the
probability that resistance evolves from standing genetic variation. Depending
on the treatment we find probabilities of the evolution of drug resistance due
to standing genetic variation between 0 and 39%. For patients who start
triple-drug combination therapy, we find that drug resistance evolves from
standing genetic variation in approximately 6% of the patients. We use a
population-dynamic and population-genetic model to understand the observations
and to estimate important evolutionary parameters. We find that both, the
effective population size of the virus before treatment, and the fitness of the
resistant mutant during treatment, are key-parameters that determine the
probability that resistance evolves from standing genetic variation.
Importantly, clinical data indicate that both of these parameters can be
manipulated by the kind of treatment that is used.
| arxiv topic:q-bio.PE q-bio.GN |
arxiv_dataset-30451111.6264 | Revisiting the pure annihilation decays $B_s\to \pi^+ \pi^-$ and $B^0
\to K^+ K^-$: the data and the pQCD predictions
hep-ph hep-ex
In this work, we recalculate the charmless pure annihilation decays $B_s\to
\pi^+ \pi^-$ and $B^0 \to K^+ K^-$ by using the perturbative QCD (pQCD)
factorization approach, and compare the pQCD predictions with currently
available experimental measurements. We used the same set of relevant input
parameters and wave functions to make the calculations for the considered decay
modes and found the following results: (a) one can provide a consistent pQCD
interpretation for both the measured $Br(B_s^0 \to \pi^+ \pi^-)$ and $Br(B_d^0
\to K^+ K^-)$ simultaneously; (b) the pQCD predictions for $Br(B_s^0 \to
\pi^+\pi^-)$ obtained by different authors are well consistent with each other;
(c) our new pQCD prediction for $Br(B_d^0 \to K^+K^-)$ agree very well with the
measured values from CDF and LHCb Collaboration; and (d) the CP-violating
asymmetry ${\cal A}_{CP}(B_d^0 \to K^+K^-) \approx 16%$, which is large and may
be detected at the LHCb experiment.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-30461111.6364 | On the first eigenvalue of the Witten-Laplacian and the diameter of
compact shrinking Ricci solitons
math.DG
We prove a lower bound estimate for the first non-zero eigenvalue of the
Witten-Laplacian on compact Riemannian manifolds. As an application, we derive
a lower bound estimate for the diameter of compact gradient shrinking Ricci
solitons. Our results improve some previous estimates which were obtained by
the first author and Y. Sano in [12], and by B. Andrews and L. Ni in [1].
Moreover, we extend the diameter estimate to compact self-similar shrinkers of
mean curvature flow.
| arxiv topic:math.DG |
arxiv_dataset-30471111.6464 | Very Low-Mass Stars: structural and evolutionary properties
astro-ph.SR
We briefly review the main physical and structural properties of Very
Low-Mass stars. The most important improvements in the physical inputs required
for the stellar models computations are also discussed. We show some
comparisons with observational measurements concerning both the Color-Magnitude
diagrams, mass-luminosity relations and mass-radius one, in order to disclose
the level of agreement between the present theoretical framework and
observations.
| arxiv topic:astro-ph.SR |
arxiv_dataset-30481111.6564 | Comment on "Reversed gravitational acceleration...", arXiv:1102.2870v2
gr-qc
Hilbert's 1917 discovery of reversed gravitational acceleration is discussed,
and the connection to arXiv:1102.2870v2 [gr-qc] is explained.
| arxiv topic:gr-qc |
arxiv_dataset-30491111.6664 | Generalized Orthogonal Matching Pursuit
cs.IT math.IT
As a greedy algorithm to recover sparse signals from compressed measurements,
orthogonal matching pursuit (OMP) algorithm has received much attention in
recent years. In this paper, we introduce an extension of the OMP for pursuing
efficiency in reconstructing sparse signals. Our approach, henceforth referred
to as generalized OMP (gOMP), is literally a generalization of the OMP in the
sense that multiple $N$ indices are identified per iteration. Owing to the
selection of multiple ''correct'' indices, the gOMP algorithm is finished with
much smaller number of iterations when compared to the OMP. We show that the
gOMP can perfectly reconstruct any $K$-sparse signals ($K > 1$), provided that
the sensing matrix satisfies the RIP with $\delta_{NK} <
\frac{\sqrt{N}}{\sqrt{K} + 3 \sqrt{N}}$. We also demonstrate by empirical
simulations that the gOMP has excellent recovery performance comparable to
$\ell_1$-minimization technique with fast processing speed and competitive
computational complexity.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-30501111.6764 | Trigger and Aperture of the Surface Detector Array of the Pierre Auger
Observatory
astro-ph.IM
The surface detector array of the Pierre Auger Observatory consists of 1600
water-Cherenkov detectors, for the study of extensive air showers (EAS)
generated by ultra-high-energy cosmic rays. We describe the trigger hierarchy,
from the identification of candidate showers at the level of a single detector,
amongst a large background (mainly random single cosmic ray muons), up to the
selection of real events and the rejection of random coincidences. Such trigger
makes the surface detector array fully efficient for the detection of EAS with
energy above $3\times 10^{18}$ eV, for all zenith angles between 0$^\circ$ and
60$^\circ$, independently of the position of the impact point and of the mass
of the primary particle. In these range of energies and angles, the exposure of
the surface array can be determined purely on the basis of the geometrical
acceptance.
| arxiv topic:astro-ph.IM |
arxiv_dataset-30511111.6864 | Electronic properties of layered multicomponent wide-bandgap oxides: a
combinatorial approach
cond-mat.mtrl-sci
The structural, electronic, and optical properties of twelve multicomponent
oxides with layered structure, RAMO$_4$, where R$^{3+}$=In or Sc; A$^{3+}$=Al
or Ga; and M$^{2+}$=Ca, Cd, Mg, or Zn, are investigated using first-principles
density functional approach. The compositional complexity of RAMO$_4$ leads to
a wide range of band gap values varying from 2.45 eV for InGaCdO$_4$ to 6.29 eV
for ScAlMgO$_4$. Strikingly, despite the different band gaps in the oxide
constituents, namely, 2-4 eV in CdO, In$_2$O$_3$, or ZnO; 5-6 for Ga$_2$O$_3$
or Sc$_2$O$_3$; and 7-9 eV in CaO, MgO, or Al$_2$O$_3$, the bottom of the
conduction band in the multicomponent oxides is formed from the s-states of all
cations and their neighboring oxygen p-states. We show that the hybrid nature
of the conduction band in multicomponent oxides originates from the unusual
five-fold atomic coordination of A$^{3+}$ and M$^{2+}$ cations which enables
the interaction between the spatially-spread s-orbitals of adjacent cations via
shared oxygen atoms. The effect of the local atomic coordination on the band
gap, the electron effective mass, the orbital composition of the conduction
band, and the expected (an)isotropic character of the electron transport in
layered RAMO$_4$ is thoroughly discussed.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-30521111.6964 | Event-driven Monte Carlo algorithm for general potentials
cond-mat.stat-mech cond-mat.soft physics.comp-ph
We extend the event-chain Monte Carlo algorithm from hard-sphere interactions
to the micro-canonical ensemble (constant potential energy) for general
potentials. This event-driven Monte Carlo algorithm is non-local,
rejection-free, and allows for the breaking of detailed balance. The algorithm
uses a discretized potential, but its running speed is asymptotically
independent of the discretization. We implement the algorithm for the cut-off
linear potential, and discuss its possible implementation directly in the
continuum limit.
| arxiv topic:cond-mat.stat-mech cond-mat.soft physics.comp-ph |
arxiv_dataset-30531111.7064 | Correlation Decay up to Uniqueness in Spin Systems
cs.DS
We give a complete characterization of the two-state anti-ferromagnetic spin
systems which are of strong spatial mixing on general graphs. We show that a
two-state anti-ferromagnetic spin system is of strong spatial mixing on all
graphs of maximum degree at most $\Delta$ if and only if the system has a
unique Gibbs measure on infinite regular trees of degree up to $\Delta$, where
$\Delta$ can be either bounded or unbounded. As a consequence, there exists an
FPTAS for the partition function of a two-state anti-ferromagnetic spin system
on graphs of maximum degree at most $\Delta$ when the uniqueness condition is
satisfied on infinite regular trees of degree up to $\Delta$. In particular, an
FPTAS exists for arbitrary graphs if the uniqueness is satisfied on all
infinite regular trees. This covers as special cases all previous algorithmic
results for two-state anti-ferromagnetic systems on general-structure graphs.
Combining with the FPRAS for two-state ferromagnetic spin systems of
Jerrum-Sinclair and Goldberg-Jerrum-Paterson, and the hardness results of
Sly-Sun and independently of Galanis-Stefankovic-Vigoda, this gives a complete
classification, except at the phase transition boundary, of the approximability
of all two-state spin systems, on either degree-bounded families of graphs or
family of all graphs.
| arxiv topic:cs.DS |
arxiv_dataset-30541111.7164 | PARIS: Probabilistic Alignment of Relations, Instances, and Schema
cs.DB
One of the main challenges that the Semantic Web faces is the integration of
a growing number of independently designed ontologies. In this work, we present
PARIS, an approach for the automatic alignment of ontologies. PARIS aligns not
only instances, but also relations and classes. Alignments at the instance
level cross-fertilize with alignments at the schema level. Thereby, our system
provides a truly holistic solution to the problem of ontology alignment. The
heart of the approach is probabilistic, i.e., we measure degrees of matchings
based on probability estimates. This allows PARIS to run without any parameter
tuning. We demonstrate the efficiency of the algorithm and its precision
through extensive experiments. In particular, we obtain a precision of around
90% in experiments with some of the world's largest ontologies.
| arxiv topic:cs.DB |
arxiv_dataset-30551111.7264 | Neutrino Cosmology after WMAP and LHC7
hep-ph astro-ph.CO gr-qc
The gauge-extended U(1)_C \times SU(2)_L \times U(1)_{I_R} \times U(1)_L
model has the attractive property of elevating the two major global symmetries
of the standard model (baryon number B and lepton number L) to local gauge
symmetries. The U(1)_L symmetry prevents the generation of Majorana masses,
leading to three superweakly interacting right-handed neutrinos. This also
renders a B-L symmetry non-anomalous. We show that the superweak interactions
of these Dirac states (through their coupling to the TeV-scale B-L gauge boson)
permit right-handed neutrino decoupling just above the QCD phase transition:
175 MeV < T_{\nu_R}^{dec} < 250 MeV. In this transitional region, the residual
temperature ratio between \nu_L and \nu_R generates extra relativistic degrees
of freedom at BBN and at the CMB epochs. Consistency (within 1\sigma) with both
WMAP 7-year data and the most recent estimate of the primordial ^4He mass
fraction is achieved for 3 TeV < M_{B-L} < 6 TeV. The model is fully
predictive, and can be confronted with dijet and dilepton data (or lack
thereof) from LHC7 and, eventually, LHC14.
| arxiv topic:hep-ph astro-ph.CO gr-qc |
arxiv_dataset-30561112.0045 | CytoITMprobe: a network information flow plugin for Cytoscape
q-bio.QM cs.DB q-bio.MN
To provide the Cytoscape users the possibility of integrating ITM Probe into
their workflows, we developed CytoITMprobe, a new Cytoscape plugin.
CytoITMprobe maintains all the desirable features of ITM Probe and adds
additional flexibility not achievable through its web service version. It
provides access to ITM Probe either through a web server or locally. The input,
consisting of a Cytoscape network, together with the desired origins and/or
destinations of information and a dissipation coefficient, is specified through
a query form. The results are shown as a subnetwork of significant nodes and
several summary tables. Users can control the composition and appearance of the
subnetwork and interchange their ITM Probe results with other software tools
through tab-delimited files.
The main strength of CytoITMprobe is its flexibility. It allows the user to
specify as input any Cytoscape network, rather than being restricted to the
pre-compiled protein-protein interaction networks available through the ITM
Probe web service. Users may supply their own edge weights and
directionalities. Consequently, as opposed to ITM Probe web service,
CytoITMprobe can be applied to many other domains of network-based research
beyond protein-networks. It also enables seamless integration of ITM Probe
results with other Cytoscape plugins having complementary functionality for
data analysis.
| arxiv topic:q-bio.QM cs.DB q-bio.MN |
arxiv_dataset-30571112.0145 | Finite-temperature phase structures of hard-core bosons in an optical
lattice with an effective magnetic field
cond-mat.quant-gas cond-mat.stat-mech
We study finite-temperature phase structures of hard-core bosons in a
two-dimensional optical lattice subject to an effective magnetic field by
employing the gauged CP$^1$ model. Based on the extensive Monte Carlo
simulations, we study their phase structures at finite temperatures for several
values of the magnetic flux per plaquette of the lattice and mean particle
density. Despite the presence of the particle number fluctuation, the
thermodynamic properties are qualitatively similar to those of the frustrated
XY model with only the phase as a dynamical variable. This suggests that cold
atom simulators of the frustrated XY model are available irrespective of the
particle filling at each site.
| arxiv topic:cond-mat.quant-gas cond-mat.stat-mech |
arxiv_dataset-30581112.0245 | Simultaneous PQ-Ordering with Applications to Constrained Embedding
Problems
cs.DS cs.DM
In this paper, we define and study the new problem Simultaneous PQ-Ordering.
Its input consists of a set of PQ-trees, which represent sets of circular
orders of their leaves, together with a set of child-parent relations between
these PQ-trees, such that the leaves of the child form a subset of the leaves
of the parent. Simultaneous PQ-Ordering asks whether orders of the leaves of
each of the trees can be chosen simultaneously, that is, for every child-parent
relation the order chosen for the parent is an extension of the order chosen
for the child. We show that Simultaneous PQ-Ordering is NP-complete in general
and that it is efficiently solvable for a special subset of instances, the
2-fixed instances. We then show that several constrained embedding problems can
be formulated as such 2-fixed instances.
In particular, we obtain a linear-time algorithm for Partially PQ-Constrained
Planarity for biconnected graphs, a common generalization of two recently
considered embedding problems, and a quadratic-time algorithm for Simultaneous
Embedding with Fixed Edges for biconnected graphs with a connected
intersection; formerly only the much more restricted case that the intersection
is biconnected was known to be efficiently solvable. Both results can be
extended to the case where the input graphs are not necessarily biconnected but
have the property that each cutvertex is contained in at most two non-trivial
blocks. This includes for example the case where both graphs have maximum
degree 5. Moreover, we give an optimal linear-time algorithm for recognition of
simultaneous interval graphs, improving upon a recent O(n^2 log n)-time
algorithm due to Jampani and Lubiw and show that this can be used to also solve
the problem of extending partial interval representations of graphs with n
vertices and m edges in time O(n + m), improving a recent result of Klav\'ik et
al.
| arxiv topic:cs.DS cs.DM |
arxiv_dataset-30591112.0345 | Top quark physics at CDF
hep-ex
We present the recent results of top-quark physics using up to 6 fb$^{-1}$ of
$p\bar{p}$ collisions analyzed by the CDF collaboration. The large number of
top quark events analyzed, of the order of several thousands, allows stringent
checks of the standard model predictions. Also, the top quark is widely
believed to be a window to new physics. We present the latest measurements of
top quark intrinsic properties as well as direct searches for new physics in
the top sector.
| arxiv topic:hep-ex |
arxiv_dataset-30601112.0445 | Phenomenology of neutrino mixing in vacuum and matter
hep-ph
Neutrino oscillation is the new physics beyond standard model. In this paper
we have revisited the issue of neutrino oscillation in simple and delicate
manner. Starting from the fundamental quantum mechanical treatment for the
neutrinos, we calculated the probabilities for the neutrino oscillating within
three flavors. Normal and inverted hierarchy have been taken into account for
the solar and atmospheric cases, in vacuum and matter. The probabilities have
been plotted for all the cases and discussed.
| arxiv topic:hep-ph |
arxiv_dataset-30611112.0545 | Uncovering Local Absorbed Active Galactic Nuclei with Swift and Suzaku
astro-ph.HE astro-ph.CO
Detection of absorbed active galactic nuclei and their properties remains an
elusive and important problem in understanding the evolution and activation of
black holes. With the very hard X-ray survey conducted by Swift's Burst Alert
Telescope - the first all-sky survey in 30 years - we are beginning to uncover
the characteristics of obscured AGN. The synergy between Suzaku and Swift has
been crucial in pinning down the X-ray properties of newly detected heavily
obscured but bright hard X-ray sources. We review the X-ray and optical
spectroscopic properties of obscured AGN in the local Universe, as detected in
the Swift survey. We discuss the relative distribution of absorbed/unabsorbed
sources, including "hidden" and Compton thick AGN populations. Among the
results from the survey, we find that absorbed AGN are less luminous than
unabsorbed sources. Optical spectra reveal that sources with emission line
ratios indicative of LINERs/H II galaxies/composites are the least luminous
objects in the sample, while optical absorbed and unabsorbed Seyferts have the
same luminosity distributions. Thus, the least luminous sources are likely
accreting in a different mode than the Seyferts.
| arxiv topic:astro-ph.HE astro-ph.CO |
arxiv_dataset-30621112.0645 | Probing the quantum behaviors of a nanomechanical resonator coupled to a
double quantum dot
cond-mat.mes-hall quant-ph
We propose a current correlation spectrum approach to probe the quantum
behaviors of a nanome-chanical resonator (NAMR). The NAMR is coupled to a
double quantum dot (DQD), which acts as a quantum transducer and is further
coupled to a quantum-point contact (QPC). By measuring the current correlation
spectrum of the QPC, shifts in the DQD energy levels, which depend on the
phonon occupation in the NAMR, are determined. Quantum behaviors of the NAMR
could, thus, be observed. In particular, the cooling of the NAMR into the
quantum regime could be examined. In addition, the effects of the coupling
strength between the DQD and the NAMR on these energy shifts are studied. We
also investigate the impacts on the current correlation spectrum of the QPC due
to the backaction from the charge detector on the DQD.
| arxiv topic:cond-mat.mes-hall quant-ph |
arxiv_dataset-30631112.0745 | The Imprint of the Baryon Acoustic Oscillations (BAO) in the
Cross-correlation of the Redshifted HI 21-cm Signal and the Ly-alpha Forest
astro-ph.CO
The cross-correlation of the Ly-alpha forest and redshifted 21-cm emission
has recently been proposed as an observational tool for mapping out the
large-scale structures in the post-reionization era z < 6. This has a
significant advantage as the problems of continuum subtraction and foreground
removal are expected to be considerably less severe in comparison to the
respective auto-correlation signals. Further, the effect of discrete quasar
sampling is less severe for the cross-correlation in comparison to the Ly-alpha
forest auto-correlation signal. In this paper we explore the possibility of
using the cross-correlation signal to detect the baryon acoustic oscillation
(BAO). To this end, we have developed a theoretical formalism to calculate the
expected cross-correlation signal and its variance. We have used this to
predict the expected signal, and estimate the range of observational parameters
where a detection is possible.
For the Ly-$\alpha$ forest, we have considered BOSS and BIGBOSS which are
expected have a quasar density of 16 deg^{-2} and 64 deg^{-2} respectively. A
radio interferometric array that covers the redshift range z=2 to 3 using
antennas of size 2 m * 2 m, is well suited for the 21-cm observations. It is
required to observe 25 independent fields of view, which corresponds to the
entire angular extent of BOSS. We find that it is necessary to achieve a noise
level of 1.1 * 10^{-5} K^2 and 6.25 * 10^{-6} mK^2 per field of view in the
21-cm observations to detect the angular and radial BAO respectively with BOSS.
The corresponding figures are 3.3 * 10^{-5} mK^2 and 1.7 * 10^{-5} mK^2 for
BIGBOSS. Four to five independent radio interferometric arrays, each containing
400 antennas uniformly sampling all the baselines within 50 m will be able to
carry out these observations in the span of a few years.
| arxiv topic:astro-ph.CO |
arxiv_dataset-30641112.0845 | Knottedness is in NP, modulo GRH
math.GT cs.CC
Given a tame knot K presented in the form of a knot diagram, we show that the
problem of determining whether K is knotted is in the complexity class NP,
assuming the generalized Riemann hypothesis (GRH). In other words, there exists
a polynomial-length certificate that can be verified in polynomial time to
prove that K is non-trivial. GRH is not needed to believe the certificate, but
only to find a short certificate. This result complements the result of Hass,
Lagarias, and Pippenger that unknottedness is in NP. Our proof is a corollary
of major results of others in algebraic geometry and geometric topology.
| arxiv topic:math.GT cs.CC |
arxiv_dataset-30651112.0945 | Interleaved Product LDPC Codes
cs.IT math.IT
Product LDPC codes take advantage of LDPC decoding algorithms and the high
minimum distance of product codes. We propose to add suitable interleavers to
improve the waterfall performance of LDPC decoding. Interleaving also reduces
the number of low weight codewords, that gives a further advantage in the error
floor region.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-30661112.1045 | Non-Malleable Extractors, Two-Source Extractors and Privacy
Amplification
cs.CR cs.CC
Dodis and Wichs introduced the notion of a non-malleable extractor to study
the problem of privacy amplification with an active adversary. A non-malleable
extractor is a much stronger version of a strong extractor. Previously, there
are only two known constructions of non-malleable extractors. Both
constructions only work for (n, k)-sources with k>n/2. Interestingly, both
constructions are also two-source extractors.
In this paper, we present a strong connection between non-malleable
extractors and two-source extractors. The first part of the connection shows
that non-malleable extractors can be used to construct two-source extractors.
With appropriate parameters the resulted two-source extractor beats the best
known construction of two-source extractors. This partially explains why
previous constructions of non-malleable extractors only work for sources with
entropy rate >1/2, and why explicit non-malleable extractors for small
min-entropy may be hard to get. The second part of the connection shows that
certain two-source extractors can be used to construct non-malleable
extractors. Using this connection, we obtain the first construction of
non-malleable extractors for k < n/2. Specifically, we give an unconditional
construction for min-entropy k=(1/2-\delta)n for some constant \delta>0, and a
conditional (semi-explicit) construction that can potentially achieve k=\alpha
n for any constant \alpha>0.
Finally, despite the lack of explicit non-malleable extractors for
arbitrarily linear entropy, we give the first 2-round privacy amplification
protocol with asymptotically optimal entropy loss and communication complexity
for (n, k) sources with k=\alpha n for any constant \alpha>0. This dramatically
improves previous results and answers an open problem in \cite{DLWZ11}.
| arxiv topic:cs.CR cs.CC |
arxiv_dataset-30671112.1145 | The Lower Bounds for Eigenvalues of Elliptic Operators --By
Nonconforming Finite Element Methods
math.NA math.AP
The aim of the paper is to introduce a new systematic method that can produce
lower bounds for eigenvalues. The main idea is to use nonconforming finite
element methods. The general conclusion herein is that if local approximation
properties of nonconforming finite element spaces $V_h$ are better than global
continuity properties of $V_h$, corresponding methods will produce lower bounds
for eigenvalues. More precisely, under three conditions on continuity and
approximation properties of nonconforming finite element spaces we first show
abstract error estimates of approximate eigenvalues and eigenfunctions.
Subsequently, we propose one more condition and prove that it is sufficient to
guarantee nonconforming finite element methods to produce lower bounds for
eigenvalues of symmetric elliptic operators. As one application, we show that
this condition hold for most nonconforming elements in literature. As another
important application, this condition provides a guidance to modify known
nonconforming elements in literature and to propose new nonconforming elements.
In fact, we enrich locally the Crouzeix-Raviart element such that the new
element satisfies the condition; we propose a new nonconforming element for
second order elliptic operators and prove that it will yield lower bounds for
eigenvalues. Finally, we prove the saturation condition for most nonconforming
elements.
| arxiv topic:math.NA math.AP |
arxiv_dataset-30681112.1245 | A spectral sequence for parallelized persistence
cs.CG cs.DC math.AT
We approach the problem of the computation of persistent homology for large
datasets by a divide-and-conquer strategy. Dividing the total space into
separate but overlapping components, we are able to limit the total memory
residency for any part of the computation, while not degrading the overall
complexity much. Locally computed persistence information is then merged from
the components and their intersections using a spectral sequence generalizing
the Mayer-Vietoris long exact sequence.
We describe the Mayer-Vietoris spectral sequence and give details on how to
compute with it. This allows us to merge local homological data into the global
persistent homology. Furthermore, we detail how the classical topology
constructions inherent in the spectral sequence adapt to a persistence
perspective, as well as describe the techniques from computational commutative
algebra necessary for this extension.
The resulting computational scheme suggests a parallelization scheme, and we
discuss the communication steps involved in this scheme. Furthermore, the
computational scheme can also serve as a guideline for which parts of the
boundary matrix manipulation need to co-exist in primary memory at any given
time allowing for stratified memory access in single-core computation. The
spectral sequence viewpoint also provides easy proofs of a homology nerve lemma
as well as a persistent homology nerve lemma. In addition, the algebraic tools
we develop to approch persistent homology provide a purely algebraic
formulation of kernel, image and cokernel persistence (D. Cohen-Steiner, H.
Edelsbrunner, J. Harer, and D. Morozov. Persistent homology for kernels,
images, and cokernels. In Proceedings of the twentieth Annual ACM-SIAM
Symposium on Discrete Algorithms, pages 1011-1020. Society for Industrial and
Applied Mathematics, 2009.)
| arxiv topic:cs.CG cs.DC math.AT |
arxiv_dataset-30691112.1345 | Self-consistent tilted-axis-cranking study of triaxial strongly deformed
bands in $^{158}$Er at ultrahigh spin
nucl-th
Stimulated by recent experimental discoveries, triaxial strongly deformed
(TSD) states in $^{158}$Er at ultrahigh spins have been studied by means of the
Skyrme-Hartree-Fock model and the tilted-axis-cranking method. Restricting the
rotational axis to one of the principal axes -- as done in previous cranking
calculations -- two well-defined TSD minima in the total Routhian surface are
found for a given configuration: one with positive and another with negative
triaxial deformation $\gamma$. By allowing the rotational axis to change
direction, the higher-energy minimum is shown to be a saddle point. This
resolves the long-standing question of the physical interpretation of the two
triaxial minima at a very similar quadrupole shape obtained in the principal
axis cranking approach. Several TSD configurations have been predicted,
including a highly deformed band expected to cross lesser elongated TSD bands
at the highest spins. Its transitional quadrupole moment $Q_t \approx 10.5$\,eb
is close to the measured value of $\sim$11\,eb; hence, it is a candidate for
the structure observed in experiment.
| arxiv topic:nucl-th |
arxiv_dataset-30701112.1445 | A cohomological interpretation of Bogomolov's instability
math.AG
We give a new proof of Bogomolov's instability theorem. Furthermore we prove
that it is equivalent to a statement which characterizes when the first
cohomology group of a suitable divisor does not vanish.
| arxiv topic:math.AG |
arxiv_dataset-30711112.1545 | Oriented paths in n-chromatic digraphs
math.CO
In this thesis, we try to treat the problem of oriented paths in n-chromatic
digraphs. We first treat the case of antidirected paths in 5-chromatic
digraphs, where we explain El-Sahili's theorem and provide an elementary and
shorter proof of it. We then treat the case of paths with two blocks in
n-chromatic digraphs with n greater than 4, where we explain the two different
approaches of Addario-Berry et al. and of El-Sahili. We indicate a mistake in
Addario-Berry et al.'s proof and provide a correction for it.
| arxiv topic:math.CO |
arxiv_dataset-30721112.1645 | How to Gamble If You're In a Hurry
math.PR cs.GT
The beautiful theory of statistical gambling, started by Dubins and Savage
(for subfair games) and continued by Kelly and Breiman (for superfair games)
has mostly been studied under the unrealistic assumption that we live in a
continuous world, that money is indefinitely divisible, and that our life is
indefinitely long. Here we study these fascinating problems from a purely
discrete, finitistic, and computational, viewpoint, using Both Symbol-Crunching
and Number-Crunching (and simulation just for checking purposes).
| arxiv topic:math.PR cs.GT |
arxiv_dataset-30731112.1745 | Measurement Error Models in Astronomy
astro-ph.IM physics.data-an
I discuss the effects of measurement error on regression and density
estimation. I review the statistical methods that have been developed to
correct for measurement error that are most popular in astronomical data
analysis, discussing their advantages and disadvantages. I describe functional
models for accounting for measurement error in regression, with emphasis on the
methods of moments approach and the modified loss function approach. I then
describe structural models for accounting for measurement error in regression
and density estimation, with emphasis on maximum-likelihood and Bayesian
methods. As an example of a Bayesian application, I analyze an astronomical
data set subject to large measurement errors and a non-linear dependence
between the response and covariate. I conclude with some directions for future
research.
| arxiv topic:astro-ph.IM physics.data-an |
arxiv_dataset-30741112.1845 | Circumstellar disks in binary star systems
astro-ph.EP
In this paper we study the evolution of viscous and radiative circumstellar
disks under the influence of a companion star. We focus on the eccentric
{\gamma} Cephei and {\alpha} Centauri system as examples and compare the disk
quantities such as disk eccentricity and precession rate to previous isothermal
simulations. We perform two-dimensional hydrodynamical simulations of the
binary star systems under the assumption of coplanarity of the disk, host star
and binary companion. We use the grid-based, staggered mesh code FARGO with an
additional energy equation to which we added radiative cooling based on opacity
tables. The eccentric binary companion perturbs the disk around the primary
star periodically. Upon passing periastron spirals arms are induced that wind
from the outer disk towards the star. In isothermal simulations this results in
disk eccentricities up to {\epsilon}_disk ~ 0.2, but in more realistic
radiative models we obtain much smaller eccentricities of about {\epsilon}_disk
~ 0.04 - 0.06 with no real precession. Models with varying viscosity and disk
mass indicate show that disks with less mass have lower temperatures and higher
disk eccentricity. The rather large high disk eccentricities, as indicated in
previous isothermal disk simulations, implied a more difficult planet formation
in the {\gamma} Cephei system due to the enhanced collision velocities of
planetesimals. We have shown that under more realistic conditions with
radiative cooling the disk become less eccentric and thus planet formation may
be made easier. However, we estimate that the viscosity in the disk has to very
small, with {\alpha} \lesssim 0.001, because otherwise the disk's lifetime will
be too short to allow planet formation to occur along the core instability
scenario. We estimate that the periodic heating of the disk in eccentric
binaries will be observable in the mid-IR regime.
| arxiv topic:astro-ph.EP |
arxiv_dataset-30751112.1945 | Approximation Algorithms for Edge Partitioned Vertex Cover Problems
cs.DS
We consider a natural generalization of the Partial Vertex Cover problem.
Here an instance consists of a graph G = (V,E), a positive cost function c: V->
Z^{+}, a partition $P_1,..., P_r$ of the edge set $E$, and a parameter $k_i$
for each partition $P_i$. The goal is to find a minimum cost set of vertices
which cover at least $k_i$ edges from the partition $P_i$. We call this the
Partition Vertex Cover problem. In this paper, we give matching upper and lower
bound on the approximability of this problem. Our algorithm is based on a novel
LP relaxation for this problem. This LP relaxation is obtained by adding
knapsack cover inequalities to a natural LP relaxation of the problem. We show
that this LP has integrality gap of $O(log r)$, where $r$ is the number of sets
in the partition of the edge set. We also extend our result to more general
settings.
| arxiv topic:cs.DS |
arxiv_dataset-30761112.2045 | Interfacial coupling across a modified interface studied with
ferromagnetic resonance
cond-mat.mes-hall
Using spin waves we directly probe the interface of an exchange biased
Ni$_{80}$Fe$_{20}$/Ir$_{25}$Mn$_{75}$ film which has been modified by the
presence of an Au dusting layer. Combining this experimental data with a
discretised simulation model, parameters relating to interface exchange
coupling and modification of interface magnetisation are determined. Exchange
coupling is found to be relatively uniform as gold thickness is increased, and
undergoes a sudden drop at 1.5$\textrm{\AA}$ of gold. Interface magnetisation
decreases as a function of the gold dusting thickness. Antiparallel alignment
of the ferromagnet and antiferromagnet supress the interface magnetisation
compared to when they are in parallel alignment. These findings imply that the
interface region has specific magnetisation states which depend on the
ferromagnet orientation.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-30771112.2145 | Anomaly of Film Porosity Dependence on Deposition Rate
cond-mat.mtrl-sci
This Letter reports an anomaly of film porosity dependence on deposition rate
during physical vapor deposition - the porosity increases as deposition rate
decreases. Using glancing angle deposition of Cu on SiO2 substrate, the authors
show that the Cu film consists of well separated nanorods when the deposition
rate is 1 nm/second, and that the Cu films consists of a more uniform (or lower
porosity) film when the deposition rate is 6 nm/second; all other deposition
conditions remain the same. This anomaly is the result of interplay among
substrate non-wetting, density of Cu nuclei on the substrate, and the minimum
diameter of nanorods.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-30781112.2245 | Decryptable to Your Eyes: Visualization of Security Protocols at the
User Interface
cs.CR
The design of authentication protocols, for online banking services in
particular and any service that is of sensitive nature in general, is quite
challenging. Indeed, enforcing security guarantees has overhead thus imposing
additional computation and design considerations that do not always meet
usability and user requirements. On the other hand, relaxing assumptions and
rigorous security design to improve the user experience can lead to security
breaches that can harm the users' trust in the system.
In this paper, we demonstrate how careful visualization design can enhance
not only the security but also the usability of the authentication process. To
that end, we propose a family of visualized authentication protocols, a
visualized transaction verification, and a "decryptable to your eyes only"
protocol. Through rigorous analysis, we verify that our protocols are immune to
many of the challenging authentication attacks applicable in the literature.
Furthermore, using an extensive case study on a prototype of our protocols, we
highlight the potential of our approach for real-world deployment: we were able
to achieve a high level of usability while satisfying stringent security
requirements.
| arxiv topic:cs.CR |
arxiv_dataset-30791112.2345 | Gluonic fields of a static particle to all orders in 1/N
hep-th
We determine the expectation value of the gauge invariant operator Tr
[F^2+... ] for N=4 SU(N) SYM, in the presence of an infinitely heavy static
particle in the symmetric representation of SU(N). We carry out the computation
in the context of the AdS/CFT correspondence, by considering the perturbation
of the dilaton field caused by the presence of a D3 brane dual to such an
external probe. We find that the effective chromo-electric charge of the probe
has exactly the same expression as the one recently found in the computation of
energy loss by radiation.
| arxiv topic:hep-th |
arxiv_dataset-30801112.2445 | QCD saturation at the LHC: comparisons of models to p+p and A+A data and
predictions for p+Pb collisions
hep-ph nucl-ex nucl-th
In a previous paper (arXiv:1011.1895), we showed that saturation models,
constrained by e+p HERA data on inclusive and diffractive cross-sections, are
in good agreement with p+p data at LHC in the soft sector. Particularly
impressive was the agreement of saturation models with the multiplicity
distribution as a function of $n_{\rm ch.}$. In this paper, we extend these
studies further and consider the agreement of these models with data on bulk
distributions in A+A collisions. We compare our results to data on central and
forward particle production in d+Au collisions at RHIC and make predictions for
inclusive distributions in p+Pb collisions at the LHC.
| arxiv topic:hep-ph nucl-ex nucl-th |
arxiv_dataset-30811112.2545 | One-dimensional Schr\"odinger operators with $\delta'$-interactions on a
set of Lebesgue measure zero
math.FA math.SP
We give an abstract definition of a one-dimensional Schr\"odinger
operator with $\delta'$-interaction on an arbitrary set~$\Gamma$ of
Lebesgue measure zero. The number of negative eigenvalues of such an
operator is at least as large as the number of those isolated points
of the set~$\Gamma$ that have negative values of the intensity
constants of the $\delta'$-interaction. In the case where the
set~$\Gamma$ is endowed with a Radon measure, we give constructive
examples of such operators having an infinite number of negative eigenvalues.
| arxiv topic:math.FA math.SP |
arxiv_dataset-30821112.2645 | Robust multipartite quantum correlations without complex encodings
quant-ph
One of the main challenges for the manipulation and storage of multipartite
entanglement is its fragility under noise. We present a simple recipe for the
systematic enhancement of the resistance of multipartite entanglement against
any local noise with a privileged direction in the Bloch sphere. For the case
of exact local dephasing along any given basis, and for all noise strengths,
our prescription grants full robustness: Even states with exponentially
decaying entanglement are mapped to states whose entanglement is constant. In
contrast to previous techniques resorting to complex logical-qubit encodings,
such enhancement is attained simply by performing local-unitary rotations
before the noise acts. The scheme is therefore highly experimentally friendly,
as it brings no overhead of extra physical qubits to encode logical ones. In
addition, we show that, apart from entanglement, the resiliences of the
relative entropy of quantumness and the usefulness as resources for practical
tasks such as metrology and nonlocality-based protocols are equivalently
enhanced.
| arxiv topic:quant-ph |
arxiv_dataset-30831112.2745 | Hausdorff dimension of three-period orbits in Birkhoff billiards
math.DS nlin.CD
We prove that the Hausdorff dimension of the set of three-period orbits in
classical billiards is at most one. Moreover, if the set of three-period orbits
has Hausdorff dimension one, then it has a tangent line at almost every point.
| arxiv topic:math.DS nlin.CD |
arxiv_dataset-30841112.2845 | Maximally localized Wannier functions for ultracold atoms in
one-dimensional double-well periodic potentials
cond-mat.quant-gas hep-ph
We discuss a method for constructing generalized Wannier functions that are
maximally localized at the minima of a one-dimensional periodic potential with
a double-well per unit cell. By following the approach of (Marzari M and
Vanderbilt D 1997 Phys. Rev. B 56, 12847), we consider a set of band-mixing
Wannier functions with minimal spread, and design a specific two-step gauge
transformation of the Bloch functions for a composite two band system. This
method is suited to efficiently compute the tight-binding coefficients needed
for mapping the continuous system to a discrete lattice model. Their behaviour
is analyzed here as a function of the symmetry properties of the double-well
(including the possibility of parity-breaking), in a range of feasible
experimental parameters.
| arxiv topic:cond-mat.quant-gas hep-ph |
arxiv_dataset-30851112.2945 | Symbolic approach and induction in the Heisenberg group
math.DS
We associate a homomorphism in the Heisenberg group to each hyperbolic
unimodular automorphism of the free group on two generators. We show that the
first return-time of some flows in "good" sections, are conjugate to
niltranslations, which have the property of being self-induced.
| arxiv topic:math.DS |
arxiv_dataset-30861112.3045 | Spectral properties of one-dimensional spiral spin density wave states
cond-mat.str-el cond-mat.mes-hall
We provide a full characterization of the spectral properties of spiral spin
density wave (SSDW) states which emerge in one-dimensional electron systems
coupled to localized magnetic moments or quantum wires with spin-orbit
interactions. We derive analytic results for the spectral function, local
density of states and optical conductivity in the low-energy limit by using
field theory techniques. We identify various collective modes and show that the
spectrum strongly depends on the interaction strength between the electrons.
The results provide characteristic signatures for an experimental detection of
SSDW states.
| arxiv topic:cond-mat.str-el cond-mat.mes-hall |
arxiv_dataset-30871112.3145 | Continuation and collapse of homoclinic tangles
math.DS math.NA
By a classical theorem transversal homoclinic points of maps lead to shift
dynamics on a maximal invariant set, also referred to as a homoclinic tangle.
In this paper we study the fate of homoclinic tangles in parameterized systems
from the viewpoint of numerical continuation and bifurcation theory. The
bifurcation result shows that the maximal invariant set near a homoclinic
tangency, where two homoclinic tangles collide, can be characterized by a
system of bifurcation equations that is indexed by a symbolic sequence. For the
H\'{e}non family we investigate in detail the bifurcation structure of
multi-humped orbits originating from several tangencies. The homoclinic network
found by numerical continuation is explained by combining our bifurcation
result with graph-theoretical arguments.
| arxiv topic:math.DS math.NA |
arxiv_dataset-30881112.3245 | Reconciling cyanobacterial fixed-nitrogen distributions and transport
experiments with quantitative modelling
physics.bio-ph q-bio.CB
Filamentous cyanobacteria growing in media with insufficient fixed nitrogen
differentiate some cells into heterocysts, which fix nitrogen for the remaining
vegetative cells. Transport studies have shown both periplasmic and cytoplasmic
connections between cells that could transport fixed-nitrogen along the
filament. Two experiments have imaged fixed-nitrogen distributions along
filaments. In 1974,Wolk et al found a peaked concentration of fixed-nitrogen at
heterocysts using autoradiographic techniques. In contrast, in 2007, Popa et al
used nanoSIMS to show large dips at the location of heterocysts, with a
variable but approximately level distribution between them. With an integrated
model of fixed-nitrogen transport and cell growth, we recover the results of
both Wolk et al and of Popa et al using the same model parameters. To do this,
we account for immobile incorporated fixed-nitrogen and for the differing
durations of labeled nitrogen fixation that occurred in the two experiments.
The variations seen by Popa et al are consistent with the effects of
cell-by-cell variations of growth rates, and mask diffusive gradients. We are
unable to rule out a significant amount of periplasmic fN transport.
| arxiv topic:physics.bio-ph q-bio.CB |
arxiv_dataset-30891112.3345 | On the vacua of N = 8 gauged supergravity in 4 dimensions
hep-th
We discuss a simple procedure for finding vacua of gauged supergravity
models, based on the variation of the embedding tensor rather than on a direct
minimization of the scalar potential. We apply this procedure to N=8 gauged
supergravity in 4 dimensions. We easily recover many of the previously known
vacua, also completing their scalar mass spectrum, and we apply our procedure
to find a dozen of new analytical vacuum solutions. The analysis shows an
interesting structure on the moduli spaces of these vacua and provides new
criteria to determine the expected value of the cosmological constant by a
simple inspection of the group properties of the embedding tensor.
| arxiv topic:hep-th |
arxiv_dataset-30901112.3445 | Jahn-Teller mechanism of stripe formation in doped layered
La$_{2-x}$Sr$_x$NiO$_4$ nickelates
cond-mat.str-el cond-mat.mtrl-sci
We introduce an effective model for $e_g$ electrons to describe
quasi-two-dimensional layered La$_{2-x}$Sr$_{x}$NiO$_4$ nickelates and study it
using correlated wave functions on $8 \times 8 $ and $6 \times 6 $ clusters.
The effective Hamiltonian includes the kinetic energy, on-site Coulomb
interactions for $e_g$ electrons (intraorbital $U$ and Hund's exchange $J_H$)
and the coupling between $e_g$ electrons and Jahn-Teller distortions (static
modes). The experimental ground state phases with inhomogeneous charge, spin
and orbital order at the dopings $x=1/3$ and $x=1/2$ are reproduced very well
by the model. Although the Jahn-Teller distortions are weak, we show that they
play a crucial role and stabilize the observed cooperative charge, magnetic and
orbital order in form of a diagonal stripe phase at $x=1/3$ doping and a
checkerboard phase at $x=1/2$ doping.
| arxiv topic:cond-mat.str-el cond-mat.mtrl-sci |
arxiv_dataset-30911112.3545 | \beta-deformed matrix model and Nekrasov partition function
hep-th
We study Penner type matrix models in relation with the Nekrasov partition
function of four dimensional \mathcal{N}=2, SU(2) supersymmetric gauge theories
with N_F=2,3 and 4. By evaluating the resolvent using the loop equation for
general \beta, we explicitly construct the first half-genus correction to the
free energy and demonstrate the result coincides with the corresponding
Nekrasov partition function with general \Omega-background, including higher
instanton contributions after modifying the relation of the Coulomb branch
parameter with the filling fraction. Our approach complements the proof using
the Selberg integrals directly which is useful to find the contribution in the
series of instanton numbers for a given deformation parameter.
| arxiv topic:hep-th |
arxiv_dataset-30921112.3645 | Higgs Boson Mass Predictions in SUGRA Unification, Recent LHC-7 Results,
and Dark Matter
hep-ph astro-ph.HE hep-ex
LHC-7 has narrowed down the mass range of the light Higgs boson. This result
is consistent with the supergravity unification framework, and the current
Higgs boson mass window implies a rather significant loop correction to the
tree value pointing to a relatively heavy scalar sparticle spectrum with
universal boundary conditions. It is shown that the largest value of the Higgs
boson mass is obtained on the Hyperbolic Branch of radiative breaking. The
implications of light Higgs boson in the broader mass range of 115 GeV to 131
GeV and a narrower range of 123 GeV to 127 GeV are explored in the context of
the discovery of supersymmetry at LHC-7 and for the observation of dark matter
in direct detection experiments.
| arxiv topic:hep-ph astro-ph.HE hep-ex |
arxiv_dataset-30931112.3745 | Asymmetry tests for Bifurcating Auto-Regressive Processes with missing
data
math.ST stat.TH
We present symmetry tests for bifurcating autoregressive processes (BAR) when
some data are missing. BAR processes typically model cell division data. Each
cell can be of one of two types \emph{odd} or \emph{even}. The goal of this
paper is to study the possible asymmetry between odd and even cells in a single
observed lineage. We first derive asymmetry tests for the lineage itself,
modeled by a two-type Galton-Watson process, and then derive tests for the
observed BAR process. We present applications on both simulated and real data.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-30941112.3845 | The Steiner rearrangement in any codimension
math.AP
We analyze the Steiner rearrangement in any codimension of Sobolev and $BV$
functions. In particular, we prove a P\'olya-Szeg\H{o} inequality for a large
class of convex integrals. Then, we give minimal assumptions under which
functions attaining equality are necessarily Steiner symmetric.
| arxiv topic:math.AP |
arxiv_dataset-30951112.3945 | Heat flow in chains driven by thermal noise
cond-mat.stat-mech
We consider the large deviation function for a classical harmonic chain
composed of N particles driven at the end points by heat reservoirs, first
derived in the quantum regime by Saito and Dhar and in the classical regime by
Saito and Dhar and Kundu et al. Within a Langevin description we perform this
calculation on the basis of a standard path integral calculation in Fourier
space. The cumulant generating function yielding the large deviation function
is given in terms of a transmission Green's function and is consistent with the
fluctuation theorem. We find a simple expression for the tails of the heat
distribution which turn out to decay exponentially. We, moreover, consider an
extension of a single particle model suggested by Derrida and Brunet and
discuss the two-particle case. We also discuss the limit for large N and
present a closed expression for the cumulant generating function. Finally, we
present a derivation of the fluctuation theorem on the basis of a Fokker-Planck
description. This result is not restricted to the harmonic case but is valid
for a general interaction potential between the particles.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-30961112.4045 | Using simple elastic bands to explain quantum mechanics: a conceptual
review of two of Aert's machine-models
quant-ph
From the beginning of his research, the Belgian physicist Diederik Aerts has
shown great creativity in inventing a number of concrete machine-models that
have played an important role in the development of general mathematical and
conceptual formalisms for the description of the physical reality. These models
can also be used to demystify much of the strangeness in the behavior of
quantum entities, by allowing to have a peek at what's going on - in structural
terms - behind the "quantum scenes," during a measurement. In this author's
view, the importance of these machine-models, and of the approaches they have
originated, have been so far seriously underappreciated by the physics
community, despite their success in clarifying many challenges of quantum
physics. To fill this gap, and encourage a greater number of researchers to
take cognizance of the important work of so-called Geneva-Brussels school, we
describe and analyze in this paper two of Aerts' historical machine-models,
whose operations are based on simple breakable elastic bands. The first one,
called the spin quantum-machine, is able to replicate the quantum probabilities
associated with the spin measurement of a spin-1/2 entity. The second one,
called the \emph{connected vessels of water model} (of which we shall present
here an alternative version based on elastics) is able to violate Bell's
inequality, as coincidence measurements on entangled states can do.
| arxiv topic:quant-ph |
arxiv_dataset-30971112.4145 | Convergence of energy scales on the approach to a local quantum critical
point
cond-mat.str-el
We find the emergence of strong correlations and universality on the approach
to the quantum critical points of a two impurity Anderson model. The two
impurities are coupled by an inter-impurity exchange interaction $J$ and direct
interaction $U_{12}$ and are hybridized with separate conduction channels.The
low energy behavior is described in terms of renormalized parameters, which can
be deduced from numerical renormalization group (NRG) calculations. We show
that on the approach to the transitions to a local singlet and a local charged
ordered state, the quasiparticle weight factor $z\to 0$, and the renormalized
parameters can be expressed in terms of a single energy scale $T^*$. The values
of the renormalized interaction parameters in terms of $T^*$ can be predicted
from the condition of continuity of the spin and charge susceptibilities, and
correspond to strong correlation as they are greater than or equal to the
effective band width. These predictions are confirmed by the NRG calculations,
including the case when the onsite interaction U=0.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-30981112.4245 | Ahlfors-Beurling conformal invariant and relative capacity of compact
sets
math.CV math.PR
For a given domain $D$ in the extended complex plane $\bar{\mathbb C}$ with
an accessible boundary point $z_0 \in \partial D$ and for a subset $E \subset
{D},$ relatively closed w.r.t. $D,$ we define the relative capacity $\rc E$ as
a coefficient in the asymptotic expansion of the Ahlfors-Beurling conformal
invariant $r(D\setminus E,z)/r(D, z)$ when $z$ approaches the point $z_0.$ Here
$r(G,z)$ denotes the inner radius at $z$ of the connected component of the set
$G$ containing the point $z.$ The asymptotic behavior of this quotient is
established. Further, it is shown that in the case when the domain $D$ is the
upper half plane and $z_0=\infty$ the capacity $\rc E$ coincides with the
well-known half-plane capacity ${\hc} E.$ Some properties of the relative
capacity are proven, including the behavior of this capacity under various
forms of symmetrization and under some other geometric transformations. Some
applications to bounded holomorphic functions of the unit disk are given.
| arxiv topic:math.CV math.PR |
arxiv_dataset-30991112.4345 | Quantum-Hall plateau-plateau transition in top-gated epitaxial graphene
grown on SiC (0001)
cond-mat.mes-hall
We investigate the low-temperature magneto-transport properties of monolayer
epitaxial graphene films formed on the Si-face of semi-insulating 4H-SiC
substrates by a high temperature sublimation process. A high-k top-gate on the
epitaxial graphene is realized by inserting a fully oxidized nanometer thin
aluminum film as a seeding layer, followed by an atomic layer deposition
process. At low temperatures, the devices demonstrate a strong field effect by
the top gate with an on/off ratio of ~7 and an electron mobility up to ~3250
cm^2/Vs. After the observation of the half-integer quantum Hall effect for
monolayer epitaxial graphene films, detailed magneto-transport measurements
have been carried out including varying densities, temperatures, magnetic
fields and currents. We study the width of the distinguishable quantum-Hall
plateau to plateau transition (Landau level index n=0 to n=1) as temperature
(T) and current are varied. For both gate voltage and magnetic field sweeps and
T>10 K the transition width goes as T^{-\kappa} with exponent \kappa ~0.42.
This universal scaling exponent agrees well with those found in III-V
heterojunctions with short range alloy disorders and in exfoliated graphene.
| arxiv topic:cond-mat.mes-hall |
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