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arxiv_dataset-53001406.1117 | The flux suppression at the highest energies
astro-ph.HE
Almost half a century ago, Greisen, Zatsepin and Kuz'min (GZK) predicted a
"cosmologically meaningful termination" of the spectrum of cosmic rays at
energies around $10^{20}$ eV due to their interaction with the cosmic microwave
background, as they propagate from distant extragalactic sources. A suppression
of the flux above $4\times 10^{19}$ eV is now confirmed. We argue that current
data are insufficient to conclude whether the observed feature is due to energy
loss during propagation, or else to the fact that the astrophysical
accelerators reach their limit, or indeed to a combination of both source
properties and propagation effects. We discuss the dependence of the spectral
steepening upon the cosmic-ray composition, source properties, and intervening
magnetic fields, and speculate on the additional information that may be
necessary to reach unambiguous conclusions about the origin of the flux
suppression and of the mechanisms behind the acceleration of cosmic rays up to
the highest observed energies.
| arxiv topic:astro-ph.HE |
arxiv_dataset-53011406.1217 | Free Form Lensing Implications for the Collision of Dark Matter and Gas
in the Frontier Fields Cluster MACSJ0416.1-2403
astro-ph.CO astro-ph.GA
We present a free form mass reconstruction of the massive lensing cluster
MACSJ0416.1-2403 using the latest Hubble Frontier Fields data. Our model
independent method finds that the extended lensing pattern is generated by two
elongated, closely projected clusters of similar mass. Our lens model
identifies new lensed images with which we improve the accuracy of the dark
matter distribution. We find that the bimodal mass distribution is nearly
coincident with the bimodal X-ray emission, but with the two dark matter peaks
lying closer together than the centroids of the X-ray emisison. We show this
can be achieved if the collision has occurred close to the plane and such that
the cores are deflected around each other. The projected mass profiles of both
clusters are well constrained because of the many interior lensed images,
leading to surprisingly flat mass profiles of both components in the region
15-100 kpc. We discuss the extent to which this may be generated by tidal
forces in our dynamical model which are large during an encounter of this type
as the cores "graze" each other. The relative velocity between the two cores is
estimated to be about 1200 km/s and mostly along the line of sight so that our
model is consistent with the relative redshift difference between the two cD
galaxies (dz = 0.04).
| arxiv topic:astro-ph.CO astro-ph.GA |
arxiv_dataset-53021406.1317 | Tumbling of a rigid rod in a shear flow
cond-mat.stat-mech
The tumbling of a rigid rod in a shear flow is analyzed in the high viscosity
limit. Following Burgers, the Master Equation is derived for the probability
distribution of the orientation of the rod. The equation contains one
dimensionless number, the Weissenberg number, which is the ratio of the shear
rate and the orientational diffusion constant. The equation is solved for the
stationary state distribution for arbitrary Weissenberg numbers, in particular
for the limit of high Weissenberg numbers. The stationary state gives an
interesting flow pattern for the orientation of the rod, showing the interplay
between flow due to the driving shear force and diffusion due to the random
thermal forces of the fluid. The average tumbling time and tumbling frequency
are calculated as a function of the Weissenberg number. A simple cross-over
function is proposed which covers the whole regime from small to large
Weissenberg numbers.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-53031406.1417 | Threshold Resummation for WZ and ZZ Pair Production at the LHC
hep-ph
We perform the threshold resummation for WZ and ZZ pair production at the
next-to-next-to-leading logarithmic accuracy in Soft-Collinear Effective Theory
at the LHC. Our results show that the resummation effects increase the total
cross sections by about 7% for ZZ production and 12% for WZ production
with$\sqrt{S}= 7,~8,~13 and 14 TeV, respectively, and the scale uncertainties
are significantly reduced. Besides, our numerical results are well consistent
with experimental data reported by the ATLAS and CMS collaborations.
| arxiv topic:hep-ph |
arxiv_dataset-53041406.1517 | Yet another criterion for global existence in the 3D relativistic
Vlasov-Maxwell system
math.AP math-ph math.MP
We prove that solutions of the 3D relativistic Vlasov-Maxwell system can be
extended, as long as the quantity $\sigma_{-1}(t, x) = \max_{|\omega|=1}
\,\int_{R^3} \frac{dp}{\sqrt{1+p^2}}\, \frac{1}{(1+v\cdot\omega)}\, f(t, x, p)$
is bounded in $L^2_x$.
| arxiv topic:math.AP math-ph math.MP |
arxiv_dataset-53051406.1617 | High speed photospheric material flow observed at the polarity inversion
line of a delta-type sunspot producing an X5.4 flare on 7 March 2012
astro-ph.SR
Solar flares abruptly release the free energy stored as a non-potential
magnetic field in the corona and may be accompanied by eruptions of the coronal
plasma. Formation of a non-potential magnetic field and the mechanisms for
triggering the onset of flares are still poorly understood. In particular,
photospheric dynamics observed near those polarity inversion lines that are
sites of major flare production have not been well observed with high spatial
resolution spectro-polarimetry. This paper reports on a remarkable high-speed
material flow observed along the polarity inversion line located between flare
ribbons at the main energy release side of an X5.4 flare on 7 March 2012.
Observations were carried out by the spectro-polarimeter of the Solar Optical
Telescope onboard Hinode. The high-speed material flow was observed in the
horizontally-oriented magnetic field formed nearly parallel to the polarity
inversion line. This flow persisted from at least 6 hours before the onset of
the flare, and continued for at least several hours after the onset of the
flare. Observations suggest that the observed material flow represents neither
the emergence nor convergence of the magnetic flux. Rather, it may be
considered to be material flow working both to increase the magnetic shear
along the polarity inversion line and to develop magnetic structures favorable
for the onset of the eruptive flare.
| arxiv topic:astro-ph.SR |
arxiv_dataset-53061406.1717 | Median Filtering is Equivalent to Sorting
cs.DS
This work shows that the following problems are equivalent, both in theory
and in practice:
- median filtering: given an $n$-element vector, compute the sliding window
median with window size $k$,
- piecewise sorting: given an $n$-element vector, divide it in $n/k$ blocks
of length $k$ and sort each block.
By prior work, median filtering is known to be at least as hard as piecewise
sorting: with a single median filter operation we can sort $\Theta(n/k)$ blocks
of length $\Theta(k)$. The present work shows that median filtering is also as
easy as piecewise sorting: we can do median filtering with one piecewise
sorting operation and linear-time postprocessing. In particular, median
filtering can directly benefit from the vast literature on sorting
algorithms---for example, adaptive sorting algorithms imply adaptive median
filtering algorithms.
The reduction is very efficient in practice---for random inputs the
performance of the new sorting-based algorithm is on a par with the fastest
heap-based algorithms, and for benign data distributions it typically
outperforms prior algorithms.
The key technical idea is that we can represent the sliding window with a
pair of sorted doubly-linked lists: we delete items from one list and add items
to the other list. Deletions are easy; additions can be done efficiently if we
reverse the time twice: First we construct the full list and delete the items
in the reverse order. Then we undo each deletion with Knuth's dancing links
technique.
| arxiv topic:cs.DS |
arxiv_dataset-53071406.1817 | Measuring a topological transition in an artificial spin 1/2 system
quant-ph cond-mat.mes-hall
We present measurements of a topological property, the Chern number
($C_\mathrm{1}$), of a closed manifold in the space of two-level system
Hamiltonians, where the two-level system is formed from a superconducting
qubit. We manipulate the parameters of the Hamiltonian of the superconducting
qubit along paths in the manifold and extract $C_\mathrm{1}$ from the
nonadiabitic response of the qubit. By adjusting the manifold such that a
degeneracy in the Hamiltonian passes from inside to outside the manifold, we
observe a topological transition $C_\mathrm{1} = 1 \rightarrow 0$. Our
measurement of $C_\mathrm{1}$ is quantized to within 2 percent on either side
of the transition.
| arxiv topic:quant-ph cond-mat.mes-hall |
arxiv_dataset-53081406.1917 | Generalized Tchebyshev triangulations
math.CO math.AT
After fixing a triangulation $L$ of a $k$-dimensional simplex that has no new
vertices on the boundary, we introduce a triangulation operation on all
simplicial complexes that replaces every $k$-face with a copy of $L$, via a
sequence of induced subdivisions. The operation may be performed in many ways,
but we show that the face numbers of the subdivided complex depend only on the
face numbers of the original complex, in a linear fashion. We use this linear
map to define a sequence of polynomials generalizing the Tchebyshev polynomials
of the first kind and show, that in many cases, but not all, the resulting
polynomials have only real roots, located in the interval $(-1,1)$. Some
analogous results are shown also for generalized Tchebyshev polynomials of the
higher kind, defined using summing over links of all original faces of a given
dimension in our generalized Tchebyshev triangulations. Generalized Tchebyshev
triangulations of the boundary complex of a cross-polytope play a central role
in our calculations, and for some of these we verify the validity of a
generalized lower bound conjecture by the second author.
| arxiv topic:math.CO math.AT |
arxiv_dataset-53091406.2017 | Anticipating Activity in Social Media Spikes
cs.SI physics.soc-ph
We propose a novel mathematical model for the activity of microbloggers
during an external, event-driven spike. The model leads to a testable
prediction of who would become most active if a spike were to take place. This
type of information is of great interest to commercial organisations,
governments and charities, as it identifies key players who can be targeted
with information in real time when the network is most receptive. The model
takes account of the fact that dynamic interactions evolve over an underlying,
static network that records who listens to whom. The model is based on the
assumption that, in the case where the entire community has become aware of an
external news event, a key driver of activity is the motivation to participate
by responding to incoming messages. We test the model on a large scale Twitter
conversation concerning the appointment of a UK Premier League football club
manager. We also present further results for a Bundesliga football match, a
marketing event and a television programme. In each case we find that
exploiting the underlying connectivity structure improves the prediction of who
will be active during a spike. We also show how the half-life of a spike in
activity can be quantified in terms of the network size and the typical
response rate.
| arxiv topic:cs.SI physics.soc-ph |
arxiv_dataset-53101406.2117 | Flat coordinates for flat St\"ackel systems
nlin.SI
In this article we explicitely construct transformation bewteen separable and
flat coordinates for flat St\"ackel systems and exploit the structre of these
systems in flat coordinates. In the elliptic case these coordinates become well
known generalized elliptical coordinates of Jacobi.
| arxiv topic:nlin.SI |
arxiv_dataset-53111406.2217 | Measurements of Observables Replaced by "Detections" in Quantum Theory
quant-ph
In Quantum Physics it is not always possible to directly perform the
measurement of an obsevable; in some of these cases, however, its value can be
{\sl detected}, i.e. it can be inferred by measuring {\sl another} observable
characterized by perfect correlation with the observable of interest. Though a
{\sl detection} is often interpreted as a {\sl measurement} of the detected
observable, we prove that the two concepts cannot be identified in Quantum
Physics. Furthermore, we establish what meaning and role can be ascribed to
detections coherently with Quantum Theory.
| arxiv topic:quant-ph |
arxiv_dataset-53121406.2317 | Warped Circumbinary Disks in Active Galactic Nuclei
astro-ph.GA gr-qc
We study a warping instability of a geometrically thin, non-self-gravitating
disk surrounding binary supermassive black holes on a circular orbit. Such a
circumbinary disk is subject to not only tidal torques due to the binary
gravitational potential but also radiative torques due to radiation emitted
from an accretion disk around each black hole. We find that a circumbinary disk
initially aligned with the binary orbital plane is unstable to radiation-driven
warping beyond the marginally stable warping radius, which is sensitive to both
the ratio of vertical to horizontal shear viscosities and the mass-to-energy
conversion efficiency. As expected, the tidal torques give no contribution to
the growth of warping modes but tend to align the circumbinary disk with the
orbital plane. Since the tidal torques can suppress the warping modes in the
inner part of circumbinary disk, the circumbinary disk starts to be warped at
radii larger than the marginally stable warping radius. If the warping radius
is of the order of 0.1 pc, a resultant semi-major axis is estimated to be of
the order of 10^-2 pc to 10^-4 pc for 10^7 Msun black hole. We also discuss the
possibility that the central objects of observed warped maser disks in active
galactic nuclei are binary supermassive black holes with a triple disk: two
accretion disks around the individual black holes and one circumbinary disk
surrounding them.
| arxiv topic:astro-ph.GA gr-qc |
arxiv_dataset-53131406.2417 | Reconstruction of scalar field theories realizing inflation consistent
with the Planck and BICEP2 results
hep-th astro-ph.CO gr-qc hep-ph
We reconstruct scalar field theories to realize inflation compatible with the
BICEP2 result as well as the Planck. In particular, we examine the chaotic
inflation model, natural (or axion) inflation model, and an inflationary model
with a hyperbolic inflaton potential. We perform an explicit approach to find
out a scalar field model of inflation in which any observations can be
explained in principle.
| arxiv topic:hep-th astro-ph.CO gr-qc hep-ph |
arxiv_dataset-53141406.2517 | Complex geometry of quantum cones
math.QA
The algebras obtained as fixed points of the action of the cyclic group $Z_N$
on the coordinate algebra of the quantum disc are studied. These can be
understood as coordinate algebras of quantum or non-commutative cones. The
following observations are made. First, contrary to the classical situation,
the actions of $Z_N$ are free and the resulting algebras are homologically
smooth. Second, the quantum cone algebras admit differential calculi that have
all the characteristics of calculi on smooth complex curves. Third, the
corresponding volume forms are exact, indicating that the constructed algebras
describe manifolds with boundaries.
| arxiv topic:math.QA |
arxiv_dataset-53151406.2617 | Spontaneous chiral symmetry breaking on a fully polarized frustrated
magnet at finite temperature
cond-mat.str-el
Frustration can introduce more-than-two minima in a spin dispersion relation
even in a fully polarized magnet under high magnetic field. We generally
discuss, on the fully polarized phase, the possibility of the chiral symmetry
breaking where the number of magnons pumped by finite temperature deviates to
one side of minima. We study this phase by constructing the Ginzburg-Landau
energy which is controlled by the external magnetic field and interactions
between magnons near the dispersion minima. This chirality breaking phase
accompanies, not a magnetization perpendicular to the external field, but the
vector chirality $S_m \times S_n$. We also discuss the possibility of the
chirality breaking phase on LiCuVO4 slightly above the saturation field.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-53161406.2717 | Dynamical Tides in Compact White Dwarf Binaries: Influence of Rotation
astro-ph.SR
Tidal interactions play an important role in the evolution and ultimate fate
of compact white dwarf (WD) binaries. Not only do tides affect the pre-merger
state (such as temperature and rotation rate) of the WDs, but they may also
determine which systems merge and which undergo stable mass transfer. In this
paper, we attempt to quantify the effects of rotation on tidal angular momentum
transport in binary stars, with specific calculations applied to WD stellar
models. We incorporate the effect of rotation using the traditional
approximation, in which the dynamically excited gravity waves within the WDs
are transformed into gravito-inertial Hough waves. The Coriolis force has only
a minor effect on prograde gravity waves, and previous results predicting the
tidal spin-up and heating of inspiraling WDs are not significantly modified.
However, rotation strongly alters retrograde gravity waves and inertial waves,
with important consequences for the tidal spin-down of accreting WDs. We
identify new dynamical tidal forcing terms that arise from a proper separation
of the equilibrium and dynamical tide components; these new forcing terms are
very important for systems near synchronous rotation. Additionally, we discuss
the impact of Stokes drift currents on the wave angular momentum flux. Finally,
we speculate on how tidal interactions will affect super-synchronously rotating
WDs in accreting systems.
| arxiv topic:astro-ph.SR |
arxiv_dataset-53171406.2817 | Isogeometric Boundary Element Method with Hierarchical Matrices
cs.NA math.NA
In this work we address the complexity problem of the isogeometric Boundary
Element Method by proposing a collocation scheme for practical problems in
linear elasticity and the application of hierarchical matrices. For mixed
boundary value problems, a block system of matrices similar to Galerkin
formulations is constructed allowing an effective application of that matrix
format. We introduce a strategy for the geometric bisection of surfaces based
on NURBS patches. The approximation of system matrices is carried out by means
of kernel interpolation. Numerical results are shown that prove the success of
the formulation.
| arxiv topic:cs.NA math.NA |
arxiv_dataset-53181406.2917 | New formulation of the Kubo Optical Conductivity: a Shortcut to
Transport Properties
cond-mat.other
The Kubo formula for the electrical conductivity is rewritten in terms of a
sum of Drude-like contributions associated to the exact eigenstates of the
interacting system, each characterized by its own frequency-dependent
relaxation time. The structure of the novel and equivalent formulation,
weighting the contribution from each eigenstate by its Boltzmann occupation
factor, simplifies considerably the access to the static properties (dc
conductivity) and resolves the long standing difficulties to recover the
Boltzmann result for dc conductivity from the Kubo formula. It is shown that
the Boltzmann result, containing the correct transport scattering time instead
of the electron lifetime determined by the Green function, can be recovered in
problems with elastic and inelastic scattering at the lowest order of
interaction.
| arxiv topic:cond-mat.other |
arxiv_dataset-53191406.3017 | Simultaneous emergence of curved spacetime and quantum mechanics
physics.gen-ph
It is shown in this paper that the geometrically structureless spacetime
manifold is converted instantaneously to a curved one, the Riemannian or may be
a Finslerian spacetime with an associated Riemannian spacetime, on the
appearance of quantum Weyl spinors dependent only on time in that background
flat manifold and having the sympleic property in the abstract space of
spinors. The scenario depicts simultaneous emergence of the gravity in accord
with general relativity and quantum mechanics.The emergent gravity leads to the
generalized uncertainty principle, which in turn, ushers in discrete space
time. The emerged space time is specified here as to be Finslerian and the
field equation in that space time has been obtained from the classical one due
to the arising quantized space and time. From this field equation we find the
quantum field equation for highly massive (of the Planck order) spinors in the
associated Riemannian space of the Finsler space, which is in fact, the
background FRW space time of the universe.These highly massive spinors provide
the mass distribution complying Einstein equivalence principle. All these
occurred in the indivisible minimum time considered as zero time or
spontaneity.
| arxiv topic:physics.gen-ph |
arxiv_dataset-53201406.3117 | Low-cost Augmented Reality prototype for controlling network devices
cs.HC cs.MM
With the evolution of mobile devices, and smart-phones in particular, comes
the ability to create new experiences that enhance the way we see, interact,
and manipulate objects, within the world that surrounds us. It is now possible
to blend data from our senses and our devices in numerous ways that simply were
not possible before using Augmented Reality technology. In a near future, when
all of the office devices as well as your personal electronic gadgets are on a
common wireless network, operating them using a universal remote controller
would be possible. This paper presents an off-the-shelf, low-cost prototype
that leverages the Augmented Reality technology to deliver a novel and
interactive way of operating office network devices around using a mobile
device. We believe this type of system may provide benefits to controlling
multiple integrated devices and visualizing interconnectivity or utilizing
visual elements to pass information from one device to another, or may be
especially beneficial to control devices when interacting with them physically
may be difficult or pose danger or harm.
| arxiv topic:cs.HC cs.MM |
arxiv_dataset-53211406.3217 | Signal Formation in Various Detectors
hep-ex physics.ins-det
In this write-up we present the general theory of the signal formation in
various detectors. We follow a pedagogical analysis and presentation such that
the results could be easily understood and applied by the interested reader to
the different detector configurations. We include few applications to gaseous
detectors, namely, Monitored Drift Tubes (MDT) and micro-pattern gaseous
detectors of the Micromegas type.
| arxiv topic:hep-ex physics.ins-det |
arxiv_dataset-53221406.3317 | Types of perfect matchings in toroidal square grids
math-ph math.CO math.MP
Let $T_{m,n}$ be toroidal square grid of size $m\times n$ and let both $m$
and $n$ be even. Let $P$ be a perfect matching of $T_{m,n}$ and let $D(P)$ be
the cycle-rooted spanning forest of $P$ obtained by the generalized Temperley's
construction. The types of $P$ and $D(P)$ in the first homology group
$H_1(\mathbb{T},\mathbb{Z})$ of torus $\mathbb{T}$ with coefficients in
$\mathbb{Z}$ has been extensively studied. In this paper we study the types of
$P$ and $D(P)$ in the first homology group $H_1(\mathbb{T},\mathbb{F}_2)$ with
the coefficients in $\mathbb{F}_2$. Our considerations connect two remarkable
results concerning perfect matchings of toroidal square grids, namely
Temperley's bijection and the Arf-invariant formula.
| arxiv topic:math-ph math.CO math.MP |
arxiv_dataset-53231406.3417 | Generators of Quantum Markov Semigroups
math-ph math.MP math.OA
Quantum Markov Semigroups (QMSs) originally arose in the study of the
evolutions of irreversible open quantum systems. Mathematically, they are a
generalization of classical Markov semigroups where the underlying function
space is replaced by a non-commutative operator algebra. In the case when the
QMS is uniformly continuous, theorems due to Lindblad \cite{lindblad},
Stinespring \cite{stinespring}, and Kraus \cite{kraus} imply that the generator
of the semigroup has the form $$L(A)=\sum_{n=1}^{\infty}V_n^*AV_n +GA+AG^*$$
where $V_n$ and G are elements of the underlying operator algebra. In the
present paper we investigate the form of the generators of QMSs which are not
necessarily uniformly continuous and act on the bounded operators of a Hilbert
space. We prove that the generators of such semigroups have forms that reflect
the results of Lindblad and Stinespring. We also make some progress towards
forms reflecting Kraus' result. Lastly we look at several examples to clarify
our findings and verify that some of the unbounded operators we are using have
dense domains.
| arxiv topic:math-ph math.MP math.OA |
arxiv_dataset-53241406.3517 | Affine cellularity of affine Brauer algebras
math.QA
We show that the affine Brauer algebras are affine cellular algebras in the
sense of Koenig and Xi.
| arxiv topic:math.QA |
arxiv_dataset-53251406.3617 | Reconstruction/Non-reconstruction Thresholds for Colourings of General
Galton-Watson Trees
cs.DM
The broadcasting models on trees arise in many contexts such as discrete
mathematics, biology statistical physics and cs. In this work, we consider the
colouring model. A basic question here is whether the root's assignment affects
the distribution of the colourings at the vertices at distance h from the root.
This is the so-called "reconstruction problem". For a d-ary tree it is well
known that d/ln (d) is the reconstruction threshold. That is, for
k=(1+eps)d/ln(d) we have non-reconstruction while for k=(1-eps)d/ln(d) we have.
Here, we consider the largely unstudied case where the underlying tree is
chosen according to a predefined distribution. In particular, our focus is on
the well-known Galton-Watson trees. This model arises naturally in many
contexts, e.g. the theory of spin-glasses and its applications on random
Constraint Satisfaction Problems (rCSP). The aforementioned study focuses on
Galton-Watson trees with offspring distribution B(n,d/n), i.e. the binomial
with parameters n and d/n, where d is fixed. Here we consider a broader version
of the problem, as we assume general offspring distribution, which includes
B(n,d/n) as a special case.
Our approach relates the corresponding bounds for (non)reconstruction to
certain concentration properties of the offspring distribution. This allows to
derive reconstruction thresholds for a very wide family of offspring
distributions, which includes B(n,d/n). A very interesting corollary is that
for distributions with expected offspring d, we get reconstruction threshold
d/ln(d) under weaker concentration conditions than what we have in B(n,d/n).
Furthermore, our reconstruction threshold for the random colorings of
Galton-Watson with offspring B(n,d/n), implies the reconstruction threshold for
the random colourings of G(n,d/n).
| arxiv topic:cs.DM |
arxiv_dataset-53261406.3717 | New statistical results on the optical IDV data of BL Lac S5 0716+714
astro-ph.HE
This paper reports on the statistical behaviour of the optical IntraDay
Variability of BL Lac S5 0716+714. Available IntraDay Variability data in the
optical is tested to see whether or not the magnitude is log-normally
distributed. It was consistently found that this is not the case. This is in
agreement with a previous discussion for data for the same object but in a
different observational period. Simultaneously, the spectral slope of the light
curves is calculated. The implications of these findings for models which
discuss both the location and the source of IntraDay Variability are presented.
| arxiv topic:astro-ph.HE |
arxiv_dataset-53271406.3817 | Fermi-edge transmission resonance in graphene driven by a single Coulomb
impurity
cond-mat.mes-hall
The interaction between the Fermi sea of conduction electrons and a
non-adiabatic attractive impurity potential can lead to a power-law divergence
in the tunneling probability of charge through the impurity. The resulting
effect, known as the Fermi edge singularity (FES), constitutes one of the most
fundamental many-body phenomena in quantum solid state physics. Here we report
the first observation of FES for Dirac Fermions in graphene driven by isolated
Coulomb impurities in the conduction channel. In high-mobility graphene devices
on hexagonal boron nitride substrates, the FES manifests in abrupt changes in
conductance with a large magnitude $\approx e^{2}/h$ at resonance, indicating
total many-body screening of a local Coulomb impurity with fluctuating charge
occupancy. Furthermore, we exploit the extreme sensitivity of graphene to
individual Coulomb impurities, and demonstrate a new defect-spectroscopy tool
to investigate strongly correlated phases in graphene in the quantum Hall
regime.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-53281406.3917 | Polymorphism and thermodynamic ground state of Silver fulminate studied
from van der Waals density functional calculations
cond-mat.mtrl-sci
Silver fulminate (AgCNO) is a primary explosive, which exists in two
polymorphic phases namely orthorhombic (\emph{Cmcm}) and trigonal
(\emph{R$\bar{3}$}) forms at ambient conditions. In the present study, we have
investigated the effect of pressure and temperature on relative phase stability
of the polymorphs using planewave pseudopotential approaches based on Density
Functional Theory (DFT). van der Waals interactions play a significant role in
predicting the phase stability and they can be effectively captured by
semiempirical dispersion correction methods incontrast to standard DFT
functionals. Based on our total energy calculations using DFT-D2 method, the
\emph{Cmcm} structure is found to be the preferred thermodynamic equilibrium
phase under studied pressure and temperature range. Hitherto \emph{Cmcm} and
\emph{R$\bar{3}$} phases denoted as $\alpha$ and $\beta$-forms of AgCNO,
respectively. Also a pressure induced polymorphic phase transition is seen
using DFT functionals and the same was not observed with DFT-D2 method. The
equation of state and compressibility of both polymorphic phases were
investigated. Electronic structure and optical properties were calculated using
full potential linearized augmented plane wave method within the Tran-Blaha
modified Becke-Johnson potential. The calculated electronic structure shows
that $\alpha$, $\beta$ phases are indirect band gap insulators with a band gap
values of 3.51 and 4.43 eV, respectively. The nature of chemical bonding is
analyzed through the charge density plots and partial density of states.
Optical anisotropy, electric-dipole transitions and photo sensitivity to light
of the polymorphs are analyzed from the calculated optical spectra. Overall,
the present study provides an early indication to experimentalists to avoid the
formation of unstable $\beta$-form of AgCNO.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-53291406.4017 | The incompressible Navier-Stokes system with time-dependent Robin-type
boundary conditions
math.AP
We show that the incompressible 3D Navier-Stokes system in a C 1;1 bounded
domain or a bounded convex domain with a non penetration condition u = 0 at the
boundary @ together with a time-dependent Robin boundary condition of the type
curl u = (t)u on @ admits a solution with enough regularity provided the
initial condition is small enough in an appropriate functional space.
| arxiv topic:math.AP |
arxiv_dataset-53301406.4117 | On Parameter Space of Complex Polynomial Vector Fields in the Complex
Plane
math.DS
The space of degree d single-variable monic and centered complex polynomial
vector fields can be decomposed into loci in which the vector fields have the
same topological structure. We analyze the geometric structure of these loci
and describe some bifurcations, in particular, it is proved that new homoclinic
separatrices can form under small perturbation. By an example, we show that
this decomposition of parameter space by combinatorial data is not a cell
decomposition. The appendix to this article, joint work with Tan Lei, shows
that landing separatrices are stable under small perturbation of the vector
field if the multiplicities of the equilibrium points are preserved.
| arxiv topic:math.DS |
arxiv_dataset-53311406.4217 | The last forcing standing with diamonds
math.LO
This article continues Roslanowski and Shelah math.LO/9906024 and 1105.6049
We introduce here yet another property of (<lambda)-strategically complete
forcing notions which implies that their lambda-support iterations do not
collapse lambda^+.
| arxiv topic:math.LO |
arxiv_dataset-53321406.4317 | Frustration induced noncollinear magnetic order phase in one-dimensional
Heisenberg chain with alternating antiferromagnetic and ferromagnetic next
nearest neighbor interactions
cond-mat.str-el
By using the coupled cluster method, the numerical exact diagonalization
method, and the numerical density matrix renormalization group method, we
investigated the properties of the one-dimensional Heisenberg chain with
alternating antiferromagnetic and ferromagnetic next nearest neighbor
interactions. In the classical limit, the ground state is in the collinear Neel
state if a<1/2, while for a>1/2, there is an noncollinear canted state. For the
quantum case, we found that, although the classical Neel state is absent, the
canted state exists if the frustration parameter a exceeds a critical point
ac1. The precise critical point ac1 can be determined by using the coupled
cluster method and the numerical exact diagonalization method separately. The
results of the coupled cluster method and the exact diagonalization method both
disclose that the type of phase transition occurring at ac1 changes from a
classical second-order transition to a quantum first-order transition due to
quantum fluctuation. Although there is another critical point ac2 in a finite
system at which the ground state evolves from the canted state to the collinear
Neel plus ferromagnetic state, that state is absent because ac2 tends to
infinity in the thermodynamic limit.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-53331406.4417 | A Group Theoretical Approach to Graviton Two-Point Function
gr-qc
Respecting the group theoretical approach, it is debated that the theory of
linear conformal gravity should be formulated through a tensor field of rank-3
and mixed symmetry \cite{binegar}. Pursuing this path, such a field equation
was obtained in de Sitter space \cite{takook}. In present work, considering the
de Sitter ambient space notation, a proper solution to the physical part of
this field equation is obtained. We have also calculated the related two-point
function, which is interestingly de Sitter invariant and free of infrared
divergence.
| arxiv topic:gr-qc |
arxiv_dataset-53341406.4517 | Probing the $\nu=2/3$ fractional quantum Hall edge by momentum-resolved
tunneling
cond-mat.str-el cond-mat.mes-hall
The nature of the fractional quantum Hall state with filling factor $\nu=2/3$
and its edge modes continues to remain an open problem in low-dimensional
condensed matter physics. Here, we suggest an experimental setting to probe the
$\nu=2/3$ edge by tunnel-coupling it to a $\nu=1$ integer quantum Hall edge in
another layer of a two-dimensional electron gas (2DEG). In this double-layer
geometry, the momentum of tunneling electrons may be boosted by an auxiliary
magnetic field parallel to the two planes of 2DEGs. We evaluate the current as
a function of bias voltage and the boosting magnetic field. Its threshold
behavior yields information about the spectral function of the $\nu=2/3$ edge,
in particular about the nature of the chiral edge modes. Our theory accounts
also for the effects of Coulomb interaction and disorder.
| arxiv topic:cond-mat.str-el cond-mat.mes-hall |
arxiv_dataset-53351406.4617 | General triple charged black ring solution in supergravity
hep-th gr-qc
We present the general black ring solution in $U(1)^{3}$ supergravity in 5
dimensions with three independent dipole and electric charges. This immediately
gives the general black ring solution in the minimal 5D supergravity as well.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-53361406.4717 | Non-commutativity from exact renormalization group dualities
hep-th quant-ph
Here we demonstrate, firstly, the construction of dualities using the exact
renormalization group approach and, secondly, that spatial non-commutativity
can emerge as such a duality. This is done in a simple quantum mechanical
setting that establishes an exact duality between the commutative and
non-commutative quantum Hall systems with harmonic interactions. It is also
demonstrated that this link can be understood as a blocking (coarse graining)
transformation in time that relates commutative and non-commutative degrees of
freedom.
| arxiv topic:hep-th quant-ph |
arxiv_dataset-53371406.4817 | 3D Printing of Scintillating Materials
cond-mat.mtrl-sci nucl-ex physics.ins-det
We demonstrate, for the first time, the applicability of 3D printing
technique to the manufacture of scintillation detectors. We report of a
formulation, usable in stereolithographic printing, that exhibits scintillation
efficiency on the order of 30\% of that of commercial polystyrene based
scintillators. We discuss the applicability of these techniques and propose
future enhancements that will allow tailoring the printed scintillation
detectors to various application.
| arxiv topic:cond-mat.mtrl-sci nucl-ex physics.ins-det |
arxiv_dataset-53381406.4917 | Max-Weight Scheduling and Quality-Aware Streaming for Device-to-Device
Video Delivery
cs.NI
We propose and analyze centralized and distributed algorithms for
device-to-device video scheduling and streaming. The proposed algorithms
address jointly the problems of device-to-device link scheduling and video
quality adaptation in streaming. Our simulations show that the proposed
algorithms significantly outperform conventional separated approaches that
treat these two problems independently.
| arxiv topic:cs.NI |
arxiv_dataset-53391406.5017 | Lax operator algebras and gradings on semi-simple Lie algebras
math.RA math-ph math.MP math.RT
A Lax operator algebra is constructed for an arbitrary semi-simple Lie
algebra over $\mathbb C$ equipped with a $\mathbb Z$-grading, and arbitrary
compact Riemann surface with marked points. In this set-up, a treatment of
almost graded structures, and classification of the central extensions of Lax
operator algebras are given. A relation to the earlier approach based on the
Tyurin parameters is established.
| arxiv topic:math.RA math-ph math.MP math.RT |
arxiv_dataset-53401406.5117 | Simple and reliable method of conductive SPM probe fabrication using
carbon nanotubes
cond-mat.mes-hall cond-mat.mtrl-sci
We demonstrate the procedure of Scanning Probe Microscopy (SPM) conductive
probe fabrication with a single multi-walled carbon nanotube (MWNT) on a
silicon cantilever pyramid. The nanotube bundle reliably attached to the
metal-covered pyramid is formed using electrophoresis technique from the MWNT
suspension. It is shown that the dimpled aluminium sample can be used both for
shortening/modification of the nanotube bundle by applying pulse voltage
between the probe and the sample, and for controlling the probe shape via
Atomic Force Microscopy (AFM) imaging the sample. It allows to fabricate a
probe suitable for SPM imaging in the contact and modulation regimes. The
majority of such probes are conductive with conductivity not degrading within
hours of SPM imaging.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-53411406.5217 | Optomechanical conversion by mechanical turbines
cond-mat.soft
Liquid crystal elastomers are rubbers with liquid crystal order. They
contract along their nematic director when heated or illuminated. The shape
changes are large and occur in a relatively narrow temperature interval, or at
low illumination, around the nematic-isotropic transition. We present a
conceptual design of a mechanical, turbine-based engine using photo-active
liquid crystal elastomers to extract mechanical work from light. Its efficiency
is estimated to be 40%.
| arxiv topic:cond-mat.soft |
arxiv_dataset-53421406.5317 | Coexistence of superconductivity and charge-density-wave domain in
$1T$-Fe$_x$Ta$_{1-x}$SSe
cond-mat.supr-con
A series of $1T$-Fe$_x$Ta$_{1-x}$SSe (0 $\leq x \leq$ 0.1) single crystals
was fabricated via the chemical-vapor-transport (CVT) method and investigated
by structure, transport, and magnetic measurements along with the
density-functional-theory (DFT) calculations. The superconductivity (SC) in
parent $1T$-TaSSe can be gradually suppressed by Fe-substitution ($x\leq0.03$),
accompanied by the disappearance of charge-density-wave (CDW). DFT calculations
show that the Fe-substitution effectively inhibits the CDW superstructure and
thereby the CDW domains are destroyed. With further increasing $x$ ($x>0.03$),
the disorder-induced scattering increases, and the system enters into the
possible Anderson localization (AL) state. Our results prove the SC develops in
the CDW phase and coexists with the CDW domain in $1T$-TaSSe system.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-53431406.5417 | Existence of the solution to a nonlocal-in-time evolutional problem
math.DS math.AP math.FA
This work is devoted to the study of a nonlocal-in-time evolutional problem
for the first order differential equation in Banach space. Our primary
approach, although stems from the convenient technique based on the reduction
of a nonlocal problem to its classical initial value analogue, uses more
advanced analysis. That is a validation of the correctness in definition of the
general solution representation via the Dunford-Cauchy formula. Such approach
allows us to reduce the given existence problem to the problem of locating
zeros of a certain entire function. It results in the necessary and sufficient
conditions for the existence of a generalized (mild) solution to the given
nonlocal problem. Aside of that we also present new sufficient conditions which
in the majority of cases generalize existing results.
| arxiv topic:math.DS math.AP math.FA |
arxiv_dataset-53441406.5517 | Molecular hydrogen from z = 0.0963 DLA towards the QSO J1619+3342
astro-ph.GA
We report the detection of H2 in a zabs= 0.0963 Damped Lyman-{\alpha} (DLA)
system towards zem = 0.4716 QSO J1619+3342. This DLA has log N(H I) = 20.55
(0.10), 18.13 < log N(H2) < 18.40, [S/H] = -0.62 (0.13), [Fe/S] = -1.00 (0.17)
and the molecular fraction -2.11 < log f(H2) < -1.85. The inferred gas kinetic
temperature using the rotational level population is in the range 95 - 132 K.
We do not detect C I or C II* absorption from this system. Using R- and V-band
deep images we identify a sub-L* galaxy at an impact parameter of 14 kpc from
the line of sight, having consistent photometric redshift, as a possible host
for the absorber. We use the photoionization code CLOUDY to get the physical
conditions in the H2 component using the observational constrains from H2, C I,
C II* and Mg I. All the observations can be consistently explained if one or
more of the following is true: (i) Carbon is underabundant by more than 0.6 dex
as seen in halo stars with Z ~ 0.1 Z_sun, (ii) H I associated with H2 component
is less than 50% of the H I measured along the line of sight and (iii) the H2
formation rate on the dust grains is at least a factor two higher than what is
typically used in analytic calculations for Milky Way interstellar medium. Even
when these are satisfied, the gas kinetic temperature in the models are much
lower than what is inferred from the ortho-to-para ratio of the molecular
hydrogen. Alternatively the high kinetic temperature could be a consequence of
contribution to the gas heating from non-radiative heating processes seen in
hydrodynamical simulations.
| arxiv topic:astro-ph.GA |
arxiv_dataset-53451406.5617 | Web Document Clustering and Ranking using Tf-Idf based Apriori Approach
cs.IR
The dynamic web has increased exponentially over the past few years with more
than thousands of documents related to a subject available to the user now.
Most of the web documents are unstructured and not in an organized manner and
hence user facing more difficult to find relevant documents. A more useful and
efficient mechanism is combining clustering with ranking, where clustering can
group the similar documents in one place and ranking can be applied to each
cluster for viewing the top documents at the beginning.. Besides the particular
clustering algorithm, the different term weighting functions applied to the
selected features to represent web document is a main aspect in clustering
task. Keeping this approach in mind, here we proposed a new mechanism called
Tf-Idf based Apriori for clustering the web documents. We then rank the
documents in each cluster using Tf-Idf and similarity factor of documents based
on the user query. This approach will helps the user to get all his relevant
documents in one place and can restrict his search to some top documents of his
choice. For experimental purpose, we have taken the Classic3 and Classic4
datasets of Cornell University having more than 10,000 documents and use gensim
toolkit to carry out our work. We have compared our approach with traditional
apriori algorithm and found that our approach is giving better results for
higher minimum support. Our ranking mechanism is also giving a good F-measure
of 78%.
| arxiv topic:cs.IR |
arxiv_dataset-53461406.5717 | Constraining regular and turbulent magnetic field strengths in M51 via
Faraday depolarization
astro-ph.GA
We employ an analytical model that incorporates both wavelength-dependent and
wavelength-independent depolarization to describe radio polarimetric
observations of polarization at $\lambda \lambda \lambda \, 3.5, 6.2, 20.5$ cm
in M51 (NGC 5194). The aim is to constrain both the regular and turbulent
magnetic field strengths in the disk and halo, modeled as a two- or three-layer
magneto-ionic medium, via differential Faraday rotation and internal Faraday
dispersion, along with wavelength-independent depolarization arising from
turbulent magnetic fields. A reduced chi-squared analysis is used for the
statistical comparison of predicted to observed polarization maps to determine
the best-fit magnetic field configuration at each of four radial rings spanning
$2.4 - 7.2$ kpc in $1.2$ kpc increments. We find that a two-layer modeling
approach provides a better fit to the observations than a three-layer model,
where the near and far sides of the halo are taken to be identical, although
the resulting best-fit magnetic field strengths are comparable. This implies
that all of the signal from the far halo is depolarized at these wavelengths.
We find a total magnetic field in the disk of approximately $18~\mu$G and a
total magnetic field strength in the halo of $\sim 4-6~\mu$G. Both turbulent
and regular magnetic field strengths in the disk exceed those in the halo by a
factor of a few. About half of the turbulent magnetic field in the disk is
anisotropic, but in the halo all turbulence is only isotropic.
| arxiv topic:astro-ph.GA |
arxiv_dataset-53471406.5817 | Reduction of systemic risk by means of Pigouvian taxation
q-fin.RM physics.soc-ph q-fin.GN q-fin.TR
We analyze the possibility of reduction of systemic risk in financial markets
through Pigouvian taxation of financial institutions which is used to support
the rescue fund. We introduce the concept of the cascade risk with a clear
operational definition as a subclass and a network related measure of the
systemic risk. Using financial networks constructed from real Italian money
market data and using realistic parameters, we show that the cascade risk can
be substantially reduced by a small rate of taxation and by means of a simple
strategy of the money transfer from the rescue fund to interbanking market
subjects. Furthermore, we show that while negative effects on the return on
investment ($ROI$) are direct and certain, an overall positive effect on risk
adjusted return on investments ($ROI^{RA}$) is visible. Please note that
\emph{the taxation} is introduced as a monetary/regulatory, not as a fiscal
measure, as the term could suggest. \emph{The rescue fund} is implemented in a
form of a common reserve fund.
| arxiv topic:q-fin.RM physics.soc-ph q-fin.GN q-fin.TR |
arxiv_dataset-53481406.5917 | BSTree: an Incremental Indexing Structure for Similarity Search and Real
Time Monitoring of Data Streams
cs.DB
In this work, a new indexing technique of data streams called BSTree is
proposed. This technique uses the method of data discretization, SAX [4], to
reduce online the dimensionality of data streams. It draws on Btree to build
the index and finally uses an LRV (least Recently visited) pruning technique to
rid the index structure from data whose last visit time exceeds a threshold
value and thus minimizes response time for similarity search queries.
| arxiv topic:cs.DB |
arxiv_dataset-53491406.6017 | Uniform-in-bandwidth consistency for nonparametric estimation of
divergence measures
stat.ME
We propose nonparametric estimation of divergence measures between continuous
distributions. Our approach is based on a plug-in kernel- type estimators of
density functions. We give the uniform in bandwidth consistency for the
proposal estimators. As a consequence, their asymp- totic 100% confidence
intervals are also provided.
| arxiv topic:stat.ME |
arxiv_dataset-53501406.6117 | Consistency Relations for Large Field Inflation
astro-ph.CO gr-qc hep-th
Consistency relations for chaotic inflation with a monomial potential and
natural inflation and hilltop inflation are given which involve the scalar
spectral index $n_s$, the tensor-to-scalar ratio $r$ and the running of the
spectral index $\alpha$. The measurement of $\alpha$ with $O(10^{-3})$ and the
improvement in the measurement of $n_s$ could discriminate monomial model from
natural/hilltop inflation models. A consistency region for general large field
models is also presented.
| arxiv topic:astro-ph.CO gr-qc hep-th |
arxiv_dataset-53511406.6217 | Coherent control of light interaction with graphene
physics.optics
We report the experimental observation of all-optical modulation of light in
a graphene film. The graphene film is scanned across a standing wave formed by
two counter-propagating laser beams in a Sagnac interferometer. Through a
coherent absorption process the on-axis transmission is modulated with close to
80% efficiency. Furthermore we observe modulation of the scattered energy by
mapping the off-axis scattered optical signal: scattering is minimized at a
node of the standing wave pattern and maximized at an antinode. The results
highlight the possibility to switch and modulate any given optical interaction
with deeply sub-wavelength films.
| arxiv topic:physics.optics |
arxiv_dataset-53521406.6317 | Energy transfer and dissipation in forced isotropic turbulence
physics.flu-dyn
A model for the Reynolds number dependence of the dimensionless dissipation
rate $C_{\varepsilon}$ was derived from the dimensionless
K\'{a}rm\'{a}n-Howarth equation, resulting in $C_{\varepsilon}=C_{\varepsilon,
\infty} + C/R_L + O(1/R_L^2)$, where $R_L$ is the integral scale Reynolds
number. The coefficients $C$ and $C_{\varepsilon,\infty}$ arise from asymptotic
expansions of the dimensionless second- and third-order structure functions.
This theoretical work was supplemented by direct numerical simulations (DNSs)
of forced isotropic turbulence for integral scale Reynolds numbers up to
$R_L=5875$ ($R_\lambda=435$), which were used to establish that the decay of
dimensionless dissipation with increasing Reynolds number took the form of a
power law $R_L^n$ with exponent value $n = -1.000\pm 0.009$, and that this
decay of $C_{\varepsilon}$ was actually due to the increase in the Taylor
surrogate $U^3/L$. The model equation was fitted to data from the DNS which
resulted in the value $C=18.9\pm 1.3$ and in an asymptotic value for
$C_\varepsilon$ in the infinite Reynolds number limit of
$C_{\varepsilon,\infty} = 0.468 \pm 0.006$.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-53531406.6417 | Big Models: From Beijing to the whole China
cs.OH
This paper propose the concept of big model as a novel research paradigm for
regional and urban studies. Big models are fine-scale regional/urban simulation
models for a large geographical area, and they overcome the trade-off between
simulated scale and spatial unit by tackling both of them at the same time
enabled by emerging big/open data, increasing computation power and matured
regional/urban modeling methods. The concept, characteristics, and potential
applications of big models have been elaborated. We addresse several case
studies to illustrate the progress of research and utilization on big models,
including mapping urban areas for all Chinese cities, performing parcel-level
urban simulation, and several ongoing research projects. Most of these
applications can be adopted across the country, and all of them are focusing on
a fine-scale level, such as a parcel, a block, or a township (sub-district),
which is not the same with the existing studies using conventional models that
are only suitable for a certain single or two cities or regions, or for a
larger area but have to significantly sacrifice the data resolution. It is
expected that big models will mark a promising new era for the urban and
regional study in the age of big data.
| arxiv topic:cs.OH |
arxiv_dataset-53541406.6517 | Homogeneous coloured multipartite graphs
math.CO
We classify the countable homogeneous coloured multipartite graphs with any
finite number of parts. By Fraisse's Theorem this amounts to classifying the
families F of pairwise non-embeddable finite coloured multipartite graphs for
which the class Forb(F) of multipartite graphs which forbid these is an
amalgamation class. We show that once we understand such families F in the
quadripartite case, things do not become any more complicated for larger
numbers of parts.
| arxiv topic:math.CO |
arxiv_dataset-53551406.6617 | Eigenvalue ratios of nonnegatively curved graphs
math.SP math.CO
We derive an optimal eigenvalue ratio estimate for finite weighted graphs
satisfying the curvature-dimension inequality $CD(0,\infty)$. This estimate is
independent of the size of the graph and provides a general method to obtain
higher order spectral estimates. The operation of taking Cartesian products is
shown to be an efficient way for constructing new weighted graphs satisfying
$CD(0,\infty)$. We also discuss a higher order Cheeger constant ratio estimate
and related topics about expanders.
| arxiv topic:math.SP math.CO |
arxiv_dataset-53561406.6717 | Homological Algebra for Diffeological Vector Spaces
math.KT
Diffeological spaces are natural generalizations of smooth manifolds,
introduced by J.M.~Souriau and his mathematical group in the 1980's.
Diffeological vector spaces (especially fine diffeological vector spaces) were
first used by P. Iglesias-Zemmour to model some infinite dimensional spaces
in~\cite{I1,I2}. K.~Costello and O.~Gwilliam developed homological algebra for
differentiable diffeological vector spaces in Appendix A of their
book~\cite{CG}. In this paper, we present homological algebra of general
diffeological vector spaces via the projective objects with respect to all
linear subductions, together with some applications in analysis.
| arxiv topic:math.KT |
arxiv_dataset-53571406.6817 | Abundance sensitive points of line profiles in the stellar spectra
astro-ph.SR
Many abundance studies are based on spectrum synthesis and $\chi$-squared
differences between the synthesized and an observed spectrum. Much of the
spectra so compared depend only weakly on the elemental abundances. Logarithmic
plots of line depths rather than relative flux make this more apparent. We
present simulations that illustrate a simple method for finding regions of the
spectrum most sensitive to abundance, and also some caveats for using such
information. As expected, we find that weak features are the most sensitive.
Equivalent widths of weak lines are ideal features, because of their
sensitivity to abundances, and insensitivity to factors that broaden the line
profiles. The wings of strong lines can also be useful, but it is essential
that the broadening mechanisms be accurately known. The very weakest features,
though sensitive to abundance, should be avoided or used with great caution
because of uncertainty of continuum placement as well as numerical
uncertainties associated with the subtraction of similar numbers.
| arxiv topic:astro-ph.SR |
arxiv_dataset-53581406.6917 | Time and Space separation in General Relativity
math-ph math.MP
Let $(M,g)$ be a spacetime. That is, $M$ is a real manifold of dimension $4$
equipped with a Lorentzian metric $g$. We show that any separation of time and
space in $M$ is equivalent to introducing a (non-smooth) Riemann metric $h$. If
$h$ is smooth, it induces a smooth line bundle $T_p\rightarrow M$, whose any
fiber is generated by a time-like vector, called the time bundle. Whether
$(M,g,h)$ is time orientable or not corresponds to whether this line bundle is
trivial or not. As well-known, the last condition is characterized by the first
Stiefel-Whitney class $w^1(T_p)\in H^1(M,\mathbb{Z}/2)$. We then define a
partial time orientation of $M$ as a section of the line bundle $T\rightarrow
M$. As applications, we discuss time and space differentiations on $M$.
| arxiv topic:math-ph math.MP |
arxiv_dataset-53591406.7017 | Longest common subsequences in sets of words
math.CO
Given a set of $t$ words of length $n$ over a $k$-letter alphabet, it is
proved that there exists a common subsequence among two of them of length at
least $\frac{n}{k}+cn^{1-1/(t-k-2)}$, for some $c>0$ depending on $k$ and $t$.
This is sharp up to the value of $c$.
| arxiv topic:math.CO |
arxiv_dataset-53601406.7117 | A Complete Review of Controlling the FDR in a Multiple Comparison
Problem Framework -- The Benjamini-Hochberg Algorithm
stat.ME
This paper is a review of the popular Benjamini Hochberg Method and other
related useful methods of Multiple Hypothesis testing. This is written with the
purpose of serving a short but complete easy to understand review of the main
article with proper background. The paper titled 'Controlling the False
Discovery Rate-a practical and powerful Approach to multiple Testing' by
benjamini et. al.[1] proposes a new framework of controlling the False
Discovery Rate in a Multiple Hypothesis testing problem. It has been claimed
that the procedure proposed in the paper results in a substantial gain in power
more applicable in case of problems which call for False discovery rate (FDR)
control rather than Familywise Error Rate (FWER). The proposed method uses a
simple Bonferroni type procedure for FDR control.
| arxiv topic:stat.ME |
arxiv_dataset-53611406.7217 | Some inequalities for differentiable convex functions with applications
math.CA
In this paper, the Authors establish a new identity for differentiable
functions. By the well-known H\"older and power mean inequality, they obtain
some integral inequalities related to the convex functions and apply these
inequalities to special means.
| arxiv topic:math.CA |
arxiv_dataset-53621406.7317 | Combinatorial Interpretation of General Eulerian Numbers
math.CO
Since 1950s, mathematicians have successfully interpreted the traditional
Eulerian numbers and $q-$Eulerian numbers combinatorially. In this paper, the
authors give a combinatorial interpretation to the general Eulerian numbers
defined on general arithmetic progressions { a, a+d, a+2d,...}.
| arxiv topic:math.CO |
arxiv_dataset-53631406.7417 | Euler and the German Princess
math.HO
In 1760, Leonhard Euler began to write beautiful Letters to a German Princess
on Diverse Subjects of Physics and Philosophy. Much has been written about
Euler and his work, but we wonder, who was the princess? How did she become
involved with the greatest mathematician of her time? The princess was a
fifteen year old named Friederike Charlotte von Brandenburg-Schwedt. In this
article we explore her story and the nature of the letters.
| arxiv topic:math.HO |
arxiv_dataset-53641406.7517 | On fractional Choquard equations
math.AP
We investigate a class of nonlinear Schrodinger equations with a generalized
Choquard nonlinearity and fractional diffusion. We obtain regularity,
existence, nonexistence, symmetry as well as decays properties.
| arxiv topic:math.AP |
arxiv_dataset-53651406.7617 | Parallel acceleration due to the radial electric field in a magnetized
plasma with low-frequency turbulence
physics.plasm-ph
A new physical mechanism of the parallel acceleration of a turbulent
magnetized plasma is discovered by using a Fokker-Planck phase space stochastic
transport equation. It is found that the random walk of a charged particle is
correlated with the random change of the parallel velocity due to the radial
electric field and the magnetic moment conservation. This correlation leads to
a parallel acceleration of the plasma with a finite parallel fluid flow.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-53661406.7717 | Study of gamma induced defects in Nd doped phosphate glass using UV-Vis
spectrophotometer and photophysics beamline on INDUS-1
cond-mat.mtrl-sci physics.optics
Nd doped phosphate glasses have been studied before and after gamma
irradiation in order to understand the effect of glass composition and
radiation induced defects on the optical properties of glasses. UV, Vis
absorption and photoluminescence spectra of these glasses are found strongly
dependent on the composition of glass matrix, particularly on the ratio of
oxygen (O) and neodymium (Nd) concentration obtained from energy dispersive
X-ray spectroscopic (EDX) measurement. Gamma irradiation of glass modifies the
transmission below 700 nm due to generation of some new absorption bands
corresponding to different types of defects. Observations indicate toward
possibility of change in the valence state of Nd3+ to Nd2+ and generation of
oxygen vacancies in glass matrix. EDX and X-ray photoelectron spectroscopic
(XPS) measurements indicate change in the composition of glasses particularly
decrease in the relative concentration of oxygen in glass samples after gamma
irradiation.
| arxiv topic:cond-mat.mtrl-sci physics.optics |
arxiv_dataset-53671406.7817 | Newton algorithm for Hamiltonian characterization in quantum control
quant-ph
We propose a Newton algorithm to characterize the Hamiltonian of a quantum
system interacting with a given laser field. The algorithm is based on the
assumption that the evolution operator of the system is perfectly known at a
fixed time. The computational scheme uses the Crank-Nicholson approximation to
explicitly determine the derivatives of the propagator with respect to the
Hamiltonians of the system. In order to globalize this algorithm, we use a
continuation method that improves its convergence properties. This technique is
applied to a two-level quantum system and to a molecular one with a double-well
potential. The numerical tests show that accurate estimates of the unknown
parameters are obtained in some cases. We discuss the numerical limits of the
algorithm in terms of basin of convergence and non uniqueness of the solution.
| arxiv topic:quant-ph |
arxiv_dataset-53681407.0043 | Edge-colorings of $K_{m,n}$ which Forbid Multicolored Cycles
math.CO
A subgraph in an edge-colored graph is multicolored if all its edges receive
distinct colors. In this paper, we study the proper edge-colorings of the
complete bipartite graph $K_{m,n}$ which forbid multicolored cycles. Mainly, we
prove that (1) for any integer $k\geq 2$, if $n\geq 5k-6$, then any properly
$n$-edge-colored $K_{k,n}$ contains a multicolored $C_{2k}$, and (2) determine
the order of the properly edge-colored complete bipartite graphs which forbid
multicolored $C_6$.
| arxiv topic:math.CO |
arxiv_dataset-53691407.0143 | A nonconventional local limit theorem
math.PR
We extend local limit theorem type results to nonconventional sums of the
form $S_N=\sum_{n=1}^NF(\xi_n,\xi_{2n},...,\xi_{\ell n})$.
| arxiv topic:math.PR |
arxiv_dataset-53701407.0243 | A priori estimates for semistable solutions of semilinear elliptic
equations
math.AP
We consider positive semistable solutions $u$ of $Lu+f(u)=0$ with zero
Dirichlet boundary condition, where $L$ is a uniformly elliptic operator and
$f\in C^2$ is a positive, nondecreasing, and convex nonlinearity which is
superlinear at infinity. Under these assumptions, the boundedness of all
semistable solutions is expected up to dimension $n\leq 9$, but only
established for $n\leq 4$.
In this paper we prove the $L^\infty$ bound up to dimension $n=5$ under the
following further assumption on $f$: for every $\varepsilon>0$, there exist
$T=T(\varepsilon)$ and $C=C(\varepsilon)$ such that $f'(t)\leq
Cf(t)^{1+\varepsilon}$ for all $t>T$. This bound follows from a $L^p$-estimate
for $f'(u)$ for every $p<3$ and $n\geq 2$. Under a similar but more restrictive
assumption on $f$, we also prove the $L^\infty$ estimate when $n=6$. We remark
that our results do not assume any lower bound on $f'$.
| arxiv topic:math.AP |
arxiv_dataset-53711407.0343 | Expected degree of finite preferential attachment networks
cs.SI nlin.AO
We provide an analytic expression for the quantity described in the title.
Namely, we perform a preferential attachment growth process to generate a
scale-free network. At each stage we add a new node with $m$ new links. Let $k$
denote the degree of a node, and $N$ the number of nodes in the network. The
degree distribution is assumed to converge to a power-law (for $k\geq m$) of
the form $k^{-\gamma}$ and we obtain an exact implicit relationship for
$\gamma$, $m$ and $N$. We verify this with numerical calculations over several
orders of magnitude. Although this expression is exact, it provides only an
implicit expression for $\gamma(m)$. Nonetheless, we provide a reasonable guess
as to the form of this curve and perform curve fitting to estimate the
parameters of that curve --- demonstrating excellent agreement between
numerical fit, theory, and simulation.
| arxiv topic:cs.SI nlin.AO |
arxiv_dataset-53721407.0443 | The EB Factory Project I. A Fast, Neural Net Based, General Purpose
Light Curve Classifier Optimized for Eclipsing Binaries
astro-ph.IM astro-ph.SR
We describe a new neural-net based light curve classifier and provide it with
documentation as a ready-to-use tool for the community. While optimized for
identification and classification of eclipsing binary stars, the classifier is
general purpose, and has been developed for speed in the context of upcoming
massive surveys such as LSST. A challenge for classifiers in the context of
neural-net training and massive data sets is to minimize the number of
parameters required to describe each light curve. We show that a simple and
fast geometric representation that encodes the overall light curve shape,
together with a chi-square parameter to capture higher-order morphology
information results in efficient yet robust light curve classification,
especially for eclipsing binaries. Testing the classifier on the ASAS light
curve database, we achieve a retrieval rate of 98\% and a false-positive rate
of 2\% for eclipsing binaries. We achieve similarly high retrieval rates for
most other periodic variable-star classes, including RR Lyrae, Mira, and delta
Scuti. However, the classifier currently has difficulty discriminating between
different sub-classes of eclipsing binaries, and suffers a relatively low
($\sim$60\%) retrieval rate for multi-mode delta Cepheid stars. We find that it
is imperative to train the classifier's neural network with exemplars that
include the full range of light curve quality to which the classifier will be
expected to perform; the classifier performs well on noisy light curves only
when trained with noisy exemplars. The classifier source code, ancillary
programs, a trained neural net, and a guide for use, are provided.
| arxiv topic:astro-ph.IM astro-ph.SR |
arxiv_dataset-53731407.0543 | Critical behaviour in the nonlinear elastic response of hydrogels
cond-mat.soft cond-mat.mtrl-sci
In this paper we study the elastic response of synthetic hydrogels to an
applied shear stress. The hydrogels studied here have previously been shown to
mimic the behaviour of biopolymer networks when they are sufficiently far above
the gel point. We show that near the gel point they exhibit an elastic response
that is consistent with the predicted critical behaviour of networks near or
below the isostatic point of marginal stability. This point separates rigid and
floppy states, distinguished by the presence or absence of finite linear
elastic moduli. Recent theoretical work has also focused on the response of
such networks to finite or large deformations, both near and below the
isostatic point. Despite this interest, experimental evidence for the existence
of criticality in such networks has been lacking. Using computer simulations,
we identify critical signatures in the mechanical response of sub-isostatic
networks as a function of applied shear stress. We also present experimental
evidence consistent with these predictions. Furthermore, our results show the
existence of two distinct critical regimes, one of which arises from the
nonlinear stretch response of semi-flexible polymers..
| arxiv topic:cond-mat.soft cond-mat.mtrl-sci |
arxiv_dataset-53741407.0643 | The Max-Distance Network Creation Game on General Host Graphs
cs.GT
In this paper we study a generalization of the classic \emph{network creation
game} in the scenario in which the $n$ players sit on a given arbitrary
\emph{host graph}, which constrains the set of edges a player can activate at a
cost of $\alpha \geq 0$ each. This finds its motivations in the physical
limitations one can have in constructing links in practice, and it has been
studied in the past only when the routing cost component of a player is given
by the sum of distances to all the other nodes. Here, we focus on another
popular routing cost, namely that which takes into account for each player its
\emph{maximum} distance to any other player. For this version of the game, we
first analyze some of its computational and dynamic aspects, and then we
address the problem of understanding the structure of associated pure Nash
equilibria. In this respect, we show that the corresponding price of anarchy
(PoA) is fairly bad, even for several basic classes of host graphs. More
precisely, we first exhibit a lower bound of $\Omega (\sqrt{ n / (1+\alpha)})$
for any $\alpha = o(n)$. Notice that this implies a counter-intuitive lower
bound of $\Omega(\sqrt{n})$ for very small values of $\alpha$ (i.e., edges can
be activated almost for free). Then, we show that when the host graph is
restricted to be either $k$-regular (for any constant $k \geq 3$), or a
2-dimensional grid, the PoA is still $\Omega(1+\min\{\alpha,
\frac{n}{\alpha}\})$, which is proven to be tight for
$\alpha=\Omega(\sqrt{n})$. On the positive side, if $\alpha \geq n$, we show
the PoA is $O(1)$. Finally, in the case in which the host graph is very sparse
(i.e., $|E(H)|=n-1+k$, with $k=O(1)$), we prove that the PoA is $O(1)$, for any
$\alpha$.
| arxiv topic:cs.GT |
arxiv_dataset-53751407.0743 | The Beta-Gompertz Distribution
math.ST stat.TH
In this paper, we introduce a new four-parameter generalized version of the
Gompertz model which is called Beta-Gompertz (BG) distribution. It includes
some well-known lifetime distributions such as beta-exponential and generalized
Gompertz distributions as special sub-models. This new distribution is quite
flexible and can be used effectively in modeling survival data and reliability
problems. It can have a decreasing, increasing, and bathtub-shaped failure rate
function depending on its parameters. Some mathematical properties of the new
distribution, such as closed-form expressions for the density, cumulative
distribution, hazard rate function, the $k$th order moment, moment generating
function, Shannon entropy, and the quantile measure are provided. We discuss
maximum likelihood estimation of the BG parameters from one observed sample and
derive the observed Fisher's information matrix. A simulation study is
performed in order to investigate this proposed estimator for parameters. At
the end, in order to show the BG distribution flexibility, an application using
a real data set is presented.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-53761407.0843 | The Gamification Design Problem
cs.HC
Under the assumptions that (i) gamification consists of various types of
users that experience game design elements differently; and (ii) gamification
is deployed in order to achieve some goal in the broadest sense, we pose the
gamification problem as that of assigning each user a game design element that
maximizes their expected contribution in order to achieve that goal. We show
that this problem reduces to a statistical learning problem and suggest matrix
factorization as one solution when user interaction data is given. The
hypothesis is that predictive models as intelligent tools for supporting users
in decision-making may also have potential to support the design process in
gamification.
| arxiv topic:cs.HC |
arxiv_dataset-53771407.0943 | Spectrum Refarming: A New Paradigm of Spectrum Sharing for Cellular
Networks
cs.IT math.IT
Spectrum refarming (SR) refers to a radio resource management technique which
allows different generations of cellular networks to operate in the same radio
spectrum. In this paper, an underlay SR model is proposed, in which an
Orthogonal Frequency Division Multiple Access (OFDMA) system refarms the
spectrum of a Code Division Multiple Access (CDMA) system through intelligently
exploiting the interference margin provided by the CDMA system. We investigate
the mutual effect of the two systems by evaluating the asymptotic
signal-to-interference-plus-noise ratio (SINR) of the users, based on which the
interference margin tolerable by the CDMA system is determined. By using the
interference margin together with the transmit power constraints, the uplink
resource allocation problem of OFDMA system is formulated and solved through
dual decomposition method. Simulation results have verified our theoretical
analysis, and validated the effectiveness of the proposed resource allocation
algorithm and its capability to protect the legacy CDMA users. The proposed SR
system requires the least information flow from the CDMA system to the OFDMA
system, and importantly, no upgrading of legacy CDMA system is needed; thus it
can be deployed by telecom operators to maximize the spectral efficiency of
their cellular networks.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-53781407.1043 | Closing the stop gap
hep-ph hep-ex
Light stops are a hallmark of the most natural realizations of weak-scale
supersymmetry. While stops have been extensively searched for, there remain
open gaps around and below the top mass, due to similarities of stop and top
signals with current statistics. We propose a new fast-track avenue to improve
light stop searches for R-parity conserving supersymmetry, by comparing top
cross section measurements to the theoretical prediction. Stop masses below ~
180 GeV can now be ruled out for a light neutralino. The possibility of a stop
signal contaminating the top mass measurement is also briefly addressed.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-53791407.1143 | Direct detection of cosmic rays: through a new era of precision
measurements of particle fluxes
astro-ph.HE
In the last years the direct measurement of cosmic rays received a push
forward by the possibility of conducting experiments on board long duration
balloon flights, satellites and on the International Space Station. The
increase in the collected statistics and the technical improvements in the
construction of the detectors permit the fluxes measurement to be performed at
higher energies with a reduced discrepancy among different experiments respect
to the past. However, high statistical precision is not always associated to
the needed precision in the estimation of systematics; features in the particle
spectra can be erroneously introduced or hidden. A review and a comparison of
the latest experimental results on direct cosmic rays measurements will be
presented with particular emphasis on their similarities and discrepancies.
| arxiv topic:astro-ph.HE |
arxiv_dataset-53801407.1243 | Complete representation by partial functions for composition,
intersection and antidomain
math.RA math.LO
For representation by partial functions in the signature with intersection,
composition and antidomain, we show that a representation is meet complete if
and only if it is join complete. We show that a representation is complete if
and only if it is atomic, but that not all atomic representable algebras are
completely representable. We show that the class of completely representable
algebras is not axiomatisable by any existential-universal-existential
first-order theory. By giving an explicit representation, we show that the
completely representable algebras form a basic elementary class, axiomatisable
by a universal-existential-universal sentence.
| arxiv topic:math.RA math.LO |
arxiv_dataset-53811407.1343 | Computing Greeks for L\'evy Models: The Fourier Transform Approach
q-fin.PR
The computation of Greeks for exponential L\'evy models are usually
approached by Malliavin Calculus and other methods, as the Likelihood Ratio and
the finite difference method. In this paper we obtain exact formulas for Greeks
of European options based on the Lewis formula for the option value. Therefore,
it is possible to obtain accurate approximations using Fast Fourier Transform.
We will present an exhaustive development of Greeks for Call options. The error
is shown for all Greeks in the Black-Scholes model, where Greeks can be exactly
computed. Other models used in the literature are compared, such as the Merton
and Variance Gamma models. The presented formulas can reach desired accuracy
because our approach generates error only by approximation of the integral.
| arxiv topic:q-fin.PR |
arxiv_dataset-53821407.1443 | Analysis of Yelp Reviews
cs.SI cs.CY physics.soc-ph
In the era of Big Data and Social Computing, the role of customer reviews and
ratings can be instrumental in predicting the success and sustainability of
businesses. In this paper, we show that, despite the apparent subjectivity of
user ratings, there are also external, or objective factors which help to
determine the outcome of a business's reviews. The current model for social
business review sites, such as Yelp, allows data (reviews, ratings) to be
compiled concurrently, which introduces a bias to participants (Yelp Users).
Our work examines Yelp Reviews for businesses in and around college towns. We
demonstrate that an Observer Effect causes data to behave cyclically: rising
and falling as momentum (quantified in user ratings) shifts for businesses.
| arxiv topic:cs.SI cs.CY physics.soc-ph |
arxiv_dataset-53831407.1543 | Dictionary Learning and Tensor Decomposition via the Sum-of-Squares
Method
cs.DS cs.LG stat.ML
We give a new approach to the dictionary learning (also known as "sparse
coding") problem of recovering an unknown $n\times m$ matrix $A$ (for $m \geq
n$) from examples of the form \[ y = Ax + e, \] where $x$ is a random vector in
$\mathbb R^m$ with at most $\tau m$ nonzero coordinates, and $e$ is a random
noise vector in $\mathbb R^n$ with bounded magnitude. For the case $m=O(n)$,
our algorithm recovers every column of $A$ within arbitrarily good constant
accuracy in time $m^{O(\log m/\log(\tau^{-1}))}$, in particular achieving
polynomial time if $\tau = m^{-\delta}$ for any $\delta>0$, and time $m^{O(\log
m)}$ if $\tau$ is (a sufficiently small) constant. Prior algorithms with
comparable assumptions on the distribution required the vector $x$ to be much
sparser---at most $\sqrt{n}$ nonzero coordinates---and there were intrinsic
barriers preventing these algorithms from applying for denser $x$.
We achieve this by designing an algorithm for noisy tensor decomposition that
can recover, under quite general conditions, an approximate rank-one
decomposition of a tensor $T$, given access to a tensor $T'$ that is
$\tau$-close to $T$ in the spectral norm (when considered as a matrix). To our
knowledge, this is the first algorithm for tensor decomposition that works in
the constant spectral-norm noise regime, where there is no guarantee that the
local optima of $T$ and $T'$ have similar structures.
Our algorithm is based on a novel approach to using and analyzing the Sum of
Squares semidefinite programming hierarchy (Parrilo 2000, Lasserre 2001), and
it can be viewed as an indication of the utility of this very general and
powerful tool for unsupervised learning problems.
| arxiv topic:cs.DS cs.LG stat.ML |
arxiv_dataset-53841407.1643 | Two-sided ideals in the ring of differential operators on a
Stanley-Reisner ring
math.AC
Let R be a Stanley-Reisner ring (that is, a reduced monomial ring) with
coefficients in a domain k, and K its associated simplicial complex. Also let
D_k(R) be the ring of k-linear differential operators on R. We give two
different descriptions of the two-sided ideal structure of D_k(R) as being in
bijection with certain well-known subcomplexes of K; one based on explicit
computation in the Weyl algebra, valid in any characteristic, and one valid in
characteristic p based on the Frobenius splitting of R. A result of Traves
[Tra99] on the D_k(R)-module structure of R is also given a new proof and
different interpretation using these techniques.
| arxiv topic:math.AC |
arxiv_dataset-53851407.1743 | Phase Mixing of Alfv\'en Waves Near a 2D Magnetic Null Point
astro-ph.SR
The propagation of linear Alfv\'en wave pulses in an inhomogeneous plasma
near a 2D coronal null point is investigated. When a uniform plasma density is
considered, it is seen that an initially planar Alfv\'en wavefront remains
planar, despite the varying equilibrium Alfv\'en speed, and that all the wave
collects at the separatrices. Thus, in the non-ideal case, these Alfv\'enic
disturbances preferentially dissipate their energy at these locations. For a
non-uniform equilibrium density, it is found that the Alfv\'en wavefront is
significantly distorted away from the initially planar geometry, inviting the
possibility of dissipation due to phase mixing. Despite this however, we
conclude that for the Alfv\'en wave, current density accumulation and
preferential heating still primarily occur at the separatrices, even when an
extremely non-uniform density profile is considered.
| arxiv topic:astro-ph.SR |
arxiv_dataset-53861407.1843 | Constraining the Low-Mass Slope of the Star Formation Sequence at
0.5<z<2.5
astro-ph.GA
We constrain the slope of the star formation rate ($\log\Psi$) to stellar
mass ($\log\mathrm{M_{\star}}$) relation down to
$\log(\mathrm{M_{\star}/M_{\odot}})=8.4$
($\log(\mathrm{M_{\star}/M_{\odot}})=9.2$) at $z=0.5$ ($z=2.5$) with a
mass-complete sample of 39,106 star-forming galaxies selected from the 3D-HST
photometric catalogs, using deep photometry in the CANDELS fields. For the
first time, we find that the slope is dependent on stellar mass, such that it
is steeper at low masses ($\log\mathrm{\Psi}\propto\log\mathrm{M_{\star}}$)
than at high masses
($\log\mathrm{\Psi}\propto(0.3-0.6)\log\mathrm{M_{\star}}$). These steeper low
mass slopes are found for three different star formation indicators: the
combination of the ultraviolet (UV) and infrared (IR), calibrated from a
stacking analysis of Spitzer/MIPS 24$\mu$m imaging; $\beta$-corrected UV SFRs;
and H$\alpha$ SFRs. The normalization of the sequence evolves differently in
distinct mass regimes as well: for galaxies less massive than
$\log(\mathrm{M_{\star}/M_{\odot}})<10$ the specific SFR
($\Psi/\mathrm{M_{\star}}$) is observed to be roughly self-similar with
$\Psi/\mathrm{M_{\star}}\propto(1+z)^{1.9}$, whereas more massive galaxies show
a stronger evolution with $\Psi/\mathrm{M_{\star}}\propto(1+z)^{2.2-3.5}$ for
$\log(\mathrm{M_{\star}/M_{\odot}})=10.2-11.2$. The fact that we find a steep
slope of the star formation sequence for the lower mass galaxies will help
reconcile theoretical galaxy formation models with the observations. The
results of this study support the analytical conclusions of Leja et al. (2014).
| arxiv topic:astro-ph.GA |
arxiv_dataset-53871407.1943 | WSClean: an implementation of a fast, generic wide-field imager for
radio astronomy
astro-ph.IM
Astronomical widefield imaging of interferometric radio data is
computationally expensive, especially for the large data volumes created by
modern non-coplanar many-element arrays. We present a new widefield
interferometric imager that uses the w-stacking algorithm and can make use of
the w-snapshot algorithm. The performance dependencies of CASA's w-projection
and our new imager are analysed and analytical functions are derived that
describe the required computing cost for both imagers. On data from the
Murchison Widefield Array, we find our new method to be an order of magnitude
faster than w-projection, as well as being capable of full-sky imaging at full
resolution and with correct polarisation correction. We predict the computing
costs for several other arrays and estimate that our imager is a factor of 2-12
faster, depending on the array configuration. We estimate the computing cost
for imaging the low-frequency Square-Kilometre Array observations to be 60
PetaFLOPS with current techniques. We find that combining w-stacking with the
w-snapshot algorithm does not significantly improve computing requirements over
pure w-stacking. The source code of our new imager is publicly released.
| arxiv topic:astro-ph.IM |
arxiv_dataset-53881407.2043 | Off-diagonal matrix elements of local operators in many-body quantum
systems
cond-mat.stat-mech cond-mat.quant-gas cond-mat.str-el quant-ph
In the time evolution of isolated quantum systems out of equilibrium, local
observables generally relax to a long-time asymptotic value, governed by the
expectation values (diagonal matrix elements) of the corresponding operator in
the eigenstates of the system. The temporal fluctuations around this value,
response to further perturbations, and the relaxation toward this asymptotic
value, are all determined by the off-diagonal matrix elements. Motivated by
this non-equilibrium role, we present generic statistical properties of
off-diagonal matrix elements of local observables in two families of
interacting many-body systems with local interactions. Since integrability (or
lack thereof) is an important ingredient in the relaxation process, we analyze
models that can be continuously tuned to integrability. We show that, for
generic non-integrable systems, the distribution of off-diagonal matrix
elements is a gaussian centered at zero. As one approaches integrability, the
peak around zero becomes sharper, so that the distribution is approximately a
combination of two gaussians. We characterize the proximity to integrability
through the deviation of this distribution from a gaussian shape. We also
determine the scaling dependence on system size of the average magnitude of
off-diagonal matrix elements.
| arxiv topic:cond-mat.stat-mech cond-mat.quant-gas cond-mat.str-el quant-ph |
arxiv_dataset-53891407.2143 | Parameterized Algorithmics for Computational Social Choice: Nine
Research Challenges
cs.MA cs.GT
Computational Social Choice is an interdisciplinary research area involving
Economics, Political Science, and Social Science on the one side, and
Mathematics and Computer Science (including Artificial Intelligence and
Multiagent Systems) on the other side. Typical computational problems studied
in this field include the vulnerability of voting procedures against attacks,
or preference aggregation in multi-agent systems. Parameterized Algorithmics is
a subfield of Theoretical Computer Science seeking to exploit meaningful
problem-specific parameters in order to identify tractable special cases of in
general computationally hard problems. In this paper, we propose nine of our
favorite research challenges concerning the parameterized complexity of
problems appearing in this context.
| arxiv topic:cs.MA cs.GT |
arxiv_dataset-53901407.2243 | Neutrino Lighthouse at Sagittarius A*
astro-ph.HE hep-ph
We investigate whether a subset of high-energy events observed by IceCube may
be due to neutrinos from Sagittarius A*. We check both spatial and temporal
coincidences of IceCube events with other transient activities of Sagittarius
A*. Among the seven IceCube shower events nearest to the galactic center, we
have found that event 25 has a time very close to (around three hours after)
the brightest X-ray flare of Sagittarius A* observed by the Chandra X-ray
Observatory with a p-value of 0.9%. Furthermore, two of the seven events
occurred within one day of each other (there is a 1.6% probability that this
would occur for a random distribution in time). Thus, the determination that
some IceCube events occur at similar times as X-ray flares and others occur in
a burst could be the smoking gun that Sagittarius A* is a point source of very
high energy neutrinos. We point out that if IceCube galactic center neutrino
events originate from charged pion decays, then TeV gamma rays should come from
neutral pion decays at a similar rate. We show that the CTA, HAWC, H.E.S.S. and
VERITAS experiments should be sensitive enough to test this.
| arxiv topic:astro-ph.HE hep-ph |
arxiv_dataset-53911407.2343 | Fast Separable Non-Local Means
cs.CV
We propose a simple and fast algorithm called PatchLift for computing
distances between patches (contiguous block of samples) extracted from a given
one-dimensional signal. PatchLift is based on the observation that the patch
distances can be efficiently computed from a matrix that is derived from the
one-dimensional signal using lifting; importantly, the number of operations
required to compute the patch distances using this approach does not scale with
the patch length. We next demonstrate how PatchLift can be used for patch-based
denoising of images corrupted with Gaussian noise. In particular, we propose a
separable formulation of the classical Non-Local Means (NLM) algorithm that can
be implemented using PatchLift. We demonstrate that the PatchLift-based
implementation of separable NLM is few orders faster than standard NLM, and is
competitive with existing fast implementations of NLM. Moreover, its denoising
performance is shown to be consistently superior to that of NLM and some of its
variants, both in terms of PSNR/SSIM and visual quality.
| arxiv topic:cs.CV |
arxiv_dataset-53921407.2443 | Wave amplification in the framework of forced nonlinear Schrodinger
equation: the rogue wave context
physics.flu-dyn
Irregular waves which experience the time-limited external forcing within the
framework of the nonlinear Schrodinger (NLS) equation are studied numerically.
It is shown that the adiabatically slow pumping (the time scale of forcing is
much longer than the nonlinear time scale) results in selective enhancement of
the solitary part of the wave ensemble. The slow forcing provides eventually
wider wavenumber spectra, larger values of kurtosis and higher probability of
large waves. In the opposite case of rapid forcing the nonlinear waves readjust
passing through the stage of fast surges of statistical characteristics. Single
forced envelope solitons are considered with the purpose to better identify the
role of coherent wave groups. An approximate description on the basis of
solutions of the integrable NLS equation is provided. Applicability of the
Benjamin - Feir Index to forecasting of conditions favourable for rogue waves
is discussed.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-53931407.2543 | X-ray line in Radiative Neutrino Model with Global $U(1)$ Symmetry
hep-ph
We study a three loop induced radiative neutrino model with global $U(1)$
symmetry at TeV scale, in which we consider two component dark matter
particles. We discuss the possibility to explain the X-ray line signal at about
3.55 keV recently reported by XMN-Newton X-ray observatory using data of
various galaxy clusters and Andromeda galaxy. Subsequently, we also discuss to
show that sizable muon anomalous magnetic moment, a discrepancy of the
effective number of neutrino species $\Delta N_{\rm eff}\approx$ 0.39, and
scattering cross section detected by direct detection searches can be derived.
| arxiv topic:hep-ph |
arxiv_dataset-53941407.2643 | Thermal Properties of Asymmetric Nuclear Matter
nucl-th
The thermal properties of asymmetric nuclear matter are investigated in a
relativistic mean- field approach. We start from free space NN-interactions and
derive in-medium self-energies by Dirac-Brueckner theory. By the DDRH procedure
we derive in a self-consistent approach density- dependent meson-baryon
vertices. At the mean-field level, we include isoscalar and isovector scalar
and vector interactions. The nuclear equation of state is investigated for a
large range of total baryon densities up to the neutron star regime, the full
range of asymmetries from symmetric nuclear matter to pure neutron matter, and
temperatures up to T~100 MeV. The isovector-scalar self-energies are found to
modify strongly the thermal properties of asymmetric nuclear matter. A striking
result is the change of phase transitions when isovector-scalar self-energies
are included.
| arxiv topic:nucl-th |
arxiv_dataset-53951407.2743 | Isothermal Navier-Stokes Equations and Radon Transform
math.AP
In the paper we prove the existence results for initial-value boundary value
problems for compressible isothermal Navier-Stokes equations. We restrict
ourselves to 2D case of a problem with no-slip condition for nonstationary
motion of viscous compressible isothermal fluid. However, the technique of
modeling and analysis presented here is general and can be used for 3D
problems.
| arxiv topic:math.AP |
arxiv_dataset-53961407.2843 | Is there a "$\Delta$-isobar puzzle" in the physics of neutron stars?
astro-ph.SR hep-ph nucl-th
We discuss the formation of $\Delta$ isobars in neutron star matter. We show
that their threshold density strictly correlates with the density derivative of
the symmetry energy of nuclear matter, the $L$ parameter. By restricting $L$ to
the range of values indicated by recent experimental and theoretical analysis,
i.e. $40$ MeV $\lesssim L \lesssim 62$ MeV, we find that $\Delta$ isobars
appear at a density of the order of 2$\div$3 times nuclear matter saturation
density, i.e. the same range for the appearance of hyperons. The range of
values of the couplings of the $\Delta$s with the mesons is restricted by the
analysis of the data obtained from photoabsorption, electron and pion
scattering on nuclei. If the potential of the $\Delta$ in nuclear matter is
close to the one indicated by the experimental data then the equation of state
becomes soft enough that a "$\Delta$ puzzle" exists, similar to the "hyperon
puzzle" widely discussed in the literature.
| arxiv topic:astro-ph.SR hep-ph nucl-th |
arxiv_dataset-53971407.2943 | Empirical Study of Simulated Two-planet Microlensing Event
astro-ph.EP
We undertake the first study of two-planet microlensing models recovered from
simulations of microlensing events generated by realistic multi-planet systems
in which 292 planetary events including 16 two-planet events were detected from
6690 simulated light curves. We find that when two planets are recovered, their
parameters are usually close to those of the two planets in the system most
responsible for the perturbations. However, in one of the 16 examples, the
apparent mass of both detected planets was more than doubled by the unmodeled
influence of a third, massive planet. This fraction is larger than, but
statistically consistent with, the roughly 1.5% rate of serious mass errors due
to unmodeled planetary companions for the 274 cases from the same simulation in
which a single planet is recovered. We conjecture that an analogous effect due
to unmodeled stellar companions may occur more frequently. For seven out of 23
cases in which two planets in the system would have been detected separately,
only one planet was recovered because the perturbations due to the two planets
had similar forms. This is a small fraction (7/274) of all recovered
single-planet models, but almost a third of all events that might plausibly
have led to two-planet models. Still, in these cases, the recovered planet
tends to have parameters similar to one of the two real planets most
responsible for the anomaly.
| arxiv topic:astro-ph.EP |
arxiv_dataset-53981407.3043 | Stabilized Finite Element Approximation of the Mean Curvature Vector on
Closed Surfaces
math.NA
We develop a stabilized discrete Laplace-Beltrami operator that is used to
compute an approximate mean curvature vector which enjoys convergence of order
one in L2. The stabilization is of gradient jump type and we consider both
standard meshed surfaces and so called cut surfaces that are level sets of
piecewise linear distance functions. We prove a priori error estimates and
verify the theoretical results numerically.
| arxiv topic:math.NA |
arxiv_dataset-53991407.3143 | Permanence of approximation properties for discrete quantum groups
math.OA math.GR math.QA
We prove several results on the permanence of weak amenability and the
Haagerup property for discrete quantum groups. In particular, we improve known
facts on free products by allowing amalgamation over a finite quantum subgroup.
We also define a notion of relative amenability for discrete quantum groups and
link it with amenable equivalence of von Neumann algebras, giving additional
permanence properties.
| arxiv topic:math.OA math.GR math.QA |
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