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arxiv_dataset-34001205.0999 | Fluid depletion in shear bands
cond-mat.soft cond-mat.mtrl-sci physics.comp-ph
How does pore liquid reconfigure within shear bands in wet granular media?
Conventional wisdom predicts that liquid is drawn into dilating granular media.
We, however, find a depletion of liquid in shear bands despite increased
porosity due to dilatancy. This apparent paradox is resolved by a microscale
model for liquid transport at low liquid contents induced by rupture and
reconfiguration of individual liquid bridges. Measured liquid content profiles
show macroscopic depletion bands similar to results of numerical simulations.
We derive a modified diffusion description for rupture-induced liquid
migration.
| arxiv topic:cond-mat.soft cond-mat.mtrl-sci physics.comp-ph |
arxiv_dataset-34011205.1099 | From Knothe's rearrangement to Brenier's optimal transport map
math.OC math.AP
The Brenier optimal map and the Knothe-Rosenblatt rearrangement are two
instances of a transport map, that is to say a map sending one measure onto
another. The main interest of the former is that it solves the
Monge-Kantorovich optimal transport problem, while the latter is very easy to
compute, being given by an explicit formula. A few years ago, Carlier,
Galichon, and Santambrogio showed that the Knothe rearrangement could be seen
as the limit of the Brenier map when the quadratic cost degenerates. In this
paper, we prove that on the torus (to avoid boundary issues), when all the data
are smooth, the evolution is also smooth, and is entirely determined by a PDE
for the Kantorovich potential (which determines the map), with a subtle initial
condition. The proof requires the use of the Nash-Moser inverse function
theorem. This result generalizes the ode discovered by Carlier, Galichon, and
Santambrogio when one measure is uniform and the other is discrete, and could
pave to way to new numerical methods for optimal transportation.
| arxiv topic:math.OC math.AP |
arxiv_dataset-34021205.1199 | Fractional wave equation and damped waves
math-ph math.AP math.MP
In this paper, a fractional generalization of the wave equation that
describes propagation of damped waves is considered. In contrast to the
fractional diffusion-wave equation, the fractional wave equation contains
fractional derivatives of the same order $\alpha,\ 1\le \alpha \le 2$ both in
space and in time. We show that this feature is a decisive factor for
inheriting some crucial characteristics of the wave equation like a constant
propagation velocity of both the maximum of its fundamental solution and its
gravity and mass centers. Moreover, the first, the second, and the Smith
centrovelocities of the damped waves described by the fractional wave equation
are constant and depend just on the equation order $\alpha$. The fundamental
solution of the fractional wave equation is determined and shown to be a
spatial probability density function evolving in time that possesses finite
moments up to the order $\alpha$. To illustrate analytical findings, results of
numerical calculations and numerous plots are presented.
| arxiv topic:math-ph math.AP math.MP |
arxiv_dataset-34031205.1299 | Traveling Baseball Players' Problem in Korea
physics.soc-ph physics.data-an
We study the so-called the traveling tournament problem (TTP), to find an
optimal tournament schedule. Differently from the original TTP, in which the
total travel distance of all the participants is the objective function to
minimize, we instead seek to maximize the fairness of the round robin
tournament schedule of the Korean Baseball League. The standard deviation of
the travel distances of teams is defined as the energy function, and the
Metropolis Monte-Carlo method combined with the simulated annealing technique
is applied to find the ground state configuration. The resulting tournament
schedule is found to satisfy all the constraint rules set by the Korean
Baseball Organization, but with drastically increased fairness in traveling
distances.
| arxiv topic:physics.soc-ph physics.data-an |
arxiv_dataset-34041205.1399 | Multisetting Bell inequalities for $N$ spins-1 avoiding KS contradiction
quant-ph
Bell's theorem for systems more complicated than two qubits faces a hidden,
as yet undiscussed, problem. One of the methods to derive Bell's inequalities
is to assume existence of joint probability distribution for measurement
results for all settings in the given experiment. However for spins-1, one
faces the problem that eigenvalues of observables do not allow a consistent
algebra if one allows all possible settings on each side (Bell 1966
contradiction), or some specific sets (leading to a Kochen-Specker 1967
contradiction). We show here that by choosing special set of settings which
never lead to inconsistent algebra of eigenvalues, one can still derive
multisetting Bell inequalities, and that they are robustly violated. Violation
factors increase with the number of subsystems. The inequalities involve only
spin observables, we do not allow all possible qutrit observables, still the
violations are strong.
| arxiv topic:quant-ph |
arxiv_dataset-34051205.1499 | Different reactions to adverse neighborhoods in games of cooperation
physics.soc-ph q-bio.PE
In social dilemmas, cooperation among randomly interacting individuals is
often difficult to achieve. The situation changes if interactions take place in
a network where the network structure jointly evolves with the behavioral
strategies of the interacting individuals. In particular, cooperation can be
stabilized if individuals tend to cut interaction links when facing adverse
neighborhoods. Here we consider two different types of reaction to adverse
neighborhoods, and all possible mixtures between these reactions. When faced
with a gloomy outlook, players can either choose to cut and rewire some of
their links to other individuals, or they can migrate to another location and
establish new links in the new local neighborhood. We find that in general
local rewiring is more favorable for the evolution of cooperation than
emigration from adverse neighborhoods. Rewiring helps to maintain the diversity
in the degree distribution of players and favors the spontaneous emergence of
cooperative clusters. Both properties are known to favor the evolution of
cooperation on networks. Interestingly, a mixture of migration and rewiring is
even more favorable for the evolution of cooperation than rewiring on its own.
While most models only consider a single type of reaction to adverse
neighborhoods, the coexistence of several such reactions may actually be an
optimal setting for the evolution of cooperation.
| arxiv topic:physics.soc-ph q-bio.PE |
arxiv_dataset-34061205.1599 | The autocorrelation of the Mobius function and Chowla's conjecture for
the rational function field
math.NT math.DS
We prove a function field version of Chowla's conjecture on the
autocorrelation of the Mobius function in the limit of a large finite field.
| arxiv topic:math.NT math.DS |
arxiv_dataset-34071205.1699 | Molecular structures in charmonium spectrum: The $XYZ$ puzzle
hep-ph nucl-th
We study in the framework of a constituent quark model the possible
contributions of molecular structures to the XYZ charmonium like states. We
analyze simultaneously the $c\bar{c}$ structures and the possible molecular
components in a formalism which allows us to treat channels below and above
thresholds. The only molecular state found in the $1^{++}$ sector correspond to
the X(3872). Molecular resonances also appear with other quantum numbers. So,
the so called Y(3940) and the X(3915) are suggested to be $J^{PC}=0^{++}$
charmonium states. In the $J^{PC}=1^{--}$ sector we also found significant
contributions of the molecular structures which can affect the phenomenology.
| arxiv topic:hep-ph nucl-th |
arxiv_dataset-34081205.1799 | Asymmetric velocity anisotropies in remnants of collisionless mergers
astro-ph.CO
Dark matter haloes in cosmological N-body simulations are affected by
processes such as mergers, accretion and the gravitational interaction with
baryonic matter. Typically the analysis of dark matter haloes is performed in
spherical or elliptical bins and the velocity distributions are often assumed
to be constant within those bins. However, the velocity anisotropy, which
describes differences between the radial and tangential velocity dispersion,
has recently been show to have a strong dependence on direction in the triaxial
halos formed in cosmological simulations. In this study we derive properties of
particles in cones parallel or perpendicular to the collision axis of merger
remnants. We find that the velocity anisotropy has a strong dependence on
direction. The finding that the direction-dependence of the velocity anisotropy
of a halo depends on the merger history, explains the existence of such trends
in cosmological simulations. It also explains why a large diversity is seen in
the velocity anisotropy profiles in the outer parts of high-resolution
simulations of cosmological haloes.
| arxiv topic:astro-ph.CO |
arxiv_dataset-34091205.1899 | Two-component solitons under a spatially modulated linear coupling:
Inverted photonic crystals and fused couplers
physics.optics nlin.PS
We study two-component solitons and their symmetry-breaking bifurcations
(SBBs) in linearly coupled photonic systems with a spatially inhomogeneous
strength of the coupling. One system models an inverted virtual photonic
crystal, built by periodically doping the host medium with atoms implementing
the electromagnetically induced transparency (EIT). In this system, two
soliton-forming probe beams with different carrier frequencies are mutually
coupled by the EIT-induced effective linear interconversion. The system is
described by coupled nonlinear Schr\"{o}dinger (NLS) equations for the probes,
with the linear-coupling constant periodically modulated in space according to
the density distribution of the active atoms. The type of the SBB changes from
sub- to supercritical with the increase of the total power of the probe beams,
which does not occur in systems with constant linear-coupling constants.
Qualitatively similar results for the SBB of two-component solitons are
obtained, in an exact analytical form, in the model of a fused dual-core
waveguide, with the linear coupling concentrated at a point.
| arxiv topic:physics.optics nlin.PS |
arxiv_dataset-34101205.1999 | Local Gating of an Ir(111) Surface Resonance by Graphene Islands
cond-mat.mes-hall
The influence of graphene islands on the electronic structure of the Ir(111)
surface is investigated. Scanning tunneling spectroscopy (STS) indicates the
presence of a two-dimensional electron gas with a binding energy of -160meV and
an effective mass of -0.18m_e underneath single-layer graphene on the Ir(111)
surface. Density functional calculations reveal that the STS features are
predominantly due to a holelike surface resonance of the Ir(111) substrate.
Nanometer-sized graphene islands act as local gates, which shift and confine
the surface resonance.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-34111205.2099 | Attractor horizons in six-dimensional type IIB supergravity
hep-th
We consider near horizon geometries of extremal black holes in
six-dimensional type IIB supergravity. In particular, we use the entropy
function formalism to compute the charges and thermodynamic entropy of these
solutions. We also comment on the role of attractor mechanism in understanding
the entropy of the Hopf T-dual solutions in type IIA supergravity.
| arxiv topic:hep-th |
arxiv_dataset-34121205.2199 | Gamma Resonances near Threshold for the Production of Thermal
Photoneutrons
nucl-ex
We have determined the positions of the (gamma,n) resonances and upper limits
for the integrated cross sections for the (gamma,n) reactions, using data for
the inverse process (n,gamma). With the aid of these data we have estimated the
number of low-energy neutrons which can be generated by the irradiation of a
target with a gamma-ray beam. Among the reactions producing thermal neutrons
via (gamma,n) reaction we mention 185Re(gamma,n)184Re with an upper limit of
the integrated cross section of 2.4 b-eV, and 178Hf(gamma,n)177Hf with an upper
limit of the integrated cross section of 0.9 b-eV.
| arxiv topic:nucl-ex |
arxiv_dataset-34131205.2299 | Electricity price modeling and asset valuation: a multi-fuel structural
approach
q-fin.PR
We introduce a new and highly tractable structural model for spot and
derivative prices in electricity markets. Using a stochastic model of the bid
stack, we translate the demand for power and the prices of generating fuels
into electricity spot prices. The stack structure allows for a range of
generator efficiencies per fuel type and for the possibility of future changes
in the merit order of the fuels. The derived spot price process captures
important stylized facts of historical electricity prices, including both
spikes and the complex dependence upon its underlying supply and demand
drivers. Furthermore, under mild and commonly used assumptions on the
distributions of the input factors, we obtain closed-form formulae for
electricity forward contracts and for spark and dark spread options. As merit
order dynamics and fuel forward prices are embedded into the model, we capture
a much richer and more realistic dependence structure than can be achieved by
classical reduced-form models. We illustrate these advantages by comparing with
Margrabe's formula and a simple cointegration model, and highlight important
implications for the valuation of power plants.
| arxiv topic:q-fin.PR |
arxiv_dataset-34141205.2399 | Increasing the Number of TeV Blazars with Parsec-Scale Kinematics
astro-ph.HE
We report on our observations of the parsec-scale radio jet structures of
five blazars that have been detected by ground-based TeV gamma-ray telescopes.
These five blazars all belong to the class of high-frequency peaked BL Lac
objects (HBLs), which are the most common blazar type detected at the TeV
energy range. Because of their relative faintness in the radio, these HBLs are
not well represented in other radio blazar surveys. Our observations consist of
five epochs of Very Long Baseline Array (VLBA) imaging from 2006 to 2009, of
each of the five blazars 1ES 1101-232, Markarian 180, 1ES 1218+304, PG
1553+113, and H 2356-309, at frequencies from 5 to 22 GHz. Fundamental jet
properties, including the apparent jet speeds, that can be measured from these
multi-epoch series of VLBA images are presented and compared with other
gamma-ray blazars. Confirming prior work, we find that the TeV HBLs have
significantly slower apparent jet speeds than radio-selected blazars. Together
with other radio properties of the HBL class, this suggests modest Lorentz
factors in their parsec-scale radio jets. This in turn suggests some form of
Lorentz factor gradient in these jets, since they are likely to have high
Lorentz factors in their TeV-emitting regions. The study presented here
approximately doubles the number of TeV HBLs with multi-epoch parsec-scale
kinematic measurements.
| arxiv topic:astro-ph.HE |
arxiv_dataset-34151205.2499 | Three-photon electromagnetically induced transparency using Rydberg
states
physics.atom-ph
We demonstrate electromagnetically induced transparency (EIT) in a four-level
cascade system where the upper level is a Rydberg state. The observed spectral
features are sub-Doppler and can be enhanced due to the compensation of Doppler
shifts with AC Stark shifts. A theoretical description of the system is
developed which agrees well with the experimental results and an expression for
the optimum parameters is derived.
| arxiv topic:physics.atom-ph |
arxiv_dataset-34161205.2599 | On the Identifiability of the Post-Nonlinear Causal Model
stat.ML cs.LG
By taking into account the nonlinear effect of the cause, the inner noise
effect, and the measurement distortion effect in the observed variables, the
post-nonlinear (PNL) causal model has demonstrated its excellent performance in
distinguishing the cause from effect. However, its identifiability has not been
properly addressed, and how to apply it in the case of more than two variables
is also a problem. In this paper, we conduct a systematic investigation on its
identifiability in the two-variable case. We show that this model is
identifiable in most cases; by enumerating all possible situations in which the
model is not identifiable, we provide sufficient conditions for its
identifiability. Simulations are given to support the theoretical results.
Moreover, in the case of more than two variables, we show that the whole causal
structure can be found by applying the PNL causal model to each structure in
the Markov equivalent class and testing if the disturbance is independent of
the direct causes for each variable. In this way the exhaustive search over all
possible causal structures is avoided.
| arxiv topic:stat.ML cs.LG |
arxiv_dataset-34171205.2699 | Measuring Higgs Couplings from LHC Data
hep-ph
Following recent ATLAS and CMS publications we interpret the results of their
Higgs searches in terms of Standard Model operators. For a Higgs mass of 125
GeV we determine several Higgs couplings from 2011 data and extrapolate the
results towards different scenarios of LHC running. Even though our analysis is
limited by low statistics we already derive meaningful constraints on modified
Higgs sectors.
| arxiv topic:hep-ph |
arxiv_dataset-34181205.2799 | Relativistic Solution for a Class of Static Compact Charged Star in
Pseudo Spheroidal Space-Time
astro-ph.SR astro-ph.CO gr-qc
Considering Vaidya-Tikekar metric, we obtain a class of solutions of the
Einstein-Maxwell equations for a charged static fluid sphere. The physical
3-space (t=constant) here is described by pseudo-spheroidal geometry. The
relativistic solution for the theory is used to obtain models for charged
compact objects, thereafter a qualitative analysis of the physical aspects of
compact objects are studied. The dependence of some of the properties of a
superdense star on the parameters of the three geometry is explored. We note
that the spheroidicity parameter $a$, plays an important role for determining
the properties of a compact object. A non-linear equation of state is required
to describe a charged compact object with pseudo-spheroidal geometry which we
have shown for known masses of compact objects. We also note that the size of a
static compact charged star is more than that of a static compact star without
charge.
| arxiv topic:astro-ph.SR astro-ph.CO gr-qc |
arxiv_dataset-34191205.2899 | Some toy Furstenberg sets and projections of the four-corner Cantor set
math.CA
We give lower bounds for the Hausdorff dimensions of some model Furstenberg
sets.
| arxiv topic:math.CA |
arxiv_dataset-34201205.2999 | Towards a new brain science: lessons from the economic collapse
nlin.AO q-fin.GN
Economies are complex man-made systems where organisms and markets interact
according to motivations and principles not entirely understood yet. The
increasing dissatisfaction with the postulates of traditional economics i.e.
perfectly rational agents, interacting through efficient markets in the search
of equilibrium, has created new incentives for different approaches in
economics. The science of complexity may provide the platform to cross
disciplinary boundaries in seemingly disparate fields such as brain science and
economics. In this paper we take an integrative stance, fostering new insights
into the economic character of neural activity. The objective here is to
precisely delineate common topics in both neural and economic science, within a
systemic outlook grounded in empirical basis that jolts the unification across
the science of complex systems. It is argued that this mainly relies on the
study of the inverse problem in complex system with a truly Bayesian approach.
| arxiv topic:nlin.AO q-fin.GN |
arxiv_dataset-34211205.3099 | Direct and indirect searches for New Physics
hep-ph
An overview of the indirect constraints from flavour physics on
supersymmetric models is presented. We study in particular constraints from Bs
-> mu+mu- and B -> K* mu+mu-, emphasising on the new LHCb results. We show that
these rare transitions provide valuable information in the search for new
physics and are complementary to the direct searches.
| arxiv topic:hep-ph |
arxiv_dataset-34221205.3199 | Conformal blocks and cohomology in genus 0
math.AG math.QA math.RT
We give a characterization of conformal blocks in terms of the singular
cohomology of suitable smooth projective varieties, in genus 0 for classical
Lie algebras and $G_2$.
| arxiv topic:math.AG math.QA math.RT |
arxiv_dataset-34231205.3299 | Fermionic solutions of chiral Gross-Neveu and Bogoliubov-de Gennes
systems in nonlinear Schr\"odinger hierarchy
cond-mat.supr-con hep-ph hep-th nlin.SI
The chiral Gross-Neveu model or equivalently the linearized Bogoliubov-de
Gennes equation has been mapped to the nonlinear Schr\"odinger (NLS) hierarchy
in the Ablowitz-Kaup-Newell-Segur formalism by Correa, Dunne and Plyushchay. We
derive the general expression for exact fermionic solutions for all gap
functions in the arbitrary order of the NLS hierarchy. We also find that the
energy spectrum of the n-th NLS hierarchy generally has n+1 gaps. As an
illustration, we present the self-consistent two-complex-kink solution with
four real parameters and two fermion bound states. The two kinks can be placed
at any position and have phase shifts. When the two kinks are well separated,
the fermion bound states are localized around each kink in most parameter
region. When two kinks with phase shifts close to each other are placed at
distance as short as possible, the both fermion bound states have two peaks at
the two kinks, i.e., the delocalization of the bound states occurs.
| arxiv topic:cond-mat.supr-con hep-ph hep-th nlin.SI |
arxiv_dataset-34241205.3399 | Random walks in Euclidean space
math.DS math.GR math.PR
Consider a sequence of independent random isometries of Euclidean space with
a previously fixed probability law. Apply these isometries successively to the
origin and consider the sequence of random points that we obtain this way. We
prove a local limit theorem under a suitable moment condition and a necessary
non-degeneracy condition. Under stronger hypothesis, we prove a limit theorem
on a wide range of scales: between e^(-cl^(1/4)) and l^(1/2), where l is the
number of steps.
| arxiv topic:math.DS math.GR math.PR |
arxiv_dataset-34251205.3499 | Signatures of sub-GeV dark matter beams at neutrino experiments
hep-ph
We study the high-luminosity fixed-target neutrino experiments at MiniBooNE,
MINOS and T2K and analyze their sensitivity to light stable states, focusing on
MeV--GeV scale dark matter. Thermal relic dark matter scenarios in the sub-GeV
mass range require the presence of light mediators, whose coupling to the
Standard Model facilitates annihilation in the early universe and allows for
the correct thermal relic abundance. The mediators in turn provide a production
channel for dark matter at colliders or fixed targets, and as a consequence the
neutrino beams generated at fixed targets may contain an additional beam of
light dark matter. The signatures of this beam include elastic scattering off
electrons or nucleons in the (near-)detector, which closely mimics the neutral
current scattering of neutrinos. We determine the event rate at modern fixed
target facilities and the ensuing sensitivity to sub-GeV dark matter.
| arxiv topic:hep-ph |
arxiv_dataset-34261205.3599 | Expansions of monomial ideals and multigraded modules
math.AC
We introduce an exact functor defined on multigraded modules which we call
the expansion functor and study its homological properties. The expansion
functor applied to a monomial ideal amounts to substitute the variables by
monomial prime ideals and to apply this substitution to the generators of the
ideal. This operation naturally occurs in various combinatorial contexts.
| arxiv topic:math.AC |
arxiv_dataset-34271205.3699 | Discovery of the Optical/Ultraviolet/Gamma-ray Counterpart to the
Eclipsing Millisecond Pulsar J1816+4510
astro-ph.HE
The energetic, eclipsing millisecond pulsar J1816+4510 was recently
discovered in a low-frequency radio survey with the Green Bank Telescope. With
an orbital period of 8.7 hr and minimum companion mass of 0.16 Msun it appears
to belong to an increasingly important class of pulsars that are ablating their
low-mass companions. We report the discovery of the gamma-ray counterpart to
this pulsar, and present a likely optical/ultraviolet counterpart as well.
Using the radio ephemeris we detect pulsations in the unclassified gamma-ray
source 2FGL J1816.5+4511, implying an efficiency of ~25% in converting the
pulsar's spin-down luminosity into gamma-rays and adding PSR J1816+4510 to the
large number of millisecond pulsars detected by Fermi. The likely optical/UV
counterpart was identified through position coincidence (<0.1") and unusual
colors. Assuming that it is the companion, with R=18.27+/-0.03 mag and
effective temperature >15,000 K it would be among the brightest and hottest of
low-mass pulsar companions, and appears qualitatively different from other
eclipsing pulsar systems. In particular, current data suggest that it is a
factor of two larger than most white dwarfs of its mass, but a factor of four
smaller than its Roche lobe. We discuss possible reasons for its high
temperature and odd size, and suggest that it recently underwent a violent
episode of mass loss. Regardless of origin, its brightness and the relative
unimportance of irradiation make it an ideal target for a mass, and hence a
neutron star mass, determination.
| arxiv topic:astro-ph.HE |
arxiv_dataset-34281205.3799 | Effect of weak rotation on large-scale circulation cessations in
turbulent convection
physics.flu-dyn
We investigate the effect of weak rotation on the large-scale circulation
(LSC) of turbulent Rayleigh-B\'{e}nard convection, using the theory for
cessations in a low-dimensional stochastic model of the flow previously
studied. We determine the cessation frequency of the LSC as a function of
rotation, and calculate the statistics of the amplitude and azimuthal velocity
fluctuations of the LSC as a function of the rotation rate for different
Rayleigh numbers. Furthermore, we show that the tails of the reorientation
probability distribution function remain unchanged for rotating systems, while
the distribution of the LSC amplitude and correspondingly the cessation
frequency are strongly affected by rotation. Our results are in close agreement
with experimental observations.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-34291205.3899 | Recent heavy flavor results from the Tevatron
hep-ex
The CDF and D0 experiments at the Tevatron ppbar collider have pioneered and
established the role of flavor physics in hadron collisions. A broad program is
now at its full maturity. We report on three new results sensitive to physics
beyond the standard model, obtained using the whole CDF dataset: a measurement
of the difference of CP asymmetries in $K^+K^-$ and $\pi^+\pi^-$ decays of
$D^0$ mesons, new bounds on the $B^0_s$ mixing phase and on the decay width
difference of $B^0_s$ mass-eigenstates, and an update of the summer 2011 search
for $B^0_(s)$ mesons decaying into pairs of muons. Finally, the D0 confirmation
of the observation of a new hadron, the $\chi_b(3P)$ state, is briefly
mentioned.
| arxiv topic:hep-ex |
arxiv_dataset-34301205.3999 | Optimal Weights Mixed Filter for Removing Mixture of Gaussian and
Impulse Noises
cs.CV
According to the character of Gaussian, we modify the Rank-Ordered Absolute
Differences (ROAD) to Rank-Ordered Absolute Differences of mixture of Gaussian
and impulse noises (ROADG). It will be more effective to detect impulse noise
when the impulse is mixed with Gaussian noise. Combining rightly the ROADG with
Optimal Weights Filter (OWF), we obtain a new method to deal with the mixed
noise, called Optimal Weights Mixed Filter (OWMF). The simulation results show
that the method is effective to remove the mixed noise.
| arxiv topic:cs.CV |
arxiv_dataset-34311205.4099 | Magnetic ordering in double perovskites R$_2$CoMnO$_6$ (R= Y,Tb)
investigated by high resolution neutron spectroscopy
cond-mat.str-el cond-mat.mtrl-sci
We have investigated low energy nuclear spin excitations in double perovskite
compounds R$_2$CoMnO$_6$ (R = Y,Tb) by inelastic neutron scattering with a
high-resolution back-scattering spectrometer. We observed inelastic signals at
about 2.1 $\mu$eV for Y$_2$CoMnO$_6$ and also for Tb$_2$CoMnO$_6$ at T = 2 K in
both energy loss and energy gain sides. We interpret these inelastic peaks to
be due to the transitions between the hyperfine split nuclear levels of
$^{59}$Co nucleus. The inelastic peaks move towards the central elastic peak
and finally merge with it at the magnetic ordering temperature $T_C$. The
energy of the low energy excitations decreases continuously and becomes zero at
$T_C \approx 75$ K for Y$_2$CoMnO$_6$ and $T_C \approx 100$ K for
Tb$_2$CoMnO$_6$. For Tb$_2$CoMnO$_6$, which contains magnetic rare-earth ions,
additional quasielastic scattering due presumably to the fluctuations of large
Tb magnetic moments was observed. The present study reveals the magnetic
ordering of the Co sublattice. The results of this investigation along with
that obtained by us for other compounds indicate the presence of unquenched
orbital moments in some of the Co compounds.
| arxiv topic:cond-mat.str-el cond-mat.mtrl-sci |
arxiv_dataset-34321205.4199 | Oriented rotational wave-packet dynamics studies via high harmonic
generation
physics.atom-ph
We produce oriented rotational wave packets in CO and measure their
characteristics via high harmonic generation. The wavepacket is created using
an intense, femtosecond laser pulse and its second harmonic. A delayed 800 nm
pulse probes the wave packet, generating even-order high harmonics that arise
from the broken symmetry induced by the orientation dynamics. The even-order
harmonic radiation that we measure appears on a zero background, enabling us to
accurately follow the temporal evolution of the wave packet. Our measurements
reveal that, for the conditions optimum for harmonic generation, the
orientation is produced by preferential ionization which depletes the sample of
molecules of one orientation.
| arxiv topic:physics.atom-ph |
arxiv_dataset-34331205.4299 | An Oxford SWIFT Integral Field Spectroscopy study of 14 early-type
galaxies in the Coma cluster
astro-ph.CO
As a demonstration of the capabilities of the new Oxford SWIFT integral field
spectrograph, we present first observations for a set of 14 early-type galaxies
in the core of the Coma cluster. Our data consist of I- and z-band spatially
resolved spectroscopy obtained with the Oxford SWIFT spectrograph, combined
with r-band photometry from the SDSS archive for 14 early- type galaxies. We
derive spatially resolved kinematics for all objects from observations of the
calcium triplet absorption features at \sim 8500 {AA} . Using this kinematic
information we classify galaxies as either Fast Rotators or Slow Rotators. We
compare the fraction of fast and slow rotators in our sample, representing the
densest environment in the nearby Universe, to results from the ATLAS3D survey,
finding the slow rotator fraction is \sim 50 per cent larger in the core of the
Coma cluster than in the Virgo cluster or field, a 1.2 {\sigma} increase given
our selection criteria. Comparing our sample to the Virgo cluster core only
(which is 24 times less dense than the Coma core) we find no evidence of an
increase in the slow rotator fraction. Combining measurements of the effective
velocity dispersion {\sigma_e} with the photometric data we determine the
Fundamental Plane for our sample of galaxies. We find the use of the average
velocity dispersion within 1 effective radius, {\sigma_e}, reduces the
residuals by 13 per cent with respect to comparable studies using central
velocity dispersions, consistent with other recent integral field Fundamental
Plane determinations.
| arxiv topic:astro-ph.CO |
arxiv_dataset-34341205.4399 | Universal integrability objects
math-ph math.MP
We discuss the main points of the quantum group approach in the theory of
quantum integrable systems and illustrate them for the case of the quantum
group $U_q(\mathcal L(\mathfrak{sl}_2))$. We give a complete set of the
functional relations correcting inexactitudes of the previous considerations. A
special attention is given to the connection of the representations used to
construct the universal transfer operators and $Q$-operators.
| arxiv topic:math-ph math.MP |
arxiv_dataset-34351205.4499 | Reconstruction of energy-dependent Sturm-Liouville equations from two
spectra
math.SP
In this paper we study the inverse spectral problem of reconstructing
energy-dependent Sturm-Liouville equations from two spectra. We give a
reconstruction algorithm and establish existence and uniqueness of
reconstruction. Our approach essentially exploits the connection between the
spectral problems under study and those for Dirac operators of a special form.
| arxiv topic:math.SP |
arxiv_dataset-34361205.4599 | Entropy decay for interacting systems via the Bochner--Bakry--Emery
approach
math.PR math-ph math.MP
We obtain estimates on the exponential rate of decay of the relative entropy
from equilibrium for Markov processes with a non-local infinitesimal generator.
We adapt some of the ideas coming from the Bakry-Emery approach to this
setting. In particular, we obtain volume-independent lower bounds for the
Glauber dynamics of interacting point particles and for various classes of
hardcore models.
| arxiv topic:math.PR math-ph math.MP |
arxiv_dataset-34371205.4699 | Issues of Architectural Description Languages for Handling Dynamic
Reconfiguration
cs.SE
Dynamic reconfiguration is the action of modifying a software system at
runtime. Several works have been using architectural specification as the basis
for dynamic reconfiguration. Indeed ADLs (architecture description languages)
let architects describe the elements that could be reconfigured as well as the
set of constraints to which the system must conform during reconfiguration. In
this work, we investigate the ADL literature in order to illustrate how
reconfiguration is supported in four well-known ADLs: pi-ADL, ACME, C2SADL and
Dynamic Wright. From this review, we conclude that none of these ADLs: (i)
addresses the issue of consistently reconfiguring both instances and types;
(ii) takes into account the behaviour of architectural elements during
reconfiguration; and (iii) provides support for assessing reconfiguration,
e.g., verifying the transition against properties.
| arxiv topic:cs.SE |
arxiv_dataset-34381205.4799 | Borderline estimates for fully nonlinear elliptic equations
math.AP
We prove new borderline regularity results for solutions to fully nonlinear
elliptic equations together with pointwise gradient potential estimates.
| arxiv topic:math.AP |
arxiv_dataset-34391205.4899 | Controlled-NOT gate operating with single photons
quant-ph
The initial proposal for scalable optical quantum computing required single
photon sources, linear optical elements such as beamsplitters and
phaseshifters, and photon detection. Here we demonstrate a two qubit gate using
indistinguishable photons from a quantum dot in a pillar microcavity. As the
emitter, the optical circuitry, and the detectors are all semiconductor, this
is a promising approach towards creating a fully integrated device for scalable
quantum computing.
| arxiv topic:quant-ph |
arxiv_dataset-34401205.4999 | Analysis of the Heyd-Scuseria-Ernzerhof density functional parameter
space
cond-mat.mtrl-sci
The Heyd-Scuseria-Ernzerhof (HSE) density functionals are popular for their
ability to improve the accuracy of standard semilocal functionals such as
Perdew-Burke-Ernzerhof (PBE), particularly for semiconductor band gaps. They
also have a reduced computational cost compared to hybrid functionals, which
results from the restriction of Fock exchange calculations to small
inter-electron separations. These functionals are defined by an overall
fraction of Fock exchange and a length scale for exchange screening. We
systematically examine this two-parameter space to assess the performance of
hybrid screened exchange (sX) functionals and to determine a balance between
improving accuracy and reducing the screening length, which can further reduce
computational costs. Three parameter choices emerge as useful: "sX-PBE" is an
approximation to the sX-LDA screened exchange density functionals based on the
local density approximation (LDA); "HSE12" minimizes the overall error over all
tests performed; and "HSE12s" is a range-minimized functional that matches the
overall accuracy of the existing HSE06 parameterization but reduces the Fock
exchange length scale by half. Analysis of the error trends over parameter
space produces useful guidance for future improvement of density functionals.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-34411205.5099 | Optical Properties of Graphene-like Two Dimensional Silicene
cond-mat.mes-hall
We study optical properties of two dimensional silicene using density
functional theory based calculations. Our results on optical response property
calculations show that they strongly depend on direction of polarization of
light, hence the optical absorption spectra are different for light polarized
parallel and perpendicular to plane of silicence. The optical absorption
spectra of silicene possess two major peaks: (i) a sharp peak at 1.74 eV due to
transition from pi to pi* states and (ii) a broad peak in range of 4-10 eV due
to excitation of sigma states to conduction bands. We also investigate the
effect of external influences such as (a) transverse static electric field and
(b) doping of hydrogen atoms (hydrogenation) on optical properties of silicene.
Firstly, with electric field, it is observed that band gap can be opened up in
silicene at Fermi level by breaking the inversion symmetry. We see appreciable
changes in optical absorption due to band gap opening. Secondly, hydrogenation
in silicene strongly modifies the hybridization and our geometry analysis
indicates that the hybridization in silicene goes from mixture of sp^2 + sp^3
to purely sp^3. Therefore, there is no pi electron present in the system.
Consequently, the electronic structure and optical absorption spectra of
silicene get modified and it undergoes a transition from semi-metal to
semiconductor due to hydrogenation.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-34421205.5199 | Automorphism groups of Cayley graphs generated by connected
transposition sets
cs.DM math.CO
Let $S$ be a set of transpositions that generates the symmetric group $S_n$,
where $n \ge 3$. The transposition graph $T(S)$ is defined to be the graph with
vertex set $\{1,\ldots,n\}$ and with vertices $i$ and $j$ being adjacent in
$T(S)$ whenever $(i,j) \in S$. We prove that if the girth of the transposition
graph $T(S)$ is at least 5, then the automorphism group of the Cayley graph
$\Cay(S_n,S)$ is the semidirect product $R(S_n) \rtimes \Aut(S_n,S)$, where
$\Aut(S_n,S)$ is the set of automorphisms of $S_n$ that fixes $S$. This
strengthens a result of Feng on transposition graphs that are trees. We also
prove that if the transposition graph $T(S)$ is a 4-cycle, then the set of
automorphisms of the Cayley graph $\Cay(S_4,S)$ that fixes a vertex and each of
its neighbors is isomorphic to the Klein 4-group and hence is nontrivial. We
thus identify the existence of 4-cycles in the transposition graph as being an
important factor in causing a potentially larger automorphism group of the
Cayley graph.
| arxiv topic:cs.DM math.CO |
arxiv_dataset-34431205.5299 | Relativistic Linear Restoring Force
physics.class-ph
We consider two different forms for a relativistic version of a linear
restoring force. The pair comes from taking Hooke's law to be the force
appearing on the right of the relativistic expressions: dp/dt or dp/dtau .
Either formulation recovers Hooke's law in the non-relativistic limit. In
addition to these two forces, we introduce a form of retardation appropriate
for the description of a linear (in displacement) force arising from the
interaction of a pair of particles with a relativistic field. The procedure is
akin to replacing Coulomb's law in E&M with a retarded form (the first
correction in the full relativistic case). This retardation leads to the
expected oscillation, but with amplitude growth in both its relativistic and
non-relativistic incarnations.
| arxiv topic:physics.class-ph |
arxiv_dataset-34441205.5399 | Influence of correlated impurities on conductivity of graphene sheets:
Time-dependent real-space Kubo approach
cond-mat.mes-hall
Exact numerical calculations of the conductivity of graphene sheets with
random and correlated distributions of disorders have been performed using the
time-dependent real-space Kubo formalism. The disorder was modeled by the
long-range Gaussian potential describing screened charged impurities and by the
short-range potential describing neutral adatoms both in the weak and strong
scattering regime. Our central result is that correlation in the spatial
distribution for the strong short-range scatterers and for the long-range
Gaussian potential do not lead to any enhancement of the conductivity in
comparison to the uncorrelated case. Our results strongly indicate that the
temperature enhancement of the conductivity reported in the recent study (Yan
and Fuhrer, Phys. Rev. Lett. 107, 206601 (2011)) and attributed to the effect
of dopant correlations was most likely caused by other factors not related to
the correlations in the scattering potential.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-34451205.5499 | The Reactor Anomaly after Daya Bay and RENO
hep-ph astro-ph.CO
Gallium and short baseline reactor neutrino experiments indicate a
short-distance anomalous disappearance of electron antineutrinos which, if
interpreted in terms of neutrino oscillations, would lead to a sterile neutrino
mass inconsistent with standard cosmological models. This anomaly is difficult
to measure at 1 km baseline experiments because its disappearance effects are
degenerate with that of theta_13. The flux normalization independent
measurement of theta_13 at Daya Bay breaks this degeneracy, allowing an
unambiguous differentiation of 1-3 neutrino oscillations and the anomalous
disappearance at Double Chooz and RENO. The resulting anomaly is consistent
with that found at very short baselines and suggests a downward revision of
RENO's result for theta_13. A MCMC global analysis of current cosmological data
shows that a quintom cosmology is just compatible at 2 sigma with a sterile
neutrino with the right mass to reproduce the reactor anomaly and to a lesser
extent the gallium and LSND/MiniBooNE anomalies. However models in which the
sterile neutrino acquires a chameleon mass easily satisfy the cosmological
bounds and also reduce the tension between LSND and KARMEN.
| arxiv topic:hep-ph astro-ph.CO |
arxiv_dataset-34461205.5599 | Water on The Moon, III. Volatiles & Activity
astro-ph.EP
For centuries some scientists have argued that there is activity on the Moon
(or water, as recounted in Parts I & II), while others have thought the Moon is
simply a dead, inactive world. The question comes in several forms: is there a
detectable atmosphere? Does the surface of the Moon change? What causes
interior seismic activity? From a more modern viewpoint, we now know that as
much carbon monoxide as water was excavated during the LCROSS impact, as
detailed in Part I, and a comparable amount of other volatiles were found. At
one time the Moon outgassed prodigious amounts of water and hydrogen in
volcanic fire fountains, but released similar amounts of volatile sulfur (or
SO2), and presumably large amounts of carbon dioxide or monoxide, if theory is
to be believed. So water on the Moon is associated with other gases. We review
what is known (and touch on what is unknown) about outgassing of various gases
from the Moon.
| arxiv topic:astro-ph.EP |
arxiv_dataset-34471205.5699 | Minimal Binary Abelian Codes of length $p^m q^n$
cs.IT math.IT
We consider binary abelian codes of length $p^m q^n$, where $p$ and $q$ are
prime rational integers under some restrictive hypotheses. In this case, we
determine the idempotents generating minimal codes and either the respective
weights or bounds of these weights. We give examples showing that these bounds
are attained in some cases.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-34481205.5799 | On the Nonlocaity in the Goulomb Gauge External Field Problem
physics.gen-ph
The apparent nonlocality of the Coulomb gauge external field problem in
electrodynamics is illustrated with an example in which nonlocality is
especially striking. Explanation of this apparent nonlocal behaviour based on a
purely local picture is given. A gauge invariant decomposition of the
Lorentz-force into two terms with clear physical meanings is pointed out. Based
on this decomposition derivation of the Aharonov-Bohm effect in terms of field
strengths alone is given.
| arxiv topic:physics.gen-ph |
arxiv_dataset-34491205.5899 | Limit of three-point Green functions : the degenerate case
math.CV math.AG
We investigate the limits of the ideals of holomorphic functions vanishing on
three points in $\C^2$ when all three points tend to the origin, and what
happens to the associated pluricomplex Green functions. This is a continuation
of the work of Magnusson, Rashkovskii, Sigurdsson and Thomas, where those
questions were settled in a generic case.
| arxiv topic:math.CV math.AG |
arxiv_dataset-34501205.5999 | Models of AM CVn star outbursts
astro-ph.SR
Outbursting AM CVn stars exhibit outbursts similar to those observed in
different types of dwarf novae. Their light-curves combine the characteristic
features of SU UMa, ER UMa, Z Cam, and WZ Sge-type systems but also show a
variety of properties never observed in dwarf novae. The compactness of AM CVn
orbits and their unusual chemical composition make these systems valuable
testbeds for outburst models. We aim for a better understanding of the role of
helium in the accretion disc instability mechanism, testing the model for dwarf
novae outbursts in the case of AM CVn stars, and aim to explain the outburst
light-curves of these ultra-compact binaries. We calculated the properties of
the hydrogen-free AM CVn stars using our previously developed numerical code
adapted to the different chemical composition of these systems and supplemented
with formulae accounting for mass transfer rate variations, additional sources
of the disc heating, and the primary's magnetic field. We discovered how
helium-dominated discs react to the thermal-viscous instability and were able
to reproduce various features of the outburst cycles in the light-curves of AM
CVn stars. The AM CVn outbursts can be explained by the suitably adapted
dwarf-nova disc instability model but, as in the case of its application to
hydrogen-dominated cataclysmic variables, one has to resort to additional
mechanisms to account for the observed superoutbursts, dips, cycling states,
and standstills. We show that the enhanced mass-transfer rate, due presumably
to variable irradiation of the secondary, must not only be taken into account
but is a determining factor that shapes AM CVn star outbursts. The cause of the
variable secondary's irradiation has yet to be understood; the best candidate
is the precession of a tilted/warped disc.
| arxiv topic:astro-ph.SR |
arxiv_dataset-34511205.6099 | Existence and examples of quantum isometry group for a class of compact
metric spaces
math.OA math.MG math.QA
We formulate a definition of isometric action of a compact quantum group
(CQG) on a compact metric space, generalizing Banica's definition for finite
metric spaces. For metric spaces $(X,d)$ which can be isometrically embedded in
some Euclidean space, we prove the existence of a universal object in the
category of the compact quantum groups acting isometrically on $(X,d)$. In
fact, our existence theorem applies to a larger class, namely for any compact
metric space $(X,d)$ which admits a one-to-one continuous map $f : X \raro
\IR^n$ for some $n$ such that $d_0(f(x),f(y))=\phi(d(x,y))$ (where $d_0$ is the
Euclidean metric) for some homeomorphism $\phi$ of $\IR^+$. As concrete
examples, we obtain Wang's quantum permutation group $\cls_n^+$ and also the
free wreath product of $\IZ_2$ by $\cls_n^+$ as the quantum isometry groups for
certain compact connected metric spaces constructed by taking topological joins
of intervals in \cite{huang1}.
| arxiv topic:math.OA math.MG math.QA |
arxiv_dataset-34521205.6199 | Asymptotic direction of random walks in Dirichlet environment
math.PR
In this paper we generalize the result of directional transience from
[SabotTournier10]. This enables us, by means of [Simenhaus07], [ZernerMerkl01]
and [Bouchet12] to conclude that, on Z^d (for any dimension d), random walks in
i.i.d. Dirichlet environment, or equivalently oriented-edge reinforced random
walks, have almost-surely an asymptotic direction equal to the direction of the
initial drift, unless this drift is zero. In addition, we identify the exact
value or distribution of certain probabilities, answering and generalizing a
conjecture of [SaTo10].
| arxiv topic:math.PR |
arxiv_dataset-34531205.6299 | Interaction between Injection Points during Hydraulic Fracturing
cond-mat.mtrl-sci physics.flu-dyn physics.geo-ph
We present a model of the hydraulic fracturing of heterogeneous poroelastic
media. The formalism is an effective continuum model that captures the coupled
dynamics of the fluid pressure and the fractured rock matrix and models both
the tensile and shear failure of the rock. As an application of the formalism,
we study the geomechanical stress interaction between two injection points
during hydraulic fracturing (hydrofracking) and how this interaction influences
the fracturing process. For injection points that are separated by less than a
critical correlation length, we find that the fracturing process around each
point is strongly correlated with the position of the neighboring point. The
magnitude of the correlation length depends on the degree of heterogeneity of
the rock and is on the order of 30-45 m for rocks with low permeabilities. In
the strongly correlated regime, we predict a novel effective fracture-force
that attracts the fractures toward the neighboring injection point.
| arxiv topic:cond-mat.mtrl-sci physics.flu-dyn physics.geo-ph |
arxiv_dataset-34541205.6399 | Forming Teams for Teaching Programming based on Static Code Analysis
cs.SE
The use of team for teaching programming can be effective in the classroom
because it helps students to generate and acquire new knowledge in less time,
but these groups to be formed without taking into account some respects, may
cause an adverse effect on the teaching-learning process. This paper proposes a
tool for the formation of team based on the semantics of source code (SOFORG).
This semantics is based on metrics extracted from the preferences, styles and
good programming practices. All this is achieved through a static analysis of
code that each student develops. In this way, you will have a record of
students with the information extracted; it evaluates the best formation of
teams in a given course. The team's formations are based on programming styles,
skills, pair programming or with leader.
| arxiv topic:cs.SE |
arxiv_dataset-34551205.6499 | Spin Response and Neutrino Emissivity of Dense Neutron Matter
nucl-th astro-ph.HE hep-ph
We study the spin response of cold dense neutron matter in the limit of zero
momentum transfer, and show that the frequency dependence of the
long-wavelength spin response is well constrained by sum-rules and the
asymptotic behavior of the two-particle response at high frequency. The
sum-rules are calculated using Auxiliary Field Diffusion Monte Carlo technique
and the high frequency two-particle response is calculated for several
nucleon-nucleon potentials. At nuclear saturation density, the sum-rules
suggest that the strength of the spin response peaks at $\omega \simeq$ 40--60
MeV, decays rapidly for $\omega \geq $100 MeV, and has a sizable strength below
40 MeV. This strength at relatively low energy may lead to enhanced neutrino
production rates in dense neutron-rich matter at temperatures of relevance to
core-collapse supernova.
| arxiv topic:nucl-th astro-ph.HE hep-ph |
arxiv_dataset-34561205.6599 | An inverse Cartier transform via exponential in positive characteristic
math.AG
Let $k$ be a perfect field of odd characteristic $p$ and $X_0$ a smooth
connected algebraic variety over $k$ which is assumed to be $W_2(k)$-liftable.
In this short note we associate a de Rham bundle to a nilpotent Higgs bundle
over $X_0$ of exponent $n\leq p-1$ via the exponential function. Presumably,
the association is equivalent to the inverse Cartier transform of A. Ogus and
V. Vologodsky for these Higgs bundles. However this point has not been verified
in the note. Instead, we show the equivalence of the association with that of
Sheng-Xin-Zuo in the geometric case. The construction relies on the cocycle
property of the difference of different Frobenius liftings over $W_2(k)$, which
plays the key role in the proof of $E_1$-degeration of the Hodge to de Rham
spectral sequence of $X_0$ due to P. Deligne and L. Illusie.
| arxiv topic:math.AG |
arxiv_dataset-34571205.6699 | Minuet: A Scalable Distributed Multiversion B-Tree
cs.DB
Data management systems have traditionally been designed to support either
long-running analytics queries or short-lived transactions, but an increasing
number of applications need both. For example, online games, socio-mobile apps,
and e-commerce sites need to not only maintain operational state, but also
analyze that data quickly to make predictions and recommendations that improve
user experience. In this paper, we present Minuet, a distributed, main-memory
B-tree that supports both transactions and copy-on-write snapshots for in-situ
analytics. Minuet uses main-memory storage to enable low-latency transactional
operations as well as analytics queries without compromising transaction
performance. In addition to supporting read-only analytics queries on
snapshots, Minuet supports writable clones, so that users can create branching
versions of the data. This feature can be quite useful, e.g. to support complex
"what-if" analysis or to facilitate wide-area replication. Our experiments show
that Minuet outperforms a commercial main-memory database in many ways. It
scales to hundreds of cores and TBs of memory, and can process hundreds of
thousands of B-tree operations per second while executing long-running scans.
| arxiv topic:cs.DB |
arxiv_dataset-34581205.6799 | The 21cm radiation from minihalos as a probe of small primordial
non-Gaussianity
astro-ph.CO
We present a new probe of primordial non-Gaussianity via the 21cm radiation
from minihalos at high redshifts. We calculate the fluctuations in the
brightness temperature (measured against the cosmic microwave background) of
the 21cm background from minihalos containing HI at redshift \sim 6-20, and
find a significant enhancement due to small non-Gaussianity with amplitude f_NL
\leq 1. This enhancement can be attributed to the nonlinear bias which is
strongly increased in the presence of non-Gaussianity. We show that our results
are robust against changes in the assumed mass function and some physical
aspects of minihalo formation, but are nevertheless sensitive to the presence
of strong radiation sources within or around the minihalos. Our findings are
relevant for constraining and searching for small primordial non-Gaussianity
with upcoming radio telescopes such as LOFAR and SKA.
| arxiv topic:astro-ph.CO |
arxiv_dataset-34591205.6899 | Transversal electric conductivity and dielectric function in quantum
Maxwell collisional plasma
physics.plasm-ph quant-ph
Formulas for transversal conductance and dielectric permeability (dielectric
function) in quantum Maxwell collisional plasma are deduced. The kinetic
equation with collision integral in the form relaxation type is used.
| arxiv topic:physics.plasm-ph quant-ph |
arxiv_dataset-34601205.6999 | Dynamics of one-dimensional tight-binding models with arbitrary
time-dependent external homogeneous fields
quant-ph cond-mat.quant-gas
The exact propagators of two one-dimensional systems with time-dependent
external fields are presented by following the path-integral method. It is
shown that the Bloch acceleration theorem can be generalized to the
impulse-momentum theorem in quantum version. We demonstrate that an evolved
Gaussian wave packet always keeps its shape in an arbitrary time-dependent
homogeneous driven field. Moreover, that stopping and accelerating of a wave
packet can be achieved by the pulsed field in a diabatic way.
| arxiv topic:quant-ph cond-mat.quant-gas |
arxiv_dataset-34611206.0007 | Detection of isolated population III stars with the James Webb Space
Telescope
astro-ph.CO
The first population III stars are predicted to form in minihalos at a
redshift of approximately 10-30. The James Webb Space Telescope (JWST),
tentatively scheduled for launch in 2018, will probably be able to detect some
of the first galaxies, but whether it will also be able to detect the first
stars remains more doubtful. Here, we explore the prospects of detecting an
isolated population III star or a small cluster of population III stars down to
redshift 2 in either lensed or unlensed fields. Our calculations are based on
realistic stellar atmospheres and take into account the potential flux
contribution from the surrounding HII region. We find that unlensed population
III stars are beyond the reach of JWST, and that even lensed population III
stars will be extremely difficult to detect. However, the main problem with the
latter approach is not necessarily that the lensed stars are too faint, but
that their surface number densities are too low. To detect even one population
III star of 60 solar masses when pointing JWST through the galaxy cluster MACS
J0717.5+3745, the lensing cluster with the largest Einstein radius detected so
far, the cosmic star formation rate of population III stars would need to be
approximately an order of magnitude higher than predicted by the most
optimistic current models.
| arxiv topic:astro-ph.CO |
arxiv_dataset-34621206.0107 | Cooperation in Carrier Sense Based Wireless Ad Hoc Networks - Part II:
Proactive Schemes
cs.NI
This work is the second of a two-part series of papers on the effectiveness
of cooperative techniques in non-centralized carrier sense-based ad hoc
wireless networks. While Part I extensively discussed reactive cooperation,
characterized by relayed transmissions triggered by failure events at the
intended receiver, Part II investigates in depth proactive solutions, in which
the source of a packet exploits channel state information to preemptively
coordinate with relays in order to achieve the optimal overall rate to the
destination. In particular, this work shows by means of both analysis and
simulation that the performance of reactive cooperation is reduced by the
intrinsic nature of the considered medium access policy, which biases the
distribution of the available relays, locating them in unfavorable positions
for rate optimization. Moreover, the highly dynamic nature of interference that
characterizes non-infrastructured ad hoc networks is proved to hamper the
efficacy and the reliability of preemptively allocated cooperative links, as
unpredicted births and deaths of surrounding transmissions may force relays to
abort their support and/or change the maximum achievable rate at the intended
receiver. As a general conclusion, our work extensively suggests that
CSMA-based link layers are not apt to effectively support cooperative
strategies in large-scale non-centralized ad hoc networks.
| arxiv topic:cs.NI |
arxiv_dataset-34631206.0207 | Probabilistic Turing Machine and Landauer Limit
math-ph math.MP
We show the equivalence between a probabilistic Turing machine and the time
evolution of a one-dimensional Ising model, the Glauber model in one dimension,
equilibrium positions representing the results of computations of the Turing
machine. This equivalence permits to map a physical system on a computational
system providing in this way an evaluation of the entropy at the end of
computation. The result agrees with Landauer limit.
| arxiv topic:math-ph math.MP |
arxiv_dataset-34641206.0307 | Quantum Superinductor with Tunable Non-Linearity
cond-mat.supr-con
We report on the realization of a superinductor, a dissipationless element
whose microwave impedance greatly exceeds the resistance quantum. The design of
the superinductor, implemented as a ladder of nanoscale Josephson junctions,
enables tuning of the inductance and its nonlinearity by a weak magnetic field.
The Rabi decay time of the superinductor-based qubit exceeds 1 microsecond. The
high kinetic inductance and strong nonlinearity offer new types of
functionality, including the development of qubits protected from both flux and
charge noises, fault tolerant quantum computing, and high-impedance isolation
for electrical current standards based on Bloch oscillations.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-34651206.0407 | New properties of multiple harmonic sums modulo $p$ and $p$-analogues of
Leshchiner's series
math.NT math.CO
In this paper we present some new identities of hypergeometric type for
multiple harmonic sums whose indices are the sequences $(\{1\}^a,c,\{1\}^b),$
$(\{2\}^a,c,\{2\}^b)$ and prove a number of congruences for these sums modulo a
prime $p.$ The congruences obtained allow us to find nice $p$-analogues of
Leshchiner's series for zeta values and to refine a result due to M. Hoffman
and J. Zhao about the set of generators of the multiple harmonic sums of weight
7 and 9 modulo $p$. Moreover, we are also able to provide a new proof of
Zagier's formula for $\zeta^{*}(\{2\}^a,3,\{2\}^b)$ based on a finite identity
for partial sums of the zeta-star series.
| arxiv topic:math.NT math.CO |
arxiv_dataset-34661206.0507 | Observational Constraints of Modified Chaplygin Gas in Loop Quantum
Cosmology
physics.gen-ph astro-ph.CO gr-qc
We have considered the FRW universe in loop quantum cosmology (LQC) model
filled with the dark matter (perfect fluid with negligible pressure) and the
modified Chaplygin gas (MCG) type dark energy. We present the Hubble parameter
in terms of the observable parameters $\Omega_{m0}$, $\Omega_{x0}$ and $H_{0}$
with the redshift $z$ and the other parameters like $A$, $B$, $C$ and $\alpha$.
From Stern data set (12 points), we have obtained the bounds of the arbitrary
parameters by minimizing the $\chi^{2}$ test. The best-fit values of the
parameters are obtained by 66%, 90% and 99% confidence levels. Next due to
joint analysis with BAO and CMB observations, we have also obtained the bounds
of the parameters ($B,C$) by fixing some other parameters $\alpha$ and $A$.
From the best fit of distance modulus $\mu(z)$ for our theoretical MCG model in
LQC, we concluded that our model is in agreement with the union2 sample data.
| arxiv topic:physics.gen-ph astro-ph.CO gr-qc |
arxiv_dataset-34671206.0607 | Global and uniqueness properties of stationary and static spacetimes
with outer trapped surfaces
gr-qc math.DG
Global properties of maximal future Cauchy developments of stationary,
m-dimensional asymptotically flat initial data with an outer trapped boundary
are analyzed. We prove that, whenever the matter model is well posed and
satisfies the null energy condition, the future Cauchy development of the data
is a black hole spacetime. More specifically, we show that the future Killing
development of the exterior of a sufficiently large sphere in the initial data
set can be isometrically embedded in the maximal Cauchy development of the
data. In the static setting we prove, by working directly on the initial data
set, that all Killing prehorizons are embedded whenever the initial data set
has an outer trapped boundary and satisfies the null energy condition. By
combining both results we prove a uniqueness theorem for static initial data
sets with outer trapped boundary.
| arxiv topic:gr-qc math.DG |
arxiv_dataset-34681206.0707 | Recurrence of planar graph limits
math.PR math.CO
We prove that any distributional limit of finite planar graphs in which the
degree of the root has an exponential tail is almost surely recurrent. As a
corollary, we obtain that the uniform infinite planar triangulation and
quadrangulation (UIPT and UIPQ) are almost surely recurrent, resolving a
conjecture of Angel, Benjamini and Schramm.
We also settle another related problem of Benjamini and Schramm. We show that
in any bounded degree, finite planar graph the probability that the simple
random walk started at a uniform random vertex avoids its initial location for
T steps is at most C/log T.
| arxiv topic:math.PR math.CO |
arxiv_dataset-34691206.0807 | Masses and Majorana fermions in graphene
cond-mat.mes-hall
We review the classification of all the 36 possible gap-opening instabilities
in graphene, i.e., the 36 relativistic masses of the two-dimensional Dirac
Hamiltonian when the spin, valley, and superconducting channels are included.
We then show that in graphene it is possible to realize an odd number of
Majorana fermions attached to vortices in superconducting order parameters if a
proper hierarchy of mass scales is in place.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-34701206.0907 | The local Tb theorem with rough test functions
math.CA
We prove a local $Tb$ theorem under close to minimal (up to certain
`buffering') integrability assumptions, conjectured by S. Hofmann (El Escorial,
2008): Every cube is assumed to support two non-degenerate functions $b^1_Q\in
L^p$ and $b^2_Q\in L^q$ such that $1_{2Q}Tb^1_Q\in L^{q'}$ and
$1_{2Q}T^*b^2_Q\in L^{p'}$, with appropriate uniformity and scaling of the
norms. This is sufficient for the $L^2$-boundedness of the Calderon-Zygmund
operator $T$, for any $p,q\in(1,\infty)$, a result previously unknown for
simultaneously small values of $p$ and $q$. We obtain this as a corollary of a
local $Tb$ theorem for the maximal truncations $T_{\#}$ and $(T^*)_{\#}$: for
the $L^2$-boundedness of $T$, it suffices that $1_Q T_{\#}b^1_Q$ and $1_Q
(T^*)_{\#}b^2_Q$ be uniformly in $L^0$. The proof builds on the technique of
suppressed operators from the quantitative Vitushkin conjecture due to
Nazarov-Treil-Volberg.
| arxiv topic:math.CA |
arxiv_dataset-34711206.1007 | On the scaling ranges of detrended fluctuation analysis for long-memory
correlated short series of data
physics.data-an q-fin.GN
We examine the scaling regime for the detrended fluctuation analysis (DFA) -
the most popular method used to detect the presence of long memory in data and
the fractal structure of time series. First, the scaling range for DFA is
studied for uncorrelated data as a function of length $L$ of time series and
regression line coefficient $R^2$ at various confidence levels. Next, an
analysis of artificial short series with long memory is performed. In both
cases the scaling range $\lambda$ is found to change linearly -- both with $L$
and $R^2$. We show how this dependence can be generalized to a simple unified
model describing the relation $\lambda=\lambda(L, R^2, H)$ where $H$ ($1/2\leq
H \leq 1$) stands for the Hurst exponent of long range autocorrelated data. Our
findings should be useful in all applications of DFA technique, particularly
for instantaneous (local) DFA where enormous number of short time series has to
be examined at once, without possibility for preliminary check of the scaling
range of each series separately.
| arxiv topic:physics.data-an q-fin.GN |
arxiv_dataset-34721206.1107 | A new approach to the results of K\"ovari, S\'os, and Tur\'an concerning
rectangle-free subsets of the grid
math.CO
For positive integers $m$ and $n$, define $f(m,n)$ to be the smallest integer
such that any subset $A$ of the $m \times n$ integer grid with $|A| \geq
f(m,n)$ contains a rectangle; that is, there are $x\in [m]$ and $y \in [n]$ and
$d_{1},d_{2} \in \mathbb{Z}^{+}$ such that all four points $(x,y)$,
$(x+d_{1},y)$, $(x,y+d_{2})$, and $(x+d_{1},y+d_{2})$ are contained in $A$. In
\cite{kovarisosturan}, K\"ovari, S\'os, and Tur\'an showed that $\dlim_{k \to
\infty}\dfrac{f(k,k)}{k^{3/2}} = 1$. They also showed that whenever $p$ is a
prime number, $f(p^{2},p^{2}+p) = p^{2}(p+1)+1$. We recover their asymptotic
result and strengthen the second, providing cleaner proofs which exploit a
connection to projective planes, first noticed by Mendelsohn in
\cite{mendelsohn87}. We also provide an explicit lower bound for $f(k,k)$ which
holds for all $k$.
| arxiv topic:math.CO |
arxiv_dataset-34731206.1207 | Causality bounds for neutron-proton scattering
nucl-th cond-mat.quant-gas
We consider the constraints of causality and unitarity for the low-energy
interactions of protons and neutrons. We derive a general theorem that
non-vanishing partial-wave mixing cannot be reproduced with zero-range
interactions without violating causality or unitarity. We define and calculate
interaction length scales which we call the causal range and the Cauchy-Schwarz
range for all spin channels up to J = 3. For some channels we find that these
length scales are as large as 5 fm. We investigate the origin of these large
lengths and discuss their significance for the choice of momentum cutoff scales
in effective field theory and universality in many-body Fermi systems.
| arxiv topic:nucl-th cond-mat.quant-gas |
arxiv_dataset-34741206.1307 | Non-Additivity of the Entanglement of Purification (Beyond Reasonable
Doubt)
quant-ph cs.IT math.IT
We demonstrate the convexity of the difference between the regularized
entanglement of purification and the entropy, as a function of the state. This
is proved by means of a new asymptotic protocol to prepare a state from
pre-shared entanglement and by local operations only. We go on to employ this
convexity property in an investigation of the additivity of the (single-copy)
entanglement of purification: using numerical results for two-qubit Werner
states we find strong evidence that the entanglement of purification is
different from its regularization, hence that entanglement of purification is
not additive.
| arxiv topic:quant-ph cs.IT math.IT |
arxiv_dataset-34751206.1407 | Axion topological field theory of topological superconductors
cond-mat.supr-con hep-th
Topological superconductors are gapped superconductors with gapless and
topologically robust quasiparticles propagating on the boundary. In this paper,
we present a topological field theory description of three-dimensional
time-reversal invariant topological superconductors. In our theory the
topological superconductor is characterized by a topological coupling between
the electromagnetic field and the superconducting phase fluctuation, which has
the same form as the coupling of "axions" with an Abelian gauge field. As a
physical consequence of our theory, we predict the level crossing induced by
the crossing of special "chiral" vortex lines, which can be realized by
considering s-wave superconductors in proximity with the topological
superconductor. Our theory can also be generalized to the coupling with a
gravitational field.
| arxiv topic:cond-mat.supr-con hep-th |
arxiv_dataset-34761206.1507 | The Composite Particles Model (CPM), Vacuum Structure and ~ 125 GeV
Higgs Mass
hep-ph
The Composite Particles Model (CPM) is characterized by composite Higgs,
composite top quark, cancelation of the scalar leading quadratic divergences,
and a particular ground state such that top anti-top channel is neither
attractive or repulsive at tree level at the Z pole mass. The radiatively
generated scalar mass in 2D is m_H=\sqrt((6m_t^2 -M_Z^2-2M_w^2)/3(1+{\pi}/k))=
113 GeV/c^2,143 GeV/c^2,...,230 GeV/c^2 for k = 1,2,...\infty. As first
proposed by Nambu in the simplest models with dynamical mass generation and
fermion condensate in 4D, one expects the Higgs mass on the order of twice the
heaviest fermion mass. Hence, if this is applied to the CPM one could expect
scalar mass dynamically generated by top constituent quarks and composite top
quarks to be equal to 2 m_t/3 and 2m_t respectively. When Bose-Einstein
statistics for kT \cong M_W c^2 is applied to the two lowest energy states in
2D (113 GeV and 143 GeV) and 4D (115 GeV and 346 GeV), the CPM suggests
physical Higgs mass equal to m_H \cong 125 GeV/c^2 in both 2D and 4D.
| arxiv topic:hep-ph |
arxiv_dataset-34771206.1607 | Searching for High Energy Neutrino counterpart signals; The case of the
Fermi Bubbles signal and of Dark Matter annihilation in the inner Galaxy
astro-ph.HE astro-ph.GA hep-ph
The recent uncovering of the \textit{Fermi} Bubbles/haze in the
\textit{Fermi} gamma-ray data has generated theoretical work to explain such a
signal of hard $\gamma$-rays in combination with the \textit{WMAP} haze signal.
Many of these theoretical models can have distinctively different implications
with regards to the production of high energy neutrinos. We discuss the
neutrino signals from different models proposed for the explanation of the
\textit{Fermi} Bubbles/haze, more explicitly, from Dark Matter annihilation in
the galactic halo with conditions of preferential CR diffusion, from recent AGN
jet activity, from periodic diffusive shock acceleration, from stochastic 2nd
order Fermi acceleration and from long time-scale star formation in the
galactic center in combination with strong galactic winds. We find that some of
these models will be probed by the IceCube DeepCore detector. Moreover, with a
km$^3$ telescope located at the north hemisphere, we will be able to
discriminate between the hadronic, leptonic and the DM models. Additionally
using the reconstructed neutrino spectra we will probe annihilation of TeV
scale dark matter towards the galactic center.
| arxiv topic:astro-ph.HE astro-ph.GA hep-ph |
arxiv_dataset-34781206.1707 | Sample dispersion in isotachophoresis with Poiseuille counterflow
physics.flu-dyn
A particular mode of isotachophoresis (ITP) employs a pressure-driven flow
opposite to the sample electromigration direction in order to anchor a sample
zone at a specific position along a channel or capillary. We investigate this
situation using a two-dimensional finite-volume model based on the
Nernst-Planck equation. The imposed Poiseuille flow profile leads to a
significant dispersion of the sample zone. This effect is detrimental for the
resolution in analytical applications of ITP. We investigate the impact of
convective dispersion, characterized by the area-averaged width of a sample
zone, for various values of the sample P\'{e}clet-number, as well as the
relative mobilities of the sample and the adjacent electrolytes. A
one-dimensional model for the area-averaged concentrations based on a
Taylor-Aris-type effective axial diffusivity is shown to yield good agreement
with the finite-volume calculations. This justifies the use of such simple
models and opens the door for the rapid simulation of ITP protocols with
Poiseuille counterflow.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-34791206.1807 | Non-Gaussian quantum discord for Gaussian states
quant-ph
In recent years the paradigm based on entanglement as the unique measure of
quantum correlations has been challenged by the rise of new correlation
concepts, such as quantum discord, able to reveal quantum correlations that are
present in separable states. It is in general difficult to compute quantum
discord, because it involves a minimization over all possible local
measurements in a bipartition. In the realm of continuous variable (CV)
systems, a Gaussian version of quantum discord has been put forward upon
restricting to Gaussian measurements. It is natural to ask whether non-Gaussian
measurements can lead to a stronger minimization than Gaussian ones. Here we
focus on two relevant classes of two-mode Gaussian states: squeezed thermal
states (STS) and mixed thermal states (MTS), and allow for a range of
experimentally feasible non-Gaussian measurements, comparing the results with
the case of Gaussian measurements. We provide evidence that Gaussian
measurements are optimal for Gaussian states.
| arxiv topic:quant-ph |
arxiv_dataset-34801206.1907 | Fragmentation and OB Star Formation in High-Mass Molecular Hub-Filament
System
astro-ph.SR
Filamentary structures are ubiquitously seen in the interstellar medium. The
concentrated molecular mass in the filaments allows fragmentation to occur in a
shorter timescale than the timescale of the global collapse. Such hierarchical
fragmentation may further assist the dissipation of excessive angular momentum.
It is crucial to resolve the morphology and the internal velocity structures of
the molecular filaments observationally.
We perform 0".5-2".5 angular resolution interferometric observations toward
the nearly face-on OB cluster forming region G33.92+0.11. Observations of
various spectral lines as well as the millimeter dust continuum emission,
consistently trace several $\sim$1 pc scale, clumpy molecular arms. Some of the
molecular arms geometrically merge to an inner
3.0$^{{\scriptsize{+2.8}}}_{{-\scriptsize{1.4}}}\cdot10^{3}$\,$M_{\odot}$, 0.6
pc scale central molecular clump, and may directly channel the molecular gas to
the warm ($\sim$50 K) molecular gas immediately surrounding the centrally
embedded OB stars. The NH$_{3}$ spectra suggest a medium turbulence line width
of FWHM$\lesssim$2\,km\,s$^{-1}$ in the central molecular clump, implying a
$\gtrsim$10 times larger molecular mass than the virial mass. Feedbacks from
shocks and the centrally embedded OB stars and localized (proto)stellar
clusters, likely play a key role in the heating of molecular gas and could lead
to the observed chemical stratification. Although (proto)stellar feedbacks are
already present, G33.92+0.11 chemically appears to be at an early evolutionary
stage given by the low abundance limit of SO$_{2}$ observed in this region.
| arxiv topic:astro-ph.SR |
arxiv_dataset-34811206.2007 | Time-Dependent Thermopower Effect in an Interacting Quantum Dot
cond-mat.mes-hall
The time-dependent thermopower is analyzed through an interacting quantum dot
coupled to a time-dependent gate voltage and under the influence of an external
magnetic field using the Keldysh nonequilibrium Green's function formalism.
Formal expressions of the electrical and thermal conductances, thermopower, and
thermoelectrical figure of merit are obtained. The influence of the magnetic
field on the displacement current and the heat current is studied. Results show
that although applying time-dependent gate voltage results in the enhancement
of the Seebeck coefficient, the electron-electron interaction gives rise to a
significant reduction in the thermopower. The reason for why applying time
dependent gate voltage results in the enhancement of the thermopower is also
analyzed.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-34821206.2107 | Measurements and Information in Spin Foam Models
gr-qc math-ph math.MP
We present a problem relating measurements and information theory in spin
foam models. In the three dimensional case of quantum gravity we can compute
probabilities of spin network graphs and study the behaviour of the Shannon
entropy associated to the corresponding information. We present a general
definition, compute the Shannon entropy of some examples, and find some
interesting inequalities.
| arxiv topic:gr-qc math-ph math.MP |
arxiv_dataset-34831206.2207 | Octet baryon electromagnetic form factors in nuclear medium
hep-ph hep-ex hep-lat nucl-ex nucl-th
We study the octet baryon electromagnetic form factors in nuclear matter
using the covariant spectator quark model extended to the nuclear matter
regime. The parameters of the model in vacuum are fixed by the study of the
octet baryon electromagnetic form factors. In nuclear matter the changes in
hadron properties are calculated by including the relevant hadron masses and
the modification of the pion-baryon coupling constants calculated in the
quark-meson coupling model. In nuclear matter the magnetic form factors of the
octet baryons are enhanced in the low $Q^2$ region, while the electric form
factors show a more rapid variation with $Q^2$. The results are compared with
the modification of the bound proton electromagnetic form factors observed at
Jefferson Lab. In addition, the corresponding changes for the bound neutron are
predicted.
| arxiv topic:hep-ph hep-ex hep-lat nucl-ex nucl-th |
arxiv_dataset-34841206.2307 | A PAXOS based State Machine Replication System for Anomaly Detection
cs.CR
A number of systems in recent times suffer from attacks like DDoS and Ping of
Death. Such attacks result in loss of critical system resources and CPU cycles,
as these compromised systems behave in an abnormal manner. The effect of such
abnormalities is worse in case of compromised systems handling financial
transaction, since it leads to severe monetary losses. In this paper we propose
a system that uses the Replicated State Machine approach to detect abnormality
in system usage. The suggested system is based on PAXOS algorithm, an algorithm
for solving the consensus problem in a network of unreliable processors.
| arxiv topic:cs.CR |
arxiv_dataset-34851206.2407 | Fermionic Superfluid from a Bilayer Band Insulator in an Optical Lattice
cond-mat.quant-gas cond-mat.supr-con
We propose a model to realize a fermionic superfluid state in an optical
lattice circumventing the cooling problem. Our proposal exploits the idea of
tuning the interaction in a characteristically low entropy state, a
band-insulator in an optical bilayer system, to obtain a superfluid. By
performing a detailed analysis of the model including fluctuations and
augmented by a variational quantum Monte Carlo calculations of the ground
state, we show that the superfluid state obtained has high transition
temperature of the order of the hopping energy. Our system is designed to
suppress other competing orders such as a charge density wave. We suggest a
laboratory realization of this model via an orthogonally shaken optical lattice
bilayer.
| arxiv topic:cond-mat.quant-gas cond-mat.supr-con |
arxiv_dataset-34861206.2507 | Complementarity and phases in SU(3)
math-ph math.MP quant-ph
Phase operators and phase states are introduced for irreducible
representations of the Lie algebra su(3) using a polar decomposition of ladder
operators. In contradistinction with su(2), it is found that the su(3) polar
decomposition does not uniquely determine a Hermitian phase operator. We
describe two possible ways of proceeding: one based in imposing SU(2)
invariance and the other based on the idea of complementarity. The
generalization of these results to SU(n) is sketched.
| arxiv topic:math-ph math.MP quant-ph |
arxiv_dataset-34871206.2607 | Selective decay by Casimir dissipation in fluids
nlin.CD math-ph math.MP physics.flu-dyn
The problem of parameterizing the interactions of larger scales and smaller
scales in fluid flows is addressed by considering a property of two-dimensional
incompressible turbulence. The property we consider is selective decay, in
which a Casimir of the ideal formulation (enstrophy in 2D flows, helicity in 3D
flows) decays in time, while the energy stays essentially constant. This paper
introduces a mechanism that produces selective decay by enforcing Casimir
dissipation in fluid dynamics. This mechanism turns out to be related in
certain cases to the numerical method of anticipated vorticity discussed in
\cite{SaBa1981,SaBa1985}. Several examples are given and a general theory of
selective decay is developed that uses the Lie-Poisson structure of the ideal
theory. A scale-selection operator allows the resulting modifications of the
fluid motion equations to be interpreted in several examples as parameterizing
the nonlinear, dynamical interactions between disparate scales. The type of
modified fluid equation systems derived here may be useful in modelling
turbulent geophysical flows where it is computationally prohibitive to rely on
the slower, indirect effects of a realistic viscosity, such as in large-scale,
coherent, oceanic flows interacting with much smaller eddies.
| arxiv topic:nlin.CD math-ph math.MP physics.flu-dyn |
arxiv_dataset-34881206.2707 | The equilibrium states of open quantum systems in the strong coupling
regime
cond-mat.stat-mech quant-ph
In this work we investigate the late-time stationary states of open quantum
systems coupled to a thermal reservoir in the strong coupling regime. In
general such systems do not necessarily relax to a Boltzmann distribution if
the coupling to the thermal reservoir is non-vanishing or equivalently if the
relaxation timescales are finite. Using a variety of non-equilibrium formalisms
valid for non-Markovian processes, we show that starting from a product state
of the closed system = system + environment, with the environment in its
thermal state, the open system which results from coarse graining the
environment will evolve towards an equilibrium state at late-times. This state
can be expressed as the reduced state of the closed system thermal state at the
temperature of the environment. For a linear (harmonic) system and environment,
which is exactly solvable, we are able to show in a rigorous way that all
multi-time correlations of the open system evolve towards those of the closed
system thermal state. Multi-time correlations are especially relevant in the
non-Markovian regime, since they cannot be generated by the dynamics of the
single-time correlations. For more general systems, which cannot be exactly
solved, we are able to provide a general proof that all single-time
correlations of the open system evolve to those of the closed system thermal
state, to first order in the relaxation rates. For the special case of a
zero-temperature reservoir, we are able to explicitly construct the reduced
closed system thermal state in terms of the environmental correlations.
| arxiv topic:cond-mat.stat-mech quant-ph |
arxiv_dataset-34891206.2807 | An efficient hierarchical graph based image segmentation
cs.CV
Hierarchical image segmentation provides region-oriented scalespace, i.e., a
set of image segmentations at different detail levels in which the
segmentations at finer levels are nested with respect to those at coarser
levels. Most image segmentation algorithms, such as region merging algorithms,
rely on a criterion for merging that does not lead to a hierarchy, and for
which the tuning of the parameters can be difficult. In this work, we propose a
hierarchical graph based image segmentation relying on a criterion popularized
by Felzenzwalb and Huttenlocher. We illustrate with both real and synthetic
images, showing efficiency, ease of use, and robustness of our method.
| arxiv topic:cs.CV |
arxiv_dataset-34901206.2907 | Particular Integrability and (Quasi)-exact-solvability
math-ph math.MP nlin.SI physics.class-ph quant-ph
A notion of a particular integrability is introduced when two operators
commute on a subspace of the space where they act. Particular integrals for
one-dimensional (quasi)-exactly-solvable Schroedinger operators and
Calogero-Sutherland Hamiltonians for all roots are found. In the classical case
some special trajectories for which the corresponding particular constants of
motion appear are indicated.
| arxiv topic:math-ph math.MP nlin.SI physics.class-ph quant-ph |
arxiv_dataset-34911206.3007 | Maximal antichains of minimum size
math.CO
Let $n\geqslant 4$ be a natural number, and let $K$ be a set $K\subseteq
[n]:={1,2,...,n}$. We study the problem to find the smallest possible size of a
maximal family $\mathcal{A}$ of subsets of $[n]$ such that $\mathcal{A}$
contains only sets whose size is in $K$, and $A\not\subseteq B$ for all
${A,B}\subseteq\mathcal{A}$, i.e. $\mathcal{A}$ is an antichain. We present a
general construction of such antichains for sets $K$ containing 2, but not 1.
If $3\in K$ our construction asymptotically yields the smallest possible size
of such a family, up to an $o(n^2)$ error. We conjecture our construction to be
asymptotically optimal also for $3\not\in K$, and we prove a weaker bound for
the case $K={2,4}$. Our asymptotic results are straightforward applications of
the graph removal lemma to an equivalent reformulation of the problem in
extremal graph theory which is interesting in its own right.
| arxiv topic:math.CO |
arxiv_dataset-34921206.3107 | Testing Einstein's time dilation under acceleration using M\"ossbauer
spectroscopy
physics.class-ph
The Einstein time dilation formula was tested in several experiments. Many
trials have been made to measure the transverse second order Doppler shift by
M\"{o}ssbauer spectroscopy using a rotating absorber, to test the validity of
this formula. Such experiments are also able to test if the time dilation
depends only on the velocity of the absorber, as assumed by Einstein's clock
hypothesis, or the present centripetal acceleration contributes to the time
dilation. We show here that the fact that the experiment requires $\gamma$-ray
emission and detection slits of finite size, the absorption line is broadened;
by geometric longitudinal first order Doppler shifts immensely. Moreover, the
absorption line is non-Lorenzian. We obtain an explicit expression for the
absorption line for any angular velocity of the absorber.
The analysis of the experimental results, in all previous experiments which
did not observe the full absorption line itself, were wrong and the conclusions
doubtful. The only proper experiment was done by K\"{u}ndig (Phys. Rev. 129
(1963) 2371), who observed the broadening, but associated it to random
vibrations of the absorber. We establish necessary conditions for the
successful measurement of a transverse second order Doppler shift by
M\"{o}ssbauer spectroscopy. We indicate how the results of such an experiment
can be used to verify the existence of a Doppler shift due to acceleration and
to test the validity of Einstein's clock hypothesis.
| arxiv topic:physics.class-ph |
arxiv_dataset-34931206.3207 | Non-Gaussian statistics and extreme waves in a nonlinear optical cavity
physics.optics physics.flu-dyn
A unidirectional optical oscillator is built by using a liquid crystal
light-valve that couples a pump beam with the modes of a nearly spherical
cavity. For sufficiently high pump intensity, the cavity field presents a
complex spatio-temporal dynamics, accompanied by the emission of extreme waves
and large deviations from the Gaussian statistics. We identify a mechanism of
spatial symmetry breaking, due to a hypercycle-type amplification through the
nonlocal coupling of the cavity field.
| arxiv topic:physics.optics physics.flu-dyn |
arxiv_dataset-34941206.3307 | Planets Around Low-Mass Stars (PALMS). II. A Low-Mass Companion to the
Young M Dwarf GJ 3629 Separated By 0.2"
astro-ph.EP
We present the discovery of a 0.2" companion to the young M dwarf GJ 3629 as
part of our high contrast adaptive optics imaging search for giant planets
around low-mass stars with the Keck-II and Subaru telescopes. Two epochs of
imaging confirm the pair is co-moving and reveal signs of orbital motion. The
primary exhibits saturated X-ray emission, which together with its UV
photometry from GALEX point to an age younger than ~300 Myr. At these ages the
companion lies below the hydrogen burning limit with a model-dependent mass of
46 +/- 16 Mjup based on the system's photometric distance of 22 +/- 3 pc.
Resolved YJHK photometry of the pair indicates a spectral type of M7 +/- 2 for
GJ 3629 B. With a projected separation of 4.4 +/- 0.6 AU and an estimated
orbital period of 21 +/- 5 yr, GJ 3629 AB is likely to yield a dynamical mass
in the next several years, making it one of only a handful of brown dwarfs to
have a measured mass and an age constrained from the stellar primary.
| arxiv topic:astro-ph.EP |
arxiv_dataset-34951206.3407 | BCS-BEC crossover in nuclear matter with the relativistic
Hartree-Bogoliubov theory
nucl-th cond-mat.quant-gas
Based on the relativistic Hartree-Bogoliubov theory, the influence of the
pairing interaction strength on the di-neutron correlations and the crossover
from superfluidity of neutron Cooper pairs in the $^{1}S_{0}$ channel to
Bose-Einstein condensation of di-neutron pairs is systematically investigated
in the nuclear matter. The bare nucleon-nucleon interaction Bonn-B is taken in
the particle-particle channel with an effective factor to simulate the medium
effects and take into account the possible ambiguity of pairing force, and the
effective interaction PK1 is used in the particle-hole channel. If the
effective factor is larger than 1.10, a di-neutron BEC state appears in the
low-density limit, and if it is smaller than 0.85, the neutron Cooper pairs are
found totally in the weak coupling BCS region. The reference values of several
characteristic quantities which characterize the BCS-BEC crossover are obtained
respectively from the dimensionless parameter $1/(k_{\rm Fn}a)$ with $a$ the
scattering length and $k_{\rm{Fn}}$ the neutron Fermi momentum, the
zero-momentum transfer density correlation function D(0) and the effective
chemical potential $\nu_{\rm n}$.
| arxiv topic:nucl-th cond-mat.quant-gas |
arxiv_dataset-34961206.3507 | Waves and instability in a one-dimensional microfluidic array
physics.flu-dyn
Motion in a one-dimensional (1D) microfluidic array is simulated. Water
droplets, dragged by flowing oil, are arranged in a single row, and due to
their hydrodynamic interactions spacing between these droplets oscillates with
a wave-like motion that is longitudinal or transverse. The simulation yields
wave spectra that agree well with experiment. The wave-like motion has an
instability which is confirmed to arise from nonlinearities in the interaction
potential. The instability's growth is spatially localized. By selecting an
appropriate correlation function, the interaction between the longitudinal and
transverse waves is described.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-34971206.3607 | Proposed search for T-odd, P-even interactions in spectra of chaotic
atoms
physics.atom-ph hep-ph
Violation of fundamental symmetries in atoms is the subject of intense
experimental and theoretical interest. P-odd, T-even transitions have been
observed and are in excellent agreement with electroweak theory. Searches for
permanent electric dipole moments have placed bounds on T-odd, P-odd
interactions, constraining proposed extensions to the Standard Model of
elementary particles. Here we propose a new search for T-odd, P-even (TOPE)
interactions in atoms. We consider open-shell atoms, such as the rare-earth
atoms, which have dense, chaotic excitation spectra with strong level
repulsion. The strength of the level repulsion depends on the underlying
symmetries of the atomic Hamiltonian. TOPE interactions lead to enhanced level
repulsion. We demonstrate how a statistical analysis of many chaotic spectra
can determine the strength of level repulsion; in particular, the variance of
the number of levels in an energy range has been shown to be a useful measure.
We estimate that, using frequency comb spectroscopy, a sufficient number of
chaotic levels could be measured to match or exceed the current experimental
bounds on TOPE interactions.
| arxiv topic:physics.atom-ph hep-ph |
arxiv_dataset-34981206.3707 | Symplectic geometry of quantum noise
math.SG math-ph math.MP quant-ph
We discuss a quantum counterpart, in the sense of the Berezin-Toeplitz
quantization, of certain constraints on Poisson brackets coming from "hard"
symplectic geometry. It turns out that they can be interpreted in terms of the
quantum noise of observables and their joint measurements in operational
quantum mechanics. Our findings include various geometric mechanisms of quantum
noise production and a noise-localization uncertainty relation. The methods
involve Floer theory and Poisson bracket invariants originated in function
theory on symplectic manifolds.
| arxiv topic:math.SG math-ph math.MP quant-ph |
arxiv_dataset-34991206.3807 | Scalar Material Reference Systems and Loop Quantum Gravity
gr-qc hep-th
In the past, the possibility to employ (scalar) material reference systems in
order to describe classical and quantum gravity directly in terms of gauge
invariant (Dirac) observables has been emphasised frequently. This idea has
been picked up more recently in Loop Quantum Gravity (LQG) with the aim to
perform a reduced phase space quantisation of the theory thus possibly avoiding
problems with the (Dirac) operator constraint quantisation method for
constrained system. In this work, we review the models that have been studied
on the classical and/or the quantum level and parametrise the space of theories
so far considered. We then describe the quantum theory of a model that, to the
best of our knowledge, so far has only been considered classically. This model
could arguably called the optimal one in this class of models considered as it
displays the simplest possible true Hamiltonian while at the same time reducing
all constraints of General Relativity.
| arxiv topic:gr-qc hep-th |
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