id stringlengths 16 29 | text stringlengths 86 3.49k | source stringlengths 14 112 |
|---|---|---|
arxiv_dataset-33001203.4641 | Transversally Lipschitz Harmonic Functions are Lipschitz
math.AP math.CA
Let \Omega\subset\mathbb{R}^n be a bounded domain with C^\infty boundary. We
show that a harmonic function in \Omega that is Lipschitz along a family of
curves transversal to b\Omega is Lipschitz in \Omega. The space of Lipschitz
functions we consider is defined using the notion of a majorant which is a
certain generalization of the power functions t^\alpha, 0<\alpha<1.
| arxiv topic:math.AP math.CA |
arxiv_dataset-33011203.4741 | Magneto-thermal properties of the Heisenberg-Ising orthogonal-dimer
chain with triangular XXZ-clusters
cond-mat.str-el cond-mat.stat-mech
We study a spin-1/2 model with triangular XXZ-clusters on the
orthogonal-dimer chain in the presence of an external magnetic field. First, we
discuss the case where the triangular clusters are coupled via intermediate
"classical" Ising spins. Diagonalization of the triangular XXZ-clusters yields
the exact ground states; finite-temperature properties are computed exactly by
an additional transfer-matrix step. A detailed analysis reveals a large variety
of ground states at magnetization M equal to fractions 0, 1/4, and 1/2 of the
saturation magnetization M=1. Some of these ground states break translational
symmetry spontaneously and give rise to doubling of the unit cell. In a second
part we present complementary numerical data for the spin-1/2 Heisenberg model
on the orthogonal-dimer chain. We analyze several examples of T=0 magnetization
curves, entropy as a function of temperature T and magnetic field, and the
associated magnetic cooling rate. Comparison of the two models shows that in
certain situations the simplified exactly solvable model yields a qualitatively
or sometimes even quantitatively accurate description of the more challenging
quantum model, including a case which may be relevant to experimental
observations of an enhanced magnetocaloric effect in the two-dimensional
compound SrCu2(BO3)2.
| arxiv topic:cond-mat.str-el cond-mat.stat-mech |
arxiv_dataset-33021203.4841 | Achieving Congestion Diversity in Multi-hop Wireless Mesh Networks
cs.NI
This paper reports on the first systematic study of congestion-aware routing
algorithms for wireless mesh networks to achieve an improved end-end delay
performance. In particular, we compare 802.11 compatible implementations of a
set of congestion-aware routing protocols against our implementation of state
of the art shortest path routing protocol (SRCR). We implement congestion-aware
routing algorithms Backpressure (BP), Enhanced-Backpressure (E-BP) adapted from
[1], [2] suitably adjusted for 802.11 implementation. We then propose and
implement Congestion Diversity Protocol (CDP) adapted from [3] recognizing the
limitations of BP and E-BP for 802.11-based wireless networks. SRCR solely
utilizes link qualities, while BP relies on queue differential to route
packets. CDP and E-BP rely on distance metrics which take into account queue
backlogs and link qualities in the network. E-BP computes its metric by summing
the ETX and queue differential, while CDP determines its metric by calculating
the least draining time to the destination. Our small testbed consisting of
twelve 802.11g nodes enables us to empirically compare the performance of
congestion-aware routing protocols (BP, E-BP and CDP) against benchmark SRCR.
For medium to high load UDP traffic, we observe that CDP exhibits significant
improvement with respect to both end-end delay and throughput over other
protocols with no loss of performance for TCP traffic. Backpressure-based
routing algorithms (BP and E-BP) show poorer performance for UDP and TCP
traffic. Finally, we carefully study the effects of the modular approach to
congestion-aware routing design in which the MAC layer is left intact
| arxiv topic:cs.NI |
arxiv_dataset-33031203.4941 | Out-of-equilibrium generalized fluctuation-dissipation relations
cond-mat.stat-mech cond-mat.soft
We discuss fluctuation-dissipation relations valid under general conditions
even out of equilibrium. The response function is expressed in terms of
unperperturbed correlation functions, where contributions peculiar to
non-equilibrium can appear. Such extra terms take into account the interaction
among the relevant degrees of freedom in the system. We illustrate the general
formalism with two examples: driven granular systems and anomalous diffusion on
comb structures.
| arxiv topic:cond-mat.stat-mech cond-mat.soft |
arxiv_dataset-33041203.5041 | Universal Quantum Computing with Spin and Valley
cond-mat.mes-hall quant-ph
We investigate a two-electron double quantum dot with both spin and valley
degrees of freedom as they occur in graphene, carbon nanotubes, or silicon, and
regard the 16-dimensional space with one electron per dot as a four-qubit logic
space. In the spin-only case, it is well known that the exchange coupling
between the dots combined with arbitrary single-qubit operations is sufficient
for universal quantum computation. The presence of the valley degeneracy in the
electronic band structure alters the form of the exchange coupling and in
general leads to spin-valley entanglement. Here, we show that universal quantum
computation can still be performed by exchange interaction and single-qubit
gates in the presence of the additional (valley) degree of freedom. We present
an explicit pulse sequence for a spin-only controlled-NOT consisting of the
generalized exchange coupling and single-electron spin and valley rotations. We
also propose state preparations and projective measurements with the use of
adiabatic transitions between states with (1,1) and (0,2) charge distributions
similar to the spin-only case, but with the additional requirement of
controlling the spin and the valley Zeeman energies by an external magnetic
field. Finally, we demonstrate a universal two-qubit gate between a spin and a
valley qubit, allowing universal gate operations on the combined spin and
valley quantum register.
| arxiv topic:cond-mat.mes-hall quant-ph |
arxiv_dataset-33051203.5141 | Longitudinal Rescaling of Quantum Chromodynamics
hep-th hep-lat hep-ph
We examine the effect of quantum longitudinal rescaling of coordinates, on
the action of quantum chromodynamics (with quarks) to one loop. We use an
aspherical Wilsonian integration (previously applied to the pure Yang-Mills
theory and to quantum electrodynamics). Quantum fluctuations produce anomalous
powers of the rescaling parameter in the coefficients of the rescaled action.
Our results are valid for small rescalings only, because perturbation theory
breaks down for large rescalings.
| arxiv topic:hep-th hep-lat hep-ph |
arxiv_dataset-33061203.5241 | Interacting tachyon Fermi gas
hep-ph
We consider a system of many fermionic tachyons coupled to a scalar,
pseudoscalar, vector and pseudovector fields. The scalar and pseudoscalar
fields are responsible for the effective mass, while the pseudovector field is
similar to ordinary electromagnetic field. The action of vector field
$\omega_\mu$ results in tachyonic dispersion relation
$\varepsilon_p=\sqrt{p^2+g^2\omega_0^2-hpg\omega_0-g\vec \sigma \cdot \nabla
\omega_0-m^2} -g\vec \sigma \cdot \vec \omega$ that depends on helicity $h$ and
spin $\vec \sigma$. We apply the mean field approximation and find that there
appears a vector condensate with finite average $<\omega_0>$ depending on the
tachyon density. The pressure and energy density of a many-tachyon system
include the mean-field energy $<\varepsilon_p>
=\sqrt{p^2+hpng^2/M^2+n^2g^4/M^4-m^2}$ which is real when the particle number
density exceeds definite threshold which is $n>mM^2/g^2$ for right-handed and
$n>\frac 2{\sqrt{3}}mM^2/g^2$ for left-handed tachyons, while all tachyons are
subluminal at high density. There is visible difference in the properties of
right-handed and left-handed tachyons. Interaction via the vector field
$\omega_0$ may lead to stabilization of tachyon matter if its density is large
enough.
| arxiv topic:hep-ph |
arxiv_dataset-33071203.5341 | Strong QCD and Dyson-Schwinger Equations
nucl-th hep-lat hep-ph nucl-ex
The real-world properties of quantum chromodynamics (QCD) - the
strongly-interacting piece of the Standard Model - are dominated by two
emergent phenomena: confinement; namely, the theory's elementary
degrees-of-freedom - quarks and gluons - have never been detected in isolation;
and dynamical chiral symmetry breaking (DCSB), which is a remarkably effective
mass generating mechanism, responsible for the mass of more than 98% of visible
matter in the Universe. These phenomena are not apparent in the formulae that
define QCD, yet they play a principal role in determining Nature's observable
characteristics. Much remains to be learnt before confinement can properly be
understood. On the other hand,the last decade has seen important progress in
the use of relativistic quantum field theory, so that we can now explain the
origin of DCSB and are beginning to demonstrate its far-reaching consequences.
Dyson-Schwinger equations have played a critical role in these advances. These
lecture notes provide an introduction to Dyson-Schwinger equations (DSEs), QCD
and hadron physics, and illustrate the use of DSEs to predict phenomena that
are truly observable.
| arxiv topic:nucl-th hep-lat hep-ph nucl-ex |
arxiv_dataset-33081203.5441 | K-shell photoionization of ground-state Li-like carbon ions [C$^{3+}$]:
experiment, theory and comparison with time-reversed photorecombination
astro-ph.EP physics.atom-ph
Absolute cross sections for the K-shell photoionization of ground-state
Li-like carbon [C$^{3+}$(1s$^2$2s $^2$S)] ions were measured by employing the
ion-photon merged-beams technique at the Advanced Light Source. The energy
ranges 299.8--300.15 eV, 303.29--303.58 eV and 335.61--337.57 eV of the
[1s(2s2p)$^3$P]$^2$P, [1s(2s2p)$^1$P]$^2$P and [(1s2s)$^3$S 3p]$^2$P
resonances, respectively, were investigated using resolving powers of up to
6000. The autoionization linewidth of the [1s(2s2p)$^1$P]$^2$P resonance was
measured to be $27 \pm 5$ meV and compares favourably with a theoretical result
of 26 meV obtained from the intermediate coupling R-Matrix method. The present
photoionization cross section results are compared with the outcome from
photorecombination measurements by employing the principle of detailed balance.
| arxiv topic:astro-ph.EP physics.atom-ph |
arxiv_dataset-33091203.5541 | Unwinding of a one-dimensional topological superconductor
cond-mat.str-el
We show that a topological superconductor made of four chains of
superconducting spinless fermions characterized by four Majorana edge states
can adiabatically be deformed into a trivial band insulator. To unwind this
time-reversal invariant topological superconductor, interactions to spinful
fermions are switched on along an adiabatic path. Thereby, we couple modes
which belong to two different representations of the time-reversal symmetry
operator T with T^2 = 1 and T^2 = -1, respectively. This observation can be
understood by investigating how the relevant symmetries act on the entanglement
spectrum giving rise to four instead of eight different topological phases with
Majorana edge modes. We also show that a simple level crossing of doubly and
singly degenerate states occurs in the entanglement spectrum upon deforming the
quantum state.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-33101203.5641 | Exact Sequences for the Homology of the Matching Complex
math.CO
Building on work by Bouc and by Shareshian and Wachs, we provide a toolbox of
long exact sequences for the reduced simplicial homology of the matching
complex $M_n$, which is the simplicial complex of matchings in the complete
graph $K_n$. Combining these sequences in different ways, we prove several
results about the 3-torsion part of the homology of $M_n$. First, we
demonstrate that there is nonvanishing 3-torsion in $H_d(M_n;Z)$ whenever
$\nu_n \le d \le (n-6}/2$, where $\nu_n= \lceil (n-4)/3 \rceil$. By results due
to Bouc and to Shareshian and Wachs, $H_{\nu_n}(M_n;Z)$ is a nontrivial
elementary 3-group for almost all $n$ and the bottom nonvanishing homology
group of $M_n$ for all $n \neq 2$. Second, we prove that $H_d(M_n;Z)$ is a
nontrivial 3-group whenever $\nu_n \le d \le (2n-9)/5$. Third, for each $k \ge
0$, we show that there is a polynomial $f_k(r)$ of degree 3k such that the
dimension of $H_{k-1+r}(M_{2k+1+3r};Z_3)$, viewed as a vector space over $Z_3$,
is at most $f_k(r)$ for all $r \ge k+2$.
| arxiv topic:math.CO |
arxiv_dataset-33111203.5741 | Khovanov homology of a unicolored B-adequate link has a tail
math.GT
C. Armond, S. Garoufalidis and T.Le have shown that a unicolored Jones
polynomial of a B-adequate link has a stable tail at large colors. We
categorify this tail by showing that Khovanov homology of a unicolored link
also has a stable tail, whose graded Euler characteristic coincides with the
tail of the Jones polynomial.
| arxiv topic:math.GT |
arxiv_dataset-33121203.5841 | The bosonic Fock representation and a generalized Shale theorem
math.FA math-ph math.MP
We detail a new approach to the bosonic Fock representation of a complex
Hilbert space V: our account places the bosonic Fock space S[V] between the
symmetric algebra SV and its full antidual SV'; in addition to providing a
context in which arbitrary (not necessarily restricted) real symplectic
automorphisms of V are implemented, it offers simplified proofs of many
standard results of the theory.
| arxiv topic:math.FA math-ph math.MP |
arxiv_dataset-33131203.5941 | Circular law for random discrete matrices of given row sum
math.CO math.PR
Let $M_n$ be a random matrix of size $n\times n$ and let
$\lambda_1,...,\lambda_n$ be the eigenvalues of $M_n$. The empirical spectral
distribution $\mu_{M_n}$ of $M_n$ is defined as $$\mu_{M_n}(s,t)=\frac{1}{n}#
\{k\le n, \Re(\lambda_k)\le s; \Im(\lambda_k)\le t\}.$$
The circular law theorem in random matrix theory asserts that if the entries
of $M_n$ are i.i.d. copies of a random variable with mean zero and variance
$\sigma^2$, then the empirical spectral distribution of the normalized matrix
$\frac{1}{\sigma\sqrt{n}}M_n$ of $M_n$ converges almost surely to the uniform
distribution $\mu_\cir$ over the unit disk as $n$ tends to infinity.
In this paper we show that the empirical spectral distribution of the
normalized matrix of $M_n$, a random matrix whose rows are independent random
$(-1,1)$ vectors of given row-sum $s$ with some fixed integer $s$ satisfying
$|s|\le (1-o(1))n$, also obeys the circular law. The key ingredient is a new
polynomial estimate on the least singular value of $M_n$.
| arxiv topic:math.CO math.PR |
arxiv_dataset-33141203.6041 | S and D-wave phase shifts in isospin-2 pi pi scattering from lattice QCD
hep-ph hep-lat
The isospin-2 pi pi system provides a useful testing ground for determining
elastic hadron scattering parameters from finite-volume spectra obtained using
lattice QCD computations. A reliable determination of the excited state
spectrum of two pions in a cubic box follows from variational analysis of
correlator matrices constructed using a large basis of operators. A general
operator construction is presented which respects the symmetries of a
multi-hadron system in flight. This is applied to the case of pi pi and allows
for the determination of the scattering phase-shifts at a large number of
kinematic points, in both S-wave and D-wave, within the elastic region. The
technique is demonstrated with a calculation at a pion mass of 396 MeV, where
the elastic scattering is found to be well described by a scattering length
parameterisation.
| arxiv topic:hep-ph hep-lat |
arxiv_dataset-33151203.6141 | How the Unruh effect affects transition between classical and quantum
decoherences
quant-ph gr-qc
We investigate how the Unruh effect affects the transition between classical
and quantum decoherences for a general class of initial states and find that:
$(i)$ The quantum decoherence exists while $\lambda t\leq\lambda \widetilde{t}$
(the transition time) and the classical one can also affect the system's
evolution while $\lambda t\geq\lambda\widetilde{t}$ for both the bit and
phase-bit flips, which are different from the cases in inertial frame; $(ii)$
The classical correlations will be different constants corresponding to
different Unruh temperature and the quantum decoherence still dominates the
evolution of system as $\lambda t\geq\lambda\widetilde{t}$ for the phase flip;
And $(iii)$ as the Unruh temperature increases, the $\lambda\widetilde{t}$,
compared with that in inertial frame, will be bigger for phase flip but smaller
for bit flip. However, the $\lambda\widetilde{t}$ does not change no matter
what the Unruh effect is for phase-bit flip.
| arxiv topic:quant-ph gr-qc |
arxiv_dataset-33161203.6241 | Pseudo-Hermitian Quantum Mechanics with Unbounded Metric Operators
math-ph math.MP quant-ph
We extend the formulation of pseudo-Hermitian quantum mechanics to
eta-pseudo-Hermitian Hamiltonian operators H with an unbounded metric operator
eta. In particular, we give the details of the construction of the physical
Hilbert space, observables, and equivalent Hermitian Hamiltonian for the case
that H has a real and discrete spectrum and its eigenvectors belong to the
domain of eta and consequently its positive square root.
| arxiv topic:math-ph math.MP quant-ph |
arxiv_dataset-33171203.6341 | Sommerfeld Enhancement from Multiple Mediators
hep-ph
We study the Sommerfeld enhancement experienced by a scattering object that
couples to a tower of mediators. This can occur in, e.g., models of secluded
dark matter when the mediator scale is generated naturally by hidden-sector
confinement. Specializing to the case of a confining CFT, we show that
off-resonant values of the enhancement can be increased by ~ 20% for cases of
interest when (i) the (strongly-coupled) CFT admits a weakly-coupled dual
description and (ii) the conformal symmetry holds up to the Planck scale.
Larger enhancements are possible for lower UV scales due to an increase in the
coupling strength of the tower.
| arxiv topic:hep-ph |
arxiv_dataset-33181203.6441 | Finitely-Generated Projective Modules over the Theta-deformed 4-sphere
math.OA math-ph math.MP math.QA
We investigate the "theta-deformed spheres" C(S^{3}_{theta}) and
C(S^{4}_{theta}), where theta is any real number. We show that all
finitely-generated projective modules over C(S^{3}_{theta}) are free, and that
C(S^{4}_{theta}) has the cancellation property. We classify and construct all
finitely-generated projective modules over C(S^{4}_{\theta}) up to isomorphism.
An interesting feature is that if theta is irrational then there are nontrivial
"rank-1" modules over C(S^{4}_{\theta}). In that case, every finitely-generated
projective module over C(S^{4}_{\theta}) is a sum of a rank-1 module and a free
module. If theta is rational, the situation mirrors that for the commutative
case theta=0.
| arxiv topic:math.OA math-ph math.MP math.QA |
arxiv_dataset-33191203.6541 | A level raising result for modular Galois representations modulo prime
powers
math.NT
In this work we provide a level raising theorem for $\mod \lambda^n$ modular
Galois representations. It allows one to see such a Galois representation that
is modular of level $N$, weight 2 and trivial Nebentypus as one that is modular
of level $Np$, for a prime $p$ coprime to $N$, when a certain local condition
at $p$ is satisfied. It is a generalization of a result of Ribet concerning
$\mod \ell$ Galois representations.
| arxiv topic:math.NT |
arxiv_dataset-33201203.6641 | The clustering of galaxies in the SDSS-III Baryon Oscillation
Spectroscopic Survey: measurements of the growth of structure and expansion
rate at z=0.57 from anisotropic clustering
astro-ph.CO
We analyze the anisotropic clustering of massive galaxies from the Sloan
Digital Sky Survey III Baryon Oscillation Spectroscopic Survey (BOSS) Data
Release 9 (DR9) sample, which consists of 264,283 galaxies in the redshift
range 0.43 < z < 0.7 spanning 3,275 square degrees. Both peculiar velocities
and errors in the assumed redshift-distance relation ("Alcock-Paczynski
effect") generate correlations between clustering amplitude and orientation
with respect to the line-of-sight. Together with the sharp baryon acoustic
oscillation (BAO) standard ruler, our measurements of the broadband shape of
the monopole and quadrupole correlation functions simultaneously constrain the
comoving angular diameter distance (2190 +/- 61 Mpc) to z=0.57, the Hubble
expansion rate at z=0.57 (92.4 +/- 4.5 km/s/Mpc), and the growth rate of
structure at that same redshift (d sigma8/d ln a = 0.43 +/- 0.069). Our
analysis provides the best current direct determination of both DA and H in
galaxy clustering data using this technique. If we further assume a LCDM
expansion history, our growth constraint tightens to d sigma8/d ln a = 0.415
+/- 0.034. In combination with the cosmic microwave background, our
measurements of DA, H, and growth all separately require dark energy at z >
0.57, and when combined imply \Omega_{\Lambda} = 0.74 +/- 0.016, independent of
the Universe's evolution at z<0.57. In our companion paper (Samushia et al.
prep), we explore further cosmological implications of these observations.
| arxiv topic:astro-ph.CO |
arxiv_dataset-33211203.6741 | Optimal Linear Control over Channels with Signal-to-Noise Ratio
Constraints
cs.SY math.OC
We consider a networked control system where a linear time-invariant (LTI)
plant, subject to a stochastic disturbance, is controlled over a communication
channel with colored noise and a signal-to-noise ratio (SNR) constraint. The
controller is based on output feedback and consists of an encoder that measures
the plant output and transmits over the channel, and a decoder that receives
the channel output and issues the control signal. The objective is to stabilize
the plant and minimize a quadratic cost function, subject to the SNR
constraint.
It is shown that optimal LTI controllers can be obtained by solving a convex
optimization problem in the Youla parameter and performing a spectral
factorization. The functional to minimize is a sum of two terms: the first is
the cost in the classical linear quadratic control problem and the second is a
new term that is induced by the channel noise. %todo ta bort meningen?
A necessary and sufficient condition on the SNR for stabilization by an LTI
controller follows directly from a constraint of the optimization problem. It
is shown how the minimization can be approximated by a semidefinite program.
The solution is finally illustrated by a numerical example.
| arxiv topic:cs.SY math.OC |
arxiv_dataset-33221203.6841 | Local newforms and formal exterior square L-functions
math.NT math.RT
Let F be a non-archimedean local field of characteristic zero. Jacquet and
Shalika attached a family of zeta integrals to unitary irreducible generic
representations $\pi$ of GL_n(F). In this paper, we show that Jacquet-Shalika
integral attains a certain L-function, so called the formal exterior square
L-function, when the Whittaker function is associated to a newform for $\pi$.
By consideration on the Galois side, formal exterior square L-functions are
equal to exterior square L-functions for some principal series representations.
| arxiv topic:math.NT math.RT |
arxiv_dataset-33231204.0038 | Network analyzer measurements of spin transfer torques in magnetic
tunnel junctions
cond-mat.mes-hall cond-mat.mtrl-sci
We demonstrate a simple network-analyzer technique to make quantitative
measurements of the bias dependence of spin torque in a magnetic tunnel
junction. We apply a microwave current to exert an oscillating spin torque near
the ferromagnetic resonance frequency of the tunnel junction's free layer. This
produces an oscillating resistance that, together with an applied direct
current, generates a microwave signal that we measure with the network
analyzer. An analysis of the resonant response yields the strength and
direction of the spin torque at non-zero bias. We compare to measurements of
the spin torque vector by time-domain spin-torque ferromagnetic resonance.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-33241204.0138 | Schwinger pair creation in multilayer graphene
hep-ph cond-mat.str-el hep-lat
The low energy effective field model for the multilayer graphene (at ABC
stacking) in external Electric field is considered. The Schwinger pair creation
rate and the vacuum persistence probability are calculated using the semi -
classical approach.
| arxiv topic:hep-ph cond-mat.str-el hep-lat |
arxiv_dataset-33251204.0238 | The J/{\Psi} meson and the missing heavy baryon octet
physics.gen-ph
The 5D homogeneous space-time projection theory produces the Gell-Mann
standard model, and the gluon fields together with quantum gauge constraint
which is responsible for the major portion of the hadron mass as discussed
previously. It was found that the SU(3) representations for the mesons and
baryons together with the mass levels within each representations are generated
by the gluon fields strength factors which form their respective Lorentz jet
sum rules. In this paper, we deduce from the meson jet sum rule the remaining
mesons, the J/{\Psi} particle with the exact mass of 3096 MeV, and the Y
particles with mass 9460 MeV and 4140 MeV. For the baryons, there might be the
not yet found octet with mass levels in the 5 to 8 GeV energy region, with mass
level splitting also in the GeV range, far higher than those in the known octet
and decuplet
| arxiv topic:physics.gen-ph |
arxiv_dataset-33261204.0338 | The Complex of Non-separating embedded spheres
math.GT
For n >2, we shall show that the group Aut(NS(M)) of simplicial automorphisms
of the complex NS(M) of non-separating embedded spheres in the manifold
M,connected sum of n copies of S^2 X S^1, isomorphic to the group Out(F_n) of
outer automorphisms of the free group F_n, where $F_n$ is identified with the
fundamental group of M up to conjugacy of the base point in M.
| arxiv topic:math.GT |
arxiv_dataset-33271204.0438 | Efficient scheme for three-photon Greenberger-Horne-Zeilinger state
generation
quant-ph
We propose an efficient scheme for the generation of three-photon
Greenberger-Horne-Zeilinger (GHZ) state with linear optics and postselection.
Several devices are designed and a two-mode quantum nondemolition (QND)
detection is introduced to obtain the desired state. It is worth noting that
the states which have entanglement in both polarization and spatial degrees of
freedom are created in one of the designed setups. The method described in the
present scheme can create a large number of three-photon GHZ states in
principle. We also discuss an approach to generate the desired GHZ state in the
presence of channel noise.
| arxiv topic:quant-ph |
arxiv_dataset-33281204.0538 | Josephson effect between a two-band superconductor with the s++ or s+-
pairing symmetry and a conventional s-wave superconductor
cond-mat.supr-con cond-mat.mtrl-sci
In this work, we investigate the Josephson effect between a two-band
superconductor either with the $s++$ (two energy gaps have the same sign and
are fully gapped) pairing symmetry or $s\pm$ (two energy gaps have $\pi$ phase
difference and are fully gapped) pairing symmetry and a conventional s-wave
superconductors. The ground state, critical current, plasma modes, flux flow
dynamics, and response to external ac electric field, possible soliton
solutions are investigated. For junctions with the charge neutrality breaking,
we find a new plasma mode for junctions, which gives rise to new resonance
peaks in the Josephson flux flow region. Because of the frustrated interaction
in junctions with $s\pm$ pairing symmetry, time-reversal-symmetry (TRS) can be
broken if the frustration is optimized. In the TRS broken (TRSB) state, there
is a non-trivial phase difference between the two Josephson tunnelling
channels, which results in a non-trivial interference. Furthermore, we find a
novel massless plasma mode at the TRSB transition for junctions with the charge
neutrality breaking. In the TRSB state, a spontaneous magnetic flux appears
where there is a spatial inhomogeneity in the Josephson coupling, thus provides
a possible smoking-gun evidence for the underlying pairing symmetry.
| arxiv topic:cond-mat.supr-con cond-mat.mtrl-sci |
arxiv_dataset-33291204.0638 | Multi-quadratic quad equations: integrable cases from a
factorised-discriminant hypothesis
nlin.SI
We give integrable quad equations which are multi-quadratic (degree-two)
counterparts of the well-known multi-affine (degree-one) equations classified
by Adler, Bobenko and Suris (ABS). These multi-quadratic equations define
multi-valued evolution from initial data, but our construction is based on the
hypothesis that discriminants of the defining polynomial factorise in a
particular way that allows to reformulate the equation as a single-valued
system. Such reformulation comes at the cost of introducing auxiliary (edge)
variables and augmenting the initial data. Like the multi-affine equations
listed by ABS, these new models are consistent in multidimensions. We clarify
their relationship with the ABS list by obtaining Backlund transformations
connecting all but the primary multi-quadratic model back to equations from the
multi-affine class.
| arxiv topic:nlin.SI |
arxiv_dataset-33301204.0738 | Modeling a measurement-device-independent quantum key distribution
system
quant-ph
We present a detailed description of a widely applicable mathematical model
for quantum key distribution (QKD) systems implementing the
measurement-device-independent (MDI) protocol. The model is tested by comparing
its predictions with data taken using a proof-of-principle, time-bin
qubit-based QKD system in a secure laboratory environment (i.e. in a setting in
which eavesdropping can be excluded). The good agreement between the
predictions and the experimental data allows the model to be used to optimize
mean photon numbers per attenuated laser pulse, which are used to encode
quantum bits. This in turn allows optimization of secret key rates of existing
MDI-QKD systems, identification of rate-limiting components, and projection of
future performance. In addition, we also performed measurements over deployed
fiber, showing that our system's performance is not affected by
environment-induced perturbations.
| arxiv topic:quant-ph |
arxiv_dataset-33311204.0838 | Computationally efficient methods for modelling laser wakefield
acceleration in the blowout regime
physics.acc-ph physics.plasm-ph
Electron self-injection and acceleration until dephasing in the blowout
regime is studied for a set of initial conditions typical of recent experiments
with 100 terawatt-class lasers. Two different approaches to computationally
efficient, fully explicit, three-dimensional particle-in-cell modelling are
examined. First, the Cartesian code VORPAL using a perfect-dispersion
electromagnetic solver precisely describes the laser pulse and bubble dynamics,
taking advantage of coarser resolution in the propagation direction, with a
proportionally larger time step. Using third-order splines for macroparticles
helps suppress the sampling noise while keeping the usage of computational
resources modest. The second way to reduce the simulation load is using
reduced-geometry codes. In our case, the quasi-cylindrical code CALDER-CIRC
uses decomposition of fields and currents into a set of poloidal modes, while
the macroparticles move in the Cartesian 3D space. Cylindrical symmetry of the
interaction allows using just two modes, reducing the computational load to
roughly that of a planar Cartesian simulation while preserving the 3D nature of
the interaction. This significant economy of resources allows using fine
resolution in the direction of propagation and a small time step, making
numerical dispersion vanishingly small, together with a large number of
particles per cell, enabling good particle statistics. Quantitative agreement
of the two simulations indicates that they are free of numerical artefacts.
Both approaches thus retrieve physically correct evolution of the plasma
bubble, recovering the intrinsic connection of electron self-injection to the
nonlinear optical evolution of the driver.
| arxiv topic:physics.acc-ph physics.plasm-ph |
arxiv_dataset-33321204.0938 | Metrical musings on Littlewood and friends
math.NT
We prove a metrical result on a family of conjectures related to the
Littlewood conjecture, namely the original Littlewood conjecture, the mixed
Littlewood conjecture of de Mathan and Teuli\'e and a hybrid between a
conjecture of Cassels and the Littlewood conjecture. It is shown that the set
of numbers satisfying a strong version of all of these conjectures is large in
the sense of Hausdorff dimension restricted to the set of badly approximable
numbers.
| arxiv topic:math.NT |
arxiv_dataset-33331204.1038 | On Entire Solutions of an Elliptic System Modeling Phase Separations
math.AP
We study the qualitative properties of a limiting elliptic system arising in
phase separation for Bose-Einstein condensates with multiple states: \Delta u=u
v^2 in R^n, \Delta v= v u^2 in R^n, u, v>0\quad in R^n. When n=1, we prove
uniqueness of the one-dimensional profile. In dimension 2, we prove that stable
solutions with linear growth must be one-dimensional. Then we construct entire
solutions in $\R^2$ with polynomial growth $|x|^d$ for any positive integer $d
\geq 1$. For $d\geq 2$, these solutions are not one-dimensional. The
construction is also extended to multi-component elliptic systems.
| arxiv topic:math.AP |
arxiv_dataset-33341204.1138 | Simulation of NMR Fermi contact shifts for Lithium battery materials:
the need of an efficient hybrid functional approach
cond-mat.mtrl-sci
In the context of the development of NMR Fermi contact shift calculations for
assisting structural characterization of battery materials, we propose an
accurate, efficient, and robust approach based on the use of an all electron
method. The full-potential linearized augmented plane wave method, as
implemented in the WIEN2k code, is coupled with the use of hybrid functionals
for the evaluation of hyperfine field quantities. The WIEN2k code is able to
fully relax relativistic core states and uses an autoadaptive basis set that is
highly accurate for the determination of the hyperfine field. Furthermore, the
way hybrid functional approaches are implemented offers the possibility to use
them at no additional computational cost. In this paper, NMR Fermi contact
shifts for lithium are studied in different classes of paramagnetic materials
that present an interest in the field of Li-ion batteries: olivine LiMPO4 (M =
Mn, Fe, Co, Ni), anti-NASICON type Li3M2(PO4)3 (M = Fe, V), and
antifluorite-type Li6CoO4. Making use of the possibility to apply partial
hybrid functionals either only on the magnetic atom or also on the anionic
species, we evidence the role played by oxygen atoms on polarisation
mechanisms. Our method is quite general for an application on various types of
materials.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-33351204.1238 | Majorana-Like Modes of Light in a One-Dimensional Array of Nonlinear
Cavities
cond-mat.quant-gas quant-ph
The search for Majorana fermions in p-wave paired fermionic systems has
recently moved to the forefront of condensed-matter research. Here we propose
an alternative route and show theoretically that Majorana-like modes can be
realized and probed in a driven-dissipative system of strongly correlated
photons consisting of a chain of tunnel-coupled cavities, where p-wave pairing
effectively arises from the interplay between strong on-site interactions and
two-photon parametric driving. The nonlocal nature of these exotic modes could
be demonstrated through cross-correlation measurements carried out at the ends
of the chain---revealing a strong photon bunching signature---and their
non-Abelian properties could be simulated through tunnel-braid operations.
| arxiv topic:cond-mat.quant-gas quant-ph |
arxiv_dataset-33361204.1338 | SDSS J184037.78+642312.3: The First Pulsating Extremely Low Mass White
Dwarf
astro-ph.SR astro-ph.GA
We report the discovery of the first pulsating extremely low mass (ELM) white
dwarf (WD), SDSS J184037.78+642312.3 (hereafter J1840). This DA
(hydrogen-atmosphere) WD is by far the coolest and the lowest-mass pulsating
WD, with Teff = 9100 \pm 170 K and log g = 6.22 \pm 0.06, which corresponds to
a mass ~ 0.17 Msun. This low-mass pulsating WD greatly extends the DAV (or ZZ
Ceti) instability strip, effectively bridging the log g gap between WDs and
main sequence stars. We detect high-amplitude variability in J1840 on
timescales exceeding 4000 s, with a non-sinusoidal pulse shape. Our
observations also suggest that the variability is multi-periodic. The star is
in a 4.6 hr binary with another compact object, most likely another WD. Future,
more extensive time-series photometry of this ELM WD offers the first
opportunity to probe the interior of a low-mass, presumably He-core WD using
the tools of asteroseismology.
| arxiv topic:astro-ph.SR astro-ph.GA |
arxiv_dataset-33371204.1438 | On the Roman bondage number of a graph
math.CO
A Roman dominating function on a graph $G=(V,E)$ is a function
$f:V\rightarrow\{0,1,2\}$ such that every vertex $v\in V$ with $f(v)=0$ has at
least one neighbor $u\in V$ with $f(u)=2$. The weight of a Roman dominating
function is the value $f(V(G))=\sum_{u\in V(G)}f(u)$. The minimum weight of a
Roman dominating function on a graph $G$ is called the Roman domination number,
denoted by $\gamma_{R}(G)$. The Roman bondage number $b_{R}(G)$ of a graph $G$
with maximum degree at least two is the minimum cardinality of all sets
$E'\subseteq E(G)$ for which $\gamma_{R}(G-E')>\gamma_R(G)$. In this paper, we
first show that the decision problem for determining $b_{\rm R}(G)$ is NP-hard
even for bipartite graphs and then we establish some sharp bounds for $b_{\rm
R}(G)$ and characterizes all graphs attaining some of these bounds.
| arxiv topic:math.CO |
arxiv_dataset-33381204.1538 | Effects of transition metal substitutions on the incommensurability and
spin fluctuations in BaFe2As2 by elastic and inelastic neutron scattering
cond-mat.supr-con cond-mat.str-el
The spin fluctuation spectra from nonsuperconducting Cu-substituted, and
superconducting Co-substituted, BaFe2As2 are compared quantitatively by
inelastic neutron scattering measurements and are found to be indis-
tinguishable. Whereas diffraction studies show the appearance of incommensurate
spin-density wave order in Co and Ni substituted samples, the magnetic phase
diagram for Cu substitution does not display incommensu- rate order,
demonstrating that simple electron counting based on rigid-band concepts is
invalid. These results, supported by theoretical calculations, suggest that
substitutional impurity effects in the Fe plane play a signifi- cant role in
controlling magnetism and the appearance of superconductivity, with Cu
distinguished by enhanced impurity scattering and split-band behavior.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-33391204.1638 | Complete Integrability for Hamiltonian Systems with a Cone Potential
nlin.SI math.AP
It is known that, if a point in $R^n$ is driven by a bounded below potential
$V$, whose gradient is always in a closed convex cone which contains no lines,
then the velocity has a finite limit as time goes to $+\infty$.
The components of the asymptotic velocity, as functions of the initial data,
are trivially constants of motion. We find sufficient conditions for these
functions to be $C^k$ ($2\le k \le+\infty$) first integrals, independent and
pairwise in involution.
In this way we construct a large class of completely integrable systems. We
can deal with very different asymptotic behaviours of the potential and we have
persistence of the integrability under any small perturbation of the potential
in an arbitrary compact set.
| arxiv topic:nlin.SI math.AP |
arxiv_dataset-33401204.1738 | Spin-current rectification through a quantum dot using temperature bias
cond-mat.mes-hall
We analyze spin-dependent transport through a spin-diode in the presence of
spin-flip and under influence of temperature bias. The current polarization and
the spin accumulation are investigated in detail by means of reduced density
matrix. Results show that the spin accumulation is linearly increased when the
metallic electrode is warmer whereas, its behavior is more complicated when the
ferromagnetic lead is warmer. Furthermore, spin-flip causes that the current
polarization becomes not only a function of spin-flip rate but also a function
of temperature. The current polarization is reduced up to 90% if the time of
spin-flip is equal to the tunneling time. The behavior of spin-dependent
current is also studied as a function of temperature, spin-flip rate, and
polarization.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-33411204.1838 | Optimal error correction in topological subsystem codes
quant-ph cond-mat.dis-nn
A promising approach to overcome decoherence in quantum computing schemes is
to perform active quantum error correction using topology. Topological
subsystem codes incorporate both the benefits of topological and subsystem
codes, allowing for error syndrome recovery with only 2-local measurements in a
two-dimensional array of qubits. We study the error threshold for topological
subsystem color codes under very general external noise conditions. By
transforming the problem into a classical disordered spin model, we estimate
using Monte Carlo simulations that topological subsystem codes have an optimal
error tolerance of 5.5(2)%. This means there is ample space for improvement in
existing error-correcting algorithms that typically find a threshold of
approximately 2%.
| arxiv topic:quant-ph cond-mat.dis-nn |
arxiv_dataset-33421204.1938 | Heights and quadratic forms: on Cassels' theorem and its generalizations
math.NT
In this survey paper, we discuss the classical Cassels' theorem on existence
of small-height zeros of quadratic forms over Q and its many extensions, to
different fields and rings, as well as to more general situations, such as
existence of totally isotropic small-height subspaces. We also discuss related
recent results on effective structural theorems for quadratic spaces, as well
as Cassels'-type theorems for small-height zeros of quadratic forms with
additional conditions. We conclude with a selection of open problems.
| arxiv topic:math.NT |
arxiv_dataset-33431204.2038 | A New Approach to Analytic, Non-Perturbative and Gauge-Invariant QCD
hep-ph hep-th
Following a previous calculation of quark scattering in eikonal
approximation, this paper presents a new, analytic and rigorous approach to the
calculation of QCD phenomena. In this formulation a basic distinction between
the conventional "idealistic" description of QCD and a more "realistic"
description is brought into focus by a non-perturbative, gauge-invariant
evaluation of the Schwinger solution for the QCD generating functional in terms
of the exact Fradkin representations of the Green's functional and the vacuum
functional. Because quarks exist asymptotically only in bound states, their
transverse coordinates can never be measured with arbitrary precision; the
non-perturbative neglect of this statement leads to obstructions that are
easily corrected by invoking in the basic Lagrangian a probability amplitude
which describes such transverse imprecision.
The second result of this non-perturbative analysis is the appearance of a
new and simplifying output called "Effective Locality", in which the
interactions between quarks by the exchange of a "gluon bundle" - which
"bundle" contains an infinite number of gluons, including cubic and quartic
gluon interactions - display an exact locality property that reduces the
several functional integrals of the formulation down to a set of ordinary
integrals. It should be emphasized that "non-perturbative" here refers to the
effective summation of all gluons between a pair of quark lines, but does not
(yet) include a summation over all closed-quark loops which are tied by
gluon-bundle exchange to the rest of the "Bundle Diagram". As an example of the
power of these methods we offer as a first analytic calculation the
quark-antiquark binding potential of a pion, and the corresponding three-quark
binding potential of a nucleon, obtained in a simple way from relevant eikonal
scattering approximations.
| arxiv topic:hep-ph hep-th |
arxiv_dataset-33441204.2138 | Role of context in usability evaluations: A review
cs.HC
Usability is often defined as the ability of a system to carry out specific
tasks by specific users in a specific context. Usability evaluation involves
testing the system for its expected usability. Usability testing is performed
in natural environment (field) or artificial environment (laboratory). The
result of usability evaluation is affected by the environment in which it is
carried out. Previous studies have focused only on the physical environment
(lab and field) effect on the results but rarely focused on the effect of
social environment (people present during testing). Therefore, this study aims
to review how important it is to take context into account during usability
evaluation. Context is explored through the theory of behaviour settings,
according to which behaviour of individuals is strongly influenced by the
physical as well as the social environment in which they function. The result
of this review indicates that the physical and social context plays a
substantial role in usability evaluations. Further, it also suggests that the
usability evaluation model should encompass context as an important component
in the framework.
| arxiv topic:cs.HC |
arxiv_dataset-33451204.2238 | On Zero Forcing Number of Functigraphs
math.CO
\emph{Zero forcing number}, $Z(G)$, of a graph $G$ is the minimum cardinality
of a set $S$ of black vertices (whereas vertices in $V(G) \setminus S$ are
colored white) such that $V(G)$ is turned black after finitely many
applications of "the color-change rule": a white vertex is converted black if
it is the only white neighbor of a black vertex. Zero forcing number was
introduced and used to bound the minimum rank of graphs by the "AIM Minimum
Rank -- Special Graphs Work Group". Let $G_1$ and $G_2$ be disjoint copies of a
graph $G$ and let $f: V(G_1) \rightarrow V(G_2)$ be a function. Then a
\emph{functigraph} $C(G, f)=(V, E)$ has the vertex set $V=V(G_1) \cup V(G_2)$
and the edge set $E=E(G_1) \cup E(G_2) \cup \{uv \mid v=f(u)\}$. For a
connected graph $G$ of order $n \ge 3$, it is readily seen that $1+\delta(G)
\le Z(C(G, \sigma)) \le n$ for any permutation $\sigma$; we show that $1+
\delta(G) \le Z(C(G, f)) \le 2n-2$ for any function $f$, where $\delta(G)$ is
the minimum degree of $G$. We give examples showing that there does not exist a
function $g$ such that, for every pair $(G,f)$, $Z(G)<g(Z(C(G,f)))$ or
$g(Z(G))>Z(C(G,f))$. We further investigate the zero forcing number of
functigraphs on complete graphs, on cycles, and on paths.
| arxiv topic:math.CO |
arxiv_dataset-33461204.2338 | Asymptotic behavior of the socle of Frobenius powers
math.AC
Let $(R, m)$ be a local ring of prime characteristic $p$ and $q$ a varying
power of $p$. We study the asymptotic behavior of the socle of $R/I^{[q]}$
where $I$ is an $m$ -primary ideal of $R$. In the graded case, we define the
notion of diagonal $F$-threshold of $R$ as the limit of the top socle degree of
$R/m^{[q]}$ over $q$ when $q \to \infty$. Diagonal $F$-threshold exists as a
positive number (rational number in the latter case) when: (1) $R$ is either a
complete intersection or $R$ is $F$-pure on the punctured spectrum; (2) $R$ is
a two dimensional normal domain. In the latter case, we also discuss its
geometric interpretation and apply it to determine the strong semistability of
the syzygy bundle of $(x^d, y^d,z^d)$ over the smooth projective curve in
$\mathbb P^2$ defined by $x^n+y^n+z^n=0$. The rest of this paper concerns a
different question about how the length of the socle of $R/I^{[q]}$ vary as $q$
varies. We give explicit calculations of the length of the socle of $R/m^{[q]}$
for a class of hypersurface rings which attain the minimal Hilbert-Kunz
function. We finally show, under mild conditions, the growth of such length
function and the growth of the second Betti numbers of $R/m^{[q]}$ differ by at
most a constant, as $q \to \infty$.
| arxiv topic:math.AC |
arxiv_dataset-33471204.2438 | On \sigma-convex subsets in spaces of scatteredly continuous functions
math.GN math.FA
We prove that for any topological space $X$ of countable tightness, each
\sigma-convex subspace $\F$ of the space $SC_p(X)$ of scatteredly continuous
real-valued functions on $X$ has network weight $nw(\F)\le nw(X)$. This implies
that for a metrizable separable space $X$, each compact convex subset in the
function space $SC_p(X)$ is metrizable. Another corollary says that two
Tychonoff spaces $X,Y$ with countable tightness and topologically isomorphic
linear topological spaces $SC_p(X)$ and $SC_p(Y)$ have the same network weight
$nw(X)=nw(Y)$. Also we prove that each zero-dimensional separable Rosenthal
compact space is homeomorphic to a compact subset of the function space
$SC_p(\omega^\omega)$ over the space $\omega^\omega$ of irrationals.
| arxiv topic:math.GN math.FA |
arxiv_dataset-33481204.2538 | Quantum criticality in spin chains with non-ohmic dissipation
cond-mat.stat-mech cond-mat.other
We investigate the critical behavior of a spin chain coupled to bosonic baths
characterized by a spectral density proportional to $\omega^s$, with $s>1$.
Varying $s$ changes the effective dimension $d_\text{eff} = d + z$ of the
system, where $z$ is the dynamical critical exponent and the number of spatial
dimensions $d$ is set to one. We consider two extreme cases of clock models,
namely Ising-like and U(1)-symmetric ones, and find the critical exponents
using Monte Carlo methods. The dynamical critical exponent and the anomalous
scaling dimension $\eta$ are independent of the order parameter symmetry for
all values of $s$. The dynamical critical exponent varies continuously from $z
\approx 2$ for $s=1$ to $z=1$ for $s=2$, and the anomalous scaling dimension
evolves correspondingly from $\eta \gtrsim 0$ to $\eta = 1/4$. The latter
exponent values are readily understood from the effective dimensionality of the
system being $d_\text{eff} \approx 3$ for $s=1$, while for $s=2$ the anomalous
dimension takes the well-known exact value for the 2D Ising and XY models,
since then $d_{\rm{eff}}=2$. A noteworthy feature is, however, that $z$
approaches unity and $\eta$ approaches 1/4 for values of $s < 2$, while naive
scaling would predict the dissipation to become irrelevant for $s=2$. Instead,
we find that $z=1,\eta=1/4$ for $s \approx 1.75$ for both Ising-like and U(1)
order parameter symmetry. These results lead us to conjecture that for all
site-dissipative $Z_q$ chains, these two exponents are related by the scaling
relation $z = \text{max} {(2-\eta)/s, 1}$. We also connect our results to
quantum criticality in nondissipative spin chains with long-range spatial
interactions.
| arxiv topic:cond-mat.stat-mech cond-mat.other |
arxiv_dataset-33491204.2638 | Perturbative Expansion Technique for Non-linear FBSDEs with Interacting
Particle Method
q-fin.CP q-fin.PR q-fin.RM
In this paper, we propose an efficient Monte Carlo implementation of
non-linear FBSDEs as a system of interacting particles inspired by the ideas of
branching diffusion method. It will be particularly useful to investigate large
and complex systems, and hence it is a good complement of our previous work
presenting an analytical perturbation procedure for generic non-linear FBSDEs.
There appear multiple species of particles, where the first one follows the
diffusion of the original underlying state, and the others the Malliavin
derivatives with a grading structure. The number of branching points are capped
by the order of perturbation, which is expected to make the scheme less
numerically intensive. The proposed method can be applied to semi-linear
problems, such as American and Bermudan options, Credit Value Adjustment (CVA),
and even fully non-linear issues, such as the optimal portfolio problems in
incomplete and/or constrained markets, feedbacks from large investors, and also
the analysis of various risk measures.
| arxiv topic:q-fin.CP q-fin.PR q-fin.RM |
arxiv_dataset-33501204.2738 | Experimental Investigation of the Evolution of Gaussian Quantum Discord
in an Open System
quant-ph
Gaussian quantum discord is a measure of quantum correlations in Gaussian
systems. Using Gaussian discord we quantify the quantum correlations of a
bipartite entangled state and a separable two-mode mixture of coherent states.
We experimentally analyze the effect of noise addition and dissipation on
Gaussian discord and show that the former noise degrades the discord while the
latter noise for some states leads to an increase of the discord. In
particular, we experimentally demonstrate the near-death of discord by noisy
evolution and its revival through dissipation.
| arxiv topic:quant-ph |
arxiv_dataset-33511204.2838 | Evidence of Gunn-Peterson damping wings in high-z quasar spectra:
strengthening the case for incomplete reionization
astro-ph.CO
The spectra of several high-redshift (z>6) quasars have shown evidence for a
Gunn-Peterson (GP) damping wing, indicating a substantial mean neutral hydrogen
fraction (x_HI > 0.03) in the z ~ 6 intergalactic medium (IGM). However,
previous analyses assumed that the IGM was uniformly ionized outside of the
quasar's HII region. Here we relax this assumption and model patchy
reionization scenarios for a range of IGM and quasar parameters. We quantify
the impact of these differences on the inferred x_HI, by fitting the spectra of
three quasars: SDSS J1148+5251 (z=6.419), J1030+0524 (z=6.308), and J1623+3112
(z=6.247). We find that the best-fit values of x_HI in the patchy models agree
well with the uniform case. More importantly, we confirm that the observed
spectra favor the presence of a GP damping wing, with peak likelihoods
decreasing by factors of > few - 10 when the spectra are modeled without a
damping wing. We also find that the Ly alpha absorption spectra, by themselves,
cannot distinguish the damping wing in a relatively neutral IGM from a damping
wing in a highly ionized IGM, caused either by an isolated neutral patch, or by
a damped Ly alpha absorber (DLA). However, neutral patches in a highly ionized
universe (x_HI < 0.01), and DLAs with the large required column densities (N_HI
> few x 10^{20} cm^{-2}) are both rare. As a result, when we include reasonable
prior probabilities for the line of sight (LOS) to intercept either a neutral
patch or a DLA at the required distance of ~ 40-60 comoving Mpc away from the
quasar, we find strong lower limits on the neutral fraction in the IGM, x_HI >
0.1 (at 95% confidence). This strengthens earlier claims that a substantial
global fraction of hydrogen in the z~6 IGM is in neutral form.
| arxiv topic:astro-ph.CO |
arxiv_dataset-33521204.2938 | Strong approximation of almost periodic functions
math.CA
We consider summability methods generated by the class GM(2b). We generalize
some related results of P. Pych-Taberska [Studia Math. XCVI (1990), 91-103] on
strong approximation of almost periodic functions by their Fourier series and
S. M. Mazhar and V. Totik [J. Approx. Theory, 60(1990), 174-182] on
approximation of periodic functions by matrix means of their Fourier series.
| arxiv topic:math.CA |
arxiv_dataset-33531204.3038 | On Control Of Sobolev Norms For Some Semilinear Wave Equations With
Localized Data
math.AP
We establish new bounds of the Sobolev norms of solutions of semilinear wave
equations for data lying in the Hs, s<1, closure of compactly supported data
inside a ball of radius R, with R a fixed and positive number. In order to do
that we perform an analysis in the neighborhood of the cone, using an almost
Shatah-Struwe estimate, an almost conservation law and some estimates for
localized functions: this allows to prove a decay estimate and establish a low
frequency estimate of the position of the solution. Then, in order to establish
a high frequency estimate of the position and an estimate of the velocity, we
use this decay estimate and another almost conservation law.
| arxiv topic:math.AP |
arxiv_dataset-33541204.3138 | Quantization of area for event and Cauchy horizons of the Kerr-Newman
black hole
gr-qc hep-th
Based on various string theoretic constructions, and various string-inspired
generalizations thereof, there have been repeated suggestions that the areas of
black hole event horizons might be quantized in a quite specific manner, in
terms of linear combinations of square roots of positive integers. It is
important to realise that there are significant physical constraints on such
integer-based proposals when one (somewhat speculatively) attempts to extend
them outside their original extremal and supersymmetric framework.
Specifically, in their most natural and direct physical interpretations, some
of the more speculative integer-based proposals for the quantization of horizon
areas fail for the ordinary Kerr-Newman black holes in (3+1) dimensions,
essentially because the fine structure constant is not an integer. A more
baroque interpretation involves asserting the fine structure constant is the
square root of a rational number; but such a proposal has its own problems.
Insofar as one takes (3+1) general relativity (plus the usual quantization of
angular momentum and electric charge) as being paramount, the known explicitly
calculable spectra of horizon areas for the physically compelling Kerr-Newman
spacetimes indicate that some caution is called for when assessing the
universality of some of the more speculative integer-based string-inspired
proposals.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-33551204.3238 | Reliable communication over non-binary insertion/deletion channels
cs.IT math.IT
We consider the problem of reliable communication over non-binary
insertion/deletion channels where symbols are randomly deleted from or inserted
in the transmitted sequence and all symbols are corrupted by additive white
Gaussian noise. To this end, we utilize the inherent redundancy achievable in
non-binary symbol sets by first expanding the symbol set and then allocating
part of the bits associated with each symbol to watermark symbols. The
watermark sequence, known at the receiver, is then used by a forward-backward
algorithm to provide soft information for an outer code which decodes the
transmitted sequence. Through numerical results and discussions, we evaluate
the performance of the proposed solution and show that it leads to significant
system ability to detect and correct insertions/deletions. We also provide
estimates of the maximum achievable information rates of the system, compare
them with the available bounds, and construct practical codes capable of
approaching these limits.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-33561204.3338 | Flux-correlation approach to characterizing reaction pathways in quantum
systems: A study of condensed-phase proton-coupled electron transfer
cond-mat.stat-mech physics.chem-ph
We introduce a simple method for characterizing reactive pathways in quantum
systems. Flux auto- correlation and cross-correlation functions are employed to
develop a quantitative measure of dynamical coupling in quantum transition
events, such as reactive tunneling and resonant energy transfer. We utilize the
method to study condensed-phase proton-coupled electron transfer (PCET)
reactions and to determine the relative importance of competing concerted and
sequential reaction pathways. Results presented here include numerically exact
quantum dynamics simulations for model condensed-phase PCET reactions. This
work demonstrates the applicability of the new method for the analysis of both
approximate and exact quantum dynamics simulations.
| arxiv topic:cond-mat.stat-mech physics.chem-ph |
arxiv_dataset-33571204.3438 | HP-sequence design for lattice proteins - an exact enumeration study on
diamond as well as square lattice
cond-mat.stat-mech physics.bio-ph physics.comp-ph
We present an exact enumeration algorithm for identifying the {\it native}
configuration - a maximally compact self avoiding walk configuration that is
also the minimum energy configuration for a given set of contact-energy
schemes; the process is implicitly sequence-dependent. In particular, we show
that the 25-step native configuration on a diamond lattice consists of two
sheet-like structures and is the same for all the contact-energy schemes,
${(-1,0,0);(-7,-3,0); (-7,-3,-1); (-7,-3,1)}$; on a square lattice also, the
24-step native configuration is independent of the energy schemes considered.
However, the designing sequence for the diamond lattice walk depends on the
energy schemes used whereas that for the square lattice walk does not. We have
calculated the temperature-dependent specific heat for these designed sequences
and the four energy schemes using the exact density of states. These data show
that the energy scheme $(-7,-3,-1)$ is preferable to the other three for both
diamond and square lattice because the associated sequences give rise to a
sharp low-temperature peak. We have also presented data for shorter (23-, 21-
and 17-step) walks on a diamond lattice to show that this algorithm helps
identify a unique minimum energy configuration by suitably taking care of the
ground-state degeneracy. Interestingly, all these shorter target configurations
also show sheet-like secondary structures.
| arxiv topic:cond-mat.stat-mech physics.bio-ph physics.comp-ph |
arxiv_dataset-33581204.3538 | Muon Collider: Plans, Progress and Challenges
physics.acc-ph hep-ex
We in the physics community expect the LHC to uncover new physics in the next
few years. The character and energy scale of the new physics remain unclear,
but it is likely that data from the LHC will need to be complemented by
information from a lepton collider which can provide for precise examination of
new phenomena. We describe the concept, accelerator design, and detector R&D
for a high energy Muon Collider as well as the challenges associated with the
machine and its detector environment.
| arxiv topic:physics.acc-ph hep-ex |
arxiv_dataset-33591204.3638 | Water ice in the Kuiper belt
astro-ph.EP
We examine a large collection of low resolution near-infrared spectra of
Kuiper belt objects and centaurs in an attempt to understand the presence of
water ice in the Kuiper belt. We find that water ice on the surface of these
objects occurs in three separate manners: (1) Haumea family members uniquely
show surfaces of nearly pure water ice, presumably a consequence of the
fragmentation of the icy mantle of a larger differentiated proto-Haumea; (2)
large objects with absolute magnitudes of $H<3$ (and a limited number to H=4.5)
have surface coverings of water ice - perhaps mixed with ammonia - that appears
to be related to possibly ancient cryovolcanism on these large objects; and (3)
smaller KBOs and centaurs which are neither Haumea family members nor
cold-classical KBOs appear to divide into two families (which we refer to as
"neutral" and "red"), each of which is a mixture of a common nearly-neutral
component and either a slightly red or very red component that also includes
water ice. A model suggesting that the difference between neutral and red
objects is due to formation in an early compact solar system either inside or
outside, respectively, of the ~20 AU methanol evaporation line is supported by
the observation that methanol is only detected on the reddest objects, which
are those which would be expected to have the most of the methanol containing
mixture.
| arxiv topic:astro-ph.EP |
arxiv_dataset-33601204.3738 | The Two-Component Camassa-Holm Equations CH(2,1) and CH(2,2):
First-Order Integrating Factors and Conservation Laws
nlin.SI
Recently, Holm and Ivanov, proposed and studied a class of multi-component
generalisations of the Camassa-Holm equations [D D Holm and R I Ivanov,
Multi-component generalizations of the CH equation: geometrical aspects,
peakons and numerical examples, J. Phys A: Math. Theor. 43, 492001 (20pp),
2010]. We consider two of those systems, denoted by Holm and Ivanov by CH(2,1)
and CH(2,2), and report a class of integrating factors and its corresponding
conservation laws for these two systems. In particular, we obtain the complete
sent of first-order integrating factors for the systems in Cauchy-Kovalevskaya
form and evaluate the corresponding sets of conservation laws for CH(2,1) and
CH(2,2).
| arxiv topic:nlin.SI |
arxiv_dataset-33611204.3838 | Energy cost reduction in the synchronization of a pair of nonidentical
coupled Hindmarsh-Rose neurons
cs.AI nlin.CD q-bio.NC
Many biological processes involve synchronization between nonequivalent
systems, i.e, systems where the difference is limited to a rather small
parameter mismatch. The maintenance of the synchronized regime in this cases is
energetically costly \cite{1}. This work studies the energy implications of
synchronization phenomena in a pair of structurally flexible coupled neurons
that interact through electrical coupling. We show that the forced
synchronization between two nonidentical neurons creates appropriate conditions
for an efficient actuation of adaptive laws able to make the neurons
structurally approach their behaviours in order to decrease the flow of energy
required to maintain the synchronization regime.
| arxiv topic:cs.AI nlin.CD q-bio.NC |
arxiv_dataset-33621204.3938 | An aggregation equation with degenerate diffusion: qualitative property
of solutions
math.AP math-ph math.MP
We study a nonlocal aggregation equation with degenerate diffusion, set in a
periodic domain. This equation represents the generalization to $m > 1$ of the
McKean-Vlasov equation where here the "diffusive" portion of the dynamics are
governed by Porous medium self-interactions. We focus primarily on $m\in(1,2]$
with particular emphasis on $m = 2$. In general, we establish regularity
properties and, for small interaction, exponential decay to the uniform
stationary solution. For $m=2$, we obtain essentially sharp results on the rate
of decay for the entire regime up to the (sharp) transitional value of the
interaction parameter.
| arxiv topic:math.AP math-ph math.MP |
arxiv_dataset-33631204.4038 | Dephasing of Cooper pairs and subgap electron transport in
superconducting hybrids
cond-mat.mes-hall cond-mat.supr-con
We argue that electron-electron interactions fundamentally restrict the
penetration length of Cooper pairs into a diffusive normal metal (N) from a
superconductor (S). At low temperatures this Cooper pair dephasing length
$L_\varphi$ remains finite and does not diverge at $T \to 0$. We evaluate the
subgap conductance of NS hybrids in the presence of electron-electron
interactions and demonstrate that this new length $L_\varphi$ can be directly
extracted from conductance measurements in such structures.
| arxiv topic:cond-mat.mes-hall cond-mat.supr-con |
arxiv_dataset-33641204.4138 | Uniform convergence to equilibrium for granular media
math.AP
We study the long time asymptotics of a nonlinear, nonlocal equation used in
the modelling of granular media. We prove a uniform exponential convergence to
equilibrium for degenerately convex and non convex interaction or confinement
potentials, improving in particular results by J. A. Carrillo, R. J. McCann and
C. Villani. The method is based on studying the dissipation of the Wasserstein
distance between a solution and the steady state.
| arxiv topic:math.AP |
arxiv_dataset-33651204.4238 | MCMC-free adaptive Bayesian procedures using random series prior
math.ST stat.TH
We consider priors for several nonparametric Bayesian models which use finite
random series with a random number of terms. The prior is constructed through
distributions on the number of basis functions and the associated coefficients.
We derive a general result on the construction of an appropriate sieve and
obtain adaptive posterior contraction rates for all smoothness levels of the
function in the true model. We apply this general result on several statistical
problems such as signal processing, density estimation, nonparametric additive
regression, classification, spectral density estimation, functional regression
etc. The prior can be viewed as an alternative to commonly used Gaussian
process prior, but can be analyzed by relatively simpler techniques and in many
cases allows a simpler approach to computation without using Markov chain
Monte-Carlo (MCMC) methods. A simulation study was conducted to show that the
performance of the random series prior is comparable to that of a Gaussian
process prior.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-33661204.4338 | Extensions of superalgebras of Krichever-Novikov type
math.RA
An explicit construction of central extensions of Lie superalgebras of
Krichever-Novikov type is given. In the case of Jordan superalgebras related to
the superalgebras of Krichever-Novikov type we calculate a 1-cocycle with
coefficients in the dual space.
| arxiv topic:math.RA |
arxiv_dataset-33671204.4438 | Effects of Spatial Dispersion on the Casimir Force between Graphene
Sheets
cond-mat.mes-hall
The Casimir force between graphene sheets is investigated with emphasis on
the effect from spatial dispersion using a combination of factors, such as a
nonzero chemical potential and an induced energy gap. We distinguish between
two regimes for the interaction - T=0 $K$ and $T\neq 0$ $K$. It is found that
the quantum mechanical interaction (T=0 $K$) retains its distance dependence
regardless of the inclusion of dispersion. The spatial dispersion from the
finite temperature Casimir force is found to contribute for the most part from
$n=0$ Matsubara term. These effects become important as graphene is tailored to
become a poor conductor by inducing a band gap.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-33681204.4538 | Algebraic vector bundles on spheres
math.AG math.AC math.AT math.KT
We determine the first non-stable ${\mathbb A}^1$-homotopy sheaf of $SL_n$.
Using techniques of obstruction theory involving the ${\mathbb A}^1$-Postnikov
tower, supported by some ideas from the theory of unimodular rows, we classify
vector bundles of rank $\geq d-1$ on split smooth affine quadrics of dimension
$2d-1$. These computations allow us to answer a question posed by Nori, which
gives a criterion for completability of certain unimodular rows. Furthermore,
we study compatibility of our computations of ${\mathbb A}^1$-homotopy sheaves
with real and complex realization.
| arxiv topic:math.AG math.AC math.AT math.KT |
arxiv_dataset-33691204.4638 | Two-Photon Airy Disk
quant-ph physics.optics
We report an experimental observation of quantum Airy disk diffraction
pattern using an entangled two-photon source. In contrast to the previous
quantum lithography experiments where the subwavelength diffraction patterns
were observed in the far field limit, we perform the Fraunhofer diffraction
experiment with a convex lens. The experimental result shows that the
two-photon Airy disk is provided with the super-resolution spot, which
surpasses the classical diffraction limit. In particular, the spot size can be
well controlled by the focal length, which adapted to optical super-focusing.
Our experiment can promote potential application of quantum lithography.
| arxiv topic:quant-ph physics.optics |
arxiv_dataset-33701204.4738 | A proof of Andrews' conjecture on Partitions with no short sequences
math.NT math.PR
Holroyd, Liggett, and Romik introduced the following probability model. Let
$C_1, C_2,...$ be independent events with probabilities $\P_s(C_n)= 1-e^{-ns}$
under a probability measure $\P_s$ with $0<s<1$. Let $A_k$ be the event that
there is no sequence of $k$ consecutive $C_i$ that do not occur. We given an
asymptotic for $\P_s(A_k)$ with a relative error term that goes to 0 as $s\to
0$. This establishes a conjecture of Andrews.
| arxiv topic:math.NT math.PR |
arxiv_dataset-33711204.4838 | On $k$-gonal loci in Severi varieties on general $K3$ surfaces and
rational curves on hyperk\"ahler manifolds
math.AG
In this paper we study the gonality of the normalizations of curves in the
linear system $|H|$ of a general primitively polarized complex $K3$ surface
$(S,H)$ of genus $p$. We prove two main results. First we give a necessary
condition on $p, g, r, d$ for the existence of a curve in $ |H|$ with geometric
genus $g$ whose normalization has a $g^ r_d$. Secondly we prove that for all
numerical cases compatible with the above necessary condition, there is a
family of \emph{nodal} curves in $|H|$ of genus $g$ carrying a $g^1_k$ and of
dimension equal to the \emph{expected dimension} $\min\{2(k-1),g\}$. Relations
with the Mori cone of the hyperk\"ahler manifold $\Hilb^ k(S)$ are discussed.
| arxiv topic:math.AG |
arxiv_dataset-33721204.4938 | Distributions of missing sums and differences
math.NT
This paper discusses the distributions of missing sums and differences.
| arxiv topic:math.NT |
arxiv_dataset-33731204.5038 | Bipolaron formation in organic semiconductors at the interface with
dielectric gates
cond-mat.str-el cond-mat.mtrl-sci cond-mat.soft
The formation of the electron-phonon induced bipolaron is shown to be
feasible in organic semiconductors at the interface with dielectric gates due
to the coupling of the carriers with interface vibrational modes and to the
weak to intermediate strength of bulk electron-electron interaction. The
polaronic bound states are found to be quite robust in a model with realistic
strengths of electron coupling to both bulk and interface phonons. The
crossover to nearly on-site bipolarons occurs for coupling values much smaller
than those for nearly on-site polarons, but, on the other hand, it gives rise
to an activated behavior of mobility with much larger activation energies. The
results are discussed in connection with rubrene field-effect transistors.
| arxiv topic:cond-mat.str-el cond-mat.mtrl-sci cond-mat.soft |
arxiv_dataset-33741204.5138 | Quantum cohomology of the cotangent bundle of a flag variety as a
Yangian Bethe algebra
math.AG math.QA math.RT
We interpret the equivariant cohomology algebra
H^*_{GL_n\times\C^*}(T^*F_\lambda;\C) of the cotangent bundle of a partial flag
variety F_\lambda parametrizing chains of subspaces 0=F_0\subset
F_1\subset\dots\subset F_N =\C^n, \dim F_i/F_{i-1}=\lambda_i, as the Yangian
Bethe algebra of the gl_N-weight subspace of a gl_N Yangian module. Under this
identification the dynamical connection of [TV1] turns into the quantum
connection of [BMO] and [MO]. As a result of this identification we describe
the algebra of quantum multiplication on H^*_{GL_n\times\C^*}(T^*F_\lambda;\C)
as the algebra of functions on fibers of a discrete Wronski map. In particular
this gives generators and relations of that algebra. This identification also
gives us hypergeometric solutions of the associated quantum differential
equation. That fact manifests the Landau-Ginzburg mirror symmetry for the
cotangent bundle of the flag variety.
| arxiv topic:math.AG math.QA math.RT |
arxiv_dataset-33751204.5238 | Selective Gas Sensing with a Single Pristine Graphene Transistor
cond-mat.mtrl-sci cond-mat.mes-hall
We show that vapors of different chemicals produce distinguishably different
effects on the low-frequency noise spectra of graphene. It was found in a
systematic study that some gases change the electrical resistance of graphene
devices without changing their low-frequency noise spectra while other gases
modify the noise spectra by inducing Lorentzian components with distinctive
features. The characteristic frequency fc of the Lorentzian noise bulges in
graphene devices is different for different chemicals and varies from fc=10 -
20 Hz to fc=1300 - 1600 Hz for tetrahydrofuran and chloroform vapors,
respectively. The obtained results indicate that the low-frequency noise in
combination with other sensing parameters can allow one to achieve the
selective gas sensing with a single pristine graphene transistor. Our method of
gas sensing with graphene does not require graphene surface functionalization
or fabrication of an array of the devices with each tuned to a certain
chemical.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall |
arxiv_dataset-33761204.5338 | Wadge-like reducibilities on arbitrary quasi-Polish spaces
math.LO math.GN
The structure of the Wadge degrees on zero-dimensional spaces is very simple
(almost well-ordered), but for many other natural non-zero-dimensional spaces
(including the space of reals) this structure is much more complicated. We
consider weaker notions of reducibility, including the so-called
\Delta^0_\alpha-reductions, and try to find for various natural topological
spaces X the least ordinal \alpha_X such that for every \alpha_X \leq \beta <
\omega_1 the degree-structure induced on X by the \Delta^0_\beta-reductions is
simple (i.e. similar to the Wadge hierarchy on the Baire space). We show that
\alpha_X \leq {\omega} for every quasi-Polish space X, that \alpha_X \leq 3 for
quasi-Polish spaces of dimension different from \infty, and that this last
bound is in fact optimal for many (quasi-)Polish spaces, including the real
line and its powers.
| arxiv topic:math.LO math.GN |
arxiv_dataset-33771204.5438 | Stability under deformations of Hermite-Einstein almost-K\"ahler metrics
math.DG
On a 4-dimensional compact symplectic manifold, we consider a smooth family
of compatible almost-complex structures such that at time zero the induced
metric is Hermite-Einstein almost-K\"ahler metric with zero or negative
Hermitian scalar curvature. We prove, under certain hypothesis, the existence
of a smooth family of compatible almost-complex structures, diffeomorphic at
each time to the initial family, and inducing constant Hermitian scalar
curvature metrics.
| arxiv topic:math.DG |
arxiv_dataset-33781204.5538 | Numerical Simulations of Optically Thick Accretion onto a Black Hole -
I. Spherical Case
astro-ph.IM astro-ph.HE
Modeling the radiation generated by accreting matter is an important step
towards realistic simulations of black hole accretion disks, especially at high
accretion rates. To this end, we have recently added radiation transport to the
existing general relativistic magnetohydrodynamic code, Cosmos++. However,
before attempting to model radiative accretion disks, we have tested the new
code using a series of shock tube and Bondi (spherical inflow) problems. The
four radiative shock tube tests, first presented by Farris et al. (2008), have
known analytic solutions, allowing us to calculate errors and convergence rates
for our code. The Bondi problem only has an analytic solution when radiative
processes are ignored, but is pertinent because it is closer to the physics we
ultimately want to study. In our simulations, we include Thomson scattering and
thermal bremsstrahlung in the opacity, focusing exclusively on the
super-Eddington regime. Unlike accretion onto bodies with solid surfaces,
super-Eddington accretion onto black holes does not produce super-Eddington
luminosity. In our examples, despite accreting at up to 300 times the Eddington
rate, our measured luminosity is always several orders of magnitude below
Eddington.
| arxiv topic:astro-ph.IM astro-ph.HE |
arxiv_dataset-33791204.5638 | Search for supersymmetry in events with three leptons and missing
transverse momentum in sqrt(s) = 7 TeV pp collisions with the ATLAS detector
hep-ex
A search for the weak production of charginos and neutralinos into final
states with three electrons or muons and missing transverse momentum is
presented. The analysis uses 2.06 fb^-1 of sqrt(s) = 7 TeV proton-proton
collision data delivered by the Large Hadron Collider and recorded with the
ATLAS detector. Observations are consistent with standard model expectations in
two signal regions that are either depleted or enriched in Z-boson decays.
Upper limits at 95% confidence level are set in R-parity conserving
phenomenological minimal supersymmetric and simplified models. For the
simplified models, degenerate lightest chargino and next-to-lightest neutralino
masses up to 300 GeV are excluded for mass differences from the lightest
neutralino up to 300 GeV.
| arxiv topic:hep-ex |
arxiv_dataset-33801204.5738 | Thermodynamics of ultrasmall metallic grains in the presence of pairing
and exchange correlations: Mesoscopic fluctuations
cond-mat.mes-hall cond-mat.str-el nucl-th
We study the mesoscopic fluctuations of thermodynamic observables in a
nanosized metallic grain in which the single-particle dynamics are chaotic and
the dimensionless Thouless conductance is large. Such a grain is modeled by the
universal Hamiltonian describing the competition between exchange and pairing
correlations. The exchange term is taken into account exactly by a
spin-projection method, and the pairing term is treated in the static-path
approximation together with small-amplitude quantal fluctuations around each
static fluctuation of the pairing field. Odd-even particle-number effects
induced by pairing correlations are included using a number-parity projection.
We find that the exchange interaction shifts the number-parity effects in the
heat capacity and spin susceptibility to lower temperatures. In the regime
where the pairing gap is similar to or smaller than the single-particle mean
level spacing, these number-parity effects are suppressed by exchange
correlations, and the fluctuations of the spin susceptibility may be
particularly large. However, for larger values of the pairing gap, the
number-parity effects may be enhanced by exchange correlations.
| arxiv topic:cond-mat.mes-hall cond-mat.str-el nucl-th |
arxiv_dataset-33811204.5838 | Curvature Properties of Two Naveira Classes of Riemannian Product
Manifolds
math.DG
The main aim of the present work is to obtain some curvature properties of
the manifolds from two classes of Riemannian product manifolds. These classes
are two basic classes from Naveira classification of Riemannian almost product
manifolds.
| arxiv topic:math.DG |
arxiv_dataset-33821204.5938 | Exact solutions of a Flat Full Causal Bulk viscous FRW cosmological
model through factorization
gr-qc
We study the classical flat full causal bulk viscous FRW cosmological model
through the factorization method. The method shows that there exists a
relationship between the viscosity parameter $s$ and the parameter $\gamma$
entering the equations of state of the model. Also, the factorization method
allows to find some new exact parametric solutions for different values of the
viscous parameter $s$. Special attention is given to the well known case
$s=1/2$, for which the cosmological model admits scaling symmetries.
Furthermore, some exact parametric solutions for $s=1/2$ are obtained through
the Lie group method.
| arxiv topic:gr-qc |
arxiv_dataset-33831204.6038 | Displaced Supersymmetry
hep-ph hep-ex
The apparent absence of light superpartners at the LHC strongly constrains
the viability of the MSSM as a solution to the hierarchy problem. These
constraints can be significantly alleviated by R-parity violation (RPV).
Bilinear R-parity violation, with the single operator L H_u, does not require
any special flavor structure and can be naturally embedded in a GUT while
avoiding constraints from proton decay (unlike baryon-number-violating RPV).
The LSP in this scenario can be naturally long-lived, giving rise to displaced
vertices. Many collider searches, particularly those selecting b-jets or
leptons, are insensitive to events with such detector-scale displaced decays
owing to cuts on track quality and impact parameter. We demonstrate that for
decay lengths in the window ~1-1000 mm, constraints on superpartner masses can
be as low as ~450 GeV for squarks and ~40 GeV for LSPs. In some parts of
parameter space light LSPs can dominate the Higgs decay width, hiding the Higgs
from existing searches. This framework motivates collider searches for
detector-scale displaced vertices. LHCb may be ideally suited to trigger on
such events, while ATLAS and CMS may need to trigger on missing energy in the
event.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-33841204.6138 | Structural recovery of ion implanted ZnO nanowires
cond-mat.mtrl-sci
Ion implantation is an interesting method to dope semiconducting materials
such as zinc oxide provided that the implantation-induced defects can be
subsequently removed. Nitrogen implantation followed by anneals under O2 were
carried out on zinc oxide nanowires in the same conditions as in a previous
study on bulk ZnO [J. Appl.Phys. 109, 023513 (2011)], allowing a direct
comparison of the defect recovery mechanisms. Transmission electron microscopy
and cathodoluminescence were carried out to assess the effects of nitrogen
implantation and of subsequent anneals on the structural and optical properties
of ZnO nanowires. Defect recovery is shown to be more effective in nanowires
compared with bulk material due to the proximity of free surfaces.
Nevertheless, the optical emission of implanted and annealed nanowires
deteriorated compared to as-grown nanowires, as also observed for unimplanted
and annealed nanowires. This is tentatively attributed to the dissociation of
excitons in the space charge region induced by O2 adsorption on the nanowire
surface.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-33851204.6238 | Decoherence in Quantum Markov Chains
quant-ph
It is known that under some assumptions the hitting time in quantum Markov
chains is quadratically smaller than the hitting time in classical Markov
chains. This work extends this result for decoherent quantum Markov chains. The
decoherence is introduced using a percolation-like graph model, which allows us
to define a decoherent quantum hitting time and to establish a
decoherent-intensity range for which the decoherent quantum hitting time is
quadratically smaller than the the classical hitting time. The detection
problem under decoherence is also solved with quadratic speedup in this range.
| arxiv topic:quant-ph |
arxiv_dataset-33861204.6338 | Transition probability of perturbative form for nu_mu -> nu_e
oscillations in matter of constant density
hep-ph
We give a convenient expression for the appearance probability P(nu_mu ->
nu_e) describing neutrino oscillations in matter of constant density, derived
using textbook quantum mechanics stratagems. Our formulation retains the
clarity of an expansion in alpha = Delta m_{21}^2/Delta m_{31}^2 exhibited by
the popular Cervera et al. formula [Nucl. Phys. B 579, 17 (2000)] while
enabling more accurate evaluation of oscillations over terrestrial baselines.
| arxiv topic:hep-ph |
arxiv_dataset-33871204.6438 | Geometry of non-holonomic diffusion
math-ph math.MP
We study stochastically perturbed non-holonomic systems from a geometric
point of view. In this setting, it turns out that the probabilistic properties
of the perturbed system are intimately linked to the geometry of the constraint
distribution. For $G$-Chaplygin systems, this yields a stochastic criterion for
the existence of a smooth preserved measure. As an application of our results
we consider the motion planning problem for the noisy two-wheeled robot and the
noisy snakeboard.
| arxiv topic:math-ph math.MP |
arxiv_dataset-33881204.6538 | Biomolecular events in cancer revealed by attractor metagenes
q-bio.QM q-bio.MN
Mining gene expression profiles has proven valuable for identifying
metagenes, defined as linear combinations of individual genes, serving as
surrogates of biological phenotypes. Typically, such metagenes are jointly
generated as the result of an optimization process for dimensionality
reduction. Here we present an unconstrained method for individually generating
metagenes that can point to the core of the underlying biological mechanisms.
We use an iterative process that starts from any seed gene and converges to one
of several precise attractor metagenes representing biomolecular events, such
as cell transdifferentiation or the presence of an amplicon. By analyzing six
rich gene expression datasets from three different cancer types, we identified
many such biomolecular events, some of which are present in all tested cancer
types. We focus on several such events including a stage-associated mesenchymal
transition and a grade-associated mitotic chromosomal instability.
| arxiv topic:q-bio.QM q-bio.MN |
arxiv_dataset-33891204.6638 | Modelling the emergence of spatial patterns of economic activity
cs.MA cs.SI physics.soc-ph q-fin.GN
Understanding how spatial configurations of economic activity emerge is
important when formulating spatial planning and economic policy. A simple model
was proposed by Simon, who assumed that firms grow at a rate proportional to
their size, and that new divisions of firms with certain probabilities relocate
to other firms or to new centres of economic activity. Simon's model produces
realistic results in the sense that the sizes of economic centres follow a Zipf
distribution, which is also observed in reality. It lacks realism in the sense
that mechanisms such as cluster formation, congestion (defined as an overly
high density of the same activities) and dependence on the spatial distribution
of external parties (clients, labour markets) are ignored.
The present paper proposed an extension of the Simon model that includes both
centripetal and centrifugal forces. Centripetal forces are included in the
sense that firm divisions are more likely to settle in locations that offer a
higher accessibility to other firms. Centrifugal forces are represented by an
aversion of a too high density of activities in the potential location. The
model is implemented as an agent-based simulation model in a simplified spatial
setting. By running both the Simon model and the extended model, comparisons
are made with respect to their effects on spatial configurations. To this end a
series of metrics are used, including the rank-size distribution and indices of
the degree of clustering and concentration.
| arxiv topic:cs.MA cs.SI physics.soc-ph q-fin.GN |
arxiv_dataset-33901204.6738 | In defence of non-ontic accounts of quantum states
quant-ph physics.hist-ph
The paper discusses objections against non-hidden variable versions of the
epistemic conception of quantum states - the view that quantum states do not
describe the properties of quantum systems but reflect, in some way to be
specified, the epistemic conditions of agents assigning them. In the first half
of the paper, the main motivation for the epistemic conception of quantum
states is sketched, and a version of it is outlined, which combines ideas from
an earlier study of it [Friederich 2011] with elements of Richard Healey's
recent pragmatist interpretation of quantum theory [Healey 2012]. In the second
half, various objections against epistemic accounts of quantum states are
discussed in detail, which are based on criticisms found in the literature.
Possible answers by the version outlined here are compared with answers from
the quantum Bayesian point of view, which is at present the most discussed
version of the epistemic conception of quantum states.
| arxiv topic:quant-ph physics.hist-ph |
arxiv_dataset-33911205.0099 | Bayesian approach to electron correlation in density functional theory
physics.chem-ph quant-ph
In the present communication the Bayesian conditional probability approach is
applied to the wave function of a many-electron system that results in
appearance of a quantum vector potential in the DFT Schrodinger equation due to
electron correlation, apart from the correlation energy term. Mathematically,
the effect of this vector potential is equivalent to a magnetic field that
corresponds in particular to a conservative irrotational one if it is
considered in connection with the correlation potential. An analysis of the
effect of the correlation momentum on the electronic transitions suggested that
the electron correlation increases the transition probability.
| arxiv topic:physics.chem-ph quant-ph |
arxiv_dataset-33921205.0199 | Adhesion mechanics of graphene membranes
cond-mat.mtrl-sci cond-mat.mes-hall
The interaction of graphene with neighboring materials and structures plays
an important role in its behavior, both scientifically and technologically. The
interactions are complicated due to the interplay between surface forces and
possibly nonlinear elastic behavior. Here we review recent experimental and
theoretical advances in the understanding of graphene adhesion. We organize our
discussion into experimental and theoretical efforts directed toward: graphene
conformation to a substrate, determination of adhesion energy, and applications
where graphene adhesion plays an important role. We conclude with a brief
prospectus outlining open issues.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall |
arxiv_dataset-33931205.0299 | Electroweak two-loop corrections to sin^2{\theta}(eff,bb) and R(b) using
numerical Mellin-Barnes integrals
hep-ph
Multi-loop integrals can be evaluated numerically using Mellin-Barnes
representations. Here this technique is applied to the calculation of
electroweak two-loop correction with closed fermion loops for two observables:
the effective weak mixing angle for bottom quarks, sin^2{\theta}(eff,bb), and
the branching ratio of the Z boson into bottom quarks, R(b). Good agreement
with a previous result for sin^2{\theta}(eff,bb) is found. The result for R(b)
is new, and a simple parametrization formula is provided which approximates the
full result within integration errors.
| arxiv topic:hep-ph |
arxiv_dataset-33941205.0399 | 10 pc Scale Circumnuclear Molecular Gas Imaging of Nearby AGNs
astro-ph.CO astro-ph.GA
We present the images and kinematics of circumnuclear molecular gas from 100
pc scale down to 10 pc scale in nearby active galactic nuclei (AGNs) using the
Submillimeter Array (SMA) and the Plateau de Bure Interferometer (PdBI). We
have observed several nearby galaxies that host AGNs, such as the nearest radio
galaxy Centaurus A (NGC 5128), the Seyfert 2 galaxy M51 (NGC 5194), the Seyfert
2 galaxy NGC 1068, the Seyfert 1 galaxy NGC 1097, and the Seyfert 2 / starburst
composite galaxy NGC 4945, in CO lines to see whether the molecular gas
distribution, kinematics, and physical conditions at 10 - 100 pc scale follows
the AGN unified model or not. In 100 pc scale, most of the circumnuclear
molecular gas shows smooth velocity gradient, suggesting a regular rotating
feature, and also shows abnormal line ratios, suggesting the existence of
active sources to make the circumnuclear molecular gas dense and/or warm
conditions or abnormal chemical compositions. In 10 pc scale, on the other
hand, the molecular gas kinematics shows various characteristics, some shows
very disturbed kinematics such as a jet-entrained feature in the galaxies that
have jets, but some still shows regular rotation feature in a galaxy that does
not have obvious jets. These results indicate that the kinematics and
physical/chemical conditions of the circumnuclear molecular gas at the scale
less than 100 pc is highly affected by the AGN activities, and at this scale,
there is no clear evidence of any unified feature seen in the circumnuclear
molecular gas.
| arxiv topic:astro-ph.CO astro-ph.GA |
arxiv_dataset-33951205.0499 | On automating Markov chain Monte Carlo for a class of spatial models
stat.CO
Markov chain Monte Carlo (MCMC) algorithms provide a very general recipe for
estimating properties of complicated distributions. While their use has become
commonplace and there is a large literature on MCMC theory and practice, MCMC
users still have to contend with several challenges with each implementation of
the algorithm. These challenges include determining how to construct an
efficient algorithm, finding reasonable starting values, deciding whether the
sample-based estimates are accurate, and determining an appropriate length
(stopping rule) for the Markov chain. We describe an approach for resolving
these issues in a theoretically sound fashion in the context of spatial
generalized linear models, an important class of models that result in
challenging posterior distributions. Our approach combines analytical
approximations for constructing provably fast mixing MCMC algorithms, and takes
advantage of recent developments in MCMC theory. We apply our methods to real
data examples, and find that our MCMC algorithm is automated and efficient.
Furthermore, since starting values, rigorous error estimates and theoretically
justified stopping rules for the sampling algorithm are all easily obtained for
our examples, our MCMC-based estimation is practically as easy to perform as
Monte Carlo estimation based on independent and identically distributed draws.
| arxiv topic:stat.CO |
arxiv_dataset-33961205.0599 | The truncated disk from Suzaku data of GX 339-4 in the extreme very high
state
astro-ph.HE
We report on the geometry of accretion disk and high energy coronae in the
strong Comptonization state (the very high/steep power law/hard intermediate
state) based on a Suzaku observation of the famous Galactic black hole GX
339-4. These data were taken just before the peak of the 2006-2007 outburst,
and the average X-ray luminosity in the 0.7-200 keV band is estimated to be
2.9E38 erg/s for a distance of 8 kpc. We fit the spectrum with both simple
(independent disk and corona) and sophisticated (energetically coupled disk and
corona) models, but all fits imply that the underlying optically thick disk is
truncated significantly before the innermost stable circular orbit around the
black hole. We show this directly by a comparison with similarly broadband data
from a disk dominated spectrum at almost the same luminosity observed by
XMM-Newton and RXTE 3 days after the Suzaku observation.
During the Suzaku observation, the QPO frequency changes from 4.3 Hz to 5.5
Hz, while the spectrum softens. The energetically coupled model gives a
corresponding 5+/- 8 % decrease in derived inner radius of the disk. While this
is not significant, it is consistent with the predicted change in QPO frequency
from Lense-Thirring precession of the hot flow interior to the disk and/or a
deformation mode of this flow, as a higher QPO frequency implies a smaller size
scale for the corona. This is consistent with the truncated disk extending
further inwards towards the black hole.
| arxiv topic:astro-ph.HE |
arxiv_dataset-33971205.0699 | Time-Varying Space-Only Codes for Coded MIMO
cs.IT math.IT
Multiple antenna (MIMO) devices are widely used to increase reliability and
information bit rate. Optimal error rate performance (full diversity and large
coding gain), for unknown channel state information at the transmitter and for
maximal rate, can be achieved by approximately universal space-time codes, but
comes at a price of large detection complexity, infeasible for most practical
systems. We propose a new coded modulation paradigm: error-correction outer
code with space-only but time-varying precoder (as inner code). We refer to the
latter as Ergodic Mutual Information (EMI) code. The EMI code achieves the
maximal multiplexing gain and full diversity is proved in terms of the outage
probability. Contrary to most of the literature, our work is not based on the
elegant but difficult classical algebraic MIMO theory. Instead, the relation
between MIMO and parallel channels is exploited. The theoretical proof of full
diversity is corroborated by means of numerical simulations for many MIMO
scenarios, in terms of outage probability and word error rate of LDPC coded
systems. The full-diversity and full-rate at low detection complexity comes at
a price of a small coding gain loss for outer coding rates close to one, but
this loss vanishes with decreasing coding rate.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-33981205.0799 | Hochschild cohomology of the cluster-tilted algebras of finite
representation type
math.RT
We compute the Hochschild cohomology groups of the cluster-tilted algebras of
finite representation type.
| arxiv topic:math.RT |
arxiv_dataset-33991205.0899 | Compact Boson Stars
gr-qc
We consider compact boson stars that arise for a V-shaped scalar field
potential. They represent a one parameter family of solutions of the scaled
Einstein-signum-Gordon equations. We analyze the physical properties of these
solutions and determine their domain of existence. Along their physically
relevant branch emerging from the compact Q-ball solution, their mass increases
with increasing radius. Empoying arguments from catastrophe theory we argue
that this branch is stable, until the maximal value of the mass is reached.
There the mass and size are on the order of magnitude of the Schwarzschild
limit, and thus the spiralling respectively oscillating behaviour, well-known
for compact stars, sets in.
| arxiv topic:gr-qc |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.