1,160 research outputs found
Identity of the imaginary-time and real-time thermal propagators for scalar bound states in a one-generation Nambu-Jona-Lasinio model
By rigorous reanalysis of the results, we have proven that the propagators at
finite temperature for scalar bound states in one-generation fermion condensate
scheme of electroweak symmetry breaking are in fact identical in the
imaginary-time and the real-time formalism. This dismisses the doubt about
possible discrepancy between the two formalisms in this problem. Identity of
the derived thermal transformation matrices of the real-time matrix propagators
for scalar bound states without and with chemical potential and the ones for
corresponding elementary scalar particles shows similarity of thermodynamic
property between the two types of particles. Only one former inference is
modified, i.e. when the two flavors of fermions have unequal nonzero masses,
the amplitude of the composite Higgs particle will decay instead grow in time.Comment: 5 pages, revtex4, no figure
Signatures of modulated pair interaction in cuprate superconductors
Recent low-temperature scanning tunnelling spectroscopy experiments on the
surface of BSCCO-2212 have revealed a strong positive correlation between the
position of localized resonances at -960 meV identified with interstitial
oxygen dopants and the size of the local spectral gap. We review efforts to
understand these correlations within a model where the dopants modulate the
pair interaction on an atomic scale. We provide further evidence for this model
by comparing the correlations between the dopants and the local density of
states with experimental results.Comment: 4 pages, 2 figures, submitted to M2S-HTSC VIII, Dresden 200
Structural Routability of n-Pairs Information Networks
Information does not generally behave like a conservative fluid flow in
communication networks with multiple sources and sinks. However, it is often
conceptually and practically useful to be able to associate separate data
streams with each source-sink pair, with only routing and no coding performed
at the network nodes. This raises the question of whether there is a nontrivial
class of network topologies for which achievability is always equivalent to
routability, for any combination of source signals and positive channel
capacities. This chapter considers possibly cyclic, directed, errorless
networks with n source-sink pairs and mutually independent source signals. The
concept of downward dominance is introduced and it is shown that, if the
network topology is downward dominated, then the achievability of a given
combination of source signals and channel capacities implies the existence of a
feasible multicommodity flow.Comment: The final publication is available at link.springer.com
http://link.springer.com/chapter/10.1007/978-3-319-02150-8_
The hodograph method applicability in the problem of long-scale nonlinear dynamics of a thin vortex filament near a flat boundary
Hamiltonian dynamics of a thin vortex filament in ideal incompressible fluid
near a flat fixed boundary is considered at the conditions that at any point of
the curve determining shape of the filament the angle between tangent vector
and the boundary plane is small, also the distance from a point on the curve to
the plane is small in comparison with the curvature radius. The dynamics is
shown to be effectively described by a nonlinear system of two
(1+1)-dimensional partial differential equations. The hodograph transformation
reduces that system to a single linear differential equation of the second
order with separable variables. Simple solutions of the linear equation are
investigated at real values of spectral parameter when the filament
projection on the boundary plane has shape of a two-branch spiral or a smoothed
angle, depending on the sign of .Comment: 9 pages, revtex4, 6 eps-figure
A Generalized Fluctuation-Dissipation Theorem for Nonlinear Response Functions
A nonlinear generalization of the Fluctuation-Dissipation Theorem (FDT) for
the n-point Green functions and the amputated 1PI vertex functions at finite
temperature is derived in the framework of the Closed Time Path formalism. We
verify that this generalized FDT coincides with known results for n=2 and 3.
New explicit relations among the 4-point nonlinear response and correlation
(fluctuation) functions are presented.Comment: 34 pages, Revte
Bloggers Behavior and Emergent Communities in Blog Space
Interactions between users in cyberspace may lead to phenomena different from
those observed in common social networks. Here we analyse large data sets about
users and Blogs which they write and comment, mapped onto a bipartite graph. In
such enlarged Blog space we trace user activity over time, which results in
robust temporal patterns of user--Blog behavior and the emergence of
communities. With the spectral methods applied to the projection on weighted
user network we detect clusters of users related to their common interests and
habits. Our results suggest that different mechanisms may play the role in the
case of very popular Blogs. Our analysis makes a suitable basis for theoretical
modeling of the evolution of cyber communities and for practical study of the
data, in particular for an efficient search of interesting Blog clusters and
further retrieval of their contents by text analysis
An adaptive multi-population differential artificial bee colony algorithm for many-objective service composition in cloud manufacturing
Several conflicting criteria must be optimized simultaneously during the service composition and optimal selection (SCOS) in cloud manufacturing, among which tradeoff optimization regarding the quality of the composite services is a key issue in successful implementation of manufacturing tasks. This study improves the artificial bee colony (ABC) algorithm by introducing a synergetic mechanism for food source perturbation, a new diversity maintenance strategy, and a novel computing resources allocation scheme to handle complicated many-objective SCOS problems. Specifically, differential evolution (DE) operators with distinct search behaviors are integrated into the ABC updating equation to enhance the level of information exchange between the foraging bees, and the control parameters for reproduction operators are adapted independently. Meanwhile, a scalarization based approach with active diversity promotion is used to enhance the selection pressure. In this proposal, multiple size adjustable subpopulations evolve with distinct reproduction operators according to the utility of the generating offspring so that more computational resources will be allocated to the better performing reproduction operators. Experiments for addressing benchmark test instances and SCOS problems indicate that the proposed algorithm has a competitive performance and scalability behavior compared with contesting algorithms
Infrared Behaviour of The Gluon Propagator in Non-Equilibrium Situations
The infrared behaviour of the medium modified gluon propagator in
non-equilibrium situations is studied in the covariant gauge using the
Schwinger-Keldysh closed-time path formalism. It is shown that the magnetic
screening mass is non-zero at the one loop level whenever the initial gluon
distribution function is non isotropic with the assumption that the
distribution function of the gluon is not divergent at zero transverse
momentum. For isotropic gluon distribution functions, such as those describing
local equilibrium, the magnetic mass at one loop level is zero which is
consistent with finite temperature field theory results. Assuming that a
reasonable initial gluon distribution function can be obtained from a
perturbative QCD calculation of minijets, we determine these out of equilibrium
values for the initial magnetic and Debye screening masses at energy densities
appropriate to RHIC and LHC. We also compare the magnetic masses obtained here
with those obtained using finite temperature lattice QCD methods at similar
temperatures at RHIC and LHC.Comment: 21 pages latex, 4 figures, final version to be published in Phys.
Rev.
Spin symmetry in Dirac negative energy spectrum in density-dependent relativistic Hartree-Fock theory
The spin symmetry in the Dirac negative energy spectrum and its origin are
investigated for the first time within the density-dependent relativistic
Hartree-Fock (DDRHF) theory. Taking the nucleus O as an example, the
spin symmetry in the negative energy spectrum is found to be a good
approximation and the dominant components of the Dirac wave functions for the
spin doublets are nearly identical. In comparison with the relativistic Hartree
approximation where the origin of spin symmetry lies in the equality of the
scalar and vector potentials, in DDRHF the cancellation between the Hartree and
Fock terms is responsible for the better spin symmetry properties and
determines the subtle spin-orbit splitting. These conclusions hold even in the
case when significant deviations from the G-parity values of the
meson-antinucleon couplings occur.Comment: 13 pages, 7 figures, 1 table, accepted by Eur. Phys. J.
When Machine Learning Meets 2D Materials:A Review
The availability of an ever-expanding portfolio of 2D materials with rich internal degrees of freedom (spin, excitonic, valley, sublattice, and layer pseudospin) together with the unique ability to tailor heterostructures made layer by layer in a precisely chosen stacking sequence and relative crystallographic alignments, offers an unprecedented platform for realizing materials by design. However, the breadth of multi-dimensional parameter space and massive data sets involved is emblematic of complex, resource-intensive experimentation, which not only challenges the current state of the art but also renders exhaustive sampling untenable. To this end, machine learning, a very powerful data-driven approach and subset of artificial intelligence, is a potential game-changer, enabling a cheaper – yet more efficient – alternative to traditional computational strategies. It is also a new paradigm for autonomous experimentation for accelerated discovery and machine-assisted design of functional 2D materials and heterostructures. Here, the study reviews the recent progress and challenges of such endeavors, and highlight various emerging opportunities in this frontier research area.</p
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