1,066,269 research outputs found
Nonperturbative Renormalisation Group: Applications to the few and many-body systems
We consider the applications of functional renormalisation group to few and
many-body systems. As an application to the few-body dynamics we study the
ratio between the fermion-fermion scattering length and the dimer-dimer
scattering length for systems of few nonrelativistic fermions.
We find a strong dependence on the cutoff function used in the
renormalisation flow for a two-body truncation of the action. Adding a simple
three-body term substantially reduces this dependence. In the context of
many-body physics we study the dynamics of both symmetric and asymmetric
many-fermion systems using the same functional renormalisation technique. It is
demonstrated that functional renormalisation group gives sensible and reliable
results and provides a solid theoretical ground for the future studies. Open
questions as well as lines of further developments are discussed.Comment: Talk on International IUPAP Conference on Few-Body Problems in
Physics, September, 2009, Bonn, German
Two Measures of Dependence
Two families of dependence measures between random variables are introduced.
They are based on the R\'enyi divergence of order and the relative
-entropy, respectively, and both dependence measures reduce to
Shannon's mutual information when their order is one. The first
measure shares many properties with the mutual information, including the
data-processing inequality, and can be related to the optimal error exponents
in composite hypothesis testing. The second measure does not satisfy the
data-processing inequality, but appears naturally in the context of distributed
task encoding.Comment: 40 pages; 1 figure; published in Entrop
Crossover between strong and weak measurement in interacting many-body systems
Measurements with variable system-detector interaction strength, ranging from
weak to strong, have been recently reported in a number of electronic
nanosystems. In several such instances many-body effects play a significant
role. Here we consider the weak--to--strong crossover for a setup consisting of
an electronic Mach-Zehnder interferometer, where a second interferometer is
employed as a detector. In the context of a conditional which-path protocol, we
define a generalized conditional value (GCV), and determine its full crossover
between the regimes of weak and strong (projective) measurement. We find that
the GCV has an oscillatory dependence on the system-detector interaction
strength. These oscillations are a genuine many-body effect, and can be
experimentally observed through the voltage dependence of cross current
correlations.Comment: 5 pages, 3 figures, and appendices (9 pages, 3 figures, 2 tables
Momentum distribution dynamics of a Tonks-Girardeau gas: Bragg reflections of a quantum many-body wavepacket
The dynamics of the momentum distribution and the reduced single-particle
density matrix (RSPDM) of a Tonks-Girardeau (TG) gas is studied in the context
of Bragg-reflections of a many-body wavepacket. We find strong suppression of a
Bragg-reflection peak for a dense TG wavepacket; our observation illustrates
dependence of the momentum distribution on the interactions/wavefunction
symmetry. The momentum distribution is calculated with a fast algorithm based
on a formula expressing the RSPDM via a dynamically evolving single-particle
basis
Copula-Based Dependence Characterizations and Modeling for Time Series
This paper develops a new unified approach to copula-based modeling and characterizations for time series and stochastic processes. We obtain complete characterizations of many time series dependence structures in terms of copulas corresponding to their finite-dimensional distributions. In particular, we focus on copula- based representations for Markov chains of arbitrary order, m-dependent and r-independent time series as well as martingales and conditionally symmetric processes. Our results provide new methods for modeling time series that have prescribed dependence structures such as, for instance, higher order Markov processes as well as non-Markovian processes that nevertheless satisfy Chapman-Kolmogorov stochastic equations. We also focus on the construction and analysis of new classes of copulas that have flexibility to combine many different dependence properties for time series. Among other results, we present a study of new classes of cop- ulas based on expansions by linear functions (Eyraud-Farlie-Gumbel-Mongenstern copulas), power functions (power copulas) and Fourier polynomials (Fourier copulas) and introduce methods for modeling time series using these classes of dependence functions. We also focus on the study of weak convergence of empirical copula processes in the time series context and obtain new results on asymptotic gaussianity of such processes for a wide class of beta mixing sequences.
Exploring cultural factors in human-robot interaction: A matter of personality?
This paper proposes an experimental study to investigate task-dependence and cultural-background dependence of the personality trait attribution on humanoid robots. In Human-Robot Interaction, as well as in Human-Agent Interaction research, the attribution of personality traits towards intelligent agents has already been researched intensively in terms of the social similarity or complementary rule. These two rules imply that humans either tend to like others with similar personality traits or complementary personality traits more. Even though state of the art literature suggests that similarity attraction happens for virtual agents, and complementary attraction for robots, there are many contradictions in the findings. We assume that searching the explanation for personality trait attribution in the similarity and complementary rule does not take into account important contextual factors. Just like people equate certain personality types to certain professions, we expect that people may have certain personality expectations depending on the context of the task the robot carries out. Because professions have different social meaning in different national culture, we also expect that these task-dependent personality preferences differ across cultures. Therefore suggest an experiment that considers the task-context and the cultural background of users
A light-front coupled-cluster method for the nonperturbative solution of quantum field theories
We propose a new method for the nonperturbative solution of quantum field
theories and illustrate its use in the context of a light-front analog to the
Greenberg--Schweber model. The method is based on light-front quantization and
uses the exponential-operator technique of the many-body coupled-cluster
method. The formulation produces an effective Hamiltonian eigenvalue problem in
the valence Fock sector of the system of interest, combined with nonlinear
integral equations to be solved for the functions that define the effective
Hamiltonian. The method avoids the Fock-space truncations usually used in
nonperturbative light-front Hamiltonian methods and, therefore, does not suffer
from the spectator dependence, Fock-sector dependence, and uncanceled
divergences caused by such truncations.Comment: 11 pages, 4 figures, RevTeX 4.1; expanded description of method and
replaced QED with simpler model for illustratio
- …