Statistical Mechanics
Non-Markovian Effects on Overdamped Systems (1902.01356v1)
Eduardo dos S. Nascimento, Welles A. M. Morgado
2019-02-04
We study the consequences of adopting the memory dependent, non-Markovian, physics with the memory-less over-damped approximation usually employed to investigate Brownian particles. Due to the finite correlation time scale associated with the noise, the stationary behavior of the system is not described by the Boltzmann-Gibbs statistics. However, the presence of a very weak external white noise can be used to regularize the equilibrium properties. Surprisingly, the coupling to another bath effectively restores the dynamical aspects missed by the over-damped treatment.
On the size of the space spanned by a nonequilibrium state in a quantum spin lattice system (1901.10797v2)
Maurizio Fagotti
2019-01-30
We consider the time evolution of a state in an isolated quantum spin lattice system with energy cumulants proportional to the number of the sites
. We compute the distribution of the eigenvalues of the time averaged state over a time window
in the limit of large
. This allows us to infer the size of a subspace that captures time evolution in
. We estimate the size to be
, where
is the energy variance per site, and
is the inverse error function.
An introduction to classical molecular dynamics simulation for experimental scattering users (1902.01324v1)
Andrew R. McCluskey, James Grant, Adam R. Symington, Tim Snow, James Doutch, Benjamin J. Morgan, Stephen C. Parker, Karen J. Edler
2019-02-04
Classical molecular dynamics simulations are a common component of multi-modal analyses from scattering measurements, such as small-angle scattering and diffraction. Users of these experimental techniques often have no formal training in the theory and practice of molecular dynamics simulation, leading to the possibility of these simulations being treated as a "black box" analysis technique. In this article, we describe an open educational resource (OER) designed to introduce classical molecular dynamics to users of scattering methods. This resource is available as a series of interactive web pages, which can be easily accessed by students, and as an open source software repository, which can be freely copied, modified, and redistributed by educators. The topic covered in this OER includes classical atomistic modelling, parameterising interatomic potentials, molecular dynamics simulations, typical sources of error, and some of the approaches to using simulations in the analysis of scattering data.
Phase Diagram and Conformal String Excitations of Square Ice using Gauge Invariant Matrix Product States (1807.00826v2)
Ferdinand Tschirsich, Simone Montangero, Marcello Dalmonte
2018-07-02
We investigate the ground state phase diagram of square ice -- a U(1) lattice gauge theory in two spatial dimensions -- using gauge invariant tensor network techniques. By correlation function, Wilson loop, and entanglement diagnostics, we characterize its phases and the transitions between them, finding good agreement with previous studies. We study the entanglement properties of string excitations on top of the ground state, and provide direct evidence of the fact that the latter are described by a conformal field theory. Our results pave the way to the application of tensor network methods to confining, two-dimensional lattice gauge theories, to investigate their phase diagrams and low-lying excitations.
Magnetic phase separation in a frustrated ferrimagnetic chain under a magnetic field (1902.01292v1)
A. M. do Nascimento-Junior, R. R. Montenegro-Filho
2019-02-04
We use density matrix renormalization group to study the first-order quantum phase transition induced by a magnetic field
in a frustrated ferrimagnetic chain. The magnetization (
) curve as a function of
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