258 research outputs found
Constructing Auxiliary Dynamics for Nonequilibrium Stationary States by Variance Minimization
We present a strategy to construct guiding distribution functions (GDFs) based on variance minimization. Auxiliary dynamics via GDFs mitigates the exponential growth of variance as a function of bias in Monte Carlo estimators of large deviation functions. The variance minimization technique exploits the exact properties of eigenstates of the tilted operator that defines the biased dynamics in the nonequilibrium system. We demonstrate our techniques in two classes of problems. In the continuum, we show that GDFs can be optimized to study the interacting driven diffusive systems where the efficiency is systematically improved by incorporating higher correlations into the GDF. On the lattice, we use a correlator product state ansatz to study the 1D weakly asymmetric simple exclusion process. We show that with modest resources, we can capture the features of the susceptibility in large systems that mark the phase transition from uniform transport to a traveling wave state. Our work extends the repertoire of tools available to study nonequilibrium properties in realistic systems
Local Entanglement and quantum phase transition in spin models
Due to the phase interference of electromagnetic wave, one can recover the
total image of one object from a small piece of holograph, which records the
interference pattern of two laser light reflected from it. Similarly, the
quantum superposition principle allows us to derive the global phase diagram of
quantum spin models by investigating a proper local measurement. In the present
paper, we study the two-site entanglement in the antifferomagnetic spin models
with both spin-1/2 and 1. We show that its behaviors reveal some important
information on the global properties and the quantum phase transition of these
systems.Comment: 6 pages, 7 figure
Saturation effects in forward-forward dijet production in p+Pb collisions
We study saturation effects in the production of forward dijets in
proton-lead collisions at the Large Hadron Collider, using the framework of
High Energy Factorization. Such configurations, with both jets produced in the
forward direction, probe the gluon density of the lead nucleus at small
longitudinal momentum fraction, and also limit the phase space for emissions of
additional jets. We find significant suppression of the forward dijet azimuthal
correlations in proton-lead versus proton-proton collisions, which we attribute
to stronger saturation of the gluon density in the nucleus than in the proton.
In order to minimize model dependence of our predictions, we use two different
extensions of the Balitsky-Kovchegov equation for evolution of the gluon
density with sub-leading corrections.Comment: 13 pages, 4 figures; v2: added figure 4, several clarifying sentences
and a reference; version accepted by PR
Simulation of fermionic lattice models in two dimensions with Projected Entangled-Pair States: Next-nearest neighbor Hamiltonians
In a recent contribution [Phys. Rev. B 81, 165104 (2010)] fermionic Projected
Entangled-Pair States (PEPS) were used to approximate the ground state of free
and interacting spinless fermion models, as well as the - model. This
paper revisits these three models in the presence of an additional next-nearest
hopping amplitude in the Hamiltonian. First we explain how to account for
next-nearest neighbor Hamiltonian terms in the context of fermionic PEPS
algorithms based on simulating time evolution. Then we present benchmark
calculations for the three models of fermions, and compare our results against
analytical, mean-field, and variational Monte Carlo results, respectively.
Consistent with previous computations restricted to nearest-neighbor
Hamiltonians, we systematically obtain more accurate (or better converged)
results for gapped phases than for gapless ones.Comment: 10 pages, 11 figures, minor change
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