4,552 research outputs found
Stochastic Wave-Function Simulation of Irreversible Emission Processes for Open Quantum Systems in a Non-Markovian Environment
When conducting the numerical simulation of quantum transport, the main
obstacle is a rapid growth of the dimension of entangled Hilbert subspace. The
Quantum Monte Carlo simulation techniques, while being capable of treating the
problems of high dimension, are hindered by the so-called "sign problem". In
the quantum transport, we have fundamental asymmetry between the processes of
emission and absorption of environment excitations: the emitted excitations are
rapidly and irreversibly scattered away. Whereas only a small part of these
excitations is absorbed back by the open subsystem, thus exercising the
non-Markovian self-action of the subsystem onto itself. We were able to devise
a method for the exact simulation of the dominant quantum emission processes,
while taking into account the small backaction effects in an approximate
self-consistent way. Such an approach allows us to efficiently conduct
simulations of real-time dynamics of small quantum subsystems immersed in
non-Markovian bath for large times, reaching the quasistationary regime. As an
example we calculate the spatial quench dynamics of Kondo cloud for a bozonized
Kodno impurity model.Comment: 7 pages, 3 figures, ICQT2017 Conference Proceedings; corrected a few
typos; accepted for publication in the AIP Conference Proceedings journa
Confinement in N=1 SQCD: One Step Beyond Seiberg's Duality
We consider N=1 supersymmetric quantum chromodynamics (SQCD) with the gauge
group U(N_c) and N_c+N quark flavors. N_c flavors are massless; the
corresponding squark fields develop (small) vacuum expectation values (VEVs) on
the Higgs branch. Extra N flavors are endowed with small (and equal) mass
terms. We study this theory through its Seiberg's dual: U(N) gauge theory with
N_c +N flavors of "dual quark" fields plus a gauge-singlet mesonic field M. The
original theory is referred to as "quark theory" while the dual one is termed
"monopole theory." The suggested mild deformation of Seiberg's procedure
changes the dynamical regime of the monopole theory from infrared free to
asymptotically free at large distances. We show that, upon condensation of the
"dual quarks," the dual theory supports non-Abelian flux tubes (strings).
Seiberg's duality is extended beyond purely massless states to include light
states on both sides. Being interpreted in terms of the quark theory, the
monopole-theory flux tubes are supposed to carry chromoelectric fields. The
string junctions -- confined monopole-theory monopoles -- can be viewed as
"constituent quarks" of the original quark theory. We interpret closed strings
as glueballs of the original quark theory. Moreover, there are string
configurations formed by two junctions connected by a pair of different
non-Abelian strings. These can be considered as constituent quark mesons of the
quark theory.Comment: 30 pages, 3 figures; v2 a reference added, minor comments added;
final version to be published in PR
Supersymmetric Quantum Chromodynamics: How Confined Non-Abelian Monopoles Emerge from Quark Condensation
We consider N =1 supersymmetric QCD with the gauge group U(N) and N_f=N quark
flavors. To get rid of flat directions we add a meson superfield. The theory
has no adjoint fields and, therefore, no 't Hooft-Polyakov monopoles in the
quasiclassical limit. We observe a non-Abelian Meissner effect: condensation of
color charges (squarks) gives rise to confined monopoles. The very fact of
their existence in N =1 supersymmetric QCD without adjoint scalars was not
known previously. Our analysis is analytic and is based on the fact that the N
=1 theory under consideration can be obtained starting from N =2 SQCD in which
the 't Hooft-Polyakov monopoles do exist, through a certain limiting procedure
allowing us to track the status of these monopoles at various stages. Monopoles
are confined by BPS non-Abelian strings (flux tubes). Dynamics of string
orientational zero modes are described by supersymmetric CP(N-1) sigma model on
the string world sheet. If a dual of N =1 SQCD with the gauge group U(N) and
N_f=N quark flavors could be identified, in this dual theory our demonstration
would be equivalent to the proof of the non-Abelian dual Meissner effect.Comment: 33 pages, 3 figures. V2 reference and a brief comment added; typos
corrected. V3 two comments added; final version accepted for publication to
PR
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