5,796 research outputs found
Dynamical properties of the Landau-Ginzburg model with long-range correlated quenched impurities
We investigate the critical dynamics of the time-dependent Landau-Ginzburg
model with non conserved n-component order parameter (Model A) in the presence
of long-range correlated quenched impurities. We use a special kind of
long-range correlations, previously introduced by Weinrib and Halperin. Using a
double expansion in \epsilon and \delta we calculate the critical exponent z up
to second order on the small parameters. We show that the quenched impurities
of this kind affect the critical dynamics already in first order of \epsilon
and \delta, leading to a relevant correction for the mean field value of the
exponent zComment: 7 pages, REVTEX, to be published in Phys. Rev.
Langevin equations with multiplicative noise: resolution of time discretization ambiguities for equilibrium systems
A Langevin equation with multiplicative noise is an equation schematically of
the form dq/dt = -F(q) + e(q) xi, where e(q) xi is Gaussian white noise whose
amplitude e(q) depends on q itself. Such equations are ambiguous, and depend on
the details of one's convention for discretizing time when solving them. I show
that these ambiguities are uniquely resolved if the system has a known
equilibrium distribution exp[-V(q)/T] and if, at some more fundamental level,
the physics of the system is reversible. I also discuss a simple example where
this happens, which is the small frequency limit of Newton's equation d^2q/dt^2
+ e^2(q) dq/dt = - grad V(q) + e^{-1}(q) xi with noise and a q-dependent
damping term. The resolution does not correspond to simply interpreting naive
continuum equations in a standard convention, such as Stratanovich or Ito. [One
application of Langevin equations with multiplicative noise is to certain
effective theories for hot, non-Abelian plasmas.]Comment: 15 pages, 2 figures [further corrections to Appendix A
Renormalizabilty of TH Heavy Quark Effective Theory
We show that the Heavy Quark Effective Theory is renormalizable
perturbatively. We also show that there exist renormalization schemes in which
the infinite quark mass limit of any QCD Green function is exactly given by the
corresponding Green function of the Heavy Quark Effective Theory. All this is
accomplished while preserving BRS invariance.Comment: LATEX/10 pages/ UAB-FT-314/ (References have been added.) figures
(PS) available on request. Unfortunately some mails asking for copies by
conventional mail were lost. Please resend request
Systems with Multiplicative Noise: Critical Behavior from KPZ Equation and Numerics
We show that certain critical exponents of systems with multiplicative noise
can be obtained from exponents of the KPZ equation. Numerical simulations in 1d
confirm this prediction, and yield other exponents of the multiplicative noise
problem. The numerics also verify an earlier prediction of the divergence of
the susceptibility over an entire range of control parameter values, and show
that the exponent governing the divergence in this range varies continuously
with control parameter.Comment: Four pages (In Revtex format) with 4 figures (in Postcript
Systematic Study of Theories with Quantum Modified Moduli
We begin the process of classifying all supersymmetric theories with quantum
modified moduli. We determine all theories based on a single SU or Sp gauge
group with quantum modified moduli. By flowing among theories we have
calculated the precise modifications to the algebraic constraints that
determine the moduli at the quantum level. We find a class of theories, those
with a classical constraint that is covariant but not invariant under global
symmetries, that have a singular modification to the moduli, which consists of
a new branch.Comment: 21 pages, ReVTeX (or Latex, etc), corrected typos and cQMM discusio
Leveraging Tax Time to Build Financial Capability: Research Evidence and Policy Directions
Over the past decade, a variety of initiatives have been implemented in the United States to facilitate saving and build financial security at tax time, including national experiments, pilot programs, and federal and state policies. Much progress has been made in encouraging tax filers, especially low- to moderate-income (LMI) tax filers, to save a portion of their refund. To expand upon the “golden moment” of saving at tax time, policymakers, practitioners, and researchers must now seek ways in which the lump sum of saving at tax time can serve to render tax filers capable of confidently managing their financial lives. During the 2016 tax season, thought leaders from government, policy, practice, foundations, and academia reviewed the latest research findings and discussed future possibilities of using tax time to catalyze household financial capability. The goal of the symposium was to provide opportunities for discovery and discussion across disciplines about ways LMI households can contribute to their economic security before, during, and after they file their taxes
Sum of exit times in series of metastable states in probabilistic cellular automata
Reversible Probabilistic Cellular Automata are a special class
of automata whose stationary behavior is described by Gibbs--like
measures. For those models the dynamics can be trapped for a very
long time in states which are very different from the ones typical
of stationarity.
This phenomenon can be recasted in the framework of metastability
theory which is typical of Statistical Mechanics.
In this paper we consider a model presenting two not degenerate in
energy
metastable states which form a series, in the sense that,
when the dynamics is started at one of them, before reaching
stationarity, the system must necessarily visit the second one.
We discuss a rule for combining the exit times
from each of the metastable states
Renormalizing Heavy Quark Effective Theory at O(1/m_Q^3)
We present a calculation of the renormalized HQET Lagrangian at order
O(1/m_Q^3) in the one particle sector. The anomalous dimensions of local
operators and time ordered products of dimension 7 contributing at this order
are calculated in the one loop approximation. We show that a careful treatment
of the time ordered products is necessary to arrive at a gauge independent
renormalized lagrangian. Our result sets the stage for an investigation of
reparametrization invariance at O(1/m_Q^3).Comment: Latex, epsfig. Improved teXnology and modified conclusions. The
complete paper, including figures, is also available via anonymous ftp at
ftp://ttpux2.physik.uni-karlsruhe.de/ , or via www at
http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints
Nonperturbative Matching for Field Theories with Heavy Fermions
We examine a paradox, suggested by Banks and Dabholkar, concerning
nonperturbative effects in an effective field theory which is obtained by
integrating out a generation of heavy fermions, where the heavy fermion masses
arise from Yukawa couplings. They argue that light fermions in the effective
theory appear to decay via instanton processes, whereas their decay is
forbidden in the full theory. We resolve this paradox by showing that such
processes in fact do not occur in the effective theory, due to matching
corrections which cause the relevant light field configurations to have
infinite action.Comment: 10 pages, no figures, uses harvmac, Harvard University Preprint
HUTP-93/A03
- …