7,349 research outputs found
Time Averages of Markov Processes and Applications to Two-Timescale Problems
We show a decomposition into the sum of a martingale and a deterministic
quantity for time averages of the solutions to non-autonomous SDEs and for
discrete-time Markov processes. In the SDE case the martingale has an explicit
representation in terms of the gradient of the associated semigroup or
transition operator. We show how the results can be used to obtain quenched
Gaussian concentration inequalities for time averages and to provide insights
into the Averaging principle for two-timescale processes.Comment: 18 page
QCD at high baryon density in a random matrix model
A high density diquark phase seems to be a generic feature of QCD. If so it
should also be reproduced by random matrix models. We discuss a specific one in
which the random matrix elements of the Dirac operator are supplemented by a
finite chemical potential and by non-random elements which model the formation
of instanton-anti-instanton molecules. Comparing our results to those found in
a previous investigation by Vanderheyden and Jackson we find additional support
for our starting assumption, namely that the existence of a high density
diquark phase is common to all QCD-like models.Comment: 16 pages, 4 figures, final version to appear in Eur.Phys.J.
The Kondo Lattice Model
In this lecture, we review the experimental situation of heavy Fermions with
emphasis on the existence of a quantum phase transition (QPT) and related
non-Fermi liquid (NFL) effects. We overview the Kondo lattice model (KLM) which
is believed to describe the physics of those systems. After recalling the
existing theories based on large-N expansion and various N=2 schemes, we
present two alternative approaches: (i) a spin fluctuation-Kondo functional
integral approach treating the spin-fluctuation and Kondo effects on an equal
footing, and (ii) a supersymmetric theory enlarging the usual fermionic
representation of the spin into a mixed fermionic-bosonic representation in
order to describe the spin degrees of freedom as well as the Fermi-liquid type
excitations. This kind of approaches may open up new prospects for the
description of the critical phenomena associated to the quantum phase
transition in Heavy-Fermion systems.Comment: 27 pages, 6 figures, 51 references, appeared in the Proceedings of
the XXXVIII Cracow School of Theoretical Physics, Zakopane, Poland, June
1-10, 199
Supersymmetric Approach to Heavy-Fermion Systems
We present a new supersymmetric approach to the Kondo lattice model in order
to describe simultaneously the quasiparticle excitations and the low-energy
magnetic fluctuations in heavy-Fermion systems. This approach mixes the
fermionic and the bosonic representation of the spin following the standard
rules of superalgebra. Our results show the formation of a bosonic band within
the hybridization gap reflecting the spin collective modes. The density of
states at the Fermi level is strongly renormalized while the Fermi surface sum
rule includes states. The dynamical susceptibility is made of a Fermi
liquid superimposed on a localized magnetism contribution.Comment: 5 pages, 2 figure
Full Service ISDN Satellite (FSIS) network model for advanced ISDN satellite design and experiments
The Full Service Integrated Services Digital Network (FSIS) network model for advanced satellite designs describes a model suitable for discrete event simulations. A top down model design uses the Advanced Communications Technology Satellite (ACTS) as its basis. The ACTS and the Interim Service ISDN Satellite (ISIS) perform ISDN protocol analyses and switching decisions in the terrestrial domain, whereas FSIS makes all its analyses and decisions on-board the ISDN satellite
Scenarios and performance measures for advanced ISDN satellite design and experiments
Described here are the contemplated input and expected output for the Interim Service Integrated Services Digital Network (ISDN) Satellite (ISIS) and Full Service ISDN Satellite (FSIS) Models. The discrete event simulations of these models are presented with specific scenarios that stress ISDN satellite parameters. Performance measure criteria are presented for evaluating the advanced ISDN communication satellite designs of the NASA Satellite Communications Research (SCAR) Program
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