157 research outputs found
Large deviations for clocks of self-similar processes
The Lamperti correspondence gives a prominent role to two random time
changes: the exponential functional of a L\'evy process drifting to
and its inverse, the clock of the corresponding positive self-similar process.
We describe here asymptotical properties of these clocks in large time,
extending the results of Yor and Zani
On Eigenvalue spacings for the 1-D Anderson model with singular site distribution
We study eigenvalue spacings and local eigenvalue statistics for 1D lattice
Schrodinger operators with Holder regular potential, obtaining a version of
Minami's inequality and Poisson statistics for the local eigenvalue spacings.
The main additional new input are regular properties of the Furstenberg
measures and the density of states obtained in some of the author's earlier
work.Comment: 13 page
Transient backbending behavior in the Ising model with fixed magnetization
The physical origin of the backbendings in the equations of state of finite
but not necessarily small systems is studied in the Ising model with fixed
magnetization (IMFM) by means of the topological properties of the observable
distributions and the analysis of the largest cluster with increasing lattice
size. Looking at the convexity anomalies of the IMFM thermodynamic potential,
it is shown that the order of the transition at the thermodynamic limit can be
recognized in finite systems independently of the lattice size. General
statistical mechanics arguments and analytical calculations suggest that the
backbending in the caloric curve is a transient behaviour which should not
converge to a plateau in the thermodynamic limit, while the first order
transition is signalled by a discontinuity in other observables.Comment: 24 pages, 11 figure
A new mechanism of mass protection for fermions
We present a way of protecting a Dirac fermion interacting with a scalar
(Higgs) field from getting a mass from the vacuum. It is obtained through an
implementation of translational symmetry when the theory is formulated with a
momentum cutoff, which forbids the usual Yukawa term. We consider that this
mechanism can help to understand the smallness of neutrino masses without a
tuning of the Yukawa coupling. The prohibition of the Yukawa term for the
neutrino forbids at the same time a gauge coupling between the right-handed
electron and neutrino. We prove that this mechanism can be implemented on the
lattice.Comment: LATTICE99(Higgs,Yukawa,SUSY), 3 page
Role of isospin in the nuclear liquid-gas phase transition
We study the thermodynamics of asymmetric nuclear matter using a mean field
approximation with a Skyrme effective interaction, in order to establish its
phase diagram and more particularly the influence of isospin on the order of
the transition. A new statistical method is introduced to study the
thermodynamics of a multifluid system, keeping only one density fixed the
others being replaced by their intensive conjugated variables. In this ensemble
phase coexistence reduces to a simple one dimensional Maxwell construction. For
a fixed temperature under a critical value, a coexistence line is obtained in
the plane of neutron and proton chemical potentials. Along this line the grand
potential presents a discontinuous slope showing that the transition is first
order except at the two ending points where it becomes second order. This
result is not in contradiction with the already reported occurrence of a
continuous transformation when a constant proton fraction is imposed. Indeed,
the proton fraction being an order parameter in asymmetric matter, the
constraint can only be fulfilled by gradual phase mixing along the first-order
phase transition line leading to a continuous pressure.Comment: To appear in Nuclear Physics
Non equilibrium effects in fragmentation
We study, using molecular dynamics techniques, how boundary conditions affect
the process of fragmentation of finite, highly excited, Lennard-Jones systems.
We analyze the behavior of the caloric curves (CC), the associated thermal
response functions (TRF) and cluster mass distributions for constrained and
unconstrained hot drops. It is shown that the resulting CC's for the
constrained case differ from the one in the unconstrained case, mainly in the
presence of a ``vapor branch''. This branch is absent in the free expanding
case even at high energies . This effect is traced to the role played by the
collective expansion motion. On the other hand, we found that the recently
proposed characteristic features of a first order phase transition taking place
in a finite isolated system, i.e. abnormally large kinetic energy fluctuations
and a negative branch in the TRF, are present for the constrained (dilute) as
well the unconstrained case. The microscopic origin of this behavior is also
analyzed.Comment: 21 pages, 11 figure
Time Scale Approach for Chirp Detection
International audienceTwo different approaches for joint detection and estimation of signals embedded in stationary random noise are considered and compared, for the subclass of amplitude and frequency modulated signals. Matched filter approaches are compared to time-frequency and time scale based approaches. Particular attention is paid to the case of the so-called " power-law chirps " , characterized by monomial and polynomial amplitude and frequency functions. As target application, the problem of gravitational waves at interferometric detectors is considered
Experimental Signals of Phase Transition
The connection between the thermodynamics of charged finite nuclear systems
and the asymptotically measured partitions is presented. Some open questions,
concerning in particular equilibrium partitions are discussed. We show a
detailed comparison of the decay patterns in Au+ C,Cu,Au central collisions and
in Au quasi-projectile events. Observation of abnormally large fluctuations in
carefully selected samples of data is reported as an indication of a first
order phase transition (negative heat capacity) in the nuclear equation of
state.Comment: 8 pages, 8th International Conference on Nucleus-Nucleus Collisions,
Moscow 200
Color confinement and dual superconductivity of the vacuum. III
It is demonstrated that monopole condensation in the confined phase of SU(2)
and SU(3) gauge theories is independent of the specific Abelian projection used
to define the monopoles. Hence the dual excitations which condense in the
vacuum to produce confinement must have magnetic U(1) charge in all the Abelian
projections. Some physical implications of this result are discussed.Comment: 6 pages, 5 postscript figure
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