7,675 research outputs found
Convergence to equilibrium for finite Markov processes, with application to the Random Energy Model
We estimate the distance in total variation between the law of a finite state
Markov process at time t, starting from a given initial measure, and its unique
invariant measure. We derive upper bounds for the time to reach the
equilibrium. As an example of application we consider a special case of finite
state Markov process in random environment: the Metropolis dynamics of the
Random Energy Model. We also study the process of the environment as seen from
the process
Carne--Varopoulos bounds for centered random walks
We extend the Carne--Varopoulos upper bound on the probability transitions of
a Markov chain to a certain class of nonreversible processes by introducing the
definition of a ``centering measure.'' In the case of random walks on a group,
we study the connections between different notions of centering.Comment: Published at http://dx.doi.org/10.1214/009117906000000052 in the
Annals of Probability (http://www.imstat.org/aop/) by the Institute of
Mathematical Statistics (http://www.imstat.org
From Jack to Double Jack Polynomials via the Supersymmetric Bridge
The Calogero-Sutherland model occurs in a large number of physical contexts,
either directly or via its eigenfunctions, the Jack polynomials. The
supersymmetric counterpart of this model, although much less ubiquitous, has an
equally rich structure. In particular, its eigenfunctions, the Jack
superpolynomials, appear to share the very same remarkable combinatorial and
structural properties as their non-supersymmetric version. These
super-functions are parametrized by superpartitions with fixed bosonic and
fermionic degrees. Now, a truly amazing feature pops out when the fermionic
degree is sufficiently large: the Jack superpolynomials stabilize and
factorize. Their stability is with respect to their expansion in terms of an
elementary basis where, in the stable sector, the expansion coefficients become
independent of the fermionic degree. Their factorization is seen when the
fermionic variables are stripped off in a suitable way which results in a
product of two ordinary Jack polynomials (somewhat modified by plethystic
transformations), dubbed the double Jack polynomials. Here, in addition to
spelling out these results, which were first obtained in the context of
Macdonal superpolynomials, we provide a heuristic derivation of the Jack
superpolynomial case by performing simple manipulations on the supersymmetric
eigen-operators, rendering them independent of the number of particles and of
the fermionic degree. In addition, we work out the expression of the
Hamiltonian which characterizes the double Jacks. This Hamiltonian, which
defines a new integrable system, involves not only the expected
Calogero-Sutherland pieces but also combinations of the generators of an
underlying affine algebra
Schur Superpolynomials: Combinatorial Definition and Pieri Rule
Schur superpolynomials have been introduced recently as limiting cases of the
Macdonald superpolynomials. It turns out that there are two natural
super-extensions of the Schur polynomials: in the limit and
, corresponding respectively to the Schur
superpolynomials and their dual. However, a direct definition is missing. Here,
we present a conjectural combinatorial definition for both of them, each being
formulated in terms of a distinct extension of semi-standard tableaux. These
two formulations are linked by another conjectural result, the Pieri rule for
the Schur superpolynomials. Indeed, and this is an interesting novelty of the
super case, the successive insertions of rows governed by this Pieri rule do
not generate the tableaux underlying the Schur superpolynomials combinatorial
construction, but rather those pertaining to their dual versions. As an aside,
we present various extensions of the Schur bilinear identity
Co-reduction of aluminium and lanthanide ions in molten fluorides : application to cerium and samarium extraction from nuclear waste
This work concerns the method of co-reduction process with aluminium ions in LiF–CaF2 medium (79–21 mol.%) on tungsten electrode for cerium and samarium extraction. Electrochemical techniques such as cyclic and square wave voltammetries, and potentiostatic electrolyses were used to study the co-reduction of CeF3 and SmF3 with AlF3. For each of these elements, specific peaks of Al–Ce and Al–Sm alloys formationwere observed by voltammetry aswell as peaks of pure cerium and aluminium, and pure samarium and aluminium respectively. The difference of potential measured between the solvent reduction and the alloy formation suggests expecting an extraction efficiency of 99.99% of each lanthanide by the process. Different intermetallic compounds were obtained for different potentiostatic electrolysis and were characterised by Scanning Electron Microscopy with EDS probe. The validity of the process was verified by carrying out cerium and samarium extractions in the form of Al–Ln alloy; the extraction efficiency was 99.5% for Ce(III) and 99.4% for Sm(III)
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