2,752 research outputs found
Entropy of capacities on lattices and set systems
We propose a definition for the entropy of capacities defined on lattices.
Classical capacities are monotone set functions and can be seen as a
generalization of probability measures. Capacities on lattices address the
general case where the family of subsets is not necessarily the Boolean lattice
of all subsets. Our definition encompasses the classical definition of Shannon
for probability measures, as well as the entropy of Marichal defined for
classical capacities. Some properties and examples are given
Capacities and Games on Lattices: A Survey of Result
We provide a survey of recent developments about capacities (or fuzzy measures) and ccoperative games in characteristic form, when they are defined on more general structures than the usual power set of the universal set, namely lattices. In a first part, we give various possible interpretations and applications of these general concepts, and then we elaborate about the possible definitions of usual tools in these theories, such as the Choquet integral, the Möbius transform, and the Shapley value.capacity, fuzzy measure, game, lattice, Choquet integral,Shapley value
Entropy of unimodular Lattice Triangulations
Triangulations are important objects of study in combinatorics, finite
element simulations and quantum gravity, where its entropy is crucial for many
physical properties. Due to their inherent complex topological structure even
the number of possible triangulations is unknown for large systems. We present
a novel algorithm for an approximate enumeration which is based on calculations
of the density of states using the Wang-Landau flat histogram sampling. For
triangulations on two-dimensional integer lattices we achive excellent
agreement with known exact numbers of small triangulations as well as an
improvement of analytical calculated asymptotics. The entropy density is
consistent with rigorous upper and lower bounds. The presented
numerical scheme can easily be applied to other counting and optimization
problems.Comment: 6 pages, 7 figure
Cooling and thermometry of atomic Fermi gases
We review the status of cooling techniques aimed at achieving the deepest
quantum degeneracy for atomic Fermi gases. We first discuss some physical
motivations, providing a quantitative assessment of the need for deep quantum
degeneracy in relevant physics cases, such as the search for unconventional
superfluid states. Attention is then focused on the most widespread technique
to reach deep quantum degeneracy for Fermi systems, sympathetic cooling of
Bose-Fermi mixtures, organizing the discussion according to the specific
species involved. Various proposals to circumvent some of the limitations on
achieving the deepest Fermi degeneracy, and their experimental realizations,
are then reviewed. Finally, we discuss the extension of these techniques to
optical lattices and the implementation of precision thermometry crucial to the
understanding of the phase diagram of classical and quantum phase transitions
in Fermi gases.Comment: 33 pages, 15 figures, contribution to the 100th anniversary of the
birth of Vitaly L. Ginzbur
Condensation in stochastic particle systems with stationary product measures
We study stochastic particle systems with stationary product measures that
exhibit a condensation transition due to particle interactions or spatial
inhomogeneities. We review previous work on the stationary behaviour and put it
in the context of the equivalence of ensembles, providing a general
characterization of the condensation transition for homogeneous and
inhomogeneous systems in the thermodynamic limit. This leads to strengthened
results on weak convergence for subcritical systems, and establishes the
equivalence of ensembles for spatially inhomogeneous systems under very general
conditions, extending previous results which were focused on attractive and
finite systems. We use relative entropy techniques which provide simple proofs,
making use of general versions of local limit theorems for independent random
variables.Comment: 44 pages, 4 figures; improved figures and corrected typographical
error
Approximate Capacities of Two-Dimensional Codes by Spatial Mixing
We apply several state-of-the-art techniques developed in recent advances of
counting algorithms and statistical physics to study the spatial mixing
property of the two-dimensional codes arising from local hard (independent set)
constraints, including: hard-square, hard-hexagon, read/write isolated memory
(RWIM), and non-attacking kings (NAK). For these constraints, the strong
spatial mixing would imply the existence of polynomial-time approximation
scheme (PTAS) for computing the capacity. It was previously known for the
hard-square constraint the existence of strong spatial mixing and PTAS. We show
the existence of strong spatial mixing for hard-hexagon and RWIM constraints by
establishing the strong spatial mixing along self-avoiding walks, and
consequently we give PTAS for computing the capacities of these codes. We also
show that for the NAK constraint, the strong spatial mixing does not hold along
self-avoiding walks
An axiomatization of entropy of capacities on set systems
International audienceWe present an axiomatization of the entropy of capacities defined on set systems which are not necessarily the whole power set, but satisfy a condition of regularity. This entropy encompasses the definition of Marichal and Roubens for the entropy of capacities. Its axiomatization is in the spirit of the one of Faddeev for the classical Shannon entropy. In addition, we present also an axiomatization of the entropy for capacities proposed by Dukhovn
Thermodynamics of low dimensional spin-1/2 Heisenberg ferromagnets in an external magnetic field within Green function formalism
The thermodynamics of low dimensional spin-1/2 Heisenberg ferromagnets (HFM)
in an external magnetic field is investigated within a second-order two-time
Green function formalism in the wide temperature and field range. A crucial
point of the proposed scheme is a proper account of the analytical properties
for the approximate transverse commutator Green function obtained as a result
of the decoupling procedure. A good quantitative description of the correlation
functions, magnetization, susceptibility, and heat capacity of the HFM on a
chain, square and triangular lattices is found for both infinite and
finite-sized systems. The dependences of the thermodynamic functions of 2D HFM
on the cluster size are studied. The obtained results agree well with the
corresponding data found by Bethe ansatz, exact diagonalization, high
temperature series expansions, and quantum Monte Carlo simulations.Comment: 11 pages, 14 figure
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