125 research outputs found
A local limit theorem for triple connections in subcritical Bernoulli percolation
We prove a local limit theorem for the probability of a site to be connected
by disjoint paths to three points in subcritical Bernoulli percolation on
in the limit where their distances tend to infinity.Comment: 31 page
On the Ornstein-Zernike behaviour for the Bernoulli bond percolation on in the supercitical regime
We prove Ornstein-Zernike behaviour in every direction for finite connection
functions of bond percolation on for when the
probability of occupation of a bond, is sufficiently close to Moreover, we
prove that equi-decay surfaces are locally analytic, strictly convex, with
positive Gaussian curvature.Comment: 18 pages, published versio
Rigorous Non-Perturbative Ornstein-Zernike Theory for Ising Ferromagnets
We rigorously derive the Ornstein-Zernike asymptotics of the pair-correlation
functions for finite-range Ising ferromagnets in any dimensions and at any
temperature above critical
Ornstein-Zernike Theory for the finite range Ising models above T_c
We derive precise Ornstein-Zernike asymptotic formula for the decay of the
two-point function in the general context of finite range Ising type models on
Z^d. The proof relies in an essential way on the a-priori knowledge of the
strict exponential decay of the two-point function and, by the sharp
characterization of phase transition due to Aizenman, Barsky and Fernandez,
goes through in the whole of the high temperature region T > T_c. As a
byproduct we obtain that for every T > T_c, the inverse correlation length is
an analytic and strictly convex function of direction.Comment: 36 pages, 5 figure
Random path representation and sharp correlations asymptotics at high-temperatures
We recently introduced a robust approach to the derivation of sharp
asymptotic formula for correlation functions of statistical mechanics models in
the high-temperature regime. We describe its application to the nonperturbative
proof of Ornstein-Zernike asymptotics of 2-point functions for self-avoiding
walks, Bernoulli percolation and ferromagnetic Ising models. We then extend the
proof, in the Ising case, to arbitrary odd-odd correlation functions. We
discuss the fluctuations of connection paths (invariance principle), and relate
the variance of the limiting process to the geometry of the equidecay profiles.
Finally, we explain the relation between these results from Statistical
Mechanics and their counterparts in Quantum Field Theory
A Finite-Volume Version of Aizenman-Higuchi Theorem for the 2d Ising Model
In the late 1970s, in two celebrated papers, Aizenman and Higuchi
independently established that all infinite-volume Gibbs measures of the
two-dimensional ferromagnetic nearest-neighbor Ising model are convex
combinations of the two pure phases. We present here a new approach to this
result, with a number of advantages: (i) We obtain an optimal finite-volume,
quantitative analogue (implying the classical claim); (ii) the scheme of our
proof seems more natural and provides a better picture of the underlying
phenomenon; (iii) this new approach might be applicable to systems for which
the classical method fails.Comment: A couple of typos corrected. To appear in Probab. Theory Relat.
Field
Low density expansion for Lyapunov exponents
In some quasi-one-dimensional weakly disordered media, impurities are large
and rare rather than small and dense. For an Anderson model with a low density
of strong impurities, a perturbation theory in the impurity density is
developed for the Lyapunov exponent and the density of states. The Lyapunov
exponent grows linearly with the density. Anomalies of the Kappus-Wegner type
appear for all rational quasi-momenta even in lowest order perturbation theory
Expanding direction of the period doubling operator
We prove that the period doubling operator has an expanding direction at the
fixed point. We use the induced operator, a ``Perron-Frobenius type operator'',
to study the linearization of the period doubling operator at its fixed point.
We then use a sequence of linear operators with finite ranks to study this
induced operator. The proof is constructive. One can calculate the expanding
direction and the rate of expansion of the period doubling operator at the
fixed point
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