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Yacin Ameur

Publications and source records attributed to Yacin Ameur.

32 records · Page 2Linked to original sources
arXiv2020

On boundary confinements for the Coulomb gas

We introduce a family of boundary confinements for Coulomb gas ensembles, and study them in the two-dimensional determinantal case of random normal matrices. The family interpolates between the free boundary and hard edge cases, which have been well studied in various random matrix theories. The confinement can also be relaxed beyond the free boundary to produce ensembles with more fuzzy boundaries, i.e., where the particles are more and more likely to be found outside of the boundary. The resulting ensembles are investigated with respect to scaling limits and distribution of the maximum modulus. In particular, we prove existence of a new point field - a limit of scaling limits to the ultraweak point when the droplet ceases to be well defined.

math-ph↗
arXiv2019

Scaling limits of random normal matrix processes at singular boundary points

We give a method for taking microscopic limits of normal matrix ensembles. We apply this method to study the behaviour near certain types of singular points on the boundary of the droplet. Our investigation includes ensembles without restrictions near the boundary, as well as hard edge ensembles, where the eigenvalues are confined to the droplet. We establish in both cases existence of new types of determinantal point fields, which differ from those which can appear at a regular boundary point, or in the bulk.

math.PR↗
arXiv2019

Microscopic densities and Fock-Sobolev spaces

We study two-dimensional eigenvalue ensembles close to certain types of singular points in the bulk of the droplet. We prove existence of a microscopic density which quickly approaches the classical equilibrium density, as the distance from the singularity increases beyond the microscopic scale. As a consequence we obtain asymptotics for the Bergman function of certain Fock-Sobolev spaces of entire functions.

math.CV↗
arXiv2019

Interpolation between Hilbert spaces

This note comprises a synthesis of certain results in the theory of exact interpolation between Hilbert spaces. In particular, we examine various characterizations of interpolation spaces and their relations to a number of results in operator-theory and in function-theory.

math.FA↗
arXiv2017

Repulsion in low temperature $β$-ensembles

We prove a result on separation of particles in a two-dimensional Coulomb plasma, which holds provided that the inverse temperature $β$ satisfies $β>1$. For large $β$, separation is obtained at the same scale as the conjectural Abrikosov lattice optimal separation.

math.PR↗
arXiv2016

On bulk singularities in the random normal matrix model

We extend the method of rescaled Ward identities of Ameur-Kang-Makarov to study the distribution of eigenvalues close to a bulk singularity, i.e. a point in the interior of the droplet where the density of the classical equilibrium measure vanishes. We prove results to the effect that a certain "dominant part" of the Taylor expansion determines the microscopic properties near a bulk singularity. A description of the distribution is given in terms of a special entire function, which depends on the nature of the singularity (a Mittag-Leffler function in the case of a rotationally symmetric singularity).

math-ph↗
arXiv2015

Rescaling Ward identities in the random normal matrix model

We study existence and universality of scaling limits for the eigenvalues of a random normal matrix, in particular at points on the boundary of the spectrum. Our approach uses Ward's equation, which is an identity satisfied by the 1-point function.

math.PR↗
arXiv2015

Random normal matrices and Ward identities

Consider the random normal matrix ensemble associated with a potential on the plane which is sufficiently strong near infinity. It is known that, to a first approximation, the eigenvalues obey a certain equilibrium distribution, given by Frostman's solution to the minimum energy problem of weighted logarithmic potential theory. On a finer scale, one can consider fluctuations of eigenvalues about the equilibrium. In the present paper, we give the correction to the expectation of fluctuations, and we prove that the potential field of the corrected fluctuations converge on smooth test functions to a Gaussian free field with free boundary conditions on the droplet associated with the potential.

math.CV↗
arXiv2011

Beurling-Landau densities of weighted Fekete sets and correlation kernel estimates

In this paper we discuss equidistribution results for weighted Fekete sets in subsets of the plane. More precisely, we show that Fekete sets are maximally spread out relative to a rescaled version of the Beurling--Landau density, in the "droplet" corresponding to the given weight. Our method combines Landau's idea to relate the density of a family of discrete sets to properties of the spectrum of the concentration operator, with estimates for the correlation kernel of the corresponding random normal matrix ensemble.

math.CV↗
arXiv2009

Berezin transform in polynomial Bergman spaces

We study the reproducing kernel for weighted polynomial Bergman spaces and consider applications to the Berezin transform. Some of our results have applications in random matrix theory, a topic which we discuss in a separate (companion) paper.

math.CV↗
arXiv2005

K-divisibility constants for some special couples

We prove new estimates of the $K$-divisibility constants for some special Banach couples. In particular, we prove that the $K$-divisibility constant for a couple of the form $(U\oplus V, U)$ where $U$ and $V$ are non-trivial Hilbert spaces equals $2/\sqrt{3}$. We also prove estimates for the $K$-divisibility constant of the two-dimensional version of the couple $(L_2,L_\infty)$, proving in particular that this couple is not exactly $K$-divisible. There are also several auxiliary results, including some estimates for relative Calderón constants for finite dimensional couples.

math.FA↗