arXiv subjects

Claudio Bonanno

Publications and source records attributed to Claudio Bonanno.

At least 91 records · Page 5Linked to original sources

arXiv2019

Series expansions for Maass forms on the full modular group from the Farey transfer operators

We deepen the study of the relations previously established by Mayer, Lewis and Zagier, and the authors, among the eigenfunctions of the transfer operators of the Gauss and the Farey maps, the solutions of the Lewis-Zagier three-term functional equation and the Maass forms on the modular surface $PSL(2,\Z)\backslash \HH$. In particular we introduce an "inverse" of the integral transform studied by Lewis and Zagier, and use it to obtain new series expansions for the Maass cusp forms and the non-holomorphic Eisenstein series restricted to the imaginary axis. As corollaries we obtain further information on the Fourier coefficients of the forms, including a new series expansion for the divisor function.

math.NT↗

arXiv2019

Topology via Spectral Projectors with Staggered Fermions

The spectral projectors method is a way to obtain a theoretically well posed definition of the topological susceptibility on the lattice. Up to now this method has been defined and applied only to Wilson fermions. The goal of this work is to extend the method to staggered fermions, giving a definition for the staggered topological susceptibility and testing it in the pure $SU(3)$ gauge theory. Besides, we also generalize the method to higher-order cumulants of the topological charge distribution.

hep-lat↗

arXiv2018

Infinite mixing for one-dimensional maps with an indifferent fixed point

We study the properties of `infinite-volume mixing' for two classes of intermittent maps: expanding maps $[0,1] \longrightarrow [0,1]$ with an indifferent fixed point at 0 preserving an infinite, absolutely continuous measure, and expanding maps $\mathbb{R}^+ \longrightarrow \mathbb{R}^+$ with an indifferent fixed point at $+\infty$ preserving the Lebesgue measure. All maps have full branches. While certain properties are easily adjudicated, the so-called global-local mixing, namely the decorrelation of a global and a local observable, is harder to prove. We do this for two subclasses of systems. The first subclass includes, among others, the Farey map. The second class includes the standard Pomeau-Manneville map $x \mapsto x+x^2$ mod 1. Morevoer, we use global-local mixing to prove certain limit theorems for our intermittent maps.

math.DS↗

arXiv2018

Topological properties of $CP^{N-1}$ models in the large-$N$ limit

We investigate, by numerical simulations on a lattice, the $θ$-dependence of 2$d$ $CP^{N-1}$ models for a range of $N$ going from 9 to 31, combining imaginary $θ$ and simulated tempering techniques to improve the signal-to-noise ratio and alleviate the critical slowing down of the topological modes. We provide continuum extrapolations for the second and fourth order coefficients in the Taylor expansion in $θ$ of the vacuum energy of the theory, parameterized in terms of the topological susceptibility $χ$ and of the so-called $b_2$ coefficient. Those are then compared with available analytic predictions obtained within the $1/N$ expansion, pointing out that higher order corrections might be relevant in the explored range of $N$, and that this fact might be related to the non-analytic behavior expected for $N = 2$. We also consider sixth-order corrections in the $θ$ expansion, parameterized in terms of the so-called $b_4$ coefficient: in this case our present statistical accuracy permits to have reliable non-zero continuum estimations only for $N \leq 11$, while for larger values we can only set upper bounds. The sign and values obtained for $b_4$ are compared to large-$N$ predictions, as well as to results obtained for $SU(N_c)$ Yang-Mills theories, for which a first numerical determination is provided in this study for the case $N_c = 2$.

hep-lat↗

arXiv2018

Global-local mixing for the Boole map

In the context of 'infinite-volume mixing' we prove global-local mixing for the Boole map, a.k.a. Boole transformation, which is the prototype of a non-uniformly expanding map with two neutral fixed points. Global-local mixing amounts to the decorrelation of all pairs of global and local observables. In terms of the equilibrium properties of the system it means that the evolution of every absolutely continuous probability measure converges, in a certain precise sense, to an averaging functional over the entire space.

math.DS↗

arXiv2015

Escape rates for the Farey map with approximated holes

We study the escape rate for the Farey map, an infinite measure preserving system, with a hole including the indifferent fixed point. Due to the ergodic properties of the map, the standard theoretical approaches to this problem cannot be applied. To overcome this difficulties we propose here to consider approximations of the hole by means of real analytic functions. We introduce a particular family of approximations and study numerically the behavior of the escape rate for "shrinking" approximated holes. The results suggest that the scaling of the escape rate depends on the chosen approximation, but "converges" to the behavior found for piecewise linear approximations of the map in \cite{KM}.

math.DS↗

arXiv2014

A complexity approach to the soliton resolution conjecture

The soliton resolution conjecture is one of the most interesting open problems in the theory of nonlinear dispersive equations. Roughly speaking it asserts that a solution with generic initial condition converges to a finite number of solitons plus a radiative term. In this paper we use the complexity of a finite object, a notion introduced in Algorithmic Information Theory, to show that the soliton resolution conjecture is equivalent to the analogous of the second law of thermodynamics for the complexity of a solution of a dispersive equation.

math-ph↗

arXiv2013

Solitons in gauge theories: existence and dependence on the charge

In this paper we review recent results on the existence of non-topological solitons in classical relativistic nonlinear field theories. We follow the Coleman approach, which is based on the existence of two conservation laws, energy and charge. In particular we show that under mild assumptions on the nonlinear term it is possible to prove the existence of solitons for a set of admissible charges. This set has been studied for the nonlinear Klein-Gordon equation, and in this paper we state new results in this direction for the Klein-Gordon-Maxwell system.

math-ph↗

arXiv2013

Long time dynamics of highly concentrated solitary waves for the nonlinear Schroedinger equation

In this paper we study the behavior of solutions of a nonlinear Schroedinger equation in presence of an external potential, which is allowed to be singular at one point. We show that the solution behaves like a solitary wave for long time even if we start from a unstable solitary wave, and its dynamics coincide with that of a classical particle evolving according to a natural effective Hamiltonian.

math.AP↗

arXiv2013

Soliton dynamics for the generalized Choquard equation

We investigate the soliton dynamics for a class of nonlinear Schrödinger equations with a non-local nonlinear term. In particular, we consider what we call {\em generalized Choquard equation} where the nonlinear term is $(|x|^{θ-N} * |u|^p)|u|^{p-2}u$. This problem is particularly interesting because the ground state solutions are not known to be unique or non-degenerate.

math.AP↗

arXiv2013

Multiplicity of positive solutions for nonlinear field equations in $\R^{N}$

In this paper we study the multiplicity of positive solutions for nonlinear elliptic equations on $\R^N$. The number of solutions is greater or equal than the number of disjoint intervals on which the nonlinear term is negative. Applications are given to multiplicity of standing waves for the nonlinear Schrödinger and Klein-Gordon equations.

math.AP↗

arXiv2012

On the existence of hylomorphic vortices in the nonlinear Klein-Gordon equation

In this paper we prove the existence of vortices, namely standing waves with non null angular momentum, for the nonlinear Klein-Gordon equation in dimension $N\geq 3$. We show with variational methods that the existence of these kind of solutions, that we have called \emph{hylomorphic vortices}, depends on a suitable energy-charge ratio. Our variational approach turns out to be useful for numerical investigations as well. In particular, some results in dimension N=2 are reported, namely exemplificative vortex profiles by varying charge and angular momentum, together with relevant trends for vortex frequency and energy-charge ratio. The stability problem for hylomorphic vortices is also addressed. In the absence of conclusive analytical results, vortex evolution is numerically investigated: the obtained results suggest that, contrarily to solitons with null angular momentum, vortex are unstable.

math.AP↗

arXiv2012

Soliton dynamics of NLS with singular potentials

We investigate the validity of a soliton dynamics behavior in the semi-relativistic limit for the nonlinear Schrödinger equation in $\R^{N}, N\ge 3$, in presence of a singular external potential.

math.AP↗

arXiv2012

Dynamics of continued fractions and kneading sequences of unimodal maps

In this paper we construct a correspondence between the parameter spaces of two families of one-dimensional dynamical systems, the alpha-continued fraction transformations T_alpha and unimodal maps. This correspondence identifies bifurcation parameters in the two families, and allows one to transfer topological and metric properties from one setting to the other. As an application, we recover results about the real slice of the Mandelbrot set, and the set of univoque numbers.

math.DS↗

arXiv2011

A thermodynamic approach to two-variable Ruelle and Selberg zeta functions via the Farey map

In this paper we consider the transfer operator approach to the Ruelle and Selberg zeta functions associated to continued fractions transformations and the geodesic flow on the full modular surface. We extend the results by Ruelle and Mayer to two-variable zeta functions, $ζ(q,z)$ and $Z(q,z)$. The $q$ variable plays the role of the inverse temperature and the introduction of the "geometric variable" $z$ is essential in the tentative to provide a general approach, based on the Farey map, to the correspondence between the analytic properties of the zeta functions themselves, the spectral properties of a class of generalised transfer operators and the theory of a generalisation of the three-term functional equations studied by Lewis and Zagier. The first step in this direction is a detailed study of the spectral properties of a family of signed transfer operators $\PP^{\pm}_{q}$ associated to the Farey map.

math.DS↗

arXiv2011

Solitary waves and vortices in non-Abelian gauge theories with matter

We consider a non-Abelian gauge theory in R^{4} equipped with the Minkowski metric, which provides a model for the interaction between a bosonic matter field and a gauge field with gauge group SU(2). We prove the existence of solitary waves which are related to those found for the Klein-Gordon-Maxwell equations.

math-ph↗

arXiv2009

Existence and multiplicity of stable bound states for the nonlinear Klein-Gordon equation

We are interested in the problem of existence of soliton-like solutions for the nonlinear Klein-Gordon equation. In particular we study some necessary and sufficient conditions on the nonlinear term to obtain solitons of a given charge. We remark that the conditions we consider can be easily verified. Moreover we show that multiplicity of solitons of the same charge is guaranteed by the "shape" of the nonlinear term for equations on $\R^{N}$, hence without appealing to topological or geometrical properties of the domain.

math.AP↗

arXiv2009

Nonlinear Schrödinger equations with strongly singular potentials

In this paper we look for standing waves for nonlinear Schrödinger equations $$ i\frac{\partial ψ}{\partial t}+Δψ- g(|y|) ψ-W^{\prime}(| ψ|)\fracψ{| ψ|}=0 $$ with cylindrically symmetric potentials $g$ vanishing at infinity and non-increasing, and a $C^1$ nonlinear term satisfying weak assumptions. In particular we show the existence of standing waves with non-vanishing angular momentum with prescribed $L^2$ norm. The solutions are obtained via a minimization argument, and the proof is given for an abstract functional which presents lack of compactness. As a particular case we prove the existence of standing waves with non-vanishing angular momentum for the nonlinear hydrogen atom equation.

math-ph↗