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Fumihiko Nakano

Publications and source records attributed to Fumihiko Nakano.

At least 19 recordsLinked to original sources
arXiv2026

Beta Ensembles in the Freezing Regime and Finite Free Convolutions

In the freezing regime where the system size N is fixed and the inverse temperature beta tends to infinity, the eigenvalues of Gaussian beta ensembles converge to zeros of the Nth Hermite polynomial. That law of large numbers has been proved by analyzing the joint density or reading off the random matrix model. This paper studies its dynamical version of this phenomenon. We show that in the freezing regime the eigenvalue processes called beta Dyson Brownian motions converge to deterministic limiting processes which can be written as the finite free convolution of the initial data and the zeros of Hermite polynomials. This result is a counterpart of those in the random matrix regime where N tends to infinity with fixed beta, as well as to the high temperature regime where N tends to infinity while beta N remains bounded. We also establish Gaussian fluctuations around the limit and deal with the Laguerre case.

math.PR↗
arXiv2026

The spectral measures of random Jacobi matrices related to beta ensembles at high temperature and Dirichlet processes

In a high temperature regime where $βN \to 2c$, the empirical distribution of the eigenvalues of Gaussian beta ensembles, beta Laguerre ensembles and beta Jacobi ensembles converges to a limiting measure which is related to associated Hermite polynomials, associated Laguerre polynomials and associated Jacobi polynomials, respectively. Here $β$ is the inverse temperature parameter, $N$ is the system size and $c>0$ is a given constant. This paper studies the spectral measure of the random tridiagonal matrix model of the three classical beta ensembles. We show that in the high temperature regime, the spectral measure converges in distribution to a Dirichlet process with base distribution being the limiting distribution, and scaling parameter $c$. Consequently, the spectral measure of a related semi-infinite Jacobi matrix coincides with that Dirichlet process, which provides examples of random Jacobi matrices with explicit spectral measures.

math-ph↗
arXiv2025

Eigenvalue statistics for random polymer models: Localization and delocalization

We study the local eigenvalue statistics (LES) associated with one-dimensional lattice models of random polymers. We consider models constructed from two polymers. Each polymer is a finite interval of lattice points with a finite potential. These polymers are distributed along $\mathbb{Z}$ according to a Bernoulli distribution. The deterministic spectrum for these models is dense pure point, and is known to contain finitely-many critical energies. In this paper, we prove that the LES centered at these critical energies is described by a uniform clock process, and that the LES for the unfolded eigenvalues, centered at any other energy in the deterministic spectrum, is a Poisson point process. These results add to our understanding of these models that exhibit dynamical localization in any energy interval avoiding the critical energies [Damanik, Sims, Stolz] [De Bievre, Germinet], and nontrivial transport for wave packets with initial states supported at an integer point [Jitomirskaya, Schultz-Baldes, Stolz]. We show that the projection of these initial states onto spectral subspaces associated with any energy interval that contains all of the critical energies exhibit nontrivial transport, refining the connection between nontrivial transport and the critical energies. Finally, we also prove that the transition in the unfolded LES is sharp at the critical energies.

math-ph↗
arXiv2025

Integrated density of states for the Poisson point interactions on $\mathbf{R}^3$

We determine the principal term of the asymptotics of the integrated density of states (IDS) $N(λ)$ for the Schrödinger operator with point interactions on $\mathbf{R}^3$ as $λ\to -\infty$, provided that the set of positions of the point obstacles is the Poisson configuration, and the interaction parameters are bounded i.i.d.\ random variables. In particular, we prove $N(λ) =O(|λ|^{-3/2})$ as $λ\to -\infty$. In the case that all interaction parameters are equal to a constant, we give a more detailed asymptotics of $N(λ)$, and verify the result by a numerical method using R.

math-ph↗
arXiv2025

Classical beta ensembles and related eigenvalues processes at high temperature and the Markov--Krein transform

The aim of this paper is to identify the limit in a high temperature regime of classical beta ensembles on the real line and related eigenvalue processes by using the Markov--Krein transform. We show that the limiting measure of Gaussian beta ensembles (resp.\ beta Laguerre ensembles and beta Jacobi ensembles) is the inverse Markov--Krein transform of the Gaussian distribution (resp.\ the gamma distribution and the beta distribution). At the process level, we show that the limiting probability measure-valued process is the inverse Markov--Krein transform of a certain 1d stochastic process.

math.PR↗
arXiv2025

Non-isomorphic Cayley Graphs with Same Random Walk Distributions

We construct an infinite family of triples (G,S1, S2) each consisting of a group G and a pair (S1, S2) of distinct subsets of G with the following properties. i The two Cayley graphs Cay(G, S1) and Cay(G,S2) are non-isomorphic. ii The distributions of the simple random walks on Cay(G,S1) and Cay(G,S2) are the same if one takes an appropriate correspondence between the two vertex sets at each step. iii The spectral set of Cay(G, Si) is decomposed into a disjoint union of two subsets A and B_i of the equal size which satisfies B1 = -B2.

math.CO↗
arXiv2023

Beta Jacobi ensembles and associated Jacobi polynomials, II

In a high temperature regime, it was shown in Trinh--Trinh (\emph{J.\ Stat.\ Phys.}\ \textbf{185}(1), Paper No.\ 4, 15 (2021)) that the empirical distribution of beta Jacobi ensembles converges to a limiting probability measure which is related to Model III of associated Jacobi polynomials. In this paper, we establish Gaussian fluctuations around the limit whose statement involves orthogonal polynomials. For the proofs, we refine a moment method at the process level which has been used to deal with Gaussian beta ensembles and beta Laguerre ensembles.

math.PR↗
arXiv2023

Limit theorems for moment processes of beta Dyson's Brownian motions and beta Laguerre processes

In the regime where the parameter beta is proportional to the reciprocal of the system size, it is known that the empirical distribution of Gaussian beta ensembles (resp.\ beta Laguerre ensembles) converges to a probability measure of associated Hermite polynomials (resp.\ associated Laguerre polynomials). Gaussian fluctuations around the limit have been known as well. This paper aims to study a dynamical version of those results. More precisely, we study beta Dyson's Brownian motions and beta Laguerre processes and establish LLNs and CLTs for their moment processes in the same regime.

math.PR↗
arXiv2023

Top to random shuffles on colored permutations

A deck of $n$ cards are shuffled by repeatedly taking off the top card, flipping it with probability $1/2$, and inserting it back into the deck at a random position. This process can be considered as a Markov chain on the group $B_n$ of signed permutations. We show that the eigenvalues of the transition probability matrix are $0,1/n,2/n,\ldots,(n-1)/n,1$ and the multiplicity of the eigenvalue $i/n$ is equal to the number of the {\em signed} permutation having exactly $i$ fixed points. We show the similar results also for the colored permutations. Further, we show that the mixing time of this Markov chain is $n\log n$, same as the ordinary 'top-to-random' shuffles without flipping the cards. The cut-off is also analyzed by using the asymptotic behavior of the Stirling numbers of the second kind.

math.CO↗
arXiv2023

Limiting distribution of extremal eigenvalues of d-dimensional random Schrödinger operator

We consider Schrödinger operator with random decaying potential on $\ell^2 ({\bf Z}^d)$ and showed that, (i) IDS coincides with that of free Laplacian in general cases, and (ii) the set of extremal eigenvalues, after rescaling, converges to a inhomogeneous Poisson process, under certain condition on the single-site distribution, and (iii) there are "border-line" cases, such that we have Poisson statistics in the sense of (ii) above if the potential does not decay, while we do not if the potential does decay.

math-ph↗
arXiv2022

Eigenvalue Fluctuations of 1-dimensional random Schrödinger operators

As an extension to the paper by Breuer, Grinshpon, and White \cite{B}, we study the linear statistics for the eigenvalues of the Schrödinger operator with random decaying potential with order ${\cal O}(x^{-α})$ ($α>0$) at infinity. We first prove similar statements as in \cite{B} for the trace of $f(H)$, where $f$ belongs to a class of analytic functions : there exists a critical exponent $α_c$ such that the fluctuation of the trace of $f(H)$ converges in probability for $α> α_c$, and satisfies a CLT statement for $α\le α_c$, where $α_c$ differs depending on $f$. Furthermore we study the asymptotic behavior of its expectation value.

math-ph↗
arXiv2022

Shape of eigenvectors for the decaying potential model

We consider the 1d Schrödinger operator with decaying random potential, and study the joint scaling limit of the eigenvalues and the measures associated with the corresponding eigenfunctions which is based on the formulation by Rifkind-Virag. As a result, we have completely different behavior depending on the decaying rate $α> 0$ of the potential : the limiting measure is equal to (1) Lebesgue measure for the super-critical case ($α> 1/2$), (2) a measure of which the density has power-law decay with Brownian fluctuation for critical case ($α=1/2$), and (3) the delta measure with its atom being uniformly distributed for the sub-critical case($α<1/2$). This result is consistent with previous study on spectral and statistical properties.

math-ph↗
arXiv2021

Determinantal Formula for Generalized Riffle Shuffle

We consider a generalized riffle shuffle on the colored permutation group $G_{p, n}$ and derive a determinantal formula for the probability of finding descents at given positions, proof of which is based on the bijection between the set of shuffles in question and that of non-intersecting lattice paths.

math.PR↗
arXiv2020

Poisson statistics for beta ensembles on the real line at high temperature

This paper studies beta ensembles on the real line in a high temperature regime, that is, the regime where $βN \to const \in (0, \infty)$, with $N$ the system size and $β$ the inverse temperature. In this regime, the convergence to the equilibrium measure is a consequence of a recent result on large deviation principle by Liu and Wu (Stochastic Processes and their Applications (2019)). This paper focuses on the local behavior and shows that the local statistics around any fixed reference energy converges weakly to a homogeneous Poisson point process.

math.PR↗
arXiv2019

A self-adjointness criterion for the Schrödinger operator with infinitely many point interactions and its application to random operators

We prove the Schrödinger operator with infinitely many point interactions in $\mathbb{R}^d$ $(d=1,2,3)$ is self-adjoint if the support of the interactions is decomposed into uniformly discrete clusters. Using this fact, we prove the self-adjointness of the Schrödinger operator with point interactions on a random perturbation of a lattice or on the Poisson configuration. We also determine the spectrum of the Schrödinger operators with random point interactions of Poisson--Anderson type.

math-ph↗
arXiv2017

Gaussian beta ensembles at high temperature: eigenvalue fluctuations and bulk statistics

We study the limiting behavior of Gaussian beta ensembles in the regime where $βn = const$ as $n \to \infty$. The results are (1) Gaussian fluctuations for linear statistics of the eigenvalues, and (2) Poisson convergence of the bulk statistics. (2) is an alternative proof of the result by F.~Benaych-Georges and S.~Péché (2015) with the explicit form of the intensity measure.

math.PR↗