arXiv subjects

Jacob Campbell

Publications and source records attributed to Jacob Campbell.

5 recordsLinked to original sources

arXiv2025

Statistics on monotonically ordered non-crossing partitions

We study some combinatorial statistics defined on the set $NC^{(mton)}(n)$ of monotonically ordered non-crossing partitions of {1,...,n}, and on the set $NC_2^{(mton)}(2n)$ of monotonically ordered non-crossing pair-partitions of {1,...,2n}. Unlike in the analogous results known for unordered non-crossing partitions, the computations of expectations and variances for natural block-counting statistics on $NC^{(mton)}(n)$ and for the expectation of the area statistic on $NC_2^{(mton)}(2n)$ turn out to yield a logarithmic regime. An important role in our study is played by a nice tree structure on the disjoint union of the $NC^{(mton)}(n)$'s, which we use to streamline our arguments. As an illustration of how these ideas can be applied to calculations of cumulants in monotone probability, we discuss some combinatorial aspects of the monotonic Poisson process.

math.CO↗

arXiv2025

Even Hypergeometric Polynomials and Finite Free Commutators

We study in detail the class of even polynomials and their behavior with respect to finite free convolutions. To this end, we use some specific hypergeometric polynomials and a variation of the rectangular finite free convolution to understand even real-rooted polynomials in terms of positive-rooted polynomials. Then, we study some classes of even polynomials that are of interest in finite free probability, such as even hypergeometric polynomials, symmetrizations, and finite free commutators. Specifically, we provide many new examples of these objects, involving classical families of special polynomials (such as Laguerre, Hermite, and Jacobi). Finally, we relate the limiting root distributions of sequences of even polynomials with the corresponding symmetric measures that arise in free probability.

math.CA↗

arXiv2022

Commutators in finite free probability, I

This paper describes the expected characteristic polynomial of the commutator of randomly rotated matrices, in the context of the finite free probability theory initiated by Marcus, Spielman, and Srivastava. The key technical features are the use of Weingarten calculus to translate the random matrix problem into one of combinatorial representation theory, followed by some applications of the Goulden-Jackson immanant formula and the classical theory of permutation modules.

math.CO↗

arXiv2022

A central limit theorem for star-generators of $S_{\infty}$, which relates to traceless CCR-GUE matrices

We prove a limit theorem concerning the sequence of star-generators of $S_{\infty}$, where the expectation functional is provided by a character of $S_{\infty}$ with weights $(w_1, \ldots , w_d, 0,0, \ldots )$ in the Thoma classification. The limit law turns out to be the law of a "traceless CCR-GUE" matrix, an analogue of the traceless GUE where the off-diagonal entries $g_{i,j}$ satisfy the commutation relation $g_{i,j}g_{j,i} = g_{j,i}g_{i,j} + (w_j - w_i)$. The special case $w_1 = \cdots = w_d = 1/d$ yields the law of a bona fide traceless GUE matrix, and we retrieve a result of K\"ostler and Nica from 2021, which in turn extended a result of Biane from 1995.

math.PR↗

arXiv2019

Finite free convolutions via Weingarten calculus

We consider the three finite free convolutions for polynomials studied in a recent paper by Marcus, Spielman, and Srivastava. Each can be described either by direct explicit formulae or in terms of operations on randomly rotated matrices. We present an alternate approach to the equivalence between these descriptions, based on combinatorial Weingarten methods for integration over the unitary and orthogonal groups. A key aspect of our approach is to identify a certain \emph{quadrature property}, which is satisfied by some important series of subgroups of the unitary groups (including the groups of unitary, orthogonal, and signed permutation matrices), and which yields the desired convolution formulae.

math.CO↗