arXiv subjects

Hugh Geller

Publications and source records attributed to Hugh Geller.

6 recordsLinked to original sources

arXiv2026

Betti numbers of inductively pierced codes

Neural ideals were introduced by Curto, Itskov, et al as an algebraic tool to study neural codes. In this paper, we use the notion of polarization introduced by G\"{u}nt\"{u}rk\"{u}n, Jeffries, and Sun to compute Betti numbers of inductively pierced neural codes. We prove that quadratically generated neural ideals are inductively pierced if and only if they have regularity 2. Further, we demonstrate how the Betti numbers yield information on the number and type of piercings of the original code. This work shows the utility of algebraic invariants of the neural ideal in detecting geometric features of the associated receptive fields.

math.AC↗

arXiv2025

DG-Sensitive Pruning & a Complete Classification of DG Trees and Cycles

Given a squarefree monomial ideal $I$ of a polynomial ring $Q$, we show that if the minimal free resolution $\mathbb{F}$ of $Q/I$ admits the structure of a differential graded (dg) algebra, then so does any ``pruning" of $\mathbb{F}$. In the language of combinatorics, this says that if $Q/\mathcal{F}(\Delta)$, the quotient of the ambient polynomial ring by the facet ideal $\mathcal{F}(\Delta)$ of a simplicial complex $\Delta$, is minimally resolved by a dg algebra, then so is the quotient by the facet ideal of each facet-induced subcomplex of $\Delta$ (over the smaller polynomial ring). Along with techniques from discrete Morse theory and homological algebra, this allows us to give complete classifications of the trees and cycles $G$ with $Q/I(G)$ minimally resolved by a dg algebra in terms of the length of the longest path in $G$, where $I(G)$ is the edge ideal of $G$.

math.AC↗

arXiv2023

Classifying Betti Numbers of Fiber Products

We consider fiber products of complete, local, noetherian algebras over a fixed residue field. Some of these rings cannot be minimally resolved with a free resolution using the recent work of the second author. We develop techniques to modify Geller's approach in order to recover the Betti numbers and Poincaré series for these fiber products.

math.AC↗

arXiv2023

Semidualizing Modules over Numerical Semigroup Rings

A semidualizing module is a generalization of Grothendieck's dualizing module. For a local Cohen-Macaulay ring $R$, the ring itself and its canonical module are always realized as (trivial) semidualizing modules. Reasonably, one might ponder the question; when do nontrivial examples exist? In this paper, we study this question in the realm of numerical semigroup rings and completely classify which of these rings with multiplicity at most 9 possess a nontrivial semidualizing module. Using this classification, we construct numerical semigroup rings in any multiplicity at least 9 possesses a nontrivial semidualizing module.

math.AC↗

arXiv2022

Canonical forms of neural ideals

Neural ideals, originally defined in arXiv:1212.4201, give a way of translating information about the firing pattern of a set of neurons into a pseudomonomial ideal in a polynomial ring. We give a simple criterion for determining whether a neural ideal is in canonical form, along with an improved algorithm for computing the canonical form of a neural ideal.

math.AC↗

arXiv2021

Minimal Free Resolutions of Fiber Products

We construct free resolutions for quotient rings $R/\langle \mathcal{I}', \mathcal{I}\mathcal{J}, \mathcal{J}'\rangle$, give conditions for the quotient to be realized as a fiber product, and give criteria for the construction to be minimal. We then specialize this result to fiber products over a field $k$ and recover explicit formulas for Betti numbers, graded Betti numbers, and Poincaré series.

math.AC↗