arXiv subjects

Sebastian Vander Ploeg Fallon

Publications and source records attributed to Sebastian Vander Ploeg Fallon.

4 recordsLinked to original sources

arXiv2026

Nonlinear Stability of Kerr-Sen Black Holes in Merging Binaries

We investigate the stability of Kerr-Sen black holes, which arise in Einstein-Maxwell-dilaton-axion theory. Within a numerical relativity framework, we perform head-on binary black hole simulations with approximate initial data across a portion of the parameter space. We find that for nontrivial electric charge, a dilaton field persists through merger and that in the presence of spin, the remnant will also retain an axion field. The persistence of these fields for long times after merger strongly suggests the stability of these black holes within this alternative gravity theory. We further test whether initially unscalarized black holes will acquire hair in the presence of a scalar background. We find that black holes immersed in such a background retain scalar hair. Furthermore, we find that even initially unscalarized Kerr-Newman black holes will scalarize and remain scalarized throughout the evolution.

gr-qc↗

arXiv2026

A Supernova Constraint on F-theory

We study constraints on the quantum chromodynamics (QCD) axion in F-theory, a strongly coupled limit of string theory. We build models of QCD from compactifications to four dimensions on elliptic fibrations over toric threefolds $B_3$, characterized by an integer $N=h^{1,1}(B_3)$. The QCD axion mass increases with $N$, and we find that models with sufficiently high $N$ are inconsistent with observations of the neutrino burst from supernova 1987A, disfavoring large regions of the moduli space. Specifically, at least $95\%$ of models with $N \ge 8,791$ -- a regime that arguably contains the vast majority of known F-theory topologies -- have a QCD axion mass $m_{QCD}>15~meV$ and are thus constrained. This limit is independent of cosmology. We only consider weakly-curved threefolds, where $α'$ corrections are plausibly negligible.

hep-th↗

arXiv2026

A model for horizontally restricted random square-tiled surfaces

A square-tiled surface (STS) is a (finite, possibly branched) cover of the standard square-torus with possible branching over exactly 1 point. Alternately, STSs can be viewed as finitely many axis-parallel squares with sides glued in parallel pairs. After a labelling of the squares by $\{1, \dots, n\}$, we can describe an STS with $n$ squares using two permutations $σ, τ\in S_n$, where $σ$ encodes how the squares are glued horizontally and $τ$ encodes how the squares are glued vertically. Hence, a previously considered natural model for STSs with $n$ squares is $S_n \times S_n$ with the uniform distribution. We modify this model to obtain a new one: We fix $α\in [0,1]$ and let $\mathcal{K}_{μ_n}$ be a conjugacy class of $S_n$ with at most $n^α$ cycles. Then $\mathcal{K}_{μ_n} \times S_n$ with the uniform distribution is a model for STSs with restricted horizontal gluings. Since horizontal cycles of the $σ$ permutation are related to the number of maximal horizontal cylinders, this new model serves as a random model for STSs with at most $n^α$ maximal horizontal cylinders. We deduce the asymptotic (as $n$ grows) number of components, genus distribution, most likely stratum and set of holonomy vectors of saddle connections for random STSs in this new model.

math.GT↗

arXiv2025

F-theory Axiverse

We compute the couplings of Ramond-Ramond four-form axions in three ensembles of F-theory compactifications, with up to 181,200 axions. We work in the stretched Kähler cone, where $α'$ corrections are plausibly controlled, and we use couplings to certain non-Abelian sectors as a proxy for couplings to photons. The axion masses, decay constants, and couplings to gauge sectors show striking universality across the ensembles. In particular, the axion-photon couplings grow with $h^{1,1}$, and models in our ensemble with $h^{1,1} \gtrsim$ 10,000 axions are in tension with helioscope constraints. Moreover, under mild assumptions about charged matter beyond the Standard Model, theories with $h^{1,1} \gtrsim$ 5,000 are in tension with Chandra measurements of X-ray spectra. This work is a first step toward understanding the phenomenology of quantum gravity theories with thousands of axions.

hep-th↗