arXiv subjects

Martin Teuscher

Publications and source records attributed to Martin Teuscher.

6 recordsLinked to original sources

arXiv2026

Large deviations for halos and voids: beyond perturbative non-gaussianities

The excursion-set formalism provides a key connection between primordial density fluctuations and the abundance of cosmic structures such as dark matter halos and voids, traditionally assuming Gaussian random walks. In this work, we extend this framework to fluctuations whose distribution presents strongly non-Gaussian tails. Such tails are beyond the reach of perturbative approaches to primordial non-Gaussianity based on moment expansion. We address the problem with rigorous, analytical derivations relying on the large deviation principle, suited for the study of rare fluctuations. We derive new first-passage time distributions for random walks with non-Gaussian statistics and obtain updated predictions for the halo mass function. We also study the two-barrier problem relevant to cosmic void formation, leading to a new analytical prediction for the void size function, with improved accuracy on large scales. Our results demonstrate the potential of large deviation techniques as a bridge between inflationary scenarios, often leading to strongly non-Gaussian tails, and late-Universe observables.

astro-ph.CO↗

arXiv2025

A universal scaling law for gravitational waves induced during inflation

We consider the stochastic gravitational wave background induced by arbitrary source fields that are amplified during cosmological inflation. The associated tensor spectral index is shown to be given, under minimal assumptions, by a simple formula easy to apply in most situations of accelerated expansion. For slow-roll inflation, the induced spectrum is nearly scale invariant, with an index deviating from the standard outcome of vacuum generated gravitational waves. Remarkably, we demonstrate that scale invariance remains true regardless of the original spectrum of the source. We show how this generic approach reproduces the literature on specific models of gravitational wave primordial sources, and discuss its limitations. It provides a very practical estimation of the tensor spectral index for future models, to which subleading corrections can then be added.

astro-ph.CO↗

arXiv2025

Gravitational Waves sourced by Gauge Fields during Inflation

We study the inflationary gravitational wave background induced by Abelian gauge fields generated by non-minimal kinetic and axial couplings to the inflaton. We show that, up to slow-roll corrections, for coupling functions that share the same dependence on conformal time, the gravitational wave spectrum is nearly scale invariant. We also derive its amplitude for generic gauge field coupling parameters, within the slow-roll approximation. The coupling values and the scale of inflation for which the induced gravitational wave background is observable, while ensuring that back-reaction on the inflationary dynamics remains negligible, are calculated. We find that a sizeable axial coupling can boost this secondary gravitational wave signal above the standard inflationary background. In the course of our analysis, we also show how to analytically match tensor perturbations across an arbitrary number of eras with different equations of state.

astro-ph.CO↗

arXiv2024

Prospects for detection of ultra high frequency gravitational waves from hyperbolic encounters with resonant cavities

In this brief article, we pursue the systematic investigation of possible gravitational wave sources in the gigahertz band. We focus on hyperbolic encounters of light black holes and evaluate precisely the expected signal when accounting for the detailed characteristics of haloscope experiments. Considering the GraHal setup as a benchmark, we insist on the correct signal-to-noise ratio expression, taking into account the appropriate timescales resulting from both physical and instrumental constraints. The associated maximum distance - of the order of a hundredth of an astronomical unit - at which an event can be detected is calculated for optimal, suboptimal, and general trajectories. The main conclusion is that detection seems clearly out of reach.

gr-qc↗

arXiv2024

Elementary considerations on gravitational waves from hyperbolic encounters

We examine the main properties of gravitational waves (GWs) emitted by transient hyperbolic encounters of black holes. We begin by building the set of basic variables most relevant to setting our problem. After exposing the ranges of masses and eccentricities accessible at a given GW frequency, we analyze the dependence of the gravitational strain on those parameters and determine the trajectories resulting in the most sizeable strains. Some non-trivial behaviors are unveiled, showing that highly eccentric events can be more easily detectable than parabolic ones. In particular, we underline the correct way to extend formulas from hyperbolic to parabolic orbits. Our reasonings are as general as possible, and we make a point of explaining our considerations pedagogically. The majority of the work is based on Newtonian dynamics and aims at being a benchmark to which more accurate calculations can be compared.

gr-qc↗

arXiv2022

The Big Bang as a Mirror: a Solution of the Strong CP Problem

We argue that the Big Bang can be understood as a type of mirror. We show how reflecting boundary conditions for spinors and higher spin fields are fixed by local Lorentz and gauge symmetry, and how a temporal mirror (like the Bang) differs from a spatial mirror (like the AdS boundary), providing a possible explanation for the observed pattern of left- and right-handed fermions. By regarding the Standard Model as the limit of a minimal left-right symmetric theory, we obtain a new, cosmological solution of the strong $CP$ problem, without an axion.

hep-ph↗