arXiv subjects

Guillaume Lhost

Publications and source records attributed to Guillaume Lhost.

4 recordsLinked to original sources

arXiv2026

A Plunge into the Chasm: Surviving Tidal Effects in Kerr Spacetime

We investigate the fate of an observer falling towards a Kerr black hole. The tidal forces are computed for arbitrary trajectories of an observer, and we specify them along the polar axis in order to remain as far as possible from the ring-shaped singularity. Our analysis shows that an observer is not tidally disrupted during the fall provided that the black hole mass exceeds a critical value, which depends on its spin. In practice, any supermassive black hole represents a suitable candidate to allow an observer to traverse the black hole without severe deformation. In contrast, stellar-mass rotating black holes do not satisfy the mass condition and are expected to subject the observer to extreme tidal forces leading to its destruction during the plunge.

gr-qc↗

arXiv2024

A note on partially massless supergravity

We analyse the couplings of a partially massless spin-2 field with a doublet of massless, real spin-3/2 fields. In the flat limit, this spectrum coincides with the spectrum of ${\cal N}=2$ pure supergravity around anti-de Sitter spacetime AdS$_4$. We classify all the possible parity-invariant, non-Abelian deformations of the free theory that lead to a deformation of the Lagrangian. By doing this, we re-derive a non-Abelian vertex recently found in 2412.04982 [hep-th] by Yu. M. Zinoviev following a different approach, and show that the corresponding non-Abelian gauge algebra closely resembles the one of ${\cal N}=2$ supergravity around AdS$_4$. The gauge-algebra deformation is however obstructed, at next order. Then, we add a massless vector field together with a massive spin-3/2 field, and find two nontrivial vertices mixing these fields with a single massless gravitino. Still, the gauge algebra remains obstructed at next order, therefore excluding the possibility to make local the global supersymmetry algebra found in recent works on partially massless supermultiplets in AdS$_4$. Finally, we argue that the two problems encountered are simultaneously solved by the addition of the masseless graviton, leading to ${\cal N}=1$ pure conformal supergravity around AdS$_4$ as the only consistent theory coupling partially massless spin-2 fields to massless and massive spin-3/2 fields.

hep-th↗

arXiv2024

Approach to the separatrix with eccentric orbits

Eccentric binary compact mergers are prime targets of current and future gravitational wave observatories. In the small mass ratio expansion, post-adiabatic inspirals have been modeled up to the separatrix, where first-principle modeling currently ends. In this paper, we derive the analytic late time solution to the adiabatic inspiral in terms of self-force coefficients at the separatrix. We identify the role of the Lambert $W_{-1}$ function as a key mathematical ingredient in the approach to the separatrix.

gr-qc↗

arXiv2023

Consistent couplings between a massive spin-3/2 field and a partially massless spin-2 field

We revisit the problem of constructing consistent interactions between a massive spin-3/2 field and a partially massless graviton in four-dimensional (A)dS spacetime. We use the Stueckelberg formulation of the action principle for these fields and find two non-trivial cubic vertices with less than two derivatives, when going to the unitary gauge. One of the vertices is reminiscent of the minimal coupling of the massive spin-3/2 field to gravity, except that now the graviton is partially massless.

hep-th↗