arXiv subjects

Lewis Croney

Publications and source records attributed to Lewis Croney.

4 recordsLinked to original sources

arXiv2026

Properties of black holes in non-linear electrodynamics

We investigate the properties of charged black hole geometries in nonlinear electrodynamics. We focus on the recently reported analytic charged black hole solutions to illustrate the consequences of a non-monotonic lapse function that exists for a wide range of black hole solutions. The spacetime admits stable light-rings, static near-horizon observers, and trapped near horizon photon orbits. We also show that although these modifications near the horizon are screened from afar, they nonetheless lead to additional branches of quasinormal modes for the black hole that are longer lived than the canonical Einstein branches.

hep-th↗

arXiv2025

Thermodynamics of dyonic black holes in non-linear electrodynamics

We investigate dyonic black holes in a weak field expansion of non-linear electrodynamics. The breadth of parameter space permits a rich thermodynamic structure, additional turning points and intricate phase phenomena. Energy conditions are employed to ensure the physical viability of solutions. Analytic special cases illustrate novel properties of black holes in non-linear electrodynamics, including modified extremal limit behaviour. Numerical solutions offer the most elaborate thermodynamic landscape, culminating in up to five turning points, and multiple reentrant phase transitions.

hep-th↗

arXiv2024

Ultra slow-roll with a black hole

We investigate ultra slow-roll inflation with a seed black hole in a de Sitter background. By numerically tracking transitions from slow-roll to ultra slow-roll inflation, we find that quasi-normal mode solutions of the scalar field are excited following the decay of the slow-roll attractor, depending on the mass of the black hole. For small black holes, the picture is similar to standard inflation with the usual damping of the scalar field; with a large black hole, we find that the ringing modes dominate. It is believed that the transition to ultra slow-roll in the pure inflationary case enhances the peak of the primordial power spectrum, thereby increasing the likelihood of primordial black hole formation. We comment on how the novel ringing behaviour due to the seed black hole might impact on cosmological perturbations.

hep-th↗

arXiv2023

Renormalisation group flows connecting a $4-\epsilon$ dimensional Hermitian field theory to a $\mathcal{PT}$-symmetric theory for a fermion coupled to an axion

The renormalisation group flow of a Hermitian field theory is shown to have trajectories which lead to a non-Hermitian Parity-Time ($\mathcal{PT}$) symmetric field theory for an axion coupled to a fermion in spacetime dimensions $D=4-\epsilon$, where $\epsilon >0 $. In this renormalisable field theory, the Dirac fermion field has a Yukawa coupling $g$ to a pseudoscalar (axion) field and there is quartic pseudoscalar self-coupling $u$. The robustness of this finding is established by considering flows between $\epsilon$ dpependent Wilson-Fisher fixed points and also by working to \emph{three loops} in the Yukawa coupling and to \emph{two loops} in the quartic scalar coupling. The flows in the neighbourhood of the non-trivial fixed points are calculated using perturbative analysis, together with the $\epsilon$ expansion. The global flow pattern indicates flows from positive $u$ to negative $u$; there are no flows between real and imaginary $g$. Using summation techniques we demonstrate a possible non-perturbative $\mathcal{PT}$-symmetric saddle point for $D=3$.

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