arXiv subjects

Gareth Amery

Publications and source records attributed to Gareth Amery.

4 recordsLinked to original sources

arXiv2026

Temperature of free gravitational field: A geometrical perspective

In this paper, using a novel geometrical approach, we relate the concept of the thermodynamic temperature of the free gravitational field, to the non-affinity of real null geodesics in a Newman Penrose tetrad. This naturally links various temperature functions like Clifton, Ellis and Tavakol temperature, Hawking temperature, Unruh temperature etc., in their respective proper limits. Although our analysis is done within the realm of local rotational symmetry, we show that the result can be extended to other Petrov type D geometries, like the Kerr spacetime. We also obtain the geometrical and causal transport equations for this temperature function, in the form of a hyperbolic wave equation with a forcing term, sourced by Weyl curvature and matter. Finally, as a possible physical interpretation of the non-affinity, we relate the geometrical temperature with the gravitational red/blue shift of light rays travelling along null geodesics.

gr-qc↗

arXiv2026

Ricci-Weyl curvature balance in viscous dissipative collapse: A covariant analysis of singularity censorship

We investigate the cosmic censorship conjecture in a spherically symmetric collapse with shear and bulk viscosity, heat flux, and pressure anisotropy, imposing physically reasonable energy conditions. Using the semi-tetrad covariant formalism, we derive the dynamics of the collapsing fluid, including a master equation for the evolution of the Weyl curvature, to examine the role of viscosity. The analysis of null geodesic geometry uncovers a novel curvature-balance mechanism between Ricci (matter) and Weyl (free gravitational field) curvature on the apparent horizon; this balance determines the causal nature of the horizon and thereby governs the visibility of the singularity. We then derive necessary and sufficient covariant conditions for the central singularity to be locally naked. Our findings support a weaker form of cosmic censorship and extend the covariant censorship analysis to realistic dissipative, viscous collapse.

gr-qc↗

arXiv2024

Gradient conformal stationarity and the CMC condition in LRS spacetimes

We study the existence of gradient conformal Killing vectors (CKVs) in the class of locally rotationally symmetric (LRS) spacetimes which generalizes spherically symmetric spacetimes, and investigate some implications for the evolutionary character of marginally outer trapped surfaces. We first study existence of gradient CKVs via the obtention of a relationship between the Ricci curvature and the gradient of the divergence of the CKV. This provides an alternative set of equations, for which the integrability condition is obtained, to analyze the existence of gradient CKVs. A uniqueness result is obtained in the case of perfect fluids, where it is demonstrated that the Robertson-Walker solution is the unique perfect fluid solution with a nonvanishing pressure, admitting a timelike gradient CKV. The constant mean curvature condition for LRS spacetimes is also obtained, characterized by three distinct conditions which are specified by a set of three scalars. Linear combinations of these scalars, whose vanishing define the constant mean curvature condition, turn out to be related to the evolutions of null expansions of 2-spheres along their null normal directions. As such, some implications for the existence of black holes and the character of the associated horizons are obtained. It is further shown that dynamical black holes of increasing area, with a non-vanishing heat flux across the horizon, will be in equilibrium, with respect to the frame of the conformal observers.

gr-qc↗

arXiv2020

Relating a Geroch-like boundary and the abstract boundary constructions for spacetimes

We construct a Geroch-like boundary (when restricted to geodesic curves, this boundary contains as a subset the Geroch's $g$ boundary), which we denote by $\tilde{g}$, and establish an explicit embedding of the $\tilde{g}$ boundary into the $a$ boundary of Scott and Szekeres. This construction, and subsequently the explicit embedding, is done in a 'natural' way (the emphasis on the word natural here will be clarified in the text), thereby answering in the affirmative the outstanding question as to whether there exists a natural way to relate the $g$ and the $a$ boundary constructions.

gr-qc↗