arXiv subjects

Gareth Arturo Marks

Publications and source records attributed to Gareth Arturo Marks.

7 recordsLinked to original sources

arXiv2026

Black Hole-Boson Star Binaries: Gravitational Wave Signals and Tidal Disruption

We present a detailed, fully nonlinear study of binary systems involving one black hole and one boson star, considering the effects of both a quartic self-interaction and a solitonic potential for the scalar field. First, we show the importance of using initial data for which the boson star is in an equilibrated configuration to obtain accurate gravitational waveforms, and discuss methods to further improve constraint violations in the initial data. We then present a series of head-on collisions, showing that even in this simplified scenario the radiative efficiency varies significantly with the scalar potential chosen. In addition to this, we present a preliminary study of inspiral configurations, showing that an appropriate scalar self-interaction can suppress tidal disruption. We comment throughout on implications for attempts to build model-agnostic waveform template banks for exotic compact objects.

gr-qc↗

arXiv2026

Stability and Formation of Solitonic Boson Stars

We extend a previous study of the radial stability of solitonic boson stars by nonlinearly evolving them under aspherical perturbations, and by studying their formation from the collapse of scalar clouds. We focus in particular on models previously identified as radially stable, despite having positive binding energy, which ordinarily suggests that dispersion of all scalar matter is energetically preferred. A mode analysis of our 3+1 evolutions produces no evidence for the presence of a non-radial instability in any radially stable model, including those with positive binding energy. However, we do find evidence that such models do not generically form via gravitational cooling. We also find that it is possible to form another kind of compact object, which undergoes long-lasting radial oscillations and hence cannot be described as a stationary boson star. These objects may be characterized, we suggest, by energetically favoured multi-oscillating solutions to the Einstein-Klein-Gordon equations, present in certain regions of the parameter space.

gr-qc↗

arXiv2026

Long-term stable nonlinear evolutions of ultracompact black-hole mimickers

We study the stability of ultracompact boson stars admitting light rings combining a perturbative analysis with 3+1 numerical-relativity simulations with and without symmetry assumptions. We observe excellent agreement between all perturbative and numerical results which uniformly support the hypothesis that this family of black-hole mimickers is separated into stable and unstable branches by extremal-mass configurations. This separation includes, in particular, thin-shell boson stars with light rings located on the stable branch which we conclude to represent long-term stable black-hole mimickers.

gr-qc↗

arXiv2026

Boson Stars in $D \ge 4$ Dimensions: Stability, Oscillation Frequencies, and Dynamical Evolutions

We construct spherically symmetric boson star solutions in $D \in \{4,5,6\}$ spacetime dimensions, considering the effects of both a quartic self-interaction term and a solitonic potential. We then perform a perturbative analysis, generalizing the pulsation equations to arbitrary dimension and potential and hence demonstrating the existence of radially stable higher-dimensional boson star solutions. In particular, we find stable solutions for $D \in {5, 6}$ with a quartic self-interaction term and for $D = 5$ with a solitonic potential We supplement these linear results with perturbed and unperturbed nonlinear dynamical evolutions in spherical symmetry, obtained using a dimensional reduction that allows us to evolve spacetimes with any number of background dimensions using the same numerical framework, while preserving the full gauge freedom of standard approaches to numerical relativity. The results of these evolutions indicate that the solutions we identify as perturbatively stable are indeed generally stable to nonlinear spherical dynamics.

gr-qc↗

arXiv2026

Perturbations of Solitonic Boson Stars: Nonlinear Radial Stability and Binding Energy

We study the nonlinear radial stability of boson stars with a solitonic potential across the entire parameter space, focusing especially on families of solutions that support ultracompact models on the perturbatively stable branch. Using a dimensional reduction of the CCZ4 formulation of numerical relativity, we dynamically evolve these models with both internal and external perturbations. We find in particular that there are perturbatively stable models with positive binding energy that do not effectively disperse even under explicit perturbations, challenging the conventional wisdom that negative binding energy is a necessary condition for the dynamical stability of boson stars and other compact objects.

gr-qc↗

arXiv2023

Slowly Rotating Black Holes in Einsteinian Quartic Gravities

We study slowly rotating black hole solutions in the six independent theories of Einstein Quartic Gravity (EQG) in four dimensions. Unlike in the static case for which all six theories yield the same solution, for rotating black holes we obtain distinct results for five out of the six theories. Working to leading order in the rotation parameter, we find that the equations characterizing these black holes can be reduced to second order for each theory, similar to what has already been done for Einstein Cubic Gravity. We construct approximate and numerical solutions to these equations, and study how physical properties of the solutions such as the angular velocity, photon sphere, black hole shadow, and innermost stable circular orbit are modified, working to leading order in the coupling constant.

gr-qc↗

arXiv2021

Phase Transitions in 4D Gauss-Bonnet-de Sitter Black Holes

We investigate thermodynamic aspects of black holes in the recently formulated four dimensional Gauss-Bonnet theory of gravity, focusing on its asymptotically de Sitter ($Λ>0$) solutions. We take a Euclidean path integral approach, where thermodynamic data is fixed at a finite radius `cavity' outside the black hole to achieve equilibrium in the presence of the cosmological horizon. Working in the extended phase space where the cosmological constant is treated as a thermodynamic pressure, we study the phase structure of both uncharged and charged solutions, uncovering a wealth of phenomena. In the uncharged case, black holes are found to undergo either the standard Hawking-Page-like transition to empty de Sitter space or a small-large transition (akin to those seen in charged AdS black holes in pure Einstein gravity) depending on the pressure. We also find a triple point where the radiation, small, and large black hole phases coexist, and a zeroth-order phase transition within a narrow range of Gauss-Bonnet coupling parameter. Reentrant phase transitions between radiation and a small black hole also exist inside a certain parameter range. Similar phenomena are found in the charged case, with the charge parameter playing a role analogous to the Gauss-Bonnet coupling parameter in determining the phase structure.

gr-qc↗