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Black holes in multimetric gravity. II. Hairy solutions and linear stability of the non- and partially proportional branches (2025)
Journal Article
Wood, K., Saffin, P. M., & Avgoustidis, A. (2025). Black holes in multimetric gravity. II. Hairy solutions and linear stability of the non- and partially proportional branches. Physical Review D, 111(2), Article 024057. https://doi.org/10.1103/PhysRevD.111.024057

Owing to our work in part I of this series of papers, it is understood that the analytically known black hole solutions in the theory of ghost-free multimetric gravity can be split into three distinct classes and that one of these classes—the proport... Read More about Black holes in multimetric gravity. II. Hairy solutions and linear stability of the non- and partially proportional branches.

Black holes in multimetric gravity (2024)
Journal Article
Wood, K., Saffin, P. M., & Avgoustidis, A. (2024). Black holes in multimetric gravity. Physical Review D, 109(12), Article 124006. https://doi.org/10.1103/physrevd.109.124006

We construct a wide class of black hole solutions to the general theory of ghost-free multimetric gravity in arbitrary spacetime dimension, extending and generalizing the known results in four-dimensional dRGT massive gravity and bigravity. The solut... Read More about Black holes in multimetric gravity.

Cosmology with the Laser Interferometer Space Antenna (2023)
Journal Article
Auclair, P., Bacon, D., Baker, T., Barreiro, T., Bartolo, N., Belgacem, E., Bellomo, N., Ben-Dayan, I., Bertacca, D., Besancon, M., Blanco-Pillado, J. J., Blas, D., Boileau, G., Calcagni, G., Caldwell, R., Caprini, C., Carbone, C., Chang, C.-F., Chen, H.-Y., Christensen, N., …Zhdanov, V. I. (2023). Cosmology with the Laser Interferometer Space Antenna. Living Reviews in Relativity, 26, Article 5. https://doi.org/10.1007/s41114-023-00045-2

The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and... Read More about Cosmology with the Laser Interferometer Space Antenna.

Clockwork cosmology (2023)
Journal Article
Wood, K., Saffin, P. M., & Avgoustidis, A. (2023). Clockwork cosmology. Journal of Cosmology and Astroparticle Physics, 2023(07), Article 062. https://doi.org/10.1088/1475-7516/2023/07/062

The higher order generalisation of the clockwork mechanism to gravitational interactions provides a means to generate an exponentially suppressed coupling to matter from a fundamental theory of multiple interacting gravitons, without introducing larg... Read More about Clockwork cosmology.

Deconstructing higher order clockwork gravity (2021)
Journal Article
Avgoustidis, A., Niedermann, F., Padilla, A., & Saffin, P. M. (2021). Deconstructing higher order clockwork gravity. Physical Review D, 103(12), Article 124007. https://doi.org/10.1103/physrevd.103.124007

We consider the higher order clockwork theory of gravitational interactions, whereby a number of gravitons are coupled together with TeV strength, but nevertheless generate a Planck scale coupling to matter without the need for a dilaton. It is shown... Read More about Deconstructing higher order clockwork gravity.

Understanding the suppression of structure formation from dark matter-dark energy momentum coupling (2020)
Journal Article
Chamings, F. N., Avgoustidis, A., Copeland, E. J., Green, A. M., & Pourtsidou, A. (2020). Understanding the suppression of structure formation from dark matter-dark energy momentum coupling. Physical Review D, 101(4), https://doi.org/10.1103/physrevd.101.043531

Models in which scalar field dark energy interacts with dark matter via a pure momentum coupling have previously been found to potentially ease the structure formation tension between early-and late-universe observations. In this article we explore t... Read More about Understanding the suppression of structure formation from dark matter-dark energy momentum coupling.

Cosmological evolution of semilocal string networks (2019)
Journal Article
Achúcarro, A., Avgoustidis, A., López-Eiguren, A., Martins, C. J. A. P., & Urrestilla, J. (2019). Cosmological evolution of semilocal string networks. Philosophical Transactions A: Mathematical, Physical and Engineering Sciences, 377(2161), 1-11. https://doi.org/10.1098/rsta.2019.0004

Semilocal strings—a particular limit of electroweak strings—are an interesting example of a stable non-topological defect whose properties resemble those of their topological cousins, the Abrikosov–Nielsen–Olesen vortices. There is, however, one impo... Read More about Cosmological evolution of semilocal string networks.

Early dark energy constraints on growing neutrino quintessence cosmologies (2019)
Journal Article
Noble Chamings, F., Avgoustidis, A., Copeland, E. J., Green, A. M., & Li, B. (2019). Early dark energy constraints on growing neutrino quintessence cosmologies. Physical Review D, 100(4), https://doi.org/10.1103/physrevd.100.043525

We investigate cosmological models in which dynamical dark energy consists of a scalar field whose present-day value is controlled by a coupling to the neutrino sector. The behavior of the scalar field depends on three functions: a kinetic function,... Read More about Early dark energy constraints on growing neutrino quintessence cosmologies.

Analog cosmology with two-fluid systems in a strong gradient magnetic field (2019)
Journal Article
Fifer, Z., Torres, T., Erne, S., Avgoustidis, A., Hill, R. J. A., & Weinfurtner, S. (2019). Analog cosmology with two-fluid systems in a strong gradient magnetic field. Physical Review E, 99(3), Article 031101(R). https://doi.org/10.1103/physreve.99.031101

We propose an experiment combining fluid dynamics and strong magnetic field physics to simulate cosmological scenarios. Our proposed system consists of two immiscible, weakly magnetized fluids moved through a strong gradient magnetic field. The diama... Read More about Analog cosmology with two-fluid systems in a strong gradient magnetic field.