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Black hole thermodynamics with conical defects (2017)
Journal Article
Appels, M., Gregory, R., & Kubiznak, D. (2017). Black hole thermodynamics with conical defects. Journal of High Energy Physics, 2017(5), Article 116. https://doi.org/10.1007/jhep05%282017%29116

Recently we have shown [1] how to formulate a thermodynamic first law for a single (charged) accelerated black hole in AdS space by fixing the conical deficit angles present in the spacetime. Here we show how to generalise this result, formulating th... Read More about Black hole thermodynamics with conical defects.

Black hole accretion discs and screened scalar hair (2016)
Journal Article
Davis, A. C., Gregory, R., & Jha, R. (2016). Black hole accretion discs and screened scalar hair. Journal of Cosmology and Astroparticle Physics, 2016(10), Article 024. https://doi.org/10.1088/1475-7516/2016/10/024

We present a novel way to investigate scalar field profiles around black holes with an accretion disc for a range of models where the Compton wavelength of the scalar is large compared to other length scales. By analysing the problem in ``Weyl" coord... Read More about Black hole accretion discs and screened scalar hair.

Thermodynamics of Accelerating Black Holes (2016)
Journal Article
Appels, M., Gregory, R., & Kubizňák, D. (2016). Thermodynamics of Accelerating Black Holes. Physical Review Letters, 117(13), Article 131303. https://doi.org/10.1103/physrevlett.117.131303

We address a long-standing problem of describing the thermodynamics of a charged accelerating black hole. We derive a standard first law of black hole thermodynamics, with the usual identification of entropy proportional to the area of the event hori... Read More about Thermodynamics of Accelerating Black Holes.

The fate of the Higgs vacuum (2016)
Journal Article
Burda, P., Gregory, R., & Moss, I. (2016). The fate of the Higgs vacuum. Journal of High Energy Physics, 2016(6), Article 25. https://doi.org/10.1007/jhep06%282016%29025

We have recently suggested that tiny black holes can act as nucleation seeds for the decay of the metastable Higgs vacuum. Previous results applied only to the nucleation of thin-wall bubbles, and covered a very small region of parameter space. This... Read More about The fate of the Higgs vacuum.

Vacuum metastability with black holes (2015)
Journal Article
Burda, P., Gregory, R., & Moss, I. (2015). Vacuum metastability with black holes. Journal of High Energy Physics, 2015(8), Article 114. https://doi.org/10.1007/jhep08%282015%29114

We consider the possibility that small black holes can act as nucleation seeds for the decay of a metastable vacuum, focussing particularly on the Higgs potential. Using a thin-wall bubble approximation for the nucleation process, which is possible w... Read More about Vacuum metastability with black holes.

Gravity and the stability of the Higgs vacuum (2015)
Journal Article
Burda, P., Gregory, R., & Moss, I. (2015). Gravity and the stability of the Higgs vacuum. Physical Review Letters, 115(7), Article 071303. https://doi.org/10.1103/physrevlett.115.071303

We discuss the effect of gravitational interactions on the lifetime of the Higgs vacuum where generic quantum gravity corrections are taken into account. Using a “thin-wall” approximation, we provide a proof of principle that small black holes can ac... Read More about Gravity and the stability of the Higgs vacuum.

Lifshitz flows in IIB and dual field theories (2014)
Journal Article
Burda, P., Gregory, R., & Ross, S. (2014). Lifshitz flows in IIB and dual field theories. Journal of High Energy Physics, 2014(11), Article 73. https://doi.org/10.1007/jhep11%282014%29073

We construct solutions describing flows between AdS and Lifshitz spacetimes in IIB supergravity. We find that flows from AdS5 can approach either AdS3 or Lifshitz3 in the IR depending on the values of the deformation from AdS5. Surprisingly, the choi... Read More about Lifshitz flows in IIB and dual field theories.

Vortex Hair on ADS Black Holes (2014)
Journal Article
Gregory, R., Gustainis, P., Kubizňák, D., Mann, R., & Wills, D. (2014). Vortex Hair on ADS Black Holes. Journal of High Energy Physics, 2014(11), Article 10. https://doi.org/10.1007/jhep11%282014%29010

We analyse vortex hair for charged rotating asymptotically AdS black holes in the abelian Higgs model. We give analytical and numerical arguments to show how the vortex interacts with the horizon of the black hole, and how the solution extends to the... Read More about Vortex Hair on ADS Black Holes.

Time dependent black holes and scalar hair (2014)
Journal Article
Chadburn, S., & Gregory, R. (2014). Time dependent black holes and scalar hair. Classical and Quantum Gravity, 31(19), Article 195006. https://doi.org/10.1088/0264-9381/31/19/195006

We show how to correctly account for scalar accretion onto black holes in scalar field models of dark energy by a consistent expansion in terms of a slow roll parameter. At leading order, we find an analytic solution for the scalar field within our H... Read More about Time dependent black holes and scalar hair.

Astrophysical black holes in screened modified gravity (2014)
Journal Article
Davis, A., Gregory, R., Jha, R., & Muir, J. (2014). Astrophysical black holes in screened modified gravity. Journal of Cosmology and Astroparticle Physics, 2014(08), Article 033. https://doi.org/10.1088/1475-7516/2014/08/033

Chameleon, environmentally dependent dilaton, and symmetron gravity are three models of modified gravity in which the effects of the additional scalar degree of freedom are screened in dense environments. They have been extensively studied in laborat... Read More about Astrophysical black holes in screened modified gravity.

Black holes as bubble nucleation sites (2014)
Journal Article
Gregory, R., Moss, I., & Withers, B. (2014). Black holes as bubble nucleation sites. Journal of High Energy Physics, 2014(3), https://doi.org/10.1007/jhep03%282014%29081

We consider the effect of inhomogeneities on the rate of false vacuum decay. Modelling the inhomogeneity by a black hole, we construct explicit Euclidean instantons which describe the nucleation of a bubble of true vacuum centred on the inhomogeneity... Read More about Black holes as bubble nucleation sites.

Rotating black hole hair (2013)
Journal Article
Gregory, R., Kubiznak, D., & Wills, D. (2013). Rotating black hole hair. Journal of High Energy Physics, 2013(6), https://doi.org/10.1007/jhep06%282013%29023

A Kerr black hole sporting cosmic string hair is studied in the context of the abelian Higgs model vortex. It is shown that such a system displays much richer phenomenology than its static Schwarzschild or Reissner-Nordstrom cousins, for example, the... Read More about Rotating black hole hair.

Lifshitz black holes in IIA supergravity (2012)
Journal Article
Barclay, L., Gregory, R., Parameswaran, S., Tasinato, G., & Zavala, I. (2012). Lifshitz black holes in IIA supergravity. Journal of High Energy Physics, 2012(5), Article 122. https://doi.org/10.1007/jhep05%282012%29122

We compute string theoretic black hole solutions having Lifshitz asymptotics with a general dynamical exponent z > 1. We start by constructing solutions in a flux compactification of six dimensional supergravity, then uplift them to massive type IIA... Read More about Lifshitz black holes in IIA supergravity.

Gauss-Bonnet Holographic Superconductors (2010)
Journal Article
Barclay, L., Gregory, R., Kanno, S., & Sutcliffe, P. (2010). Gauss-Bonnet Holographic Superconductors. Journal of High Energy Physics, 2010(12), Article 29. https://doi.org/10.1007/jhep12%282010%29029

We study holographic superconductors in five dimensional Einstein-Gauss-Bonnet gravity both numerically and analytically. We find the critical temperature of the superconductor decreases as backreaction is increased, although the effect of the Gauss-... Read More about Gauss-Bonnet Holographic Superconductors.

Effect of extra dimensions on gravitational waves from cosmic strings (2010)
Journal Article
O'Callaghan, E., Chadburn, S., Geshnizjani, G., Gregory, R., & Zavala, I. (2010). Effect of extra dimensions on gravitational waves from cosmic strings. Physical Review Letters, 105(8), Article 081602. https://doi.org/10.1103/physrevlett.105.081602

We show how the motion of cosmic superstrings in extra dimensions can modify the gravitational wave signal from cusps. Additional dimensions both round off cusps, as well as reducing the probability of their formation, and thus give a significant dim... Read More about Effect of extra dimensions on gravitational waves from cosmic strings.