Skip to main content
Home
Department Of Physics text logo
  • Research
    • Our research
    • Our research groups
    • Our research in action
    • Research funding support
    • Summer internships for undergraduates
  • Study
    • Undergraduates
    • Postgraduates
  • Engage
    • For alumni
    • For business
    • For schools
    • For the public
Menu
Black Hole

Lensing of space time around a black hole. At Oxford we study black holes observationally and theoretically on all size and time scales - it is some of our core work.

Credit: ALAIN RIAZUELO, IAP/UPMC/CNRS. CLICK HERE TO VIEW MORE IMAGES.

Dr Katy Clough

Visitor

Research theme

  • Particle astrophysics & cosmology

Sub department

  • Astrophysics

Research groups

  • Beecroft Institute for Particle Astrophysics and Cosmology
katy.clough@physics.ox.ac.uk
Telephone: 01865 83017
Personal webpage
GRChombo code website
  • About
  • Publications

The fate of dense scalar stars

Journal of Cosmology and Astroparticle Physics IOP Publishing 2019:07 (2019) Article:044

Authors:

F Muia, M Cicoli, Katherine Clough, F Pedro, Francisco Quevedo, GP Vacca

Abstract:

Long-lived pseudo-solitonic objects, known as oscillons/oscillatons, which we collectively call real scalar stars, are ubiquitous in early Universe cosmology of scalar field theories. Typical examples are axions stars and moduli stars. Using numerical simulations in full general relativity to include the effects of gravity, we study the fate of real scalar stars and find that depending on the scalar potential they are either meta-stable or collapse to black holes. In particular we find that for KKLT potentials the configurations are meta-stable despite the asymmetry of the potential, consistently with the results from lattice simulations that do not include gravitational effects. For α-attractor potentials collapse to black holes is possible in a region of the parameter space where scalar stars would instead seem to be meta-stable or even disperse without including gravity. Each case gives rise to different cosmological implications which may affect the stochastic spectrum of gravitational waves.
More details from the publisher
Details from ORA
More details
Details from ArXiV

Full 3D numerical relativity simulations of neutron star–boson star collisions with BAM

Classical and Quantum Gravity IOP Publishing 36:2 (2018) 025002-025002

Authors:

Tim Dietrich, Serguei Ossokine, Katy Clough
More details from the publisher
Details from ORA
More details
Details from ArXiV

Neutron star–axion star collisions in the light of multimessenger astronomy

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 483:1 (2018) 908-914

Authors:

Tim Dietrich, Francesca Day, Katy Clough, Michael Coughlin, Jens Niemeyer
More details from the publisher
Details from ORA
More details
Details from ArXiV

Axion star collisions with black holes and neutron stars in full 3D numerical relativity

Physical Review D American Physical Society 98:8 (2018) 083020

Authors:

Katherine Clough, T Dietrich, J Niemeyer

Abstract:

Axions are a potential dark matter candidate, which may condense and form self-gravitating compact objects, called axion stars (ASs). In this work, we study for the first time head-on collisions of relativistic ASs with black holes (BHs) and neutron stars (NSs). In the case of BH-AS mergers we find that, in general, the largest scalar clouds are produced by mergers of low compactness ASs and spinning BHs. Although in most of the cases which we study the majority of the mass is absorbed by the BH within a short time after the merger, in favorable cases the remaining cloud surrounding the final BH remnant can be as large as 30% of the initial axion star mass, with a bosonic cloud mass of O ( 10 − 1 ) M BH and peak energy density comparable to that obtained in a superradiant buildup. This provides a dynamical mechanism for the formation of long lived scalar hair, which could lead to observable signals in cases where the axion interacts with baryonic matter around the BH, or where it forms the seed of a future superradiant buildup in highly spinning cases. Considering NS-AS collisions we find two possible final states: (i) a BH surrounded by a (small) scalar cloud, or (ii) a stable NS enveloped in an axion cloud of roughly the same mass as the initial AS. While for low mass ASs the NS is only mildly perturbed by the collision, a larger mass AS gives rise to a massive ejection of baryonic mass from the system, purely due to gravitational effects. Therefore, even in the absence of a direct axion coupling to baryonic matter, NS-AS collisions could give rise to electromagnetic observables in addition to their gravitational wave signatures.
More details from the publisher
Details from ORA
More details
Details from ArXiV

On the difficulty of generating gravitational wave turbulence in the early universe

Classical and Quantum Gravity IOP Publishing 35:18 (2018) 187001

Authors:

Katherine Clough, J Niemeyer

Abstract:

A recent article by Galtier and Nazarenko (2017 Phys. Rev. Lett. 119 221101) proposed that weakly nonlinear gravitational waves could result in a turbulent cascade, with energy flowing from high to low frequency modes or vice versa. This is an interesting proposition for early universe cosmology because it could suggest some 'natural' initial conditions for the gravitational background. In this paper we use the ADM formalism to show that, given some simple and, arguably, natural assumptions, such initial conditions lead to expansion (or collapse) of the spacetime on a timescale much faster than that of the turbulent cascade, meaning that the cascade is unlikely to have sufficient time to develop under general conditions. We suggest possible ways in which the expansion could be mitigated to give the cascade time to develop.
More details from the publisher
Details from ORA
More details
Details from ArXiV

Pagination

  • First page First
  • Previous page Prev
  • …
  • Page 6
  • Page 7
  • Page 8
  • Page 9
  • Page 10
  • Page 11
  • Page 12
  • Current page 13
  • Page 14
  • Next page Next
  • Last page Last

Footer Menu

  • Contact us
  • Giving to the Dept of Physics
  • Work with us
  • Media

User account menu

  • Log in

Follow us

FIND US

Clarendon Laboratory,

Parks Road,

Oxford,

OX1 3PU

CONTACT US

Tel: +44(0)1865272200

University of Oxfrod logo Department Of Physics text logo
IOP Juno Champion logo Athena Swan Silver Award logo

© University of Oxford - Department of Physics

Cookies | Privacy policy | Accessibility statement

Built by: Versantus

  • Home
  • Research
  • Study
  • Engage
  • Our people
  • News & Comment
  • Events
  • Our facilities & services
  • About us
  • Current students
  • Staff intranet