PhD students

Prospective PhD students

All applications for PhD study at the University of Sheffield must be made online.  Please do not send applications directly to me.  The School of Mathematics and Statistics' prospective postgraduates webpage has information about PhD opportunities within the School, applications and funding.  The University's Doctoral Academy website has a great deal of useful information.  

To work under my supervision, I usually expect PhD students to have (or expect to obtain) the equivalent of a UK first class undergraduate degree at either BSc or MMath/MPhys level.  If you have a BSc undergraduate degree, then usually a Master's level qualification in either Theoretical Physics or Mathematics is also required.  A strong background in general relativity and quantum theory is necessary; knowledge of quantum field theory in flat space-time is an advantage.   Experience with algebraic and numerical computing (whether using Mathematica, Maple, Matlab or a programming language) is also an advantage.  

Possible PhD projects

  • Hawking radiation from quantum gravity black holes - Quantum effects are very important for black holes, but in the absence of a full theory of quantum gravity, effective models of black holes incorporating quantum effects are useful.  In a paper with Piero Nicolini, we studied the Hawking radiation of a quantum scalar field from a black hole described by a classical effective metric which models quantum gravity effects.  The radiation has a number of features rather different from the emission from a usual Schwarzschild black hole.  It would be interesting to extend this work to other quantum fields and more general effective black hole metrics.   

  • Quantum field theory on anti-de Sitter black holes - The renormalized vacuum polarization (VP) of a quantum scalar field and renormalized expectation value of the stress-energy tensor (RSET) are notoriously challenging quantities to compute, despite the central roles they play in quantum field theory in curved space-time.  There is a well-established methodology for computing both the VP and RSET for a quantum scalar field on a static, spherically symmetric, four-dimensional black hole space-time. The general idea is to write these expectation values as sums of various manifestly finite quantities which can be computed numerically.  The conventional approach does not work well in general for asymptotically anti-de Sitter black holes, as the standard quantities diverge on the space-time boundary.  The aim of this project would be to write the expectation values in terms of new quantities which remain finite on the space-time boundary, and hence to compute the VP and RSET on asymptotically anti-de Sitter black holes.  

  • Effect of charge superradiance on a quantum field - Superradiant modes of a scalar field on Kerr space-time are one of the many complications in defining quantum states on a rotating black hole.  Charge superradiance occurs for a charged scalar field on a charged black hole.  This project would investigate how quantum states can be defined in this case, paying particular attention to the role of superradiant modes. 

  • Quantum fermion field on a three-dimensional BTZ black hole - Quantum field theory on three-dimensional black holes is simpler than in four (or more) dimensions.  A quantum scalar field has been extensively studied on a three-dimensional BTZ black hole, but a quantum fermion field rather less so.  It would be interesting to compute the RSET for a quantum fermion field on both nonrotating and rotating BTZ black holes.  A key aspect will be studying appropriate boundary conditions for a fermion field on the space-time boundary. 

Current PhD students

  • Visakan Balakumar (started October 2017)
  • Thomas Morley (started October 2016)

Past PhD students

 Name Year of completion  Thesis title 
David Dempsey2017Wave propagation on black hole spacetimes (primary supervisor Sam Dolan)
Supakchai Ponglertsakul2016Aspects of self-gravitating solitons and hairy black holes
Wahiba Toubal 2015  On the mass of black holes with scalar field hair in anti-de Sitter space-time 
Keith Worden 2014  Aspects of quantum field theory on low-dimensional curved space-times
Matt Hewitt 2014  Vacuum polarization on higher-dimensional black hole space-times 
Victor Ambrus 2014 Dirac fermions on rotating space-times
Carl Kent 2013 Quantum scalar field theory on anti-de Sitter space
Ben Shepherd 2012 Einstein-Yang-Mills black holes in anti-de Sitter space
Erik Baxter 2006  Existence and stability of solitons and black holes in su(N) Einstein-Yang-Mills theory in anti-de Sitter space 
Phil Young 2006 Aspects of classical and semi-classical black holes in de Sitter and anti-de Sitter space 
Dean Morgan 2005  Quantum gravity phenomenology and high-energy neutrinos