Mailing address
| Department of Physics
University of Wisconsin-Milwaukee PO Box 413 Milwaukee, WI 53202 |
Degrees
|
Ph.D.
M.Sc. B.Sc. |
Theoretical Physics. (University of Alberta, Canada. 1994)
Mathematical Physics. (University College Dublin. 1989) Mathematical Science. (University College Dublin. 1988) |
Academic Employment
|
1999-
1998-99 1995-98 1993-95 |
Assistant Professor of Physics, UWM
Research Associate, Institute for Theoretical Physics, U. C. Santa Barbara Prize Fellow, California Institute of Technology Research Associate, University of Newcastle, England |
Awards
| 2002- | Cottrell Scholar | |
| 2002-2004 | Sloan Research Fellow | |
| 1993-1994 | Izaak Walton Killam Memorial Scholarship, U. of Alberta | |
| 1993 | Andrew Stewart Memorial Prize, U. of Alberta | |
| 1990-1992 | Recruitment Scholarship, U. of Alberta | |
| 1989 | Eolas Basic Research Award | |
| 1988-1989 | Scholarship in Mathematical Science, University College, Dublin. |
Involvements and Interests
|
Proyecto Espeleologica Purification Basic canoe leader certificate Basic First Aid certificate Secretary Graduate Physics Students Association 1991-1993 Leader, 1st Dublin Venture Scout Unit, 1988-1990 |
Selected Publications
-
Warren G Anderson, Patrick R Brady, Jolien Creighton
and Eanna E Flanagan
- An excess power statistic for detection of burst sources of
gravitational radiation
Phys. Rev. D 63, 042003 (2001), gr-qc/0008066. - B. Allen, K. Blackburn, P. Brady, J. Creighton, T. Creighton, S. Droz, A. Gillespie, S. Hughes, S. Kawamura, T. Lyons, J. Mason, B. J. Owen, F. Raab, M. Regehr, B. Sathyaprakash, R. L. Savage, S. Whitcomb, A. Wiseman
- Patrick R Brady, Chris M Chambers, William G Larrakkers and Eric Poisson
- Patrick R Brady and Teviet Creighton
- Patrick R Brady, Jolien Creighton and Kip S Thorne
- Patrick R Brady, Serge Droz, and Sharon M Morsink
- Patrick R Brady and Adrian C Ottewill
- Patrick R Brady, Teviet Creighton, Curt Cutler and Bernard Schutz
- Patrick R. Brady and John D. Smith
- Patrick R. Brady
- Warren G. Anderson, Patrick R. Brady, Werner Israel and Sharon Morsink,
- Observational limit on gravitational waves from
binary neutron stars in the Galaxy
Phys. Rev. Letters, 83, 1498 (1999), gr-qc/9903108.
- Radiative falloff in Schwarzschild-de Sitter
spacetime
Phys. Rev. D 60, 064003 (1999), gr-qc/9902010.
- Searching for periodic sources with LIGO. II: Hierarchical
searches
Phys. Rev. D 61, 082001 (2000), gr-qc/9812014}
- Computing the merger of black-hole binaries: the IBBH
problem
Phys. Rev. D 58, 061501 (1998), gr-qc/9804057.
- The late time singularity inside non-spherical black
holes
Phys. Rev. D 58, 084034 (1998), gr-qc/9805008.
- Quantum corrections to critical phenomena in gravitational
collapse
Phys. Rev. D 58, 024006 (1998), gr-qc/9804058.
- Searching for periodic sources with LIGO
Phys. Rev. D 57, 2101 (1998), gr-qc/9702050.
- Black hole singularities: A numerical approach
Phys. Rev. D 51, 4168-4176 (1995).
- Analytic example of critical behaviour in scalar field
collapse
Class. Quantum Grav. 11, 1255 (1994).
- Quantum effects in black hole interiors
Phys. Rev. Letters 70, 1041-1044 (1993).
Research Interests
My interests cover quantum aspects of gravity, black-hole physics and numerical relativity. The desired synthesis between quantum theory and the classical world of general relativity continues to be elusive, yet each is remarkably successful in its own realm. It is in strong gravitational fields, such as those obtaining is the early universe or inside black holes, that we begin to see the need to combine both theories. Moreover, the discovery of quantum radiation from black holes provides a glimpse of the beauty which a unified theory might hold. My current interests in black hole physics span both classical and quantum theory.Critical phenomena in collapse: During the past year I have been investigating aspects of classical gravitational collapse in an effort to understand the horizon and singularity structure in collapse spacetimes.
Matt Choptuik's discovery of universality and scaling behaviour in dispersion/black hole phase transitions sparked my interest in spherically symmetric scalar field collapse. Analytical explanations of the phenomena he has observed are as yet unavailable, nonetheless it does seem that the clues supplied by the numerical work can guide us to a deeper understanding of black-hole formation. The role played by discrete self-similarity in near critical evolutions led me to examine globally self-similar solutions to the field equations. These solutions exhibit some interesting properties, among which are phase transitions of a type. Recently I showed that near the critical point (and when black holes form) the radius of the apparent horizon exhibits a scaling relation with critical exponent 1/2. A more general investigation of the self-similar solutions demonstrated the existence of naked singularities which evolve from regular initial data, while providing further examples of phase transitions in gravitational collapse. Whether naked singularities persist upon relaxation of self-similarity is a question that I am addressing.
The observation of critical phenomena in other models of gravitational collapse also suggests new lines of investigation. Self-similarity plays a key role in all the models investigated thus far, however perfect fluids exhibit a continuous self-similarity in contradistinction to the dicrete echoeing observed in scalar field and axi-symmetric radiation collapse. A further investigation of fluid collapse for a variety of equations of state is necessary. I intend to undertake such an investigation in the near future. The ultimate goal is to understand to what extent these self-similar solutions are attractors for the endstate of gravitational collapse.
Black hole interiors:
Work
on spherically symmetric black-hole interiors has shown that the tunnel
to other universes is sealed off by a weak null singularity, thus preventing
travel through the black hole. My collaborators (primarily at the University
of Alberta) and I have investigated more realistic models of black-hole
interiors, and constructed asymptotic solutions near to the singularity.
The results indicate that spherical models do capture the essence of the
physics -- a weak, null singularity persists in the non-spherical case.
The spacetime appears to be asymptotically Petrov type N in the neighbourhood
of the singularity, with the degenrate null direction aligned with the
direction of the blueshifted influx.
While such asymptotic analyses provide convincing arguments, one would prefer to solve the initial value problem exactly. This is beyond present mathematical technology, however numerical relativity has reached a stage where it can provide a useful approach to this problem. Over the past year, John Smith (a graduate student at the University of Newcastle) and I have developed a code to numerically integrate the spherically symmetric Einstein-Maxwell-scalar field equations. Scalar field matter, in the spherically symmetric context, provides a good model for gravitational shear which will inevitably be present in realistic collapse scenarios. Our numerical treatment can be used to test asymptotic results -- preliminary indications are that the simple analytic models investigated to date present essentially the correct picture. Along with studying the well understood region near to the CH we intend to examine the region near to r=0, where the singularity is presumably spacelike, during the coming months.
Following this (rather
simple) involvement with numerical relativity I wish to consider less symmetric
situations in the future. Numerical codes based on the method of characteristics,
like the code mentioned above, are not easily implimentable in non-spherical
spacetimes, however investigations of axisymmetric spacetimes are possible
with current numerical techniques. Abrahams and Evans have undertaken some
preliminary studies of this type. It would be interesting to further examine
black-hole formation in axisymmetric spacetimes, both analytically and
numerically, in an effort to develop a complete picture of non-spherical
black-hole formation.
Quantum gravitational collapse: Without a final theory of quantum gravity a definitive treatment of quantum gravitational collapse is not possible. Nonetheless there are some interesting questions which one can attempt to answer within a semi-classical framework.
During the past several years my collaborators and I have investigated the effects that quantized massless fields may have on the geometry inside black holes. In particular we developed an approximation scheme which allowed us to estimate the renormalised stress-energy tensor, for a conformally invariant field, near the Cauchy horizon of a charged black hole. The results suggest that quantum effects actually reinforce the classical growth of curvature near mass-inflations singularities, refuting claims that spacetime might be continued through such a singularity.
Recently it was shown that the event horizon of an extreme Reissner-Nordstrom black hole is quantum mechanically unstable in the context of two-dimensional gravity. Whether an analogous instability exists in four dimensions remains an open question, although there are two groups working on an exact calculation. There is some hope that an answer could be found by an approximate treatment along the lines of the one described above. I am currently attempting to discover such an approach to this problem.
Finally, Ian Moss and I are looking at some general issues surrounding gravitational collapse and quantum gravity. This project is only in its infancy, however we would like to say something about singularities in quantum gravity and quantum effects obtaining in regions of high curvature. The idea is to investigate what a quantum observer might see as she falls into a black hole. This is closely related to the quantum evaporation of a black hole by the Hawking effect. I am also interested in questions of quantum backreaction on spacetime in this process, along with discussions of Hawking radiation in the presence of a short distance cutoff and of black-hole entropy.