I work on string theory and its applications to the understanding of black holes, phase transitions, and strongly coupled gauge theories. I focus particularly on the gauge-string duality, which relates gauge theories in four flat spacetime dimensions to string theory in five or ten curved dimensions. The gauge theories that can be described in this way are relatives of quantum chromodynamics, which is the theory of quarks and gluons.
There is growing evidence that the gauge-string duality describes aspects of heavy ion collisions. Such collisions cause protons and neutrons to melt into their constituent quarks and gluons, and it is generally believed that a locally thermalized state forms: the quark-gluon plasma. The strategy of the gauge-string duality is to compare the properties of the quark-gluon plasma to black holes in five curved dimensions. The results of such comparisons include predictions for the shear and bulk viscosity, the magnitude and pattern of energy loss from energetic quarks, and the location of a critical point at finite temperature and baryon density.
I have long been interested in black hole phase transitions, especially the tendency for horizons to become spatially inhomogeneous. I suggested the main mechanisms by which black holes can go through a superconducting phase transition at finite temperature, and I have investigated the fermion response to superconducting black hole backgrounds.
I maintain interests also in theoretical cosmology and in more formal aspects of the gauge-string duality. I also wrote a book on string theory for the layperson, entitled The Little Book of String Theory. You can find out more about it on the publisher's web page, and also here.
- (with A. Ficnar and M. Gyulassy) "Shooting String Holography of Jet Quenching at RHIC and LHC," arXiv:1311.6160 [hep-ph] (2013).
- (with A. Ficnar) "Finite momentum at string endpoints," arXiv:1306.6648 [hep-th] (2013).
- (with O. DeWolfe, C. Rosen, and D. Teaney) "Heavy ions and string theory," arXiv:1304.7794 [hep-th] (2013).
- (with A. Chandran, A. Nanduri, and S. Sondhi) "On equilibration and coarsening in the quantum $O(N)$ model at infinite $N$," Phys. Rev. B88, 024306, arXiv:1304.2402 [cond-mat.stat-mech] (2013).
- (with R. Caldwell) "A Brief History of Curvature," arXiv:1302.1201 [astro-ph.CO] (2013).
- "Complex deformations of Bjorken flow," Phys. Rev. C87, 014909, arXiv:1210.4181 [hep-th] (2013).
- "The gauge-string duality and heavy ion collisions," Foundations of Physics 43, 140-155, arXiv:1103.3636 [hep-th] (2013).
- (with J. Ren) "Analytic fermionic Green's functions from holography," Phys. Rev. D86, 046004, arXiv:1204.6315 [hep-th] (2012).
- (with A. Chandran, A. Erez, and S. Sondhi) "The Kibble-Zurek Problem: Universality and the Scaling Limit," Phys. Rev. B86, 064304, arXiv:1202.5277 [cond-mat.stat-mech] (2012).
- (with H. Bantilan and F. Pretorius) "Simulation of Asymptotically $AdS_5$ Spacetimes with a Generalized Harmonic Evolution Scheme," Phys. Rev. D85, 084038, arXiv:1201.2132 [hep-th] (2012).
- (with O. DeWolfe and C. Rosen) "Fermi Surfaces in Maximal Gauged Supergravity," Phys. Rev. Lett. 108, 251601, arXiv:1112.3036 [hep-th] (2012).
- "Superluminal neutrinos and extra dimensions: constraints from the null energy condition," Phys. Lett. B705, 279-281, arXiv:1109.5687 [hep-th] (2011).
- (with O. DeWolfe and C. Rosen) "Dynamic critical phenomena at a holographic critical point," Phys. Rev. D84, 126014, arXiv:1108.2029 [hep-th] (2011).
- (with R. Belliard and A. Yarom) "Absence of a Fermi surface in classical minimal four-dimensional gauged supergravity," JHEP 10, 055, arXiv:1106.6030 [hep-th] (2011).
- "Conformal symmetry and the Balitsky-Kovchegov equation," Phys. Rev. D84, 085024, arXiv:1102.4040 [hep-th] (2011).
- (with O. DeWolfe and C. Rosen) "A holographic critical point," Phys. Rev. D83, 086005, arXiv:1012.1864 [hep-th] (2011).
- (with A. Yarom) "Conformal hydrodynamics in Minkowski and de Sitter spacetimes," Nucl. Phys. B846, 469-511, arXiv:1012.1314 [hep-th] (2011).