Research topic

Black Holes and Theoretical Physics

Discover papers and researchers connected with this scholarly topic.

Research papers

1967 · Physical Review Letters · 7,323 citations

A Model of Leptons

2004 · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields · 2,295 citations

Is cosmic speed-up due to new gravitational physics?

We show that cosmic acceleration can arise due to very tiny corrections to the usual gravitational action of general relativity, of the form ${R}^{\ensuremath{-}n}$ with $n>0.$ This model eliminates the need for a nonzero cosmological constant or any other form of dark energy, attributing a purely gravitational origin to the acceleration of the universe.

2009 · Classical and Quantum Gravity · 1,659 citations

Lectures on holographic methods for condensed matter physics

These notes are loosely based on lectures given at the CERN Winter School on Supergravity, Strings and Gauge theories, February 2009, and at the IPM String School in Tehran, April 2009. I have focused on a few concrete topics and also on addressing questions that have arisen repeatedly. Background condensed matter physics material is included as motivation and easy reference for the high energy physics community. The discussion of holographic techniques progresses from equilibrium, to transport and to superconductivity.

2017 · Physics Letters B · 53 citations

Can chaos be observed in quantum gravity?

Full general relativity is almost certainly ‘chaotic’. We argue that this entails a notion of non-integrability: a generic general relativistic model, at least when coupled to cosmologically interesting matter, likely possesses neither differentiable Dirac observables nor a reduced phase space. It follows that the standard notion of observable has to be extended to include non-differentiable or even discontinuous generalized observables. These cannot carry Poisson-algebraic structures and do not admit a standard quantization; one thus faces a quantum representation problem of gravitational observables. This has deep consequences for a quantum theory of gravity, which we investigate in a simple model for a system with Hamiltonian constraint that fails to be completely integrable. We show that basing the quantization on standard topology precludes a semiclassical limit and can even prohibit any solutions to the quantum constraints. Our proposed solution to this problem is to refine topology such that a complete set of Dirac observables becomes continuous. In the toy model, it turns out that a refinement to a polymer-type topology, as e.g. used in loop gravity, is sufficient. Basing quantization of the toy model on this finer topology, we find a complete set of quantum Dirac observables and a suitable semiclassical limit. This strategy is applicable to realistic candidate theories of quantum gravity and thereby suggests a solution to a long-standing problem which implies ramifications for the very concept of quantization. Our work reveals a qualitatively novel facet of chaos in physics and opens up a new avenue of research on chaos in gravity which hints at deep insights into the structure of quantum gravity.

2020 · Physical review. D/Physical review. D. · 7 citations

Holography for tensor models

In this article we explore the holographic duals of tensor models using collective field theory. We develop a description of the gauge invariant variables of the tensor model. This is then used to develop a collective field theory description of the dynamics. We consider matrixlike subsectors that develop an extra holographic dimension. In particular, we develop the collective field theory for the matrixlike sector of an interacting tensor model. We check the correctness of the large $N$ collective field by showing that it reproduces the perturbative expansion of large $N$ expectation values. In contrast to this, we argue that melonic large $N$ limits do not develop an extra dimension. This conclusion follows from the large $N$ value for the melonic collective field, which has delta function support. The finite $N$ physics of the model is also developed and nonperturbative effects in the $1/N$ expansion are exhibited.

1972 · Progress of Theoretical Physics · 2 citations

Photo-Neutral Vector Meson Couplings in the Relativistic Extended Quark Model

Progress of Theoretical Physics Vol. 49 No. 1 (1973) pp. 282-292 High Energy Photo-Reactions and Generalized Vector Meson Dominance Model in the Relativistically Extended Quark Model Tsunehiro Kobayashi Progress of Theoretical Physics Vol. 52 No. 4 (1974) pp. 1355-1368 Gauge Freedom in Dual Feynman-Like Rules and Its Relation to the Massless Yang-Mills Field Theory Tamiaki Yoneya