arXiv subjects

Steven B. Giddings

Publications and source records attributed to Steven B. Giddings.

114 records · Page 7Linked to original sources

arXiv1995

Some exact results in supersymmetric theories based on exceptional groups

We begin an investigation of supersymmetric theories based on exceptional groups. The flat directions are most easily parameterized using their correspondence with gauge invariant polynomials. Symmetries and holomorphy tightly constrain the superpotentials, but due to multiple gauge invariants other techniques are needed for their full determination. We give an explicit treatment of $G_2$ and find gaugino condensation for $N_f\leq 2$, and an instanton generated superpotential for $N_f=3$. The analogy with $SU(N_c)$ gauge theories continues with modified and unmodified quantum moduli spaces for $N_f=4$ and $N_f=5$ respectively, and a non-Abelian Coulomb phase for $N_f\geq6$. Electric variables suffice to describe this phase over the full range of $N_f$. The appendix gives a self-contained introduction to $G_2$ and its invariant tensors.

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arXiv1994

Why Aren't Black Holes Infinitely Produced?

Unitarity and locality imply a remnant solution to the information problem, and also imply that Reissner-Nordstrom black holes have infinite numbers of internal states. Pair production of such black holes is reexamined including the contribution of these states. It is argued that the rate is proportional to the thermodynamic quantity Tr e^{-beta H}, where the trace is over the internal states of a black hole; this is in agreement with estimates from an effective field theory for black holes. This quantity, and the rate, is apparently infinite due to the infinite number of states. One obvious out is if the number of internal states of a black hole is finite.

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arXiv1994

Quantum Mechanics of Black Holes

These lectures give a pedagogical review of dilaton gravity, Hawking radiation, the black hole information problem, and black hole pair creation. (Lectures presented at the 1994 Trieste Summer School in High Energy Physics and Cosmology)

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arXiv1993

On Pair Creation of Extremal Black Holes and Kaluza-Klein Monopoles

Classical solutions describing charged dilaton black holes accelerating in a background magnetic field have recently been found. They include the Ernst metric of the Einstein-Maxwell theory as a special case. We study the extremal limit of these solutions in detail, both at the classical and quantum levels. It is shown that near the event horizon, the extremal solutions reduce precisely to the static extremal black hole solutions. For a particular value of the dilaton coupling, these extremal black holes are five dimensional Kaluza-Klein monopoles. The euclidean sections of these solutions can be interpreted as instantons describing the pair creation of extremal black holes/Kaluza-Klein monopoles in a magnetic field. The action of these instantons is calculated and found to agree with the Schwinger result in the weak field limit. For the euclidean Ernst solution, the action for the extremal solution differs from that of the previously discussed wormhole instanton by the Bekenstein-Hawking entropy. However, in many cases quantum corrections become large in the vicinity of the black hole, and the precise description of the creation process is unknown.

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arXiv1992

Toy Models For Black Hole Evaporation

These are lecture notes for the 1992 Erice Workshop on Theoretical Physics. They first present a summary of the paradox of information loss to black holes, of its proposed resolutions, and of the flaws in the proposed resolutions. There follows a review of recent attempts to attack this problem, and other issues in black hole physics, using two-dimensional dilaton gravity theories as toy models. These toy models contain collapsing black holes and have for the first time enabled an explicit semiclassical treatment of the backreaction of the Hawking radiation on the geometry of an evaporating black hole. However, a complete answer to the information conundrum seems to require physics beyond the semiclassical approximation. Preliminary attempts to make progress in this direction, using connections to conformal field theory, are described.

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arXiv1992

Quantum Theories of Dilaton Gravity

Quantization of two-dimensional dilaton gravity coupled to conformal matter is investigated. Working in conformal gauge about a fixed background metric, the theory may be viewed as a sigma model whose target space is parameterized by the dilaton $ϕ$ and conformal factor $ρ$. A precise connection is given between the constraint that the theory be independent of the background metric and conformal invariance of the resulting sigma model. Although the action is renormalizable, new coupling constants must be specified at each order in perturbation theory in order to determine the quantum theory. These constants may be viewed as initial data for the beta function equations. It is argued that not all choices of this data correspond to physically sensible theories of gravity, and physically motivated constraints on the data are discussed. In particular a recently constructed subclass of initial data which reduces the full quantum theory to a soluble Liouville-like theory has energies unbounded from below and thus is unphysical. Possibilities for modifying this construction so as to avoid this difficulty are briefly discussed.

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