arXiv subjects

S. B. Giddings

Publications and source records attributed to S. B. Giddings.

15 recordsLinked to original sources

arXiv2014

Inflation Physics from the Cosmic Microwave Background and Large Scale Structure

Fluctuations in the intensity and polarization of the cosmic microwave background (CMB) and the large-scale distribution of matter in the universe each contain clues about the nature of the earliest moments of time. The next generation of CMB and large-scale structure (LSS) experiments are poised to test the leading paradigm for these earliest moments---the theory of cosmic inflation---and to detect the imprints of the inflationary epoch, thereby dramatically increasing our understanding of fundamental physics and the early universe. A future CMB experiment with sufficient angular resolution and frequency coverage that surveys at least 1% of the sky to a depth of 1 uK-arcmin can deliver a constraint on the tensor-to-scalar ratio that will either result in a 5-sigma measurement of the energy scale of inflation or rule out all large-field inflation models, even in the presence of foregrounds and the gravitational lensing B-mode signal. LSS experiments, particularly spectroscopic surveys such as the Dark Energy Spectroscopic Instrument, will complement the CMB effort by improving current constraints on running of the spectral index by up to a factor of four, improving constraints on curvature by a factor of ten, and providing non-Gaussianity constraints that are competitive with the current CMB bounds.

astro-ph.CO↗

arXiv2008

Warped Supersymmetry Breaking

We address the size of supersymmetry-breaking effects within higher-dimensional settings where the observable sector resides deep within a strongly warped region, with supersymmetry breaking not necessarily localized in that region. Our particular interest is in how the supersymmetry-breaking scale seen by the observable sector depends on this warping. We obtain this dependence in two ways: by computing within the microscopic (string) theory supersymmetry-breaking masses in supermultiplets; and by investigating how warping gets encoded into masses within the low-energy 4D effective theory. We find that the lightest gravitino mode can have mass much less than the straightforward estimate from the mass shift of the unwarped zero mode. This lightest Kaluza-Klein excitation plays the role of the supersymmetric partner of the graviton and has a warped mass m_{3/2} proportional to e^A, with e^A the warp factor, and controls the size of the soft SUSY breaking terms. We formulate the conditions required for the existence of a description in terms of a 4D SUGRA formulation, or in terms of 4D SUGRA together with soft-breaking terms, and describe in particular situations where neither exist for some non-supersymmetric compactifications. We suggest that some effects of warping are captured by a linear $A$ dependence in the Kahler potential. We outline some implications of our results for the KKLT scenario of moduli stabilization with broken SUSY.

hep-th↗

arXiv2002

Linearized Gravity in Brane Backgrounds

A treatment of linearized gravity is given in the Randall-Sundrum background. The graviton propagator is found in terms of the scalar propagator, for which an explicit integral expression is provided. This reduces to the four-dimensional propagator at long distances along the brane, and provides estimates of subleading corrections. Asymptotics of the propagator off the brane yields exponential falloff of gravitational fields due to matter on the brane. This implies that black holes bound to the brane have a "pancake"-like shape in the extra dimension, and indicates validity of a perturbative treatment off the brane. Some connections with the AdS/CFT correspondence are described.

hep-th↗

arXiv2001

Precursors, black holes, and a locality bound

We revisit the problem of precursors in the AdS/CFT correspondence. Identification of the precursors is expected to improve our understanding of the tension between holography and bulk locality and of the resolution of the black hole information paradox. Previous arguments that the precursors are large, undecorated Wilson loops are found to be flawed. We argue that the role of precursors should become evident when one saturates a certain locality bound. The spacetime uncertainty principle is a direct consequence of this bound.

hep-th↗

arXiv1999

D3-brane shells to black branes on the Coulomb branch

We use the AdS/CFT duality to study the special point on the Coulomb branch of ${\cal N}=4$ SU(N) gauge theory which corresponds to a spherically symmetric shell of D3-branes. This point is of interest both because the spacetime region inside the shell is flat, and because this configuration gives a very simple example of the transition between D-branes in the perturbative string regime and the non-perturbative regime of black holes. We discuss how this geometry is described in the dual gauge theory, through its effect on the two-point functions and Wilson loops. In the calculation of the two-point function, we stress the importance of absorption by the branes.

hep-th↗

arXiv1994

Quantum Aspects of Gravity

Contributions from the G1 Working Group at the APS Summer Study on Particle and Nuclear Astrophysics and Cosmology in the Next Millennium, Snowmass, Colorado, June 29 - July 14, 1994. V. Frolov and L. Thorlacius: Quantum Aspects of Gravity. S.B. Giddings and L. Thorlacius: Introduction to the Information Problem. A. Strominger: Two-Dimensional Black Holes and the Information Puzzle. V. Frolov: Entropy of Black Holes. L. Thorlacius: Black Hole Complementarity. D.A. Lowe: Causality in String Theory. A.O. Barvinski: Nonlocal Effective Action and Black Holes. P.C. Argyres: Universality and Scaling in Black Hole Formation.

astro-ph↗

arXiv1993

Comments on information loss and remnants

The information loss and remnant proposals for resolving the black hole information paradox are reconsidered. It is argued that in typical cases information loss implies energy loss, and thus can be thought of in terms of coupling to a spectrum of ``fictitious'' remnants. This suggests proposals for information loss that do not imply planckian energy fluctuations in the low energy world. However, if consistency of gravity prevents energy non-conservation, these remnants must then be considered to be real. In either case, the catastrophe corresponding to infinite pair production remains a potential problem. Using Reissner-Nordstrom black holes as a paradigm for a theory of remnants, it is argued that couplings in such a theory may give finite production despite an infinite spectrum. Evidence for this is found in analyzing the instanton for Schwinger production; fluctuations from the infinite number of states lead to a divergent stress tensor, spoiling the instanton calculation. Therefore naive arguements for infinite production fail.

hep-th↗

arXiv1993

Hairy Black Holes in String Theory

Solutions of bosonic string theory are constructed which correspond to four-dimensional black holes with axionic quantum hair. The basic building blocks are the renormalization group flows of the CP1 model with a theta term and the SU(1,1)/U(1) WZW coset conformal field theory. However the solutions are also found to have negative energy excitations, and are accordingly expected to decay to the vacuum.

hep-th↗

arXiv1993

Entropy in Black Hole Pair Production

Pair production of Reissner-Nordstrom black holes in a magnetic field can be described by a euclidean instanton. It is shown that the instanton amplitude contains an explicit factor of $e^{A/4}$, where $A$ is the area of the event horizon. This is consistent with the hypothesis that $e^{A/4}$ measures the number of black hole states.

gr-qc↗

arXiv1993

Black Holes and Quantum Predictability

A brief review of the confrontation between black hole physics and quantum-mechanical unitarity is presented. Possibile reconciliations are modifying the laws of physics to allow fundamental loss of information, escape of information during the Hawking process, or black hole remnants. Each of these faces serious objections. A better understanding of the problem and its possible solutions can be had by studying two-dimensional models of dilaton gravity. Recent developments in these investigations are summarized. (Linear superposition of talks presented at the 7th Nishinomiya Yukawa Memorial Symposium and at the 1992 YITP Workshop on Quantum Gravity, November 1992.)

hep-th↗

arXiv1993

Four Dimensional Black Holes in String Theory

Exact solutions of heterotic string theory corresponding to four-dimensional charge Q magnetic black holes are constructed as tensor products of an SU(2)/Z(2Q+2) WZW orbifold with a (0,1) supersymmetric SU(1,1)/U(1) WZW coset model. The spectrum is analyzed in some detail. ``Bad'' marginal operators are found which are argued to deform these theories to asymptotically flat black holes. Surprising behaviour is found for small values of Q, where low-energy field theory is inapplicable. At the minimal value Q=1, the theory degenerates. Renormalization group arguments are given that suggest the potential gravitational singularity of the low-energy field theory is resolved by a massive two-dimensional field theory. At Q=0, a stable, neutral ``remnant,'' of potential relevance to the black hole information paradox, is found.

hep-th↗

arXiv1993

Constraints on Black Hole Remnants

One possible fate of information lost to black holes is its preservation in black hole remnants. It is argued that a type of effective field theory describes such remnants (generically referred to as informons). The general structure of such a theory is investigated and the infinite pair production problem is revisited. A toy model for remnants clarifies some of the basic issues; in particular, infinite remnant production is not suppressed simply by the large internal volumes as proposed in cornucopion scenarios. Criteria for avoiding infinite production are stated in terms of couplings in the effective theory. Such instabilities remain a problem barring what would be described in that theory as a strong coupling conspiracy. The relation to euclidean calculations of cornucopion production is sketched, and potential flaws in that analysis are outlined. However, it is quite plausible that pair production of ordinary black holes (e.g. Reissner Nordstrom or others) is suppressed due to strong effective couplings. It also remains an open possibility that a microscopic dynamics can be found yielding an appropriate strongly coupled effective theory of neutral informons without infinite pair production.

hep-th↗

arXiv1992

Black Holes and Massive Remnants

This paper revisits the conundrum faced when one attempts to understand the dynamics of black hole formation and evaporation without abandoning unitary evolution. Previous efforts to resolve this puzzle assume that information escapes in corrections to the Hawking process, that an arbitrarily large amount of information is transmitted by a planckian energy or contained in a Planck-sized remnant, or that the information is lost to another universe. Each of these possibilities has serious difficulties. This paper considers another alternative: remnants that carry large amounts of information and whose size and mass depend on their information content. The existence of such objects is suggested by attempts to incorporate a Planck scale cutoff into physics. They would greatly alter the late stages of the evaporation process. The main drawback of this scenario is apparent acausal behavior behind the horizon.

hep-th↗

arXiv1992

Quantum Black Holes

Static solutions of large-$N$ quantum dilaton gravity in $1+1$ dimensions are analyzed and found to exhibit some unusual behavior. As expected from previous work, infinite-mass solutions are found describing a black hole in equilibrium with a bath of Hawking radiation. Surprisingly, the finite mass solutions are found to approach zero coupling both at the horizon and spatial infinity, with a ``bounce'' off of strong coupling in between. Several new zero mass solutions -- candidate quantum vacua -- are also described.

hep-th↗

arXiv1992

Dynamics of Extremal Black Holes

Particle scattering and radiation by a magnetically charged, dilatonic black hole is investigated near the extremal limit at which the mass is a constant times the charge. Near this limit a neighborhood of the horizon of the black hole is closely approximated by a trivial product of a two-dimensional black hole with a sphere. This is shown to imply that the scattering of long-wavelength particles can be described by a (previously analyzed) two-dimensional effective field theory, and is related to the formation/evaporation of two-dimensional black holes. The scattering proceeds via particle capture followed by Hawking re-emission, and naively appears to violate unitarity. However this conclusion can be altered when the effects of backreaction are included. Particle-hole scattering is discussed in the light of a recent analysis of the two-dimensional backreaction problem. It is argued that the quantum mechanical possibility of scattering off of extremal black holes implies the potential existence of additional quantum numbers - referred to as ``quantum whiskers'' - characterizing the black hole.

hep-th↗