arXiv subjects

Steven B. Giddings

Publications and source records attributed to Steven B. Giddings.

At least 109 records · Page 6Linked to original sources

arXiv2003

Scales and hierarchies in warped compactifications and brane worlds

Warped compactifications with branes provide a new approach to the hierarchy problem and generate a diversity of four-dimensional thresholds. We investigate the relationships between these scales, which fall into two classes. Geometrical scales, such as thresholds for Kaluza-Klein, excited string, and black hole production, are generically determined soley by the spacetime geometry. Dynamical scales, notably the scale of supersymmetry breaking and moduli masses, depend on other details of the model. We illustrate these relationships in a class of solutions of type IIB string theory with imaginary self-dual fluxes. After identifying the geometrical scales and the resulting hierarchy, we determine the gravitino and moduli masses through explicit dimensional reduction, and estimate their value to be near the four-dimensional Planck scale. In the process we obtain expressions for the superpotential and Kahler potential, including the effects of warping. We identify matter living on certain branes to be effectively sequestered from the supersymmetry breaking fluxes: specifically, such "visible sector" fields receive no tree-level masses from the supersymmetry breaking. However, loop corrections are expected to generate masses, at the phenomenologically viable TeV scale.

hep-th↗

arXiv2003

High energy QCD scattering, the shape of gravity on an IR brane, and the Froissart bound

High-energy scattering in non-conformal gauge theories is investigated using the AdS/CFT dual string/gravity theory. It is argued that strong-gravity processes, such as black hole formation, play an important role in the dual dynamics. Further information about this dynamics is found by performing a linearized analysis of gravity for a mass near an infrared brane; this gives the far field approximation to black hole or other strong-gravity effects, and in particular allows us to estimate their shape. From this shape, one can infer a total scattering cross-section that grows with center of mass energy as ln^2 E, saturating the Froissart bound.

hep-th↗

arXiv2003

The fate of four dimensions

In gravitational theories with extra dimensions, it is argued that the existence of a positive vacuum energy generically implies catastrophic instability of our four-dimensional world. The most generic instability is a decompactification transition to growth of the extra dimensions, although other equally bad transitions may take place. This follows from simple considerations based on the form of the potential for the size modulus of the extra dimensions, and apparently offers a resolution of the conundrums presented by eternal de Sitter space. This argument is illustrated in the context of string theory with a general discussion of potentials generated by fluxes, wrapped branes, and stringy corrections. Moreover, it is unlikely that the present acceleration of the Universe represents an ongoing transition in a quintessence scenario rolling towards decompactification, unless the higher dimensional theory has a cosmological constant.

hep-th↗

arXiv2002

Toward a Theory of Precursors

To better understand the possible breakdown of locality in quantum gravitational systems, we pursue the identity of precursors in the context of AdS/CFT. Holography implies a breakdown of standard bulk locality which we expect to occur only at extremely high energy. We consider precursors that encode bulk information causally disconnected from the boundary and whose measurement involves nonlocal bulk processes. We construct a toy model of holography which encapsulates the expected properties of precursors and compare it with previous such discussions. If these precursors can be identified in the gauge theory, they are almost certainly Wilson loops, perhaps with decorations, but the relevant information is encoded in the high-energy sector of the theory and should not be observable by low energy measurements. This would be in accord with the locality bound, which serves as a criterion for situations where breakdown of bulk locality is expected.

hep-th↗

arXiv2002

High Energy Colliders as Black Hole Factories: The End of Short Distance Physics

If the fundamental Planck scale is of order a TeV, as the case in some extra-dimensions scenarios, future hadron colliders such as the Large Hadron Collider will be black hole factories. The non-perturbative process of black hole formation and decay by Hawking evaporation gives rise to spectacular events with up to many dozens of relatively hard jets and leptons, with a characteristic ratio of hadronic to leptonic activity of roughly 5:1. The total transverse energy of such events is typically a sizeable fraction of the beam energy. Perturbative hard scattering processes at energies well above the Planck scale are cloaked behind a horizon, thus limiting the ability to probe short distances. The high energy black hole cross section grows with energy at a rate determined by the dimensionality and geometry of the extra dimensions. This dependence therefore probes the extra dimensions at distances larger than the Planck scale.

hep-ph↗

arXiv2002

Black holes at accelerators

This is my contribution to the proceedings of Stephen Hawking's 60th birthday celebration. If the ideas of TeV scale gravity are correct, then black holes should be produced at accelerators that probe the TeV scale, and their decays should evidence one of Stephen's greatest discoveries, the phenomenon of black hole radiance.

hep-th↗

arXiv2002

Black holes in the lab?

If TeV-scale gravity describes nature, black holes will be produced in particle accelerators, perhaps even with impressive rates at the Large Hadron Collider. Their decays, largely via the Hawking process, will be spectacular. Black holes also would be produced in cosmic ray collisions with our atmosphere, and their showers may be observable. Such a scenario means the end of our quest to understand the world at shorter distances, but may represent the beginning of the exploration of extra dimensions.

hep-th↗

arXiv2002

Hierarchies from Fluxes in String Compactifications

Warped compactifications with significant warping provide one of the few known mechanisms for naturally generating large hierarchies of physical scales. We demonstrate that this mechanism is realizable in string theory, and give examples involving orientifold compactifications of IIB string theory and F-theory compactifications on Calabi-Yau four-folds. In each case, the hierarchy of scales is fixed by a choice of RR and NS fluxes in the compact manifold. Our solutions involve compactifications of the Klebanov-Strassler gravity dual to a confining N=1 supersymmetric gauge theory,and the hierarchy reflects the small scale of chiral symmetry breaking in the dual gauge theory.

hep-th↗

arXiv2002

Classical Black Hole Production in High-Energy Collisions

We investigate classical formation of a D-dimensional black hole in a high energy collision of two particles. The existence of an apparent horizon is related to the solution of an unusual boundary-value problem for Poisson's equation in flat space. For sufficiently small impact parameter, we construct solutions giving such apparent horizons in D=4. These supply improved estimates of the classical cross-section for black hole production, and of the mass of the resulting black holes. We also argue that a horizon can be found in a region of weak curvature, suggesting that these solutions are valid starting points for a semiclassical analysis of quantum black hole formation.

gr-qc↗

arXiv2001

Gravitational collapse and its boundary description in AdS

We provide examples of gravitational collapse and black hole formation in AdS, either from collapsing matter shells or in analogy to the Oppenheimer-Sneider solution. We then investigate boundary properties of the corresponding states. In particular, we describe the boundary two-point function corresponding to a shell outside its horizon; if the shell is quasistatically lowered into the horizon, the resulting state is the Boulware state. We also describe the more physical Hartle-Hawking state, and discuss its connection to the quasistatic shell states and to thermalization on the boundary.

hep-th↗

arXiv2001

Black hole production in TeV-scale gravity, and the future of high energy physics

If the Planck scale is near a TeV, black hole production should be possible at colliders, as well as by cosmic rays. I begin with a review of the two approaches to TeV-scale gravity, large extra dimensions and warped compactification, presented in a unified framework. Then properties of such black holes and estimates of their production rates are given, and consequences for the future of high-energy experimental physics are discussed.

hep-ph↗

arXiv2000

Effective theories and black hole production in warped compactifications

We investigate aspects of the four-dimensional effective description of brane world scenarios based on warped compactification on anti-de Sitter space. The low-energy dynamics is described by visible matter gravitationally coupled to a ``dark'' conformal field theory. We give the linearized description of the 4d stress tensor corresponding to an arbitrary 5d matter distribution. In particular a 5d falling particle corresponds to a 4d expanding shell, giving a 4d interpretation of a trajectory that misses a black hole only by moving in the fifth dimension. Breakdown of the effective description occurs when either five-dimensional physics or strong gravity becomes important. In scenarios with a TeV brane, the latter can happen through production of black holes near the TeV scale. This could provide an interesting experimental window on quantum black hole dynamics.

hep-th↗

arXiv1999

The boundary S-matrix and the AdS to CFT dictionary

An S-matrix analog is defined for anti-de Sitter space by constructing ``in'' and ``out'' states that asymptote to the timelike boundary. A derivation parallel to that of the LSZ formula shows that this ``boundary S-matrix'' is given directly by correlation functions in the boundary conformal theory. This provides a key entry in the AdS to CFT dictionary.

hep-th↗

arXiv1999

What Do CFTs Tell Us About Anti-de Sitter Spacetimes?

The AdS/CFT conjecture relates quantum gravity on Anti-de Sitter (AdS) space to a conformal field theory (CFT) defined on the spacetime boundary. We interpret the CFT in terms of natural analogues of the bulk S-matrix. Our first approach finds the bulk S-matrix as a limit of scattering from an AdS bubble immersed in a space admitting asymptotic states. Next, we show how the periodicity of geodesics obstructs a standard LSZ prescription for scattering within global AdS. To avoid this subtlety we partition global AdS into patches within which CFT correlators reconstruct transition amplitudes of AdS states. Finally, we use the AdS/CFT duality to propose a large N collective field theory that describes local, perturbative supergravity. Failure of locality in quantum gravity should be related to the difference between the collective 1/N expansion and genuine finite N dynamics.

hep-th↗

arXiv1998

High Energy Scattering and D-Pair Creation in Matrix String Theory

In this paper we use the matrix string approach to begin a study of high energy scattering processes in M-theory. In particular we exhibit an instanton-type configuration in 1+1 super-Yang-Mills theory that can be interpreted as a non-perturbative description of a string interaction. This solution is used to describe high energy processes with non-zero longitudinal momentum exchange, in which an arbitrary number of eigenvalues get transferred between the two scattering states. We describe a direct correspondence between these semi-classical SYM configurations and the Gross-Mende saddle points. We also study in detail the pair production of D-particles via a one-loop calculation which in the 1+1D gauge theory language is described by the (perturbative) transition between states with different electric flux. Finally, we discuss a possible connection between these calculations in which D-particle production gives important corrections to the Gross-Mende process.

hep-th↗

arXiv1996

Scattering ripples from branes

A novel probe of D-brane dynamics is via scattering of a high energy ripple traveling along an attached string. The inelastic processes in which the D-brane is excited through emission of an additional attached string is considered. Corresponding amplitudes can be found by factorizing a one-loop amplitude derived in this paper. This one-loop amplitude is shown to have the correct structure, but extraction of explicit expressions for the scattering amplitudes is difficult. It is conjectured that the exponential growth of available string states with energy leads to an inclusive scattering rate that becomes large at the string scale, due to excitation of the ``string halo,'' and meaning that such probes do not easily see structure at shorter scales.

hep-th↗

arXiv1996

On the Moduli Space of N = 2 Supersymmetric G_2 Gauge Theory

We apply the method of confining phase superpotentials to N = 2 supersymmetric Yang-Mills theory with the exceptional gauge group G_2. Our findings are consistent with the spectral curve of the periodic Toda lattice, but do not agree with the hyperelliptic curve suggested previously in the literature. We also apply the method to theories with fundamental matter, treating both the example of SO(5) and G_2.

hep-th↗

arXiv1995

The black hole information paradox

A concise survey of the black hole information paradox and its current status is given. A summary is also given of recent arguments against remnants. The assumptions underlying remnants, namely unitarity and causality, would imply that Reissner Nordstrom black holes have infinite internal states. These can be argued to lead to an unacceptable infinite production rate of such black holes in background fields. (To appear in the proceedings of the PASCOS symposium/Johns Hopkins Workshop, Baltimore, MD, March 22-25, 1995).

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