2D Dilaton-Maxwell Gravity as a Fixed Point of the Renormalization Group

A general model of dialton-Maxwell gravity in two dimensions is investigated. The corresponding one-loop effective action and the generalized $\beta$-functions are obtained. A set of models that are fixed points of the renormalization group equations are presented.Comment: 7 pages, LaTeX file, UB-ECM-PF 92/Mar1

How Effective is China’s Monetary Policy? An assessment of the link between the growth of monetary aggregates and inflation during the 2000s

The effectiveness of China’s monetary policy hinges on the existence of a robust link between the growth of monetary aggregates and inflation. This paper considers this link during the 2000s using Structural VAR models and simulated out-of-sample forecasting techniques. The results indicate that the link is far from robust. Such findings serve to underscore the importance of institutional reforms that will enable interest rates to play a more prominent role as an instrument of monetary policy.

Loop Variables and Gauge Invariance in (Open) Bosonic String Theory

We give a simplified and more complete description of the loop variable approach for writing down gauge invariant equations of motion for the fields of the open string. A simple proof of gauge invariance to all orders is given. In terms of loop variables, the interacting equations look exactly like the free equations, but with a loop variable depending on an extra parameter, thus making it a band of finite width. The arguments for gauge invariance work exactly as in the free case. We show that these equations are Wilsonian RG equations with a finite world-sheet cutoff and that in the infrared limit, equivalence with the Callan-Symanzik $\beta$-functions should ensure that they reproduce the on-shell scattering amplitudes in string theory. It is applied to the tachyon-photon system and the general arguments for gauge invariance can be easily checked to the order calculated. One can see that when there is a finite world sheet cutoff in place, even the U(1) invariance of the equations for the photon, involves massive mode contributions. A field redefinition involving the tachyon is required to get the gauge transformations of the photon into standard form.Comment: 20 pages, Late

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.Comment: 14 pages + 6 figure

CP-Violation in Kaluza-Klein and Randall-Sundrum Theories

The Kaluza-Klein theory and Randall-Sundrum theory are examined comparatively, with focus on the five dimensional (Dirac) fermion and the dimensional reduction to four dimensions. They are treated in the Cartan formalism. The chiral property, localization, anomaly phenomena are examined. The electric and magnetic dipole moment terms naturally appear. The order estimation of the couplings is done. This is a possible origin of the CP-violation.Comment: 3 pages, 2 figures, Proceedings of the Fifth KEK Topical Conference -Frontiers in Flavor Physics

S-Wave Scattering of Charged Fermions by a Magnetic Black Hole

We argue that, classically, $s$-wave electrons incident on a magnetically charged black hole are swallowed with probability one: the reflection coefficient vanishes. However, quantum effects can lead to both electromagnetic and gravitational backscattering. We show that, for the case of extremal, magnetically charged, dilatonic black holes and a single flavor of low-energy charged particles, this backscattering is described by a perturbatively computable and unitary $S$-matrix, and that the Hawking radiation in these modes is suppressed near extremality. The interesting and much more difficult case of several flavors is also discussed.Comment: 9p

Information Loss and Anomalous Scattering

The approach of 't Hooft to the puzzles of black hole evaporation can be applied to a simpler system with analogous features. The system is $1+1$ dimensional electrodynamics in a linear dilaton background. Analogues of black holes, Hawking radiation and evaporation exist in this system. In perturbation theory there appears to be an information paradox but this gets resolved in the full quantum theory and there exists an exact $S$-matrix, which is fully unitary and information conserving. 't Hooft's method gives the leading terms in a systematic approximation to the exact result.Comment: 18 pages, 3 figures (postscript files available soon on request), (earlier version got corrupted by mail system

Adaptive query-based sampling of distributed collections

As part of a Distributed Information Retrieval system a de-scription of each remote information resource, archive or repository is usually stored centrally in order to facilitate resource selection. The ac-quisition ofprecise resourcedescriptionsistherefore animportantphase in Distributed Information Retrieval, as the quality of such represen-tations will impact on selection accuracy, and ultimately retrieval per-formance. While Query-Based Sampling is currently used for content discovery of uncooperative resources, the application of this technique is dependent upon heuristic guidelines to determine when a sufficiently accurate representation of each remote resource has been obtained. In this paper we address this shortcoming by using the Predictive Likelihood to provide both an indication of thequality of an acquired resource description estimate, and when a sufficiently good representation of a resource hasbeen obtained during Query-Based Sampling

Canonical and Functional Schrodinger Quantization of Two--Dimensional Dilaton Gravity

We discuss the relation between canonical and Schrodinger quantization of the CGHS model. We also discuss the situation when background charges are added to cancel the Virasoro anomaly. New physical states are found when the square of the background charges vanishes.Comment: 12 pages, revtex Minor correction

Torons and black hole entropy

We consider a supersymmetric system of D-5-branes compactified on a 5-torus with a self-dual background field strength on a 4-torus and carrying left-moving momentum along a circle. The corresponding supergravity solution describes a 5-dimensional black hole with a regular horizon. The entropy of this black hole may be explained in terms of the Landau degeneracy for open strings stretching between different branes. In the gauge theory approximation this D-5-brane system is described by a super Yang-Mills theory with a t'Hooft twist. By choosing a supersymmetric branch of the theory we obtain perfect agreement with the entropy formula. The result relies on the number of massless torons associated with the gauge field components that obey twisted boundary conditions.Comment: 31 pages, latex. Some equations corrected. Final version to be published in Nuclear Physics