Covariant Pauli-Villars Regularization of Quantum Gravity at the One Loop Order

We study a regularization of the Pauli-Villars kind of the one loop gravitational divergences in any dimension. The Pauli-Villars fields are massive particles coupled to gravity in a covariant and nonminimal way, namely one real tensor and one complex vector. The gauge is fixed by means of the unusual gauge-fixing that gives the same effective action as in the context of the background field method. Indeed, with the background field method it is simple to see that the regularization effectively works. On the other hand, we show that in the usual formalism (non background) the regularization cannot work with each gauge-fixing.In particular, it does not work with the usual one. Moreover, we show that, under a suitable choice of the Pauli-Villars coefficients, the terms divergent in the Pauli-Villars masses can be corrected by the Pauli-Villars fields themselves. In dimension four, there is no need to add counterterms quadratic in the curvature tensor to the Einstein action (which would be equivalent to the introduction of new coupling constants). The technique also works when matter is coupled to gravity. We discuss the possible consequences of this approach, in particular the renormalization of Newton's coupling constant and the appearance of two parameters in the effective action, that seem to have physical implications.Comment: 26 pages, LaTeX, SISSA/ISAS 73/93/E

Cosmological Gravitational Wave in a Gravity with Quadratic Order Curvature Couplings

We present a set of equations describing the cosmological gravitational wave in a gravity theory with quadratic order gravitational coupling terms which naturally arise in quantum correction procedures. It is known that the gravitational wave equation in the gravity theories with a general $f(R)$ term in the action leads to a second order differential equation with the only correction factor appearing in the damping term. The case for a $R^{ab} R_{ab}$ term is completely different. The gravitational wave is described by a fourth order differential equation both in time and space. However, curiously, we find that the contributions to the background evolution are qualitatively the same for both terms.Comment: 4 pages, revtex, no figure

Strong Coupling Quantum Gravity and Physics beyond the Planck Scale

We propose a renormalization prescription for the Wheeler-DeWitt equation of (3+1)-dimensional Einstein gravity and also propose a strong coupling expansion as an approximation scheme to probe quantum geometry at length scales much smaller than the Planck length. We solve the Wheeler-DeWitt equation to the second order in the expansion in a class of local solutions and discuss problems arising in our approach.Comment: 27 pages, LaTeX file. To be published in Phys. Rev.

Super-Ehlers in Any Dimension

We classify the enhanced helicity symmetry of the Ehlers group to extended supergravity theories in any dimension. The vanishing character of the pseudo-Riemannian cosets occurring in this analysis is explained in terms of Poincar\'e duality. The latter resides in the nature of regularly embedded quotient subgroups which are non-compact rank preserving.Comment: 1+55 pages; 15 Tables, 6 Figures; v2 : some clarifications added in Sec. 1 and in App.

Quantum Gravity

General lectures on quantum gravity.Comment: Lectures given at Karpacz. 40 pages, submitted to Lecture Notes in Physics. Bigger figure

On Locality in Quantum General Relativity and Quantum Gravity

The physical concept of locality is first analyzed in the special relativistic quantum regime, and compared with that of microcausality and the local commutativity of quantum fields. Its extrapolation to quantum general relativity on quantum bundles over curved spacetime is then described. It is shown that the resulting formulation of quantum-geometric locality based on the concept of local quantum frame incorporating a fundamental length embodies the key geometric and topological aspects of this concept. Taken in conjunction with the strong equivalence principle and the path-integral formulation of quantum propagation, quantum-geometric locality leads in a natural manner to the formulation of quantum-geometric propagation in curved spacetime. Its extrapolation to geometric quantum gravity formulated over quantum spacetime is described and analyzed.Comment: Mac-Word file translated to postscript for submission. The author may be reached at: [email protected] To appear in Found. Phys. vol. 27, 199

General relativity as an effective field theory: The leading quantum corrections

I describe the treatment of gravity as a quantum effective field theory. This allows a natural separation of the (known) low energy quantum effects from the (unknown) high energy contributions. Within this framework, gravity is a well behaved quantum field theory at ordinary energies. In studying the class of quantum corrections at low energy, the dominant effects at large distance can be isolated, as these are due to the propagation of the massless particles (including gravitons) of the theory and are manifested in the nonlocal/nonanalytic contributions to vertex functions and propagators. These leading quantum corrections are parameter-free and represent necessary consequences of quantum gravity. The methodology is illustrated by a calculation of the leading quantum corrections to the gravitational interaction of two heavy masses.Comment: 34 pages, Latex, UMHEP-40

Infinities within graviton scattering amplitudes

We present unitarity as a method for determining the infinities present in graviton scattering amplitudes. The infinities are a combination of IR and UV. By understanding the soft singularities we may extract the UV infinities and relate these to counter-terms in the effective action. As an demonstration of this method we rederive the UV infinities present at one-loop when gravity is coupled to matter.Comment: revised versio

String Theory, Unification and Quantum Gravity

An overview is given of the way in which the unification program of particle physics has evolved into the proposal of superstring theory as a prime candidate for unifying quantum gravity with the other forces and particles of nature. A key concern with quantum gravity has been the problem of ultraviolet divergences, which is naturally solved in string theory by replacing particles with spatially extended states as the fundamental excitations. String theory turns out, however, to contain many more extended-object states than just strings. Combining all this into an integrated picture, called M-theory, requires recognition of the r\^ole played by a web of nonperturbative duality symmetries suggested by the nonlinear structures of the field-theoretic supergravity limits of string theory.Comment: 29 pages, 13 figures, 3 tables; Lectures given at the 6th Aegean Summer School "Quantum Gravity and Quantum Cosmology", Chora, Naxos Island, Greece, 12-17 September 201

道徳と幸福 : カント倫理思想の一考察

Asthma is a serious health problem and during the last decade various experimental models of asthma have been developed to study the pathogenesis of this disease. In this study we describe a new mouse model of asthma that uses the spores of Alternaria alternata and Cladosporium herbarum, two allergenic molds recognized as common inducers of rhinitis and asthma in humans. Here we demonstrate that A. alternata and C. herbarum spores are immunogenic when injected into BALB/c mice, and induce the production of specific IgM and IgG1 antibodies and strongly increase IgE serum levels. To induce the allergic response, mice were sensitized by two intraperitoneal (i.p.) injections and then intranasaly (i.n.) challenged with A. alternata and C. herbarum spores. Bronchoalveolar lavages (BALs) from these mice contained numerous macrophages, neutrophils, eosinophils and lymphocytes whereas neutrophils were the predominant BAL inflammatory cells in nonsensitized mice. Histological studies demonstrated an influx of eosinophils in peri-vascular and peri-bronchial areas and the presence of numerous epithelial goblet cells only in sensitized mice. Increased expression of mRNA specific for various chemokines (eotaxin, MIP-1α, MIP-2) and chemokine receptors (CCR-1, CCR-2 and CCR-5) was observed in the lungs of nonsensitized mice challenged with the spores. Expression of CCR-3 mRNA in the lungs and Th2 cytokine (IL-4, IL-5 and IL-13) secretion in the BAL was additionally observed in sensitized and challenged mice. Finally we demonstrate through whole-body plethysmography that mold spore sensitization and challenge induce the development of an airway hyperreactivity in response to nebulized methacholine