摘要:

String theory is a promising candidate for a quantum theory of gravity and a unified theory of all forces and particles. I will briefly summarize the current status of this theory and discuss some recent results. The most important results involve describing quantum states of black holes in terms of strings, which has provided a fundamental explanation of black hole entropy and Hawking radiation. Further investigation of this connection between black holes and strings has led to a completely new nonperturbative formulation of string theory. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1419525

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Unified theories suggest that space is intrinsically 10 dimensional, even though everyday phenomena seem to take place in only 3 large dimensions. In “Brane World” models, matter and radiation are localized to a “brane” which has a thickness less than ≈(TeV)−1in all but the usual three dimensions, while gravity propagates in additional dimensions, some of which may extend as far as submillimeter scales. A brief review is presented of some of these models and their astrophysical phenomenology. One distinctive possibility is a gravitational wave background originating in the mesoscopic early universe, at temperatures above about 1 TeV and on scales smaller than a millimeter, during the formation of our 3-dimensional brane within a 10-dimensional space. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1419526

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We study bulk timelike geodesics in the presence of a brane-world black hole, where the brane -world is a two-brane moving in a3+1-dimensional asymptoticallyadS4spacetime. We show that for a certain range of the parameters measuring the black hole mass and bulk cosmological constant, there exist stable timelike geodesics which orbit the black hole and remain bound close to the two-brane. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1419527

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We investigate brane physics in a universe with an extra dimensional global monopole and negative bulk cosmological constant. To counter divergence of the graviton zero mode, we employ a physical cut-off. This cut-off yields 4D gravity on a brane at the monopole core; it also solves the hierarchy problem, by inducing the observed hierarchy between particle and Planck scales in the effective 4D universe. Our model has a discrete spectrum of massive Kaluza Klein modes, easily made consistent with 4D gravity on the brane. Extra-dimensional matter fields also induce 4D matter fields on the brane, with the same Kaluza Klein spectrum of excited states. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1419528

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We present the results of a systematic investigation of the qualitative behavior of the Friedmann-Lemaı⁁tre-Robertson-Walker (FLRW) and Bianchi I and V cosmological models in Randall-Sundrum brane-world type scenarios. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1419529

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

In hybrid inflation models, typically only a tiny fraction of possible initial conditions give rise to successful inflation, even if one assumes spatial homogeneity. We show that hybrid inflation on the brane is not afflicted by this problem. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1419530

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The recent data from the Boomerang and MAXIMA-1 balloon flights have marked the beginning of the precision era of Cosmic Microwave Background anisotropy (CMB) measurements. We discuss the observational constraints from the current CMB anisotropy measurements on the simplest inflation models, characterized by a single scalar field &fgr;, in the parameter space consisting of scalar spectral indexnSand tensor/scalar ratior. The data are consistent with the simplest assumption of a scale invariant power spectrum, but the specific error contours in ther−nplane depend on prior assumptions, particularly the baryon density of the universe and the reionization history. Models with significant “red” tilt(n<1)and appreciable tensor fluctuations are disfavored in all cases. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1419531

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We propose a chaotic inflation model in supergravity. In this model, the form of Ka¨hler potential is determined by a symmetry, that is, the Nambu-Goldstone like shift symmetry, which guarantees the absence of the exponential factor in the potential for the inflation field. Though we need introduction of small parameters, the smallness of parameters is justified also by symmetries. That is, the zero limit of small parameters recovers symmetries, which is natural in ’t Hooft’s sense. The leptogenesis scenario via the inflation decay in this chaotic inflation model is also discussed. We find that the lepton asymmetry enough to explain the present baryon number density is produced for low reheating temperatures avoiding the overproduction of gravitinos. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1419532

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We investigate the propagation of light for metrics in which the approximation of geometrical (ray) optics breaks down due to nonadiabatically rapid (in space or time) variations of the curved-spacetime geometry. This may lead to wavelength-dependent effects such as diffraction and dispersion. The rapidly-expanding cosmological spacetimes are good candidate metrics for such effects. We find that conformal invariance prevents such violations of adiabaticity for the spatially-flat Friedmann Robertson-Walker metric; but if one breaks conformal invariance via the anisotropic (but homogeneous) Kasner metrics, then the propagation of light waves will be shown to deviate from the predictions of simple ray-tracing. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1419533

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We have researched the Universe vacuum properties (vacuum self-organization) that is the problem of the cosmological constant. This problem can’t be solved in terms of the current quantum field theory which operates with Higgs and nonperturbative vacuum condensates and takes into account the changes of these condensates during relativistic phase transitions. The problem can’t be completely solved also in terms of the conventional global quantum theory: Wheeler-DeWitt quantum geometrodynamics does not describe the evolution of the Universe in time (relativistic phase transitions in particular). We have investigated this problem in the context of energies density of different vacuum subsystems characteristic scales of which pervaid all energetic scale of the Universe. The transformation of the cosmological constant in dynamical variable is inevitably. The change of vacuum parameters brings to catastrophic consequences for the Universe (the antropic principle). ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1419534

出版商:AIP    

年代:1901

数据来源: AIP