119112712
The Friedmann Universe and Compact Internal Spaces in Higher-Dimensional Gravity Theories
We consider gravity theories in 4 + N dimensions which are governed by the Lagrangian written as an extended Gauss-Bonnet density. We can find a naturally generalized Einstein gravity where the maximal symmetric compactification leads to vanishing four-dimensional cosmological constant in the static limit. A later stage in the generalized Kaluza-Klein cosmology is also examined. In the last decade, the unification of the gauge interactions and the gravity through higher dimensions has much interest.[1] This renewed Kaluza-Klein idea is originated from the study of supergravity theories[2] and superstring theories,[3] which have a simple or unique structure in higher dimensions than four. Most attractive feature of Kaluza-Klein theories is that the isometry group of compact extra spaces will be viewed as the gauge symmetry group in the four-dimensional effective theory.[1] Various gauge groups can be obtained as a consequence of the corresponding compactification in the Kaluza-Klein (super) gravity.[2] Another aspect of the Kaluza-Kein model is the cosmological evolution of the scale factors. In the early universe, it is natural to expect the “dimensional reduction transition”[4] which explains the reason why the length scale of extra spaces is too small to be obervable. And also, we can ask whether the cosmological inflation associated with this phase transition takes place or not.[5] However, before such investigations, we have to explain why the four-dimensional cosmological constant is so small in our universe.[6] From the cosmological observation it follows that the cosmological constant in the universe at present cannot be greater than the critical density ∼ 10 120 m 4 . In usual Kaluza-Klein supergravity theories, though the higher-dimensional cosmological term is forbidden by supersymmetry, the compactification of extra spaces brings about a large four-dimensional cosmological constant ∼ m 4 . On the other hand, in nonsuper-theories, we can adjust the higher-dimensional cosmological constant in order to lead a vanishing four-dimensional cosmological constant. However, this
53378499
Classical and quantum cosmology of multigravity
Recently, a multigraviton theory on a simple closed circuit graph corresponding to the discretization of S1 compactification of the Kaluza–Klein (KK) theory has been considered. In the present paper, we extend this theory to that on a general graph and study what modes of particles are included. Furthermore, we generalize it in a possible nonlinear theory based on the vierbein formalism and study classical and quantum cosmological solutions in the theory. We found that scale factors in a solution for this theory repeat acceleration and deceleration.
118693225
GAUGE FIELDS ON TORUS AND PARTITION FUNCTION OF STRINGS
In this paper we consider the interrelation between compactified string theories on torus and gauge fields on it. We start from open string theories with background gauge fields and derive partition functions by path integral. Since the effects of background fields and compactification correlate only through string zero modes, we investigate these zero modes. From this point of view, we discuss the Wilson loop mechanism at finite temperature. For the closed string, only a few comments are mentioned.
102352448
Exact solutions for gravitational collapse with a dilaton field in arbitrary dimensions
We present time-dependent analytic solutions to the Einstein equations coupled with a dilaton (scalar) field. The background geometry for the solutions is a product of an N-dimensional spherically symmetric space and a d-dimensional flat space. We discuss the global properties of the spacetime.
118536921
Quantum Corrections to Scattering Amplitude in Conical Space-time
It is known that the vacuum polarization of zero-point field arises around a conical singularity generated by an infinite, straight cosmic string. In this paper we study quantum electromagnetic corrections to the gravitational Aharonov-Bohm effect around a cosmic string. We find the scattering amplitude from a conical defect for charged Klein-Gordon field.
118476788
Hosotani mechanism in higher dimensional Lee-Wick theory
Hosotani mechanism in higher-dimensional Lee-Wick theory is investigated. The symmetry breaking mechanism proposed by Hosotani is studied at one-loop level through a toy model in this theory. We find that the phase diagram of symmetry and masses of fields are modified from the original one if masses of Lee-Wick particles are in the same order of the inverse of the compactification scale.
118234841
Super-kamiokande atmospheric neutrino analysis of matter-dependent neutrino oscillation models