7338034
Light-cone fluctuations in flat spacetimes with nontrivial topology
The quantum light-cone fluctuations in flat spacetimes with compactified spatial dimensions or with boundaries are examined. The discussion is based upon a model in which the source of the underlying metric fluctuations is taken to be quantized linear perturbations of the gravitational field. General expressions are derived, in the transverse trace-free gauge, for the summation of graviton polarization tensors, and for vacuum graviton two-point functions. Because of the fluctuating light cone, the flight time of photons between a source and a detector may be either longer or shorter than the light propagation time in the background classical spacetime. We calculate the mean deviations from the classical propagation time of photons due to the changes in the topology of the flat spacetime. These deviations are in general larger in the directions in which topology changes occur and are typically of the order of the Planck time, but they can get larger as the travel distance increases.
119090796
Fulling–Davies–Unruh effect and spontaneous excitation of an accelerated atom interacting with a quantum scalar field
Abstract We investigate, from the point of view of a coaccelerated frame, the spontaneous excitation of a uniformly accelerated two-level atom interacting with a scalar field in a thermal state at a finite temperature T and show that the same spontaneous excitation rate for the uniformly accelerated atom in the Minkowski vacuum obtained in the inertial frame can only be recovered in the coaccelerated frame assuming a thermal bath at the Fulling–Davies–Unruh temperature T FDU = a / 2 π for what appears to be the Minkowski vacuum to the inertial observer. Our discussion provides another example of a physical process different from those examined before in the literature to better understand the Fulling–Davies–Unruh effect.
119124346
Unruh effect and entanglement generation for accelerated atoms near a reflecting boundary
We study, in the framework of open systems, the entanglement generation of two independent uniformly accelerated atoms in interaction with the vacuum fluctuations of massless scalar fields subjected to a reflecting plane boundary. We demonstrate that, with the presence of the boundary, the accelerated atoms exhibit distinct features from static ones in a thermal bath at the corresponding Unruh temperature in terms of the entanglement creation at the neighborhood of the initial time. In this sense, accelerated atoms in vacuum do not necessarily have to behave as if they were static in a thermal bath at the Unruh temperature.
118525095
Lamb shift for static atoms outside a Schwarzschild black hole
We study, by separately calculating the contributions of vacuum fluctuations and radiation reaction to the atomic energy level shift, the Lamb shift of a static two-level atom interacting with real massless scalar fields in the Boulware, Unruh, and Hartle-Hawking vacuums outside a Schwarzschild black hole. We find that in the Boulware vacuum, the Lamb shift gets a correction arising as a result of the backscattering of vacuum field modes off the space-time curvature, which is reminiscent of the correction to the Lamb shift induced by the presence of cavities. However, when the Unruh and Hartle-Hawking vacua are concerned, our results show that the Lamb shift behaves as if the atom were irradiated by a thermal radiation or immersed in a thermal bath at the Hawking temperature, depending on whether the scalar field is in the Unruh or the Hartle-Hawking vacuum. Remarkably, the thermal radiation is always backscattered by the space-time geometry.
120986058
Quantum thermal aspects of uniformly accelerating charged black holes
115459673
LIGHTCONE FLUCTUATIONS AND EXTRA DIMENSIONS
119699165
STUDY ON HADRONIC DECAY OF THE LOWEST LYING GLUEBALLS WITH JPC=even++ TO TWO PSEUDOSCALAR MESONS
Taking into account the possible glueball component in the final state mesons, we investigate the hadronic decay modes of the lowest lying glueballs (G) with JPC=even++ to two pseudoscalar mesons (PP). The naive estimations of $\frac{\tilde\Gamma(G\rightarrow PP)}{\tilde\Gamma(G\rightarrow K\bar K)}$ for scalar and tensor glueballs are given.
121463466
Critical exponents of new universality classes
Abstract We calculate critical exponents of chiral Ising, XY and Heisenberg universality classes up to second order in 4 − ϵ expansion. General expressions for any number N of fermionic variables are given and compared with recent extensive 1/ N calculation and lattice simulations. The possibility that these new universality classes describe critical phenomena in certain 3D magnetic systems and in finite temperature phase transitions of 3 + 1 dimensional quantum field theories is briefly discussed.
120346822
NOETHER CHARGES, BLACK HOLES AND THE IMMIRZI PARAMETER
We have shown that terms in the action which won't contribute to local equation of motions do contribute to globally conversed physical quantities in classical theories of gravity due to general coordinate covariance. This observation allows one to determining the Immirzi parameter in the Ashtekar variable formulation of gravitational theories even at classical level. Applying Wald's Noether charge approach and identifying the entropy on black hole horizon as the Noether charge for translation, one can demonstrate explicitly that the Immirzi parameter does make its contributions through the boundary term. Our results also shed lights in connecting the Immirzi paramter to quasi-normal modes of black holes.
119123919
Fermion Mass Hierarchy and Proton Stability from Non-anomalous U(1)(F) in SUSY SU(5)
We present a realistic supersymmetric SU(5) model combined with a nonanomalous U(1){sub F} symmetry. We find a set of U(1){sub F} charges which automatically lead to the realistic mass hierarchy and mixing patterns for quarks, leptons, and neutrinos. All gauge anomalies, including the [U(1){sub F}]{sup 3} anomaly, are canceled in our model without invoking the Green-Schwarz mechanism or having exotic fields. Proton decay mediated by dimension-5 operators is automatically suppressed in our model, because the scale set by the largest right-handed neutrino mass is much less than the GUT scale.
118352399
The Origin of the Immirzi Parameter in Loop Quantum Gravity