119682398
Relationship between Hawking radiation from black holes and spontaneous excitation of atoms
Using the formalism that separates the contributions of vacuum fluctuations and radiation reaction to the rate of change of the mean atomic energy, we show that a two-level atom in interaction with a quantum massless scalar field both in the Hartle-Hawking and Unruh vacuum in a $1+1$ dimensional black hole background spontaneously excites as if there is thermal radiation at the Hawking temperature emanating from the black hole. Our calculation, therefore, ties the existence of Hawking radiation to the spontaneous excitation of a two-level atom placed in vacuum in the exterior of a black hole and shows pleasing consistence of two different physical phenomena, the Hawking radiation and the spontaneous excitation of atoms, which are quite prominent in their own right.
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.
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.
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.
120986058
Quantum thermal aspects of uniformly accelerating charged black holes
115459673
LIGHTCONE FLUCTUATIONS AND EXTRA DIMENSIONS
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.
123617602
Pionic contribution to the proton spin
Abstract We estimate the contribution to the proton spin due to the orbital angular momentum of the pion cloud in a physical proton.
118352399
The Origin of the Immirzi Parameter in Loop Quantum Gravity
120093276
CONSISTENT FACTORIZATION AND TWIST-3 CONTRIBUTIONS TO THE POLARIZED NUCLEON STRUCTURE FUNCTION g2(x,Q2)
Quark mass effects are clarified in the parton model approach to the transversely polarized nucleon structure function. The special propagator technique is employed to obtain manifestly gauge invariant results and extract the buried short-distance contributions inside the soft part after momentum factorization in the collinear expansion approach. A generalized massive special propagator for a massive quark is constructed. We identify the corresponding matrix elements of the transversely polarized structure function in deep inelastic scattering by the massive special propagator technique.
43002203
Black holes and Rindler superspace: Classical singularity and quantum unitarity
Canonical quantization of spherically symmetric initial data appropriate to classical interior black hole solutions in four dimensions is solved exactly without gauge fixing the remaining kinematic Gauss law constraint. The resultant mini-superspace manifold is two dimensional, of signature (+, -), nonsingular, and can be identified with the first Rindler wedge. The associated Wheeler-DeWitt equation with evolution in intrinsic superspace time is a free massive Klein-Gordon equation, and the Hamilton-Jacobi semiclassical limit of plane wave solutions can be matched to the interiors of Schwarzschild black holes. Classical black hole horizons and singularities correspond to the boundaries of the Rindler wedge. Exact wave functions of the Dirac equation in superspace are also considered. Precise correspondence between Schwarzschild black holes and free-particle mechanics in superspace is noted. Despite the presence of classical singularities, Hermiticity of the Dirac Hamiltonian operator, and thus unitarity of the quantum theory, is equivalent to an appropriate boundary condition which must be satisfied by the quantum states. This boundary condition holds for quite generic quantum wave packets of energy eigenstates, but fails for the usual Rindler fermion modes which are eigenstates with zero uncertainty in energy.