16978340
Cosmic censorship and the dilaton.
We investigate extremal electrically charged black holes in Einstein-Maxwell-dilaton theory with a cosmological constant inspired by string theory. These solutions are not static, and a timelike singularity eventually appears which is not surrounded by an event horizon. This suggests that cosmic censorship may be violated in this theory.
23955919
Origin of gauge invariance in string theory.
We present a first quantization of the space-time embedding X/sup ..mu../ and the world-sheet metric rho of the open bosonic string. The world-sheet metric rho decouples from S-matrix elements in 26 dimensions. This formulation of the theory naturally includes 26-dimensional gauge transformations. The gauge invariance of S-matrix elements is a direct consequence of the decoupling of rho. Second quantization leads to a string field Phichemically bondX/sup ..mu../,rhochemically bond with a gauge-covariant equation of motion.
7270273
Pair creation of extremal black holes and Kaluza-Klein monopoles.
Classical solutions describing charged dilaton black holes accelerating in a background magnetic field have recently been found. They include the Ernst metric of the Einstein-Maxwell theory as a special case. We study the extremal limit of these solutions in detail, both at the classical and quantum levels. It is shown that near the event horizon the extremal solutions reduce precisely to the static extremal black hole solutions. For a particular value of the dilaton coupling, these extremal black holes are five-dimensional Kaluza-Klein monopoles. The Euclidean sections of these solutions can be interpreted as instantons describing the pair creation of extremal black holes and/or Kaluza-Klein monopoles in a magnetic field. The action of these instantons is calculated and found to agree with the Schwinger result in the weak-field limit. For the Euclidean Ernst solution, the action for the extremal solution differs from that of the previously discussed wormhole instanton by the Bekenstein-Hawking entropy. However, in many cases quantum corrections become large in the vicinity of the black hole, and the precise description of the creation process is unknown.
14670933
Microstates of a neutral black hole in M theory.
We consider vacuum solutions in M theory of the form of a five-dimensional Kaluza-Klein black hole cross T6. In a certain limit, these include the five-dimensional neutral rotating black hole (cross T6). From a type-IIA standpoint, these solutions carry D0 and D6 charges. We show that there is a simple D-brane description which precisely reproduces the Hawking-Bekenstein entropy in the extremal limit, even though supersymmetry is completely broken.
15786164
Where is the information stored in black holes
It is shown that many modes of the gravitational field exist only inside the horizon of an extreme black hole in string theory. At least in certain cases, the number of such modes is sufficient to account for the Bekenstein-Hawking entropy. These modes are associated with sources which carry Ramond-Ramond charge, and so may be viewed as the strong coupling limit of D-branes. Although these sources naturally live at the singularity, they are well defined and generate modes which extend out to the horizon. This suggests that the information in an extreme black hole is not localized near the singularity or the horizon, but extends between them.
15074147
Photoemission “experiments” on holographic superconductors
We study the effects of a superconducting condensate on holographic Fermi surfaces. With a suitable coupling between the fermion and the condensate, there are stable quasiparticles with a gap. We find some similarities with the phenomenology of the cuprates: in systems whose normal state is a non-Fermi liquid with no stable quasiparticles, a stable quasiparticle peak appears in the condensed phase.
38595082
Neutrino interactions in a dense plasma.
We investigate many-body corrections to neutrino scattering from electrons and nuclei. The Coulomb correlations of the electrons screen the weak vector neutral current. Electron screening is important only for electron neutrinos (or antineutrinos) and most effective for neutrino energies of several MeV or less. At electron densities relevant for supernovae, the total quasielastic {nu}-{ital e} cross section can be reduced by 50%, and elastic neutrino-nucleus scattering by up to 85%.
21320167
Relativistic Love-Franey model: Covariant representation of the NN interaction for N-nucleus scattering.
A Lorentz invariant form of the NN amplitude is fit with a simple model which includes direct and exchange first Born terms from a number of ''mesons.'' The (complex) couplings and nucleon-meson form factors are adjusted to fit the NN amplitudes directly without iteration. The resulting parameters agree well with one-boson-exchange potentials and have a systematic and small energy dependence. Detailed analytic representations of the relativistic NN amplitudes are provided at lab energies of 135, 200, and 400 MeV. The model separation of the NN amplitudes into direct and exchange contributions does not involve sensitive cancellations and is contrasted with the very different nonrelativistic results. The model amplitudes are used to construct optical potentials in a relativistic impulse approximation using both pseudovector and pseudoscalar ..pi..-N coupling. The pseudoscalar result reproduces earlier relativistic impulse approximation calculations which diverge at low energies, while the pseudovector results are nearly constant with energy and in good agreement with phenomenological potentials.
37677102
Microscopic relativistic description of proton-nucleus scattering.
Microscopic relativistic optical potentials have been calculated for closed shell nuclei at energies near 200 MeV. These calculations go beyond the simple RIA by resolving ambiguities in the relativistic NN amplitudes and including Pauli blocking corrections.
2626556
Meson exchange effects in parity violating electron-deuteron scattering.
We discuss heavy-meson exchange corrections in the context of parity violating quasielastic electron-deuteron scattering. We compute the meson exchange contributions to the isoscalar vector response function of the deuteron. In contrast to the case of heavy targets the corrections are found to be small.
15357267
Delta excitations in neutrino-nucleus scattering.
We derive the contribution of {Delta}-{ital h} excitations to quasielastic charged-current neutrino-nucleus scattering in the framework of relativistic mean-field theory. We discuss the effect of {Delta} production on the determination of the axial mass {ital M}{sub {ital A}} in neutrino scattering experiments. {copyright} {ital 1996 The American Physical Society.}