An equivalence between momentum and charge in string theory.
It is shown that for a translationally invariant solution to string theory, spacetime duality interchanges the momentum in the symmetry direction and the axion charge per unit length. As one application, we show explicitly that charged black strings are equivalent to boosted (uncharged) black strings. The extremal black strings (which correspond to the field outside of a fundamental macroscopic string) are equivalent to plane-fronted waves describing strings moving at the speed of light.

title: Pair creation of extremal black holes and Kaluza-Klein monopoles.
abstract: 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.

title: Where is the information stored in black holes
abstract: 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.

title: Photoemission “experiments” on holographic superconductors
abstract: 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.

title: Origin of gauge invariance in string theory.
abstract: 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.

title: Microstates of a neutral black hole in M theory.
abstract: 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.

title: Nuclear to quark-matter transition in the string-flip model.
abstract: We have calculated ground-state properties of nuclear matter in a simple string-flip quark model in one dimension. Special emphasis was placed on the transition from hadron to quark matter and to the response of the system to color fields. Numerical simulations involving a large number of quarks were carried out for two- and three-quark clusters. This in turn enabled us to investigate the hadron-to-quark transition through the study of finite-size effects. The concept of a sudden-quark potential was introduced as an example of a generic response of the medium to color fields. We have argued that this response might be relevant to the propagation of a rapidly moving quark-antiquark pair (e.g., J/ψ meson) through the medium

title: Neutrino interactions in a dense plasma.
abstract: 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%.

title: Neutrino-nucleus quasifree neutral current reactions and the nucleon strange quark content.
abstract: Differential cross sections for neutrino- (and antineutrino-) induced nucleon knockout are calculated for neutral-current reactions from nuclei. A relativistic Fermi gas model with binding energy corrections is used. We examine the accuracy with which strange quark axial and vector current parameters can be extracted from both existing and (possible) future experiments. Both high (above 1 GeV) and low (near 150 MeV) neutrino energies and the knockout of neutrons and protons are considered.

title: Role of heavy-meson exchange in pion production near threshold.
abstract: Recent calculations of s-wave pion production have severely underestimated the accurately known pp → pp� 0 total cross section near threshold. In these calculations, only the single-nucleon axial-charge operator is considered. We have calculated, in addition to the one-body term, the two-body contributions to this reaction that arise from the exchange of mesons. We find that the inclusion of the scalar �-meson exchange current (and lesser contributions from other mesons) increases the cross section by about a factor of five, and leads to excellent agreement with the data. The results are neither very sensitive to changes in the distorting potential that generates the NN wave function, nor to different choices for the meson-nucleon form factors. We argue that pp → pp� 0 data provide direct experimental evidence for meson

title: Relativistic and nuclear structure effects in parity-violating quasielastic electron scattering.
abstract: The parity-violating longitudinal asymmetry [ital scrA] is calculated for quasielastic electron scattering. We use a varietry of relativistic mean field models for the response of nuclear matter and [sup 12]C at a momentum transfer of [ital q]=550 MeV/[ital c]. Relativistic effects from a reduced nucleon mass, RPA correlations, and vacuum polarization can all change [ital scrA] by a relatively large amount. These large nuclear structure corrections could make it impossible to extract strange quark matrix elements or radiative corrections to weak axial currents.