5,448 research outputs found
Regularization of identity based solution in string field theory
We demonstrate that an Erler-Schnabl type solution in cubic string field
theory can be naturally interpreted as a gauge invariant regularization of an
identity based solution. We consider a solution which interpolates between an
identity based solution and ordinary Erler-Schnabl one. Two gauge invariant
quantities, the classical action and the closed string tadpole, are evaluated
for finite value of the gauge parameter. It is explicitly checked that both of
them are independent of the gauge parameter.Comment: 9 pages, minor typos corrected and references adde
The Kramers equation simulation algorithm I. Operator analysis
Using an operatorial formalism, we study the Kramers equation and its
applications to numerical simulations. We obtain classes of algorithms which
may be made precise at every desired order in the time step and with
a set of free parameters which can be used to reduce autocorrelations. We show
that it is possible to use a global Metropolis test to restore Detailed
Balance.Comment: 32 pages, REVTeX 3.0, IFUP-TH-2
A Correspondence Principle for Black Holes and Strings
For most black holes in string theory, the Schwarzschild radius in string
units decreases as the string coupling is reduced. We formulate a
correspondence principle, which states that (i) when the size of the horizon
drops below the size of a string, the typical black hole state becomes a
typical state of strings and D-branes with the same charges, and (ii) the mass
does not change abruptly during the transition. This provides a statistical
interpretation of black hole entropy. This approach does not yield the
numerical coefficient, but gives the correct dependence on mass and charge in a
wide range of cases, including neutral black holes.Comment: 24 pages, one typo correcte
Black Holes with Multiple Charges and the Correspondence Principle
We consider the entropy of near extremal black holes with multiple charges in
the context of the recently proposed correspondence principle of Horowitz and
Polchinski, including black holes with two, three and four Ramond-Ramond
charges. We find that at the matching point the black hole entropy can be
accounted for by massless open strings ending on the D-branes for all cases
except a black hole with four Ramond-Ramond charges, in which case a possible
resolution in terms of brane-antibrane excitations is considered.Comment: 26 pages, harvmac, minor correction
Field-Effect Transistor on SrTiO3 with sputtered Al2O3 Gate Insulator
A field-effect transistor that employs a perovskite-type SrTiO3 single
crystal as the semiconducting channel is revealed to function as n-type
accumulation-mode device with characteristics similar to that of organic FET's.
The device was fabricated at room temperature by sputter-deposition of
amorphous Al2O3 films as a gate insulator on the SrTiO3 substrate. The
field-effect(FE) mobility is 0.1cm2/Vs and on-off ratio exceeds 100 at room
temperature. The temperature dependence of the FE mobility down to 2K shows a
thermal-activation-type behavior with an activation energy of 0.6eV
Black hole entropy reveals a 12th "dimension"
The Beckenstein-Hawking black hole entropy in string theory and its
extensions, as expressed in terms of charges that correspond to central
extensions of the supersymmetry algebra, has more symmetries than U-duality. It
is invariant under transformations of the charges, involving a 12th (or 13th)
``dimension''. This is an indication that the secret theory behind string
theory has a superalgebra involving Lorentz non-scalar extensions (that are not
strictly central), as suggested in S-theory, and which could be hidden in M- or
F- theories. It is suggested that the idea of spacetime is broader than usual,
and that a larger ``spacetime" is partially present in black holes.Comment: Latex, 20 pages, minor formatting correction
New stability results for Einstein scalar gravity
We consider asymptotically anti de Sitter gravity coupled to a scalar field
with mass slightly above the Breitenlohner-Freedman bound. This theory admits a
large class of consistent boundary conditions characterized by an arbitrary
function . An important open question is to determine which admit stable
ground states. It has previously been shown that the total energy is bounded
from below if is bounded from below and the bulk scalar potential
admits a suitable superpotential. We extend this result and show that the
energy remains bounded even in some cases where can become arbitrarily
negative. As one application, this leads to the possibility that in
gauge/gravity duality, one can add a double trace operator with negative
coefficient to the dual field theory and still have a stable vacuum
Counting States of Black Strings with Traveling Waves
We consider a family of solutions to string theory which depend on arbitrary
functions and contain regular event horizons. They describe six dimensional
extremal black strings with traveling waves and have an inhomogeneous
distribution of momentum along the string. The structure of these solutions
near the horizon is studied and the horizon area computed. We also count the
number of BPS string states at weak coupling whose macroscopic momentum
distribution agrees with that of the black string. It is shown that the number
of such states is given by the Bekenstein-Hawking entropy of the black string
with traveling waves.Comment: 21 pages RevTex. One equation correcte
Comments on Black Holes in Matrix Theory
The recent suggestion that the entropy of Schwarzschild black holes can be
computed in matrix theory using near-extremal D-brane thermodynamics is
examined. It is found that the regime in which this approach is valid actually
describes black strings stretched across the longitudinal direction, near the
transition where black strings become unstable to the formation of black holes.
It is argued that the appropriate dynamics on the other (black hole) side of
the transition is that of the zero modes of the corresponding super Yang-Mills
theory. A suggestive mean field theory argument is given for the entropy of
black holes in all dimensions. Consequences of the analysis for matrix theory
and the holographic principle are discussed.Comment: 15 pages, harvmac, minor errors correcte
Delta Excitations in Neutrino-Nucleus Scattering
We derive the contribution of -h excitations to quasielastic
charged-current neutrino-nucleus scattering in the framework of relativistic
mean-field theory. We discuss the effect of production on the
determination of the axial mass in neutrino scattering experiments.Comment: 14 pages, revtex, 3 postscript figures (available upon request
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