70 research outputs found
Closed String Amplitudes from Gauge Fixed String Field Theory
Closed string diagrams are derived from cubic open string field theory using
a gauge fixed kinetic operator. The basic idea is to use a string propagator
that does not generate a boundary to the world sheet. Using this propagator and
the closed string vertex, the moduli space of closed string surfaces is
covered, so closed string scattering amplitudes should be reproduced. This
kinetic operator could be a gauge fixed form of the string field theory action
around the closed string vacuum.Comment: 10 pages, revtex, 3 figures. Discussion on the covering of moduli
expanded, version to appear in PR
Linking the trans-Planckian and the information loss problems in black hole physics
The trans-Planckian and information loss problems are usually discussed in
the literature as separate issues concerning the nature of Hawking radiation.
Here we instead argue that they are intimately linked, and can be understood as
"two sides of the same coin" once it is accepted that general relativity is an
effective field theory.Comment: 10 pages, 2 figures. Replaced with the version to be published in
General Relativity and Gravitatio
On different actions for the vacuum of bosonic string field theory
We study a family of kinetic operators in string field theory describing the
theory around the closed string vacuum. Those operators are based on the
analytical classical solutions of Takahashi and Tanimoto and are analogous to
the pure ghost action usually referred to as "vacuum string field theory," but
are much more general, and less singular than the pure ghost operator. The
closed string vacuum is related to the D-brane vacuum by large, singular, gauge
transformations or field redefinition, and all those different representations
are related to each other by small gauge transformations. We try to clarify the
nature of this singular gauge transformation. We also show that by choosing the
Siegel gauge one recovers the propagator proposed in hep-th/0207266 that
generates closed string surfaces.Comment: 15 page
Pre-Hawking Radiation from a Collapsing Shell
We investigate the effect of induced massive radiation given off during the
time of collapse of a massive spherically symmetric domain wall in the context
of the functional Schr\"odinger formalism. Here we find that the introduction
of mass suppresses the occupation number in the infrared regime of the induced
radiation during the collapse. The suppression factor is found to be given by
, which is in agreement with the expected Planckian distribution
of induced radiation. Thus a massive collapsing domain wall will radiate mostly
(if not exclusively) massless scalar fields, making it difficult for the domain
wall to shed any global quantum numbers and evaporate before the horizon is
formed.Comment: 10 pages, 3 figures. We updated the acknowledgments as well as added
a statement clarifying that we are following the methods first laid out in
Phys. Rev. D 76, 024005 (2007
Wet chemical etching of single-bore microstructured silicon dioxide fibers
We model the process of wet chemical etching of the external surface of a single-bore microstructured silicon dioxide fiber in hydrofluoric acid (HFA) while water is pumped through the internal channel to prevent etching of it. The model uses the Stokes flow for the velocity throughout the system and the advectionâdiffusion equation for the concentration of HFA. We determine the etch rate as a function of HFA concentration using data from experiments designed for this purpose, from which we calculate the change in the fiber surface. We solve our equations using a time-stepping finite-element method and verify our model by comparing to results found experimentally. We investigate the effects of different water flow rates, diffusivity, buoyancy, and bore radius. We find the water being pumped through the bore does not fully protect it and there is some etching of the internal channel, which is difficult to see in experimental images. We also obtain an estimate of the diffusivity of high-concentration HFA in water.Josef A. Giddings, Yvonne M. Stokes, Kyle J. Bachus, and Heike Ebendorff-Heideprie
Evolving Lorentzian Wormholes
Evolving Lorentzian wormholes with the required matter satisfying the Energy
conditions are discussed. Several different scale factors are used and the
corresponding consequences derived. The effect of extra, decaying (in time)
compact dimensions present in the wormhole metric is also explored and certain
interesting conclusions are derived for the cases of exponential and
Kaluza--Klein inflation.Comment: 10 pages( RevTex, Twocolumn format), Two figures available on request
from the first author. transmission errors corrected
Supersymmetry reduction of N-extended supergravities in four dimensions
We consider the possible consistent truncation of N-extended supergravities
to lower N' theories. The truncation, unlike the case of N-extended rigid
theories, is non trivial and only in some cases it is sufficient just to delete
the extra N-N' gravitino multiplets. We explore different cases (starting with
N=8 down to N'\geq 2) where the reduction implies restrictions on the matter
sector. We perform a detailed analysis of the interesting case N=2 \to N=1.
This analysis finds applications in different contexts of superstring and
M-theory dynamics.Comment: Version published on JHE
Computing in String Field Theory Using the Moyal Star Product
Using the Moyal star product, we define open bosonic string field theory
carefully, with a cutoff, for any number of string oscillators and any
oscillator frequencies. Through detailed computations, such as Neumann
coefficients for all string vertices, we show that the Moyal star product is
all that is needed to give a precise definition of string field theory. The
formulation of the theory as well as the computation techniques are
considerably simpler in the Moyal formulation. After identifying a monoid
algebra as a fundamental mathematical structure in string field theory, we use
it as a tool to compute with ease the field configurations for wedge, sliver,
and generalized projectors, as well as all the string interaction vertices for
perturbative as well as monoid-type nonperturbative states. Finally, in the
context of VSFT we analyze the small fluctuations around any D-brane vacuum. We
show quite generally that to obtain nontrivial mass and coupling, as well as a
closed strings, there must be an associativity anomaly. We identify the
detailed source of the anomaly, but leave its study for future work.Comment: 77 pages, LaTeX. v3: corrections of signs or factors (for a list of
corrections see beginning of source file
Chern-Simons Vortices in Supergravity
We study supersymmetric vortex solutions in three-dimensional abelian gauged
supergravity. First, we construct the general U(1)-gauged D=3, N=2 supergravity
whose scalar sector is an arbitrary Kahler manifold with U(1) isometry. This
construction clarifies the connection between local supersymmetry and the
specific forms of some scalar potentials previously found in the literature --
in particular, it provides the locally supersymmetric embedding of the abelian
Chern-Simons Higgs model. We show that the Killing spinor equations admit
rotationally symmetric vortex solutions with asymptotically conical geometry
which preserve half of the supersymmetry.Comment: 26 pages, LaTeX2
Solitonic Strings and BPS Saturated Dyonic Black Holes
We consider a six-dimensional solitonic string solution described by a
conformal chiral null model with non-trivial superconformal transverse
part. It can be interpreted as a five-dimensional dyonic solitonic string wound
around a compact fifth dimension. The conformal model is regular with the
short-distance (`throat') region equivalent to a WZW theory. At distances
larger than the compactification scale the solitonic string reduces to a dyonic
static spherically-symmetric black hole of toroidally compactified heterotic
string. The new four-dimensional solution is parameterised by five charges,
saturates the Bogomol'nyi bound and has nontrivial dilaton-axion field and
moduli fields of two-torus. When acted by combined T- and S-duality
transformations it serves as a generating solution for all the static
spherically-symmetric BPS-saturated configurations of the low-energy heterotic
string theory compactified on six-torus. Solutions with regular horizons have
the global space-time structure of extreme Reissner-Nordstrom black holes with
the non-zero thermodynamic entropy which depends only on conserved (quantised)
charge vectors. The independence of the thermodynamic entropy on moduli and
axion-dilaton couplings strongly suggests that it should have a microscopic
interpretation as counting degeneracy of underlying string configurations. This
interpretation is supported by arguments based on the corresponding
six-dimensional conformal field theory. The expression for the level of the WZW
theory describing the throat region implies a renormalisation of the string
tension by a product of magnetic charges, thus relating the entropy and the
number of oscillations of the solitonic string in compact directions.Comment: 27 Pages, uses RevTeX (solution for the axion field corrected,
erratum to appear in Phys. Rev. D
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