3,508 research outputs found
Probability of a Solution to the Solar Neutrino Problem Within the Minimal Standard Model
Tests, independent of any solar model, can be made of whether solar neutrino
experiments are consistent with the minimal Standard Model (stable, massless
neutrinos). If the experimental uncertainties are correctly estimated and the
sun is generating energy by light-element fusion in quasi-static equilibrium,
the probability of a standard-physics solution is less than 2%. Even when the
luminosity constraint is abandoned, the probability is not more than 4%. The
sensitivity of the conclusions to input parameters is explored.Comment: PRL, Revtex, 1 figure, 5 page
Predicting Big Bang Deuterium
We present new upper and lower bounds to the primordial abundances of
deuterium and helium-3 based on observational data from the solar system and
the interstellar medium. Independent of any model for the primordial production
of the elements we find (at the 95\% C.L.): and . When combined with
the predictions of standard big bang nucleosynthesis, these constraints lead to
a 95\% C.L. bound on the primordial abundance of deuterium: . Measurements of deuterium absorption in the
spectra of high redshift QSOs will directly test this prediction. The
implications of this prediction for the primordial abundances of helium-4 and
lithium-7 are discussed, as well as those for the universal density of baryons.Comment: Revised version of paper to reflect comments of the referee and reply
to suggestions of Copi, Schramm, and Turner regarding the overall analysis
and treatment of chemical evolution of D and He-3. Best-fit D/H abundance
changes from (2.3 + 3.0 - 1.0)x10^{-5} to (3.5 +2.7 - 1.8) x10^{-5}. See also
hep-ph/950531
Rolling Tachyon Solution in Vacuum String Field Theory
We construct a time-dependent solution in vacuum string field theory and
investigate whether the solution can be regarded as a rolling tachyon solution.
First, compactifying one space direction on a circle of radius R, we construct
a space-dependent solution given as an infinite number of *-products of a
string field with center-of-mass momentum dependence of the form e^{-b p^2/4}.
Our time-dependent solution is obtained by an inverse Wick rotation of the
compactified space direction. We focus on one particular component field of the
solution, which takes the form of the partition function of a Coulomb system on
a circle with temperature R^2. Analyzing this component field both analytically
and numerically using Monte Carlo simulation, we find that the parameter b in
the solution must be set equal to zero for the solution to approach a finite
value in the large time limit x^0\to\infty. We also explore the possibility
that the self-dual radius R=\sqrt{\alpha'} is a phase transition point of our
Coulomb system.Comment: 39 pages, 17 figures, v3: references adde
Semiconductor-enriched single wall carbon nanotube networks applied to field effect transistors
Substantial progress on field effect transistors "FETs" consisting of
semiconducting single wall carbon nanotubes "s-SWNTs" without detectable traces
of metallic nanotubes and impurities is reported. Nearly perfect removal of
metallic nanotubes is confirmed by optical absorption, Raman measurements, and
electrical measurements. This outstanding result was made possible in
particular by ultracentrifugation (150 000 g) of solutions prepared from SWNT
powders using polyfluorene as an extracting agent in toluene. Such s-SWNTs
processable solutions were applied to realize FET, embodying randomly or
preferentially oriented nanotube networks prepared by spin coating or
dielectrophoresis. Devices exhibit stable p-type semiconductor behavior in air
with very promising characteristics. The on-off current ratio is 10^5, the
on-current level is around 10 A, and the estimated hole mobility is larger
than 2 cm2 / V s
Time Dependent Solution in Cubic String Field Theory
We study time dependent solutions in cubic open string field theory which are
expected to describe the configuration of the rolling tachyon. We consider the
truncated system consisting of component fields of level zero and two, which
are expanded in terms of cosh n x^0 modes. For studying the large time behavior
of the solution we need to know the coefficients of all and, in particular,
large n modes. We examine numerically the coefficients of the n-th mode, and
find that it has the leading n-dependence of the form (-\beta)^n \lambda^{-n^2}
multiplied by a peculiar subleading part with peaks at
n=2^m=4,8,16,32,64,128,.... This behavior is also reproduced analytically by
solving simplified equations of motion of the tachyon system.Comment: 22 pages, 12 figures, LaTeX2e, v3:minor correction
Chan-Paton factors and Higgsing from Vacuum String Field Theory
We give a description of open strings stretched between N parallel D-branes
in VSFT. We show how higgsing is generated as the branes are displaced: the
shift in the mass formula for on-shell states stretched between different
branes is due to a twist anomaly, a contribution localized at the midpoint.Comment: 20 pages, JHEP clas
The Perturbative Spectrum of the Dressed Sliver
We analyze the fluctuations of the dressed sliver solution found in a
previous paper, hep-th/0311198, in the operator formulation of Vacuum String
Field Theory. We derive the tachyon wave function and then analyze the higher
level fluctuations. We show that the dressing is responsible for implementing
the transversality condition on the massless vector. In order to consistently
deal with the singular mode we introduce a string midpoint regulator and
we show that it is possible to accommodate all the open string states among the
solutions to the linearized equations of motion. We finally show how the
dressing can give rise to the correct ratio between the energy density of the
dressed sliver and the brane tension computed via the three-tachyons-coupling.Comment: 52 pages, v2: comment added in sec. 5, v3: one appendix added,
comments added in introduction and conclusion, to appear on PR
Boundary states as exact solutions of (vacuum) closed string field theory
We show that the boundary states are idempotent B*B=B with respect to the
star product of HIKKO type closed string field theory. Variations around the
boundary state correctly reproduce the open string spectrum with the gauge
symmetry. We explicitly demonstrate it for the tachyonic and massless vector
modes. The idempotency relation may be regarded as the equation of motion of
closed string field theory at a possible vacuum.Comment: 30 pages, 2 figures, v3:regularization improve
- âŠ