6,109 research outputs found
The nonperturbative closed string tachyon vacuum to high level
We compute the action of closed bosonic string field theory at quartic order
with fields up to level ten. After level four, the value of the potential at
the minimum starts oscillating around a nonzero negative value, in contrast
with the proposition made in [5]. We try a different truncation scheme in which
the value of the potential converges faster with the level. By extrapolating
these values, we are able to give a rather precise value for the depth of the
potential.Comment: 24 pages. v2: typos corrected, clarified extrapolation in scheme B,
and added extrapolated tachyon and dilaton vev's at the end of Section
Zeta Nonlocal Scalar Fields
We consider some nonlocal and nonpolynomial scalar field models originated
from p-adic string theory. Infinite number of spacetime derivatives is
determined by the operator valued Riemann zeta function through d'Alembertian
in its argument. Construction of the corresponding Lagrangians L starts
with the exact Lagrangian for effective field of p-adic tachyon
string, which is generalized replacing p by arbitrary natural number n and then
taken a sum of over all n. The corresponding new objects we
call zeta scalar strings. Some basic classical field properties of these fields
are obtained and presented in this paper. In particular, some solutions of the
equations of motion and their tachyon spectra are studied. Field theory with
Riemann zeta function dynamics is interesting in its own right as well.Comment: 13 pages, submitted to Theoretical and Mathematical Physic
Vortex ring refraction at large Froude numbers
We have experimentally studied the impact of an initially planar axisymmetric
vortex ring, incident at an oblique angle, upon a gravity-induced interface
separating two fluids of differing densities. After impact, the vortex ring was
found to exhibit a variety of subsequent trajectories, which we organize
according to both the incidence angle, , and the interface strength,
defined as the ratio of the Atwood and Froude numbers, . For grazing
incidence angles ( deg.) vortices either penetrate or
reflect from the interface, depending on whether the interface is weak or
strong. In some cases, reflected vortices execute damped oscillations before
finally disintegrating. For smaller incidence angles (
deg.) vortices penetrate the interface. When there is a strong interface, these
vortices are observed to curve back up toward the interface. When there is a
weak interface, these vortices are observed to refract downward, away from the
interface. The critical interface strength below which vortex ring refraction
is observed is given by .Comment: 26 pages, 11 figures; Submitted to Physical Review
Formulation of the Spinor Field in the Presence of a Minimal Length Based on the Quesne-Tkachuk Algebra
In 2006 Quesne and Tkachuk (J. Phys. A: Math. Gen. {\bf 39}, 10909, 2006)
introduced a (D+1)-dimensional -two-parameter Lorentz-covariant
deformed algebra which leads to a nonzero minimal length. In this work, the
Lagrangian formulation of the spinor field in a (3+1)-dimensional space-time
described by Quesne-Tkachuk Lorentz-covariant deformed algebra is studied in
the case where up to first order over deformation parameter
. It is shown that the modified Dirac equation which contains higher
order derivative of the wave function describes two massive particles with
different masses. We show that physically acceptable mass states can only exist
for . Applying the condition
to an electron, the upper bound for the isotropic
minimal length becomes about . This value is near to the
reduced Compton wavelength of the electron and is not incompatible with the results obtained for
the minimal length in previous investigations.Comment: 11 pages, no figur
Rolling to the tachyon vacuum in string field theory
We argue that the rolling-tachyon solution in cubic OSFT proceeds at late
times to precisely the analytic tachyon-vacuum solution constructed by Schnabl.
In addition, we demonstrate the relationship between the rolling-tachyon
solution and the standard BCFT description by showing that there is a finite
gauge transformation which relates the two.Comment: 16 pages, 5 figures, References and comments adde
A perturbative analysis of tachyon condensation
Tachyon condensation in the open bosonic string is analyzed using a
perturbative expansion of the tachyon potential around the unstable D25-brane
vacuum. Using the leading terms in the tachyon potential, Pad\'e approximants
can apparently give the energy of the stable vacuum to arbitrarily good
accuracy. Level-truncation approximations up to level 10 for the coefficients
in the tachyon potential are extrapolated to higher levels and used to find
approximants for the full potential. At level 14 and above, the resulting
approximants give an energy less than -1 in units of the D25-brane tension, in
agreement with recent level-truncation results by Gaiotto and Rastelli. The
extrapolated energy continues to decrease below -1 until reaching a minimum
near level 26, after which the energy turns around and begins to approach -1
from below. Within the accuracy of this method, these results are completely
consistent with an energy which approaches -1 as the level of truncation is
taken to be arbitrarily large.Comment: 8 pages, 3 eps figures, Latex; v2: typo correcte
Proof of vanishing cohomology at the tachyon vacuum
We prove Sen's third conjecture that there are no on-shell perturbative
excitations of the tachyon vacuum in open bosonic string field theory. The
proof relies on the existence of a special state A, which, when acted on by the
BRST operator at the tachyon vacuum, gives the identity. While this state was
found numerically in Feynman-Siegel gauge, here we give a simple analytic
expression.Comment: 19 pages, 4 figures; v2: references adde
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