498 research outputs found
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
Particle bombardment as a strategy for the production of transgenic high oleic sunflower (Helianthus annuus L.)
In order to develop an efficient and reproducible protocol for genetic engineering of high oleic Helianthus annuus L. genotypes (cv. capella and SWSR2 inbred line) important parameters of a particle bombardment strategy have been optimized, such as gold particle size, particle acceleration pressure, distance between macrocarrier assembly and target plate, pre-culture period of the explant and number of bombardments per explant. These parameters were evaluated on the basis of resulting GUS activity coupled with regeneration frequency and efficiency as well as plant cell vitality. Split shoot apices were used as explants. The maximum GUS activity was observed at 1550 psi acceleration pressure combined with 6 cm target distance and 1.6 μm gold particle size. A pre-culture of one day prior to bombardment gave the best results. In addition, two subsequent bombardments increased the GUS activity of cv.capella and SWSR2 inbred line 1.6 and 2.1 fold, respectively, compared to explants bombarded once. The optimized bombardment conditions were applied for estimating the transformation frequency which reached 3.1 and 4.5 % for high oleic cv.capella and SWSR2 inbred line, respectively. This frequency was calculated on the basis of positive PCR results of putative transgenic plants and in relation to the total number of bombarded explants.Abbreviations: MUG – 4-methylumbelliferyl-ß-glucuronide; 4-MU – 4-methylumbelliferone; BAP – 6-benzylaminopurine; gus – β- glucuronidase; MS – Murashige and Skoog; nos – nopaline synthase gene; nptII – neomycin phosphotransferase gene; psi – pounds per square inch; SE – standard error; SIM – shoot induction mediu
Marginal deformations in string field theory
We describe a method for obtaining analytic solutions corresponding to exact
marginal deformations in open bosonic string field theory. For the photon
marginal deformation we have an explicit analytic solution to all orders. Our
construction is based on a pure gauge solution where the gauge field is not in
the Hilbert space. We show that the solution itself is nevertheless perfectly
regular. We study its gauge transformations and calculate some coefficients
explicitly. Finally, we discuss how our method can be implemented for other
marginal deformations.Comment: 23 pages. v2: Some paragraphs improved, typos corrected, ref adde
Level Truncated Tachyon Potential in Various Gauges
New gauge fixing condition with single gauge parameter proposed by the
authors is applied to the level truncated analysis of tachyon condensation in
cubic open string field theory. It is found that the only one real non-trivial
extremum persists to appear in the well-defined region of the gauge parameter,
while the other solutions are turned out to be gauge-artifacts. Contrary to the
previously known pathology in the Feynman-Siegel gauge, tachyon potential is
remarkably smooth enough around Landau-type gauge.Comment: 13 pages, 5 figures. For associated movie files, see
http://hep1.c.u-tokyo.ac.jp/~kato/sft
On the validity of the solution of string field theory
We analyze the realm of validity of the recently found tachyon solution of
cubic string field theory. We find that the equation of motion holds in a non
trivial way when this solution is contracted with itself. This calculation is
needed to conclude the proof of Sen's first conjecture. We also find that the
equation of motion holds when the tachyon or gauge solutions are contracted
among themselves.Comment: JHEP style, 9+1 pages. Typos correcte
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
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
Comments on Schnabl's analytic solution for tachyon condensation in Witten's open string field theory
Schnabl recently constructed an analytic solution for tachyon condensation in
Witten's open string field theory. The solution consists of two pieces. Only
the first piece is involved in proving that the solution satisfies the equation
of motion when contracted with any state in the Fock space. On the other hand,
both pieces contribute in evaluating the kinetic term to reproduce the value
predicted by Sen's conjecture. We therefore need to understand why the second
piece is necessary. We evaluate the cubic term of the string field theory
action for Schnabl's solution and use it to show that the second piece is
necessary for the equation of motion contracted with the solution itself to be
satisfied. We also present the solution in various forms including a pure-gauge
configuration and provide simpler proofs that it satisfies the equation of
motion.Comment: 33 pages, 4 figures, LaTeX2e; v2: minor changes, version published in
JHE
The off-shell Veneziano amplitude in Schnabl gauge
We give a careful definition of the open string propagator in Schnabl gauge
and present its worldsheet interpretation. The propagator requires two
Schwinger parameters and contains the BRST operator. It builds surfaces by
gluing strips of variable width to the left and to the right of off-shell
states with contracted or expanded local frames. We evaluate explicitly the
four-point amplitude of off-shell tachyons. The computation involves a subtle
boundary term, crucial to enforce the correct exchange symmetries.
Interestingly, the familiar on-shell physics emerges even though string
diagrams produce Riemann surfaces more than once. Off-shell, the amplitudes do
not factorize over intermediate on-shell states.Comment: 48 pages, 10 figures. v2:acknowledgments adde
Tachyon Vacuum Solution in Open String Field Theory with Constant B Field
We show that Schnabl's tachyon vacuum solution is an exact solution of the
equation of motion of Witten's open bosonic string field theory in the
background of constant antisymmetric two-form field. The action computed at the
vacuum solution is given by the Dirac-Born-Infeld factor multiplied to that
without the antisymmetric tensor field.Comment: 8 page
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