4,977 research outputs found
On the Supersymmetry and Gauge Structure of Matrix Theory
Supersymmetric Ward identity for the low energy effective action in the
standard background gauge is derived for {\it arbitrary} trajectories of
supergravitons in Matrix Theory. In our formalism, the quantum-corrected
supersymmetry transformation laws of the supergravitons are directly identified
in closed form, which exhibit an intricate interplay between supersymmetry and
gauge (BRST) symmetry. As an application, we explicitly compute the
transformation laws for the source-probe configuration at 1-loop and confirm
that supersymmetry fixes the form of the action completely, including the
normalization, to the lowest order in the derivative expansion.Comment: 29 pages, 1 figur
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
Winding Number in String Field Theory
Motivated by the similarity between cubic string field theory (CSFT) and the
Chern-Simons theory in three dimensions, we study the possibility of
interpreting N=(\pi^2/3)\int(U Q_B U^{-1})^3 as a kind of winding number in
CSFT taking quantized values. In particular, we focus on the expression of N as
the integration of a BRST-exact quantity, N=\int Q_B A, which vanishes
identically in naive treatments. For realizing non-trivial N, we need a
regularization for divergences from the zero eigenvalue of the operator K in
the KBc algebra. This regularization must at same time violate the
BRST-exactness of the integrand of N. By adopting the regularization of
shifting K by a positive infinitesimal, we obtain the desired value
N[(U_tv)^{\pm 1}]=\mp 1 for U_tv corresponding to the tachyon vacuum. However,
we find that N[(U_tv)^{\pm 2}] differs from \mp 2, the value expected from the
additive law of N. This result may be understood from the fact that \Psi=U Q_B
U^{-1} with U=(U_tv)^{\pm 2} does not satisfy the CSFT EOM in the strong sense
and hence is not truly a pure-gauge in our regularization.Comment: 20 pages, no figures; v2: references added, minor change
Tachyon Vacuum in Cubic Superstring Field Theory
In this paper we give an exact analytic solution for tachyon condensation in
the modified (picture 0) cubic superstring field theory. We prove the absence
of cohomology and, crucially, reproduce the correct value for the D-brane
tension. The solution is surprising for two reasons: First, the existence of a
tachyon vacuum in this theory has not been definitively established in the
level expansion. Second, the solution {\it vanishes} in the GSO sector,
implying a ``tachyon vacuum'' solution exists even for a {\it BPS} D-brane.Comment: 16 pages, 2 figure
The boundary state for a class of analytic solutions in open string field theory
We construct a boundary state for a class of analytic solutions in the
Witten's open string field theory. The result is consistent with the property
of the zero limit of a propagator's length, which was claimed in [19]. And we
show that our boundary state becomes expected one for the perturbative vacuum
solution and the tachyon vacuum solution. We also comment on possible presence
of multi-brane solutions and ghost brane solutions from our boundary state.Comment: 19 pages, 2 figure
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