60 research outputs found
Tachyon Condensation and Background Independent Superstring Field Theory
We study quantum corrections at the one loop level in open superstring
tachyon condensation using the boundary string field theory (BSFT) method. We
find that the tachyon field action has the same form as at the disc level, but
with a renormalized effective coupling
( is the renormalized dimensionless closed string coupling,
is the tachyonic field expectation value) and with an effective
string tension. This result is in agreement with that based on general analysis
of loop effects.Comment: 22 pages, LaTe
Sigma model approach to string theory effective actions with tachyons
Motivated by recent discussions of actions for tachyon and vector fields
related to tachyon condensation in open string theory we review and clarify
some aspects of their derivation within sigma model approach. In particular, we
demonstrate that the renormalized partition function of boundary sigma
model gives the effective action for massless vectors which is consistent with
string S-matrix and beta function, resolving an old problem with this
suggestion in bosonic string case at the level of the leading
derivative corrections to Born-Infeld action. We give manifestly gauge
invariant definition of in non-abelian NSR open string theory and
check that its derivative reproduces the tachyon beta function in a particular
scheme. We also discuss derivation of similar actions for tachyon and massless
modes in closed bosonic and NSR (type 0) string theories.Comment: 26 pages, harvmac. To appear in the special issue of J. Math. Phys.
on Strings, Branes and M-theory. v4: minor editorial changes, version to
appear in JM
On the dynamical generation of the Maxwell term and scale invariance
Gauge theories with no Maxwell term are investigated in various setups. The
dynamical generation of the Maxwell term is correlated to the scale invariance
properties of the system. This is discussed mainly in the cases where the gauge
coupling carries dimensions. The term is generated when the theory contains a
scale explicitly, when it is asymptotically free and in particular also when
the scale invariance is spontaneously broken. The terms are not generated when
the scale invariance is maintained. Examples studied include the large
limit of the model in dimensions, a 3D gauged
vector model and its supersymmetric extension. In the latter case the
generation of the Maxwell term at a fixed point is explored. The phase
structure of the case is investigated in the presence of a Chern-Simons
term as well. In the supersymmetric model the emergence of the Maxwell
term is accompanied by the dynamical generation of the Chern-Simons term and
its multiplet and dynamical breaking of the parity symmetry. In some of the
phases long range forces emerge which may result in logarithmic confinement.
These include a dilaton exchange which plays a role also in the case when the
theory has no gauge symmetry. Gauged Lagrangian realizations of the 2D coset
models do not lead to emergent Maxwell terms. We discuss a case where the gauge
symmetry is anomalous.Comment: 38 pages, 4 figures; v2 slightly improved, typos fixed, references
added, published versio
The Orbifold-String Theories of Permutation-Type: I. One Twisted BRST per Cycle per Sector
We resume our discussion of the new orbifold-string theories of
permutation-type, focusing in the present series on the algebraic formulation
of the general bosonic prototype and especially the target space-times of the
theories. In this first paper of the series, we construct one twisted BRST
system for each cycle in each twisted sector of the general case,
verifying in particular the previously-conjectured algebra
of the BRST charges. The BRST systems
then imply a set of extended physical-state conditions for the matter of each
cycle at cycle central charge where
is the length of cycle .Comment: 31 page
Time Evolution via S-branes
Using S(pacelike)-branes defined through rolling tachyon solutions, we show
how the dynamical formation of D(irichlet)-branes and strings in tachyon
condensation can be understood. Specifically we present solutions of S-brane
actions illustrating the classical confinement of electric and magnetic flux
into fundamental strings and D-branes. The role of S-branes in string theory is
further clarified and their RR charges are discussed. In addition, by examining
``boosted'' S-branes, we find what appears to be a surprising dual S-brane
description of strings and D-branes, which also indicates that the critical
electric field can be considered as a self-dual point in string theory. We also
introduce new tachyonic S-branes as Euclidean counterparts to non-BPS branes.Comment: 62 pages, 10 figures. v2 references adde
The Boundary State Formalism and Conformal Invariance in Off-shell String Theory
We present a generalization of the boundary state formalism for the bosonic
string that allows us to calculate the overlap of the boundary state with
arbitrary closed string states. We show that this generalization exactly
reproduces world-sheet sigma model calculations, thus giving the correct
overlap with both on- and off-shell string states, and that this new boundary
state automatically satisfies the requirement for integrated vertex operators
in the case of non-conformally invariant boundary interactions.Comment: 19 pages, 0 figure
Tachyon Condensation, Boundary State and Noncommutative Solitons
We discuss the tachyon condensation in a single unstable D-brane in the
framework of boundary state formulation. The boundary state in the background
of the tachyon condensation and the NS B-field is explicitly constructed. We
show in both commutative theory and noncommutative theory that the unstable
D-branes behaves like an extended object and eventually reduces to the lower
dimensional D-branes as the system approaches the infrared fixed point. We
clarify the relationship between the commutative field theoretical description
of the tachyon condensation and the noncommutative one.Comment: Revtex, 1 figure, References adde
Open strings in relativistic ion traps
Electromagnetic plane waves provide examples of time-dependent open string
backgrounds free of corrections. The solvable case of open strings in
a quadrupolar wave front, analogous to pp-waves for closed strings, is
discussed. In light-cone gauge, it leads to non-conformal boundary conditions
similar to those induced by tachyon condensates. A maximum electric gradient is
found, at which macroscopic strings with vanishing tension are pair-produced --
a non-relativistic analogue of the Born-Infeld critical electric field. Kinetic
instabilities of quadrupolar electric fields are cured by standard atomic
physics techniques, and do not interfere with the former dynamic instability. A
new example of non-conformal open-closed duality is found. Propagation of open
strings in time-dependent wave fronts is discussed.Comment: 43 pages, 11 figures, Latex2e, JHEP3.cls style; v2: one-loop
amplitude corrected, open-closed duality proved, refs added, miscellaneous
improvements, see historical note in fil
String Bit Models for Superstring
We extend the model of string as a polymer of string bits to the case of
superstring. We mainly concentrate on type II-B superstring, with some
discussion of the obstacles presented by not II-B superstring, together with
possible strategies for surmounting them. As with previous work on bosonic
string we work within the light-cone gauge. The bit model possesses a good deal
less symmetry than the continuous string theory. For one thing, the bit model
is formulated as a Galilei invariant theory in dimensional
space-time. This means that Poincar\'e invariance is reduced to the Galilei
subgroup in space dimensions. Naturally the supersymmetry present in the
bit model is likewise dramatically reduced. Continuous string can arise in the
bit models with the formation of infinitely long polymers of string bits. Under
the right circumstances (at the critical dimension) these polymers can behave
as string moving in dimensional space-time enjoying the full
Poincar\'e supersymmetric dynamics of type II-B superstring.Comment: 43 pages, phyzzx require
Stochastic Tachyon Fluctuations, Marginal Deformations and Shock Waves in String Theory
Starting with exact solutions to string theory on curved spacetimes we obtain
deformations that represent gravitational shock waves. These may exist in the
presence or absence of sources. Sources are effectively induced by a tachyon
field that randomly fluctuates around a zero condensate value. It is shown that
at the level of the underlying conformal field theory (CFT) these deformations
are marginal and moreover all \a'-corrections are taken into account. Explicit
results are given when the original undeformed 4-dimensional backgrounds
correspond to tensor products of combinations of 2-dimensional CFT's, for
instance SL(2,R)/R \times SU(2)/U(1).Comment: 26 pages, harvmac, no figures. Very minor modifications, and in
addition conditions (B.3) and (B.4) were also obtained using beta-function
equations. Version to appear in Phys. Rev.
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