22 research outputs found
New Global Defect Structures
We investigate the presence of defects in systems described by real scalar
field in (D,1) spacetime dimensions. We show that when the potential assumes
specific form, there are models which support stable global defects for D
arbitrary. We also show how to find first-order differential equations that
solve the equations of motion, and how to solve models in D dimensions via
soluble problems in D=1. We illustrate the procedure examining specific models
and finding explicit solutions.Comment: RevTex4, 4 pages, 3 eps figures; to be published in Phys. Rev. Let
Tachyon Tube on non BPS D-branes
We report our searches for a single tubular tachyonic solution of regular
profile on unstable non BPS D3-branes. We first show that some extended
Dirac-Born-Infeld tachyon actions in which new contributions are added to avoid
the Derrick's no-go theorem still could not have a single regular tube
solution. Next we use the Minahan-Zwiebach tachyon action to find the regular
tube solutions with circular or elliptic cross section. With a critical
electric field, the energy of the tube comes entirely from the D0 and strings,
while the energy associated to the tubular D2-brane tension is vanishing. We
also show that fluctuation spectrum around the tube solution does not contain
tachyonic mode. The results are consistent with the identification of the
tubular configuration as a BPS D2-brane.Comment: Latex 18 page
Realization of Brane Descent Relations in Effective Theories
We examine Sen's descent relations among (non-)BPS D-branes by using low
energy effective field theories of DpDpbar system. We find that the fluctuation
around the kink solution reproduces the low energy matter content on a non-BPS
D(p-1)-brane. The effective action for these fluctuation modes turns out to be
a generalization of Minahan-Zwiebach model. In addition, it is shown that the
fluctuations around the vortex solution consist of massless fields on a BPS
D(p-2)-brane and they are subject to Dirac-Born-Infeld action. We find the
universality that the above results do not refer to particular forms of the
effective action.Comment: 24 pages, LaTeX, 1 eps figure; v2:minor correction
Rolling Tachyon
We discuss construction of classical time dependent solutions in open string
(field) theory, describing the motion of the tachyon on unstable D-branes.
Despite the fact that the string field theory action contains infinite number
of time derivatives, and hence it is not a priori clear how to set up the
initial value problem, the theory contains a family of time dependent solutions
characterized by the initial position and velocity of the tachyon field. We
write down the world-sheet action of the boundary conformal field theories
associated with these solutions and study the corresponding boundary states.
For D-branes in bosonic string theory, the energy momentum tensor of the system
evolves asymptotically towards a finite limit if we push the tachyon in the
direction in which the potential has a local minimum, but hits a singularity if
we push it in the direction where the potential is unbounded from below.Comment: LaTeX file, 20 pages, references adde
Stretched strings in tachyon condensation models
In this note, we consider the two derivative truncation of boundary string
field theory for unstable D9 branes in Type IIA string theory. We construct
multiples of the stable codimension 1 solitons that correspond to stacks of D8
branes. We find the fluctuation modes that correspond to open strings
stretching between the branes, and find that their masses are consistent with
the string tension. We show that these modes are localized halfway between the
branes and that their width is independent of the brane separation.Comment: 12 pages, LaTeX; v2, references adde
From Free Fields to AdS -- II
We continue with the program of hep-th/0308184 to implement open-closed
string duality on free gauge field theory (in the large limit). In this
paper we consider correlators such as \la \prod_{i=1}^n
\Tr\Phi^{J_i}(x_i)\ra. The Schwinger parametrisation of this -point
function exhibits a partial gluing up into a set of basic skeleton graphs. We
argue that the moduli space of the planar skeleton graphs is exactly the same
as the moduli space of genus zero Riemann surfaces with holes. In other
words, we can explicitly rewrite the -point (planar) free field correlator
as an integral over the moduli space of a sphere with holes. A preliminary
study of the integrand also indicates compatibility with a string theory on
. The details of our argument are quite insensitive to the specific form
of the operators and generalise to diagrams of higher genus as well. We take
this as evidence of the field theory's ability to reorganise itself into a
string theory.Comment: 26 pages, 2 figures; v2. some additional comments, references adde
Dual equivalence in models with higher-order derivatives
We introduce a class of higher-order derivative models in (2,1) space-time
dimensions. The models are described by a vector field, and contain a
Proca-like mass term which prevents gauge invariance. We use the gauge
embedding procedure to generate another class of higher-order derivative
models, gauge-invariant and dual to the former class. We show that the results
are valid in arbitrary (d,1) space-time dimensions when one discards the
Chern-Simons and Chern-Simons-like terms. We also investigate duality at the
quantum level, and we show that it is preserved in the quantum scenario. Other
results include investigations concerning the gauge embedding approach when the
vector field couples with fermionic matter, and when one adds nonlinearity.Comment: RevTex4, 14 pages; new version includes duality at the quantum level,
and new references. To be published in J. Phys.
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
Dynamical Decay of Brane-Antibrane and Dielectric Brane
Using D-brane effective field theories, we study dynamical decay of unstable
brane systems : (i) a parallel brane-antibrane pair with separation l and (ii)
a dielectric brane. In particular we give explicitly the decay width of these
unstable systems, and describe how the decay proceeds after the tunnel effect.
The decay (i) is analysed by the use of a tachyon effective action on the
Dp-Dpbar. A pair annihilation starts by nucleation of a bubble of a tachyon
domain wall which represents a throat connecting these branes, and the
tunneling decay width is found to be proportional to exp(-l^{p+1} T_{Dp}). We
study also the decay leaving topological defects corresponding to
lower-dimensional branes, which may be relevant for recent inflationary
braneworld scenario. As for the decay (ii), first we observe that Dp-branes
generically ``curl up'' in a nontrivial RR field strength. Using this
viewpoint, we compute the decay width of the dielectric D2-branes by
constructing relevant Euclidean bounce solutions in the shape of a funnel. We
also give new solutions in doughnut shape which are involved with nucleation of
dielectric branes from nothing.Comment: 46 pages, 17 eps figures, references added, typos correcte