39 research outputs found
D-Brane Dynamics and NS5 Rings
We consider the classical motion of a probe D-brane moving in the background
geometry of a ring of NS5 branes, assuming that the latter are non-dynamical.
We analyse the solutions to the Dirac-Born-Infield (DBI) action governing the
approximate dynamics of the system. In the near horizon (throat) approximation
we find several exact solutions for the probe brane motion. These are compared
to numerical solutions obtained in more general cases. One solution of
particular interest is when the probe undergoes oscillatory motion through the
centre of the ring (and perpendicular to it). By taking the ring radius
sufficiently large, this solution should remain stable to any stringy
corrections coming from open-strings stretching between the probe and the
NS5-branes along the ring.Comment: 17 pages, Latex, 8 figures; References adde
D-brane dynamics near compactified NS5-branes
We examine the dynamics of a -brane in the background of coincident,
parallel 5-branes which have had one of their common transverse directions
compactified. We find that for small energy, bound orbits can exist at
sufficiently large distances where there will be no stringy effects. The orbits
are dependent upon the energy density, angular momentum and electric field. The
analysis breaks down at radial distances comparable with the compactification
radius and we must resort to using a modified form of the harmonic function in
this region.Comment: Latex, 20 pages, 6 figs, references adde
On the Universal Tachyon and Geometrical Tachyon
We study properties of non-BPS D(p+1)-brane in the background of k
NS5-branes, with one transverse direction compactified on a circle, from the
point of view of Dirac-Born-Infeld action. We present the analysis of two
different embedding of non-BPS D(p+1)-brane in given background and study the
classical solutions of given world-volume theory. We argue for the
configuration of a non-BPS D(p+1)-brane which allows us to find solutions of
the equations of motion that give unified descriptions of G and U-type branes.Comment: 24 pages, minor change
The Topological Cigar Observables
We study the topologically twisted cigar, namely the SL(2,R)/U(1)
superconformal field theory at arbitrary level, and find the BRST cohomology of
the topologically twisted N=2 theory. We find a one to one correspondence
between the spectrum of the twisted coset and singular vectors in the Wakimoto
modules constructed over the SL(2,R) current algebra. The topological cigar
cohomology is the crucial ingredient in calculating the closed string spectrum
of topological strings on non-compact Gepner models.Comment: 28 page
Exactly Soluble Dynamics of (p,q) String Near Macroscopic Fundamental Strings
We study dynamics of Type IIB bound-state of a Dirichlet string and n
fundamental strings in the background of N fundamental strings. Because of
supergravity potential, the bound-state string is pulled to the background
fundamental strings, whose motion is described by open string rolling radion
field. The string coupling can be made controllably weak and, in the limit , the bound-state energy involved is small
compared to the string scale. We thus propose rolling dynamics of open string
radion in this system as an exactly solvable analog for rolling dynamics of
open string tachyon in decaying D-brane. The dynamics bears a novel feature
that the worldsheet electric field increases monotonically to the critical
value as the bound-state string falls into the background string. Close to the
background string, D string constituent inside the bound-state string decouples
from fundamental string constituents.Comment: 27p, 2 figure
On Minimal N=4 Topological Strings And The (1,k) Minimal Bosonic String
In this paper we consider tree-level scattering in the minimal N=4
topological string and show that a large class of N-point functions can be
recast in terms of corresponding amplitudes in the (1,k) minimal bosonic
string. This suggests a non-trivial relation between the minimal N=4
topological strings, the (1,k) minimal bosonic strings and their corresponding
ADE matrix models. This relation has interesting and far-reaching implications
for the topological sector of six-dimensional Little String Theories.Comment: lanlmac, 30 pages; v3 minor revisions, version published in JHE
Dynamics of D1-brane in I-brane Background
This paper is devoted to the study of the effective field theory description
of the probe D1-brane in the background of the system of two stacks of
fivebranes in type IIB theory that intersect on . We study the
properties of the Dirac-Born-Infeld action for D1-brane moving in this
background. We will argue that this action is invariant under an additional
symmetry in the near horizon limit and that this new symmetry is closely
related to the enhanced symmetry of the I-brane background considered recently
in [hep-th/0508025]. We also solve explicitly the equation of motion of
D1-brane in the near horizon limit.Comment: 21 pages, references adde
Non-BPS D-brane Near NS5-branes
We use tachyon field theory effective action to study the dynamics of a
non-BPS Dp-brane propagating in the vicinity of k NS5-branes. For the time
dependent tachyon condensation we will concentrate on the case of the large
tachyon and the case when a non-BPS D-brane is close to NS5-branes. For spatial
dependent tachyon condensation we will argue that the problem reduces to the
study of the motion of an array of D(p-1)-branes and D(p-1)-antibranes in the
vicinity of k NS5-branes.Comment: 21 page
Geometrical Tachyon Kinks and NS5 Branes
We further investigate the 5 ring background using the tachyon map.
Mapping the radion fields to the rolling tachyon helps to explain the motion of
a probe -brane in this background. It turns out that the radion field
becomes tachyonic when the brane is confined to one dimensional motion inside
the ring. We find explicit solutions for the geometrical tachyon field that
describe stable kink solutions which are similar to those of the open string
tachyon. Interestingly in the case of the geometric tachyon, the dynamics is
controlled by a cosine potential. In addition, we couple a constant electric
field to the probe-brane, but find that the only stable kink solutions occur
when there is zero electric field or a critical field value. We also
investigate the behaviour of Non-BPS branes in this background, and find that
the end state of any probe brane is that of tachyonic matter 'trapped' around
the interior of the ring. We conclude by considering compactification of the
ring solution in one of the transverse directions.Comment: Latex, 24 pages, 1 eps fig; clarifying comments added to Section 2;
typos correcte
Spinflation from Geometric Tachyon
We study the assisted inflation scenario from the rolling of BPS D3-brane
into the NS5-branes, on a transverse geometry of , coupled to
four dimensional gravity. We assume that the branes are distributed along
and the probe D3-branes spin along plane. Qualitatively this process is
similar to that of N-tachyon assisted inflation on unstable D-branes. We
further study the spinflation scenario numerically and analyze its effect.Comment: 18pages, 9 figures, added clarifications, to appear in JHE