102 research outputs found
New Examples of Flux Vacua
Type IIB toroidal orientifolds are among the earliest examples of flux vacua.
By applying T-duality, we construct the first examples of massive IIA flux
vacua with Minkowski space-times, along with new examples of type IIA flux
vacua. The backgrounds are surprisingly simple with no four-form flux at all.
They serve as illustrations of the ingredients needed to build type IIA and
massive IIA solutions with scale separation. To check that these backgrounds
are actually solutions, we formulate the complete set of type II supergravity
equations of motion in a very useful form that treats the R-R fields
democratically.Comment: 38 pages, LaTeX; references updated; additional minor comments added;
published versio
On RR couplings on D-branes at order
Recently, it has been found that there are couplings of the RR field strength
and the B-field strength on the world volume of D-branes at
order . These couplings which have both world-volume and
transverse indices, are invariant under the linear T-duality transformations.
Consistency with the nonlinear T-duality indicates that the RR field strength
in these couplings should be replaced by where . This replacement, however, reproduces some
non-gauge invariant terms. On the other hand, the nonlinear terms are invariant
under the linear T-duality transformations at the level of two B-fields. This
allows one to remove some of the nonlinear terms in . We fix
this by comparing the nonlinear couplings with the S-matrix element of one RR
and two NSNS vertex operators. Our results indicate that in the expansion of
one should keep only the B-field gauge invariant terms, e.g.
where both indices of B-field lie along the brane.
Moreover, in this case one should replace with to have the
-field gauge invariance.Comment: 23 pages, Latex file, 1 figure; v2:typos corrected, to appear in JHE
On effective actions of BPS branes and their higher derivative corrections
We calculate in detail the disk level S-matrix element of one Ramond-Ramond
field and three gauge field vertex operators in the world volume of BPS branes,
to find four gauge field couplings to all orders of up to on-shell
ambiguity. Then using these infinite couplings we find that the massless pole
of the field theory amplitude is exactly equal to the massless pole S-matrix
element of this amplitude for the case to all orders of .
Finally we show that the infinite massless poles and the contact terms of this
amplitude for the case can be reproduced by the Born-Infeld action and
the Wess-Zumino actions and by their higher derivative corrections.Comment: 26 pages, 2 figures, minor corrections,references added and version
published in JHE
Intersecting D4-branes Model of Holographic QCD and Tachyon Condensation
We consider the intersecting D4-brane and anti-D4-brane model of holographic
QCD, motivated by the model that has recently been suggested by Van Raamsdonk
and Whyte. We analyze such D4-branes by the use of the action with a
bi-fundamental ``tachyon'' field, so that we find the classical solutions
describing the intersecting D4-branes and the U-shaped D4-branes. We show that
the ``tachyon'' field in the bulk theory provides a current quark mass and a
quark condensate to the dual gauge theory and that the lowest modes of mesons
obtain mass via tachyon condensation. Then evaluating the properties of a pion,
one can reproduce Gell-Mann-Oakes-Renner relation.Comment: 24 pages, 5 figures; v2: refs. added; v3: discussions on Chern-Simons
terms are adde
The group structure of non-Abelian NS-NS transformations
We study the transformations of the worldvolume fields of a system of
multiple coinciding D-branes under gauge transformations of the supergravity
Kalb-Ramond field. We find that the pure gauge part of these NS-NS
transformations can be written as a U(N) symmetry of the underlying Yang-Mills
group, but that in general the full NS-NS variations get mixed up non-trivially
with the U(N). We compute the commutation relations and the Jacobi identities
of the bigger group formed by the NS-NS and U(N) transformations.Comment: Latex, 11 pages. v2: Typos corrected; version to appear in JHEP
M-theory and Type IIA Flux Compactifications
We consider compactifications of M-theory and type IIA string theory to four
dimensions. For Minkowski space-time, a supergravity no-go theorem forbids flux
supported in the internal space. We show how to evade this no-go theorem by
exhibiting new sources of brane charge: in string theory, the basic physical
phenomenon is the generation of new brane charges from D-branes in transverse
fluxes. In M-theory, there is a new source of M5-brane charge from novel higher
derivative couplings that involve fluxes as well as curvatures. We present some
explicit orientifold examples with both N=1 and N=2 space-time supersymmetry.
Finally, we explain the status of massive type IIA flux compactifications.Comment: 36 pages, LaTeX; references adde
Comments on regularization of identity based solutions in string field theory
We analyze the consistency of the recently proposed regularization of an
identity based solution in open bosonic string field theory. We show that the
equation of motion is satisfied when it is contracted with the regularized
solution itself. Additionally, we propose a similar regularization of an
identity based solution in the modified cubic superstring field theory.Comment: 24 pages, two subsections added, two references adde
Non Abelian Geometrical Tachyon
We investigate the dynamics of a pair of coincident D5 branes in the
background of NS5 branes. It has been proposed by Kutasov that the system
with a single probing D-brane moving radially in this background is dual to the
tachyonic DBI action for a non-BPS Dp brane. We extend this proposal to the
non-abelian case and find that the duality still holds provided one promotes
the radial direction to a matrix valued field associated with a non-abelian
geometric tachyon and a particular parametrization for the transverse scalar
fields is chosen. The equations of motion of a pair of coincident D5 branes
moving in the NS5 background are determined. Analytic and numerical solutions
for the pair are found in certain simplified cases in which the U(2) symmetry
is broken to corresponding to a small transverse separation
of the pair. For certain range of parameters these solutions describe periodic
motion of the centre of mass of the pair 'bouncing off' a finite sized throat
whose minimum size is limited by the D5 branes separation.Comment: 18 pages, 2 figures, PdfLatex: references added.accepted for
publication in JHE
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