189 research outputs found
Fundamental vs. Solitonic Description of D3 branes
Type IIB string theory expanded around D3 brane backgrounds describes the
dynamics of D3 branes as solitonic objects. On the other hand, there is a
fundamental description of them via Polchinski's open strings with Dirichlet
boundary conditions. Since these two descriptions describe the dynamics of the
same objects, D3 branes, it is natural to believe that they are dual. Therefore
at this level, we have a string-string duality as opposed to a string-field
theory duality. Once we take the same limits in both descriptions, Maldacena
Conjecture in its weaker form follows. We try to make this viewpoint precise
and study the implication of it for the stronger form of Maldacena Conjecture.Comment: 11 pages, 3 figures, typos correcte
Dynamics of false vacuum bubbles in Brans-Dicke theory
We study the dynamics of false vacuum bubbles in the Brans-Dicke theory of
gravity by using the thin shell or thin wall approximation. We consider a false
vacuum bubble that has a different value for the Brans-Dicke field between the
inside false vacuum region and the outside true vacuum region. Within a certain
limit of field values, the difference of field values makes the effective
tension of the shell negative. This allows new expanding false vacuum bubbles
to be seen by the outside observer, which are disallowed in Einstein gravity.Comment: 29 pages, 20 figure
Scalar Hair of Global Defect and Black Brane World
We consider a complex scalar field in (p+3)-dimensional bulk with a negative
cosmological constant and study global vortices in two extra-dimensions. We
reexamine carefully the coupled scalar and Einstein equations, and show that
the boundary value of scalar amplitude at infinity of the extra-dimensions
should be smaller than vacuum expectation value. The brane world has a
cigar-like geometry with an exponentially decaying warp factor and a flat thick
p-brane is embedded. Since a coordinate transformation identifies the obtained
brane world as a black p-brane world bounded by a horizon, this strange
boundary condition of the scalar amplitude is understood as existence of a
short scalar hair.Comment: 26 pages, 2 figure
entropy of M5 branes from dielectric effect
We observe that the entropy behavior of near-extermal M5 branes can be
reproduced from SYM side with the role of Myers' terms. We start by
generalizing the Klebanov-Tseytlin (KT) supergravity solution that displays the
entropy behavior. The new feature of the general solution is visibility
of the "internal" degrees of the M5 branes, i.e., the M0 branes and the M2
branes. With the rationale provided by the supergravity analysis, we consider a
D0 brane quantum mechanical setup with Myers' terms. Using localization
technique, we show that the leading behavior of the free energy comes
from the "classical contribution" with the rest sub-leading.Comment: latex, 21 pages, missing figure adde
Super Yang-Mills Operators from the D3-brane Action in a Curved Background
A consistent truncation of IIB on S^5 has been obtained in the sector of the
metric and the 4-form potential. The ansatz contains 20 scalars and all 15
gauge fields of gauged supergravity in five dimensions. With this
fully non-linear ansatz, the calculations for n-point correlators of super
Yang-Mills (SYM) theory via AdS/CFT are simpler than those in the literature
that use {\em linear} ansatz followed by non-linear field redefinitions. We
work out the SYM operators that couple to the scalars by expanding the
Dirac-Born-Infeld (DBI) action plus Wess-Zumino (WZ) terms around an
AdS_5\timesS^5 background with the metric fluctuations. The resulting
operators agree with those based on a superconformal symmetry argument. We
discuss the significance of our results.Comment: one author's name correcte
Moduli Space of Unstable D-branes on a Circle of Critical Radius
We study the moduli space of the boundary conformal field theories describing
an unstable D-brane of type II string theory compactified on a circle of
critical radius. This moduli space has two branches, -- a three dimensional
branch S^3/Z_2 and a two dimensional branch described by a square torus T^2.
These two branches are joined along a circle. We compare this with the moduli
space of classical solutions of tachyon effective field theory compactified on
a circle of critical radius. This moduli space has a very similar structure to
that of the boundary conformal field theory with the only difference that the
S^3 of the S^3/Z_2 component becomes a deformed S^3. This provides one more
indication that the tachyon effective field theory captures qualitatively the
dynamics of the tachyon on an unstable D-brane.Comment: LaTeX file, 24 pages, 2 figures; v2: reference to earlier work adde
OXA-carbapenemases present in clinical acinetobacter baumannii-calcoaceticus complex isolates from patients in kurdistan region, Iraq
In addition to intrinsic resistance in Acinetobacter baumannii, many different types of acquired resistance mechanisms have been reported, including the presence of VIM and IMP metallo β-lactamases and also of blaOXA-23-like and blaOXA-58-like enzymes. In the Kurdistan region of Iraq, the multiresistant A. baumannii-calcoaceticus complex is prevalent. We characterized the different mechanisms of resistance present in clinical isolates collected from different wards and different hospitals from the Kurdistan region. One hundred twenty clinical nonduplicate A. baumannii-calcoaceticus complex isolates were collected from four hospitals between January 2012 and October 2013. The identification of the isolates was confirmed by MALDI-TOF.
The sus
S-matrix elements and off-shell tachyon action with non-abelian gauge symmetry
We propose that there is a unique expansion for the string theory S-matrix
elements of tachyons that corresponds to non-abelian tachyon action. For those
S-matrix elements which, in their expansion, there are the Feynman amplitudes
resulting from the non-abelian kinetic term, we give a prescription on how to
find the expansion. The gauge invariant action is an expanded action,
and the tachyon mass which appears as coefficient of many different
couplings, is arbitrary. We then analyze in details the S-matrix element of
four tachyons and the S-matrix element of two tachyons and two gauge fields, in
both bosonic and superstring theories, in favor of this proposal. In the
superstring theory, the leading terms of the non-abelian gauge invariant
couplings are in agreement with the symmetrised trace of the direct non-abelian
generalization of the tachyonic Born-Infeld action in which the tachyon
potential is consistent with . In the bosonic
theory, on the other hand, the leading terms are those appear in superstring
case as well as some other gauge invariant couplings which spoils the
symmetrised trace prescription. These latter terms are zero in the abelian
case.Comment: Latex, 27 pages, no figures,v4:change the introduction section, add
some notes to clarify the idea, add reference
Proposal for the Open String Tachyon Effective Action in the Linear Dilaton Background
In this paper we propose tachyon effective actions for unstable D-branes in
superstring and bosonic string theories in the presence of the linear dilaton
background.Comment: 18 page
- …