24 research outputs found
Semiclassical String Solutions on 1/2 BPS Geometries
We study semiclassical string solutions on the 1/2 BPS geometry of type IIB
string theory characterized by concentric rings on the boundary plane. We
consider both folded rotating strings carrying nonzero R-charge and circular
pulsating strings. We find that unlike rotating strings, as far as circular
pulsating strings are concerned, the dynamics remains qualitatively unchanged
when the concentric rings replace AdS_5\times S^5. Using the gravity dual we
have also studied the Wilson loop of the corresponding gauge theory. The result
is qualitatively the same as that in AdS_5\times S^5 in the global coordinates
where the corresponding gauge theory is defined on S^3\times R. We show that
there is a correction to 1/L leading order behavior of the potential between
external objects.Comment: 17 pages, latex file, v2: refs. adde
Quasi-Normal Modes of Extremal BTZ Black Holes in TMG
We study the spectrum of tensor perturbations on extremal BTZ black holes in
topologically massive gravity for arbitrary values of the coefficient of the
Chern-Simons term, . Imposing proper boundary conditions at the boundary
of the space and at the horizon, we find that the spectrum contains
quasi-normal modes.Comment: 18 pages, Latex, Ref's added, Typos correcte
On Isolated Conformal Fixed Points and Noncritical String Theory
We search for the gravity description of unidentified field theories at their
conformal fixed points by studying the low energy effective action of six
dimensional noncritical string theory. We find constant dilaton solutions by
solving both the equations of motion and BPS equations. Our solutions include a
free parameter provided by a stack of uncharged space filling branes. We find
several AdS_p\times S^q solutions with constant radii for AdS_p and S^q. The
curvature of the solutions are of the order of the string scale.Comment: 17 pages, Latex fil
Circular Semiclassical String solutions on Confining AdS/CFT Backgrounds
We study multiwrapped circular string pulsating in the radial direction of
AdS black hole. We compute the energy of this string as a function of a large
quantum number n. One then could associate it with energy and a quantum number
of states in the dual finite temperature {\cal N}=4 SYM theory as well as three
dimensional pure gauge theory. We observe that the n dependence of the energy
has a universal form. We have also considered pulsating string in the
background of the near-extremal D4-brane solution. Circular pulsating membrane
in M-theory on AdS_7\times S^4 has also been studied.Comment: 14 pages, latex, v2: typos corrected, refs. adde
2D Gravity on with Chern-Simons Corrections
We study 2D Maxwell-dilaton gravity with higher order corrections given by
the Chern-Simons term. The model admits three distinctive vacuum
solutions. By making use of the entropy function formalism we find the entropy
of the solutions which is corrected due to the presence of the Chern-Simons
term. We observe that the form of the correction depends not only on the
coefficient of the Chern-Simons term, but also on the sign of the electric
charge; pointing toward the chiral nature of the dual CFT. Using the asymptotic
symmetry of the theory as well as requiring a consistent picture we can find
the central charge and the level of U(1) current. Upon uplifting the solutions
to three dimensions we get purely geometric solutions which will be either
or warped with an identification.Comment: 15 pages; V2: refs adde
Dual Spikes; New Spiky String Solutions
We find a new class of spiky solutions for closed strings in flat,
and backgrounds. In the flat
case the new solutions turn out to be T-dual configurations of spiky strings
found by Kruczenski hep-th/0410226. In the case of solutions living in ,
we make a semi classical analysis by taking the large angular momentum limit.
The anomalous dimension for these dual spikes is similar to that for rotating
and pulsating circular strings in AdS with angular momentum playing the role of
the level number. This replaces the well known logarithmic dependence for
spinning strings. For the dual spikes living on sphere we find that no large
angular momentum limit exists.Comment: Added reference
On Effective Superpotentials and Compactification to Three Dimensions
We study four dimensional N=2 SO/SP supersymmetric gauge theory on R^3\times
S^1 deformed by a tree level superpotential. We will show that the exact
superpotential can be obtained by making use of the Lax matrix of the
corresponding integrable model which is the periodic Toda lattice. The
connection between vacua of SO(2N) and SO(2kN-2k+2) can also be seen in this
framework. Similar analysis can also be applied for SO(2N+1) and SP(2N).Comment: 18 pages, latex file, v2: typos corrected, refs adde
Semiclassical String Solutions on deformed NS5-brane Backgrounds and New Plane wave
We study different Penrose limits of supergravity solution of NS5-brane in
the presence of RR field. Although in the case of NS5-brane we get a
4-dimensional plane wave, in the case with RR field we will get two different
plane waves; a 4-dimensional and a 3-dimensional one. These plane wave
solutions are the backgrounds that a particular string solution feels at one
loop approximation. Using the one loop correction one can identify a particular
subsector of LST/deformed LST which is dual to type II string theories on these
plane waves.Comment: 18 pages, latex, v2: Minor changes, typos correcte
Multi-spin string solutions in AdS Black Hole and confining backgrounds
We study semi-classical multi-spin strings in the non-supersymmetric
backgrounds of Black Hole and Witten's confining model. We consider
constant radius strings with rotations along the isometries of the backgrounds.
In the Black Hole, solutions exist only if there is a non-zero spin in
the Black Hole part. In contrast with the background, we find solutions
which although have no rotation in the part, have a regular
expansion in the expression for large energy. In the near-extremal and
backgrounds, we find that strings have to be located on the confining
wall. We also discuss the stability of solutions by considering the fluctuation
Lagrangians.Comment: 26 pages, LaTeX, references adde