8,096 research outputs found
The D3/D7 Background and Flavor Dependence of Regge Trajectories
In the context of AdS/CFT with flavor, we consider the type IIB supergravity
solution corresponding to a fully localized D3/D7 intersection. We complete the
standard metric ansatz by providing an analytic expression for the warp factor,
under the assumption of a logarithmically running axion-dilaton. From the gauge
dual perspective, this behavior is related to the positive beta function of the
N=4, d=4 SU(N_c) super Yang-Mills gauge theory, coupled to N_f fundamental N=2
hypermultiplets. We comment on the existence of tadpoles and relate them to the
same gauge theory beta function. Next we consider a classical spinning string
configuration in the decoupling limit of the D3/D7 geometry and extract the
flavor (N_f) dependence of the associated meson Regge trajectory. Including the
backreaction of the D7-branes in the supergravity dual allows for going beyond
the quenched approximation on the dual gauge theory side.Comment: 26 pages, 5 figure
Flavoring the gravity dual of N=1 Yang-Mills with probes
We study two related problems in the context of a supergravity dual to N=1
SYM. One of the problems is finding kappa symmetric D5-brane probes in this
particular background. The other is the use of these probes to add flavors to
the gauge theory. We find a rich and mathematically appealing structure of the
supersymmetric embeddings of a D5-brane probe in this background. Besides, we
compute the mass spectrum of the low energy excitations of N=1 SQCD (mesons)
and match our results with some field theory aspects known from the study of
supersymmetric gauge theories with a small number of flavors.Comment: 55 pages, 7 figures, LaTeX; v2: typos corrected, references added;
v3: typos correcte
N=2 Coset Compactifications with Non-Diagonal Invariants
We consider 4-dimensional string models obtained by tensoring N=2 coset
theories with non-diagonal modular invariants. We present results from a
systematic analysis including moddings by discrete symmetries.Comment: 29 page
On Non-Abelian T-Duality and new N=1 backgrounds
We study the action of non-Abelian T-duality in the context of N=1 geometries
with well understood field theory duals. In the conformal case this gives rise
to a new solution that contains an AdS_5 X S^2 piece. In the case of
non-conformal geometries we obtain a new background in massive IIA supergravity
that presents similar behaviour to the cascade of Seiberg dualities. Some
physical observables are discussed.Comment: 13 pages, Latex. Version to appear in Physics Letters B (v2
Black hole - D-brane correspondence: An example
We explore the connection between D-branes and black holes in one particular
case: a -brane compactified to four dimensions on . Using the
-brane boundary state description we show the equivalence with a double
extremal N=2 black hole solution of four dimensional supergravity.Comment: 15 pages, LaTeX. Contribution by C. Nunez to the conference Quantum
Gravity in the Southern Cone, Bariloche 7-10 January 1998; to appear in the
proceeding
A new eclipsing binary system with a pulsating component detected by CoRoT
We report the discovery of CoRoT 102980178 (R.A.= 06:50:12.10, Dec.=
-02:41:21.8, J2000) an Algol-type eclipsing binary system with a pulsating
component (oEA). It was identified using a publicly available 55 day long
monochromatic lightcurve from the CoRoT initial run dataset (exoplanet field).
Eleven consecutive 1.26m deep total primary and the equal number of 0.25m deep
secondary eclipses (at phase 0.50) were observed. The following light elements
for the primary eclipse were derived: HJD_MinI= 2454139.0680 + 5.0548d x E. The
lightcurve modeling leads to a semidetached configuration with the photometric
mass ratio q=0.2 and orbital inclination i=85 deg. The out-of-eclipse
lightcurve shows ellipsoidal variability and positive O'Connell effect as well
as clear 0.01m pulsations with the dominating frequency of 2.75 c/d. The
pulsations disappear during the primary eclipses, which indicates the primary
(more massive) component to be the pulsating star. Careful frequency analysis
reveals the second independent pulsation frequency of 0.21 c/d and numerous
combinations of these frequencies with the binary orbital frequency and its
harmonics. On the basis of the CoRoT lightcurve and ground based multicolor
photometry, we favor classification of the pulsating component as a gamma
Doradus type variable, however, classification as an SPB star cannot be
excluded.Comment: 16 pages, 7 figures, 3 tables, accepted to Communications in
Asteroseismolog
Dynamic transition to spontaneous scalarization in boson stars
We show that the phenomenon of spontaneous scalarization predicted in neutron
stars within the framework of scalar-tensor tensor theories of gravity, also
takes place in boson stars without including a self-interaction term for the
boson field (other than the mass term), contrary to what was claimed before.
The analysis is performed in the physical (Jordan) frame and is based on a 3+1
decomposition of spacetime assuming spherical symmetry.Comment: Minor changes to match the final version to appear in PR
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