D3-D7 Quark-Gluon Plasmas at Finite Baryon Density

We present the string dual to SU(Nc) N=4 SYM, coupled to Nf massless fundamental flavors, at finite temperature and baryon density. The solution is determined by two dimensionless parameters, both depending on the 't Hooft coupling $\lambda_h$ at the scale set by the temperature T: $\epsilon_h\sim\lambda_h Nf/Nc$, weighting the backreaction of the flavor fields and $\tilde\delta\sim\lambda_h^{-1/2}nb/(Nf T^3)$, where $nb$ is the baryon density. For small values of these two parameters the solution is given analytically up to second order. We study the thermodynamics of the system in the canonical and grand-canonical ensembles. We then analyze the energy loss of partons moving through the plasma, computing the jet quenching parameter and studying its dependence on the baryon density. Finally, we analyze certain "optical" properties of the plasma. The whole setup is generalized to non abelian strongly coupled plasmas engineered on D3-D7 systems with D3-branes placed at the tip of a generic singular Calabi-Yau cone. In all the cases, fundamental matter fields are introduced by means of homogeneously smeared D7-branes and the flavor symmetry group is thus a product of abelian factors.Comment: 27 pages; v2: 29 pages, 1 (new) figure, new section 4.4 on optical properties, references, comments added; v3: eq. (3.19), comments and a reference adde

Towards multi-scale dynamics on the baryonic branch of Klebanov-Strassler

We construct explicitly a new class of backgrounds in type-IIB supergravity which generalize the baryonic branch of Klebanov-Strassler. We apply a solution-generating technique that, starting from a large class of solutions of the wrapped-D5 system, yields the new solutions, and then proceed to study in detail their properties, both in the IR and in the UV. We propose a simple intuitive field theory interpretation of the rotation procedure and of the meaning of our new solutions within the Papadopoulos-Tseytlin ansatz, in particular in relation to the duality cascade in the Klebanov-Strassler solution. The presence in the field theory of different VEVs for operators of dimensions 2, 3 and 6 suggests that this is an important step towards the construction of the string dual of a genuinely multi-scale (strongly coupled) dynamical model.Comment: 37 pages, 7 figures. References added, version to appear in JHE

Glueball Spectra of SQCD-like Theories

We study the spectrum of scalar glueballs in SQCD-like theories whose gravity description is in terms of Nc D5 color branes wrapped on an S^2 inside a CY3-fold, and Nf backreacting D5 flavor branes wrapped on a non-compact two-cycle inside the same CY3-fold. We show that there exists a consistent truncation of the ten-dimensional Type IIB supergravity system to a five-dimensional non-linear sigma model consisting of four scalars coupled to gravity. Studying fluctuations of the scalars as well as the metric around particular backgrounds allows us to compute their spectra. A few different backgrounds share the same qualitative features, namely that the mass of the lightest scalar glueball increases as the number of flavors is increased, until one reaches the point Nf = 2 Nc after which the opposite behaviour is obtained. We show that the five-dimensional non-linear sigma model obeys Seiberg duality, and demonstrate this explicitly for the spectra of a class of backgrounds that are Seiberg dual to themselves.Comment: 34 pages, 7 figures. Discussion of field theory added. Version to be published in JHEP