Supersymmetry breaking at the end of a cascade of Seiberg dualities

We study the IR dynamics of the cascading non-conformal quiver theory on N regular and M fractional D3 branes at the tip of the complex cone over the first del Pezzo surface. The horizon of this cone is the irregular Sasaki-Einstein manifold Y^{2,1}. Our analysis shows that at the end of the cascade supersymmetry is dynamically broken.Comment: 12 pages, 2 figures, minor changes, typos correcte

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

Hydrodynamics of fundamental matter

First and second order transport coefficients are calculated for the strongly coupled N=4 SYM plasma coupled to massless fundamental matter in the Veneziano limit. The results, including among others the value of the bulk viscosity and some relaxation times, are presented at next-to-leading order in the flavor contribution. The bulk viscosity is found to saturate Buchel's bound. This result is also captured by an effective single-scalar five-dimensional holographic dual in the Chamblin-Reall class and it is suggested to hold, in the limit of small deformations, for generic plasmas with gravity duals, whenever the leading conformality breaking effects are driven by marginally (ir)relevant operators. This proposal is then extended to other relations for hydrodynamic coefficients, which are conjectured to be universal for every non-conformal plasma with a dual Chamblin-Reall-like description. Our analysis extends to any strongly coupled gauge theory describing the low energy dynamics of Nc>>1 D3-branes at the tip of a generic Calabi-Yau cone. The fundamental fields are added by means of 1<<Nf<<Nc homogeneously smeared D7-branes.Comment: 24 pages. V2: Important improvements in the discussion of the results in section 1. References adde

On the geometry of string duals with backreacting flavors

Making use of generalized calibrated geometry and G-structures we put the problem of finding string-duals with smeared backreacting flavor branes in a more mathematical setting. This more formal treatment of the problem allows us to easily smear branes without good coordinate representations, establish constraints on the smearing form and identify a topological central charge in the SUSY algebra. After exhibiting our methods for a series of well known examples, we apply them to the problem of flavoring a supergravity-dual to a d=2+1 dimensional N=2 super Yang-Mills-like theory. We find new solutions to both the flavored and unflavored systems. Interpretating these turns out to be difficult.Comment: 38 pages - Typos corrected and references added - As published in JHE

Holographic Duals of Quark Gluon Plasmas with Unquenched Flavors

We review the construction of gravitational solutions holographically dual to N=1 quiver gauge theories with dynamical flavor multiplets. We focus on the D3-D7 construction and consider the finite temperature, finite quark chemical potential case where there is a charged black hole in the dual solution. Discussed physical outputs of the model include its thermodynamics (with susceptibilities) and general hydrodynamic properties.Comment: Lecture presented at the Workshop "AdS/CFT and Novel Approaches to Hadron and Heavy Ion Physics", Kavli Institute of Theoretical Physics (KITPC), Beijing, China, 13 October 2010. Review article to be published in Communications in Theoretical Physics. 27 pages, 2 figure

An elementary stringy estimate of transport coefficients of large temperature QCD

Modeling QCD at large temperature with a simple holographic five dimensional theory encoding minimal breaking of conformality, allows for the calculation of all the transport coefficients, up to second order, in terms of a single parameter. In particular, the shear and bulk relaxation times are provided. The result follows by deforming the AdS background with a scalar dual to a marginally relevant operator, at leading order in the deformation parameter.Comment: 11 pages; v2: comments and references adde

Spinning Particles on Spacelike Hypersurfaces and their Rest-Frame Description

A new spinning particle with a definite sign of the energy is defined on spacelike hypersurfaces after a critical discussion of the standard spinning particles. They are the pseudoclassical basis of the positive energy $({1\over 2},0)$ [or negative energy $(0,{1\over 2})$] parts of the $({1\over 2},{1\over 2})$ solutions of the Dirac equation. The study of the isolated system of N such spinning charged particles plus the electromagnetic field leads to their description in the rest-frame Wigner-covariant instant form of dynamics on the Wigner hyperplanes orthogonal to the total 4-momentum of the isolated system (when it is timelike). We find that on such hyperplanes these spinning particles have a nonminimal coupling only of the type "spin-magnetic field" like the nonrelativistic Pauli particles to which they tend in the nonrelativistic limit. The Lienard-Wiechert potentials associated with these charged spinning particles are found. Then, a comment on how to quantize the spinning particles respecting their fibered structure describing the spin structure is done.Comment: 70 pages, revte

On unquenched N=2 holographic flavor

The addition of fundamental degrees of freedom to a theory which is dual (at low energies) to N=2 SYM in 1+3 dimensions is studied. The gauge theory lives on a stack of Nc D5 branes wrapping an S^2 with the appropriate twist, while the fundamental hypermultiplets are introduced by adding a different set of Nf D5-branes. In a simple case, a system of first order equations taking into account the backreaction of the flavor branes is derived (Nf/Nc is kept of order 1). From it, the modification of the holomorphic coupling is computed explicitly. Mesonic excitations are also discussed.Comment: 25 pages, 4 figure