Ismail Zahed

The Skyrme Model

We review the recent developments on the Skyrme model in the context of QCD, and analyze their relevance to low-energy phenomenology. The fundamentals of chiral symmetry and PCAC are presented, and their importance in effective chiral models of the Skyrme type discussed. The nature and properties of skyrmions are thoroughly investigated, with particular stress on the basic role of the Wess-Zumino term. The conventional Skyrme model is extended to the low-lying vector meson resonances, and the rudiments of vector meson dominance are elucidated. A detailed account of the static and dynamical properties of nucleons and δ-isobars is presented. The relevance of the Skyrme model to the nuclear many-body problem is outlined and its importance for boson exchange models stressed.

A Gravity Dual of RHIC Collisions

In the context of the AdS/CFT correspondence we discuss the gravity dual of a heavyion-like collision in a variant of N = 4 SYM. We provide a gravity dual picture of the entire process using a model where the scattering process creates initially a holographic shower in bulk AdS. The subsequent gravitational fall leads to a moving black hole that is gravity dual to the expanding and cooling heavy-ion fireball. The front of the fireball cools at the rate of 1/�, while

High-multiplicity pp and pA collisions: Hydrodynamics at its edge

With growing multiplicity, the pp and pA collisions enter the domain where the macroscopic description (thermodynamics and hydrodynamics) becomes applicable. We discuss this situation, first with simplified thought experiments, then with some idealized representative cases, and finally address the real data. For clarity, we do not do it numerically but analytically, using the Gubser solution. We found that the radial flow is expected to increase from central AA to central pA, while the elliptic flow decreases, with higher harmonics being comparable. We extensively study the magnitude and distribution of the viscous corrections, in Navier-Stokes and Israel-Stuart approximations, ending with higher gradient resummation proposed by Lublinsky and Shuryak. We found that those corrections grow from AA to pA to pp, but remain tractable even for pp.

Chiral effective action with heavy quark symmetry

We derive an effective action combining chiral and heavy-quark symmetry, using approximate bosonization techniques to QCD-inspired models of spontaneous symmetry breaking. We explicitly show that the heavy-quark limit is compatible with the large [ital N][sub [ital c]] (number of color) limit in the meson sector, and estimate the couplings between the light and heavy mesons ([ital D],[ital D][sup *], . . .) and their chiral partners to order one in the heavy-quark mass. The relevance of this effective action to solitons with heavy quarks is briefly discussed.

The chiral model of Sakai-Sugimoto at finite baryon density

In the context of holographic QCD we analyze Sakai-Sugimotos chiral model at finite baryon density and zero temperature. The baryon number density is introduced through compact D4 wrapping S4 at the tip of D8-. Each baryon acts as a chiral point-like source distributed uniformly over 3, and leads a non-vanishing U(1)V potential on the brane. For fixed baryon charge density nB we analyze the energy density and pressure using the canonical formalism. The baryonic matter with point like sources is always in the spontaneously broken phase of chiral symmetry, whatever the density. The point-like nature of the sources and large Nc cause the matter to be repulsive as all baryon interactions are omega mediated. Through the induced DBI action on D8-, we study the effects of the fixed baryon charge density nB on the pion and vector meson masses and couplings. Issues related to vector dominance in matter in the context of holographic QCD are also discussed.

Rethinking the properties of the quark gluon plasma at T approximately T(c)

We argue that although at asymptotically high temperatures the QGP in bulk behaves as a gas of weakly interacting quasiparticles (modulo long-range magnetism), at temperatures up to few times the critical temperature

RANDOM MATRIX THEORY AND THREE-DIMENSIONAL QCD

T_c

Plasmons from a gauge invariant effective action for hot gluons

it displays different properties. If the running of the QCD coupling constant continues in the Coulomb phase till the screening length scale, it reaches the strong coupling treshold

Instanton induced effects in QCD high-energy scattering

\alpha_s(m_D)\sim 1

Dense Holographic QCD in the Wigner-Seitz Approximation

. As a result, the Coulomb phase supports weakly bound Coulombic s-wave