Relation between the chiral and deconfinement phase transitions

Lattice QCD simulations at finite temperature have shown that the chiral phase transition in the chiral limit and the deconfinement phase transition in the quenched limit are continuously connected. I emphasize the nontriviality of this result and propose an unconventional scenario which naturally explains the existing lattice data. The continuity of the two phase transitions is a manifestation of the familiar glueball-meson mixing, which can be traced back to the properties of QCD at zero temperature.Comment: 5 pages, talk given at Strong and Electroweak Matter 2004 (SEWM04), Helsinki, Finland, 16-19 Jun 200

"A Theory of Commodity Tax Reform under Revenue Constraint"

Despite the development of the optimal taxation theory , few of the practicing tax economists question the traditional wisdom that making tax rates flat will lead to a more efficient tax system. Practicing tax economists seem to have an intuition that even if the uniform tax structure may not be the most efficient, it may be a close approximation. The present paper survey the literature that provides theoretical under-pinnings for the practitioner's intuition. Also, the paper simplifies the statements and proofs of theorems in literature.

Deep Inelastic Scattering in Holographic AdS/QCD Models

We review the description of deep inelastic scattering using some AdS/QCD phenomenological models.Comment: Talk presented by NRFB at Light Cone 2009: Relativistic Hadronic and Particle Physics, 8-13 Jul 2009, Sao Jose dos Campos, Brazi

Jet fragmentation and gauge/string duality

We consider an analog of e^+e^- annihilation in gauge theories which have a dual string description in asymptotically AdS_5 space and discuss the nature of jet fragmentation. We construct the timelike anomalous dimension which governs the scale dependence of the fragmentation function. In the limit of infinite 't Hooft coupling, the average multiplicity rises linearly with the energy and the inclusive spectrum is peaked at the kinematical boundary.Comment: 9 pages, v2:comments and references adde

On the small-xx behavior of the orbital angular momentum distributions in QCD

We present the numerical solution of the leading order QCD evolution equation for the orbital angular momentum distributions of quarks and gluons and discuss its implications for the nucleon spin sum rule. We observe that at small-$x$, the gluon helicity and orbital angular momentum distributions are roughly of the same magnitude but with opposite signs, indicating a significant cancellation between them. A similar cancellation occurs also in the quark sector. We explain analytically the reason for this cancellation.Comment: 12 pages. v2: two figures added, version to appear in Physics Letters

Soft photon anomaly and gauge/string duality

Motivated by the recent DELPHI report on the anomalous photon production in e^+e^- annihilation, we exactly calculate the inclusive cross section of soft photons in the strong coupling limit of N=4 super Yang-Mills. We find that the energy distribution is that of the Bremsstrahlung, while the angular distribution is spherical. Our result elucidates a new non-perturbative source of soft photons not associated with the final state hadronic Bremsstrahlung.Comment: 22 page