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

Proton number fluctuation as a signal of the QCD critical end-point

We argue that the event-by-event fluctuation of the proton number is a meaningful and promising observable for the purpose of detecting the QCD critical end-point in heavy-ion collision experiments. The long range fluctuation of the order parameter induces a characteristic correlation between protons which can be measured. The proton fluctuation also manifests itself as anomalous enhancement of charge fluctuations near the end-point, which might be already seen in existing data.Comment: 4 pages, version accepted in PR

A Theory of Optimum Tariff Under Revenue Constraint.

This paper analyzes the revenue-constrained optimum tariff problem. When a fixed level of tax revenue has to be collected only from tariffs, an efficient resource allocation can not be achieved by any tariff structure. Thus we need to find the optimum tariff structure as the second best resource allocation.TAXATION ; TRADE ; ECONOMIC THEORY

Sub-threshold J/ψ and ϒ production in γA collisions

We study sub-threshold heavy quarkonium (J/ψ and ϒ) photo-productions in γA collisions as an independent test of the universality of the nucleon-nucleon short range correlation (SRC) in nuclear scattering processes. Just below the γp threshold, the cross section is dominated by the mean field contribution of nucleons inside the nucleus. The SRC contributions start to dominate at lower photon energies, depending on the fraction of the SRC pairs in the target nucleus. We give an estimate of the cross sections in the sub-threshold region both for J/ψ and ϒ. This may be helpful for future measurements at JLab as well as at the Electron-Ion Collider in the U.S., and especially in China

QCD resummation in hard diffractive dijet production at the electron-ion collider

Diffractive dijet production at the electron-ion collider (EIC) has been proposed to study the gluon Wigner distribution at small-x. We investigate the soft gluon radiation associated with the final state jets and an all order resummation formula is derived. We show that the soft gluon resummation plays an important role to describe E791 data on π-induced diffractive dijet production at Fermilab. Predictions for the EIC are presented, and we emphasize that the soft gluon resummation is an important aspect to explore the nucleon/nucleus tomography through these processes

Jet evolution from weak to strong coupling

Recent studies, using the AdS/CFT correspondence, of the radiation produced by a decaying system or by an accelerated charge in the N=4 supersymmetric Yang-Mills theory, led to a striking result: the 'supergravity backreaction', which is supposed to describe the energy density at infinitely strong coupling, yields exactly the same result as at zero coupling, that is, it shows no trace of quantum broadening. We argue that this is not a real property of the radiation at strong coupling, but an artifact of the backreaction calculation, which is unable to faithfully capture the space-time distribution of the radiation. This becomes obvious in the case of a decaying system ('virtual photon'), for which the backreaction is tantamount to computing a three-point function in the conformal gauge theory, which is independent of the coupling since protected by symmetries. Whereas this non-renormalization property is specific to the conformal N=4 SYM theory, we argue that the failure of the three-point function to provide a local measurement is in fact generic: it holds in any field theory with non-trivial interactions. To properly study a localized distribution, one should rather compute a four-point function, as standard in deep inelastic scattering. We substantiate these considerations with studies of the radiation produced by the decay of a time-like photon at both weak and strong coupling. We show that by computing four-point functions, in perturbation theory at weak coupling and, respectively, from Witten diagrams at strong coupling, one can follow the quantum evolution and thus demonstrate the broadening of the energy distribution. This broadening is slow when the coupling is weak but it proceeds as fast as possible in the limit of a strong coupling.Comment: 49 pages, 6 figure

Radiation by a heavy quark in N=4 SYM at strong coupling

Using the AdS/CFT correspondence in the supergravity approximation, we compute the energy density radiated by a heavy quark undergoing some arbitrary motion in the vacuum of the strongly coupled N=4 supersymmetric Yang-Mills theory. We find that this energy is fully generated via backreaction from the near-boundary endpoint of the dual string attached to the heavy quark. Because of that, the energy distribution shows the same space-time localization as the classical radiation that would be produced by the heavy quark at weak coupling. We believe that this and some other unnatural features of our result (like its anisotropy and the presence of regions with negative energy density) are artifacts of the supergravity approximation, which will be corrected after including string fluctuations. For the case where the quark trajectory is bounded, we also compute the radiated power, by integrating the energy density over the surface of a sphere at infinity. For sufficiently large times, we find agreement with a previous calculation by Mikhailov [hep-th/0305196].Comment: 22 page