Electromagnetic and Axial Current Form Factors and Spectroscopy of Three-Flavor Holographic Baryons

We present an analysis of the three-flavor holographic model of QCD associated to a $D4/D8$ brane configuration, with symmetry breaking induced by a worldsheet instanton associated to a closed loop connecting $D4-D8-D6-\overline{D8}$. We calculate the electromagnetic and axial couplings of all octet and decuplet baryons, as well as several negative parity excitations, with and without symmetry breaking effects, and demonstrate qualitative and quantitative agreement with many available experimental measurements, with marked improvement over the analogous two-flavor models.Comment: 23 page

Nonabelian Berry Phases in Baryons

We show how generic nonabelian gauge fields can be induced in baryons when a hierarchy of fast degrees of freedom is integrated out. We identify them with nonabelian Berry potentials and discuss their role in transmuting quantum numbers in bag and soliton models of baryons. The resulting baryonic spectra for both light and heavy quark systems are generic and resemble closely the excitation spectrum of diatomic molecules. The symmetry restoration in the system, i.e., the electronic rotational invariance in diatomic molecules, the heavy-quark symmetry in heavy baryons etc. is interpreted in terms of the vanishing of nonabelian Berry potentials that otherwise govern the hyperfine splitting.Comment: Latex 35 pages (2 figures not added, will be faxed if requested), NTG-92-2

H-dibaryon matter in the Skyrme model on a hypersphere

We study the properties of H-dibaryon matter through the SO(3) Skyrmion solution on a three-dimensional hypersphere $S^3$. As the density increases, the swelling of H-dibaryon is found. Above a critical density, the system becomes uniform in terms of the baryon density. In this uniform phase, the critical order parameter is largely reduced, which can be interpreted as the chiral symmetry restoration. From the comparison with the $SO(2) \times SO(2)$ solution, the SO(3) soliton is found to be the true ground state for high density system with $R \leq 0.64$ fm in the B=2 sector with $N_f=3$.Comment: 10 pages LaTeX, 7 epsf figures, epsf.sty, to be published in Physics Letters B Comparison with SO(2)xSO(2) configuration is adde

Rethinking the Properties of the Quark-Gluon Plasma at T∼TcT\sim 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 $T_c$ 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 $\alpha_s(m_D)\sim 1$. As a result, the Coulomb phase supports weakly bound Coulombic s-wave $\bar c c$, light quark and even $gg$ states. The existence of shallow bound states dramatically increases the quasiparticle rescattering at low energies, reducing the viscosity and thereby explaining why heavy ion collisions at RHIC exhibit robust collective phenomena. In conformal gauge theories at finite temperature the Coulomb binding persists further in the strong coupling regime, as found for ${\cal N}=4$ SUSY YM in the Maldacena regime.Comment: v2 version have one more figure and one more reference, v3 is the same as v2 except a double-page format (the v2 had corrupted last lines on the page

Thermal Dileptons from a Nonperturbative Quark-Gluon Phase

Assuming that gluon condensates are important even above the deconfining phase transition, we develop a model for the dilepton yield from a quark gluon plasma. Using a simple fire ball description of a heavy ion collision, and various estimates of the strengths of the gluon condensates, we compare our predicted dilepton yields with those observed in the CERES and HELIOS experiments at CERN. The simple model gives an adequate description of the data, and in particular it explains the observed considerable enhancement of the yield in the low mass region.Comment: 7 pages, 6 figures, reference adde

Dilepton and Photon Emission Rates from a Hadronic Gas III

We extend our early analyses of the dilepton and photon emission rates from a hadronic gas to account for strange mesons using a density expansion. The emission rates are reduced to vacuum correlation functions using three-flavor chiral reduction formulas, and the latters are assessed in terms of empirical data. Using a fire-ball, we compare our results to the low and intermediate mass dilepton data available from CERN. Our results suggest that a baryon free hadronic gas does not account for the excess of low mass dielectrons observed at CERES but do well in accounting for the intermediate dimuons at HELIOS. The same observations apply to the recent low and high $p_t$ dielectron rates from CERES.Comment: 12 pages LaTeX, 11 eps figure

The Skyrme model predictions for the 27J=3/2{\bf 27}_{J=3/2} mass spectrum and the 273/2{\bf 27}_{3/2}-10ˉ\bar{\bf 10} mass splittings

The ${\bf 27}_{J=3/2}$-plet mass spectrum and the ${\bf 27}_{3/2}$-$\bar{\bf 10}$ mass splittings are computed in the framework of the minimal SU(3)$_f$ extended Skyrme model. As functions of the Skyrme charge $e$ and the SU(3)$_f$ symmetry breaking parameters the predictions are presented in tabular form. The predicted mass splitting ${\bf 27}_{3/2}$-$\bar{\bf 10}$ is the smallest among all SU(3)$_f$ baryonic multiplets.Comment: 4 pages, 2 tables, version to appear in Phys. Rev.