Hadrons Above T_c

Hadronic modes in the quark-gluon plasma and their spectral properties are discussed on the basis of the lattice QCD data.Comment: Invited talk at the International Conference on "QCD and Hadronic Physics", June 16-20, 2005, Beijing, China. 6 pages, 3 fugures, typeset with ws-ijma.cl

Chiral Gap and Collective Excitations in Monolayer Graphene from Strong Coupling Expansion of Lattice Gauge Theory

Using the strong coupling expansion of the compact and non-compact U(1) lattice gauge theory for monolayer graphene, we show analytically that fermion bandgap and pseudo Nambu--Goldstone exciton (pi-exciton) are dynamically generated due to chiral symmetry breaking. The mechanism is similar to the generation of quark mass and pion excitation in quantum chromodynamics (QCD). We derive a formula for the pi-exciton analogous to the Gell-Mann--Oakes--Renner (GOR) relation in QCD. Experimental confirmation of the GOR relation on a suspended monolayer graphene would be a clear evidence of chiral symmetry breaking.Comment: 4 pages, 3 figures; references and comments added; brief comments about non-compact formulatio

QCD Level Density from Maximum Entropy Method

We propose a method to calculate the QCD level density directly from the thermodynamic quantities obtained by lattice QCD simulations with the use of the maximum entropy method (MEM). Understanding QCD thermodynamics from QCD spectral properties has its own importance. Also it has a close connection to phenomenological analyses of the lattice data as well as experimental data on the basis of hadronic resonances. Our feasibility study shows that the MEM can provide a useful tool to study QCD level density.Comment: 6 pages, 4 figures, talk presented at Lattice 2005 (Non-zero temperature and density