We construct an effective action for QCD by expanding the quark determinant in powers of the chemical potential at finite temperature in the case of massless quarks. To cut the infinite series we adopt the Weinberg power counting criterium. We compute the minimal effective action (∼ p), expanding in the external momentum, which implies the use of the Hard Thermal Loop approximation. Our main re...

We propose the study of non-local gauge invariant operators to obtain an uncontaminated ground state for hadrons. The efficiency of the operators is shown by looking at the wave function of the first excited state, which has a node as a function of spatial extent of the operator.

We deal with extensions of the Standard Model by adding horizontal interactions between particle generations. We calculate two loop corrections caused by the presence of coupling between hypothetical horizontal gauge bosons and matter field, both at low and high energy. It is proved numerically that the coupling of such extra bosons does not affect the positive features of unified and extended ...

(Received February 1, 2008) We review some motivation behind the introduction of chiral random matrix models in QCD, with particular emphasis on the importance of the Gell-Mann-Oakes (GOR) relation for these arguments. We show why the microscopic limit is universal in power counting, and present arguments for why the macroscopic limit is generic for a class of problems that defy power counting,...

We find an eleven dimensional description of the D-2-brane of the massive type IIA theory as a first step towards an understanding of this theory in eleven dimensions. By means of a world-volume IIA/M theory duality transformation we show that the massive D-2-brane is equivalent to the dimensional reduction of the eleven dimensional membrane coupled to an auxiliary vector field. The role of thi...

We study a gauge fixed action of open string field theory expanded around the universal solution, which has been found as an analytic classical solution with one parameter, a. For a > −1/2, we are able to reproduce open string scattering amplitudes in the theory fixed in the Siegel gauge. At a = −1/2, all scattering amplitudes vanish and there is no open string excitation in the gauge fixed the...

We find that the fermion determinant is not generally positive in a class of lattice actions recently constructed by Cohen et al. [hep-lat/0307012]; these are actions that contain an exact lattice supersymmetry and have as their target (continuum) theory (4,4) 2-dimensional super-Yang-Mills. We discuss the implications of this finding for lattice simulations and give some preliminary results fo...

Our study of the energy distribution has shown that the strength of the first order transition in the fourdimensional compact U(1) lattice gauge theory decreases when the coupling λ of the monopole term increases. The disappearance of the energy gap for sufficiently large values of λ indicates that the transition ultimately becomes of second order. In our present investigation, based on a finit...

Adding fundamental matter of mass mQ to N = 4 Yang Mills theory, we study quarkonium, and “generalized quarkonium” containing light adjoint particles. At large ’t Hooft coupling the states of spin ≤ 1 are anomalously light (Kruczenski et al., hep-th/0304032). We examine their form factors, and show these hadrons are unlike any known in QCD. By a traditional yardstick they appear infinite in siz...