We study instanton effects in QCD at very high baryon density. In this regime instantons are suppressed by a large power of (ΛQCD/μ), where ΛQCD is the QCD scale parameter and μ is the baryon chemical potential. Instantons are nevertheless important because they contribute to several physical observables that vanish to all orders in perturbative QCD. We study, in particular, the chiral condensa...

The Perturbative QCD Potential and the t ¯ t Threshold Abstract We include the full second-order corrections to the static QCD potential in the analysis of the t ¯ t threshold cross section. There is an unexpectedly large difference between the QCD potential improved by the renormalization-group equation in momentum space and the potential improved by the renormalization-group equation in coord...

It is believed that QCD undergoes phase transitions as temperature T and the baryon density, controlled by a chemical potential μ, increase. For example, an expected phase structure is found in Fig.1 of ref. 1. To theoretically investigate what really happens at non-zero T and μ in QCD, lattice calculations seem ideal. Indeed, as reviewed in ref. 2, lattice QCD investigations are very successfu...

With the help of M-theory configuration of N=1 supersymmetric QCD, we analyze the strong coupling moduli of N=1 theory and its relation with S-duality transformation in N=2 supersymmetric QCD. As a result we confirm that two type-IIA descriptions for N=1 supersymmetric QCD, one of them being strong coupling description and another being weak, correspond to a single M-theory description for N=1 ...