# ACP Seminar (Astronomy - Cosmology - Particle Physics)

Speaker: Yoichi Iwasaki (U. Tsukuba) Conformal Theories with IR cutoff Wed, Jan 30, 2013, 13:30 - 14:30 Seminar Room A 850.pdf We give a new perspective on the dynamics of conformal theories realized in the SU(N) gauge theory, when the number of flavors N_f is within the conformal window. Motivated by the RG argument on conformal theories with a finite IR cutoff \Lambda_{IR}, we conjecture that the propagator of a meson G_H(t) on a lattice behaves at large t as a power-law corrected Yukawa-type decaying form G_H(t) = c_H \exp{(-m_H t)}/t^{\alpha_H} instead of the exponentially decaying form c_H\exp{(-m_H t)}, in the small quark mass region where m_H \le c \Lambda_{IR}: m_H is the mass of the ground state hadron in the channel H and c is a constant of order 1. The transition between the "conformal region'' and the "confining region" is a first order transition. Our numerical results verify the predictions for the N_f=7 case and the N_f=16 case in the SU(3) gauge theory with the fundamental representation. Secondly, we discuss small number of flavors (N_f=2 \sim 6) QCD at finite temperatures. We point out theoretically and verify numerically that the correlation functions at T/T_c > 1 exhibit the characteristics of conformal theories with IR cutoff, a Yukawa-type decaying form of the propagators. Further, we observe our data are consistent with the picture that the N_f=7 case and the N_f=2 at T \sim 2\, T_c case are close to the meson unparticle model. On the other hand, the N_f=16 case and the N_f=2 at T= 10^2 \sim 10^5 ,Tc cases are close to the fermion unparticle model. All results are consistent with naive physical intuition and solve long standing issues at high temperatures such as why the free energy at high temperatures does not reach the Stefan-Boltzmann ideal gas limit even at T=100 T_c.