8,004 research outputs found

### Non-trivial Center Dominance in High Temperature QCD

We investigate the properties of quarks and gluons above the chiral phase
transition temperature $T_c,$ using the RG improved gauge action and the Wilson
quark action with two degenerate quarks mainly on a $32^3\times 16$ lattice. In
the one-loop perturbation theory, the thermal ensemble is dominated by the
gauge configurations with effectively $Z(3)$ center twisted boundary
conditions, making the thermal expectation value of the spatial Polyakov loop
take a non-trivial $Z(3)$ center. This is in agreement with our lattice
simulation of high temperature QCD. We further observe that the temporal
propagator of massless quarks at extremely high temperature $\beta=100.0 \, (T
\simeq10^{58} T_c)$ remarkably agrees with the temporal propagator of free
quarks with the $Z(3)$ twisted boundary condition for $t/L_t \geq 0.2$, but
differs from that with the $Z(3)$ trivial boundary condition. As we increase
the mass of quarks $m_q$, we find that the thermal ensemble continues to be
dominated by the $Z(3)$ twisted gauge field configurations as long as $m_q \le
3.0 \, T$ and above that the $Z(3)$ trivial configurations come in. The
transition is essentially identical to what we found in the departure from the
conformal region in the zero-temperature many-flavor conformal QCD on a finite
lattice by increasing the mass of quarks. We argue that the behavior is
consistent with the renormalization group analysis at finite temperature.Comment: 16 pages, 9 figures; 4 tables, an appendix adde

### IR fixed points in $SU(3)$ gauge Theories

We propose a novel RG method to specify the location of the IR fixed point in
lattice gauge theories and apply it to the $SU(3)$ gauge theories with $N_f$
fundamental fermions. It is based on the scaling behavior of the propagator
through the RG analysis with a finite IR cut-off, which we cannot remove in the
conformal field theories in sharp contrast with the confining theories. The
method also enables us to estimate the anomalous mass dimension in the
continuum limit at the IR fixed point. We perform the program for $N_f=16, 12,
8$ and $N_f=7$ and indeed identify the location of the IR fixed points in all
cases.Comment: 7 pages, 7 figures, 1 table: the scale of the y axis in Figs..1-4
change; minor modifications as appear in PL

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