arXiv subjects
Publications and source records attributed to Anna Hasenfratz.
We present a theoretically consistent definition of the topological charge operator based on renormalization group arguments. Results of the measurement of the topological susceptibility at zero and finite temperature for SU(2) gauge theory are presented.
We construct a few parameter approximate fixed point action for SU(2) pure gauge theory and subject it to scaling tests, via Monte Carlo simulation. We measure the critical coupling for deconfinement for lattices of temporal extent $N_t=2$, 3, 4, the torelon mass at fixed physical volume, and the string tension (and heavy quark potential) from Wilson loops. We calculate the topological susceptibility using inverse blocking and show that it scales over the observed range of lattice spacings.
We describe the properties of instantons in lattice gauge theory when the action is a fixed point action of some renormalization group transformation. We present a theoretically consistent method for measuring topological charge using an inverse renormalization group transformation. We show that, using a fixed point action, the action of smooth configurations with non-zero topological charge is greater than or equal to its continuum value $8π^2/g^2$.
Heavy dynamical fermions with masses around the cut-off do not change the low energy physics apart from a finite renormalization of the gauge coupling. In this paper we study how light the heavy fermions have to be to cause more than this trivial renormalization.
It is expected that the only effect of heavy dynamical fermions in QCD is to renormalize the gauge coupling. We derive a simple expression for the shift in the gauge coupling induced by $N_f$ flavors of heavy fermions. We compare this formula to the shift in the gauge coupling at which the confinement-deconfinement phase transition occurs (at fixed lattice size) from numerical simulations as a function of quark mass and $N_f$. We find remarkable agreement with our expression down to a fairly light quark mass. However, simulations with eight heavy flavors and two light flavors show that the eight flavors do more than just shift the gauge coupling. We observe confinement-deconfinement transitions at $β=0$ induced by a large number of heavy quarks. We comment on the relevance of our results to contemporary simulations of QCD which include dynamical fermions.
We investigate the gauge interaction induced by heavy fermions using both dimensional and lattice regularization. We study the condition under which heavy fermions induce a continuum gauge theory.
We investigate the detailed conditions under which a purely fermionic model with current-current interaction goes over to a renormalizable, asymptotically free SU$(N)$ gauge theory.