Dr Michael Teper

Abstract:

We calculate various meson and glueball masses in the version of lattice QCD with two colors and four (light) flavors. We do so both in the chirally symmetric and in the spontaneously broken phases. In the spontaneously broken phase (performed on 10320 lattices at =1.975) we find the following mass ratios: mG(0+)m=1.1(2), mG(0+)=2.8(5), m=0.39(3), mG(2+)mG(0+)=1.7(5). In the small-spatial-volume, chirally symmetric phase we explicitly observe parity doubling among the mesons but not among the glueballs. All these calculations are exploratory for a variety of reasons which we discuss. © 1991 The American Physical Society.

Abstract:

We study hadron thermodynamics with Wilson quarks. The crossover curve between the high-and low-temperature phases is determined as a function of gauge coupling and hopping parameter on 83×4 lattices. Screening lengths are calculated in the vicinity of the crossover region, and meson masses are calculated along the crossover curve on 82×16×4 and 83×16 lattices, respectively. © 1991 The American Physical Society.

Abstract:

Under the DOE Grand Challenge program, we have calculated the hadron spectrum of QCD with two flavors of dynamical quarks. We set 6 g2 = 5.6 and use bare quark masses amq = 0.025 and 0.01 to generate gauge configurations. The spectrum is calculated using both staggered and Wilson valence quarks. There are several positive features when these results are compared to those with larger lattice spacing; however, the nucleon to rho mass ratio is still too large. © 1991.

Abstract:

We present results of a numerical calculation of the chiral condensate in quenched SU(2) lattice gauge theory. The calculation proceeds by evaluating the spectral density distribution function for small eigenvalues on both the original lattice and after a factor-of-two blocking. It is performed on lattices as large as 204 and for couplings as small as β = 4/g2 = 2.6. The fitted values of the condensate as a function of β show good evidence for scaling and universality when compared with string tension measurements at the same value. At the smallest lattice spacings considered, we find evidence that a separation of length scales between ultraviolet fluctuations and those responsible for chiral symmetry breaking has occurred. A more qualitative study yields a significant correlation between the small modes |n〉 responsible for the non-zero value of 〈ψψ〉 and topological activity as revealed by the expectation value 〈n|γ5 ⊗ 1|n〉, and hence provides evidence for a topological origin of chiral symmetry breaking. Our interpretation is supported by a subsidiary calculation of the topological susceptibility of the vacuum. © 1990.

Abstract:

We have carried out a simulation of QCD using the hybrid-molecular-dynamics algorithm with two flavors of staggered quarks. The spectrum was calculated for 6g2=5.6 and dynamical quark masses amq=0.025 and 0.01. Lattice sizes of 124, 123×24, and 164 were used to generate the gauge configurations. Hadron propagators were calculated with both staggered and Wilson quarks on doubled or quadrupled latices. Finite-size effects are visible on the smaller lattices. Some improvement in the to-nucleon mass ratio and chiral symmetry is seen as compared to previous calculations, but, as in most lattice calculations, the proton-to mass ratio remains larger than in the real world and the proton splitting is too small. © 1990 The American Physical Society.