arXiv subjects

Y. Shen

Publications and source records attributed to Y. Shen.

75 records · Page 5Linked to original sources

arXiv1995

Monte Carlo Study of the Yukawa Coupled Two Spin Ising Model

We consider a particular 4 state spin system composed of two Ising spins (~$s_x, \; σ_x$~) with independent hopping parameters $κ_1, κ_2$, coupled by a bilinear Yukawa term, $y s_x σ_x$. The Yukawa term is solely responsible for breaking the global $ Z_2 \times Z_2$ symmetry down to $Z_2$. This model is intended as an illustration of general coupled Higgs system where scalars can arise both as composite and elementary excitations. For the Ising example in 2d, we give convincing numerical evidence of the universality of the two spin system with the one spin Ising model, by Monte Carlo simulations and finite scaling analysis . We also show that as we approach the phase transition, universality arises by a separation of low mass spin waves from an extra set of spin waves with an energy gap that diverges as the correlations length diverges

hep-lat↗

arXiv1993

A Lattice Calculation of the Isgur-Wise Function

We calculate the Isgur-Wise function ($ξ_0$) by measuring the heavy-heavy meson transition matrix element on the lattice in the quenched approximation. The standard Wilson action is used for both the heavy and the light quarks. Our numerical results are compared with various model calculations and experimental data. In particular, using a linear fit, we find $ρ^2 = 1.24\pm .26 \pm .26 $. (The slope of $ξ_0$ at the zero-recoil point is $-ρ^2$.) Using instead the parametrization of $ξ_0$ suggested by Neubert and Rieckert and fitting the lattice data up to $v\cdot v' \sim 1.2$, we find $ρ^2_{NR}=1.41\pm.19\pm.19$

hep-lat↗

arXiv1992

The Phase Diagram of a U(1) Higgs-Yukawa Model at Finite $λ$

In this paper we investigate how the phase diagram of a U(1) symmetric Higgs-Yukawa system depends on the scalar self coupling $λ$. The phase diagram of similar models with continuous symmetry were extensively studied in the infinite scalar self coupling $λ=\infty$ limit. Recent analytical and numerical calculations at zero self coupling showed qualitatively different phase diagram, raising the question of the $λ$ dependence of the phase diagram. Here we use analytical (large $N_f$, perturbative and mean field) approximations as well as numerical simulations to investigate the system.

hep-lat↗