Michael Grady

Hadron spectra and potential screening for lattice QCD with dynamical quarks

Abstract Hybrid simulations of lattice QCD with four light quark flavors are made on an 8 3 ×16 lattice. Hadron masses are calculated from the propagators measured on both the 8 3 ×16 and doubled (8 3 ×32) lattices. The screening effects of the dynamical quarks on the interquark potential are observed. The finite temperature phase transition is observed at T c ≃ 110 MeV and its effects on the pion mass and potential screening noted.

Finite-temperature phase transition in SU(2) lattice gauge theory with extended action

We study the three dimensional fundamental-adjoint SU(2) lattice gauge theory at finite temperature by Monte Carlo simulations. We find that the finite-temperature deconfinement phase transition line joins the first-order bulk phase transition line at its endpoint. Moreover, across the bulk transition line, the Polyakov loop undergoes a discontinuous jump implying the existence of both confining and deconfining phases on its two sides. Implications for universality and the nature of the confining-deconfining transition are discussed.

Alternative scaling hypothesis forSU(2) andSU(3) lattice gauge theories

High precision data from a variety of sources forSU(2) andSU(3) Wilson action lattice gauge theory are analyzed with respect to the hypothesis of the possible existence of a zero temperature deconfining phase transition, in analogy with theU(1) theory. The internal energy, specific heat, string tension, and Wilson line, fit well to correlation length scaling laws associated with a finite order transition occurring at the weak coupling end of the crossover region for both theories. TheSU(2) theory is consistent with a correlation length exponent ν=2/3 and critical pointβc≈2.47. ForSU(3) the data fit well to ν=1 andβc≈6.69. Additional indirect evidence for the existence of such phase transitions is discussed, as is the possible crucial role of light dynamical fermions in the confinement mechanism.

Spurious first-order phase transitions from topological effects on the lattice

Abstract The discrete nature of the topological charge, Q , leads to sudden jumps in observables when Q changes by ±1 in lattice gauge theory Monte Carlo simulations. This is especially apparent for couplings for which Q = 0 and Q = ±1 are the dominant configurations for the lattice being studied. Metastability of gauge configurations responsible for topological charge, and the strong dependence of quantities such as (ψψ) on Q leads to behavior that has very much the appearance of a first-order chiral phase transition. However, this is only a result of topological charge quantization, the effects of which disappear in the infinite-lattice limit, and not a true phase transition. The phenomenon is demonstrated with Monte Carlo simulations of two-dimensional U(1) lattice gauge theory. The possibility that some signals attributed to first-order chiral transitions in four-dimensional theories could be due to this effect is discussed.

Cabibbo mixing from strong-interaction condensates

SummaryIn a scenario where the down and strange quark weak-interaction eigenstates are given a current mass, it is argued that a likely pattern of chiral symmetry breaking is one in which

Critical or tricritical point in mixed-action SU(2) lattice gauge theory?

\left\langle {\bar uu} \right\rangle ,\left\langle {\bar dd} \right\rangle

Monopole loop distribution and confinement in SU(2) lattice gauge theory

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