8,681 research outputs found
Kakutani Dichotomy on Free States
Two quasi-free states on a CAR or CCR algebra are shown to generate
quasi-equivalent representations unless they are disjoint.Comment: 12 page
CP^1+U(1) Lattice Gauge Theory in Three Dimensions: Phase Structure, Spins, Gauge Bosons, and Instantons
In this paper we study a 3D lattice spin model of CP Schwinger-bosons
coupled with dynamical compact U(1) gauge bosons. The model contains two
parameters; the gauge coupling and the hopping parameter of CP bosons. At
large (weak) gauge couplings, the model reduces to the classical O(3) (O(4))
spin model with long-range and/or multi-spin interactions. It is also closely
related to the recently proposed "Ginzburg-Landau" theory for quantum phase
transitions of quantum spin systems on a 2D square lattice at zero
temperature. We numerically study the phase structure of the model by
calculating specific heat, spin correlations, instanton density, and
gauge-boson mass. The model has two phases separated by a critical line of
second-order phase transition; O(3) spin-ordered phase and spin-disordered
phase. The spin-ordered phase is the Higgs phase of U(1) gauge dynamics,
whereas the disordered phase is the confinement phase. We find a crossover in
the confinement phase which separates dense and dilute regions of instantons.
On the critical line, spin excitations are gapless, but the gauge-boson mass is
{\it nonvanishing}. This indicates that a confinement phase is realized on the
critical line. To confirm this point, we also study the noncompact version of
the model. A possible realization of a deconfinement phase on the criticality
is discussed for the CP+U(1) model with larger .Comment: Discussion of finite size scaling, O(4) spin correlation adde
Heavy Quark Interactions in Finite Temperature QCD
We study the free energy of a heavy quark-antiquark pair in a thermal medium.
We constuct a simple ansatz for the free energy for two quark flavors motivated
by the Debye-H\"uckel theory of screening.Comment: 4 pages, 4 figures, contribution to the proceedings of the
International Conference on Hard and Electromagnetic Probes of High Energy
Nuclear Collisions, Ericeira, Portugal, Nov. 4-10, 200
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