873 research outputs found
Gauge Theory of Composite Fermions: Particle-Flux Separation in Quantum Hall Systems
Fractionalization phenomenon of electrons in quantum Hall states is studied
in terms of U(1) gauge theory. We focus on the Chern-Simons(CS) fermion
description of the quantum Hall effect(QHE) at the filling factor
, and show that the successful composite-fermions(CF) theory
of Jain acquires a solid theoretical basis, which we call particle-flux
separation(PFS). PFS can be studied efficiently by a gauge theory and
characterized as a deconfinement phenomenon in the corresponding gauge
dynamics. The PFS takes place at low temperatures, , where
each electron or CS fermion splinters off into two quasiparticles, a fermionic
chargeon and a bosonic fluxon. The chargeon is nothing but Jain's CF, and the
fluxon carries units of CS fluxes. At sufficiently low temperatures , fluxons Bose-condense uniformly and (partly)
cancel the external magnetic field, producing the correlation holes. This
partial cancellation validates the mean-field theory in Jain's CF approach.
FQHE takes place at as a joint effect of (i) integer QHE of
chargeons under the residual field and (ii) Bose condensation of
fluxons. We calculate the phase-transition temperature and the CF
mass. PFS is a counterpart of the charge-spin separation in the t-J model of
high- cuprates in which each electron dissociates into holon and
spinon. Quasiexcitations and resistivity in the PFS state are also studied. The
resistivity is just the sum of contributions of chargeons and fluxons, and
changes its behavior at , reflecting the change of
quasiparticles from chargeons and fluxons at to electrons at
.Comment: 18 pages, 7 figure
Phase Structure of Repulsive Hard-Core Bosons in a Stacked Triangular Lattice
In this paper, we study phase structure of a system of hard-core bosons with
a nearest-neighbor (NN) repulsive interaction in a stacked triangular lattice.
Hamiltonian of the system contains two parameters one of which is the hopping
amplitude between NN sites and the other is the NN repulsion . We
investigate the system by means of the Monte-Carlo simulations and clarify the
low and high-temperature phase diagrams. There exist solid states with density
of boson and , superfluid, supersolid and
phase-separated state. The result is compared with the phase diagram of the
two-dimensional system in a triangular lattice at vanishing temperature.Comment: 4+epsilon pages, 11 figures, Version to be published in Phys.Rev.
Casimir Energy of the Universe and the Dark Energy Problem
We regard the Casimir energy of the universe as the main contribution to the
cosmological constant. Using 5 dimensional models of the universe, the flat
model and the warped one, we calculate Casimir energy. Introducing the new
regularization, called {\it sphere lattice regularization}, we solve the
divergence problem. The regularization utilizes the closed-string
configuration. We consider 4 different approaches: 1) restriction of the
integral region (Randall-Schwartz), 2) method of 1) using the minimal area
surfaces, 3) introducing the weight function, 4) {\it generalized
path-integral}. We claim the 5 dimensional field theories are quantized
properly and all divergences are renormalized. At present, it is explicitly
demonstrated in the numerical way, not in the analytical way. The
renormalization-group function (\be-function) is explicitly obtained. The
renormalization-group flow of the cosmological constant is concretely obtained.Comment: 12 pages, 13 figures, Proceedings of DSU2011(2011.9.26-30,Beijin
Fluctuation effects of gauge fields in the slave-boson t-J model
We present a quantitative study of the charge-spin separation(CSS) phenomenon
in a U(1) gauge theory of the t-J model of high-Tc superconductures. We
calculate the critical temperature of confinement-deconfinement phase
transition below which the CSS takes place.Comment: Latex, 9 pages, 3 figure
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