2,641 research outputs found
Study of unstable particle through the spectral function in O(4) theory
We test application of the maximum entropy method to decompose the states
contributing to the unstable correlation function through the spectral
function in the four dimensional O(4) theory. Reliable results are
obtained for the mass and two-particle state energy using
only the correlation function. We also find that the property of the
particle is different between the unstable ()
and stable () cases.Comment: Lattice2002(spectrum), 3 page
Metal-insulator transition caused by the coupling to localized charge-frustrated systems under ice-rule local constraint
We report the results of our theoretical and numerical study on electronic
and transport properties of fermion systems with charge frustration. We
consider an extended Falicov-Kimball model in which itinerant spinless fermions
interact repulsively by U with localized particles whose distribution satisfies
a local constraint under geometrical frustration, the so-called ice rule. We
numerically calculate the density of states, optical conductivity, and inverse
participation ratio for the models on the pyrochlore, checkerboard, and kagome
lattices, and discuss the nature of metal-insulator transitions at commensurate
fillings. As a result, we show that the ice-rule local constraint leads to
several universal features in the electronic structure; a charge gap opens at a
considerably small U compared to the bandwidth, and the energy spectrum
approaches a characteristic form in the large U limit, that is, the
noninteracting tight-binding form in one dimension or the -functional
peak. In the large U region, the itinerant fermions are confined in the
macroscopically-degenerate ice-rule configurations, which consist of a bunch of
one-dimensional loops: We call this insulating state the charge ice. On the
other hand, transport properties are much affected by the geometry and
dimensionality of lattices; e.g., the pyrochlore lattice model exhibits a
transition from a metallic to the charge-ice insulating state by increasing U,
while the checkerboard lattice model appears to show Anderson localization
before opening a gap. Meanwhile, in the kagome lattice case, we do not obtain
clear evidence of Anderson localization. Our results elucidate the universality
and diversity of phase transitions to the charge-ice insulator in fully
frustrated lattices.Comment: 16 pages, 17 figure
Quantum melting of charge ice and non-Fermi-liquid behavior: An exact solution for the extended Falicov-Kimball model in the ice-rule limit
An exact solution is obtained for a model of itinerant electrons coupled to
ice-rule variables on the tetrahedron Husimi cactus, an analogue of the Bethe
lattice of corner-sharing tetrahedra. It reveals a quantum critical point with
the emergence of non-Fermi-liquid behavior in melting of the "charge ice"
insulator. The electronic structure is compared with the numerical results for
the pyrochlore-lattice model to elucidate the physics of electron systems
interacting with the tetrahedron ice rule.Comment: 5 pages, 4 figure
Pion decay constant in quenched QCD with Kogut-Susskind quarks
We present a non-perturbative calculation for the pion decay constant with
quenched Kogut-Susskind quarks. Numerical simulations are carried out at and 6.2 with various operators extending over all flavors. The
renormalization correction is applied for each flavor by computing
non-perturbative renormalization constants, and it is compared with a
perturbative calculation. We also study the behavior of in the
continuum limits for both non-perturbative and perturbative calculations. The
results in the continuum limit is also discussed.Comment: LATTICE99(matrix elements) 3 pages, 4 eps figure
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