69,024 research outputs found
Monopole Condensation in Lattice SU(2) QCD
This is the short review of Monte-Carlo studies of quark confinement in
lattice QCD. After abelian projections both in the maximally abelian and
Polyakov gauges, it is seen that the monopole part alone is responsible for
confinement. A block spin transformation on the dual lattice suggests that
lattice QCD is always ( for all ) in the monopole condensed
phase and so in the confinement phase in the infinite volume limit.Comment: Contribution to Confinement '95, March 1995, Osaka, Japan. Names of
figure files are corrected. 8 page uuencoded latex file and 10 ps figure
An Almost Perfect Lattice Action for infrared QCD
A block-spin transformation on the dual lattice leads us to an almost perfect
lattice action for monopoles and strings in QCD. The perfect operator for a
static quark potential is fixed when we compare the above action with the
perfect action obtained analytically after infinite-step block-spin
transformations in a simple case. The continuum rotational invariance is
restored and the physical value of the string tension is reproduced fairly
well. Gauge independence of the abelian and the monopole scenario is discussed.Comment: Proceedings of the International Workshop on Nonperturbative Methods
and Lattice QCD, Guangzhou, Chin
Development of Cu-spin correlation in Bi_1.74_Pb_0.38_Sr_1.88_Cu_1-y_Zn_y_O_6+d_ high-temperature superconductors observed by muon spin relaxation
A systematic muon-spin-relaxation study in Bi-2201 high-Tc cuprates has
revealed for the first time that the Cu-spin correlation (CSC) is developed at
low temperatures below 2 K in a wide range of hole concentration where
superconductivity appears. The CSC tends to become weak gradually with
increasing hole-concentration. Moreover, CSC has been enhanced through the 3%
substitution of Zn for Cu. These results are quite similar to those observed in
La-214 high-Tc cuprates. Accordingly, it has been suggested that the intimate
relation between the so-called spin-charge stripe correlations and
superconductivity is a universal feature in hole-doped high-Tc cuprates.
Furthermore, apparent development of CSC, which is suppressed through the Zn
substitution oppositely, has been observed in non-superconducting heavily
overdoped samples, being argued in the context of a recently proposed
ferromagnetic state in heavily overdoped cuprates.Comment: 6 pages, 5 figure
Time-Dependent Dynamics of the Bose-Fermi Mixed Condensed System
We study the monopole oscillation in the bose-fermi mixed condensed system by
performing the time-dependent Gross-Pitaevsky (GP) and Vlasov equations. We
find that the big damping exists for the fermion oscillation in the mixed
system even at zero temperatureComment: 5pages, 2 figure
Hole-trapping by Ni, Kondo effect and electronic phase diagram in non-superconducting Ni-substituted La2-xSrxCu1-yNiyO4
In order to investigate the electronic state in the normal state of high-Tc
cuprates in a wide range of temperature and hole-concentration, specific-heat,
electrical-resistivity, magnetization and muon-spin-relaxation (muSR)
measurements have been performed in non-superconducting Ni-substituted
La2-xSrxCu1-yNiyO4 where the superconductivity is suppressed through the
partial substitution of Ni for Cu without disturbing the Cu-spin correlation in
the CuO2 plane so much. In the underdoped regime, it has been found that there
exist both weakly localized holes around Ni and itinerant holes at high
temperatures. With decreasing temperature, all holes tend to be localized,
followed by the occurrence of variable-range hopping conduction at low
temperatures. Finally, in the ground state, it has been found that each Ni2+
ion traps a hole strongly and that a magnetically ordered state appears. In the
overdoped regime, on the other hand, it has been found that a Kondo-like state
is formed around each Ni2+ spin at low temperatures. In conclusion, the ground
state of non-superconducting La2-xSrxCu1-yNiyO4 changes upon hole doping from a
magnetically ordered state with the strong hole-trapping by Ni2+ to a metallic
state with Kondo-like behavior due to Ni2+ spins, and the quantum phase
transition is crossover-like due to the phase separation into short-range
magnetically ordered and metallic regions.Comment: 9 pages, 8 figures, accepted for publication in Phys. Rev.
Effective Monopole Action at Finite Temperature in SU(2) Gluodynamics
Effective monopole action at finite temperature in SU(2) gluodynamics is
studied on anisotropic lattices. Using an inverse Monte-Carlo method and the
blockspin transformation for space directions, we determine 4-dimensional
effective monopole action at finite temperature. We get an almost perfect
action in the continuum limit under the assumption that the action is composed
of two-point interactions alone. It depends on a physical scale and the
temperature . The temperature-dependence appears with respect to the
spacelike monopole couplings in the deconfinement phase, whereas the timelike
monopole couplings do not show any appreciable temperature-dependence. The
dimensional reduction of the 4-dimensional SU(2) gluodynamics ((SU(2)))
at high temperature is the 3-dimensional Georgi-Glashow model ().
The latter is studied at the parameter region obtained from the dimensional red
uction. We compare the effective instanton action of with the
timelike monopole action obtained from (SU(2)). We find that both agree
very well for at large region. The dimensional reduction
works well also for the effective action.Comment: 34 pages, 23 figure
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