Dual Superconductor Mechanism of Confinement on the Lattice

We investigate the dual superconductor mechanism of confinement for pure SU(2) lattice gauge theory in the maximally abelian gauge. We focus on the the dual Meissner effect. We find that the transverse distribution of the longitudinal chromoelectric field due to a static quark-antiquark pair satisfies the dual London equation. Moreover we show that the size of the flux tube scales according to asymptotic freedom.Comment: LaTeX, 9 pages, 6 figures available as a PostScript file from L. Cosmai, BARI - TH 110/9

Creutz Ratios From Color-Truncated Lattice Configurations

We investigate whether information about Creutz ratios is encoded, separately, in each gluon color component of numerically generated lattice configurations. Working in SU(2) lattice gauge theory in Landau gauge, we set two of the three gluon color components to zero, and compensate for the loss of two-thirds of the fluctuation by simply rescaling the remaining component by a factor of $\sqrt{3}$. Creutz ratios are then computed with this "abelianized" configuration. We find that the Creutz ratios of loops constructed from abelianized links converge to the usual Creutz ratios in the scaling regime.Comment: 5 pages, plain LaTeX, one figur

String tension and monopoles in T≠0T \neq 0 SU(2) QCD

Monopole and photon contributions to abelian Wilson loops are calculated using Monte-Carlo simulations of finite-temperature $SU(2)$ QCD in the maximally abelian gauge. Long monopole loops alone are responsible for the behavior of the string tension in the confinement phase up to the critical $\beta_c$. Short monopole loops and photons do not contribute to the string tension. The abelian and the monopole spacial string tensions (both of which agree with the normal ones for $\beta < \beta_c$) show a $g^{4}(T) T^2$ scaling behavior in the deconfinement phase. The abelian spacial string tension is in agreement with the full one even in the deconfinement phase.Comment: 10 Pages + 1 table + 8 figures, KANAZAWA 94-1

Recent Results on the Abelian Projection of Lattice Gluodynamics

The abelian projection of lattice gluodynamics is reviewed. The main topics are: abelian and monopole dominance, monopole condensate as the disorder parameter, effective abelian Lagrangian, monopoles in the instanton field, Aharonov -- Bohm effect on the lattice.Comment: 7 pages, LaTeX, 7 PS figures, Talk presented at LATTICE9

On the perfect lattice actions of abelian-projected SU(2) QCD

We study the perfect lattice actions of abelian-projected SU(2) gluodynamics. Using the BKT and duality transformations on the lattice, an effective string model is derived from the direction-dependent quadratic monopole action, obtained numerically from SU(2) gluodynamics in maximally abelian gauge. The string tension and the restoration of continuum rotational invariance are investigated using strong coupling expansion of lattice string model analytically. We also found that the block spin transformation can be performed analytically for the quadratic monopole action.Comment: 3 pages, Latex, 1 figures; talk presented at LATTICE9

Various representations of infrared effective lattice QCD

We study various representations of the infrared effective theory of SU(2) gluodynamics starting from the monopole action derived recently. We determine the coupling constants in the abelian-Higgs model directly from lattice QCD and evaluate the type of the QCD vacuum. The string action is derived using the BKT transformation on the lattice. At the classical level this action reproduces the physical string tension with a good accuracy.Comment: 3 pages, LaTeX, 2 figures; talk presented at LATTICE9

Evidence of Strong Correlation between Instanton and QCD-monopole on SU(2) Lattice

The correlation between instantons and QCD-monopoles is studied both in the lattice gauge theory and in the continuum theory. An analytical study in the Polyakov-like gauge, where $A_4(x)$ is diagonalized, shows that the QCD-monopole trajectory penetrates the center of each instanton, and becomes complicated in the multi-instanton system. Using the SU(2) lattice with $16^4$, the instanton number is measured in the singular (monopole-dominating) and regular (photon-dominating) parts, respectively. The monopole dominance for the topological charge is found both in the maximally abelian gauge and in the Polyakov gauge.Comment: 4 pages, Latex, 3 figures. Talk presented by H. Suganuma at International Symposium on 'Lattice Field Theory', July 11 - 15, 1995, Melbourne, Australi

Room temperature and low-field resonant enhancement of spin Seebeck effect in partially compensated magnets

Resonant enhancement of spin Seebeck effect (SSE) due to phonons was recently discovered in Y3Fe5O12 (YIG). This effect is explained by hybridization between the magnon and phonon dispersions. However, this effect was observed at low temperatures and high magnetic fields, limiting the scope for applications. Here we report observation of phonon-resonant enhancement of SSE at room temperature and low magnetic field. We observed in Lu2BiFe4GaO12 and enhancement 700 % greater than that in a YIG film and at very low magnetic fields around 10-1 T, almost one order of magnitude lower than that of YIG. The result can be explained by the change in the magnon dispersion induced by magnetic compensation due to the presence of non-magnetic ion substitutions. Our study provides a way to tune the magnon response in a crystal by chemical doping with potential applications for spintronic devices.Comment: 17 pages, 4 figure