arXiv subjects

Katsuya Ishiguro

Publications and source records attributed to Katsuya Ishiguro.

At least 19 recordsLinked to original sources

arXiv2022

Monopoles of the Dirac type and color confinement in QCD -- First results of SU(3) numerical simulations without gauge fixing

If non-Abelian gauge fields in $SU(3)$ QCD have a line-singularity leading to non-commutativity with respect to successive partial-derivative operations, the non-Abelian Bianchi identity is violated. The violation as an operator is shown to be equivalent to violation of Abelian-like Bianchi identities. Then there appear eight Abelian-like conserved magnetic monopole currents of the Dirac type in $SU(3)$ QCD. Exact Abelian (but kinematical) symmetries appear in non-Abelian $SU(3)$ QCD. Here we try to show the Abelian dual Meissner effect due to the above Abelian-like monopoles are responsible for color confinement in $SU(3)$ QCD. If this picture is correct, the string tension of non-Abelian Wilson loops is reproduced fully by that of the Abelian Wilson loops. This is called as perfect Abelian dominance. In this report, the perfect Abelian dominance is shown to exist with the help of the multilevel method but without introducing additional smoothing techniques like partial gauge fixings, although lattice sizes studied are not large enough to study the infinite volume limit. Perfect monopole dominance is also shown without any additional gauge fixing. Abelian electric fields are squeezed due to solenoidal monopole currents and the penetration length for an Abelian electric field of a single color is the same as that of non-Abelian electric field. The coherence length is also measured directly through the correlation of the monopole density and the Polyakov loop pair. The Ginzburg-Landau parameter indicates that the vacuum type is the weak type I (dual) superconductor. The results obtained above without any additional assumptions as well as more clear previous $SU(2)$ results seem to suggest strongly the above Abelian dual Meissner picture of color confinement mechanism.

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arXiv2021

Abelian monopoles of the Dirac type and color confinement in QCD

We present results of $SU(3)$ Monte-Carlo studies of a new color confinement scheme due to Abelian-like monopoles of the Dirac type without any gauge-fixing. We get (1) perfect Abelian dominance with respect to the static potentials on $12^4\sim 16^4$ lattice at $β=5.6-5.8$ using the multilevel method, (2) monopole as well as Abelian dominances with respect to the static potentials by evaluating Polyakov loop correlators on $24^3\times4$ lattice at $β=5.6$. (3) Abelian dual Meissner effects are studied directly by measuring Abelian color fields and monopole currents around the static source. The vacuum in pure $SU(3)$ seems to be of the type 1 near the border between both types, although scaling is not studied yet.

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arXiv2021

Flux tube profiles in two-color QCD at low temperature and high density

We investigate the temperature and density dependence of the color flux tube structure of dense two-color QCD with $N_f = 2$ Wilson fermions by using a lattice simulation. From Refs. [1] and [2], we have already clarified the rich phase structure in the low temperature region, including the hadronic and superfluid phases. In this study we measure the quark-antiquark potential and color flux tube profiles in such a low temperature region and find that even in the high density superfluid phase, the color electric field is squeezed into a flux tube as in the low density hadronic phase.

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arXiv2021

Monopoles of the Dirac type and color confinement in QCD

We present results of $SU(3)$ Monte-Carlo studies of a new color confinement scheme proposed recently due to Abelian-like monopoles of the Dirac type corresponding in the continuum limit to violation of the non-Abelian Bianchi identities (VNABI). The simulations are done without any additional gauge-fixing smoothing the vacuum. We get for the first time, in pure $SU(3)$ simulations with the standard Wilson action, (1) the perfect Abelian dominance with respect to the static potentials on $12^4\sim 16^4$ lattices at $β=5.6-5.8$ using the multilevel method. (2) The perfect monopole as well as Abelian dominances with respect to the static potentials by evaluating the Polyakov loop correlators on $24^3\times4$ at $β=5.6$. The Abelian photon part gives zero string tension. (3) The Abelian dual Meissner effect is observed with respect to the Abelian gauge field and Abelian monopoles. The Abelian electric field of a color is squeezed due to the solenoidal monopole current with the corresponding color. Although the scaling and the volume dependence are not yet studied in $SU(3)$, the present results and the previous $SU(2)$ results are consistent with the new Abelian picture of color confinement that each one of eight (three in $SU(2)$) colored electric flux is squeezed by the corresponding colored Abelian-like monopole of the Dirac type corresponding to VNABI.

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arXiv2020

New Abelian-like monopoles and the dual Meissner effect

Violation of non-Abelian Bianchi identity can be regarded as $N^2-1$ Abelian-like monopole currents in the continuum SU(N) QCD. Three Abelian-like monopoles, when defined in SU(2) gluodynamics on the lattice à la DeGrand-Toussaint, are shown to have the continuum limit with respect to the color-invariant monopole density and the effective monopole action. Since each Abelian-like monopole is not gauge invariant, we have introduced various partial gauge fixing for the purpose of reducing lattice artifact monopoles in the thermalized vacuum. Here we investigate Abelian and monopole dominances and the Abelian dual Meissner effects adopting the same gauges like the maximal center gauge (MCG) in comparison with the maximal Abelian gauge (MAG). Abelian and monopole contributions to the string tension in these gauges are observed to be a little smaller than the non-Abelian string tension. However, we find that the monopole dominance is improved well when use is made of the block-spin transformations with respect to Abelian-like monopoles. We find each electric field is squeezed by the corresponding colored Abelian-like monopole in such gauges and the Abelian dual Meissner effect is observed independently for each color. Moreover, we confirm the dual Ampère's law in these new gauges as well as in MAG. The SU(2) vacuum is shown to be near the border between the type 1 and type 2 dual superconductors. The penetration length is almost equal for the four gauge fixings and the vacuum type in MCG is almost the same value as the previous results. These results are consistent with the previous results suggesting the continuum limit and the gauge-independence of Abelian monopoles.

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arXiv2018

A new scheme for color confinement and violation of the non-Abelian Bianchi identities

A new scheme for color confinement in QCD due to violation of the non-Abelian Bianchi identities proposed earlier is revised. The violation of the non-Abelian Bianchi identities (VNABI) $J_μ$ is equal to Abelian-like monopole currents $k_μ$ defined by the violation of the Abelian-like Bianchi identities. VNABI satisfies $\partial_μJ_μ=0$. There are $N^2-1$ conserved magnetic charges in $SU(N)$ QCD. The charge of each component of VNABI is assumed to satisfy the Dirac quantization condition. %%%%% Each color component of the non-Abelian electric field $E^a$ is squeezed by the corresponding color component of the solenoidal current $J^a_μ$. Then only the color singlets alone can survive as a physical state and non-Abelian color confinement is realized. Numerical studies are done in the framework of $SU(2)$ lattice gauge theory. We adopt an Abelian-like definition of monopole following DeGrand-Toussaint as a lattice version of VNABI. To reduce severe lattice artifacts, we introduce various techniques of smoothing the thermalized vacuum such as the maximal center gauge (MCG) fixing. We measure the density $ρ(a(β),n)=\sqrt{(k_n^1)^2+(k_n^2)^2+(k_n^3)^2}/(4\sqrt{4}Vb^3)$, where $k_n^a$ is an $n$ blocked monopole in the color direction $a$ and $b=na(β)$ is the blocked lattice spacing. Beautiful scaling behaviors are seen when we plot $ρ(a(β),n)$ versus $b=na(β)$. A single universal curve $ρ(b)$ is found from $n=1\sim 12$, which suggests that $ρ(a(β),n)$ is a function of $b=na(β)$ alone. The universal curve seems independent of a gauge fixing procedure used to smooth the lattice vacuum when the scaling is obtained. The scaling shows that the lattice definition of VNABI has the continuum limit.

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arXiv2016

Abelian spatial string tension in finite temperature SU(2) gauge theory

We investigate Abelian and monopole contributions to spatial string tension in the deconfined phase of finite temperature SU(2) gauge theory without imposing any gauge fixing conditions. Lattice calculations of non-Abelian and Abelian spatial string tensions from the Wilson action at gauge coupling $β=2.74$ and lattice volume $24^3\times{N_t}$ $(N_{t}=\left\{ 24,8,6,4,2)\right\}$ show that these string tensions agree with each other within error bars at any adopted value of $N_t$, which implies Abelian dominance. From measurements of non-Abelian, Abelian, and monopole forces that arise from the corresponding spatial string tension, furthermore, we find the tendency that the monopole contribution to the spatial string tension can be almost as large as the non-Abelian and Abelian ones. The temperature dependence of the calculated non-Abelian and Abelian spatial string tensions allows us to conclude that the concept of dimensional reduction holds both for non-Abelian and Abelian sectors at temperatures higher than twice the critical temperature.

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arXiv2007

Topological defects and equation of state of gluon plasma

We show that the degrees of freedom associated with magnetic monopole- and vortexlike gluonic configurations make a strong contribution to the anomaly of the energy-momentum tensor of Yang-Mills theory in the deconfinement phase immediately above the critical temperature. As is well known in zero-temperature Yang-Mills theory, the monopoles and vortices are constituents of a generic gluonic object in which the two neighbor monopoles are connected together by a segment of vortex string. Our results provide evidence that the monopole-vortex chains in SU(2) gauge theory and their SU(3) counterparts, the monopole-vortex nets, are thermodynamically relevant degrees of freedom in the gluonic plasma.

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arXiv2007

Gauge-independent Abelian mechanism of color confinement in gluodynamics

Abelian mechanism of non-Abelian color confinement is observed in a gauge-independent way by high precision lattice Monte Carlo simulations in gluodynamics. An Abelian gauge field is extracted with no gauge-fixing. A static quark-antiquark potential derived from Abelian Polyakov loop correlators gives us the same string tension as the non-Abelian one. The Hodge decomposition of the Abelian Polyakov loop correlator to the regular photon and the singular monopole parts also reveals that only the monopole part is responsible for the string tension. The investigation of the flux-tube profile then shows that Abelian electric fields defined in an arbitrary color direction are squeezed by monopole supercurrents with the same color direction, and the quantitative features of flux squeezing are consistent with those observed previously after Abelian projections with gauge fixing. Gauge independence of Abelian and monopole dominance strongly supports that the mechanism of non-Abelian color confinement is due to the Abelian dual Meissner effect.

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arXiv2007

Abelian dominance in local unitary gauges and without gauge-fixing in pure SU(2) QCD

We perform lattice Monte-Carlo simulations of pure SU(2) QCD using the multi-level method. We find Abelian dominance in local unitary gauges such as those diagonalizing a plaquette. A static potential described by Abelian link fields alone gives us the same string tension as that of a non-Abelian potential. Abelian dominance of the string tension and Abelian flux tube profiles are observed also without gauge-fixing, i.e., without any Abelian projection. On the basis of these results, we propose a simple gauge-independent Abelian confinement scenario without any Abelian projection. All color components of the non-Abelian field strength become Abelian dominant in the infrared region. The Abelian dual Meissner effect works in any color direction. Abelian neutral states in any color directions which are just non-Abelian color-singlet can exist as a physical state. In this way, the non-Abelian color confinement could be understood in the framework of the Abelian dual Meissner effect.

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arXiv2007

Abelian dominance and the dual Meissner effect in local unitary gauges in SU(2) gluodynamics

Performing highly precise Monte-Carlo simulations of SU(2) gluodynamics, we observe for the first time Abelian dominance in the confining part of the static potential in local unitary gauges such as the F12 gauge. We also study the flux-tube profile between the quark and antiquark in these local unitary gauges and find a clear signal of the dual Meissner effect. The Abelian electric field is found to be squeezed into a flux tube by the monopole supercurrent. This feature is the same as that observed in the non-local maximally Abelian gauge. These results suggest that the Abelian confinement scenario is gauge independent. Observing the important role of space-like monopoles in the Polyakov gauge also indicates that the monopoles defined on the lattice do not necessarily correspond to those proposed by 't Hooft in the context of Abelian projection.

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arXiv2005

Gauge invariance of the dual Meissner effect in QCD

The dual Meissner effect is described and numerically observed in a gauge-invariant way in lattice Monte-Carlo simulations of pure SU(2) QCD. A gauge-invariant Abelian-like field strength is defined in terms of a unit-vector in color space which is constructed by a non-Abelian field strength itself. A gauge-invariant monopole-like quantity is defined by a violation of the Bianchi identity with respect to the Abelian-like field strength. The squeezing of the non-Abelian electric field $\sqrt{\sum_a(E^a_i)^2}$ between a pair of static quark and anti-quark occurs due to the solenoidal current coming from the gauge-invariant monopole-like quantity. An equation similar to the dual London equation is confirmed approximately in the long-range region.

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arXiv2005

Gauge invariant 'monopoles' and color confinement mechanism

The dual Meissner effect is described and numerically observed in a gauge-invariant way in lattice Monte-Carlo simulations of pure SU(2) QCD. A gauge-invariant monopole-like quantity on the lattice is defined by a gauge-invariant Abelian-like field strength. The Abelian-like field strength is expressed in terms of a unit-vector in color space which is constructed by a non-Abelian field strength itself. It is just equal to the absolute value of the corresponding non-Abelian field strength except for the sign. In this note we show the theoretical background and most numerical results will be published in a separate report \cite{Suzuki:2005lat052} in this conference.

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arXiv2005

Gauge invariance of the Abelian dual Meissner effect in pure SU(2) QCD

The dual Meissner effect is described and numerically observed in a gauge-invariant way in lattice Monte-Carlo simulations in pure SU(2) QCD. The squeezing of the non-Abelian electric field between a pair of static quark and anti-quark occurs due to the solenoidal current coming from the gauge-invariant monopole-like quantity. Preliminary results are obtained with respect to the vacuum type of the confinement phase. The SU(2) QCD vacuum seems near the border between the type 1 and the type 2 dual superconductors. The theoretical background of this idea is published in another report \cite{Suzuki:2005lat051}. Here we show numerical results in this note.

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arXiv2005

Towards SU(2) invariant formulation of the monopole confinement mechanism

The type of the vacuum is studied numerically in the maximally Abelian (MA) gauge and in the Landau (LA) gauge of SU(2) gluodynamics. The type of the vacuum is determined by a ratio between the dual coherence and the dual penetration lengths. The dual penetration length is determined from correlations between Wilson loops and electric fields in both gauges. The dual coherence length is found from correlations between Wilson loops and dimension-2 operators both in the MA and the LA gauges. This determination of the coherence length is supported by theoretical and numerical observation that the dimension-2 gluon operators in the studied gauges have a strong correlation with the monopole current determined in the MA gauge. We find numerically that the dual penetration lengths and the dual coherence lengths in the LA and the MA gauges are almost the same. Therefore we conclude, that in both gauges the type of the vacuum in the confinement phase is near to the border between the type 1 and the type 2 dual superconductors.

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arXiv2005

Vacuum type of SU(2) gluodynamics in maximally Abelian and Landau gauges

The vacuum type of SU(2) gluodynamics is studied using Monte-Carlo simulations in maximally Abelian (MA) gauge and in Landau (LA) gauge, where the dual Meissner effect is observed to work. The dual Meissner effect is characterized by the coherence and the penetration lengths. Correlations between Wilson loops and electric fields are evaluated in order to measure the penetration length in both gauges. The coherence length is shown to be fixed in the MA gauge from measurements of the monopole density around the static quark-antiquark pair. It is also shown numerically that a dimension 2 gluon operator A^+A^-(s) and the monopole density has a strong correlation as suggested theoretically. Such a correlation is observed also between the monopole density and A^2(s)= A^+A^-(s) + A^3A^3(s) condensate if the remaining U(1) gauge degree of freedom is fixed to U(1) Landau gauge (U1LA). The coherence length is determined numerically also from correlations between Wilson loops and A^+A^-(s) and A^2(s) in MA + U1LA gauge. Assuming that the same physics works in the LA gauge, we determine the coherence length from correlations between Wilson loops and A^2(s). Penetration lengths and coherence lengths in the two gauges are almost the same. The vacuum type of the confinement phase in both gauges is near to the border between the type 1 and the type 2 dual superconductors.

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arXiv2005

Entropy of spatial monopole currents in pure SU(2) QCD at finite temperature

We study properties of space-like monopole trajectories in the Maximal Abelian gauge of quenched SU(2) QCD at the finite temperature. We concentrate on infrared monopole clusters which are responsible for the confinement properties of the theory. We determine numerically the effective action of the monopoles projected onto the three-dimensional time-slice. Then we derive the length distributions of the monopole loops and fix their entropy.

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arXiv2005

The Dual Meissner Effect and Magnetic Displacement Currents

The dual Meissner effect is observed without monopoles in quenched $SU (2)$ QCD with Landau gauge-fixing. Magnetic displacement currents which are time-dependent Abelian magnetic fields play a role of solenoidal currents squeezing Abelian electric fields. Monopoles are not always necessary to the dual Meissner effect. The squeezing of the electric flux means the dual London equation and the massiveness of the Abelian electric fields as an asymptotic field. The mass generation of the Abelian electric fields is related to a gluon condensate $ \neq 0$ of mass dimension 2.

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