arXiv subjects

Y. M. Cho

Publications and source records attributed to Y. M. Cho.

At least 73 records · Page 4Linked to original sources

arXiv2006

D-type Vortex and N-type Vortex in Two-gap Superconductor

We show that the two-gap superconductor has two types of non-Abrikosov magnetic vortex, the D-type which has no concentration of the condensate at the core and the N-type which has a non-vanishing concentration of the condensate at the core, which may carry $4π$-flux, $2π$-flux, or a fractional flux, depending on the parameters of the potential. Furthermore, we show that the non-Abrikosov vortex is described by two types of topology. The integer flux vortex has the non-Abelian topology $π_2(S^2)$, but the fractional flux vortex has the Abelian topology $π_1(S^1)$. We show that the inclusion of the Josephson interaction does not affect the existence of the magnetic vortex, but alter the shape of the vortex drastically.

cond-mat.supr-con↗

arXiv2006

Non-Abrikosov Vortex and Topological Knot in Two-gap Superconductor

We establish the existence of topologically stable knot in two-gap superconductor whose topology $π_3(S^2)$ is fixed by the Chern-Simon index of the electromagnetic potential. We present a helical magnetic vortex solution in Ginzburg-Landau theory of two-gap superconductor which has a non-vanishing condensate at the core, and identify the knot as a twisted magnetic vortex ring made of the helical vortex. We discuss how the knot can be constructed in the recent two-gap $\rm MgB_2$ superconductor.

cond-mat.supr-con↗

arXiv2006

New Interpretation of Skyrme Theory

Based on the proposal that the Skyrme theory is a theory of monopole we provide a new interpretation of Skyrme theory, that the theory can also be viewed as an effective theory of strong interaction which is dual to QCD, where the monopoles (not the quarks) are confined through the Meissner effect. This dual picture leads us to predict the existence of a topological glueball in QCD, a chromoelectric knot which is dual to the chromomagnetic Faddeev-Niemi knot in Skyrme theory, whose mass and decay width are estimated to be around $60 GeV$ and $8 GeV$. As importantly, the existence of the magnetic vortex and the magnetic vortex ring in Skyrme theory strongly indicates that the theory could also be interpreted to describe a very interesting low energy condensed matter physics in a completely different environment. These new interpretations of Skyrme theory puts the theory in a totally new perspective.

hep-th↗

arXiv2006

Light Propagation Effects In QED: Effective Action Approach

The effects of light propagation in constant magnetic and electric backgrounds are considered in the framework of the effective action approach. We use the exact analytic series representation for the one-loop effective action of QED and apply it to the birefringence effect. Analytical results for the light velocity modes are obtained for weak and strong field regime. We present asymptotic formulae for the light velocity modes for the ultra strong magnetic field which can be realized in some neutron stars.

hep-th↗

arXiv2005

Effective Potential of QCD

We present a simple method to calculate the one-loop effective action of QCD which reduces the calculation to that of SU(2) QCD. For the chromomagnetic background we show that the effective potential has an absolute minimum only when two color magnetic fields $H_{μν}^3$ and $H_{μν}^8$ are orthogonal to each other. For the chromoelectric background we find that the imaginary part of the effective action has a negative signature, which implies the gluon pair-annihilation. We discuss the physical implications of our result.

hep-th↗

arXiv2005

Non-Abelian Superconductivity

We establish a non-Abelian superconductivity and a non-Abelian Meissner effect by constructing an effective field theory of superconductivity in which a genuine SU(2) gauge symmetry governs the dynamics. We show that the magnetic flux is quantized in the unit of $4π/g$, not $2π/g$, in the non-Abelian superconductor.

cond-mat.supr-con↗

arXiv2005

Non-Abelian Vortices in Condensed Matter Physics

We study the non-Abelian topological vortices in condensed matter physics, whose topological flux quantum number is described by $π_2(S^2)$, not by $π_1(S^1)$. We present two examples, a magnetic vortex in two-gap superconductor and a vorticity vortex in two-component Bose-Einstein condensate. In both cases the condensates exhibit a global SU(2) symmetry which allows the non-Abelian topology. We establish the non-Abelian flux quantization in two-gap superconductor by demonstrating the existence of non-Abelian magnetic vortex whose flux is quantized in the unit $4π/g$, not $2π/g$. We also discuss a genuine non-Abelian gauge theory of superconductivity which has a local SU(2) gauge symmetry, and establish the non-Abelian Meissner effect in the non-Abelian superconductor. We compare the non-Abelian vortices with the well-known Abelian Abrikosov vortex, and discuss how these non-Abelian vortices could be observed experimentally in two-gap superconductor made of ${\rm MgB_2}$ and spin-1/2 condensate of $^{87}{\rm Rb}$ atoms. Finally, we argue that the existence of the non-Abelian vortices provides a strong evidence for the existence of topological knots in these condensed matters whose topology is fixed by $π_3(S^2)$, which one can construct by twisting and connecting the periodic ends of the non-Abelian vortices.

cond-mat.supr-con↗

arXiv2005

A Stable Magnetic Background in SU(2) QCD

Motivated by the instability of the Savvidy-Nielsen-Olesen (SNO) vacuum we make a systematic search for a stable magnetic background in pure SU(2) QCD. It is shown that Wu-Yang monopole-antimonopole pair is unstable under vacuum fluctuations. However, it is shown that a pair of axially symmetric monopole-antimonopole string configuration is stable, provided the distance between the two strings is small enough (less than a critical value). The existence of a stable monopole-antimonopole string background strongly supports that a magnetic condensation of monopole-antimonopole pairs can indeed generate a dynamical symmetry breaking, and thus a desired magnetic confinement of color, in QCD.

hep-th↗

arXiv2005

Topological Objects in Two-component Bose-Einstein Condensates

We study the topological objects in two-component Bose-Einstein condensates. We compare two competing theories of two-component Bose-Einstein condensate, the popular Gross-Pitaevskii theory and the recently proposed gauge theory of two-component Bose-Einstein condensate which has an induced vorticity interaction. We show that two theories produce very similar topological objects, in spite of the obvious differences in dynamics. Furthermore we show that the gauge theory of two-component Bose-Einstein condensate, with the U(1) gauge symmetry, is remarkably similar to the Skyrme theory. Just like the Skyrme theory the theory admits the non-Abelian vortex, the helical vortex, and the vorticity knot. We construct the lightest knot solution in two-component Bose-Einstein condensate numerically, and discuss how the knot can be constructed in the spin-1/2 condensate of $^{87}{\rm Rb}$ atoms.

cond-mat.other↗

arXiv2005

Stable Monopole-Antimonopole String Background in SU(2) QCD

Motivated by the instability of the Savvidy-Nielsen-Olesen vacuum we make a systematic search for a stable magnetic background in pure SU(2) QCD. It is shown that a pair of axially symmetric monopole and antimonopole strings is stable, provided that the distance between the two strings is less than a critical value. The existence of a stable monopole-antimonopole string background strongly supports that a magnetic condensation of monopole-antimonopole pairs can generate a dynamical symmetry breaking, and thus the magnetic confinement of color in QCD.

hep-th↗

arXiv2004

Color Reflection Invariance and Monopole Condensation in QCD

We review the quantum instability of the Savvidy-Nielsen-Olesen (SNO) vacuum of the one-loop effective action of SU(2) QCD, and point out a critical defect in the calculation of the functional determinant of the gluon loop in the SNO effective action. We prove that the gauge invariance, in particular the color reflection invariance, exclude the unstable tachyonic modes from the gluon loop integral. This guarantees the stability of the magnetic condensation in QCD.

hep-th↗

arXiv2004

Vorticity Knot in Two-component Bose-Einstein Condensates

We demonstrate the existence of the helical vortex solution in two-component Bose-Einstein condensates which can be identified as a twisted vorticity flux. Based on this we argue that the recently proposed knot in two-component Bose-Einstein condensates can be interpreted as a vorticity knot, a vortex ring made of the helical vortex. This picture shows that the knot is made of two quantized vorticity fluxes linked together, whose topology $π_3(S^2)$ is fixed by the linking number of two vorticity fluxes. Due to the helical structure the knot has both topological and dynamical stability. We estimate the energy of the lightest knot to be about $3\times 10^{-3} eV$.

cond-mat.other↗

arXiv2004

Stability of Monopole Condensation in SU(2) QCD

We propose to resolve the controversy regarding the stability of the monopole condensation in QCD by calculating the imaginary part of the one-loop effective action perturbatively. We calculate the imaginary part perturbatively to the order $g^2$ with two different methods, with Fyenman diagram and with Schwinger's method. Our result shows that with the magnetic background the effective action has no imaginary part, but with the electric background it acquires a negative imaginary part. This strongly indicates a stable monopole condensation in QCD.

hep-th↗

arXiv2004

Gauge Invariance and Stability of SNO vacuum in QCD

We point out a critical defect in the calculation of the functional determinant of the gluon loop in the Savvidy-Nielsen-Olesen (SNO) effective action. We prove that the gauge invariance naturally exclude the unstable tachyonic modes from the gluon loop integral. This guarantees the stability of the magnetic condensation in QCD.

hep-th↗

arXiv2004

Reinterpretation of Faddeev-Niemi Knot in Skyrme Theory

We identify the Faddeev-Niemi knot in Skyrme theory as a vortex ring made of a helical baby skyrmion (a twisted chromomagnetic vortex which is periodic in $z$-coodinate) with the periodic ends connected together. This allows us to interpret the knot as two quantized magnetic flux rings linked together, the first one winding the second $m$ times and the second one winding the first $n$ times, whose linking number $mn$ is fixed by the Chern-Simon index of the magnetic potential. This interpretation strongly suggests that the Skyrme theory could also describe a very interesting low energy physics in a completely different environment, which puts the theory in a totally new perspective.

nucl-th↗

arXiv2004

Chromoelectric Knot in QCD

We argue that the Skyrme theory describes the chromomagnetic (not chromoelectric) dynamics of QCD. This shows that the Skyrme theory could more properly be interpreted as an effective theory which is dual to QCD, rather than an effective theory of QCD itself. This leads us to predict the existence of a new type of topological knot, a twisted chromoelectric flux ring, in QCD which is dual to the chromomagnetic Faddeev-Niemi knot in Skyrme theory. We estimate the mass and the decay width of the lightest chromoelectric knot to be around $50 GeV$ and $117 MeV$.

hep-th↗

arXiv2004

Knot Topology of QCD Vacuum

We show that one can express the knot equation of Skyrme theory completely in terms of the vacuum potential of SU(2) QCD, in such a way that the equation is viewed as a generalized Lorentz gauge condition which selects one vacuum for each class of topologically equivalent vacua. From this we show that there are three ways to describe the QCD vacuum (and thus the knot), by a non-linear sigma field, a complex vector field, or by an Abelian gauge potential. This tells that the QCD vacuum can be classified by an Abelian gauge potential with an Abelian Chern-Simon index.

hep-th↗

arXiv2004

Monopole Condensation and Dimensional Transmutation in SU(2) QCD

We resolve the controversy on the stability of the monopole condensation in the one-loop effective action of SU(2) QCD by calculating the imaginary part of the effective action with two different methods at one-loop order. Our result confirms that the effective action for the magnetic background has no imaginary part but the one for the electric background has a negative imaginary part. This assures that the monopole condensation is indeed stable, but the electric background becomes unstable due to the pair-annihilation of gluons.

hep-th↗