2,925 research outputs found
Color Confinement and Massive Gluons
Color confinement is one of the central issues in QCD so that there are
various interpretations of this feature. In this paper we have adopted the
interpretation that colored particles are not subject to observation just
because colored states are unphysical in the sense of Eq. (2.16). It is shown
that there are two phases in QCD distinguished by different choices of the
gauge parameter. In one phase, called the "confinement phase", color
confinement is realized and gluons turn out to be massive. In the other phase,
called the "deconfinement phase", color confinement is not realized, but the
gluons remain massless.Comment: 14 page
Noncommutative Quantum Field Theory: A Confrontation of Symmetries
The concept of a noncommutative field is formulated based on the interplay
between twisted Poincar\'e symmetry and residual symmetry of the Lorentz group.
Various general dynamical results supporting this construction, such as the
light-wedge causality condition and the integrability condition for
Tomonaga-Schwinger equation, are presented. Based on this analysis, the claim
of the identity between commutative QFT and noncommutative QFT with twisted
Poincar\'e symmetry is refuted.Comment: 20 page
No confinement without Coulomb confinement
We compare the physical potential of an external quark-antiquark
pair in the representation of SU(N), to the color-Coulomb potential which is the instantaneous part of the 44-component of the gluon
propagator in Coulomb gauge, D_{44}(\vx,t) = V_{\rm coul}(|\vx|) \delta(t) +
(non-instantaneous). We show that if is confining, , then the inequality holds asymptotically at large , where is the Casimir in
the representation . This implies that is also
confining.Comment: 9 page
Renormalization Constant of the Color Gauge Field as a Probe of Confinement
The mechanism of color confinement as a consequence of an unbroken
non-abelian gauge symmetry and asymptotic freedom is elucidated and compared
with that of other models based on an analogy with the type II superconductor.
It is demonstrated that a sufficient condition for color confinement is given
by where denotes the renormalization constant of the color
gauge field. It is shown that this condition is actually satisfied in quantum
chromodynamics and that some of the characteristic features of other models
follow from it.Comment: 34 pages, Latex, v2 - 2 appendices adde
Significantly enhanced critical current densities in MgB2 tapes made by a scaleable, nano-carbon addition route
Nanocarbon-doped Fe-sheathed MgB2 tapes with different doping levels were
prepared by the in situ powder-in-tube method. Compared to the undoped tapes,
Jc for all the C-doped samples was enhanced by more than an order of magnitude
in magnetic fields above 9 T. At 4.2 K, the transport Jc for the 5 at% doped
tapes reached 1.85x104 A/cm2 at 10 T and 2.8x103 A/cm2 at 14 T, respectively.
Moreover, the critical temperature for the doped tapes decreased slightly.
Transmission electron microscopy showed a number of intra-granular dislocations
and the dispersed nanoparticles embedded within MgB2 grains induced by the C
doping. The mechanism for the enhancement of flux pinning is also discussed.
These results indicate that powder-in-tube-processed MgB2 tape is very
promising for high-field applications.Comment: 13 pages, 5 figures. to be published soo
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