2,397 research outputs found
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
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
14-MeV Neutron Irradiation Effects on Superconducting Magnet Materials under Cryogenic Temperature
Collaboration Network for Investigation on Neutron Irradiation Effect on Superconducting Magnet Materials
Dual Interpretations of Pion Clouds at RHIC
A gauge theory of pions interacting with rho-mesons at elevated temperatures
is used to calculate the pressure in a hot pion gas. No reference is made to
the pion's status as a QCD Goldstone boson. The role of the pion is merely that
of a carrier of an SU(2) symmetry, gauged to create a vector-meson interaction,
the rho playing the role of the interacting vector particle. The results are in
rough agreement with much more elaborate calculations, both of the purely
hadronic variety, and those that invoke quark-gluon degrees of freedom. The
quark-gluon and purely hadronic calculations seemingly lead to very similar
predictions which are in accord with receent data from RHIC. The results
motivate the question as to whether the two descriptions are dual to each other
in the sense of being alternate models, each sufficient to explain the observed
data.Comment: 11 pages, 4 figures (2 eps files, 1 ps file) + a figure that uses
metafont package feynmf, also forwarded. Open with "latex feynmf.ins". See
http://www.ctan.org/tex-archive/help/Catalogue/entries/feynmf.html 9/6/06
replaced figure 2 with scaled version of sam
Duality and Superconvergence Relation in Supersymmetric Gauge Theories
We investigate the phase structures of various N=1 supersymmetric gauge
theories including even the exceptional gauge group from the viewpoint of
superconvergence of the gauge field propagator. Especially we analyze in detail
whether a new type of duality recently discovered by Oehme in gauge
theory coupled to fundamental matter fields can be found in more general gauge
theories with more general matter representations or not. The result is that in
the cases of theories including matter fields in only the fundamental
representation, Oehme's duality holds but otherwise it does not. In the former
case, superconvergence relation might give good criterion to describe the
interacting non-Abelian Coulomb phase without using some information from dual
magnetic theory.Comment: 20 pages, LaTe
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