72,027 research outputs found
Equivalence of the Beta-function of the Variational Approach to that of QCD
The variational ansatz for the ground state wavefunctional of QCD is found to
capture the anti-screening behaviour that contributes the dominant `-4' to the
beta-function and leads to asymptotic freedom. By considering an SU(N) purely
gauge theory in the Hamiltonian formalism and choosing the Coulomb gauge, the
origins of all screening and anti-screening contributions in gluon processes
are found in terms of the physical degrees of freedom. The overwhelming anti-
screening contribution of `-4' is seen to originate in the renormalisation of a
Coulomb interaction by a transverse gluon. The lesser screening contribution of
`1/3' is seen to originate in processes involving transverse gluon
interactions. It is thus apparent how the variational ansatz must be developed
to capture the full running of the QCD coupling constant.Comment: 35 pages, 11 figures, LaTe
Giant dispersion of critical currents in superconductor with fractal clusters of a normal phase
The influence of fractal clusters of a normal phase on the dynamics of a
magnetic flux trapped in a percolative superconductor is considered. The
critical current distribution and the current-voltage characteristics of
fractal superconducting structures in the resistive state are obtained for an
arbitrary fractal dimension of the cluster boundaries. The range of fractal
dimensions, where the dispersion of critical currents becomes infinite, is
found. It is revealed that the fractality of clusters depresses of the electric
field caused by the magnetic flux motion thus increasing the critical current
value. It is expected that the maximum current-carrying capability of a
superconductor can be achieved in the region of giant dispersion of critical
currents.Comment: 7 pages with 3 figure
Higher Descent Data as a Homotopy Limit
We define the 2-groupoid of descent data assigned to a cosimplicial
2-groupoid and present it as the homotopy limit of the cosimplicial space
gotten after applying the 2-nerve in each cosimplicial degree. This can be
applied also to the case of -groupoids thus providing an analogous
presentation of "descent data" in higher dimensions.Comment: Appeared in JHR
Macroscopic amplification of electroweak effects in molecular Bose-Einstein condensates
We investigate the possible use of Bose-Einstein condensates of diatomic
molecules to measure nuclear spin-dependent parity violation effects, outlining
a detection method based on the internal Josephson effect between molecular
states of opposite parity. When applied to molecular condensates, the fine
experimental control achieved in atomic bosonic Josephson junctions could
provide data on anapole moments and neutral weak couplings.Comment: 5 pages. To be published Phys. Rev. A (Rapid Communication) (2012
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