1,801 research outputs found
Supersymmetric Nambu-Jona-Lasinio Model in an External Gravitational Field
We investigate the effect of an external gravitational fields to the chiral
symmetry breaking in the SUSY (supersymmetric) NJL (Nambu-Jona-Lasinio) model
non-minimally interacting with external supergravity. Evaluating the effective
potential in the leading order of the -expansion and in the linear
curvature approximation it is found the possibility of the chiral symmetry
breaking in the SUSY NJL model in an external gravitational fields. In the
broken phase the dynamically generated mass is analytically and numerically
calculated.Comment: 8 pages, Latex, epic.sty and eepic.sty are use
epsilon'/epsilon in the Standard Model
In order to provide an estimate of eps'/eps several effective theories and
physical effects have to be disentangled. In this talk I discuss how it is
possible to predict eps '/eps taking into account all sources of large logs.
The numerical result one obtains, \eps '/\eps \sim (1.7\pm 0.6) \cdot
10^{-4}, is in good agreement with present measurements.Comment: Talk presented at QCD2000, Montpellier july 200
Metric Perturbation Approach to Gravitational Waves in Isotropic Cosmologies
Gravitational waves in isotropic cosmologies were recently studied using the
gauge-invariant approach of Ellis-Bruni. We now construct the linearised metric
perturbations of the background Robertson-Walker space-time which reproduce the
results obtained in that study. The analysis carried out here also facilitates
an easy comparison with Bardeen.Comment: 29 pages, Latex file, accepted for publication in Physical Review
Life inside black holes
We consider test planet and photon orbits of the third kind inside a black
hole, which are stable, periodic and neither come out of the black hole nor
terminate at the singularity. Interiors of supermassive black holes may be
inhabited by advanced civilizations living on planets with the third-kind
orbits. In principle, one can get information from the interiors of black holes
by observing their white hole counterparts.Comment: 4 pages, 2 figure
Anomalous Chiral Behavior in Quenched Lattice QCD
A study of the chiral behavior of pseudoscalar masses and decay constants is
carried out in quenched lattice QCD with Wilson fermions. Using the modified
quenched approximation (MQA) to cure the exceptional configuration problem,
accurate results are obtained for pion masses as low as 200 MeV. The
anomalous chiral log effect associated with quenched loops is studied
in both the relation between vs. and in the light-mass
behavior of the pseudoscalar and axial vector matrix elements. The size of
these effects agrees quantitatively with a direct measurement of the
hairpin graph, as well as with a measurement of the topological susceptibility,
thus providing several independent and quantitatively consistent determinations
of the quenched chiral log parameter . For with
clover-improved fermions all results are consistent with
.Comment: 51 pages, 20 figures, Late
Bernoulli potential in type-I and weak type-II superconductors: III. Electrostatic potential above the vortex lattice
The electrostatic potential above the Abrikosov vortex lattice, discussed
earlier by Blatter {\em et al.} {[}PRL {\bf 77}, 566 (1996){]}, is evaluated
within the Ginzburg-Landau theory. Unlike previous studies we include the
surface dipole. Close to the critical temperature, the surface dipole reduces
the electrostatic potential to values below a sensitivity of recent sensors. At
low temperatures the surface dipole is less effective and the electrostatic
potential remains observable as predicted earlier.Comment: 8 pages 5 figure
Normal metal to ferromagnetic superconductor tunneling
We study the point-contact tunneling between normal metal and ferromagnetic
superconductor. In the case of magnon-induced pairing the tunneling conductance
is continuous and smooth function of the applied voltage. For small values of
the applied voltage the Ohm law holds. We show that one can obtain the
magnetization and the superconducting order parameter from the tunneling
conduc- tance. In the case of paramagnon-induced superconductivity the
tunneling does not depend on the magnetization. We argue that tunneling
experiment can unambiguously determine the correct pairing mechanism in the
ferromagnetic superconductors.Comment: 6 pages, 4 figur
Decay properties of new D-mesons
We consider radiative and pionic decays of the new D_s-mesons in the
framework of a phenomenologically motivated approach. Present data on ratios of
the two kinds of decays can be described without explicit using a 4-quark
component. Most probably, the isospin violation in decays of different
D_s-mesons is not universal, and the binding potential should be different from
Coulombic. New precise measurements may provide further clarification for the
nature of the D_s excited states.Comment: 12 pages, Late
Folded Strings Falling into a Black Hole
We find all the classical solutions (minimal surfaces) of open or closed
strings in {\it any} two dimensional curved spacetime. As examples we consider
the SL(2,R)/R two dimensional black hole, and any 4D black hole in the
Schwarzschild family, provided the motion is restricted to the time-radial
components. The solutions, which describe longitudinaly oscillating folded
strings (radial oscillations in 4D), must be given in lattice-like patches of
the worldsheet, and a transfer operation analogous to a transfer matrix
determines the future evolution. Then the swallowing of a string by a black
hole is analyzed. We find several new features that are not shared by particle
motions. The most surprizing effect is the tunneling of the string into the
bare singularity region that lies beyond the black hole that is classically
forbidden to particles.Comment: 28 pages plus 4 figures, LaTeX, USC-94/HEP-B
Regularization-independent study of renormalized non-perturbative quenched QED
A recently proposed regularization-independent method is used for the first
time to solve the renormalized fermion Schwinger-Dyson equation numerically in
quenched QED. The Curtis-Pennington vertex is used to illustrate the
technique and to facilitate comparison with previous calculations which used
the alternative regularization schemes of modified ultraviolet cut-off and
dimensional regularization. Our new results are in excellent numerical
agreement with these, and so we can now conclude with confidence that there is
no residual regularization dependence in these results. Moreover, from a
computational point of view the regularization independent method has enormous
advantages, since all integrals are absolutely convergent by construction, and
so do not mix small and arbitrarily large momentum scales. We analytically
predict power law behaviour in the asymptotic region, which is confirmed
numerically with high precision. The successful demonstration of this efficient
new technique opens the way for studies of unquenched QED to be undertaken in
the near future.Comment: 20 pages,5 figure
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