808,993 research outputs found
Self-gravitating stringlike configurations from nonlinear electodynamics
We consider static, cylindrically symmetric configurations in general
relativity coupled to nonlinear electrodynamics (NED) with an arbitrary
gauge-invariant Lagrangian of the form , . We
study electric and magnetic fields with three possible orientations: radial
(R), longitudinal (L) and azimuthal (A), and try to find solitonic stringlike
solutions, having a regular axis and a flat metric at large , with a
possible angular defect. Assuming the function to be regular at small
, it is shown that a regular axis is impossible in R-fields if there is a
nonzero effective electric charge and in A-fields if there is a nonzero
effective electric current along the axis. Solitonic solutions are only
possible for purely magnetic R-fields and purely electric A-fields, in cases
when tends to a finite limit at large . For both R- and A-fields,
the desired large asymptotic is only possible with a non- Maxwell behaviour
of at small . For L-fields, solutions with a regular axis are
easily obtained (and can be found by quadratures) whereas a desired large
asymptotic is only possible in an exceptional solution; the latter gives rise
to solitonic configurations in case \Phi(F) = \const \cdot \sqrt{F}. We give
an explicit example of such a solution.Comment: 7 pages, Latex-2e,gc.sty, to appear in Grav. & Cosmo
Possible eta-mesic 3He states within the finite rank approximation
We extend the method of time delay proposed by Eisenbud and Wigner, to search
for unstable states formed by eta mesons and the 3He nucleus. Using few body
equations to describe eta-3He elastic scattering, we predict resonances and
unstable bound states within different models of the eta-N interaction. The
eta-3He states predicted within this novel approach are in agreement with the
recent claim of the evidence of eta-mesic 3He made by the TAPS collaboration.Comment: 10 pages LaTex, 3 figure
Catalysis of chiral symmetry breaking by external magnetic fields in three-dimensional lattice QED
The enhancement of the fermionic condensate due to the presence of both
homogeneous and non-homogeneous external magnetic fields is studied for
three-dimensional QED.Comment: 5 pages, contribution to "Strong and electroweak matter 98",
Copenhagen, December 199
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