22,827 research outputs found
Phi meson mass and decay width in nuclear matter
The meson spectrum, which in vacuum is dominated by its coupling to
the system, is modified in nuclear matter. Following a model based
on chiral SU(3) dynamics we calculate the meson selfenergy in nuclear
matter considering the and in-medium properties. For the latter
we use the results of previous calculations which account for and wave
kaon-nucleon interactions based on the lowest order meson-baryon chiral
effective Lagrangian, and this leads to a dressing of the kaon propagators in
the medium. In addition, a set of vertex corrections is evaluated to fulfill
gauge invariance, which involves contact couplings of the meson to
wave and wave kaon-baryon vertices. Within this scheme the mass shift
and decay width of the meson in nuclear matter are studied.Comment: 19 pages, 10 figures in EPS format, revtex4; One section modified,
some references update
Formality of Donaldson submanifolds
We introduce the concept of s-formal minimal model as an extension of
formality. We prove that any orientable compact manifold M, of dimension 2n or
(2n-1), is formal if and only if M is (n-1)-formal. The formality and the hard
Lefschetz property are studied for the symplectic manifolds constructed by
Donaldson with asymptotically holomorphic techniques. This study permits us to
show an example of a Donaldson symplectic manifold of dimension eight which is
formal simply connected and does not satisfy the hard Lefschetz theorem.Comment: 24 pages, no figures, Latex2e; v3. statement of Lemma 2.7 correcte
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