13,165 research outputs found
Chemical potential as a source of stability for gravitating Skyrmions
A discussion of the stability of self gravitating Skyrmions, with a large
winding number N, in a Schwarzschild type of metric, is presented for the case
where an isospin chemical potential is introduced. It turns out that the
chemical potential stabilizes the behavior of the Skyrmion discussed previously
in the literature. This analysis is carried on in the framework of a
variational approach using different ansaetze for the radial profile of the
Skyrmion. We found a divergent behavior for the size of the Skyrmion,
associated to a certain critical value of the chemical potential. At
this point, the mass of the Skyrmion vanishes. is essentialy
independent of gravitating effects. The stability of a large N skyrmion against
decays into single particles is also discussed.Comment: 10 pages, 4 figures Small changes to the previous version and a new
referenc
(Pseudo)Scalar Charmonium in Finite Temperature QCD
The hadronic parameters of pseudoscalar () and scalar ()
charmonium are determined at finite temperature from Hilbert moment QCD sum
rules. These parameters are the hadron mass, leptonic decay constant, total
width, and continuum threshold (). Results for in both channels
indicate that starts approximately constant, and then it decreases
monotonically with increasing until it reaches the QCD threshold, , at a critical temperature T = T_c \simeq 180 \; \mbox{MeV}
interpreted as the deconfinement temperature. The other hadronic parameters
behave qualitatively similarly to those of the , as determined in this
same framework. The hadron mass is essentially constant, the total width is
initially independent of T, and after it begins to increase
with increasing up to for
(), and subsequently it decreases sharply up to , for (), beyond which the sum rules are no
longer valid. The decay constant of at first remains basically flat up
to , then it starts to decrease up to , and finally it increases sharply with increasing . In the case of
the decay constant does not change up to where
it begins a gentle increase up to beyond which it
increases dramatically with increasing . This behaviour contrasts with that
of light-light and heavy-light quark systems, and it suggests the survival of
the and the states beyond the critical temperature, as
already found for the from similar QCD sum rules. These conclusions
are very stable against changes in the critical temperature in the wide range
T_c = 180 - 260 \; \mbox{MeV}.Comment: 12 pages, 5 figures. A wide range of critical temperatures has been
considered. No qualitative changes to the conclusion
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