1,065 research outputs found
Calculation of the Regularized Vacuum Energy in Cavity Field Theories
A novel technique based on Schwinger's proper time method is applied to the
Casimir problem of the M.I.T. bag model. Calculations of the regularized vacuum
energies of massless scalar and Dirac spinor fields confined to a static and
spherical cavity are presented in a consistent manner. While our results agree
partly with previous calculations based on asymptotic methods, the main
advantage of our technique is that the numerical errors are under control.
Interpreting the bag constant as a vacuum expectation value, we investigate
potential cancellations of boundary divergences between the canonical energy
and its bag constant counterpart in the fermionic case. It is found that such
cancellations do not occur.Comment: 14 pages, 4 figures, accepted for publication in Eur.Phys.J.
Dark matter concentration in the galactic center
It is shown that the matter concentration observed through stellar motion at
the galactic center (Eckart & Genzel, 1997, MNRAS, 284, 576 and Genzel et al.,
1996, ApJ, 472, 153) is consistent with a supermassive object of solar masses composed of self-gravitating, degenerate heavy neutrinos, as
an alternative to the black hole interpretation. According to the observational
data, the lower bounds on possible neutrino masses are
keV for or keV for , where is the
spin degeneracy factor. The advantage of this scenario is that it could
naturally explain the low X-ray and gamma ray activity of Sgr A, i.e. the
so called "blackness problem" of the galactic center.Comment: ApJ, 500, 591 (1998), AASTEX, aasms4.sty, v2 reference adde
Cosmological k-essence condensation
We consider a model of dark energy/matter unification based on a k-essence
type of theory similar to tachyon condensate models. Using an extension of the
general relativistic spherical model which incorporates the effects of both
pressure and the acoustic horizon we show that an initially perturbative
k-essence fluid evolves into a mixed system containing cold dark matter like
gravitational condensate in significant quantities.Comment: 8 pages, 2 figures, presented by NB at the conference Beyond 2010,
Cape Town, 1-6 February 201
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