208 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
Vacuum structure of a modified MIT Bag
An alternative to introducing and subsequently renormalizing classical
parameters in the expression for the vacuum energy of the MIT bag for quarks is
proposed in the massless case by appealing to the QCD trace anomaly and scale
separation due to asymptotic freedom. The explicit inclusion of gluons implies
an unrealistically low separation scale.Comment: 5 pages, 2 figure
Hadron masses in cavity quantum chromodynamics to order
The non-divergent diagrams describing two-gluon exchange and annihilation
between quarks and antiquarks are calculated in the Feynman gauge, based on
quantum chromodynamics in a spherical cavity. Using the experimental ,
, , and masses to fit the free parameters of the M.I.T.\
bag model, the predicted states agree very well with the observed low-lying
hadrons. As expected, the two-gluon annihilation graphs lift the degeneracy of
the and , while the and remain degenerate.
Diagonalizing the subspace Hamiltonian yields a very good value
for the mass of the meson.Comment: 15 pages, 2 figure
Sgr A^*: A supermassive black hole or a spatially extended object?
We report here on a calculation of possible orbits of the fast moving
infrared source S1 which has been recently observed by Eckart and Genzel (1997)
near the Galactic center. It is shown that tracking of the orbit of S1 or any
other fast moving star near Sgr A^* offers a possibility of distinguishing
between the supermassive black hole and extended object scenarios of Sgr A^*.
In our calculations we assumed that the extended object at the Galactic center
is a non-baryonic ball made of degenerate, self-gravitating heavy neutrino
matter, as it has been recently proposed by Tsiklauri & Viollier (1998a,b).Comment: AASTEX, 5 postscript figs., submitted to ApJ Let
Gauging the Shadow Sector with SO(3)
We examine the phenomenology of a low-energy extension of the Standard Model,
based on the gauge group SU(3) x SU(2) x U(1) x SO(3), with SO(3) operating in
the shadow sector. This model offers and oscillations as the solution of the solar and atmospheric neutrino
problems. Moreover, it provides a neutral heavy shadow lepton X that could play
the role of a cold dark matter particle.Comment: 8 page
Chaplygin Gas Cosmology - Unification of Dark Matter and Dark Energy
The models that unify dark matter and dark energy based upon the Chaplygin
gas fail owing to the suppression of structure formation by the adiabatic speed
of sound. Including string theory effects, in particular the Kalb-Ramond field,
we show how nonadiabatic perturbations allow a successful structure formation.Comment: 7 pages, presented by N. B. at IRGAC 2006, Barcelona, 11-15 July
2006, typos corrected, concluding paragraph slightly expanded, final version,
accepted in J. Phys. A, special issu
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