35,959 research outputs found
Effective QFT and what it tells us about dynamical torsion
The covariantly constant spacetime torsion is one of the fields which may
break Lorentz and CPT symmetry. We review the previous works on the dynamical
torsion in the framework of effective quantum field theory (QFT). It turns out
that the existence of propagating torsion is strongly restricted by the QFT
principles. In particular, the torsion mass must be much greater than the
masses of all fermionic particles. In this situation, the main chance to
observe torsion is due to some symmetry breaking which may, in principle,
produce almost constant background torsion field.Comment: 5 pages, Accepted for publication in the Proceedings of the Fifth
Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, U.S.A., June
28-July 2, 201
Renormalization in QED and QFT with a Lorentz- and CPT-violating backgrounds
The general features of renormalization and the renormalization group in QED
and in general quantum field theories in curved spacetime with additional
Lorentz- and CPT-violating background fields are reviewed.Comment: 4 pages, WS styles, Presented at the Sixth Meeting on CPT and Lorentz
Symmetry,Bloomington, Indiana, June 17-21, 201
Relativistic Collapse of Rotating Supermassive Stars to Supermassive Black Holes
There is compelling evidence that supermassive black holes (SMBHs) exist. Yet
the origin of these objects, or their seeds, is still unknown. We are
performing general relativistic simulations of gravitational collapse to black
holes in different scenarios to help reveal how SMBH seeds might arise in the
universe. SMBHs with ~ 10^9 solar masses must have formed by z > 6, or within
10^9 yrs after the Big Bang, to power quasars. It may be difficult for gas
accretion to build up such a SMBH by this time unless the initial seed black
hole already has a substantial mass. One plausible progenitor of a massive seed
black hole is a supermassive star (SMS). We have followed the collapse of a SMS
to a SMBH by means of 3D hydrodynamic simulations in post-Newtonian gravity and
axisymmetric simulations in full general relativity. The initial SMS of
arbitrary mass M in these simulations rotates uniformly at the mass--shedding
limit and is marginally unstable to radial collapse. The final black hole mass
and spin are determined to be M_h/M ~ 0.9 and J_h/M_h^2 ~ 0.75. The remaining
mass goes into a disk of mass M_{disk}/M ~ 0.1. This disk arises even though
the total spin of the progenitor star, J/M^2 = 0.97, is safely below the Kerr
limit. The collapse generates a mild burst of gravitational radiation.
Nonaxisymmetric bars or one-armed spirals may arise during the quasi-stationary
evolution of a SMS, during its collapse, or in the ambient disk about the hole,
and are potential sources of quasi-periodic waves, detectable by LISA.Comment: 11 pages, to appear in "The Astrophysics of Gravitational Wave
Sources", Proceedings of a Workshop held at the University of Maryland in
April 2003, ed. J. Centrella, AIP, in pres
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