12 research outputs found
Stability Conditions For a Noncommutative Scalar Field Coupled to Gravity via the Positive Energy Theorem
The stability requirements for a noncommutative scalar field coupled to
gravity is investigated through the positive energy theorem. It is shown that
for a noncommutative scalar with a polynomial potential, the stability
conditions are similar to the ones for the commutative case. This result
remains valid even whether the space-time has horizons.Comment: 6 pages. Talk presented by C. Z. at the "Invisible Universe
International Conference", Paris, Palais de l'UNESCO, June 29- July 3. To
appear in the Proceeding
Vanishing DC holographic conductivity from a magnetic monopole condensate
We show how to obtain a vanishing DC conductivity in 3-dimensional strongly
coupled QFT's using a massive 2-form field in the bulk that satisfies a special
kind of boundary condition. The real and imaginary parts of the AC conductivity
are evaluated in this holographic setup and we show that the DC conductivity
identically vanishes even for an arbitrarily small (though nonzero) value of
the 2-form mass in the bulk. We identify the bulk action of the massive 2-form
with an effective theory describing a phase in which magnetic monopoles have
condensed in the bulk. Our results indicate that a condensate of magnetic
monopoles in a 4-dimensional bulk leads to a vanishing DC holographic
conductivity in 3-dimensional strongly coupled QFT's.Comment: 24 pages, 2 figures, accepted for publication in JHE
Noncommutative effects in astrophysical objects: a survey
The main implications of noncommutativity over astrophysical objects are
examined. Noncommutativity is introduced through a deformed dispersion relation
and the relevant
thermodynamical quantities are calculated using the grand canonical ensemble
formalism. These results are applied to simple physical models describing
main-sequence stars, white-dwarfs and neutron stars. The stability of
main-sequence stars and white dwarfs is discussed.Comment: 10 pages. Talk presented by C. Z. at the "First Mediterranean
Conference on Classical and Quantum Gravity", Kolymbari (Crete, Greece),
September 14-18, 2009. To appear in the Proceeding
Towards a Noncommutative Astrophysics
We consider astrophysical objects such as main-sequence stars, white-dwarfs
and neutron stars in a noncommutative context. Noncommutativity is implemented
via a deformed dispersion relation from which we obtain noncommutative corrections to the
pressure, particle number and energy densities for radiation and for a
degenerate fermion gas. The main implications of noncommutativity for the
considered astrophysical objects are examined and discussed.Comment: Version to match the Physical Review D on