644 research outputs found
Hawking Radiation for Non-minimally Coupled Matter from Generalized 2D Black Hole Models
It is well known that spherically symmetric reduction of General Relativity
(SSG) leads to non-minimally coupled scalar matter. We generalize (and correct)
recent results to Hawking radiation for a class of dilaton models which share
with the Schwarzschild black hole non-minimal coupling of scalar fields and the
basic global structure. An inherent ambiguity of such models (if they differ
from SSG) is discussed. However, for SSG we obtain the rather disquieting
result of a negative Hawking flux at infinity, if the usual recipe for such
calculations is applied.Comment: 8 page
Comment on: ``Trace anomaly of dilaton coupled scalars in two dimensions''
The trace anomaly for nonminimally coupled scalars in spherically reduced
gravity obtained by Bousso and Hawking (hep-th/9705236) is incorrect. We
explain the reasons for the deviations from our correct (published) result
which is supported by several other recent papers.Comment: 2 page
Wormholes in String Theory
A wormhole is constructed by cutting and joining two spacetimes satisfying
the low energy string equations with a dilaton field. In spacetimes described
by the "string metric" the dilaton energy-momentum tensor need not satisfy the
weak or dominant energy conditions. In the cases considered here the dilaton
field violates these energy conditions and is the source of the exotic matter
required to maintain the wormhole. There is also a surface stress-energy, that
must be produced by additional matter, where the spacetimes are joined. It is
shown that wormholes can be constructed for which this additional matter
satisfies the weak and dominant energy conditions, so that it could be a form
of "normal" matter. Charged dilaton wormholes with a coupling between the
dilaton and the electromagnetic field that is more general than in string
theory are also briefly discussed.Comment: 9 pages, LaTex, submitted to Phys. Rev.
Magnetic polarizability of hadrons from lattice QCD
We extract the magnetic polarizability from the quadratic response of a
hadron's mass shift in progressively small static magnetic fields. The
calculation is done on a 24x12x12x24 lattice at a = 0.17 fm with an improved
gauge action and the clover quark action. The results are compared to those
from experiments and models where available.Comment: 3 pages, 3 figures, contribution to Lattice 2002 (spectrum
Secretion of Streptomyces mobaraensis pro-transglutaminase by coryneform bacteria
We previously reported on the secretion of Streptomyces mobaraensis transglutaminase by Corynebacterium glutamicum ATCC13869 (formerly classified as Brevibacterium lactofermentum). In the present work, we investigated whether any other coryneform bacteria showed higher productivity than C. glutamicum ATCC13869. We found that most coryneform species secreted pro-transglutaminase efficiently. Moreover, we confirmed that Corynebacterium ammoniagenes ATCC6872 produced about 2.5Â g/l pro-transglutaminase over a 71-h period in a jar fermentor. Our findings suggest that some other coryneform bacteria, especially C. ammoniagenes ATCC6872, are potential hosts for industrial scale protein production
Nonperturbative path integral of 2d dilaton gravity and two-loop effects from scalar matter
Performing an nonperturbative path integral for the geometric part of a large
class of 2d theories without kinetic term for the dilaton field, the quantum
effects from scalar matter fields are treated as a perturbation. When
integrated out to two-loops they yield a correction to the Polyakov term which
is still exact in the geometric part. Interestingly enough the effective action
only experiences a renormalization of the dilaton potential.Comment: 15 page
- …