178 research outputs found
Causal Structure of Vacuum Solutions to Conformal(Weyl) Gravity
Using Penrose diagrams the causal structure of the static spherically
symmetric vacuum solution to conformal (Weyl) gravity is investigated. A
striking aspect of the solution is an unexpected physical singularity at
caused by a linear term in the metric. We explain how to calculate the
deflection of light in coordinates where the metric is manifestly conformal to
flat i.e. in coordinates where light moves in straight lines.Comment: 18 pages, 2 figures, title and abstract changed, contents essentially
unaltered accepted for publication in General Relativity and Gravitatio
A new duality transformation for fourth-order gravity
We prove that for non-linear L = L(R), the Lagrangians L and \hat L give
conformally equivalent fourth-order field equations being dual to each other.
The proof represents a new application of the fact that the operator
is conformally invariant.Comment: 11 pages, LaTeX, no figures. Gen. Relat. Grav. in prin
Local and global gravity
Our long experience with Newtonian potentials has inured us to the view that
gravity only produces local effects. In this paper we challenge this quite
deeply ingrained notion and explicitly identify some intrinsically global
gravitational effects. In particular we show that the global cosmological
Hubble flow can actually modify the motions of stars and gas within individual
galaxies, and even do so in a way which can apparently eliminate the need for
galactic dark matter. Also we show that a classical light wave acquires an
observable, global, path dependent phase in traversing a gravitational field.
Both of these effects serve to underscore the intrinsic difference between
non-relativistic and relativistic gravity.Comment: LaTeX, 20 pages plus three figures in two postscript files. To appear
in a special issue of Foundations of Physics honoring Professor Lawrence
Horwitz on the occasion of his 65th birthday; A. van der Merwe and S. Raby,
Editors, Plenum Publishing Company, N.Y., 199
Quantum Diffeomorphisms and Conformal Symmetry
We analyze the constraints of general coordinate invariance for quantum
theories possessing conformal symmetry in four dimensions. The character of
these constraints simplifies enormously on the Einstein universe . The global conformal symmetry algebra of this space determines
uniquely a finite shift in the Hamiltonian constraint from its classical value.
In other words, the global Wheeler-De Witt equation is {\it modified} at the
quantum level in a well-defined way in this case. We argue that the higher
moments of should not be imposed on the physical states {\it a priori}
either, but only the weaker condition . We
present an explicit example of the quantization and diffeomorphism constraints
on for a free conformal scalar field.Comment: PlainTeX File, 37 page
Thermodynamics of Quantum Fields in Black Hole Backgrounds
We discuss the relation between the micro-canonical and the canonical
ensemble for black holes, and highlight some problems associated with extreme
black holes already at the classical level. Then we discuss the contribution of
quantum fields and demonstrate that the partition functions for scalar and
Dirac (Majorana) fields in static space-time backgrounds, can be expressed as
functional integrals in the corresponding optical space, and point out that the
difference between this and the functional integrals in the original metric is
a Liouville-type action. The optical method gives both the correction to the
black hole entropy and the bulk contribution to the entropy due to the
radiation, while (if the Liouville term is ignored) the conical singularity
method just gives the divergent contribution to the black hole entropy. A
simple derivation of a general formula for the free energy in the
high-temperature approximation is given and applied to various cases. We
conclude with a discussion of the second law.Comment: 26 pages, latex, no figures. References added, minor error correcte
Functional characterization of two PLP-dependent enzymes involved in capsular polysaccharide biosynthesis from campylobacter jejuni
Campylobacter jejuni is a Gram-negative, pathogenic bacterium that causes campylobacteriosis, a form of gastroenteritis. C. jejuni is the most frequent cause of food-borne illness in the world, surpassing Salmonella and E. coli. Coating the surface of C. jejuni is a layer of sugar molecules known as the capsular polysaccharide that, in C. jejuni NCTC 11168, is composed of a repeating unit of d-glycero-l-gluco-heptose, d-glucuronic acid, d-N-acetyl-galactosamine, and d-ribose. The d-glucuronic acid moiety is further amidated with either serinol or ethanolamine. It is unknown how these modifications are synthesized and attached to the polysaccharide. Here, we report the catalytic activities of two previously uncharacterized, pyridoxal phosphate (PLP)-dependent enzymes, Cj1436 and Cj1437, from C. jejuni NCTC 11168. Using a combination of mass spectrometry and nuclear magnetic resonance, we determined that Cj1436 catalyzes the decarboxylation of l-serine phosphate to ethanolamine phosphate. Cj1437 was shown to catalyze the transamination of dihydroxyacetone phosphate to (S)-serinol phosphate in the presence of l-glutamate. The probable routes to the ultimate formation of the glucuronamide substructures in the capsular polysaccharides of C. jejuni are discussed
Graviton Vertices and the Mapping of Anomalous Correlators to Momentum Space for a General Conformal Field Theory
We investigate the mapping of conformal correlators and of their anomalies
from configuration to momentum space for general dimensions, focusing on the
anomalous correlators , - involving the energy-momentum tensor
with a vector or a scalar operator () - and the 3-graviton vertex
. We compute the , and one-loop vertex functions in
dimensional regularization for free field theories involving conformal scalar,
fermion and vector fields. Since there are only one or two independent tensor
structures solving all the conformal Ward identities for the or
vertex functions respectively, and three independent tensor structures for the
vertex, and the coefficients of these tensors are known for free fields,
it is possible to identify the corresponding tensors in momentum space from the
computation of the correlators for free fields. This works in general
dimensions for and correlators, but only in 4 dimensions for ,
since vector fields are conformal only in . In this way the general
solution of the Ward identities including anomalous ones for these correlators
in (Euclidean) position space, found by Osborn and Petkou is mapped to the
ordinary diagrammatic one in momentum space. We give simplified expressions of
all these correlators in configuration space which are explicitly Fourier
integrable and provide a diagrammatic interpretation of all the contact terms
arising when two or more of the points coincide. We discuss how the anomalies
arise in each approach [...]Comment: 57 pages, 7 figures. Refs adde
Logarithmic correction to BH entropy as Noether charge
We consider the role of the type-A trace anomaly in static black hole
solutions to semiclassical Einstein equation in four dimensions. Via Wald's
Noether charge formalism, we compute the contribution to the entropy coming
from the anomaly induced effective action and unveil a logarithmic correction
to the Bekenstein-Hawking area law.
The corrected entropy is given by a seemingly universal formula involving the
coefficient of the type-A trace anomaly, the Euler characteristic of the
horizon and the value at the horizon of the solution to the uniformization
problem for Q-curvature. Two instances are examined in detail: Schwarzschild
and a four-dimensional massless topological black hole. We also find agreement
with the logarithmic correction due to one-loop contribution of conformal
fields in the Schwarzschild background.Comment: 14 pages, JHEP styl
A Field-theoretical Interpretation of the Holographic Renormalization Group
A quantum-field theoretical interpretation is given to the holographic RG
equation by relating it to a field-theoretical local RG equation which
determines how Weyl invariance is broken in a quantized field theory. Using
this approach we determine the relation between the holographic C theorem and
the C theorem in two-dimensional quantum field theory which relies on the
Zamolodchikov metric. Similarly we discuss how in four dimensions the
holographic C function is related to a conjectured field-theoretical C
function. The scheme dependence of the holographic RG due to the possible
presence of finite local counterterms is discussed in detail, as well as its
implications for the holographic C function. We also discuss issues special to
the situation when mass deformations are present. Furthermore we suggest that
the holographic RG equation may also be obtained from a bulk diffeomorphism
which reduces to a Weyl transformation on the boundary.Comment: 24 pages, LaTeX, no figures; references added, typos corrected,
paragraph added to section
Mass and Gauge Invariance IV (Holography for the Karch-Randall Model)
We argue that the Karch-Randall compactification is holographically dual to a
4-d conformal field theory coupled to gravity on Anti de Sitter space. Using
this interpretation we recover the mass spectrum of the model. In particular,
we find no massless spin-2 states. By giving a purely 4-d interpretation to the
compactification we make clear that it represents the first example of a local
4-d field theory in which general covariance does not imply the existence of a
massless graviton. We also discuss some variations of the Karch-Randall model
discussed in the literature, and we examine whether its properties are generic
to all conformal field theory.Comment: 26 pages, uses package latexsym. Note added in proo
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