19,606 research outputs found
Six-dimensional Methods for Four-dimensional Conformal Field Theories
The calculation of both spinor and tensor Green's functions in
four-dimensional conformally invariant field theories can be greatly simplified
by six-dimensional methods. For this purpose, four-dimensional fields are
constructed as projections of fields on the hypercone in six-dimensional
projective space, satisfying certain transversality conditions. In this way
some Green's functions in conformal field theories are shown to have structures
more general than those commonly found by use of the inversion operator. These
methods fit in well with the assumption of AdS/CFT duality. In particular, it
is transparent that if fields on AdS approach finite limits on the boundary
of AdS, then in the conformal field theory on this boundary these limits
transform with conformal dimensionality zero if they are tensors (of any rank),
but with conformal dimension 1/2 if they are spinors or spinor-tensors.Comment: Version accepted for publication in Physical Review D. References to
earlier work added in footnote 2. Minor errors corrected. 24 page
Points of General Relativisitic Shock Wave Interaction are "Regularity Singularities" where Spacetime is Not Locally Flat
We show that the regularity of the gravitational metric tensor in spherically
symmetric spacetimes cannot be lifted from to within the
class of coordinate transformations in a neighborhood of a point of
shock wave interaction in General Relativity, without forcing the determinant
of the metric tensor to vanish at the point of interaction. This is in contrast
to Israel's Theorem which states that such coordinate transformations always
exist in a neighborhood of a point on a smooth single shock surface. The
results thus imply that points of shock wave interaction represent a new kind
of singularity for perfect fluids evolving in spacetime, singularities that
make perfectly good sense physically, that can form from the evolution of
smooth initial data, but at which the spacetime is not locally Minkowskian
under any coordinate transformation. In particular, at such singularities,
delta function sources in the second derivatives of the gravitational metric
tensor exist in all coordinate systems of the atlas, but due to
cancelation, the curvature tensor remains uniformly bounded.Comment: This article has been withdrawn since the main result is wrong due to
an computational error. See arXiv:1506.04081 and arXiv:1409.5060 for a
correction of this error and a proof of the opposite statemen
Constraints on Interacting Scalars in 2T Field Theory and No Scale Models in 1T Field Theory
In this paper I determine the general form of the physical and mathematical
restrictions that arise on the interactions of gravity and scalar fields in the
2T field theory setting, in d+2 dimensions, as well as in the emerging shadows
in d dimensions. These constraints on scalar fields follow from an underlying
Sp(2,R) gauge symmetry in phase space. Determining these general constraints
provides a basis for the construction of 2T supergravity, as well as physical
applications in 1T-field theory, that are discussed briefly here, and more
detail elsewhere. In particular, no scale models that lead to a vanishing
cosmological constant at the classical level emerge naturally in this setting.Comment: 22 pages. Footnote 14 added in v
The UV behavior of Gravity at Large N
A first step in the analysis of the renormalizability of gravity at Large N
is carried on. Suitable resummations of planar diagrams give rise to a theory
in which there is only a finite number of primitive superficially divergent
Feynman diagrams. The mechanism is similar to the the one which makes
renormalizable the 3D Gross-Neveu model at large N. Some potential problems in
fulfilling the Slavnov-Taylor and the Zinn-Justin equations are also pointed
out.Comment: 17 pages, 9 figures. To appear on Phys. Rev. D. Two more references,
further technical details and the discussion of the KLT relations at large N
have been include
On Electric Fields in Low Temperature Superconductors
The manifestly Lorentz covariant Landau-Ginzburg equations coupled to
Maxwell's equations are considered as a possible framework for the effective
description of the interactions between low temperature superconductors and
magnetic as well as electric fields. A specific experimental set-up, involving
a nanoscopic superconductor and only static applied fields whose geometry is
crucial however, is described, which should allow to confirm or invalidate the
covariant model through the determination of the temperature dependency of the
critical magnetic-electric field phase diagram and the identification of some
distinctive features it should display.Comment: 14 pages (Latex) + 2 postscript figure
The resultant parameters of effective theory
This is the 4-th paper in the series devoted to a systematic study of the
problem of mathematically correct formulation of the rules needed to manage an
effective field theory. Here we consider the problem of constructing the full
set of essential parameters in the case of the most general effective
scattering theory containing no massless particles with spin J > 1/2. We
perform the detailed classification of combinations of the Hamiltonian coupling
constants and select those which appear in the expressions for renormalized
S-matrix elements at a given loop order.Comment: 21 pages, 4 LaTeX figures, submitted to Phys. Rev.
Testing Inflation: A Bootstrap Approach
We note that the essential idea of inflation, that the universe underwent a
brief period of accelerated expansion followed by a long period of decelerated
expansion, can be encapsulated in a "closure condition" which relates the
amount of accelerated expansion during inflation to the amount of decelerated
expansion afterward. We present a protocol for systematically testing the
validity of this condition observationally.Comment: 4 pages, 2 figures, matches Phys. Rev. Lett. versio
The Conformal Window of deformed CFT's in the planar limit
We discuss in the planar approximation the effect of double-trace
deformations on CFT's. We show that this large class of models posses a
conformal window describing a non-trivial flow between two fixed points of the
renormalization group, and reveal the presence of a resonance which we
associate to the remnant of a dilaton pole. As the conformal window shrinks to
zero measure the theory undergoes a conformal phase transition separating a
symmetric from a nonsymmetric phase. The recently conjectured strongly coupled
branch of non-supersymmetric, non-abelian gauge theories with a large number of
flavors is analyzed in light of these results, and a model for the strong
branch is proposed. Some phenomenological implications in the context of
unparticle physics are also emphasized.Comment: 15 pages PRD class, 2 figures, to be published in PR
Papapetrou Energy-Momentum Tensor for Chern-Simons Modified Gravity
We construct a conserved, symmetric energy-momentum (pseudo-)tensor for
Chern-Simons modified gravity, thus demonstrating that the theory is Lorentz
invariant. The tensor is discussed in relation to other gravitational
energy-momentum tensors and analyzed for the Schwarzschild, Reissner-Nordstrom,
and FRW solutions. To our knowledge this is the first confirmation that the
Reissner-Nordstrom and FRW metrics are solutions of the modified theory.Comment: 8 pages; typos corrected, references fixed, some calculations
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