5,252 research outputs found
A Riccati type PDE for light-front higher helicity vertices
This paper is based on a curious observation about an equation related to the
tracelessness constraints of higher spin gauge fields. The equation also occurs
in the theory of continuous spin representations of the Poincar\'e group.
Expressed in an oscillator basis for the higher spin fields, the equation
becomes a non-linear partial differential operator of the Riccati type acting
on the vertex functions. The consequences of the equation for the cubic vertex
is investigated in the light-front formulation of higher spin theory. The
classical vertex is completely fixed but there is room for off-shell quantum
corrections.Comment: 27 pages. Updated to published versio
Degenerate Sectors of the Ashtekar Gravity
This work completes the task of solving locally the Einstein-Ashtekar
equations for degenerate data. The two remaining degenerate sectors of the
classical 3+1 dimensional theory are considered. First, with all densitized
triad vectors linearly dependent and second, with only two independent ones. It
is shown how to solve the Einstein-Ashtekar equations completely by suitable
gauge fixing and choice of coordinates. Remarkably, the Hamiltonian weakly
Poisson commutes with the conditions defining the sectors. The summary of
degenerate solutions is given in the Appendix.Comment: 19 pages, late
Counterterms in Gravity in the Light-Front Formulation and a D=2 Conformal-like Symmetry in Gravity
In this paper we discuss gravity in the light-front formulation (light-cone
gauge) and show how possible counterterms arise. We find that Poincare
invariance is not enough to find the three-point counterterms uniquely.
Higher-spin fields can intrude and mimic three-point higher derivative gravity
terms. To select the correct term we have to use the remaining
reparametrization invariance that exists after the gauge choice. We finally
sketch how the corresponding programme for N=8 Supergravity should work.Comment: 26 pages, references added, published versio
A trick for passing degenerate points in Ashtekar formulation
We examine one of the advantages of Ashtekar's formulation of general
relativity: a tractability of degenerate points from the point of view of
following the dynamics of classical spacetime. Assuming that all dynamical
variables are finite, we conclude that an essential trick for such a continuous
evolution is in complexifying variables. In order to restrict the complex
region locally, we propose some `reality recovering' conditions on spacetime.
Using a degenerate solution derived by pull-back technique, and integrating the
dynamical equations numerically, we show that this idea works in an actual
dynamical problem. We also discuss some features of these applications.Comment: 9 pages by RevTeX or 16 pages by LaTeX, 3 eps figures and epsf-style
file are include
Quark-Gluon Jet Differences at LEP
A new method to identify the gluon jet in 3-jet ``{\bf Y}'' decays of
is presented. The method is based on differences in particle multiplicity
between quark jets and gluon jets, and is more effective than tagging by
leptonic decay. An experimental test of the method and its application to a
study of the ``string effect'' are proposed. Various jet-finding schemes for
3-jet events are compared.Comment: 11 pages, LaTeX, 4 PostScript figures availble from the author
([email protected]), MSUTH-92-0
Causal structure and degenerate phase boundaries
Timelike and null hypersurfaces in the degenerate space-times in the Ashtekar
theory are defined in the light of the degenerate causal structure proposed by
Matschull. Using the new definition of null hypersufaces, the conjecture that
the "phase boundary" separating the degenerate space-time region from the
non-degenerate one in Ashtekar's gravity is always null is proved under certain
circumstances.Comment: 13 pages, Revte
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