842 research outputs found
A PILOT STUDY OF PLANS THAT THE UNITED STATES FOOD INDUSTRY HAS FOR PARTICIPATING IN EASTERN EUROPE
Agribusiness, International Relations/Trade,
Geometric Gravitational Forces on Particles Moving in a Line
In two-dimensional space-time, point particles can experience a geometric,
dimension-specific gravity force, which modifies the usual geodesic equation of
motion and provides a link between the cosmological constant and the vacuum
-angle. The description of such forces fits naturally into a gauge
theory of gravity based on the extended Poincar\'e group, {\it i.e.\/}
``string-inspired'' dilaton gravity.Comment: 10 pages, CTP#214
Extended de Sitter Theory of Two Dimensional Gravitational Forces
We present a simple unifying gauge theoretical formulation of gravitational
theories in two dimensional spacetime. This formulation includes the effects of
a novel matter-gravity coupling which leads to an extended de Sitter symmetry
algebra on which the gauge theory is based. Contractions of this theory
encompass previously studied cases.Comment: 19pp, no figs., CTP 2228, UCONN-93-
Energy-Momentum Conservation in General Relativity
We discuss general properties of the conservation law associated with a local
symmetry. Using Noether's theorem and a generalized Belinfante symmetrization
procedure in 3+1 dimensions, a symmetric energy-momentum (pseudo) tensor for
the gravitational Einstein-Hilbert action is derived and discussed in detail.
In 2+1 dimensions, expressions are obtained for energy and angular momentum
arising in the gauge theoretical formulation of Einstein gravity. In
addition, an expression for energy in a gauge theoretical formulation of the
string-inspired 1+1 dimensional gravity is derived and compared with the ADM
definition of energy.Comment: 18 pages in Plain TeX, MIT-CTP-224
Quantum States of String-Inspired Lineal Gravity
We construct quantum states for a (1+1) dimensional gravity-matter model that
is also a gauge theory based on the centrally extended Poincar\'e group.
Explicit formulas are found, which exhibit interesting structures. For example
wave functionals are gauge invariant except for a gauge non-invariant phase
factor that is the Kirillov-Kostant 1-form on the (co-) adjoint orbit of the
group. However no evidence for gravity-matter forces is found.Comment: 23 pages in REVTEX, MIT-CTP-227
A WZW model based on a non-semi-simple group
We present a conformal field theory which desribes a homogeneous four
dimensional Lorentz-signature space-time. The model is an ungauged WZW model
based on a central extension of the Poincar\'e algebra. The central charge of
this theory is exactly four, just like four dimensional Minkowski space. The
model can be interpreted as a four dimensional monochromatic plane wave. As
there are three commuting isometries, other interesting geometries are expected
to emerge via duality.Comment: 8 pages, phyzzx, IASSNS-HEP-93/61 Texable versio
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