1,625 research outputs found
Real Formulations of Complex Gravity and a Complex Formulation of Real Gravity
Two gauge and diffeomorphism invariant theories on the Yang-Mills phase space
are studied. They are based on the Lie-algebras and
-- the loop-algebra of . Although the theories are
manifestly real, they can both be reformulated to show that they describe
complex gravity and an infinite number of copies of complex gravity,
respectively. The connection to real gravity is given. For these theories, the
reality conditions in the conventional Ashtekar formulation are represented by
normal constraint-like terms.Comment: 23 pages, CGPG-94/4-
Deformations of extended objects with edges
We present a manifestly gauge covariant description of fluctuations of a
relativistic extended object described by the Dirac-Nambu-Goto action with
Dirac-Nambu-Goto loaded edges about a given classical solution. Whereas
physical fluctuations of the bulk lie normal to its worldsheet, those on the
edge possess an additional component directed into the bulk. These fluctuations
couple in a non-trivial way involving the underlying geometrical structures
associated with the worldsheet of the object and of its edge. We illustrate the
formalism using as an example a string with massive point particles attached to
its ends.Comment: 17 pages, revtex, to appear in Phys. Rev. D5
Yang-Mills theory a la string
A surface of codimension higher than one embedded in an ambient space
possesses a connection associated with the rotational freedom of its normal
vector fields. We examine the Yang-Mills functional associated with this
connection. The theory it defines differs from Yang-Mills theory in that it is
a theory of surfaces. We focus, in particular, on the Euler-Lagrange equations
describing this surface, introducing a framework which throws light on their
relationship to the Yang-Mills equations.Comment: 7 page
Open strings with topologically inspired boundary conditions
We consider an open string described by an action of the Dirac-Nambu-Goto
type with topological corrections which affect the boundary conditions but not
the equations of motion. The most general addition of this kind is a sum of the
Gauss-Bonnet action and the first Chern number (when the background spacetime
dimension is four) of the normal bundle to the string worldsheet. We examine
the modification introduced by such terms in the boundary conditions at the
ends of the string.Comment: 12 pages, late
Selfdual 2-form formulation of gravity and classification of energy-momentum tensors
It is shown how the different irreducibility classes of the energy-momentum
tensor allow for a Lagrangian formulation of the gravity-matter system using a
selfdual 2-form as a basic variable. It is pointed out what kind of
difficulties arise when attempting to construct a pure spin-connection
formulation of the gravity-matter system. Ambiguities in the formulation
especially concerning the need for constraints are clarified.Comment: title changed, extended versio
Chiral Superconducting Membranes
We develop the dynamics of the chiral superconducting membranes (with null
current) in an alternative geometric approach either making a Lagrangian
description and a Hamiltonian point of view. Besides of this, we show the
equivalence of the resulting descriptions to the one known Dirac-Nambu-Goto
(DNG) case. Integrability for chiral string model is obtained using a proposed
light-cone gauge. In a similar way, domain walls are integrated by means of a
simple ansatz. We compare the results with recently works appeared in the
literature.Comment: Latex file, 17 pages, no figures. Improved version, typos corrected,
Comments and references adde
Remarks on Pure Spin Connection Formulations of Gravity
In the derivation of a pure spin connection action functional for gravity two
methods have been proposed. The first starts from a first order lagrangian
formulation, the second from a hamiltonian formulation. In this note we show
that they lead to identical results for the specific cases of pure gravity with
or without a cosmological constant
The Euler characteristic and the first Chern number in the covariant phase space formulation of string theory
Using a covariant description of the geometry of deformations for extendons,
it is shown that the topological corrections for the string action associated
with the Euler characteristic and the first Chern number of the normal bundle
of the worldsheet, although do not give dynamics to the string, modify the
symplectic properties of the covariant phase space of the theory. Future
extensions of the present results are outlined.Comment: 12 page
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