798 research outputs found
Continuum coupled cluster expansion
We review the basics of the coupled-cluster expansion formalism for numerical
solutions of the many-body problem, and we outline the principles of an
approach directed towards an adequate inclusion of continuum effects in the
associated single-energy spectrum. We illustrate our findings by considering
the simple case of a single-particle quantum mechanics problem.Comment: 16 pages, 1 figur
Gauge Formulation for Higher Order Gravity
This work is an application of the second order gauge theory for the Lorentz
group, where a description of the gravitational interaction is obtained which
includes derivatives of the curvature. We analyze the form of the second field
strenght, , in terms of geometrical variables. All possible
independent Lagrangians constructed with quadratic contractions of and
quadratic contractions of are analyzed. The equations of motion for a
particular Lagrangian, which is analogous to Podolsky's term of his Generalized
Electrodynamics, are calculated. The static isotropic solution in the linear
approximation was found, exhibiting the regular Newtonian behaviour at short
distances as well as a meso-large distance modification.Comment: Published versio
Singularity structure in Veneziano's model
We consider the structure of the cosmological singularity in Veneziano's
inflationary model. The problem of choosing initial data in the model is shown
to be unsolved -- the spacetime in the asymptotically flat limit can be filled
with an arbitrary number of gravitational and scalar field quanta. As a result,
the universe acquires a domain structure near the singularity, with an
anisotropic expansion of its own being realized in each domain.Comment: 16 pages, 2 figures, shorter then journal version; references added,
discussion slightly expande
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