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Scientific paper
Nov 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aipc..861.1045t&link_type=abstract
ALBERT EINSTEIN CENTURY INTERNATIONAL CONFERENCE. AIP Conference Proceedings, Volume 861, pp. 1045-1050 (2006).
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Canonical Formalism, Lagrangians, And Variational Principles, Particle-Theory And Field-Theory Models Of The Early Universe, Lagrangian And Hamiltonian Approach, Dark Energy
Scientific paper
The discovery of the accelerated expansion in addition to the early inflationary scenario of the universe has triggered an effort to theoretically explain how this behavior can be brought about. The theories based on dark energy, quintessence, phantom fields, and other more or less imaginative names, lacking any physical evidence other than the expansion itself, essentially try and find non-standard Lagrangians from which appropriate field and motion equations can be derived. The simplest is to introduce one more universal field, coupled to geometry in the usual way; other possibilities are to study non-linear (in the curvature) Lagrangians, and/or non minimally coupled fields. In the uncertainty about what the right approach may be, we tried to use a physical guiding idea based on an analogy from every day's physics. Simple dissipative systems may be described by an appropriate Lagrangian. Starting from this fact, the analogy between the equations of motion across a viscous medium and a rate-dependent expansion of the universe is exploited to build a peculiar spacetime Lagrangian density. The proposed action integral may be thought of as corresponding to a special case of a non-minimally coupled vector field. In the usual approach, vector fields are in general ruled out, but this is not the case here. We interpret our vector field as a `physical' property of spacetime itself rather than a matter/energy field coupled to geometry differently than other ordinary fields. Eventually a phase of accelerated expansion of spacetime around a pointlike defect is obtained.
Capone Massimo
Tartaglia Angelo
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