2 research outputs found
Logarithm of the scale factor as a generalised coordinate in a lagrangian for dark matter and dark energy
A lagrangian for the essence field is set up with canonical kinetic
terms and incorporating the scaling relation of [1]. There are two degrees of
freedom, {\it viz.}, ( is the scale factor) and the
scalar field , and an interaction term involving and .The
Euler-Lagrange equations are solved for and . Using these solutions
quantities of cosmological interest are determined. The energy density
has a constant component which we identify as dark energy and a component
behaving as which we call dark matter. The pressure is {\it
negative} for time and the sound velocity . When dark energy dominates, the deceleration
parameter while in the matter dominated era . The
equation of state parameter is shown to be consistent with
for dark energy domination and during the matter
dominated era we have . Bounds for the parameters of the theory are
estimated from observational data.
Keywords: k-essence models, dark matter, dark energy
PACS No: 98.80.-kComment: 16 pages, latex, paper shortened by 2 pages for journal publicatio