400 research outputs found
Attractor solutions for general hessence dark energy
As a candidate for the dark energy, the hessence model has been recently
introduced. We discuss the critical points of this model in almost general
case, that is for arbitrary hessence potential and almost arbitrary
hessence-background matter interaction. It is shown that in all models, there
always exist some stable late-time attractors. It is shown that our general
results coincide with those solutions obtained earlier for special cases, but
some of them are new. These new solutions have two unique characteristics.
First the hessence field has finite value in these solutions and second, their
stabilities depend on the second derivative of the hessence potential.Comment: 11 pages. Add some explanations about the autonomousity of the
equations, and also a conclusion section was added. To appear in Phys. Rev. D
(2006
Cosmological coincidence problem in interacting dark energy models
An interacting dark energy model with interaction term is considered. By studying the model near the
transition time, in which the system crosses the w=-1 phantom-divide-line, the
conditions needed to overcome the coincidence problem is investigated. The
phantom model, as a candidate for dark energy, is considered and for two
specific examples, the quadratic and exponential phantom potentials, it is
shown that it is possible the system crosses the w=-1 line, meanwhile the
coincidence problem is alleviated, the two facts that have root in
observations.Comment: 15 pages, LaTeX. Some minor explanations are added. To be published
in Phys. Rev.
Generating Functional and Large N-Limit of Nonlocal 2D Generalized Yang-Mills Theories ('s)
Using the path integral method, we calculate the partition function and
generating functional (of the field strengths) on the nonlocal generalized 2D
Yang - Mills theories ('s), which is nonlocal in auxiliary field [14].
Our calculations is done for general surfaces. We find a general expression for
free energy of in theories at the strong
coupling phase (SCP) regime () for large groups. In the specific
model, we show that the theory has a third order phase transition.Comment: tex file, no figure. accepted for publication in Eur. Phys. J. C.
(2000
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