12,584 research outputs found
A Review on the Cosmology of the de Sitter Horndeski Models
We review the most general scalar-tensor cosmological models with up to
second-order derivatives in the field equations that have a fixed spatially
flat de Sitter critical point independent of the material content or vacuum
energy. This subclass of the Horndeski Lagrangian is capable of dynamically
adjusting any value of the vacuum energy of the matter fields at the critical
point. We present the cosmological evolution of the linear models and the
non-linear models with shift symmetry. We come to the conclusion that the shift
symmetric non-linear models can deliver a viable background compatible with
current observations.Comment: 7 pages, 2 figures. Proceedings accepted for publication in
"Universe", Special Issue "Varying Constants and Fundamental Cosmology" for
the VARCOSMOFUN16 in Szczecin, Poland, 12-17 September, 201
Temperature dependence of the coercive field in single-domain particle systems
The magnetic properties of Cu97Co3 and Cu90Co10 granular alloys were measured
over a wide temperature range (2 to 300K). The measurements show an unusual
temperature dependence of the coercive field. A generalized model is proposed
and explains well the experimental behavior over a wide temperature range. The
coexistence of blocked and unblocked particles for a given temperature rises
difficulties that are solved here by introducing a temperature dependent
blocking temperature. An empirical factor gamma arise from the model and is
directly related to the particle interactions. The proposed generalized model
describes well the experimental results and can be applied to other
single-domain particle system.Comment: 7 pages, 8 figures, revised version, accepted to Physical Review B on
29/04/200
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