§Non-linear EoS:
worth
exploring as dark energy or UDM, has further motivations;
dynamical,
effective cosmological constant(s) mostly natural;
Cosmic
No-Hair from energy conservation: evolution a-la L-CDM at O(0) in
dP/dr(rL) and O(1) in Dr = r - rL , in any
theory of gravity.
§Quadratic EoS:
simplest
choice beyond linear;
represents
truncated Taylor expansion of any
P(r) (3 parameters);
very reach
dynamics:
§allows for acceleration with and
without rL ;
§Standard
and phantom evolution, phantom -> de Sitter (no ÒBig RipÓ);
§Closed
models with loitering, or oscillating with no singularity;
singularities
are isotropic, as in brane models.
§Affine EoS
as UDM pass tests so far and has scalar field equivalent
(background).
§Constraints: high z,
nucleosynthesis (b>0), perturbations.
§