Got to Seoul safely. Asked Eric Linder what a Galileon is, and apparently it's a scalar field that has Galilean transform symmetry (as opposed to Lorenz transformation symmetry). Work begins tomorrow.
http://arxiv.org/abas/1106.0314
The nonlinear power spectrum in clustering quintessence cosmologies
D'Amico, Sefusatti
* I wonder what E. Sefusatti is up to.
This is a study of NL evolution of matter perturbation in "clustering quintessence cosmologies with vanishing speed of sound." Then the matter and quintessence perturbations are comoving, and one can write a single continuity equation for the density fluctuations using a weighted sum of each. Solve the evolution equation via Euler's into NL regime using Time-Renormalization group approach. Observable only related to total density perturbations only (individual components not observable).
Clustering of quintessence perturbations induce small correction wrt NL power spectrum evolution in smooth quintessence models with same equation of state. But linear regimes are more strongly affected by the vanishing sound of speed at low z; sound of speed strongly affects the shape of power spectra at different scales for models with the same spectra normalization. Such differences vanish as w => -1. This shows that the linear and the NL regime difference can be important in constraining DE models.
* Sound of speed is sqrt(bulk modulus/density) [Newton-Laplace], or sqrt{d(pressure)/d(density)}.
* Euler's fluid equations are a set of equations that govern inviscid (no viscosity) flow. They represent (i) mass conservation [continuity], (ii) momentum and (iii) energy conservation (although historically it has only been i and ii). It corresponds to Navier-Stokes equation with zero viscosity. Euler's equations can be applied to both compressible (use equation of state) and incompressible (assume zero divergence of flow velocity) flow.
* I need basic lessons in physics.
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