1,404 research outputs found
A hydrodynamic approach to boost invariant free streaming
We consider a family of exact boost invariant solutions of the transport
equation for free streaming massless particles, where the one particle
distribution function is defined in terms of a function of a single variable.
The evolution of second and third moments of the one particle distribution
function (the second moment being the energy momentum tensor (EMT) and the
third moment the non equilibrium current (NEC)) depends only on two moments of
that function. Given those two moments we show how to build a non linear
hydrodynamic theory which reproduces the early time evolution of the EMT and
the NEC. The structure of these theories may give insight on nonlinear
hydrodynamic phenomena on short time scales.Comment: 20 pages, 8 figures. Accepted for publication in Phys. Rev.
Analog cosmology with spinor BECs
We show that the properties of spinor Bose-Einstein condensates allow us to
build an analog Taub (axisymmetric Bianchi IX) Universe. We shall develop this
proposal on the example of a rubidium condensate, where the relevant
experiments are well within present day capabilities. A better Taub analog
however would be built out of a collective Rydberg excitation.Comment: Talk given at the "II Amazonian Symposium on Physics - Analogue
Models of Gravity 30 Years Celebration
Drag reduction by polymer additives from turbulent spectra
We extend the analysis of the friction factor for turbulent pipe flow
reported by G. Gioia, P. Chakraborty and N. Goldenfeld (GCG) (G. Gioia and P.
Chakraborty, Phys. Rev. Lett. 96, 044502 (2006), N. Goldenfeld, Phys. Rev.
Lett. 96, 044503 (2006)) to the case where drag is reduced by polymer
additives.Comment: 19 pages, major changes, accepted for publication in Phys. Rev.
The 2 - particle irreducible effective action in gauge theories
The goal of this paper is to develop the formalism of the two-particle
irreducible (2PI) \cite{LW61} (or Cornwall - Jackiw - Tomboulis (CJT) \cite
{CJT}) effective action (EA) in a way appropiate to its application to non
equilibrium gauge theories. We hope this review article will stimulate new work
into this field.Comment: 25 page
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