Crossing the Phantom Divide

Article Article scientifique Article Crossing the Phantom Divide eng 2006-12-08 2006-12-08 author Kunz Martin 109032 author Sapone Domenico 635559 123503 10.1103/PhysRevD.74.123503 1550-2368 astro-ph/0609040 https://link.aps.org/doi/10.1103/PhysRevD.74.123503 We consider fluid perturbations close to the 'phantom divide' characterised by p = -rho and discuss the conditions under which divergencies in the perturbations can be avoided. We find that the behaviour of the perturbations depends crucially on the prescription for the pressure perturbation delta-p. The pressure perturbation is usually defined using the dark energy rest-frame, but we show that this frame becomes unphysical at the divide. If the pressure perturbation is kept finite in any other frame, then the phantom divide can be crossed. Our findings are important for generalised fluid dark energy used in data analysis (since current cosmological data sets indicate that the dark energy is characterised by p ~ -rho so that p < -rho cannot be excluded) as well as for any models crossing the phantom divide, like some modified gravity, coupled dark energy and braneworld models. We also illustrate the results by an explicit calculation for the 'Quintom' case with two scalar fields. 95.36.+x 98.80.-k Energy: density Tensor: energy-momentum Field theory: scalar Velocity: perturbation Fluid: perturbation Energy: phantom Dark energy Pressure: perturbation Equation of state Quintom Dewey 500.2 37 Département de physique théorique 133 false Physical review. D, Particles, fields, gravitation, and cosmology 74 12 d2187cee-24c3-470e-9641-27b480495282 Article (Published version) Public PhysRevD.74.123503.pdf 646212 application/pdf openAccess Faculté des sciences / Section de physique / Département de physique théorique

Title	Published in	Access level	OA Policy	Year	Views	Downloads

Crossing the Phantom Divide	Physical review. D, Particles, fields, gravitation, and cosmology			2006	167	194

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