Entanglement entropy of an accelerating universe

We have considered the existence of a dependence of the entanglement entropy on the cosmological horizon surface area also in several accelerating models of the current universe both for a quintessence scalar field and for a phantom-energy scenario. It is shown that if a quintessence vacuum cosmic field is considered then, though the case for w>-1 satisfies a second law for entanglement entropy, when w<-1 such a law is violated. It is finally noted that the entanglement entropy and the distinct formulations of cosmic holography share common future surfaces which are optimal screen for the latter descriptions. © 2012 American Physical Society.This work was supported by MICINN under Research Project FIS2008- 06332.Peer Reviewe

Closed timelike curves in superfluid 3^{3}He

It is shown that the curved spacetime induced in a thin film of superfluid $^{3}$He-A by the presence of symmetric vortices with the unbroken symmetry phase, admits the existence of closed timelike curves through which only superfluid clusters formed by anti-$^{3}$He atoms can travel and violate causality.Comment: 7 pages, LaTex, to appear in Phys. Lett.

Entanglement entropy of an accelerating universe

We have considered the existence of a dependence of the entanglement entropy on the cosmological horizon surface area also in several accelerating models of the current universe both for a quintessence scalar field and for a phantom-energy scenario. It is shown that if a quintessence vacuum cosmic field is considered then, though the case for w &gt; À1 satisfies a second law for entanglement entropy, when w &lt; À1 such a law is violated. It is finally noted that the entanglement entropy and the distinct formulations of cosmic holography share common future surfaces which are optimal screen for the latter descriptions. [7]). Actually, entanglement entropy measures a degree of the correlation between subsystems of a given quantum system All the above results allow us to confidently extrapolate the above horizon area-entanglement entropy proportionality law to any system where quantum entanglement takes place in a cosmic space-time. The results that we are going to get later on are all consistent with that extrapolation. In fact, in this brief report we are going to extend the existence of such a dependence of entanglement entropy on the cosmological horizon surface area also in accelerating models for the current universe both for a quintessence scalar dark-energy field and for a phantom-energy scenario. It will be shown that if an usual quintessence vacuum cosmic field is considered [11], then, though the case for w &gt; À1 (note that along this report we shall only consider an equation of state for the Universe with the perfect-fluid form p ¼ w, with p the pressure and the energy density) satisfies a second law for entanglement entropy, when w &lt; À1 such a law would be violated. We want to estimate the entanglement entropy that corresponded to a quantum field in an accelerating spacetime which is inexorable endowed with a future event horizon where w ¼ p= is the parameter of the equation of state, a 0 and t 0 are the initial values of the scale factor and time, and the constant C is given by C ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 8G=3 p , with an integration constant. We introduce then a conformal time defined by so tha

Unified dark energy thermodynamics: varying w and the -1-crossing

We investigate, in a unified and general way, the thermodynamic properties of dark energy with an arbitrary, varying equation-of-state parameter w(a). We find that all quantities are well defined and regular for every w(a), including at the -1-crossing, with the temperature being negative in the phantom regime (w(a)-1). The density and entropy are always positive while the chemical potential can be arbitrary. At the -1-crossing, both temperature and chemical potential are zero. The temperature negativity can only be interpreted in the quantum framework. The regular behavior of all quantities at the -1-crossing, leads to the conclusion that such a crossing does not correspond to a phase transition, but rather to a smooth cross-over.Comment: 5 pages, version published in Class. Quant. Gra

Phantom thermodynamics

This paper deals with the thermodynamic properties of a phantom field in a flat Friedmann-Robertson-Walker universe. General expressions for the temperature and entropy of a general dark-energy field with equation of state $p=\omega\rho$ are derived from which we have deduced that, whereas the temperature of a cosmic phantom fluid ($\omega<-1$) is definite negative, its entropy is always positive. We interpret that result in terms of the intrinsic quantum nature of the phantom field and apply it to (i) attain a consistent explanation for some recent results concerning the evolution of black holes which,induced by accreting phantom energy, gradually loss their mass to finally vanish exactly at the big rip, and (ii) introduce the concept of cosmological information and its relation with life and the anthropic principle. Some quantum statistical-thermodynamic properties of the quantum quantum field are also considered that include a generalized Wien law and the prediction of some novel phenomena such as the stimulated absorption of phantom energy and the anti-laser effect.Comment: 19 pages, LaTex, 2 figures, accepted for publication in Nuclear Physics

The future of a a-universe

It is argued that the accretion of phantom energy onto a wormhole in a universe with a positive cosmological constant leads also to a gradual increase of the wormhole throat radius, which eventually overtakes the super-accelerated expansion of the universe and becomes infinite at a time in the future before the big rip. Thus, the universe as a whole can time travel toward the past or the future. © World Scientific Publishing Company.Peer Reviewe

Monochromatic two beam multiphoton dissociation of CF2HCl

Infrared multiphoton dissociation induced by monochromatic two-beam excitation has been carried out by controlling the time delay between the two laser beams. The maximum dissociation yield is found to occur at time delays around 5 μs, when the absorbed energy becomes largely stochastized and an equilibrium among the distinct processes of energy relaxation is manifested. It is shown that this behaviour essentially differs from that which occurs in dichromatic multiphoton dissociation. © 1994.This work was done under Project C187/91 supported by the Comunidad Autónoma de Madrid, and an Acción Especial N630/070 provided by the Consejo Superior de Investigaciones Cientificas (C.S.I.C.).Peer Reviewe