Presentation on theme: "IS IT POSSIBLE TO OBSERVATIONALLY DISTINGUISH ADIABATIC QUARTESSENCE FROM CDM? Luca Amendola 1, Martin Makler 2, Ribamar R. R. Reis 3 and Ioav Waga 3 1."— Presentation transcript:
IS IT POSSIBLE TO OBSERVATIONALLY DISTINGUISH ADIABATIC QUARTESSENCE FROM CDM? Luca Amendola 1, Martin Makler 2, Ribamar R. R. Reis 3 and Ioav Waga 3 1 INAF/Osservatorio Astronomico di Roma, 2 Centro Brasileiro de Pesquisas Físicas, 3 Instituto de Física – Universidade Federal do Rio de Janeiro
THE COSMOLOGICAL STANDARD MODEL
The non-relativistic, pressureless, matter is predominantly dark and non-baryonic (from Big Bang Nucleosynthesis). The universe seems to be dominated by a smooth component that drives the accelerated expansion. The spatial curvature is very close to zero (from CMB). Allen et al. – astro-ph/ K.G. Begeman, A.H. Broeils, R.H. Sanders, MNRAS 249 (1991) 523.
SOME IMPORTANT QUESTIONS: - What is the nature of the Dark Matter? - What is the nature of the Dark Energy? -Could these components be different aspects of the same substance?
UNIFYING DARK MATTER OR QUARTESSENCE A prototype – the generalized Chaplygin Gas. Chaplygin Gas ( =1) – initially suggested as an alternative to quintessence Kamenshchik et al. PLB 511, 265 (2001). Motivation: D-Branes. Dark matter regimeDark energy regime
For every quartessence model, the density decreases towards to a minimum value min and remains constant. In this phase, it behaves like a cosmological constant (w=-1). w<-1 is forbidden for such models
PROBLEMS – LINEAR PERTURBATIONS Sandvik, Tegmark, Zaldarriaga e Waga, Phys. Rev. D 69, (2004). Beça et al.- PRD 67,101301,2003 Reis, Waga, Calvão & Jorás –PRD 68, (2003). L. Amendola, I. Waga e F. Finelli, JCAP 11, 009 (2005) = = 0 = 0.1 = 0.2
PERTURBATION THEORY IN COSMOLOGY
Linear evolution equations in synchronous gauge (A=B=0) for a multi-component fluid. Assuming vanishing spatial curvature and anisotropic stress, and conservation of the energy-momentum tensor of each component.
ORIGIN OF THE PROBLEM SOLUTION: A finite sound speed in recent times is responsible for the instabilities in the power spectrum Reis et al., Phys. Rev. D 68, (R) (2003)
L. Amendola, I. Waga e F. Finelli, JCAP 11, 009 (2005) CHAPLYGIN
We have on known manner of obtain quartessence models, distinct from CDM, in agreement with Large scale structure and CMB data: considering entropy perturbations; Observational constraints on the step-like model impose which implies that the transition has occurred at. The hypothesis of unifying dark matter cannot be ruled out with the present observational data. CONCLUSION
TRABALHOS PUBLICADOS NA ÁREA R. R. R. Reis, Phys. Rev. D 67, (2003), Erratum-ibid. D 68, (2003). R. R. R. Reis, I. Waga, M. O. Calvão, and S. E. Jorás, Phys. Rev. D 68, (R) (2003). R. R. R. Reis, M. Makler, and I. Waga, Phys. Rev. D 69, (R) (2004). R. R. R. Reis, M. Makler and I. Waga, Class. Quant. Grav. 22, 353 (2005), Erratum- ibid. 22, 1191 (2005). L. Amendola, M. Makler, R. R. R. Reis and I. Waga, Phys. Rev. D 74, (2006).