IS IT POSSIBLE TO OBSERVATIONALLY DISTINGUISH ADIABATIC
QUARTESSENCE FROM CDM?
Luca Amendola1, Martin Makler2, Ribamar R. R. Reis3 and Ioav Waga3
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
0
m0
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).
K.G. Begeman, A.H. Broeils, R.H.
Sanders, MNRAS 249 (1991) 523.
Allen et al. – astro-ph/0405340
The non-relativistic, pressureless, matter
is predominantly dark and non-baryonic
(from Big Bang Nucleosynthesis).
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 regime
Dark 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
BACKGROUND DEPENDENT OBSERVATIONAL CONSTRAINTS
SNeIa + Clusters +
Radio-galaxies + weak lensing
Makler, Quinet & Waga PRD 68,123521, 2003
PROBLEMS – LINEAR PERTURBATIONS
 = - 0.1
 = 0.1
 = 0.2
=0
Sandvik, Tegmark, Zaldarriaga e Waga, Phys. Rev. D
69, 123524 (2004).
Beça et al.- PRD 67,101301,2003
Reis, Waga, Calvão & Jorás –PRD 68,061302 (2003).
L. Amendola, I. Waga e F. Finelli, JCAP 11, 009 (2005)
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
A finite sound speed in recent times is responsible for the
instabilities in the power spectrum
SOLUTION:
Reis et al., Phys. Rev. D 68, 061302(R) (2003)
CHAPLYGIN
L. Amendola, I. Waga e F. Finelli, JCAP 11, 009 (2005)
OTHER CASES
Reis, Makler e Waga, Class. Quant. Grav. 22, 353 (2005) , Erratum-ibid.22, 1191 (2005).
= 0
 = 0.3
 = 0.2
 = 0.1
OTHER CASES
Reis, Makler e Waga, Class. Quant. Grav. 22, 353 (2005) , Erratum-ibid.22, 1191 (2005).
= 0
 = 0.3
 = 0.2
 = 0.1
A NEW TYPE OF QUARTESSENCE
L. Amendola, M. Makler, R. R. R. Reis e I. Waga, Phys. Rev. D 74, 063524 (2006).
TYPE Ia SUPERNOVAE
X-RAY CLUSTER GAS FRACTION
CONSTRAINTS FROM SNeIa AND CLUSTERS
CONSTRAINTS FROM MATTER (SDSS)
AND CMB POWER SPECTRUM (WMAP1)
COMBINED ANALYSIS: SNeIa + Clusters + SDSS + WMAP1
zt

CONCLUSION
• 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.