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Título               : A strong constraint on Omega, Lambda and possible quintessence using 2dF quasar structures as standard rulers  
Conferencista: Gary Mamon, IAP  
Data                  : Quarta-feira, 26/09/01 15H30M  
Local                 : Auditório L.B.F. Clauzet - Água Funda  
Sumário           :
The internal kinematics of groups and clusters have long been used to constrain the density parameter of the Universe Omega to values of roughly 0.3 times the critical density, value confirmed by the study of the baryonic content of these systems. The use of supernovae as standard candles has more recently shown that the cosmological constant Lambda is positive, leading to an accelerating Universe. Finally very recent analyses of the Cosmic Microwave Background lead to an angular fluctuation spectrum highly consistent with a flat Universe, i.e. Omega + Lambda = 1. Taking any two of these findings together yields Omega = 0.3 and Lambda = 0.7.
I will describe how B. Roukema and I have been constraining these cosmological parameters, using very large scale structures (larger than 50 Mpc) as standard rulers in the comoving frame that expands with the Universe. Our first results on a semi-reliable quasar sample yielded Omega = 0.3. More recently, we have used the much more reliable 10QZ sample obtained with the 2dF quasar survey. With fewer hypotheses, we obtain simultaneous constraints on Omega and Lambda, consistent with the values given above, from 240 Mpc features. Our study represesents the first joint constraint on Omega and Lambda from a single sample and with a single method. I will also show our constraint on quintessence. Tighter constraints are expected when the 2dF and SDSS surveys reach completion.