H. Stefancic: The Accelerated Expansion of the Universe and the Cosmological Constant Problem

The accelerated expansion of the universe and the cosmological constant problem ,[object Object],[object Object],Hrvoje Štefančić, Theoretical Physics Division, Ruđer Bošković Institute, Zagreb, Croatia

Big issues - observational and theoretical ,[object Object],[object Object]

Our concept of the (present) universe ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The observed universe ,[object Object],[object Object],[object Object],[object Object]

Expansion of the universe ,[object Object],[object Object],[object Object],[object Object],[object Object]

FRW model – theoretical description of the expansion ,[object Object],[object Object],[object Object],[object Object],[object Object]

FRW model ,[object Object],[object Object],[object Object]

Cosmological observations – mapping the expansion ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Supernovae of the type Ia ,[object Object],[object Object],[object Object],[object Object],[object Object]

Cosmological observations - SNIa ,[object Object],[object Object]

Cosmological observations - CMB ,[object Object]

Cosmological observations - LSS ,[object Object],[object Object]

Standard cosmological model (up to 1998) ,[object Object],[object Object],[object Object]

Spatial curvature ,[object Object],[object Object]

SNIa observations (1998) ,[object Object],[object Object],[object Object],[object Object],[object Object]

CMB and BAO ,[object Object],[object Object],[object Object]

Combining observational data ,[object Object],[object Object],[object Object]

Observational constraints to the DE EOS ,[object Object],[object Object]

Accelerated expansion ,[object Object],[object Object]

Classification of theoretical approaches ,[object Object],R. Bean, S. Caroll, M. Trodden, Insights into dark energy: interplay between theory and observation. Rachel Bean ( Cornell U., Astron. Dept. ) , Sean M. Carroll ( Chicago U., EFI & KICP, Chicago ) , Mark Trodden ( Syracuse U. ) . Oct 2005. 5pp. White paper submitted to Dark Energy Task Force. http://arxiv.org/abs/astro-ph/0510059

Distorted signals and unjustified assumptions? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Distorted signals and unjustified assumptions? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Mechanism of the acceleration ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Dark energy ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Dark energy ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Dark sector ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

DE models ,[object Object],[object Object],[object Object],[object Object]

Λ CDM ,[object Object],[object Object],[object Object],[object Object],[object Object]

Quintessence ,[object Object],[object Object],[object Object],[object Object]

Phantom energy ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Singularities ,[object Object],[object Object],[object Object]

Modified gravity ,[object Object],[object Object],[object Object],[object Object],[object Object]

Braneworlds ,[object Object],[object Object],[object Object],[object Object],[object Object]

The cosmological constant ,[object Object],[object Object],[object Object],[object Object],[object Object]

The expansion with the cosmological constant J. Sol à, hep-ph/0101134v2

The expansion with the cosmological constant

Contributions to vacuum energy ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Zero point energies ,[object Object],[object Object],[object Object]

Condensates ,[object Object],[object Object],[object Object],[object Object]

The size of the CC ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The “old” cosmological constant problem – the problem of size ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The “old” cosmological constant problem ,[object Object],[object Object],[object Object],[object Object],[object Object]

DE vs CC ,[object Object],[object Object],[object Object]

Proposed solutions of the “old” CC problem ,[object Object],[object Object],[object Object],[object Object],[object Object]

Symmetry ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Back-reaction mechanisms ,[object Object],[object Object],[object Object],[object Object]

Violation of the equivalence principle ,[object Object],[object Object],[object Object],[object Object]

Statistical approaches ,[object Object],[object Object],[object Object]

The cosmic coincidence problem – the problem of timing ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Possible solutions of the cosmic coincidence problem ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Composite dark energy – Λ XCDM models ,[object Object],[object Object],[object Object],[object Object],[object Object]

Ratio of DE and matter energy density

Parameter constraints ,[object Object],[object Object],[object Object]

Parameter constraints – cross sections

The CC relaxation mechansim ,[object Object],[object Object],[object Object]

The model dynamics ,[object Object],[object Object],[object Object],[object Object],[object Object]

α < −1: the relaxation mechanism for the large cosmological constant ,[object Object],[object Object]

case ,[object Object],[object Object]

Dependence on model parameters

case ,[object Object],[object Object],[object Object]

Other parameter regimes ,[object Object],[object Object]

Fixed points, approach to de Sitter regime ,[object Object],[object Object],[object Object]

General inhomogeneous EOS ,[object Object],[object Object],[object Object]

Variable cosmological term ,[object Object],[object Object],[object Object],[object Object]

Variable cosmological term ,[object Object]

f(R) modified gravity ,[object Object],[object Object],[object Object],[object Object]

Important questions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Summary of the relaxation mechanism properties ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Relaxing a large cosmological constant - adding matter and radiation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The formalism ,[object Object],[object Object],[object Object]

½ Model ,[object Object],[object Object],[object Object],[object Object],[object Object]

The model ,[object Object],[object Object],[object Object]

Conclusions ,[object Object],[object Object],[object Object],[object Object]

H. Stefancic: The Accelerated Expansion of the Universe and the Cosmological Constant Problem

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H. Stefancic: The Accelerated Expansion of the Universe and the Cosmological Constant Problem