Plamen Fiziev Sofia University Foundation for Theoretical and Computational Physics and Astrophysics & BLTF, JINR, Dubna Compact stars in minimal dilatonic gravity Marseille, 18. 07. 2014
The basic lesson from cosmology: GR and the Standard Particles Model are not enough ! • One may add some new content: Dark matter, Dark energy • One may modify GR: simplest modifications are F(R) and MDG • Some combination of the above two possibilities may work ? What about the Star Physics ??? Do we have the same problem : EOS versus gravity modification??? Maybe we need both pisibilities simultaneously ???
Plan of the talk: • Minimal dilatonic gravity (MDG) • The basic equations of SSSS in MDG • The boundary conditions for SSSS in MDG • Neutron SSSS with simplest EOS in MDG SSSS = Static Spherically Symmetric Stars
Minimal dilatonic gravity (MDG) O’Hanlon : PRL, 1972, PPF: Mod. Phys. Lett. A, 15, 1077 (2000); gr-qc/0202074; PRD 67 , 064016 (2003); PRD 87 , 0044053 (2013); arXiv:1402.2813. (Brans-Dicke with ω = 0 – not quite correct) Variable: Λ > 0 Φ > 0 U > 0 Cosmologycal factor Gravitational factor Locally equivalent to f(R):
Basic Equations of MDG: (PPF 2000-2014) , In GR with cosmological constant : Cosmological principle respected !
4D Trace – traceless splitting: (PPF 2013) Simplest example (PPF 2002): ,
Withholding potentials: PPF, PRD (2013) No ghosts! No tachions ! MDG is consistent with Solar system experiments if: (PPF 2000) Comparison of the Starobinsky 1980 potential V St and dilatonic potential V with identical masses of the scalaron and MDG-dilaton:
The basic equations of SSSS in MDG PF: a rXiv:1402.281 Generalized TOV equations: A =
NOVEL Quantities and EOS: Dilatonic energy-density and pressure: Cosmological energy-density and pressure: Three equations of state:
The boundary conditions for SSSS in MDG PF: a rXiv:1402.281 Assuming: SSSS edge: P = 0 Cosmological horizon: De Sitter vacuum Two specific MDG relations One parametric ( 𝒒 𝒅 ) family of SSSS – as in GR and the Newton gravity !
Chandrasechkar (1935), TOV (1939) MEOS in MDG PF: a rXiv:1402.281 17% weaker gravity
In MDG we have the same stability properties of SSSS as in GR
Conclusion Most probably we need to look simultaneously and coherently for a realistic EOS and for a realistic withholding cosmological potential which are able to describe a variety of cosmological, astrophysical, gravitational and star phenomena at different scales: compact stars, with dwarfs, normal stars, stars clusters, galaxies, galaxy clusters, … It is not excluded that they are related with different de Sitter vacuums, suitable for corresponding different scales and for different time epochs.
MICHELANGELO Buonarroti, 1511 : Separation of Light from Darkness A rather old cosmological problem: More efforts seem to be needed! Thank you!
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