Compact stars in minimal dilatonic gravity Marseille, 18. 07. 2014 - - PowerPoint PPT Presentation

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Compact stars in minimal dilatonic gravity Marseille, 18. 07. 2014 - - PowerPoint PPT Presentation

Jun 05, 2023 223 likes •371 views

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

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Compact stars in minimal dilatonic gravity

Marseille, 18. 07. 2014 Plamen Fiziev

Sofia University Foundation for Theoretical and Computational Physics and Astrophysics & BLTF, JINR, Dubna

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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 ???

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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

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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)

Locally equivalent to f(R): Variable: Gravitational factor Cosmologycal factor Λ > 0 Φ > 0 U > 0

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Basic Equations of MDG: (PPF 2000-2014)

,

Cosmological principle respected !

In GR with cosmological constant :

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4D Trace – traceless splitting:

(PPF 2013)

Simplest example (PPF 2002):

,

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No ghosts! No tachions ! Withholding potentials: PPF, PRD (2013)

Comparison of the Starobinsky 1980 potential VSt and dilatonic potential V with identical masses of the scalaron and MDG-dilaton: MDG is consistent with Solar system experiments if: (PPF 2000)

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The basic equations of SSSS in MDG

Generalized TOV equations: PF: arXiv:1402.281

A =

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NOVEL Quantities and EOS:

Cosmological energy-density and pressure: Dilatonic energy-density and pressure: Three equations

  • f state:
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One parametric ( 𝒒𝒅 ) family of SSSS – as in GR and the Newton gravity !

The boundary conditions for SSSS in MDG

Assuming: SSSS edge: Cosmological horizon: De Sitter vacuum Two specific MDG relations

P = 0

PF: arXiv:1402.281

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Chandrasechkar (1935), TOV (1939) MEOS in MDG

PF: arXiv:1402.281 17%

weaker gravity

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In MDG we have the same stability properties of SSSS as in GR

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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.

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MICHELANGELO Buonarroti, 1511:

Separation of Light from Darkness

Thank you!

More efforts seem to be needed! A rather old cosmological problem: