Seminar “Modern Mathematical Physics”

Date and Time: Wednesday, 29 November 2017, at 2:30 PM

Venue: Blokhintsev Hall (4th floor), Bogoliubov Laboratory of Theoretical Physics

Seminar topic: «GR170817 / GRB170817a, Modified Theories of Gravity, and Compact Stars in Minimal Dilatonic Gravity»

Speaker: Plamen Fiziev (Sofia University, Bulgaria and BLTP, JINR, Dubna, Russia)

Abstract:

The first multi-messenger observations of merger of Neutron Star (NS) binary: GR170817 / GRB170817a, made by LIGO-VIRGO collaboration and 70 astronomical observatories and satellites, reached a large amount of new physical facts and estimates: A higher than previously known masses of NS in the interval M_max / M_⊙∈ [2.15, 2.25], a new estimate for the radius R_1.6 > 10.68(-0.04)(+0.15) km, a novel strong limit on the speed of GWs: |C_GW /C -1| < 6 × 10^-15, validation of the WEP: δγ ≤ 3.4 × 10^-9 , a novel strong limit : |w +1| < 1.2× 10^-14 on the parameter w of dark energy EOS, etc. As a result, a large amount of models of modified theories of gravity was ruled out, including the theories with superluminal movement of GWs, Dark Matter Emulators, Lorentz violating theories, most of the standard general type scalar-tensor theories, bigravity, quartic and quintic Horndeski and most beyond Horndeski theories, Einstein-Aether, Horava gravity, Generalized Proca, TeVeS and other MOND-like gravities. Fortunately, a small number of known extended theories of gravity survive the above strong tests: Jordan-Brans-Dicke (JBD) model, Minimal Dilatonic Gravity (MDG), f(R) models, quintessence conformally coupled models, and MOG (Mofat’s modified gravity). We consider the basic properties of the NS in MDG, PF, Mod. Phys. Lett. A, 32, 1750141 (2017) and stress that the additional mass of NS due to the existence of JBD-scalar-field-halo around NS in MDG is able to avoid the discrepancy between prediction for NS mass from nuclear physics EOS and the new observational maximal mass of NS.

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