Bounds on the gravitational constant from a two-solar-mass neutron - - PowerPoint PPT Presentation

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Bounds on the gravitational constant from a two-solar-mass neutron - - PowerPoint PPT Presentation

Dec 11, 2023 347 likes •681 views

Bounds on the gravitational constant from a two-solar-mass neutron star Antonio Dobado , F. Llanes Estrada and J.A. Oller Departamento de Fsica Terica, Universidad Compltense 28040-Madrid, Spain Strong interactions beyond the Standard Model

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Bounds on the gravitational constant from a two-solar-mass neutron star

Antonio Dobado, F. Llanes Estrada and J.A. Oller

Departamento de Física Teórica, Universidad Compltense 28040-Madrid, Spain

Physikzentrum Bad Honnef February 13th 2012

Strong interactions beyond the Standard Model

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Outline

  • Learning nuclear physics from gravity

and the other way around by using massive pulsars

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Neutron stars are the only window to part of the QCD phase diagram

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Ciudad Real XXXII Bienal de Física (2009) 4

The whole idea is based in the interpretation of the pulsars, discovered by Hewish in 1967, as neutron stars (Gold and others)

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XXXII Bienal de Física (2009) 6

Neutron stars are believed to be the final states of massive stars which are not heavy enough to become black holes. In order to get some hystorical perspective... Let us take a tome machine a go back 110 years....

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Neutrons stars are a natural lab for structure of matter Conjectures on the possibilty of exotic phases in the inner region

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The motivation was the recent claim of the discovery of a two-solar- mass neutron star.

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In contradicion with previous claims from the theoretical side

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And almost all measured pulsar masses

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But confirming a previous claim of neutron stars in this mass range

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Radio timing observations of the binary millisecond second pulsar J1614-2230 show a strong Shapiro delay signature giving a pulsar mass of about 1.97 +/- 0.04 solar mass. Demorest et al. 10.1038/nature 09466.

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The theory of neutron stars started in 1939 with the seminal work by Oppenheimer-Volkoff and Tolman

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Oppenheimer-Volkov-Tolman equation

General relativistic hydrostatic equilibrium (spherical bodies) Important relativistic contributions Must be supplemented with the matter Equation of State (EoS)

P=P (ε)

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Oppenheimer–Volkoff and Tolman plus the Equation of State allows the study of the equilibrium conditions for neutron stars

Gravity Strong Interaction

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a) Assuming we know gravity we can learn about strong interactions (EoS). b) Assuming we know strong interactions we can learn about gravity (GN).

Therefore we have two possibilities:

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Blue: Nucleons Pink: Nucleons plus exotic matter (kaons, hyperons…) Green: Strange quark matter

Case a)

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So we can rule out most of the exotic scenarios for the matter of neutron stars (quark matter, hyperons, kaon condensates) from the EoS in the maket, but perhaps strongly interacting quark matter (Demorest et all)

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Case b) From a given EoS

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We can get information about GN in an unexplored new regime (relativistic and high g)

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Earth surface

GN

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Earth surface J0737-3039 White darfs PSR B1913+16 (Hulse-Taylor) PSR J1614-2230 (Demorest et al)

This value is compatible with the ones found in

  • ther scenarios with much larger accelerations
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This result may be relevant since many extensions

  • f GR predict GN = GN (g)
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Now we can extrapolate to the 1.97 solar-masses J1614-2230 pulsar assuming a given EoS.

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For example the recently propossed based on Chiral Pertubation Theory which reproduces quite well the nuclear matter density from first principles (Chiral Symmetry and consistent momentum power counting in nuclear matter)

Leading Order Vr=1 Op5 1 Vr=1 NexttoLeading Order Op6 2 NexttoLeading Order Vr=2 Op6

... 3.1 3.2 ...

Lacour, Oller and Meissner 2009

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Solving Oppenheimer-Volkov-Tolman equation it is possible to find the acceleration profile for the two-solar-masses neutron star.

XXXII Bienal de Física (2009)

PSR J1614-2230

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Nuclear EoS supports at most 2.2 solar masses

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Vary the Newton constant:

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Variation of GN by more than 12% produce gravitational collapse upper bound on GN since there is a two-solar-masses neutron star

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Setting a new upper bound on GN at large g. (12% of the Earth value at he 95% confidence level)

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Summary and open questions

  • Pulsars are a very interesting laboratory to study the

interplay between strong interactions and gravity in the General Relativistic regime.

  • The recent finding of a two-solar masses pulsar allows to

rule out many models of strange nuclear matter and to set bounds on the variation of GN in a new regime of extremely high g (12 orders of magnitude the one on Earth).

  • This result can be usefull to set new constraints on

modifications of GR such as f(R) or Lovelock theories of gravities.

  • Work is in progress in that direction.
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