Monday, 2 January 2017

Testing emergent gravity: Gravitational Lensing to atom interferometer

Paranal Telescopes in Chile. (ESO/H.H. Heyer)
In this post, I would like to briefly discuss emergent gravity, an idea, that gravity itself is an artefact of more fundamental description, such as entropy. Despite the fact that we have an experimental evidence of gravitational waves, thus gravity really exist and physically detectable: The recent results of Laser Interferometer Gravitational-Wave Observatory (LIGO) programme in detecting gravitation waves was a landmark experimental evidence supporting Einstein's General Relativity theory.

Emergent Gravity: Verlinde's thesis

Eric Verlinde has proposed a controversial hypothesis in 2010 that gravity is originated from an entropic force [here]. He has shown that both Newtonian and Einstein's gravitational equations are artefacts of entropic force and in 2016 he proposed a similar approach in explaining galactic motions without the need of using dark matter [here].

Testing Emergent Gravity: Gravitational Lensing

Margot M. Brouwer and her co-workers have published a work [here], using weak gravitational lensing data from ESO telescopes. This was the first evidence for Verlinde's theory which attracted a lot of media attention because of implications in our understanding of the nature of gravity.

Testing Entropic Gravity Directly: Atom Interferometer

Despite this initial test of emergent gravity, there is still a lack of direct experimental evidence for Verlinde's initial hypothesis that force laws are artefacts of entropic force. Recently another approach is proposed to test this entropic force argument, [here], using mater-wave interferometry via utilising part of Newton-Schroedinger. The core idea is there is a direct relationship between the gravitational constant G and the atomic system's quantum state. If this is experimentally feasible, maybe with next generation atom interferometer systems, this could be a direct test for Verlinde's entropic force argument.

1 comment:

  1. This is quite a striking argument from Chesler-Loeb: Modified Newtonian Dynamics MOND type theories, "...These are modified theories of gravity designed to emulate the effects of dark matter without actually having dark matter ..", might be incompatible with LIGO observations; "...gravitational waves should obey two simple principles: (i) they should propagate at the speed of light and (ii)
    they should obey linear equations in the weak-field limit...". To be honest, I liked the idea of MOND/entropic gravity approaches that simplifies things, but after all 'Dark Matter' might be real.

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