its commonly stated that no particle accelerator will ever be built that can probe the planck scale.(adsbygoogle = window.adsbygoogle || []).push({});

what about an can an event horizon telescope observe quantum gravity effects near a black hole, such asSagittarius A*

do the various candidates of QG such as string theory LQG asf gravity, QFT on curved spacetime, sugra etc offer predictions as to what to expect around a event horizon telescope?

this paper makes claims LQG can observe it,

Quantum Gravity Effects around Sagittarius A*

Hal M. Haggard, Carlo Rovelli

(Submitted on 1 Jul 2016 (v1), last revised 5 Jul 2016 (this version, v2))

Recent VLBI observations have resolved Sagittarius A* at horizon scales. The Event Horizon Telescope is expected to provide increasingly good images of the region around the Schwarzschild radius rS of Sgr A* soon. A number of authors have recently pointed out the possibility that non-perturbative quantum gravitational phenomena could affect the space surrounding a black hole. Here we point out that the existence of a region around 76rS where these effects should be maximal.

Comments: 5 pages; Received honorable mention in the Gravity Research Foundation 2016 Awards for Essays on Gravitation

Subjects: General Relativity and Quantum Cosmology (gr-qc)

Cite as: arXiv:1607.00364 [gr-qc]

Realistic Observable in Background-Free Quantum Gravity: the Planck-Star Tunnelling-Time

Marios Christodoulou, Carlo Rovelli, Simone Speziale, Ilya Vilensky

(Submitted on 17 May 2016)

A gravitationally collapsed object can bounce-out from its horizon via a tunnelling process that violates the classical equations in a finite region. Since tunnelling is a non-perturbative phenomenon, it cannot be described in terms of quantum fluctuations around a classical solution and a background-free formulation of quantum gravity is needed to analyze it. Here we use Loop Quantum Gravity to compute the amplitude for this process, in a first approximation. The amplitude determines the tunnelling time as a function of the mass. This is the key information to evaluate the astrophysical relevance of this process. The calculation offers a template and a concrete example of how a background-free quantum theory of gravity can be used to compute a realistical observable quantity.

Comments: We consider this paper important. 16 pages, 12 figures

Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)

Cite as: arXiv:1605.05268 [gr-qc]

(or arXiv:1605.05268v1 [gr-qc] for this version)

are these claims credible, that a telescope can help distinguish various QG theories of astrophysical objects?

does string/m theory as a theory of QG offer predictions and if so, how does it compare to Rovelli et al's papers as to what the event horizon telescope observing Sagittarius A should observe?

i.e Isaac Newton, Albert Einstein, and Gunner Nordstrom all offer predictions as to what gravity would do in bending star light during an eclipse. Nordstrom's theory predicted no bending of star light, Newton one value and Einstein a value twice as large as Newton's. Einstein's prediction was confirmed and general relativity is the theory of classical gravity.

What Rovelli is claiming is something similar. the event horizon telescope can observe the event horizon surrounding Sagittarius A* at horizon scales and LQG offers predictions that differ from what classical GR provides. Does string theory/m theory also offer predictions on what event horizon telescope can observe the event horizon surrounding Sagittarius A* at horizon scales should observe and how do they compare with Rovelli's LQG?

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# A Can an event horizon telescope observe quantum gravity effects

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