Two recent tests of loop quantum gravity theory

  • #1
kodama
978
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TL;DR Summary
on electromagnetic properties of charged leptons and via the Lensing Effect
2 recent gains on loop quantum gravity theory

arXiv:2403.18606 (gr-qc)
[Submitted on 27 Mar 2024]
Test the Loop Quantum Gravity Theory via the Lensing Effect
Lai Zhao, Meirong Tang, Zhaoyi Xu
Recently, scholars such as Lewandowski, Ma, and Yang have successfully derived a quantum-corrected black hole model in loop quantum gravity (Phys.Rev.Lett.130.101501 (2023)), which is a modification of the Schwarzschild black hole. In this paper, we calculate the strong/weak gravitational lensing effects under the quantum-corrected black hole model, taking the supermassive black holes M87* and SgrA* as the subjects of study to explore the impact of the quantum correction parameter α on the positions of images and the Einstein ring. Our calculations show that in the case of strong gravitational lensing, the lensing coefficient a¯ increases with an increase in the quantum correction parameter, while the deflection angle and the lensing coefficient b¯ decrease with an increase in the quantum correction parameter. The quantum correction parameter α has a significant impact in the context of supermassive black holes. In weak gravitational lensing, the quantum correction parameter α plays a suppressive role. Our theoretical analysis suggests that with advancements in future astrophysical observation techniques, it might be possible to test loop quantum gravity theory using the gravitational lensing effect.

Subjects: General Relativity and Quantum Cosmology (gr-qc)
Cite as: arXiv:2403.18606 [gr-qc]
(or arXiv:2403.18606v1 [gr-qc] for this version)

https://doi.org/10.48550/arXiv.2403.18606

and

[Submitted on 7 Dec 2023 (v1), last revised 28 Dec 2023 (this version, v2)]
Shadows of Loop Quantum Black Holes: Semi-analytical Simulations of Loop Quantum Gravity Effects on Sagittarius A* and M 87*
Hong-Xuan Jiang, Cheng Liu, Indu K. Dihingia, Yosuke Mizuno, Haiguang Xu, Tao Zhu, Qiang Wu

In this study, we delve into the observational implications of rotating Loop Quantum Black Holes (LQBHs) within an astrophysical framework. We employ semi-analytical General Relativistic Radiative Transfer (GRRT) computations to study the emission from the accretion flow around LQBHs. Our findings indicate that the increase of Loop Quantum Gravity (LQG) effects results in an enlargement of the rings from LQBHs, thereby causing a more circular polarization pattern in the shadow images. We make comparisons with the Event Horizon Telescope (EHT) observations of Sgr\,A∗ and M\,87∗, which enable us to determine an upper limit for the polymetric function P in LQG. The upper limit for Sgr\,A∗ is 0.2, while for M\,87∗ it is 0.07. Both black holes exhibit a preference for a relatively high spin (a≳0.5 for Sgr\,A∗ and 0.5≲a≲0.7 for M\,87∗). The constraints for Sgr\,A∗ are based on black hole spin and ring diameter, whereas for M\,87∗, the constraints are further tightened by the polarimetric pattern. In essence, our simulations provide observational constraints on the effect of LQG in supermassive black holes (SMBH), providing the most consistent comparison with observation.
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
Cite as: arXiv:2312.04288 [gr-qc]
(or arXiv:2312.04288v2 [gr-qc] for this version)

https://doi.org/10.48550/arXiv.2312.04288

and

arXiv:2305.04336 (gr-qc)
[Submitted on 7 May 2023 (v1), last revised 30 Oct 2023 (this version, v2)]
Strong Gravitational Lensing by Loop Quantum Gravity Motivated Rotating Black Holes and EHT Observations
Jitendra Kumar, Shafqat Ul Islam, Sushant G. Ghosh
We investigate gravitational lensing in the strong deflection regime by loop quantum gravity (LQG)-motivated rotating black hole (LMRBH) metrics with an additional parameter l besides mass M and rotation a. The LMRBH spacetimes are regular everywhere, asymptotically encompassing the Kerr black hole as a particular case and, depending on the parameters, describe black holes with one horizon only (BH-I), black holes with an event horizon and a Cauchy horizon (BH-II), black holes with three horizons (BH-III), or black holes with no horizons (NH) spacetime. It turns out that as the LQG parameter l increases, the unstable photon orbit radius xps, the critical impact parameter ups, the deflection angle αD(θ) and angular position θ∞ also increases. Meanwhile, the angular separation s decreases, and relative magnitude rmag increases with increasing l for prograde motion but they show opposite behaviour for the retrograde motion. For Sgr A*, the angular position θ∞ is ∈ (16.4, 39.8) μas, while for M87* ∈ (12.33, 29.9) μas. The angular separation s, for SMBHs Sgr A* and M87*, differs significantly, with values ranging ∈ (0.008-0.376) μas for Sgr A* and ∈ (0.006-0.282) μas for M87*. We estimate the time delay between the first and second relativistic images using twenty supermassive galactic centre black holes as lenses. Our analysis concludes that, within the 1σ region, a significant portion of the BH-I and BH-II and for a small portion of BH-III parameter space agrees with the EHT results of M87* and Sgr A* whereas NH is completely ruled out. We discover that the EHT results of Sgr A* place more stringent limits on the parameter space of LMRBH black holes than those established by the EHT results of M87*.

Comments: 16 Pages, 11 Figures, 3 Tables, Accepted for publication in EPJC
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2305.04336 [gr-qc]
(or arXiv:2305.04336v2 [gr-qc] for this version)

and

arXiv:2302.10482 (gr-qc)
[Submitted on 21 Feb 2023 (v1), last revised 29 Apr 2023 (this version, v2)]
Observational tests of quantum extension of Schwarzschild spacetime in loop quantum gravity with stars in the galactic center
Jian-Ming Yan, Cheng Liu, Tao Zhu, Qiang Wu, Anzhong Wang


In this paper, we use the publicly available observational data of 17 stellar stars orbiting Sgr A* to test the quantum extension of Schwarzschild spacetime in loop quantum gravity (LQG). For our purpose, we transform the geodesical evolution of a massive particle in the quantum-extended Schwarzschild black hole to the perturbed Kepler problem and calculate the effects of LQG on the pericentre advance of the stellar stars. With these effects, one is able to compare them with the publicly available astrometric and spectroscopic data of stellar stars in the galactic center. We perform Monte Carlo Markov Chain (MCMC) simulations to probe the possible LQG effects on the orbit of S-stars. No significant evidence of the quantum-extended Schwarzschild black hole from LQG is found. Among the posterior analyses of 17 S-stars, the result of S2 gives the strongest bound on the LQG parameter Aλ, which places an upper bound at 95\% confidence level on Aλ to be Aλ<0.302.

Comments: 12 pages, 6 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
Cite as: arXiv:2302.10482 [gr-qc]
(or arXiv:2302.10482v2 [gr-qc] for this version)

https://doi.org/10.48550/arXiv.2302.10482
Journal reference: Phys. Rev. D 107, 084043 (2023)
Related DOI:
https://doi.org/10.1103/PhysRevD.107.084043


arXiv:2403.17197 (hep-th)
[Submitted on 25 Mar 2024]
Loop Quantum Gravity effects on electromagnetic properties of charged leptons
João Paulo S. Melo, Mario J. Neves, Jefferson M. A. Paixão, José A. Helayël-Neto

The efforts in this contribution consist in reassessing a modified Dirac equation that incorporates a γ0γ5-Lorentz-symmetry violating (LSV) term induced as a Loop Quantum Gravity (LQG) effect. Originally, this equation has been applied and considered as a good scenario for describing a number of investigations on the flight time of cosmic photons and neutrinos, which suggests that the speed of light in vacuum, in connection with the geometry that describes a granular space-time, takes an energy-dependent form, e.g., v(E)=1±E/ELSV, with ELSV≈6,5×1017 GeV for neutrinos. Once LQG provides a viable way to consistently understand this picture, we pursue an analysis of this effective Dirac equation to inspect some of its properties. These include: the derivation of the modified fermionic propagator, attainment of the Gordon decomposition of the vector current with minimal electromagnetic coupling to obtain information on the form factors, examination of the non-relativistic limit of the equation, evaluation of the spin- and velocity-dependent corrections to the Coulomb potential due to LQG effects, and the modified Hamiltonian in the low-relativistic regime. The study of the form factors may open up paths to set up bounds on the LQG parameters from the precision measurements of electromagnetic attributes of the charged leptons, such as their respective electric and magnetic dipole moments.

Comments: 11 pages, 2 figures
Subjects: High Energy Physics - Theory (hep-th); High Energy Physics - Phenomenology (hep-ph)
Cite as: arXiv:2403.17197 [hep-th]
(or arXiv:2403.17197v1 [hep-th] for this version))

https://doi.org/10.48550/arXiv.2403.17197

any comment on test loop quantum gravity theory on electromagnetic properties of charged leptons and via the Lensing Effect

are those predictions the strong/weak gravitational lensing effects under the quantum-corrected black hole model, taking the supermassive black holes M87* and SgrA* as the subjects of study on unique to loop quantum gravity theory
or
could string theory, SUGRA, semiclassical gravity also make predictions strong gravitational lensing, the lensing of supermassive black holes M87* and SgrA* via the Lensing Effect

what if observations of strong gravitational lensing, the lensing of supermassive black holes M87* and SgrA* confirm loop quantum gravity theory

attributes of the charged leptons, such as their respective electric and magnetic dipole moments is something useful for connecting to experiment by electron EDM

if loop quantum gravity theory on electromagnetic properties of charged leptons and via the Lensing Effect confirm by future experiment should Nobel Prize be awarded and loop quantum gravity theorywins over string theory ?
 
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  • #2
"Our theoretical analysis suggests that with advancements in future astrophysical observation techniques, it might be possible to test loop quantum gravity theory using the gravitational lensing effect."


LQG makes specific predictions on strong gravitational lensing for the supermassive black holes M87* and SgrA* that can be observed, in principle, by Event Horizon Telescope (EHT) observations or future telescopes.

what if these LQG predictions of gravitational lensing for the supermassive black holes M87* and SgrA* are verified?

there was a recent solar eclipse in the USA.

isn't this like the original test of GR vs Newton during the 1919 solar eclipse, here GR vs LQG using gravitational lensing
 
  • #3
The headline of the OP is a bit misleading. Scientists have proposed ways to test if reality is closer to the LQG or the classical GR prediction. But, nobody has actually done those tests at the level of precision necessary to actually distinguish between the two theories with any meaningful statistical significance.
 
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  • #4
ohwilleke said:
The headline of the OP is a bit misleading. Scientists have proposed ways to test if reality is closer to the LQG or the classical GR prediction. But, nobody has actually done those tests at the level of precision necessary to actually distinguish between the two theories with any meaningful statistical significance.

what do you think of strong gravitational lensing, the lensing of supermassive black holes M87* and SgrA*as a way to test quantum gravity effects ?

does string theory make any predictions of strong gravitational lensing, the lensing of supermassive black holes M87* and SgrA*?

could quantum gravity effects show up as strong gravitational lensing, the lensing of supermassive black holes M87* and SgrA*
 
  • #5
kodama said:
what do you think

What do you think?
 
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  • #6
kodama said:
what do you think of strong gravitational lensing, the lensing of supermassive black holes M87* and SgrA*as a way to test quantum gravity effects ?
It is a great and obvious way to test quantum gravity effects, once you have the telescopes (defined broadly to include anything that makes an astronomy observation) to do it. Since they are, by definition, at the heart of these galaxies, however, sifting through the foregrounds to observe what you really want to see is challenging.
kodama said:
does string theory make any predictions of strong gravitational lensing, the lensing of supermassive black holes M87* and SgrA*?
String theory makes no predictions and has no observational support. It isn't really even really a theory so much as an approach to come up with a theory that no one has managed to set forth yet.
kodama said:
could quantum gravity effects show up as strong gravitational lensing, the lensing of supermassive black holes M87* and SgrA*
Yes.
 
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  • #7
ohwilleke said:
It is a great and obvious way to test quantum gravity effects, once you have the telescopes (defined broadly to include anything that makes an astronomy observation) to do it. Since they are, by definition, at the heart of these galaxies, however, sifting through the foregrounds to observe what you really want to see is challenging.

String theory makes no predictions and has no observational support. It isn't really even really a theory so much as an approach to come up with a theory that no one has managed to set forth yet.

Yes.

this
arXiv:2305.04336 (gr-qc)
[Submitted on 7 May 2023 (v1), last revised 30 Oct 2023 (this version, v2)]
Strong Gravitational Lensing by Loop Quantum Gravity Motivated Rotating Black Holes and EHT Observations
Jitendra Kumar, Shafqat Ul Islam, Sushant G. Ghosh

We estimate the time delay between the first and second relativistic images using twenty supermassive galactic centre black holes as lenses. Our analysis concludes that, within the 1σ region, a significant portion of the BH-I and BH-II and for a small portion of BH-III parameter space agrees with the EHT results of M87* and Sgr A* whereas NH is completely ruled out. We discover that the EHT results of Sgr A* place more stringent limits on the parameter space of LMRBH black holes than those established by the EHT results of M87*.

. Our analysis concludes that, within the 1σ region, perhaps 5σ might be measured in more advanced degree with better quality telescopes

String theory makes no predictions and has no observational support. It isn't really even really a theory so much as an approach to come up with a theory that no one has managed to set forth yet.

String theory predicts massless spin 2, identify with the gravitons

gravitons in qft is a type of quantum gravity

does gravitons spin 2 in qft or super gravity quantum gravity effects show up as strong gravitational lensing, the lensing of supermassive black holes M87* and SgrA*?


if successful loop quantum gravity theory 5σ quantum gravity effects show up as strong gravitational lensing, the lensing of supermassive black holes M87* and SgrA* could other quantum gravity theory reproduce the same results
 
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  • #8
arXiv:2404.12811 (gr-qc)
[Submitted on 19 Apr 2024]
Black Hole shadows of α′-corrected black holes
F. Agurto-Sepúlveda, J. Oliva, M. Oyarzo, D.R.G Schleicher

In this paper we study the qualitative features induces by corrections to GR coming from String Theory, on the shadows of rotating black holes. We deal with the slowly rotating black hole solutions up to order O(a3), to first order in α′, including also the dilaton. We provide a detailed characterization of the geometry, as well as the ISCO and photon ring, and then we proceed to obtain the black hole images within the relativistic thin-disk model. We characterize the images by computing the diameter, displacement and asymmetry. A comparison with the Kerr case, indicates that all these quantities grow due to the α′ correction, and that the departure from GR for different observable is enhanced depending on the angle of view, namely for the diameter the maximum departure is obtained when the system is face-on, while for the displacement and asymmetry the departure from GR is maximized for edge-on point of view.

Comments: 14 pages, 8 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
Cite as: arXiv:2404.12811 [gr-qc]
(or arXiv:2404.12811v1 [gr-qc] for this version)

"corrections to GR coming from String Theory, on the shadows of rotating black holes" vs "gravitational lensing in the strong deflection regime by loop quantum gravity (LQG)-motivated rotating black hole"

"In this paper, we calculate the strong/weak gravitational lensing effects under the quantum-corrected black hole model, taking the supermassive black holes M87* and SgrA* as the subjects of study to explore the impact of the quantum correction parameter α on the positions of images and the Einstein ring."

vs
"In this paper we study the qualitative features induces by corrections to GR coming from String Theory, on the shadows of rotating black holes. We deal with the slowly rotating black hole solutions up to order O(a3), to first order in α′, including also the dilaton. We provide a detailed characterization of the geometry, as well as the ISCO and photon ring,"

similar to lqg
both papers on quantum corrections to GR , on the shadows of rotating black holes

would be interested to compare quantum corrections to GR coming from String Theory, on the shadows of rotating black holes with loop quantum gravity (LQG)-motivated rotating black hole strong gravitational lensing, the lensing of supermassive black holes M87* and SgrA* with real world observations
 
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  • #9
kodama said:
similar to lqg
In that both can be printed on A4 paper, yes.

You keep pointing us to papers that do not say what you say they do. You did it with the X17 and you're doing it now. It is more than a little annoying.
 
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  • #10
of interest

arXiv:2403.09756 (gr-qc)
[Submitted on 14 Mar 2024 (v1), last revised 21 Apr 2024 (this version, v2)]
Signatures of the accelerating black holes with a cosmological constant from the Sgr~A⋆ and M87⋆ shadow prospects
L. Chakhchi, H. El Moumni, K. Masmar

Recently, the Event Horizon Telescope (EHT) achieved the realization of an image of the supermassive black hole Sgr~A⋆ showing an angular shadow diameter D=48.7±7μas and the fractional deviation δ=−0.08+0.09−0.09 (VLTI),−0.04+0.09−0.10 (Keck), alongside the earlier image of M87⋆ with angular diameter D=42±3μas, deviation δ=−0.01+0.17−0.17 and deviations from circularity estimated to be ΔC≲10%. In addition, the shadow radii are assessed within the ranges 3.38≤rsM≤6.91 for M87⋆ and 3.85≤rsM≤5.72 as well as 3.95≤rsM≤5.92 for Sgr~A⋆ using the Very Large Telescope Interferometer (VLTI) and Keck observatories, respectively. These values are provided with 1-σ and 2-σ measurements. Such realizations can unveil a better comprehension of gravitational physics at the horizon scale. In this paper, we use the EHT observational results for M87⋆ and Sgr~A⋆ to elaborate the constraints on parameters of accelerating black holes with a cosmological constant. Concretely, we utilize the mass and distance of both black holes to derive the observables associated with the accelerating black hole shadow. First, we compare our findings with observed quantities such as angular diameter, circularity, shadow radius, and the fractional deviation from the M87⋆ data. This comparison reveals constraints within the acceleration parameter and the cosmological constant...
Lastly, one cannot rule out the possibility of the negative values for the cosmological constant on the emergence of accelerated black hole solutions within the context of minimal gauged supergravity...

Comments: 37 pages, 10 figures, references updated
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
Cite as: arXiv:2403.09756 [gr-qc]
(or arXiv:2403.09756v2 [gr-qc] for this version)

https://doi.org/10.48550/arXiv.2403.09756
Journal reference: Physics of the Dark Universe 44 (2024) 101501
Related DOI:
https://doi.org/10.1016/j.dark.2024.101501
 
  • #11
Vanadium 50 said:
In that both can be printed on A4 paper, yes.

You keep pointing us to papers that do not say what you say they do. You did it with the X17 and you're doing it now. It is more than a little annoying.
It seems the OP is more confused, possibly on a higher level, about these things than I am.
 

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