lqg people claim, that they found the solution to quantum gravity. please comment. in this context i will add and heavily recommend an article written by Hermann Nicolai, which i will add.
Very sceptical.
Quantum gravity is not a well defined sort of topic to start with.
I write a paper explaining the solution to the divergence problem of gravity and that the Planck-scale cutoff energy has a physical origin.
Preprint Sphere Theory: Completing Quantum Gravity through Gravitatio...
good discussion
some questions:
- Off‑shell versus on‑shell constraint closure The arguement that on‑shell closure—where the commutator of two Hamiltonians vanishes only after projecting onto a restricted “habitat” of states—is insufficient for true quantum space‑time covariance . Are there more recent attempts (post‑2006) that come close to establishing genuine off‑shell closure in 3 + 1 D? what of the the Master‑Constraint or Algebraic QG programmes promising in this regard?
- Hamiltonian ambiguities and ultralocal action Referring to the discussion of the infinitely many operator‑ordering and representation choices—leading to an “embarras de richesse” of possible Hamiltonians—was illuminating . Have any physical criteria emerged that narrow these choices (e.g., compatibility with coarse‑graining flows or new semiclassical tests)? Could an explicitly non‑ultralocal Hamiltonian resolve the missing 2→2 and 0→4 Pachner move, as highlight when comparing to spin foams ?
- Continuum limit of spin‑foam sums In the spin‑foam section it stress that finiteness proofs usually address individual foams (an IR issue) rather than a refinement or sum‑over‑foams limit . Has there been progress on demonstrating Einstein‑Hilbert behaviour under systematic coarse‑graining, perhaps via group‑field‑theory renormalisation? Does any present evidence favour Barrett–Crane‑type amplitudes over EPRL–FK (or vice versa) in that respect?
- Semi‑classical states note that only kinematical coherent states were known at the time . Are there promising constructions today that solve all constraints and exhibit correct long‑distance graviton 2‑point functions?
Harri Shore i find LQG already in the foundations very doubtful. in the Ashtekar variables, there appears from the very beginning a parameter, the Immirizi parameter. for a theory, that claims to be the final solution of quantum gravitay, this is very unsatisfying.
Harri Shore
to say the least. i think, its a fundamental flaw of qlg.
I so t find String theory any better, on any aspect.
I think it will be useful mathematically once the the picture is complete.
I suspect that in some way one of the spacetime itself is impossible to be regarded as such.
Time becomes important.
I know how vague this sounds, but these things tend to skirt the edge of meta physics.
Perhaps we theres a paper here… in collaboration
Recent SS post in
https://www.researchgate.net/post/Are-gravitational-waves-ripples-in-the-curvature-of-spacetime-or-are-it-fluctuations-of-the-gravitational-field#view=6818bf5c1f86ddca0806d794/4/4/3/4/5
and reDzennn comment , 4 passages in https://phys.org/news/2025-05-bridging-worlds-physicists-holographic-principle.html
- are relevant to this thread question.
Cheers
[Now this thread is indexed in its “Scientific topics” sections , more see section “PS” in SS post April 30 in https://www.researchgate.net/post/Is-it-true-that-physicists-do-not-want-to-understand-quantum-mechanics/329 , page 329]
Regarding the loop quantum gravity versus string theory controversy, there is a very funny "Big-bang theory" episode that I recommend everybody to watch.
“…..yes its not very elegant...…Regarding the loop quantum gravity versus string theory controversy, there is a very funny "Big-bang theory" episode that I recommend everybody to watch.…”
- there can be, relating to both, the loop quantum gravity and string theory, seems a lot of somethings that are elegant, funny, etc.; but all this, including the both theories, can have a sense only if the theories are considered as some exclusively mathematical structures. Which fundamentally have no any relation to what really exists and happens in Matter.
Gravity, as that rigorously scientifically shown in the Shevchenko-Tokarevsky’s Planck scale informational physical model, two main papers are https://www.researchgate.net/publication/391209088_The_Informational_Conception_and_Basic_Physics, [ in the paper secton 2.9 “Mediation of the forces in complex systems” can be passed since this is more comprehensively given in section 6.“Mediation of the fundamental forces in complex systems” in other paper below] , and
https://www.researchgate.net/publication/367397025_The_Informational_Physical_Model_and_Fundamental_Problems_in_Physics
- fundamentally is nothing else than some fundamental Nature force, which - as all other , i.e. Weak, Electric, Nuclear/Strong Forces , fundamentally acts in the Matter’s fundamentally absolute, fundamentally flat, fundamentally continuous, and fundamentally “Cartesian”, spacetime that has metrics (at least) [4+4+1]4D (cτ,X,Y,Z, g,w,e,s,ct) [utmost universal sub-spacetime, which is observable by some ways experimentally, has metrics [5]4D (cτ,X,Y,Z,ct)],
- where all 8 space dimensions, and the fundamentally unique time ct-dimension, are absolute, independent on each other, fundamentally by no means can impact on anything in Matter and be impacted by anything in Matter, be “graining”, etc.
Including, correspondingly, there are no any fundamental problems at developing QM-Gravity – as that happened at developing of QM theories of all other Forces [that is another thing that all – classical and QFTs – theories, as that rigorously scientifically shown in the model, have fundamental flaws, more see the links above]
And well possibly the quantum nature of Gravity can be observed experimentally - see proposed yet in 2007 experiment with photons in https://www.researchgate.net/publication/215526868_The_informational_model_-_possible_tests, section “Monochromatic photon beam distortion”.
More see the links above, to read SS post on page 1, and, since the Gravity and the spacetime are principal points in cosmology, reDzennn comment, 4 passages, in
https://phys.org/news/2025-05-dark-evolving-energy.html
Cheers
I have an idea to complete quantum gravity, and I'd like you to read it.
It is a foundational principle, recognized in both Newtonian mechanics and general relativity, that the effective gravitational source is the equivalent mass (M_eq), which includes gravitational self-energy (binding energy), rather than the free state mass (M_fr). This principle leads to a running gravitational coupling, G(k), that vanishes at a critical scale, R_gs ~ G_NM_fr/c^2. This behavior provides a powerful and self-contained mechanism for gravity’s self-renormalization, driving the coupling to a trivial fixed point (G(k) -> 0) and rendering the infinite tower of EFT counter-terms unnecessary.
The scope of Sphere Theory extends far beyond the divergence problem, providing a unified foundation for several long-standing puzzles. We demonstrate that this single principle:
1) Resolves the singularity problem via a repulsive force that emerges at a macroscopic, not quantum, scale (Section 2, 3, 4.5).
2) Solves the non-renormalizability of gravity, as exemplified by the 2-loop divergence of Goroff and Sagnotti, by demonstrating that the interaction is dynamically turned off at a critical scale (Section 4.6.3).
3) Resolves the unitarity crisis in high-energy graviton scattering by showing that the scattering amplitude naturally vanishes as the physical source of the interaction is quenched (Section 4.9).
4) Provides the physical origin of the UV cutoff for quantum field theories, demonstrating that the gravitational self-energy of force mediators (e.g., photons, gravitons) dynamically suppresses their propagation at the Planck scale (Section 4.7~ 4.9).
5) Resolves the divergence and the Landau pole problem in QED, transforming it into a potentially fundamental theory by providing a physical cutoff mechanism rooted in the gravitational self-energy of the photon (Section 4.8).
6) Provides a UV completion for EFT. It resolves divergence problems arising in (1)the gravitational potential between two masses and (2)the bending of light. This approach also renders the infinite tower of unknown EFT coefficients (c_i) unnecessary and makes a novel, falsifiable prediction of a "quantum-dominant regime” (Section 5).
7) Offers a unified explanation for major cosmological puzzles by providing (1)a mechanism for cosmic inflation, (2)a model for the universe's accelerated expansion}, and (3)a predicted upward revision of the neutron star mass limit} (TOV limit) (Section 7).
8) Finally, it culminates in a declaration that the synthesis of EFT and Sphere Theory constitutes a self-consistent and testable framework for quantum gravity, providing a consistent description from the lowest to the highest energy scales (Section 8).
[Summary]
https://www.reddit.com/r/NegativeMassPhysics/comments/1lox9li/sphere_theory_beyond_string_theory_completing/
Preprint Sphere Theory: Completing Quantum Gravity through Gravitatio...
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