Parameters of Theory of everything.

[Mordred]

I'm sorry but most of that last post makes little sense. 

[studiot]

10 hours ago, MJ kihara said:

16 hours ago, studiot said:

Really ?

 

The difficulty QM has that with that statement is that you can't when it is at that somewhere.

Mass induces gravity to infinity that extent to quantum harmonics/quantum pseudo harmonics (speculative).

It's a transition from quantum realm to classical realm...we can predict with certainity the position of earth on its orbit, however where is earth if you narrow down to it's center of gravity(it's singularity)? Anyway,lots of temptation to go off topic(TOE).

I really can't see the relevance of your reply to my comment.

Sorry I missed a word out whilst editing.

"you can't when it is at that somewhere."    should read  "you can't tell when it is at that somewhere."

 

Did you notice that little word "if" in your quotation from Wikipedia ?

 

What if you don't measure it ?

And what do you understand 'probability' to mean ?

 

Edited September 23 by studiot

[MJ kihara]

6 hours ago, studiot said:

What if you don't measure it ?

Then you don't know if it's there or not.

[swansont]

17 hours ago, MJ kihara said:

Mass induces gravity to infinity that extent to quantum harmonics/quantum pseudo harmonics (speculative).

The speculation in this thread is about a TOE. Not about any other topics.

17 hours ago, MJ kihara said:

It's a transition from quantum realm to classical realm...we can predict with certainity the position of earth on its orbit, however where is earth if you narrow down to it's center of gravity(it's singularity)?

There will always be an uncertainty in any measurement. But it’s going to be quite small relative to the size of the earth.

[chron44]

On 9/22/2024 at 12:59 AM, Mordred said:

You don't require a graviton for renormalization of gravity. The issue with gravity is the UV divergences. No effective cutoff ie singularity conditions 

 

So, either the graviton exists (the proposed spin-2 particle without mass) or not there is a possibility to craft a ToE. Is this what this cite means?

 

[Mordred]

Yes it is plausible to get a ToE without gravitons and even if gravitons are discovered the UV divergence problem will still exist.

[chron44]

32 minutes ago, Mordred said:

Yes it is plausible to get a ToE without gravitons and even if gravitons are discovered the UV divergence problem will still exist.

 

Ok.

Still, this ToE issue is a bit more entangled, I suppose:

First the reduced Planck's constant might be the "quantum floor" to our ability to measure physics, we still don't know if so.

If this is the true physics measurement limit, and the graviton exist similar to our present proposed view of it, we can only notice and confirm the graviton indirectly from gravitational waves and through effects in cosmology, and so on.

This scenario implies that a ToE theory can be "confirmed", with the unification of all 4 forces, by focusing on indirect evidence and buildings of a mathematically coherent theory that fits with experimental data from other areas of physics.

The ToE issue seems to be delicate. In several manners.

 

[Mordred]

A little secret both the graviton and gravity waves properties are derived via the Einstein field equations. Gravity waves being spin 2 quadrupole however does suggest the most likely particle candidate being spin 2 as well.

However there is also spin 1 and spin zero possibility for the graviton. 

 However there is also the possibility that gravity is strictly a spacetime effect and has no mediator boson. 

Edited September 23 by Mordred

[chron44]

47 minutes ago, Mordred said:

A little secret both the graviton and gravity waves properties are derived via the Einstein field equations. Gravity waves being spin 2 quadrupole however does suggest the most likely particle candidate being spin 2 as well.

However there is also spin 1 and spin zero possibility for the graviton. 

 However there is also the possibility that gravity is strictly a spacetime effect and has no mediator boson. 

 

Interesting, so Einstein's field equations imply "its" most possible graviton construction? Or just the bare entities, without its presumed (QM?) properties, of the graviton and the gravitational waves?

Still confusing when GR doesn't - normally - calculate with bosons. It's a QM matter.

Where the analyze and theories from the LIGO, for example, indicates a spn-2 boson?

[Mordred]

The spin 2 characteristics arise from the perturbation rank 2 symmetric tensor \(h_{\mu\nu}\) which is transverse and traceless but also must couple to matter and antimatter. This obviously also requires the rank 2 stress energy momentum tensor.

 The other detail is that gravity only attracts which is also a determining factor for spin 2.

The solutions are rather intense Ryder Lewis "Introductory to Cosmology"gives a simplified solution

However this article describes the main points as to why Spin2 is the most likely 

http://fmatrm.if.usp.br/~enrico/Gravitation_from_Field_Theory.pdf

A simple understanding is that it is the polarizations such as those of gravity waves that leads to the spin 2 and those derive from working from  4D geometry via SO(3.1) Poincare group. 

 

Edited September 24 by Mordred

[chron44]

 

Of what I have so far understood is that there is the problem with the graviton and its UV divergence for suiting a quantized construction...

This, when GR theory in combination with LIGO, among other observations, point on the spin-2 construction of the graviton.

This 4th force really is a tough challenge for a ToE.

[Mordred]

Very close be more accurate to understand that pure gravity via gravitons by itself is renormalizable. Any permutations are not. So the unperturbed Maximally symmetric spacetime  \(\eta_{\mu\nu}\) using the minimally coupled Langrangian is renormalizable. However once you lose maximal symmetry via curvature, gravity waves, cosmological constant, or other permutations involving the stress energy momentum tensor acting upon the perturbation tensor \(h_{\mu\nu}\) are not renormalizable.

These are where the higher order loop integrals arise from not the gravitons (one loop integral field ) by itself.

So under for example the weak field limit.

\[g_{\mu\nu}=\eta_{\mu\nu}+h_{\mu\nu}\]

When \(h_{\mu\nu}=0\) consequently \(T_{\mu\mu}=0\) spacetime is renormalizable. It loses renormalizability when those tensors do not equal zero Dave for the density term at T_(00).

Edited September 24 by Mordred

[MJ kihara]

4 hours ago, Mordred said:

However there is also the possibility that gravity is strictly a spacetime effect and has no mediator boson. 

Effect without cause?

[Mordred]

28 minutes ago, MJ kihara said:

Effect without cause?

No the cause is the other fields acting upon spacetime via their coupling (mass terms) the distinction is if gravity is a force the mediator is the graviton. If it's an effect then there is no mediator and it's strictly the curvature terms arising from the SM particle mass distributions.

 The question becomes is gravity strictly the tidal force (pseudoforce) due to curvature. If it's a force field then under QFT would have a mediator.

Mathematically in both cases it's the acceleration terms in the effect case spacetime curvature itself applies the pseudo force in the graviton case it would mediate the force vectors. In either case you will get the same results as it's been shown gravitons are not needed to explain the effects if spacetime curvature. 

Consequently they are not needful for a ToE. Nor are gravitons needful to understand gravity.

 

 

Edited September 24 by Mordred

[Markus Hanke]

5 hours ago, Mordred said:

However there is also spin 1 and spin zero possibility for the graviton. 

I never heard of this before, and tbh I don’t see how this is even mathematically possible…? Naively it would seem to me that you can’t get the proper polarisation states in g-radiation fields with anything less than spin-2 quanta. But maybe I’m missing something.

[Mordred]

There were alternate proposals with both possibilities I recall studying a few years back when I was studying the graviton research. Often they involved alternative gravity theories as well for example

Stability of spin-0 graviton and strong coupling in Horava-Lifshitz theory of gravity

https://arxiv.org/abs/1009.0268

Spin 1 I've seen for some supersymmetry based theories. Though haven't read any for spin 1 in several years.

I agree with you on the unlikelyhood of any spin other than spin 2 but other alternatives are around lol. 

Edited September 24 by Mordred

[chron44]

 

And, for not to mention, concerning the enormous challenges discovering the proposed spin-2 graviton.

Isn't the quantum noise in any QM laboratory setup an almost overwhelming obstacle for the "clean" observation of the graviton?

Besides the lack of any present coherent and useful theory with any such graviton search.

So, the mathematics obviously have to lead in this type of research.
(And may be the only manner in which the graviton "idea" is secured.)

I would call this for the ultimate "ghost chase".

 

[Mordred]

Let's put it this way we currently have no means to directly detect gravitons due to its extremely low theoretical cross section and extremely large Compton wavelength.

This paper better describes the challenges

https://arxiv.org/abs/gr-qc/0601043

[MJ kihara]

10 hours ago, Mordred said:

the cause is the other fields acting upon spacetime via their coupling (mass terms)

Other fields acting upon spacetime producing an effect perceived as gravity,then gravity acts upon other fields... is it not a case of gravity gravitating?

Making gravity difficult to renormalize....this option don't seem to produce a solution for renormalizing gravity.

[Mordred]

Tell you what it's far easier to literally drop the word gravity. It isn't a case of gravity gravitating whatever that means.

What is perceived as gravity under GR is simply Tidal force due to curvature.

[MigL]

Whereas you can have a ToE without a graviton, it will not be as 'beautiful'.
The graviton is only a requirement for a quantum field theory of gravity.
If gravity resists all attempts at renormalization and quantization, it will have to be considered separately from a GUT, and the ToE model will no be as elegant, or useful, as one that combines all four interactions.

[MJ kihara]

23 minutes ago, Mordred said:

What is perceived as gravity under GR is simply Tidal force due to curvature.

Then linking graviton to the curvature can be an excellent thing.

[MigL]

24 minutes ago, Mordred said:

gravity gravitating whatever that means

Gravitational potential is an energy, and as such, it is a source, like momentum, stress, mass, etc.
Rather simplistic, but easily understood for those of us that don't deal with the mathematics on a day to day basis.
Also why I prefer Feynman diagrams to the integrals of QFT.

[MJ kihara]

10 minutes ago, MigL said:

If gravity resists all attempts at renormalization and quantization, it will have to be considered separately from a GUT.

????? A ToE  with  no link between standard model and general relativity?

[chron44]

4 hours ago, Mordred said:

Let's put it this way we currently have no means to directly detect gravitons due to its extremely low theoretical cross section and extremely large Compton wavelength.

This paper better describes the challenges

https://arxiv.org/abs/gr-qc/0601043

 

Tried to read this paper, and just focused on some paragraphs about noise at this type of detection attempt.

The paper is declared/preceded in this manner:

"Freeman Dyson has questioned whether any conceivable experiment in the real universe can detect a single graviton. If not, is it meaningful to talk about gravitons as physical entities? We attempt to answer Dyson's question and find it is possible to conduct an idealized thought experiment capable of detecting one graviton; however, when anything remotely resembling realistic physics is taken into account, detection becomes impossible, indicating that Dyson's conjecture is very likely true. We also point out several mistakes in the literature dealing with graviton detection and production." 

~~~~~~~~~~~
~~~~~~~~~~~

The (theoretical) answer is furthermore given on 22 pages including appendix.
Here is the paper's aspect, specifically of noise, concerning any laboratory- graviton detection setup:

Excerpt:
"This result, however, does not absolutely exclude detection of gravitons; one can imagine filling the solar system and beyond with tiny detectors. At this point, though, the possibilities go out of sight.

Before that point, we must address two other issues. The first is noise. Any detector needs to be shielded against background noise. Two serious noise sources are neutrinos and cosmic rays. The cross section for the interaction of neutrinos with matter is about 10^−45cm^2, or at least twenty orders of magnitude greater than the gravito-electric cross section. In a typical white dwarf, neutrino emission exceeds photon emission, meaning that 10^13−10^14 neutrinos are emitted for every graviton.

Therefore, without shielding, one would expect 10^33−10^34 neutrino events for every graviton event. A shield should be thicker than the mean-free-path for neutrinos, which for materials of ordinary density amounts to light years. Such a shield would collapse into a black hole. Unless one can find another way to discriminate against neutrinos, this appears to make detection of thermal gravitons impossible. In light of this result, we do not pursue shielding against cosmic rays, which would activate the detector material, inundating it with secondary particles."
End of excerpt.

The famous words of: "Huston, we have a problem.", is in this context a huge understatement. -Though the reasoning of the graviton not being "necessary" in a ToE also has to be noticed.

Concluding issue:
Is this paper really to be considered for the real physics graviton laboratory research situation?

48 minutes ago, chron44 said:

Concluding issue:
Is this paper really to be considered for the real physics graviton laboratory research situation?

 

 For to answer this issue by myself, or to guess what pro physicists will say:

Yep..!!