chron44

If I may have some idea or vague opinion (being a layman in physics), is that the "construction" of nature (the physics part especially discussed) is fully dependent on how the universe truly is originated. The cosmological origin and further development set all such linear and non-linear, and other mathematical behavior by the original premises. I.e. if the BB is the cosmological origin, which much points on, the SM, QFT and the GUTs' among other BB sprung theories and its mathematics, all are part of the BB universal evolution line. Thus, this thread being a ToE parameters scrutiny also alternative cosmological origin ideas must be considered. Therefore, when GR have been verified so many times, this does NOT by automatics to 100% secure the BB cosmological evolutionary origin. And for to sum up my maybe a bit "easy and naive" arguing the "correct" cosmological origin does set the "fundamental thing about nature" where the "verified" GR may also suite different evolutionary lines.

Have in a layman’s manner tried to comprehend how GR works in an elementary manner. Can one easily describe adding mass and/or energy to a vacuum energy volume behaves like this? “I understand that G here is a very important constant (doesn’t change and sets the initial condition) and that the gravitational energy field is affected if mass or energy or both becomes present. One must hence note that the E=mc^2 very much influences the overall rise in this total resulting gravitational energy. -Like this famous "formula" is affecting all involved parts, the mass, the energy and the gravitational field in an intricate manner. In this way the spacetime “fabric” is altered and contributes to GR calculations being non-linear. Does this also mean that the energy related to only the gravitational field to a very extremely small extent is adding energy towards the present mass and energy? Yes, it does. “-Just like the dog is chasing its own tail”. 🙂 In this way it becomes hard to know how the total energy becomes configured. -Especially in extreme astrophysical conditions.” The underlying thought in this GR “statement” is the chase or hunt for the mystic G, the gravitational constant. Which must be an important part of a ToE’s parameters. (If I may alter a bit on the last posts focus.)

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

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".

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.

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?

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.

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?

The reason is probably given why professional physicists tend to await any graviton confirmation, before even lifting the thought on any ToE. Hypothetical, in combination with extreme small energy and massless property. Like chasing ghosts... : )

Yes, of course, the graviton still is hypothetical. I didn't express myself clear enough. Still my intention with the latest post was to point out the theory of it; and some observations, LIGO and the one you mentioned, "showed" on the main characteristics for this proposed particle being probable. -And, here a most delicate situation emerges. Todays and the most ahead years of physics laboratory tech cannot provide any existing or non-existing status for this particle. This insecure status of the graviton idea will stall any further ToE research for many years ahead. With this reasoning any serious ToE arguing will fail. (Until the graviton's existence is confirmed. Or proven to be of a different construction.) So, ToE is halted.

The parameters to a ToE obviously have to incorporate gravity, of course. Which for the moment doesn't easily (not all all?) merge with QM. So here we, that "all" are aware of, stand with separate QM and GR. Though the detection by LIGO in 2015 did in some manner "reveal" possible internal structures and necessary conditions for gravity: * Being massless * Propagating at c * Probably existing in the entire known universe Which leads to the graviton existence proposed by the main physics community, maybe not the entire.

There was also a post from me (which disappeared) about one central marker of why GUTs are involved in a TOE speculation. And that is the detection of proton decay which is postulated from any (some?) GUT. -Still during about of 40-50 years of search no proton decay whatsoever have been detected. Where Mordred did replay (not exactly but informatively) of that the GUT calculus estimated the proton lifetime till over about 10^35 years, being the reason of no to date detection, as the age of universe being about one third of that age. So the GUTs still being on the track.

Have read a bit more physics... The GUTs (Grand Unification Theories) are based on very high energy systems, which should need a BB type of very/ extremely hot universe or a similar universal original evolution. In some manner the confirmation of any GUT would be a parallel indication of the BB besides the CMB radiation detection.

This is also fetched from Chat GPT: "When, GUTs are deeply connected to the Standard Model: -The cosmological constant problem and the non-observation of proton decay, looks like central challenges that have not outright disproven GUTs or the Standard Model but, have highlighted significant gaps in these theories." Can anyone comment these central discrepancies?

If a GUT is to be considered for ToE. One crucial issue becomes. How long can physics "wait" till a proton decay is noticed? -And therefore reasonably prove a GUT being the manner in which universe works? Have there been physicists who claim this period being fulfilled? ???