Loop Quantum gravity or String theory?

[areehantgupta]

TL;DR

Which do you believe in?

I understand that string theory has almost no testable predictions, however loop quantum gravity is an enticing candidate for only quantum gravity and it doesn't explain much of symmetry, constants, mixing angles etc in Standard model. There is obviously not enough evidence to create a full assumption, however what should I believe and why?

 

[weirdoguy]

what should I believe and why?

I think to "belive" in anything you should know these models on a more technical level. I don't "belive" in non of those, but I guess if I had to choose I would say that LQG, because I wrote my bechelor thesis on some toy model in LQG (Jerzy Lewandowski, one of the more known people in the field of LQG, was my supervisor).

 

[strangerep]

what should I believe and why?

Let go of (all) your "beliefs" (difficult though this is). Embrace scientific method. Trim any excess with Occam's Razor.

 

[Demystifier]

I believe that string theory could at least be a theory of something. For LQG I am very skeptical, because it seems to give wrong results even for a harmonic oscillator https://arxiv.org/abs/hep-th/0409182v1

 

[*now*]

I believe that string theory could at least be a theory of something. For LQG I am very skeptical, because it seems to give wrong results even for a harmonic oscillator https://arxiv.org/abs/hep-th/0409182v1

Even though ways that that older pathway in LQG took back in 2004 are less interesting to me, perhaps this paper could also be mentioned https://arxiv.org/abs/hep-th/0608210

…”calculation in a recent paper by Helling et al [hep-th/0409182] are physically incorrect”.

 

[*now*]

This, from last month, is far more up to date. (I also noted in the comments skydivephil mentions having been less active at physics forums recently)

 

[phinds]

I understand that string theory has almost no testable predictions

Why is the word "almost" in that sentence?

 

[Demystifier]

…”calculation in a recent paper by Helling et al [hep-th/0409182] are physically incorrect”.

Thiemann discusses only in the conclusion, but his argument did not convince me. Roughly speaking, he says that Helling's conclusion is physically wrong because mathematically it is correct but trivial.

 

[physika]

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None.

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[*now*]

Thiemann discusses only in the conclusion, but his argument did not convince me. Roughly speaking, he says that Helling's conclusion is physically wrong because mathematically it is correct but trivial.

My impression is the trivial nature involves a strawman case where the literature’s relevant physical concepts weren’t addressed, and again, it concerned an older path 18 years ago, but the youtube debate between experts in strings and loops above, however, is just weeks old.

 

[ohwilleke]

Two main points.

First, this isn't an apples to apples comparison. String theory is a theory about something different than LQG (which less ambitiously addresses only gravity and not all forces at a naive level).

Second, you shouldn't "believe" either because neither are proven physical theories, and neither is a fully fleshed out theory that makes predictions for all matters within the ultimate domain of applicability that the theories seek to prove. It is entirely possible that the truth is neither of the above. But, even if one or the other of them are correct (or their are somehow equivalent in ways not currently apparent), we don't know enough to know right now.