Is String Theory the Ultimate Theory of Everything?

[ChrisVer]

We have found no evidence whatsoever to support string theory and supersymmetry and to prove that the theory is correct.
Although the "Large Hadron Collider" has found some evidence to support the Higgs boson particle(I think they found a trace of its energy)there would still be along way to proof that the theory is right.But still,if they can find the Higgs particle it is going to be a very big thing in science.

The Higgs is "long"-found (and nobel prize won)...

 

[Sousf]

Oh,ok

 

[ChrisVer]

just to give a complete answer...
The Higgs was found, what is missing is a better significance (larger than 5 sigma) to say [experimentally] that it is found. However most of the scientists have concluded that it's found,the certainty is so large that they handed in the Nobel Prize to Higgs and Englert last year...The new run of LHC is going to get more data around Higgs and thus finish the job.

 

[Sousf]

Ok,because all the article I read only said they only found part of it but what do I'm only 14

 

[ChrisVer]

"part of it" : well you can't find "part of" Higgs. Probably you are trying to say that we have found 1 Higgs, whereas some other theories predict more Higgses, then yes that's true.
Otherwise your articles were just trying to point out the fact that we need a better signal (having greater than 5 sigma significance, and as a result of this, minimizing the statistical errors significantly).

 

[Sousf]

Ok thx

 

[ohwilleke]

The current significance of the Higgs boson discovery is currently in the vicinity of 6.8-8 sigma, well past the discovery threshold.

More importantly for the string theory discussion, SUSY theory generically predicts at least five spin-zero Higgs bosons (a light and heavy neutral scalar boson, a neutral pseduoscalar boson, and a positively and negatively charged Higgs bosons) and some predict additional sets of four. To the extent that string theory has SUSY as a low energy effective theory, the non-discovery of extra Higgs bosons narrows the parameter space and disfavors the entire theory.

 

[ChrisVer]

when did it reach 6.8-8 sigma?
Also I think it's better to replace SUSY with MSSM.

 

[ohwilleke]

when did it reach 6.8-8 sigma?

This summer.

 

[PAllen]

Though supersymmetry is but one aspect of string theory, I think the following is a really honest description of the current state of affairs, by a SUSY enthusiast of great stature:

http://arxiv.org/abs/1309.0528

While this author makes a compelling case that it is wholly premature to rule out SUSY, he makes the following admission (reflecting the need to give up either naturalness or parsimony):

"Candor compels me to declare that at this time there is no supersymmetry as
our forebears understood the term, and as they meant it to be understood by
us."

 

[atyy]

Here are some discussions of the Higgs mass.

http://arxiv.org/abs/1205.2893
Higgs boson mass and new physics
Fedor Bezrukov, Mikhail Yu. Kalmykov, Bernd A. Kniehl, Mikhail Shaposhnikov

http://arxiv.org/abs/1307.3536
Investigating the near-criticality of the Higgs boson
Dario Buttazzo, Giuseppe Degrassi, Pier Paolo Giardino, Gian F. Giudice, Filippo Sala, Alberto Salvio, Alessandro Strumia

Here are some proposals about how string theory may be consistent with the observed Higgs mass.

http://arxiv.org/abs/1206.2655
The Intermediate Scale MSSM, the Higgs Mass and F-theory Unification
Luis E. Ibáñez, Fernando Marchesano, Diego Regalado, Irene Valenzuela

http://arxiv.org/abs/1301.5167
The Higgs Mass as a Signature of Heavy SUSY
Luis E. Ibanez, Irene Valenzuela

http://arxiv.org/abs/1304.2767
The Higgs mass from a String-Theoretic Perspective
Arthur Hebecker, Alexander K. Knochel, Timo Weigand

http://arxiv.org/abs/1406.6071
Towards the Standard Model in F-theory
Ling Lin, Timo Weigand

 

[arivero]

Also I think it's better to replace SUSY with MSSM.

I think that it is more minimal to say SUSY SM, or SSM. The MSSM is one of the extensions that solves the problem of giving mass to both quark sectors. But the really minimal thing if one wants massive W and Z in supermultiplets only adds three scalars, to complete each gauge supermultiplet.

 

[ChrisVer]

if one wants massive W and Z in supermultiplets only adds three scalars, to complete each gauge supermultiplet.

do you have a reference about this procedure?
And I didn't really understand the "scalar" things. You mean chiral sfields?
Of course it doesn't sound fun to avoid adding masses to the quarks so I guess it's just a toy model. Also it won't contain the Higgs sector, and thus it's even more unphysical [I guess it's explicitly breaking the SM symmetries].
Also my interaction with MSSM was that we just took the SM and extended it to supersymmetry (each field → chiral sfield). So I didn't see this distinction to other models where you don't extend everything. Then any other extension, was NMSSM like...

 

[arivero]

do you have a reference about this procedure?.

Do you have any book on supersymmetry?

Well, for instance, Terning's. In the page 9, first line: "The massive vector multiplet... which corresponds to two Majorana fermions, a massive vector (spin 1) and a real scalar".

Of course, the massless vector multiplet has just the massive vector and one majorana fermion, the gaugino.

But if you want to have supersymmetry AND massive gauge fields, you must add to each gauge supermultiplet another Majorana fermion and a real scalar.

So any extension of the standard model where we restore susy but we keep the SU(2)xU(1) symmetry broken, which we could in principle do if susy breaking is independent of electroweak symmetry breaking, should have at least three extra real scalars, for the multiplets of Z0, W+ and W-.


EDIT: I am not sure if it contains or not the Higgs sector, but I guess that any Higgs sector will just include this three scalars, as surely when the massive gauge multiplet becomes massless it will produce a separate chiral multiplet with the extra Majorana, the extra scalar, and other scalar corresponding to the degree of freedom "eaten" by the massive spin 1 vector field. So it looks to me as a higgs.

I would be surprised if someone could exhibit a model extending the SM and not containing this three scalars, and their corresponding chiral supermultiplets. Because of it, I say that this "SSM" is the most minimal. The only way to avoid is is to build a model where susy breaking and electroweak breaking are retorted in a way such that you can not manipulate the langrangian parameters to restore susy and keep at the same time the electroweak bosons massive.

 

[ohwilleke]

I would emphasize, instead, the very narrow parameter space of two Higgs doublet models of any kind subject to very general and generic assumptions that remains given current experimental data. See http://arxiv.org/abs/1409.3199

If the two Higgs doublet parameter space is closed, then you either have the SM's one Higgs doublet (which rules out supersymmetry) or very non-minimal SUSY models within nine or more spin-0 Higgs-like particles (including charged and double charged Higgs bosons), which add an immense number of particles, forces and parameters, none of which has any experimental support whatsoever so far.

 

[KL7AJ]

I don't think we'll be putting String Theory in a test tube any time soon. Unfortunately any physicist who doesn't swallow String Theory is pretty much a pariah.

 

[Chronos]

IMO, most modern physicists tend to consider ST a pill too big to swallow. It is mathematically elegant, but, since when has that ever been considered an acceptable substitute for empirical evidence?

 

[ChrisVer]

IMO, most modern physicists tend to consider ST a pill too big to swallow. It is mathematically elegant, but, since when has that ever been considered an acceptable substitute for empirical evidence?

Since never. Who said that string theorists are looking for substitutes? Theoretically it has what it needs as you pointed out: it's elegant. Practically it's unproven (as most models beyond standard model). Nothing but it's nice content makes it strong, and in a previous post I wrote that it's main issue at the moment is advancing mathematics rather than physics. IMO if someone calls the string theory a physical theory which explains everything, then either he doesn't understand what physical stands for or what string theory is... (un/)fortunately.

 

[Ilja]

String theory at this point is not right OR wrong, it is simply a hypothesis that has no experimental evidence but which would explain a lot of stuff very nicely if it DOES turn out to describe reality.

Why would you want to abandon the search for a theory of everything? Do you not care about knowledge?

It should not be abandoned. But something should be done to reduce it to what it deserves. Namely, to the status of "wild speculations beyond the standard model".

This is more a problem of organization of science: Scientific bureaucracy should decide how many money will be give to the whole domain "speculations beyond the standard model", and these money should not be specified in any further way. Those who work in this domain should not be considered on equal foot with physicists connected with experiments, but somehow between physicists and philosophers and mathematicians, that means, with much more freedom of choice of the direction they want to work on.

 

[Ilja]

Now that's just silly. No one area of study precludes any other area of study.

In the modern, stupid way of organization of science this is a possibility.

The scientist has to be independent. What one needs for independence is quite clear: Security, that means, a safe job. You have an exceptional idea, which you want to develop yourself, but you need many years for this? No problem if your job is safe. But an big problem if your job is not safe. And an unsolvable one if the only safe thing about your job is that after two years you have to look for another one because the grant is finished.

With this stupid way of organizing science, all scientists without tenured jobs have to care about their next position. That means, to care about publications, citations, conference participations and talks, and all this. And all this is far easier if you work in the latest vogue of the modern mainstream science. And in such a situation one area of study can easily preclude a lot of other areas of study.

It doesn't even matter much what is the latest fashion - the unfashionable research directions are automatically precluded, reduced to a few individuals with tenured positions and independent scientists who do not have to care about jobs.

 

[Higgs Boson]

How did I miss this thread prior to the transition to the new board software.

:::::::::::: long pause to review my notes :::::::::::::\

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