1. Dec 17, 2017

### Haelfix

Not that I know off for the first. Yes for the second. High scale supersymmetry has interesting phenomenology. It helps with Leptogenesis, as well as inflationary and GUT scale model building. However the dark matter candidate (the LSP with R parity) must necessarily be relatively light to avoid overproduction in the early universe and so there will be a large hierarchy between that mass and the natural mass of the other superpartners. Scenarios like that have been explored quite a bit recently. Alternatively you also have models with mid scale supersymmetry (with superpartners at around the 100s or 1000s of TEV) and these naturally also provide a dark matter candidate without finetuning (the mass of the Higgs of course will be tuned at the 10^5-10^6 level). That's called split supersymmetry.

2. Dec 19, 2017

### TheOldFart

Except the multiverse isn't a theory, it's a consequence of some theories, right?

3. Dec 19, 2017

### haushofer

I've developed an effective field theory which, as solutions, has humans. But I haven't published it yet, since I only obtain women, not men, due to a lack of spontaneous gendersymmetrybreaking.

It also contains cats, so I can also explain half of the youtube content with it. :P

4. Dec 19, 2017

### star apple

Even if fairies and globlins were reality in other multi universe.. their scientists may still not be able to detect them if they have the same mindset as our scientists which are:

1. Expecting the fairies and goblins and ghosts to knock on their doors
2. Only accepting doing experiments that conform to their preconceived ideas of how nature works...and if there are massive null results.. using arguments of Unnaturalness akin to Sabine who critiqued other physicists.. but just the same, she suffered the same bias of accepting only experiments that conform to the preconceived ideas of how nature works
3. Refusing to consider the possibility consciousness or sentience can develop in subtle matter such as dark matter
4. Refusing to do experiments where these sentient beings were invoked or call upon.. or doing any experiments that involves more complexities like accessing certain information contents to cause a physical shift or result... in addition to just colliding particles like in particle accelerators
4. Promoting Shut Up and Calculate in QM and QFT and ignoring any possible ontology (which may have new degree of freedom showing up) with the results one throws the baby with the bathwater
5. Treating all witnesses to them as mentally unstable.. including witnesses to giant dark matter entities known as UFOs.. They can't consider the possibility that just like living things can come in all sizes from dinosaurs to mosquities.. so can these entities.. and for those among them like the recent Pentagon official at CNN.. who acknowledge they perform feat not possible in aerodynamics.. and falsely attributing it to alien presence when dark matter entities can produce the same trick.

So for these other universe scientists to detect them.. they need reeducation if they think like us.. lol...
Hey, it's year end yuletide vacation period and time to relax the mind and accept some humor to release the tension and stress throughout the year. Merry Christmas everyone! :)

5. Dec 20, 2017

### websterling

I would think that in a multiverse composed of a near infinite number of universes, that in some of those universes fairies and/or goblins would be required

And that in some of those universes fairies and goblins would be the scientists.

And even some globlins!

6. Dec 20, 2017

### star apple

You were assuming fresh and blood fairies and goblins in other "multiverse"? Even in physics.. we need to use the right definition to avoid confusion.. in our universe.. "fairies" and "goblins" are words to reserve creatures that are anything but flesh and blood. In my country, we mostly have so much reports of bad goblins possessing school children. This occurs elsewhere in other parts of the world too:

https://www.dailystar.co.uk/news/la...ession-priest-goblin-woman-scream-philippines

All right. You may think they are all simply deluded as this is what our physics can give us at this point in time. But note of this. Even if they are delusions, "fairies" and "goblins' were not flesh and blood in our universe. So we mustn't use the terms to refer to them as scientists in other multiverses.

This is just to illustrate semantics is important when comparisons are made or this or other multiverses (therefore this post is to clarify semantics and i'm not violating any forum rule).

Speaking of multiverses. What are good books related to string landscapes and multiverses, are they same? how do they differ?

To be scientific. Let's avoid talking about the fairies and golbins and narrow it down to multiverses and high scale supersymmetry. If there were high scale supersymmetry.. does it mean supersymmetry is still not dead?

7. Jan 1, 2018

### gdixon

Every failure to find evidence is viewed optimistically,
giving rise to a clamor for more funding and higher
energies. It was never a beautiful idea; not even pretty.
Like GUTs, it arose out of nothing more fundamental
than a desire to extend an idea (standard symmetry
gauge groups) that was at the time novel, and giving
rise to multiple Nobel prizes. As a graduate student
I was pushed very hard to commit to SUSY. I saw
absolutely nothing elegant or beautiful in the idea,
so in the end disappointed my mentors by looking
elsewhere for Dirac’s mathematical beauty.

Want to assess its value accurately? Take a vote, but
take each yes vote and divide by some measure of how
much that person’s funding and reputation will be hurt
if it fails (and how many fruitless years (nay, decades)
they’ve committed to the idea).

8. Jan 23, 2018

### Quotidian

I am not well educated in physics, but read articles about it in the popular press, New Scientist and the like. It seems that there has been no confirmation of the so-called SUSY model by the LHC since the announcement of the discovery of the Higgs Boson (although I note above that some say it's still 'out there' but we don't have/will never have enough power to detect it).

But at least some are saying that the model should be abandoned. So the question I have is this. SUSY was originally devised to solve a whole set of issues in fundamental physics, and apparently did so in a mathematically elegant manner. But if SUSY is regarded as being disconfirmed, then the issues that SUSY was supposed to be the solution for, remain as outstanding problems. What kinds of problems are they?

9. Jan 24, 2018

### Urs Schreiber

Yes, supergravity KK-models predict axions (the "B-field") generically. While standard cold WIMP dark matter models work excellently on cosmological scales, they have severe problems on galactic scales (whence "MOND"). But ultralight axions are getting much attention these days (under various names, such as BEC/superfluid/fuzzy dark matter ) since they would naturally explain a phase shift of behaviour that dark matter (if any) needs to exhibit at around the scale of galaxies.

See Hui-Tremaine-Ostriker-Witten 16 between equations (3) and (5).

10. Feb 15, 2018

### Martin0001

Nothing new up to 10^16 GeV, maybe up to 10^19 GeV. So new physics might be there but under event horizons.
OK, we are not building any particle accelelators size of Solar System (to get 10^16 GeV) or hundreds of light years across to get 10^19 GeV anytime soon.
Boys, time to pack your toys and go home on dinner. Mama is calling. Nothing to see here.

11. Feb 15, 2018

### bluecap

In 1 Billion A.D. Can we already reach 10^16 GeV or say 3 Billion A.D.? How many billions of years later before we can probe the planck scale?

Anyway. A hundred years from now.. when building more accelerators would no longer be viable due to financial, environment, political or military catastrophe. Can we at least do one last experiment never before tried (at least officially)...

There may be a Particle Desert where nothing occurs below 10^16 GeV and above those already explored. So let the last final experiment be about testing non-thermal based symmetry breaking. Perhaps all those missing particles would suddenly popping up. In many unofficial experiments now. They detected exotic particles even monopoles by initiating non-thermal phase transition but no other scientists want to even try duplicating any of it. So before we dismantle the last particle accelerator on earth and before the last particle physicists get into other fields like banking or telecommunications industry.. can we at least try this one last experiment? Perhaps we would see results the world has never seen before..

12. Feb 16, 2018

### Urs Schreiber

Interesting to read Gordon Kane, who keeps going all in with yesterday's

Exciting implications of LHC Higgs Boson Data
(arXiv:1802.05199)

The content is not entirely new, in itself it seems to be a (somewhat hasty) writeup of a talk given already in January 2017 on occasion of Kane receiving the Sakurai prize 2017 "For instrumental contributions to the theory of the properties, reactions, and signatures of the Higgs boson."

The prize announcement knows that "Dr. Kane made important early contributions to the study of the Higgs Bosons, including an upper limit on the Higgs boson mass..." (this refers to his bold claim of a Higgs mass prediction via the $G_2$-MSSM in Kane 11, a useful informed comment is here), "...to the study of dark matter and its detection and to string theory phenomenology. His more recent work has been in the development of testable models based on string theory, in particular those based on $G_2$ compactifications of M-theory, a predictive approach that explains the hierarchy between the weak scale and the Planck scale. Dr. Kane has argued that these ideas form a consistent framework with a non-thermal cosmological history of the universe."

The article discusses four "clues" obtained from the LHC data and argued to be clues for the presence of low-scale supersymmetry. The third clue claims that some model of low scale susy is still consistent with observation, the first clue recalls that the observed Higgs mass is close to the upper limit constrained by low-scale susy, while the fourth clue claims that the observed Higgs potential is inconsistent without low-scale susy, which would cure the apparent vacuum instability.

I suppose that whether or not low-scale susy is the answer, there is a point to be made, re the fourth clue, that the apparent vacuum instability of the experimentally observed Higgs potential is in contrast to the often heard claim that "nothing new or interesting" for HEP has come out of the observation of the Higgs at LHC.

13. Feb 16, 2018

### bluecap

Very hopeful and encouraging.
Just a question Urs. Is there no existing work or papers about non-thermal symmetry breaking or phase transition whether in the quantum fields, quantum vacuum, spacetime or other stuff? If there is. What is the technical words used for non-thermal symmetry breaking. To illustrate the point. For the electroweak. We need very high temperature to put the symmetry back into place just like what we are doing at particle accelerating by colliding particles and reproducing the high temperature. Is there any concept where you can put the symmetry back into place for other particles by non-thermal means? If none. Why is it not possible?

14. Feb 16, 2018

### Urs Schreiber

By the way, the text has a bit of overlap with that of his book
where it corresponds to sections 5.1 and 6.4.

Hm, it seems to me that the bulk of the literature is about supersymmetry breaking in non-thermal contexts. A few authors discuss thermal supersymmetry breaking, for brief exposition see for instance
• Claudio Lucchesi,
"Symmetries at finite temperature"
in F. Gieres et. al (eds.)
"Symmetries in physics"
Edition Frontieres (1997)
There is maybe some care advised regarding the difference between invoking high tempterature to argue that a system has high energy and having a genuinely thermal description, usually referred to as "QFT at finite temperature". The latter requires more work and is considered by fewer authors.

15. Feb 17, 2018

### bluecap

I was asking whether you can have a new gauge-like field or fundamental force (not electroweak or strong) that has similar symmetry breaking as SUSY breaking not dependent on spontaneous symmetry breaking (or Big Bang scale gauge fields) but could be for instance gravity or anomaly mediated (as applied to SUSY symmtry breaking see https://arxiv.org/pdf/hep-th/0601076.pdf) ... or in other words, are soft gauge-like forces possible also by some SUSY-like vacua dynamics?

I'm aware of the difference between gauge and susy symmetry breaking from http://people.sissa.it/~bertmat/lect7.pdf

Can you design a fundamental force of nature that has same symmetry breaking mechanism as proposed for SUSY and can initiate symmetry breaking far below the weak scale or even low energy?

16. Feb 17, 2018

### Urs Schreiber

The fact that positive vacuum energy reflects spontaneous supersymmetry breaking is a direct consequence of the fact that local supersymmetry is an extension of local Poincaré symmetry, hence of gravity. Technically, this is because the stress-energy tensor $(T_{\mu \nu})$ in supersymmetric field theories is the image of the supersymmetry Noether's conserved current $(S_{\nu \beta})$ under the super-Poisson-bracket with the supercharge $(Q_\alpha)$

$$T_{\mu \nu} \;=\; \gamma_\mu^{\alpha \beta} \{Q_\alpha, S_{\nu,\beta}\}$$

so that the vacuum expectation value of the stress-energy tensor is

$$\langle vac \vert T_{\mu \nu} \vert vac \rangle = \gamma_\mu^{\alpha \beta} \langle vac \vert \{Q_\alpha, S_{\nu,\beta}\} \vert vac \rangle$$

which hence vanishes if the vacuum state is supersymmetric, hence if supersymmetry is not spontaneously broken.

So the specific nature of spontaneous supersymmetry-breaking is a reflection of the special fact that (local) supersymmetry is an odd-graded extension of (local) Poincaré-symmetry, hence of gravity. Symmetries not related to gravity in such a way cannot show this effect.

I recommend going to the original articles, such as Witten 81, section 2. The graphics that you reproduce above originates in Fayet-Ferrara 77, Fig. 1 on p. 286 (38 of 86).

17. Feb 17, 2018

### bluecap

What range of energy in TeV do you think the Superpartners can be lurking?

Also is there a possibility or mechanism (complex as it may be) for the supersymmetry be between normal matter and mirror matter (these being direct counterpart of all our baryonic particles but only right handed and form perhaps 5% of the dark matter sector? See a thesis about cosmology and mirror universe... https://arxiv.org/abs/astro-ph/0312607

Perhaps each is in different vacuum or spacetime boundary or the thousands of mechanisms or possibilities or variants of models physicists can easily write such as for example in ArXiv?

18. Feb 18, 2018

### Urs Schreiber

This I am really not the right one to ask or answer.

I do take interest supergravity, on the grounds that it has excellent theoretical motivation, and I appreciate the curious fact that KK-compactifications to 4d that preserve global $N=1$ supersymmetry happen to be those that are mathematically rich (CY-geometry, $G_2$-geometry), whatever that may be telling us; but I notice that there seems to be no theoretical reason why these compactifications should be dynamically preferred, and that the folklore of their phenomenological motivations (hierarchy problem, gauge coupling unification, naturalness) is based on an essentially numerological attitude only.

This makes me want to recall that:

"The alternative to naturalness, often neglected as an alternative, is having a theory."

which is a great sentence that one finds in Kane 17, p. 56 (6-10).

Now Kane of course does assume $G_2$-compactification, which, while certainly interesting in itself, seems to be lacking a dynamical explanation from within the theory; but that granted then the great achievement of him and his collaborators is that, based on this single assumption, they first of all try to and then to a remarkable extent succeed with working out the theoretical consequences systematically, by analysis of the theory. Even if the result eventually disagrees with experiment, we will have learned what the generic predictions of this model are, hence will have learned something tangible about 11d supergravity and its UV completion, while from much of the unsystematic by-hand susy model building entertained elsewhere we will possibly have to conclude in 50 years time to have learned little, besides the lesson that physics unconstrained by theoretical framework becomes arbitrary.

One of the theoretical insights that Kane and collaborators have been amplifying is that in this model the gravitino mass after susy-breaking sets the scale for the moduli and the superpartners, such that, in the words of Kane 17, p. 43 (5-1), the upshot is this:

"When supersymmetry is broken the gravitino becomes massive — the splitting between the graviton (always massless) and the gravitino is a measure of the strength of the supersymmetry breaking, and it sets the scale for all the superpartner masses.

"It is important to understand that there are two measures relevant to understanding supersymmetry breaking, one the scale at which it is broken (about $10^{14}$ GeV as described above), and the other the resulting gravitino mass. In the compactified M-theory case the gravitino mass is calculated, and comes out to be about 40 TeV (40 000 GeV). Sometimes even experts confuse these two scales if they are speculating about supersymmetry breaking without a real theory to calculate.

"Thus 40 TeV is the natural scale for superpartner masses. That is not a surprising number in a theory starting with everything at the Planck scale, but it is surprising if one expects the superpartner masses to be near the particle masses (all well below 1 TeV). The squarks and other masses are indeed predicted to be at the gravitino scale, tens of tera-electronvolts."

"The theory has formulas (‘supergravity formulas’) for all the masses. When one calculates carefully the masses of the superpartners of the gauge bosons that mediate the Standard Model forces they turn out to get no contribution from one large source, and the resulting value for the superpartners of the gauge bosons (gauginos) is about 1 TeV, rather than about 40 TeV. They are the gluino, photino, zino, and wino. The strong force gluino is heavier, about 1.5 TeV or somewhat more, and the electroweak ones (photino, zino, wino) are somewhat lighter, about half a tera-electronvolt. The lightest superpartner, which is important for how to detect the signals at the LHC and for understanding dark `matter, will be a combination of the electroweak ones, and thus about half a tera-electronvolt in mass. All of these are observable at the LHC in the run underway through 2018. That run is supposed to collect an amount of data measured in units called inverse femtobarns ($fb^{-1}$). At the time of writing (December 2016) it has collected about $40 fb^{-1}$, and is into the region where we can hope for signals of gauginos. The goal for the LHC is to collect $300 fb^{-1}$ through 2018. Without a detailed theory to calculate with, we would not have had serious predictions for masses."

(from Kane 17, chapter 5).

19. Feb 18, 2018

### ISamson

My father used to study and research Supersymmetry.
We were talking, and he was saying that the field is dying out. Now, he studies dark matter and energy with another professor.
Just what he told me.

20. Feb 18, 2018

### Urs Schreiber

Sure, that's a truism after the LHC results did rule out most of what people in the field had claimed would be seen.

On the other hand, just as an idea being fashionable does not make it true, so an idea being unfashionable alone does not make it false. The truth is more subtle than the common sport-event-like attitude towards it may indicate.