## Thursday, November 14, 2013

### State-of-the-art non-SUSY $$SO(10)$$ grand unified models

Several recent hep-ph papers studied grand unification without supersymmetry, an approach that seems intriguing to a whole group of researchers. Grand unification theories (GUT) work nicely with supersymmetry (SUSY) – it's the supersymmetric version of the $$SU(5)$$ and larger models that achieves the accurate unification of gauge couplings of the $$U(1)_Y$$, $$SU(2)_W$$, and $$SU(3)_c$$ factors of the gauge group in the simplest, most natural way.

Super-Kamiokande has looked for a proton decay, a flagship prediction of grand unified theories

However, SUSY hasn't been experimentally proven yet so it's a legitimate possibility – at least from a phenomenologist's viewpoint – that SUSY isn't relevant for any low-energy phenomena (or isn't relevant for Nature at all). The Standard Model is a bit awkward, with its diverse groups and fragmented representations, so one should better unify those structures a little bit.

The people behind the papers below tend to assume that Nature needs a grand unified theory, the symmetry breaking is achieved by the ordinary Higgs mechanism (pure field theory, no stringy Wilson lines etc.), and a precision gauge coupling unification is achieved in some way, too. They typically require a dark matter candidate, too: it's usually an axion. GUT theories may imply lots of unobserved decays of particles (especially the proton decay) so the null results of all these experiments kill many GUT models and constrain the parameters of others.

Yesterday, C.P. Martin of Madrid released the paper
$$SO(10)$$ GUTs with large tensor representations on Noncommutative Space-time
which argued that a recently proposed grand unified model is even more natural when combined with spacetime noncommutativity and reinterpreted in terms of a Clifford algebra, namely $$\CC\ell_{10}(\CC)$$. I was initially intrigued but I couldn't understand what becomes nicer if the noncommutativity is added to the game (except for some new allowed interactions [e.g. Higgs' interactions] which follow from the broken Lorentz symmetry and I would call this loosening a vice, not a virtue). And much like in the case of most physics papers that place the phrase "Clifford algebra" at a prominent place, I just don't see any beef behind the phrase.

It seems to me that these people love to write the phrase "Clifford algebra" or the Greek letter $$\Gamma$$ and that's it. It doesn't seem to me that anything linked to this mathematical structure is "exploited" in any physical way at all. At most, Martin noticed that the representations used in the model he promotes may be found in the decomposition of a bispinor of $$SO(10)$$ – I mean the tensor product of a Dirac spinor with itself. That's great, it's a justification making these representations natural – but why is there so much ado about the "Clifford algebra" there? I have no clue.

Martin's paper uses the May 2013 model by Guido Altarelli and Davide Meloni (AM),
A non-supersymmetric $$SO(10)$$ grand unified model for all the physics below $$M_{GUT}$$,
which I will discuss for a while. At the end, I will mention a grand unified paper released today, too.

AM are extending the Standard Model and a possible strategy to plan a presentation of this model is the bottom-up approach, i.e. one starting at low energies.

First, let us look at the gauge groups and their breaking patterns.

Below the electroweak scale $$v=246\GeV$$, we have the gauge group$SU(3)_c\times U(1)_{\rm em},$ the QCD color group and the electromagnetic Abelian group. As we know very well, this is just an unbroken subgroup of a larger group operating above $$v=246\GeV$$, namely the Standard Model group$G_{SM} = SU(3)_c\times SU(2)_W\times U(1)_Y$ which includes the electroweak $$SU(2)$$ and the hypercharge $$Y$$. The breaking from the Standard Model group to the QCD+electromagnetism group is achieved by a Higgs doublet. This statement is pretty much an experimental fact by now, a Nobel-prize-winning one. In this grand unified model building, we ultimately want an $$SO(10)$$ symmetry at really high scales so all fields, including the Higgs fields, have to be embedded into full representations of $$SO(10)$$.

The simplest representation of $$SO(10)$$ that provides us with the Nobel-prize-winning Higgs doublets is a $${\bf 10}$$, the fundamental vector of $$SO(10)$$, decomposing as${\bf 10}_H \to ({\bf 1},{\bf 2},{\bf 2}) \oplus ({\bf 6},{\bf 1},{\bf 1})$ under the Standard Model group. The symbol for the singlets and doublets is obvious; the 6-dimensional representation is the symmetric tensor of $$SU(3)$$ (note that due to the complexity of the group, the "trace" cannot be separated like in $$SO(3)$$).

Great. Now we're above $$v=246\GeV$$ and continue to raise the energy. AM are telling us that there is an intermediate scale, something like $$10^{10}\GeV$$, where a larger group gets restored. The intermediate energy scale may be adjusted so that the gauge coupling unification is restored with the same precision we know from the simple SUSY GUTs. This is a bit ugly – we have to adjust one real parameter (the energy scale) to guarantee one real condition (the second coupling and the third coupling unify with the first one at the same energy scale) – but there's no guarantee that all types of unification that Nature manages are "breathtakingly beautiful and rigid".

Fine. So above the intermediate scale, the gauge group becomes larger, namely$G_{PS} = SU(4)_c \times SU(2)_L \times SU(2)_R.$ We have enhanced the color group to $$SU(4)$$, i.e. added the fourth basic color (it's like going from RGB to CMYK, if you like silly analogies). The electroweak $$SU(2)_W$$ group was kept and just renamed to $$SU(2)_L$$ because it couples to the left-handed fermions. And the hypercharge was extended to an $$SU(2)_R$$ group where "R" stands for "right".

The group above has been known as the Pati-Salam group. It's a "partial unification" group because the number of factors is the same as it is in the Standard Model but at least the smaller two factors became isomorphic to one another and may be related by a discrete symmetry.

This Pati-Salam group is broken to the Standard Model by some Higgs fields analogous to those in the Standard Model. The quartic and quadratic interactions are analogous, just the group theory is a bit more complicated. The required Higgses transform as $\overline{\bf 126}.$ What is this representation? Well, consider the antisymmetric tensor field with five indices, $${\bf 5}\wedge {\bf 5}\wedge {\bf 5}\wedge {\bf 5}\wedge {\bf 5}$$, if you wish. Its dimension is $\frac{10\times 9\times 8\times 7\times 6}{5\times 4\times 3\times 2\times 1} = 252$ but one may also "Hodge-dualize" this tensor field with a 10-index "epsilon symbol" which allows us to split this 252-dimensional representation to two 126-dimensional ones, the self-dual and the anti-self-dual ones, which are complex conjugate to each other.

This tensor field $$T_{abcde}$$ may remember which 5 of the 10 (complexified) directions in the $$SO(10)$$ vector are the "holomorphic" directions of the fundamental 5-dimensional representation of $$SU(5)$$ and which of them are the antifundamental ones. Consequently, this field might break $$SO(10)$$ to $$SU(5)$$.

However, when we start with the Pati-Salam group instead of $$SO(10)$$, it's also able to break the group to the Standard Model group. The group theory is not too complicated and we actually need a Higgs field in another representation, $${\bf 45}$$, as well. This is the antisymmetric tensor with two indices, $${\bf 10}\wedge {\bf 10}$$, if you wish, with dimension $$10\times 9/2\times 1 = 45$$. Such a field simply picks a preferred complex 2-plane inside the 4-dimensional space symmetric under $$SO(4)=SU(2)\times SU(2)$$ and this complex 2-plane is the one that preserves the $$SU(2)_L$$ symmetry.

Finally, there's another scale, the highest one: the GUT scale. Above the scale, $$SO(10)$$ is restored. Beneath the scale, it is broken to the Pati-Salam group. The breaking is done by $${\bf 210}_H$$, an antisymmetric tensor with four indices whose dimension is understandably$\frac{10\times 9\times 8\times 7}{4\times 3\times 2\times 1} = 210.$ Now, there is no Hodge duality. Note that all these antisymmetric tensor products of copies of $${\bf 10}$$ may be found in the tensor product of two spinors, $${\bf 16}\otimes {\bf 16}$$, of $$SO(10)$$, except that sometimes we need the same chirality and sometimes we need the opposite chirality of the two 16-dimensional spinors. That's also the case of the 120-dimensional antisymmetric tensor with three indices that is not used in this construction.

It's easy to understand why $$SO(10)$$ may be broken to the Pati-Salam group by the antisymmetric tensor with four indices. It defines a volume form for 4-dimensional submanifolds of the 10-dimensional space so it splits "ten" to "four plus six" and $$SO(6)=SU(4)$$ while $$SO(4)=SU(2)\times SU(2)$$ which produce all the factors of the Pati-Salam group.

So the representations used in the AM paper have dimensions $$10,16,45,126,210$$ where $$16$$ is the usual "single generation of fermions" including an active right-handed neutrino. The 120-dimensional representation isn't used in this particular grand unified model (it is used in other $$SO(10)$$ models, however) while the 45-dimensional representation is used and produces an axion, a dark matter candidate. If dark matter is composed of axions only, the underground experiments will probably find nothing, at least for quite some time.

They discuss many features of the model and show it is viable. They also identify 15 high-scale parameters that are pretty much manifested as 15 parameters of the Standard Model. (My understanding is that the Higgs quartic couplings etc. are assumed to be irrelevant in all this fitting; they don't seem to know anything about their values.) Their best fit (see an appendix in that paper) leaves no freedom and you may see that the Standard Model with the required values of the parameters may be realized within their model. Some of the "best fit" values are extremely unnatural (tiny) numbers, highlighting the fact that grand unification without SUSY seems more awkward than one with SUSY.

However, it seems that aside from the gauge coupling unification and a dark matter candidate, they also manage to suppress all the dangerous decays of various particles that rule out many other generic GUT models.

Today, a Spanish-Portuguese-Czech collaboration (Carolina Arbeláez, Martin Hirsch, Michal Malinský, Jorge C. Romão: AHMR; I have never met Michal Malinský, I believe) released another non-supersymmetric $$SO(10)$$ grand unified paper,
LHC-scale left-right symmetry and unification
AHMR study not just one grand unified model but a big class of models "similar" to the AM model above. They have some intermediate left-right (Pati-Salam) gauge group and the condition of gauge coupling unification is imposed.

AM adjusted the Pati-Salam scale to be an intermediate one; it was needed for gauge coupling unification. AHMR do something else. They show that in many models, the Pati-Salam scale may be brought down, close to the LHC scale so that there's no continuous adjustment needed to restore the gauge coupling unification.

However, what's needed as an extra price to pay are new multiplets of matter – which should or might be accessible by the LHC. They seem to conclude that to guarantee a long enough lifetime of the proton that is compatible with the current lower bound of order $$10^{34}\,{\rm years}$$, or at least to respect this lower bound "safely", most of their models need to add new colored states at the LHC scale. That would be very exciting, of course (although arguably less exciting than an experimental discovery of SUSY), if such new GUT-predicted states were found.

1. Dear Lubos, Even though I may not understand all the math, I love the grammar of this exposition. Nature looks beautiful even to the uninitiated.

2. kashyap vasavadaNov 14, 2013, 5:23:00 PM

Dear Lubos: I do not yet understand all the details of your blog. But, since electro-weak unification has been already achieved, there may not be any choice but to work on a GUT theory. There may not be any alternative. I do not know if such non-SUSY models with some extra complications of non-commutativity are any better than SUSY at extremely high energy. But then, if I understood your answer to my question on one of the previous blogs,SUSY at extremely high energy may not serve the original purpose anyway. Is that right? Are we stuck? Comments please.

3. Dear Kashyap, grand unification isn't really "inevitable".

The original purpose of supersymmetry is to allow the existence of fermions in a theory of quantum gravity (string theory) - and also to eliminate the tachyons and restore some degree of the vacuum stability - and supersymmetry plays these two roles regardless of the scale at which it is broken.

I don't know what you imagine under the word "stuck". Science is always in the process of being sure about the established things and unsure about other things. The fact that the questions drift from the latter group to the former group is the reason why science is never properly described by the word "stuck".

4. kashyap vasavadaNov 14, 2013, 5:41:00 PM

Thanks. OK. The word "stuck" is too strong. But the current status seems more and more similar to confusions in physics at the beginning of 20th century. We did come out of that! BTW I would like to read about non GUT way out. A blog will be very useful.

5. I don't understand what blog you would like to see but I probably fundamentally disagree with you on the substance.

The early 20th century wasn't any era of "confusion" in my eyes and surely not an era of "being stuck". It was an era of some really crisp insights that were viewed as modest modifications of their picture of physics but within decades, they grew into something fundamentally better.

6. kashyap vasavadaNov 14, 2013, 5:54:00 PM

Ok. I see your point. Thanks.

7. A new computing language then? If it is simple I'm all for it. ;-)

8. kashyap vasavadaNov 14, 2013, 6:17:00 PM

Sorry. These questions come from my non-understanding of ST. I was curious about your statement " in a more general, stringy way that also includes gravity (this kind of
stringy unification may look highly non-unified from the viewpoint of
any effective field theory).
If it is explicitly possible to elaborate this point, then you might. Otherwise I got the general idea. Thanks.

9. Dear Kashyap, string theory as a theory unifies all forces including gravity. So any vacuum of string theory - any Minkowski-space-like solution to string theory's equations - does the same thing.

In field theory, the unification means a simple thing - the equality of the gauge couplings (if they are properly normalized) and the embedding of gauge groups into larger, simpler groups.

In string theory, gauge groups are always unified in a more general sense because they're derivable low-energy effective features of a string vacuum and string vacua always unify everything.

So the gauge couplings may differ and there may be no "all-encompassing" larger group, but all the gauge couplings are still rigid in any stabilized stringy vacuum. So the relationships between all such parameters in low-energy effective theory may be viewed as a consequence of some more complicated,stringy unification. The inequalities between couplings may be interpreted as a reflection of objects' being in different places of the compact dimensions or their generalizations.

It's hard to "elaborate on some point" if you don't really say what point you mean. It's hard to answer your questions if you don't really say what the question is, or if the question makes no sense. My original claim was completely transparent. There was nothing missing. If there's no gauge unification, there's no unification. What do you really want to elaborate here?

10. The Georgi–Glashow model suggested "at least" 10^31 years for proton half-life. Super-Kamiokande gives 90% confidence lower limits for no proton half-life less than 6.6×10^33 years via antimuon decay and 8.2×10^33 years via positron decay. Via positron decay has been updated to 1.29×10^34 years. SUSY was "recalculated" to predict 10^36 years via proton decay to a positron plus neutral pion. Hyper-K, being 20× larger than Super-K, will falsify that.

The universe as it occurs does not crunch numbers. A rigorously derived theory that affords empirically invalid outputs is self-consistently wrong. Try different protons! A megatonne of H_2O is 1.11×10^11 moles of rather ionic protons. A megatonne of CH_4 is 2.49×10^11 moles of rather covalent protons, mp = 91 K, d = 440 kg/m^3 at 98 K. Same volume for a given number of protons, much lower photodetector thermal noise. Fossil fuel methane is wholly decayed - plus carbon credits for sequestering 2.74 megatonnes CO_2-equivalent.

11. kashyap vasavadaNov 14, 2013, 6:59:00 PM

I see your point. I will try to digest what you are saying. For the time being it is OK. May be there is no real alternative to technical reading !You are the only resource for technical questions on theoretical physics! Other blogs are too wordy and non-technical. Thanks.

12. Brian G ValentineNov 14, 2013, 7:06:00 PM

For the function zeta(1/2 + it) I want to use this new language on new Google quantum computers to check the zeros of this function near logloglog(t) about 5.

I hope this new language knows how to minimize errors associated with quantum computing

13. Well, I could give a better question and maybe a subject for a blog... I won't ask to discuss all the points where string theory is using some "hand-waving" arguments but let's start with compactification, first in the mathematical sense and then in the sense accepted by string theorists: Mathematically it is quite a common feature. In principle it means making some space "compact". This is done generally either by adding points at infinity or defining some margins and ensure that maps do not bring points to "infinity". About the stringy part of the problem, if one considers heterotic strings as the main "candidate" for anything connected to the standard model then SUSY must be unbroken at compactification scale (at least for N=1 SUSY). Then one has to add D branes... now, D branes were initially invented (in a rather unimaginative way) in order to allow for Ramond-Ramond boundary conditions and in fact Ramond-Ramond fields can be considered because D-branes are their sources. Now, these RR fluxes can break SUSY at the required level but then again, there is no rule for why there should be fluxes, when, etc. All constraints considered only from geometrical perspective do not allow a specification strong enough to result in anything like what we see around (although something similar might exist). Now let's go to the no-go theorems : in essence these imply necessity of localized sources in order to get to anything like Minkovski or DeSitter spacetimes. These are of the form of "orientifold planes"... now... this is a very vague and short introduction to flux compactification where I might have forgotten or skipped some details but is there a reason why all this is necessary? I agree with all the theorems that say the results are consistent and correct but I never saw a theorem stating that this or that solution chosen at one step or another is the only one. All I see is that nobody came with anything else, and the reason for this is not necessarily scientific, it is more related to science politics... This is why I ask: can a string theorist really tell me that this is the only way to go? Can they prove they covered all loopholes and found out all possible alternatives? Eliminating a requirement from a no-go theorem is the most obvious way of generalizing a theorem, but it is not the only way. I think what is missing is some all-encompassing principle or law of nature or mathematics that would make all this "patching" of the theory superfluous. Maybe this is why thinking in the context of black hole dynamics or thermodynamics or entanglement and quantum gravity is a better approach, simply because we have more intuition for that ...

14. it is, simply stated, arrogance to say that your way (not yours, Lubos, I speak generally about physicists and the way they write or present their work and in the end, the way they learned to think) is the only way... Do you really think the planck-telescope anisotropy is the ultimate proof for parallel universes? Is that the *only*, *unique* explanation possible in the whole wide world, as the author claims??? And there are hundreds of assumptions of this kind. About string theory: I like it! I really do, it is a great idea and it deserves a better understanding, but with far less arrogance...

15. Nah, to find legitimate alternatives, loopholes, and things not thought of is maybe what we have mathematicians for to help with ... ;-P ;-)

Cheers

16. Dear Andrei, there's so much confusion in your comment that it is impossible to "answer" this comment in any meaningful way.

There is no handwaving about compactification. Compactified vacua or solutions - with the spacetime having the form of a product of a compact manifold and a noncompact known spacetime - are as good solutions as any fully decompactified ones, according to the precise, totally rigid rules of string theory (conformal invariance on the world sheet it is in the perturbative limit).

There are no D-branes, RR-fluxes, and orientifold planes in heterotic string theory at all so 1/2 of your comment discussing these objects in heterotic string theory is utterly deluded, too.

These objects exist in type II string theories and they're as good parts of solutions of the stringy equations as other objects. Your complaining about these things or suggesting that they are "politics" is *exactly* as idiotic as suggesting that the 2s state of the hydrogen atom is just politics. Everyone who knows what the equations/conditions of string theory are and why the objects you try to stigmatize solve them know it as well as I do that your ideas are completely idiotic conspiracy theories.

17. I don't think that there is any proof of parallel universes and the people claiming those things by looking at the Planck telescope data aren't quite up to their job, but I do recognize a small risk/probability that I am wrong.

18. I'm still scratching my head, wondering whether this is serious or an example of ultra bone-dry, wicked humor ... ;)

19. You can speak about RR fluxes in the context of string string dualities Heterotic vs type IIA so speaking about them in the same comment (but not in the same context) is not that far fetched as you suggest. Some identifications are not that well known though, and with this I might agree... about the rest... well... I read the post and see what else I find, and then let you know.

20. no troubles with ethics. Everyone can say whatever he/she wants but some things are simply wrong. In this case the assumption that string theory covered "everything that is there" is not only wrong but also arrogant. Not all objects that can be constructed are necessarily stringy and there is no direct bijective connection between the *known* (not assumed) laws of nature and strings. It is very unclear to me (at least) that compactification as done now is the only way one can do it. I do not (and I underline NOT) say the objects we are discussing about (orientifolds, etc) do not exist mathematically. I say they are in general artifacts constructed to help us see nature better than the artifacts constructed 40 years ago. I cannot see in what way they are parts of nature, fundamental in any way or unique, and this is a fact. Ask some topologists to explain to you what "we" know about topology of 10 dimensional manifolds. Are you sure all dualities have been discovered? String theory (including branes etc.) is in fact a very simple extension of physics done before. It's "difficulties" come from the inability to "see" in a more complicated topological space which results from this construction. It may very well be that there is another form of representation that makes everything that is so "unclear" in string theory simply obvious. So, no, I do not believe that string theory is anything like a complete description of nature. Still, it deserves all the attention and I will continue to try to understand it better and better, and, who knows, one day simply go beyond it somehow... (well, not necessarily me...)

21. suggestion for future: write a competent blog entry about compactification and I will dissect every detail out of it. That would be helpful not only for me but for most of the readers here...

22. Hi, I wrote a competent blog entry about compactification 6 days ago:

23. brilliant, thanks for reminding me: I will read that and comment all the things that are (at least in my opinion) not yet clear... Thanks for the link!

24. I have blacklisted you. So much crackpottery per day posted with this much "self-confident" is something I don't want to be spread here.

25. As you can learn below, you will definitely not "comment on all the things that are not yet clear" on this blog because you were banned. I don't like readers who need to post more than 10 wrong comments about a simple topic XY before they - perhaps - start to kindly read and understand.

26. String theory has covered all good ideas in the search for unified theories and quantum theories of gravity.

You may write wrong things but you won't be able to write them here because in the long run, this is a moderated forums and deluded trolls like you are not welcome.

27. Updated: http://data.stackexchange.com/physics/query/147381/find-all-questions-with-at-least-1-of-a-list-of-tags 12097

28. Does it brush your teeth too?

29. Yup, your teeth will be brushed by Wolfram's Tongue which is a part of the Wolfram Language, too.

30. Brian G ValentineNov 15, 2013, 8:02:00 PM

It is not as funny a joke as AGW

31. Personally I don't like when one say a lot of big words, because they are said just to sell you something. Time will show whether it'll be something big.

32. I can't say I am at all surprised but it still seems like cruelty to children.

33. oh, don't worry, physics doesn't rely on an incompetent like Lubos Motl... he is widely ignored in most of the physics world, why not also by me? My absolute last visit on this site is this one, and, no, it is pointless to correct someone like Lubos for all the misconceptions he writes here or on various educational websites. He won't learn general topology anyway, not at a level equivalent with mine, anyway... and yes, of course he is wrong, as he doesn't want to see the issues with dualities between string theories and flux compactification, but again, I won't have time or mood to argue with irrelevant people...

34. Brian G ValentineNov 16, 2013, 1:34:00 AM

Probably a good idea not to argue. Your "discourse" on "compactification" is about the level of an AGW activist explaining the "science" behind the "typhoon"

35. Manish Earth has finally made the new book policy a real policy, but......

http://meta.physics.stackexchange.com/a/5204/23119

Energy Numbers is out to kill all the old questions : (

36. Well, at least you have confirmed a part of my comment.

37. Your thoughts on game 5 of the world championship, lucretius? I predicted 7.5 to 4.5 in favor of Carlsen before game 1. I hope Anand understands now that he has no chance of winning the series and goes all out on the attack so that he can win a game or two, at the cost of losing three or four. The alternative is to suffer in all seven remaining games like a warthog squeezed by a boa constrictor.
Go out in style, Anand. You were a worthy world champion, now give us a few memorable fireworks to round out your reign.

38. I have had very little time to look at the games so far. I saw the result of the fifth game on Judit Polgar’s Facebook page, but I still know no more about it than Judit’s comment about Carlsen’s “fantastic technique in the rook endgame”. Like almost everyone outside India I expected Carlsen to win rather easily: right now he is as much ahead of the rest of the field in world chess as Kasparov was in his prime. Anand has been a good but not great champion - while I think Carlsen will be in the same class as Lasker, Capablanca, Alekhine, Botvinnik, Fisher and Kasparov. So the only chance I can see for Anand is if Carlsen inexplicably looses his coolness - but this seems extremely unlikely since he has probably the strongest nerves in chess.

I don’t think Anand will follow you advice until he find himself at least two points behind - right now the most sensible approach for him is to try to restrict the deficit to one point for as long as possible and hope to equalize the score in the last two games.

Now going even more off topic: I am right now in the beautiful baroque city of Lviv (Polish Lwów). Later today I am going to the (once largely Jewish) town where my father and my uncle were born - there is going to be a memorial ceremony for the murdered Jews and a showing of a Swiss film about my uncle (the Swiss ambassador to Ukraine will be attending). My uncle used to be head of the Swiss nuclear power safety commission - he also consulted the Germans on this matter, in the days when they were still not as insane on this subject as they are now.

But right now I am very impressed with Lviv, which I have included in my list of favourite baroque european cities, along with Vienna, Dresden and Prague and, of course, a number of Italian cities. In order to be seriously considered in this company Lviv needs many millions of dollars to be spent on restoration and infrastructure, but even as it is, it is very much worth a visit. It has an amazingly authentic Austro-Hungarian and Polish atmosphere - and that in the city that is the center of Ukrainian nationalism.

From my point of view, the biggest advantage of Prague is the music - which is exactly the kind that I like best. So a fitting way to end this post may be with an example of the latter:
this is one of my favourite favourite conductors (a graduate of the Pilsen Conservatory) conducting music by one of my favourite composers, which possibly is not as well known to the readers of this blog as he deserves:

39. http://physics.stackexchange.com/users/16409/gidom-mera

40. Oops, posted in the wrong place.

41. +1: That is correct : )

42. Yes, this energy numbers guy is so poisenous and scornful. As the community finally accepted a new policy, he tries to at least destroy the old questions. How this guy drives me up the wall, and Manishearth even supports him, as you can see from his comments in the MSO chat :-(

So we will have not only to extract our favorite tags from physics se data dumps, but all the usefull questions tagged with book too...

And Manishearths rather nice longer comment was in vain, I thought we could work better together now at least concerning certain issues. But now he has clearly told me of and embraces EnergyNumers scornful and very destructive aims and ideas instead. It does simply not work :-(...

43. And looking at the relevant meta posts, they will most probably also delete everything that has a homework tag attached to it, including all the high-level advanced topic (ST, CFT, yang-mills, SUSY, renormalization, etc) question ...

And as they seem not ready to redefine the homework tag to not include such
High-level posts, it will no longer be possible to ask technical questions that contain latex, as they consider them to be homework by definition. The new homework policy converges to throwing the high-level baby out together with the low-level bath water...

So Manishearths long nice comment was just words with no effects in reality

http://physics.stackexchange.com/questions/86833/23119

In a period of 8 hours. The reason is that "Homework questions must ask..."

REALLY? Homework? This is the best way to discourage anyone who is trying to learn Physics. It is a legitimate question, which any beginner in QFT is curious about.

Pathetic questions, like

"A ball is travelling at 5m/s. It transverses 400m in 2s. Find it's mass."

or even

"My theory is that Special Relativisty is wrong! Einstie is wrong!" .

take at least 3 days to get closed, or sometimes are never even closed at all, and crackpot answers (like

PROF KOASBAOADA of HALDUSBSARDA INTRECORPAR CORPARATION proved that Einstien is wrong and that PROF KOASBAOADA is correct and that AETHER.

are sometimes even heavily upvoted but legitimate questions are closed within half a third of a day ? ! .

45. Yep, so we could start betting about how much time from now it'll take the rascals to go after user26143's nice questions and the others we are listing in the corresponding MSO chatroom ... :-(((

The bad thing is that there are too many users ravaging around in the higher level review queues that are (at least at present) not (interested in?) learning any theoretical physics topics, such as QFT etc, at a (even slightly) technical level. They like to close good legitimate technical questions about topics they dont understand as homework just because they contain LaTex for example, and say "leave open" to low-level and very basic stuff. I could explicitely name more than 5 ... ;-) and they are the most active ones in the close/reopen queues too :-/.

So these very active more than 5 reviewers can be very efficient in shooting down higher-level technical stuff and prevent good questions from getting reopend. And if it is not exclusively them, a moderator will support them if the bad things happen not fast enough (see my upcoming new blog post)...

Users who's judgement I fully trust I know at most 2-3 who appear some kind of regularly in the higher order review queues. This is simply not enough, but then I suspect that many of the good people are waiting for the new site instead of getting too much involved with business on Physics SE any more, which is a legitimate attidude too of course ...

46. The deletism on SE is really annoying, now Manishearth has even a script to more efficiently delete comments:

http://i.stack.imgur.com/fTJQm.jpg

I hope they will not go after all the interesting physics comments that provide additional information such as links to related papers, additional short explanations and thoughts to the topic of the "regular" posts, etc ... I would be very upset if they delete usful information and explanations Lumo for example gave to me in comments ...!

It is really a shame that Physics SE as a scientific site does not try to look what MO does to keep up a good site (for example preserve useful information among many other things), and instead imitates all the bad (for academic communities) things promoted on MSO which are maybe appropriate and useful for the much larger Trilogy sites (such as the horrible deletism among many other things), but NOT on smaller sites with completely different goals and targetted audiences.

47. The script was made by "Undo", by the way.

48. I dont believe this, some party poopers who always (and in this year successfully until now) tried very hard to prevent people from obtaining any information about references and study material they need, seem to never ever give up ... :-(

http://meta.physics.stackexchange.com/questions/5205/dealing-with-level-of-resources-in-requests#comment15091_5205

Emilio is exactly right and represents a very pragmatic an reasonable attitude ... Seems there are some people who will never tolerate or even accept the new books policy we have now ...

So I guess nobody is in the slightest surprised by this new brutal and fast (asked 2h ago and immediately closed 2h ago) unilateral closure by the most vigorous terminator out there

http://physics.stackexchange.com/q/87246

I mean what is so bad, dangerous, insulting, abusive, spammy etc about that question that there is not time for letting the community decide if it is a good question?

On Math SE, the whole community and not only I would call moderators who repeadedly close non-spammy, non-offensive, and non-abusive questions in such a brutal and fast way out, giving the community not even the slightest chance to assess and evaluate for themself the merits of such questions, if they like them or not etc ...

In the comments of this thread, some people on Math SE consider such or similar unilateral closures of non-offensive, non-garbage, non-spam questions even to be an abuse of moderation power (not my words ...!)

http://meta.math.stackexchange.com/q/11667/36639

I can only imagine what the Math SE community would think or say about repeated occurences of incidents where questions the community wants to reopen get locked (and the reopen votes deleted) by a moderators ...

49. Darn, is there a new behavior of links added in comments here? They behave different since today ...

50. Today's comment by Judit:
"I, myself would go in the last four games saying double or nothing , but this is my style and most likely nothing would be left at the end:) But at least I would play some fun games! Get brave Vishy and fight!"

;-)

51. Dimension10 (Abhimanyu PS) David Z can simply not let it be and accept the new books policy: Now he goes after questions that have been correctly edited in accordance with the new policy and attacks them by abusing the "list issue" point of view

http://physics.stackexchange.com/questions/87271/data-analysis-in-physics#comment178358_87271

WTF is wrong with David Z that he (obviously for personal reasons) tries to prevent people from obtaining useful information they need, like this by all means? Will he never stop to sabotage the new book policy and attacking the questions that comply with it? I am sorry to say, but David Z still taking continuously such strong issues with "book questions" (even with those that comply with the new policy) starts to look pathetic to me ...

Such happenings are among the things why I never liked the from (M)SO imported notion of "list-questions" which are not allowed, dangerous, etc ... Highl-level sites such as MO or TP.SE not even use(d) that term, because questions legitimately can have more than one answer in science. The "list issue" as currently defined can be abused by people with appropriate power to shoot down pretty much every question they dont like for some (personal) reason ... and on Physics SE this does happen all the time unfortunately ... :-/

52. And WTF, now they are really going after technical questions containing LaTex that involve some calculation, even Qmechanic ...?

That question is even conceptual, asking how the temperature of a phase transition is related to different thermodynamic quantities

http://physics.stackexchange.com/review/close/28512

And here, the OP has done a lot of effort

http://physics.stackexchange.com/review/close/28512

Seeing how such and EW problem can be solved step by step is helpful to many people who want to learn physics at a technical level.

I mean forget about the 5-10 closevoters who know next to nothing about theoretical physics (at a technical level), can not correctly decide what is a good technical question, and vote only (SE) political anyway ...

Too bad that these reviewers are the most active in the queues, whereas people who know about TP for example are (almost ;-) ...) absent there

But Qmechanic should know better ...! If this keeps going and gets worse, only equation (or LaTex) free questions will be considered "conceptual" enough to be allowed ...

Maybe Manishearth was not that off the mark by suggesting that the Popular Science proposal on Area51 has too much overlap with Physics SE ... ?

53. That's finally it, when you look at what the most active closevoters on PSE do, they are now seriously going after good technical theoretical physics question that contain some LaTex, so for example what Brandon Enright does in these review queues:

http://physics.stackexchange.com/review/close/28617

http://physics.stackexchange.com/q/87434/2751

http://physics.stackexchange.com/review/close/28613

http://physics.stackexchange.com/review/close/28596

http://physics.stackexchange.com/review/close/28595

In his profile he says " I don't know much about physics but I keep learning.". But his not knowing much about physics does not prevent him from tagging every theoretical physics question that contains LaTex with homework and even closevotes on them ! The same goes for John Rennie, tpg2114, Crazy Budy, etc ... And not enough reasonable and knowledgeable people are there to countervoted them

Brandon Enright and tgp2114 are really the worst culprits in tagging legitimate theoretical technical questions as homework and closevoting on them, but others do it too, even Qmechanics sometimes.

So there is clearly no longer any point for people interested in theoretical physics at a technical level asking aquestion there, as the dimwits have now heavily started to tag them as homework and closevote on them.

I thought maybe I could still ask here and there a question that is not quite optimal for our new site there next year, but technical questions about theoretical physics are now heavily persecuted by dimwits who have no clue about theoretical physics at a technical level and sometimes even by people who are knowledgeable and should know better ...

Heck, I even should stop clicking that site, because seeing good technical questions mistagged as homework and closed by dimwits is simply too painfull. So is there some brain surgery that could help me with forgetting that this site exists ...?

I want it to be deleted out of my mind !

54. Yes, tpg is actually OK, but ManishEarth, and more of Brandon Enright, is mad.

55. The site is now way too much dominated and controlled by people who are not knowledgeable about theoretical physics but have obtained tons of rep from answering (the dominating in number) popular, and very basic questions. I seldom look at the tags those folks are most active in, but from sporadically clicking such posts I was too often shocked by observing how highly they get upvoted on wrong, confused, or even misleading things, or on just clumsily googled together posts, etc ...

Those folks (Brandon Enright, tpg2114, John Rennie, CrazyBudy, etc) not only systematically persecute technical theoretical questions of good (theoretical physics) students, but systematically prevent that any good or at least legitimate questions can be reopend too.

http://physics.stackexchange.com/review/reopen/28665

And of course, it is those folks the moderators support (if they appear in the close/reopen queues), and not the people who want to learn theoretical physics at a technical level ... :-/.

As the dominant people interpret the new homework policy as "lets put a homework tag on any theoretical technical question that contains LaTex and shoot them down", asking technical questions that come up when studying advanced topics either alone by reading textbooks, or by following high-level courses, or reading research-papers, are now definitively prohibited.

So I simply could no longer ask there, even if I were not banned and wanted to. And this bad situation completely takes out the last fun of answering things too...

The only possibilities for me are now MathOverflow for mathematical enough TP questions and Astronomy for cosmology (a nice new expert gave me two good answers there ...)

56. Dimension10 (Abhimanyu PS)

BTW it is nice that jinawee has now > 3000 rep too, but I suspect this alone can not improve things much (nothing can) ...

I just hope he does not get gollumized by the bad reviewers, who seem to be on a campaign to mark any theoretical technical question that contains LaTex as homework to get it finally closed or even deleted due to the new policy (in particular one user is doing this very excessively), and who claim the voting to reopen is bad because the closevoters are Gods who are alway right by definition. The bad reviewers are completely wrong on this: even on MSO I have read the notion that the goal of community reopen is not only intended to reopen questions after a necessary improvement, but to directly reverse bad closures (done by mods or normal users) that never should have happend, too !

Of course the bad reviewers never reverse each other's actions, and as there are more then 5 of them who are fanatically active too, there is not the slightest chance to get anything reopend, the gang kicks everything out of the reopen queue immediately.

So I guess this has to be taken as an early Christmas prodigy (I still cant believe it ...) ... ;-)

http://physics.stackexchange.com/posts/87246/revisions

But dont forget to look at the arrogant second comment, the poster has the Chuzpa to even call very legitimate physicists crackpots and insult their work ...

57. Seems that pinging no longer works after the last DiSqUs update...

58. Strange ...

Craig Thone should be noted about the new site too when it is time for it ...

He gave me a nice answer to my anomalous dimension question :-)

Unfortunately I can not even upvote it and/or say thank you to him, he must think I am a thankless rascal ... :-/

Maybe you could tell him ... ;-)

And I hope no dimwit will go after my question and attack it as homework ...

59. BTW have you seen this ...?

http://meta.physics.stackexchange.com/a/5231/2751

John Rennie now explicitely admits what I always suspected: He is very tolerant towards low-level, simple homework questions but wants to make technical questions about advanced topics like SUSY ect go away ... :-(

Tagging such higher-level advanced topics technical questions as "homework" is WRONG, WRONG, WRONG, and WRONG !!!

You simply cant throw advance questions about CFT into the same pot as simple questions about Newton-mechanics John Rennie, like it or not !

John Rennies attitude fits well with his habitude to post very negative and dismissive answers to popular questions about such advanced topics he does not understand, but of course he always gets upvoted whatever he says ... :-/

And calling people interested in higher-level physics elitits is really of the mark, his answer should get downvotet to the ground :-(0) ...!

60. Yes, the answer is very shocking. I had initially thought that John Rennie was a good and knowledgable person, but I was obviously wrong.

You should remove his and Jerry Schrimer's names from the "How to promote Physics Overflow?" post.

Also, his answer is not actually what the OP was talking about. I actually agree with the OP. Banning HW so explicitely would discourage graduate-level hw too.

But John Rennie has obviously totally missed the point.

61. What did Jerry Schirmer do ...?

Yes, Colin McFaul nicely distinguished between low-level crap homwork and higher-level problems of advanced topics (which should IMO not be considered and tagged homework). The high-level stuff should always be allowed of course.

But the majority of the current crowd on Physics SE seems either to be not willing or not capable of the destinction or both (Or if they make the destinction, they do it upside down by persecuting the high-level stuff and leaving the crap alone ... )They simply want to throw everything starting from lazy Newton-mechanics and kinematics homework up to research-level technical questions that come up from reading serious HEP-th papers into the same sinbin and get rid of it :-(((

If they strictly do this, Physics SE will end up as a popular equation free site, as only popular and everyday-life questions will not considered homework and "conceptual" anough. And this exactly the kind of questions that always go into the infamous hot list too ...

BTW thanks for giving Craig Thone my thanks and upvote :-)

62. Jerry Schrimer in this thread has propogated the Be Nice propaganda, which is just totally opposite to the meaning of the site.

I don't think either of them would want to join the site.