BRS: Feedback Poll, Question A

[Chris Hillman]

Dear SA/Ms:

I am seeking feedback from active and inactive SA/Ms regarding both the current and possible future utility (if any) of BRS.

I have two multiple choice questions; due to limitations of VB software I must apparently create two different polls to ask them. This poll contains the first question. It has four possible answers; please check the box which best describes your judgement.

This is an anonymous poll which is open for 100 days, in case anyone wishes to look over BRS threads before voting.

I would welcome any additional comments from any active or inactive SA/M, either posted in this thread or by PM to myself!

Thanks in advance to everyone who participates!

 

[Chris Hillman]

BRS: Feedback Poll, Question A: Two Comments

Just to get the ball rolling, I'll post two comments of my own:

First, I myself have been disappointed by at least one aspect of BRS threads to date: I haven't really finished saying what I wanted to say in any of them, so most of them are so far "incomplete" in the sense that they don't yet contain all the information I announced in the first post in each thread. (Example: probably the "least incomplete" BRS tutorial thread is the one of Weyl vacuums.) This is due, I think, in part to

• lack of evidence of interest on the part of other SA/Ms in many (but not all) of the threads,
• in order to start writing, I seem to need to experience a moment of enthusiasm, but in the past decade I seem to be unable to sustain that for any length of time, possibly irrespective of interest or lack of it from others.

Second, I think the "replies" and "views" statistics are grossly misleading, because at present:

• almost all of the "replies" consist of my own followups in a given BRS thread; this could be somewhat desirable in an unfinished "tutorial thread", but it could also lead to me underestimating the interest in a thread,
• AFAIK, almost all of the "views" are by myself.

 

[Dale]

Hi Chris, I don't think that any of the poll options apply to me. I find it useful, but difficult to digest. It takes me quite a while to chew on each piece and figure it out. Don't be discouraged by long pauses when you are talking about difficult concepts.

(sorry, just had lunch obviously)

 

[Chris Hillman]

So would "rarely read it; no time" best describe your judgement of how useful BRS has been so far to you personally?

And thanks much for your immediate feedback!

Anyone else: even if you think none of the four available answers come close, it would help me if you try to choose one, or take the time to add a brief comment in this thread (or both). TIA!

 

[Hans de Vries]

Well, at least I'm a happy Maxima user thanks to one of your threads here Regards, Hans

 

[Chris Hillman]

Maxima: can PF community help develop it further?

Oh good! Even better, if we can build some community support here for contributing to further improvements of Maxima. I know that PF User:Mentz114, for example, has written some scripts intended to extend the somewhat limited functionality of ctensor(), the built-in Maxima package which computes (coordinate basis, frame basis components of) certain tensors for specific manifolds defined by a (metric, frame field). I think a lot of people would be very happy to have a reliable free eduware toolkit for that.

More broadly, there is the SAGE iniative, which sometimes seems very ambitious, e.g. to build Maxima to the point where it has ODE and PDE solvers and Groebner basis packages similar in capacity to Maple's dsolve, pdsolve, casesplit, etc.

 

[alxm]

Well, for my part I'm a chemical physicist; So your average astrophysicist has likely forgotten more about GR than I've ever known.

So basically, I don't (and wouldn't purport to) understand most of anything that's posted here.

 

[Chris Hillman]

Hi, alxm,

It's true that many of the threads so far have been related to gtr, but only because that is a topic which arises so often in PF. But the thread I am working on currently has to do with Rubik's cube (groups, related to Polya enumeration, so might interest chemical physicists), and previous threads dealt with homology (algebraic topology) and rational polynomials with unusual Galois groups (in particular, "palindromic" polynomials are have Galois groups which also arise in studying the Rubik group).

Of course, I am probably just restating your objection as "not of interest to non-mathematicians"...

BTW, I noticed this earlier today

http://arxiv.org/abs/1008.2438

The authors don't seem to have done very much yet with their observation, but I would be curious to hear the reaction of a chemical physicist!

 

[Bystander]

"None of the above." Nothing so far that's particularly tweaked my interest --- doesn't mean there won't be in the future.

 

[DaveC426913]

Nowhere in this entire thread is there an explicit reference (beyond one or two cryptic acronyms) as to what this thread is actually about. It is astonishing that a thrread can go one so long and leave no clues.

I'm just sayin'.



[EDIT] Ohhhhh. BRS = Backroom Seminar.

 

[alxm]

It's true that many of the threads so far have been related to gtr, but only because that is a topic which arises so often in PF. But the thread I am working on currently has to do with Rubik's cube (groups, related to Polya enumeration, so might interest chemical physicists)

Well you know what John Slater called it? "Gruppenpest" (although according to Wigner, the term was coined by Schrödinger. But few opposed it to the extent Slater did, for sure). Of course, in the end Group Theory won and now every chemist in the world knows something about point groups (yet typically has no idea who Galois was).

Of course, I am probably just restating your objection as "not of interest to non-mathematicians"...

Haha, well you could say the same about the whole field of Mathematical Chemistry!

Sadly, chemistry doesn't benefit from math as much as it could, largely due to the fact that most chemists don't know that much outside the usual calculus and statistics. Group theory (such as the paper you linked) certainly should have broad applications in, for instance, combinatorial chemistry. Which, despite its name, doesn't really involve that much combinatorics. Today, the only ones really applying group theory a lot is quantum chemists and crystallographers.

 

[Chris Hillman]

My first math book project was "Gruppenbildbuch", i.e. group picture group, i.e. a book using Cayley and Schreier graphs and subgroup lattices extensively to introduce elementary group theory.

My diss was on the simplest model of quasicrystals, aka Sturmian tilings or "generalized Penrose tilings", a construction due to the combinatorialist N. G. de Bruijn (same mathematician known to computer scientists for fundamental work on algorithms and graphs). The variant I used is due to Oguey, Katz, and Duneau. Not too many besides Penrose know about both Penrose tilings and NP formalism!

BTW, GAP has some nice packages for crystallography. Its free researchware/eduware.

(Always trying to interest everyone in learning more math...)

 

[Haelfix]

I enjoy this forum. It's nice seeing an expert in mathematical GR conduct his magic. There aren't that many left anymore, and even in the large physics departments around the US its relatively rare to see discussions done in this way, at least for those of us who aren't pure theorists.

I enjoy it, b/c it refreshes material that I did know (or should know) but don't get a chance to practise much anymore.

 

[alxm]

Kind of off-topic, but man.. it doesn't seem I can't escape Group Theory anymore.. On the latest Futurama, they ended up constructing a (real!) group-theoretical proof to solve a plot point. (http://static02.mediaite.com/geekosystem/uploads/2010/08/Prisoner-of-Benda-Theorem-on-Chalkboard.png" )

The problem: The characters "switch bodies" with each other using a machine, but can only switch between each pair once. How many extra bodies do they need to get everyone back?

This is what happens when math PhDs start writing sitcoms...

 

[Chris Hillman]

Thanks!

I enjoy this forum. It's nice seeing an expert in mathematical GR conduct his magic. There aren't that many left anymore, and even in the large physics departments around the US its relatively rare to see discussions done in this way, at least for those of us who aren't pure theorists.

Thanks so much, Haelfix!

I too worry that with the Death of the Book and the retirement of the Greatest Generation* (those who participated in the Golden Age of gtr), much of this knowledge will be lost if younger researchers don't put some effort into learning it while they can still ask questions of the old masters. With the publication of such wonderful books as the "field guide" by Griffiths and Podolsky and the availability of software like GRTensor which make it easy to plunge in and explore, the obstacles are far, far lower than they were during the Golden Age.

[*I figure I can dub them the "Greatest" because I am not a member of that particular generation!]

This concern is particularly worrisome because--- as I think most of us would agree--- the long sought quantum theory of gravitation has not yet appeared, much less been developed to the point where gravitation physicists can forget about gtr. If indeed they ever can do that--- I think one should bear in mind that no-one in his right mind has ever proposed to forget about Newtonian gravitation, which retains its uses, and I think gtr will continue to be the best theory to use for most of the applications where it is currently used, other than those currently treated with semiclassical approximation (ill-defined and tricky).

See also my Post #13 in the BRS thread "Some comments on recent gtr-related threads":

www.physicsforums.com/showthread.php?p=2848963#post2848963

 

[Chris Hillman]

Curious about a possible "permutation puzzle" new to me

On the latest Futurama

Is that a sci-fi show on TV of which I have not heard? Or a sci-fi game program?

The problem: The characters "switch bodies" with each other using a machine, but can only switch between each pair once. How many extra bodies do they need to get everyone back?

Hmm... not sure I understand the plot point, but the mathematical point must involve restricting to a generating set consisting of individual transpositions (permutations of order two which swap two elements and leave all the others fixed). This genset is the one which is used in studying reflection groups, in particular the Weyl groups associated with some important Lie algebras arising in the ADE classification and which are much beloved of physicists. John Baez's This Week series featured a dozen wonderful posts on this circle of ideas (best found using the widget on his website to search his website).

The point I'm missing must involve the symmetric group (?) in question. I guess the plot point must involve extending from some S_n with some generating set to some S_(n+m) with words written in the generating set consisting of transpositions. I guess the mathematical question must involve the number of points moved by the shortest words in the new group, i.e. the number of bodies which must be used to swap two particular minds/souls without using any bodies used previously...

 

[Haelfix]

Incidentally, I have a running confusion about something in GR that I haven't had explained to me in a satisfying manner (read mathematically correct).

I don't understand the concept of an asymptotic symmetry group and why there was a huge controversy about it in the field. Prima facie it seems easy to define?

Everytime I read the literature there seems to be major disagreements over the formulation thereof, and its confusing.

 

[Chris Hillman]

Well, you probably already know just what I am going to say: such "controversies" inevitably result when people are too lazy to write (or think?) carefully enough to explain clearly and precisely exactly what concept they are talking about. Since I like to be helpful, I'll try to oblige with another BRS thread when I get a chance...particularly important since this might be one occasion on which I admit that a particular "controversy" has some substance.

BTW, alxm, if you come back, this shows why I yak so much in the BRS about gtr ;wink: Great stuff, and certainly important in physics, but not really one of my strongest mathematical interests, which is sometimes a bit frustrating, particularly when people assume I am only interested in gtr--- or even worse, only interested in debunking anti-relativity cranks--- or even worse, some particular anti-relativity crank! But people keep asking me about it, and their questions are often interesting, so...

 

[Chris Hillman]

Re my expressed concern that a new generation of physicists may be failing to learn from the masters of the Golden Age of Relativity, including Chandrasekhar (!), see my Post #4 in the BRS thread "Some Recent GTR-Related arXiv Eprints":

www.physicsforums.com/showthread.php?p=2853915#post2853915

 

[Ich]

Some of these thread were really helpful for me; others are interesting, but I don't have the time (or energy, I admit) to study them in a way that really furthers my understanding.
I usually do read the "Random Comments", because that's where I find useful information from time to time that doesn't need an hour to get the gist of.
Generally, it's a good thing that there's someone around with a firm understanding of relativity who can help out in the harder cases.