@TAbraham I'm not sure how to say this, but the odds are that alarge doesn't want to join your chat room at least in part because you keep pinging him in chat when he has already said he's busy with something else. Seriously.
7
People come and go in chat. They are not always available. You have to live with that.
And I'd like to call your attention to a comment I posted a couple of days ago to the effect that almost all our users and no trouble and how wonderful you all are...
@dmckee I think it is as simple as the following. A plane wave of momentum $h/\lambda$ is not able to resolve spatial structure that varies over distances of much less than $\lambda$. Rather, one sees merely the average over a distance $\sim\lambda$. I do not know of any rigorous proof of this, however it is intuitively fairly obvious I hope. It is also borne out by my experience of the theory of quantum probes in general (not necessarily coherent beam scattering).
I guess the idea is that it is not possible to create non-negligible interference effects between two scattered wave where the scattering centres are separated by $d \ll \lambda$. (I am thinking in a sort of Bragg scattering picture here).
When I burn wood, paper, or other plant matter, where there is a flame, there generally isn't too much smoke, but it I blow the fire out, smoke starts billowing up. It billows thicker and thicker as the material gets hotter, and suddenly a flame springs up. At the same moment, the smoke dissipate...
I work on the 1st floor of the building, which (supposedly) is where all the "important people" will pass when coming to see the Dept Chair (if that even happens)
@KyleKanos I always wonder who these "important people" are who (1) don't understand academic culture and (2) simultaneously care how the little people get their jollies as long as they turn out the [whatever it is these guys want from us].
I've met people who fit either criteria, but none who meet both.
And I seem to recall meeting the dean, totally not knowing who she was, and acting like it was no big deal while discussing my undergrad research at poster session
After she walked away, my advisor was like, "Whoa you handled that pretty well."
re not being allowed to hang up cool stuff. recall that myself. "someone" ripped down all my cool collection once yrs ago ... actually it was also a science lab & a PHB :(
xkcd also has a strip on the collatz problem. :) the guys a genius geek who unf also draws like one. maybe he could join up with watterson or something.
so KK wondering why you want to get out of the wonderful world of science/ academia into the wonderful world of finance....?
have you guys heard of larry gonick? hes great too. "illustrated guide to physics". old/ great...
@vzn I guess my years in grad school have basically shown me that I don't really want to be in academia (not a lot of fun in grading, course prepping, & failing 90% of research proposals). So that really leaves industry
I have a brother in the finance industry who's been telling me for years that he can get me a job in the company, so I'm listening to that advice
afaik even sr scientists have trouble getting grants/ research proposals funded. is that what youre talking about? science is cool, but yeah, it has its limitations... went thru similar "career path" (so to speak) myself somewhat...
you might be interested to read about doyne farmer. very interesting character. similar story also.
there are some real hardcore scientists working in finance... long list...
@vzn I'll try to remembering the books for the future
Right now, there's too much on my plate (the aforementioned Lewis book, Hull's Finance book, and Schreve's Discrete Stochastic Calculus plus that whole "writing my dissertation" thing)
@vzn, a lot of the quant buy side boutique shops, where the money and the stress is, are rather small. The least stressful place is probably in model validation, so middle office of a large bank. With the new regulations and all those are hiring a lot, but quants often view them as deadends, career wise. Well, traditionally at least.
derman, "my life as a quant," another great book on my to-read pile :)
there are certain types of quant jobs that have been around ages, maybe the model validation, but there are newer edgier types emerging within last ~2 decades.
@vzn I imagine the golden age of the math crunching quant is over, as stuff's becoming more computational (like machine learning, HFT). I don't think the econophysics stuff has really even convinced academics yet (but do add Sornette's book to your list)
@tpg2114 After going through the conversation transcript from yesterday, I think I've understood your argument. I have come to finally agree with you on that until evidence points to a dire problem in the way downvotes are cast, the benefit of doubt should be given to the present scheme of function.
@tpg2114 Please don't think my purpose to be here is to waste your time. I genuinly want to see something better for the site, and i felt putting my view across would be a good start for that. And I'm really as less argumentative in real life as I am on the h bar. :)
Is there any real reason why it is conventional to call operators $f: X\to \mathbb{R}$ where $X$ is a Banach/Hilbert space functionals rather than the usual functions, which seems to be used only when $X$ is Euclidean space? I'm asking because I've realized that no such special word is used int he context of manifolds
...although, of course, one can argue that we're really working on Euclidean space when considering functions on manifolds
@Danu I think it is because the Banach/Hilbert spaces often are themselves already real functions, and someone thought that one should call functions of functions functionals.
alarge interesting assertion but from my pov it appears that its a new golden age of quants. yes centered around HFT/ML & large hedge funds etc & other stuff we cant fully imagine right now (eg bitcoin!). yes much more "computational" although thats a tricky distinction to make. (years ago it was mostly spreadsheets, now more code-oriented/ algorithmic.) there is quite a bit of interesting analysis of quant role in 2008 crash but from my pov its largely a red herring.
yes econophysics is a very young science but yet quite valid & maybe will help sort out a lot of the bogus science that has permeated "the dismal science" for long ages. re quants, you seem well read in the area, do you have some connection to the "biz"?
its a shame that there are some highly political questions re macroeconomics such as taxation/ regulation etc that likely have quantifiable scientific analysis/ answers but are subject to so much ... misconception and near propaganda ...
@vzn I agree: Quants want to blame quants, traders blame traders (see e.g. Das' Traders, Guns and Money), and so on. I suppose it makes one seem more influential than what one actually is.
As for the golden age of quants, I think the industry, like many other fields of science, are moving away from causation to correlation. Example: big data doesn't really explain anything, nor does it rely on physics-like postulates, but rather you correlate a lot of data and make predictions based on those links rather than on some mental/mathematical model/theory. This is to say that the skills required of the quants of today are different from those of Derman et al.
Econophysics is indeed young, and largely ignored among economists. In some sense the physicists entering the field are reinventing the wheel in many ways, which is not seen all that useful.
And I don't think taxation/regulation etc. can really be easily quantified. They are inherently political. Unlike physics, economics is not set in stone and as you change policies, the underlying "laws", too, change.
It is in this sense that physics is the easiest of the sciences: It allows for rather exact mathematical modeling, and once you have figured something out, it's not going to change (sure, you'll get better models but the original model itself will not lose precision as time goes by).
some disagreement. money is a complex energy system subject to laws although that is still somewhat misunderstood. legislation/ legal laws adjust the energy dynamics of the system. ie parameters so to speak.
re causation vs correlation, big data. indeed a key part of future trends. however, my suggestion would be that big science is extremely interested/ focused in carefully isolating the difference between correlation/ causation like never before.
what changes somewhat is the scale. one can isolate real causation across many variables whereas before that was not so practical.
agreed, still a lot of speaking-separate-languages going on between econophysics/ economics. think econophysics has some very fundamental/ groundbreaking insights to offer & has done so already.
there are some basic energy laws of money roughly like F=ma probably now mapped out but not widely known/ embraced/ appreciated.
re "physics as one of the easiest of the science" ofc it is also one of the most fundamental & hardest too :)
@vzn I somewhat disagree. This view can help in looking at some minute details of some subsystems (e.g. this), but the whole thing is based on human designed infrastructure, and I think in the macroscale this approach won't be of so much help (and things keep on changing, too).
@vzn I actually have this book on my bookshelf (and on that note, also the quantum information book by the same author), but have not managed to read it yet. A friend of mine was influenced by the book a lot and decided to write one paper in an open collaboration kind of way. I think about 20-30 people joined in on the effort.
hi alarge studying collaborative science quite a bit for years re nielsen, polymath etc, also planning to blog on it in awhile, can you cite that collab science paper?
actually think that econophysics may be more applicable/ observable wrt macroeconomics than microeconomics! law of large numbers etc... have to dig up a paper on that, its been years since reading it....
think it was far more substantial than appreciated....one of those key papers that cant be recognized except on long hindsight....
basically it compared large economic systems to a thermodynamic gas behavior & finds ideal-gas-law like dynamics in std economics eqns.
individual economic agents are like energy particles that exchange energy/ momentum.
@vzn That is what one would intuitively think, yes, but I think it's false. The landscape depends so much on the institutions (like, say, the rise of shadow banking).
@vzn This is so idealized that I think it is largely useless. It's a fun model for a physicist, but I think these sort of models is why econophysics is ignored by economists.
Rather than agent based modeling I think it is behavioural finance that has really garnered a lot of interest in the past couple of decades.
There are maybe some universal "truths" in finance. Sornette has, for example, used the idea of fluctuations near phase transitions to predict stock market crashes. This has of course been used for fish populations etc. in the past, so it is not in a sense exactly a new idea.
But I believe that they have predicted several of the busts in the past 10 years or so.
But I think seeing scaling laws (something Mandelbrot first applied to finance, I think) is still far away from any sort of explanation.
Anyway, I think self-propulsion/active systems is poorly understood in physics, too, so I doubt we'll be seeing anything very useful in finance/economics for quite some time, either.
yes the ubiquitous scaling laws in finance still seem poorly understood & maybe some theories will emerge to explain them.
the trick to macroeconomic econophysics models is that someone has to fit the data. the eqns are there but the data fitting is not so much. think this will be done at some pt & be groundbreaking/ paradigm shifting because theory/ data will mesh quite well at larger scales (law of averages).
am digging up old refs, maybe will blog about some of this at some pt.
as for econophysics "predicting" crashes, think that is an unrealistic/ unattainable goal except in general. think it will not show much more success than existing economics in this regard. its quite like "predicting" earthquakes. quite based on physical laws but nearly impossible to pinpoint.
predicting stock crashes is quite similar to predicting declines in stocks, an inherently "nearly-pure" random walk.
@vzn Sornette et al have had quite a few successes, and there are similar stories from other fields. The idea is, in short, that near a phase transition the system starts to oscillate more (think, for example, metastable Ising model), and from these you can make predictions. It is not at all the same thing as predicting declines in stocks.
I think that the papers you posted are interesting, but I think of little real world value. The models are extremely idealized, and seem for example to gloss over liquidity, something that can be argued to have played a big part in the previous financial crash.
@DanielSank Danny, you probably are good at such things as I have problems with. I have a stupid problem with Lienard-Wiechert potentials: a charge moves with constant velocity. Such a charge shouldn't radiate. But in the formulas of the electric and magnetic field appears the vector position of the charge, and it changes in time. So I get that both the electric and magnetic field depend on time. Someone told me that if E and B depend on time, I got e.m. waves. Is that true?
@KyleKanos and/or @ChrisWhite Do you guys use immersed boundary methods at all? The idea is to represent interfaces (walls, or more likely in your cases phase changes) with something like a levelset that cuts through cells arbitrarily
This question is for deciding the "Thank You" policy of Phys.SE and meta.Phys.SE. Currently a user isn't allowed to say "Thank you" in his/her question. So,
Upvote this question if you want that any user should not able to say "Thank you" in his/her question.
Downvote this question if you w...
Would it be ironic of me to remove the "thanks" aspect to that Meta post (doing other edits too)??
user54412
@tpg2114 Alas no. I could see how they could be useful in certain situations, but most of the time boundaries are nicely aligned with cells. After all, there aren't many oddly-shaped walls with weird properties floating around in space.
@ChrisWhite It can be used for gas/liquid interfaces too!
@KyleKanos Agreed, but I also don't really care enough to change it. Once the voting works out for a few days, just post an answer that says "Based on the vote count, it appears the community supports X"
While in chat lamenting a really bad question that was migrated to a site because 3 people voted for it elsewhere, we got to wondering:
Is it possible to see a map of all the migration pathways in the vote to close lists?
I know moderators can move things anywhere, but what can the normal close...
The visualization is kinda cool, although hard to make sense of with so many variables (and the dataset is a really small subset because otherwise it wouldn't make the visualization)
@DanielSank : this is my problem too. It is a longer time since I learnt such things than when you learnt them. And the teacher was a bad one ( a conceit fellow by whom all the students were idiots). Also, we learnt this topic superficially, without exercises, only the proof of the formulas and "good bye".
I'm writing an answer to a question, in which I want to link to an important paper (the discovery of the W-boson). As far as I know the paper is under copyright (behind a paywall at Physics Letters), but the Princeton university webpage hosts a PDF copy of the paper. What's the policy on linking to papers in this way? I guess it's forbidden?
@innisfree I think linking to copyrighted material in that way is forbidden, since the CC-something-something license under which all posts are published on SE requires all sources to be similarly "free".
@innisfree I'd provide the PhysLetter link or a DOI or whatever is similar. If they're a student, they can get it while on campus anyway. If not, they could get it if they so choose
That's a shame. I find it very annoying that such important papers are copyrighted. I'd like them to be available to everyone, in as many languages as possible.
@KyleKanos can you tell me why I was punished? On an old question that I answered in the past I had a long discussion with Mark Mitchison. Unfortunately I forgot to introduce there a reference better than the one which was given in the post. I noticed that now and I made the change. And I was punished with 2 points. It's not just. 2 points are not big deal, it's only not just.
@Sofia If the people downvoting you don't leave a comment, it is impossible for anyone else to tell you what they considered wrong/not useful about your posts.
Unexplained downvotes are something we all have to live with