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  1. R

    The need of having done a class formally

    yeah, I have been doing it informally, i.e. nothing will show up on my transcript.
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    The need of having done a class formally

    The need of having done a class "formally" I'm (something like) a master student in Europe, now being in my first year and I have the following problem: Last semester I was attending lectures on QFT, but I haven't done the exam/assignments, since it was way too much for me that semester and...
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    Study breaks

    We have been discussing this topic with my classmates recently, and I find it quite interesting, so I also want to ask you guys: 1. For how long can you study without taking a break? 2. How long are your breaks? 3. What do you do in the breaks?
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    MSc in theoretical Physics

    If you're interested in hep-th, then you might consider: Cambridge, Oxford, Imperial College London, ETH Zurich, LMU Munich, University Utrecht. They all have very good reputation in hep-th and I think that all of them offer master's degrees in theoretical physics. As to what your chances are...
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    Mathematica Theoretical and mathematical physics grad schools

    I'm interested in doing my PhD in theoretical and mathematical physics - i.e. subjects like Quantum Field Theory, String Theory or Quantum Information Theory. My question is which universities in the US have really good programs in these areas?
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    Physics Career in Quantum computation

    It depends on whether you want to do theory or experiment. If it's theory, then theoretical/mathematical physics would be the right field, with taking some additional math and computer science courses, like Functional analysis, Advanced Algorithms, Complexity theory, Coding Theory,... In...
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    F-number and light intensity

    Aah, I see, the problem with my formula was that if I changed f, x_i would change too. Your picture, jtbell, explains it very well. Thank you very much for your time.
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    F-number and light intensity

    This is perfectly clear. This is the critical point. Let's say that the heigth of the object is y_0, the focal length is f, and the distance from the focal point to the film is x_i (as in the first picture in Then by similarity of triangles the...
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    F-number and light intensity

    ooops, you're right of course, N is the inverse of the f-number. Anyway, I still seem to misunderstand something. I found this 'derivation' of the equation, here: , although I quite don't understand some of the steps there (even if it's elementary...
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    F-number and light intensity

    Well, it's actually in most of the books on photography, but it's never derived. They say, that when you change the aperture by a factor of sqrt(2), the intensity of light will change by factor 2.
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    F-number and light intensity

    I've been searching through the internet and some of my optics books, but nowhere was I able to find the derivation of the law for a camera lens, that the intensity of light that comes on the film or chip is proportional to \frac{D^2}{f^2}=N^2, where D is the aperture diameter, f the focal...
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    GRE in both Math and Physics

    Has anyone done this? I'm a physics major and I'd like to pursue a degree in mathematical physics. I guess that physics GRE is expected from me as a physics student, although actually I feel much more comfortable in math. Do you think that it would be hard to make both? Would it make me...
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    Non-commutative geometry

    Lie group = group + differentiable manifold, hence knowledge in both algebra and differential geometry is needed.
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    Mathematica Mathematical Physics

    Traditonally, it is about solving mathematical problems that arise in physics (and are too difficult to be left to the physicist :-) ) - like finding a solution to some PDE, making integral transforms, minimizing some functional,.... But it can also mean mathematically rigorous study of...
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    Real Analysis vs Differential Geometry vs Topology

    The answer is definitely Differential Geometry, especially when you want to do QFT, where it is widely used. It will also give you much insight in other subjects (apart from the obvious GR), like classical mechanics, electrodynamics, advanced QM,... it's everywhere. Real analysis might be also...
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    Letters of recommendation (for the 100th time)

    Yeah, I'm going to ask both. But anyway, what if the I don't get it from the supervisor? Will it look suspicious on the application?
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    Letters of recommendation (for the 100th time)

    I'm applying for a masters degree on an European university this year. I have an almost perfect GPA of 3.98, I took some pretty advanced classes and have two years of research experience, but the problem is with the letters of recommendation. They require me to send one letter of...
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    Zeros in a data set

    yeah, but I'd like to know where exactly the points are, so the method I'm searching for should be using some kind of interpolation and then find the zeros.
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    Zeros in a data set

    Hi, does anyone know of some nice root-finding method (preferable GSL :-)) for a data set - i.e. I have a set of 3D data (x,y,z) where z = f(x,y,) and I want to know where the zeros of f are. I guess, I could write it myself with some interpolation method, but just in case someone knows...
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    Plotting 3D data

    It's about 30x30x30 points, more or less.
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    Plotting 3D data

    :rolleyes: The ball was just an example. The objects that I'm working with are much complicated. I'm not really sure if interpolation is what I'm searching for.
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    Plotting 3D data

    yeah, but those objects are pretty crazy and really far away from spheres. what kind of averaging schemes do you mean?
  23. R

    Plotting 3D data

    Well, let's say I have some 1000 points which form (or should form) a ball, for example. What I want to get is a nice, smooth 3D ball. Is that possible?
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    Plotting 3D data

    I have a set of 3D data (i.e. a large file where each row contains three spatial coordinates) and I'd like to get a nice, smooth 3D object out of it. The objects are not surfaces, so it's not just plotting a function (i.e. to every (x,y) there exists more than one z). Does anyone have an...
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    Simple topological problem

    I'm really stuck on this simple problem: Let X be a topological vector space and U, V are open sets in X. Prove that U+V is open. It should be a direct consequence of the continuity of addition in topological vector spaces. But continuity states that the f^{-1}(V) is open whenever V is open...
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    What are these functions called?

    Is there any name for the functions for which |f(x+y)| \leq |f(x)| + |f(y)|?
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    Programs Doing Master degree in US

    Well, I don't know how about the OP, but I'm studying in Austria and we have a three year bachelor degrees here. After completing the bachelor degree you apply for a 2 year master degree (and after that you can apply for a 3 year Phd.). As far as I know the usual bachelor degree in the US...
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    Programs Doing Master degree in US

    No, he's asking if he can apply for a master degree in the US when his bachelor degree took only 3 years (compared to 4 years in the US).
  29. R

    Canonical form of PDE

    How do I transform a second-order PDE with constant coefficients into the canonical form? I tried to solve this problem: u_xx + 13u_yy + 14u_zz - 6u_xy + 6u_yz + 2u_xz -u_x +2u_y = 0 I wrote the bilinear form of the second order derivatives and diagonalized it. I found out that it is a...
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    Closed subset of a metric space

    Of course :rolleyes: - a little modified Cauchy-Schwartz inequality is the key. I hate algebraic tricks :smile: Thanks for help