Recent content by TheShrike

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    Correspondence Theorem in Group Theory

    Ah, well that clears that up. Thanks.
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    Correspondence Theorem in Group Theory

    That's correct. So we know the identity element ##1## belongs to ##\beta(H*)##. We also know that ##N## is a subgroup, so ##1\in N##. Therefore ##\beta(H*)## contains at least one element of ##N##.
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    Correspondence Theorem in Group Theory

    Hello, I'm following the proof for this theorem in my textbook, and there is one part of it that I can't understand. Hopefully you can help me. Here is the part of the theorem and proof up to where I'm stuck: Let ##N## be a normal subgroup of a group ##G##. Then every subgroup of the...
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    Solve SHM Leaky Bucket: dT/dt Calculus Solution

    Yeah, I think you did. Take a look at the first line again. You clearly know ##\sqrt{A}=A^{\frac{1}{2}}##, so perhaps make that conversion for ##T## before taking the derivative. Also, you will need the chain rule for this problem.
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    How do we identify one particular particle that moves ?

    It is! Particles that share all their properties (such as mass, charge etc) are indistinguishable. In particular, the statistical behaviour of bosons and fermions at low temperatures (e.g. Bose-Einstein condensation) is due precisely to their indistinguishable nature.
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    Calculating Linear Density of a Standing Wave: Solving for Lambda

    Just making sure, but does that also mean you don't know whether the standing wave is occurring at the fundamental frequency or at one of the overtones?
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    Calculating Linear Density of a Standing Wave: Solving for Lambda

    I'm not quite sure of the experimental set-up you have, but think about the number of nodes of the standing wave. It can be linked to the wavelength.
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    Challenge III: Rational Tangles, solved by pwsnafu

    Challenge V: Sylvester-Gallai Theorem, solved by Mandelbroth I didn't get anywhere with it, but I'm pleased to find I was going in this very direction. I just didn't know how to show it. Also, micromass, your second link is giving me a 404 Not Found error.
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    Divergence in spherical coordinates.

    He defines ##k## as a constant. So ##\frac{\partial k}{\partial R}## is the partial derivative of ##k## with respect to the variable ##R## which is zero, as he gets.
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    Particle in an infinite square well - interval -d/2<x<d/2

    Oh, I see what you were doing now. A conflict of conventions, as vela stated. My mistake. Looks like you had the answer all along. :wink:
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    What Constitutes a Valid Path for Least Action?

    I suspect the problem is the choice of Lagrangian (this is the name for the function defined by kinetic energy minus potential energy), \mathcal{L}=T-V. The action is the integral you mentioned: S=\int^{t_1}_{t_0}\mathcal{L}dt Minimising this gives the true path, and as Feynman says, this is...
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    Particle in an infinite square well - interval -d/2<x<d/2

    You're correct that your initial eigenfunctions are wrong, but your suggested corrections are not quite right either (but really close! :) ). N labels the energy states, so that the ground state is N=1 and the first excited state is N=2. Using that in your new eigenfunctions should result in...
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    Cold & Hot Wind: What's the Difference?

    I think there is a difference between the average velocity of the constituent particles, and the velocity of the gas as a whole. The particles are moving about randomly in all directions, even in the wind, but in the wind there is a bias towards the direction of the wind. This bias could be of...
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    Force on charges placed at vertices of a square.

    Alright, I've given a few of these a try. Taking tiny-tim's suggestion first: I'm going to have the differential equation: v\frac{dv}{dx}= \frac{q^2}{mx^2}\Big(1+\frac{1}{\sqrt{2}}\Big) Let those constant terms be collapsed into the constant A. Then, by separation of variables, the...
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    Force on charges placed at vertices of a square.

    Oh, I was considering the L as a constant, so that if I integrate I'd get v(t)=\Big(\frac{q}{l}\Big)^2\Big(1+\frac{1}{(\sqrt{2})^3}\Big)t+A with A an arbitrary constant. Although putting in the initial condition would lead to A=L. Using the interpretation you've given I'd have no idea...
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