Recent content by phagist_

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    Proof of integral identity (popped up in a Fourier transform)

    any ideas? I am legitimately stumped on this one..
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    Proof of integral identity (popped up in a Fourier transform)

    Homework Statement Prove; \int_{-\infty}^{\infty} \frac{sin(\gamma)}{cosh(\lambda)-cos(\gamma)} e^{i \omega \lambda}d \lambda= 2 \pi \frac{sinh(\omega(\pi-\gamma))}{sinh(\pi \omega)} Homework Equations Contour Integration/Residue Theorem? The Attempt at a Solution I have messed...
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    Expectation value of spin in an Ising lattice

    never mind, I figured it out.
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    Expectation value of spin in an Ising lattice

    Homework Statement I have to show that (the question says deduce from the fact that magnetization is monotonically increasing and a concave function for h>0) \left< \sigma^2_{j} \right> - \left \sigma_j \right>^2 \geq 0 and \left< \left( \sigma^_{j} \right> - \sigma_j \right)^2 \right> \geq 0...
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    Evaluating Real Integrals using Residue Calculus

    ok thanks for the replies. I'm having trouble thinking of a suitable function to apply the squeeze theorem with. If I use \int_{-\infty}^{\infty} \frac{{e}^{ax}}{{e^{x}}} dx = \int_{-\infty}^{\infty} {e}^{x(a-1) dx. The function works in the \lim_{x\rightarrow\infty} but not as...
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    Evaluating Real Integrals using Residue Calculus

    Homework Statement I = \int_{-\infty}^{\infty} \frac{{e}^{ax}}{1+{e}^{x}} dx \; \; 0 < a < 1 a) Show that the improper real integral is absolutely convergent. b) Integrating around the closed rectangle \boldsymbol{R} with corners -R, R, R+2\pi\iota, -R+2\pi\iota use residue calculus to...
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    What is the inner product of a linear operator on a complex inner product space?

    So I have <[I+T^{*}T]x,x> and the definition of T^* is <Tx,x>=<x,T^*x> but I'm not really familiar with <Sx,x>.. this means that S is operating on x, right? Then another way to say it is <[I+T^{*}T]x,x> I'm looking for a way to 'break it up'.. I...
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    What is the inner product of a linear operator on a complex inner product space?

    Homework Statement Let T : V \rightarrow V be a linear operator on a complex inner product space V , and let S = I + T^{*}T, where I : V \rightarrow V is the identity. (a) Write <Sx,x> in terms of x and Tx. (b) Prove that every eigenvalue \lambda of S is real and satisfies \lambda\geq 1. (c)...
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    Finding Magnitude of v+iw in a Complex Inner Product Space

    Homework Statement Let v,w be vectors in a complex inner product space such that ||v|| = 1, ||w|| = 3 and <v,w> = 1 + 2i. Find ||v + iw||. Homework Equations The properties of an inner product. The Attempt at a Solution I figured ||v+iw||^2 = <v+iw,v+iw> Then using the...
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    (Linear Algebra) Vector Space and Fields

    oops, I see.. but I still get a denominator of a^{2}+2ab+2*b^{2} I am really new to this stuff and I'm also having a hard time trying to think of an example which would demonstrate that the field is not algebraically closed. Any hints would be greatly appreciated...
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    (Linear Algebra) Vector Space and Fields

    Ok So I have shown that F meets all the field axioms, except I am a little stuck on the multiplicative inverse. Let x= a+b\omega So I want some number x^{-1}\times x=1 So I propose that x^{-1} =\frac{1}{a+b \omega} Let \bar{x} =a - b \omega I then manipulate it, multiplying by...
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    (Linear Algebra) Vector Space and Fields

    Homework Statement Let \omega = \frac{1}{2} + \frac{\sqrt7}{2}i(a) Verify that \omega^2 = \omega - 2 (b) Prove that F = \{a + b \omega : a, b \in \mathbb{Q} \} is a field, using the usual operations of addition and multiplication for complex numbers. (c) Recall that we can think of F as a...
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    Generalized coordinates of a couple harmonic oscillator

    bump: so the centre of the plate moves vertically if one of the springs is different? and the generalized coordinates are 2 angles (measuring the tilt in each plane) and a displacement coordinate measuring the displacement of the centre of the plane from it's undisturbed position? how do you...
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    Generalized coordinates of a couple harmonic oscillator

    I got to run now, but I'll have a think about it and hopefully get back to you tomorrow. Thanks for your time Thaakisfox, much appreciated.
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