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Results tagged with correlation-functions
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user 97158
A correlation function is a statistical correlation between random variables at two different points in space, time, or other parameter space, usually as a function of the variable distance between these points. In QFT, field autocorrelation functions are propagators, so use the "propagator" tag, instead.
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What does the correlation function look like in first-order transition?
I know the correlation function for critical phenomena $$G(r)\sim \frac{1}{|r|^{d-2+\eta}}$$ for $r\ll \xi$ and $$G(r)\sim e^{-|r|/\xi}$$ for $r\gg\xi$.
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How to derive the long range behavior of XY model?
In a lecture note (Lec 23) by Sachdev (https://canvas.harvard.edu/courses/76589/files/folder/Lectures?), he considers a model
$$Z=\int D\theta(x)\,exp(-\frac{K}{2\pi}\int d^{2}x\,(\nabla_x\theta)^2),$ …
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Correlation Function of One-Dimensional XY Model
It seems that we can also use a trick in Xiao-Gang Wen's book (Quantum field theory of many body systems, page 93).
Now $\mathcal{L}=\frac{K}{2\pi}(\partial_x\theta)^2$, then the correlation function …
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How to calculate the correlation function like $\langle \partial_i \phi(x) \partial_j\phi(0)...
From the standard text book about quantum field theory, we know that if we consider $$\mathcal{L}=\frac{1}{2}(\partial_{\mu} \phi)^2-\frac{m^2}{2}\phi^2,$$ the partition function of this Gaussian theo …
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