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Results tagged with quantum-field-theory
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user 46485
Quantum Field Theory (QFT) is the theoretical framework describing the quantisation of classical fields which allows a Lorentz-invariant formulation of quantum mechanics. QFT is used both in high energy physics as well as condensed matter physics and closely related to statistical field theory. Use this tag for many-body quantum-mechanical problems and the theory of particle physics. Don’t combine with the [quantum-mechanics] tag.
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General properties of Matsubara frequency summations
By properties such as linearity, shifting, commutativity, etc. I was hoping to evaluate something like,
$$S_\eta = \dfrac{1}{\beta}\displaystyle\sum_{i\omega} \dfrac{i\omega-\xi_1}{[(i\omega-\xi_2)^2 …
4
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1
answer
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Hubbard-Stratonovich transformation and decoupling channels
I'm studying an example of the Hubbard-Stratonovich transformation in Altland and Simons' Condensed Matter Field Theory (2nd ed.), pp. 246-247.
In it they say that...
one is frequently confronte …
10
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3
answers
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Why are Grassmann fields never classical?
I see this statement in many QFT books (e.g. Altland & Simons' Condensed Matter Field Theory) but the author never explains why.
Can you briefly explain why Grassmann fields never have a classical me …
4
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1
answer
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Analysing decoupling channels in Hubbard-Stratonovich transformation
I have an action defined in terms of fermionic fields $c$ and $d$ that looks like
$$S = - \bar{d}(t)\bar{c}(t') V(t,t') d(t')c(t)$$
where $V$ is an interaction matrix.
Then performing Hubbard-Straton …