All Questions
Tagged with quantum-field-theory statistical-mechanics
48
questions
13
votes
2
answers
6k
views
Intuition behind Linked Cluster Theorem: connected vs. non-connected diagrams
Within statistical physics and quantum field theory, the linked cluster theorem is widely used to simplify things in the calculation of the partition function among other things.
My question has the ...
- 7,931
64
votes
2
answers
7k
views
Why do we expect our theories to be independent of cutoffs?
Final edit: I think I pretty much understand now (touch wood)! But there's one thing I don't get. What's the physical reason for expecting the correlation functions to be independent of the cutoff? I....
- 7,936
63
votes
4
answers
6k
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How exact is the analogy between statistical mechanics and quantum field theory?
Famously, the path integral of quantum field theory is related to the partition function of statistical mechanics via a Wick rotation and there is therefore a formal analogy between the two. I have a ...
- 3,492
35
votes
1
answer
4k
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What's the relation between Wilson Renormalization Group (RG) in Statistical Mechanics and QFT RG?
What's the relation between Wilson Renormalization Group(RG) in Statistical Mechanics and QFT RG? For easier to compare, I choose scalar $\phi^4$ in both cases.
Wilson RG:
Given $\phi^4$ model,
$$Z=...
- 2,147
30
votes
2
answers
5k
views
What is the difference between scale invariance and self-similarity?
I always thought that these two terms are some kind of synonyms, meaning that if you have a self-similar or scale invariant system, you can zoom in or out as you like and you will always see the same ...
- 9,581
25
votes
4
answers
4k
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What is a simple intuitive way to see the relation between imaginary time (periodic) and temperature relation?
I guess I never had a proper physical intuition on, for example, the "KMS condition". I have an undergraduate student who studies calculation of Hawking temperature using the Euclidean path ...
- 727
19
votes
1
answer
2k
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Mermin-Wagner and graphene
I have been told that the Mermin-Wagner theorem disallows the existence of the crystal of graphene. However, I don't have enough knowledge to understand the Mermin-Wagner theorem. If possible can ...
- 487
19
votes
2
answers
2k
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Proof of Loss of Lorentz Invariance in Finite Temperature Quantum Field Theory
In the standard quantum field theory we always take the vacuum to be a invariant under Lorentz transformation. For simple cases, at least for free fields, is very simple to actually prove this.
Now ...
- 2,589
16
votes
3
answers
2k
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Is decoherence even possible in anti de Sitter space?
Is decoherence even possible in anti de Sitter space? The spatial conformal boundary acts as a repulsive wall, thus turning anti de Sitter space into an eternally closed quantum system. Superpositions ...
- 161
13
votes
1
answer
2k
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Why does Landau theory not fail when dealing with a first order phase transition?
Here is a problem where I can do the calculation, but I am not understanding the philosophy behind it. It is about Landau theory:
The Landau theory of phase transitions is based on the idea that the ...
user21090
11
votes
1
answer
2k
views
Chemical potential in quantum field theories
The chemical potential enters the grand canonical ensemble, in statistical physics, as the Lagrange multiplier ensuring the conservation of particle number.
In QFT and relativistic theories in ...
- 24.9k
10
votes
2
answers
758
views
Spontaneous symmetry breaking: proving the equivalence of two definitions
This question can be posed for both quantum and classical set-ups. For concreteness, let me consider a local, classical Hamiltonian $H$. The expectation values I consider are with respect to the usual ...
- 9,081
8
votes
2
answers
2k
views
Connection between QFT and statistical physics of phase transitions
I have heard that there is a deep connection between QFT (emphasized by its path-integral formulation) and statistical physics of critical systems and phase transitions.
I have only a basic course in ...
user41404
4
votes
3
answers
263
views
Generating nonlinearities in renormalization group
In renormalization group (RG) calculations as performed in statistical physics (for example for Landau-Ginzburg theory - often a la Wilson), the first step is to coarse-grain the theory by integrating ...
- 498
3
votes
1
answer
597
views
Finite temperature quantum field theory
In a QFT at finite temperature we consider the Euclidean time to be periodic, i.e. we consider a theory on the manifold $\mathbb{R}^{d - 1} \times S^1$, where the spatial coordinates are in $\mathbb{R}...
- 401