All Questions
17
questions
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32
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Schwinger function with and without temperature
I have always been confused with the differences and relation between many-body theory with and without temperature. Suppose I have a theory described by some Hamiltonian $H = H_{0} + V$, where $H_{0}$...
- 1,131
1
vote
0
answers
87
views
Spontaneous breaking of discrete symmetry in d=1+1 at finite temperature and infinite volume
I came across the question of SSB of a discrete symmetry (say, $\mathbb{Z}_2$) symmetry in a QFT in d=1+1 dimensions, at finite temperature, and I have trouble making sense of two different viewpoints ...
2
votes
0
answers
91
views
Hagedorn Temperature of Type I Superstring
In many sources, the Hagedorn temperature of different string theories is given using the high temperature (or high-level limit) $N\gg1$ in the calculation of the string entropy such that:
$$T_H=\left(...
1
vote
1
answer
80
views
Multiple questions on equation 1.6 after deriving Planck's law on page 5 (Schwartz QFT)
After deriving Planck's law for the expectation energy of a single mode, Schwartz takes the limit $L \rightarrow \infty$ and turns the sums into integrals. The average total energy of the blackbody ...
1
vote
1
answer
463
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Currently self-studying QFT and The Standard Model by Schwartz and I'm stuck at equation 1.5 in Part 1 regarding black-body radiation
So basically the equation is basically a derivation of Planck's radiation law and I can't somehow find any resources as to how he derived it by adding a derivative inside. Planck says that each mode ...
5
votes
2
answers
533
views
What does the Temperature of a QFT physically mean?
In elementary statistical mechanics, one can think of temperature as arising from the average kinetic energy of particles in the ensemble. Is there a similar way to think about the temperature of a ...
- 1,055
4
votes
1
answer
1k
views
What is QFT at finite temperature?
On the one hand, according to the Wick rotation that relates Statistical Field Theory and Quantum Field Theory, a finite temperature statistical system corresponds to a compact time quantum field ...
- 1,154
3
votes
0
answers
181
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Why is finite temperature many-body perturbation theory computed in the grand canonical ensemble?
Why does virtually every textbook and paper treat many-body perturbation theory at finite temperature in the grand canonical ensemble? Is it not possible to formulate a canonical theory where all ...
- 1,356
3
votes
1
answer
597
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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
4
votes
0
answers
408
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Equivalence of $d$ dimensional quantum system to $d+1$ dimension stats system
" There are close analogies between quantum field
theories in d dimensions and classical statistical mechanics in d + 1."
What does this statement imply and from where does this extra dimension ...
- 667
8
votes
1
answer
1k
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Matsubara Field Theory - what does imaginary time $\tau$ in $G(\tau,\mathbf{x})$ mean?
Consider the free, real scalar field $\phi$ in Matsubara Finite-Temperature quantum field theory, where our system is kept in equilibrium with a heat bath at temperature $\frac{1}{\beta}$.
Then the ...
- 3,719
5
votes
4
answers
1k
views
Thermal/finite temperature quantum field theory: online lectures and best books
There is nice theme about online lectures on QFT. I would like to know about any online lectures on thermal/finite temperature QFT. Also, I would like to know about some of the best books on thermal/...
19
votes
1
answer
4k
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Quantum field theory: zero vs. finite temperature
I have recently been made aware of the concept of thermal field theory, in which the introductory statement for its motivation is that "ordinary" quantum field theory (QFT) is formulated at zero ...
- 3,063
9
votes
1
answer
889
views
Temperature in the Hamiltonian limit
There is a well known connection between statistical mechanics in D spatial dimensions and quantum field theory in D-1 spatial dimensions. Changing the temperature in statistical mechanics corresponds ...
- 8,815
10
votes
2
answers
966
views
Temperature and Renormalization Scale in QFT
A particle physicist told me that everything in Peskin & Schroder is at zero temperature, and once you consider finite-$T$ QFT, things become more complicated. Meanwhile, I sometimes see people ...
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