# Questions tagged [thermal-field-theory]

Thermal Field Theory or Finite Temperature Field Theory deals with of methods to calculate expectation values of physical observables of a Quantum Field Theory at finite temperature.

64 questions
Filter by
Sorted by
Tagged with
36 views

### Partition function for a system in local thermal equilibrium

For a system in equilibrium, the partition function is standard. But if the system is in local thermal equilibrium but stationary (i.e. zero or negligible time variation), but the temperature varies ...
43 views

26 views

### Higgs self-energy at finite temperature

Is there anybody know of a reference that calculates the Higgs self-energy at finite temperature, say in a Standard Model plasma?
156 views

### How does QED at a finite temperature differ from QED at zero temperature?

Currently, I do not have any knowledge of finite temperature field theory. But I have learnt ordinary QFT calculations and I am reasonably familiar with Statistical mechanics. With this background, I ...
50 views

### How to calculate thermal corrected masses of Higgs and Gauge bosons?

How are the self energies of scalars and gauge bosons at finite temperature calculated in the process of determining the 1-loop resummation of Debye masses? I have seen some papers where the explicit ...
22 views

### Conceptual Problems in Understanding Thermal Field States in nonrelativistic QED

I have conceptual problems understanding the notion of thermal states in the context of nonrelatistic (cavity) QED. My main problem is the definition of temperature associated to the (quantized) ...
35 views

### Time dependence of Drude-like correlation function obtained from Matsubara formalism

I'm trying to calculate the real time dependence of the correlation function that I've obtained in my effective model (it is closely related to the electron density correlation function), given in ...
71 views

### Cross-sections at zero temperature and high temperature for a process and its reverse

If the Feynman amplitude for a $2-2$ forward scattering $ab\to cd$ is denoted by $\mathcal{M}_{ab\to cd}$ and that of the reverse scattering process, $cd\to ab$, is denoted by $\mathcal{M}_{cd\to ab}$...
56 views

### Why is chaos a common property of thermal systems?

https://arxiv.org/abs/1811.06949 pg 3 mentions that chaos is a common property of thermal systems. Can someone please explain why that is? While looking at , I found that indeed most examples ...
30 views

184 views

### Temperature and Witten index

Assume that the spectrum of some supersymmetric theory is discrete, then the Witten index is expected to be independent of temperature given by $T = 1/\beta$. However, it is well-known (see this) that ...
71 views

86 views

### Estimate of trace of powers of density matrix

Given a very generic, lower bounded Hamiltonian, is there a estimate on how $Tr(\rho^{1/k})$ grows as $k>0$ increases? Does this quantity diverge as a function of $N$, the degrees of freedom of the ...
188 views

### Finite temperature quantum mechanics and mixed states

Is it necessarily true that a quantum-mechanical system in thermal equilibrium is in a mixed state? If so, why is this the case? Is there any physical intuition as to why one cannot use a pure state ...
110 views

1k views

### What are thermal photons?

What is the difference between an ordinary photon and a thermal photon? Do thermal photons act as an exchange particle for any forces similar to an ordinary photon which acts as an exchange particle ...
85 views

### Thermal field theory of isolated electroweak plasma

I need to understand something specific. The theory of electroweak temperature says that when you have a plasma of particles at energy above the electroweak phase transition (100 GeV). The Higgs ...
408 views

2k views

### is there any relation between the emissivity and the temperature?

I was just wondering if there is any relation between the emissivity and the temperature (i.e. temperature as a function of the emissivity). If yes, can you write the relation and cite a reference ...
351 views

### Quantum critical region governed by quantum critical point

I am trying to understand the following statement about quantum critical regions associated with a quantum phase transition from page 4 of these lecture notes on holographic superconductors: The ...
Why did the decay rate of the dark matter particles fall when the temperature of the Universe $T_U$ dropped below dark matter mass $M_{DM}$? In particular, why can it not decay into lighter particles ...