All Questions
12
questions
2
votes
0
answers
76
views
Different ways to understand fermions [closed]
I first learned about fermions in my atomic physics class, where the teacher said that electrons obey the Pauli exclusion principle. Later, in my quantum mechanics class, I learned about identical ...
- 368
1
vote
0
answers
65
views
System interacting with Fermi Gas
My question denoted by a reduced dynamic for a system interacting with a reservoir.
Before asking the question, for completeness I will write in detail the statement of the problem and notation.
...
- 33
3
votes
1
answer
155
views
Mean field and interacting Dirac QFT: channels and spinors
I am dealing with a QFT of Dirac fermions with an interaction term
$$L_I=\bar\psi\psi\bar\psi\psi=\psi^\dagger\gamma^0\psi\psi^\dagger\gamma^0\psi,$$
with $\gamma^0$ a Dirac matrix and $\psi$, $\psi^\...
- 503
0
votes
0
answers
110
views
Technique for diagonalising this free spinless fermionic Hamiltonian?
How does one diagonalise the following Hamiltonian?
$$
H = \sum_n \epsilon_n c^\dagger_n c_n + g \sum_n (c^\dagger_n c^\dagger_{-n} + c_{-n}c_n),
$$
where $c_n$ is a spineless fermionic op. Clearly we ...
- 1,544
2
votes
2
answers
1k
views
Using Grassmann variables on fermionic theories
I think the best way to put my question is the following: what (fermionic) theories make use of Grassmann variables?
Let me clarify my question a little further. I remember some discussions in quantum ...
- 585
1
vote
0
answers
61
views
Derivation of fermionic partition function, how does commutation work?
When deriving the fermionic partition function with coherent states $|\psi\rangle$ we make the following step
$$
\mathcal Z=\int d(\bar\psi,\psi)\ e^{-\sum_i\bar\psi_i \psi_i}\sum_n\langle n|\psi\...
- 23
6
votes
1
answer
993
views
Boundary (Anti)Periodic conditions and fermion partition functions
The path integral with antiperiodic fermions (Neveu-Schwarz spin structure) on a circle of circumference $\beta$, in a theory with Hamiltonian $H$, has partition function
$$ \rm{Tr} \exp(−\beta H)$$
...
- 4,336
1
vote
1
answer
201
views
Second quantisation for fermions
I am trying to build a model for reactions on a lattice in the Doi-Peliti formalism. Suppose there exists a lattice of $N$ sites indexed by $i$. Each site can be either occupied or unoccupied. ...
- 141
3
votes
1
answer
785
views
Quantum statistics from the (anti)commutation relations of the operators?
From a QFT point of view, the difference between bosons and fermions is that their creation/annihilation operators ($a^{\dagger}$, $a$ and $c^{\dagger}$, $c^{\dagger}$ respectively) obey the following ...
- 24.9k
1
vote
0
answers
320
views
Fermion boundary condition for a thermal compact circle
Is this true that for fermion statistical systems
in the thermal phase, with Euclidean time,
$$
\beta=1/T=t_E
$$
the Euclidean time will be chosen to be anti-periodic for fermion boundary ...
- 4,336
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
13
votes
5
answers
3k
views
Fermion boundary conditions at finite temperature
In a finite temperature QFT, fermions must obey anti-periodic boundary conditions.
What is the reason for this?
- 321