All Questions
Tagged with quantum-field-theory partition-function
40
questions with no upvoted or accepted answers
7
votes
0
answers
904
views
Physical origin of Nekrasov Partition Function
I've seen a few papers [1,2,3,4] which defined Nekrasov Partition Function as (in particular [2,3,4])
\begin{equation}
Z(\mathbf{a}, \epsilon_1,\epsilon_2,\Lambda) := \sum_{n = 0}^\infty \Lambda^n\...
- 595
6
votes
0
answers
232
views
Operator insertions vs boundary conditions in AdS/CFT
This question is motivated by AdS/CFT, but really it's just about AdS quantum gravity. Consider quantum gravity in asymptotically AdS spacetime. For simplicity, assume there are no matter fields: the ...
- 1,455
6
votes
0
answers
197
views
How does anomaly inflow work in terms of the eta invariant?
I'm trying to understand the non-perturbative picture of anomaly inflow, mainly following these two articles by Witten and Yonekura:
[1] - https://arxiv.org/pdf/1909.08775.pdf ,
[2] - https://arxiv....
- 61
5
votes
0
answers
78
views
How many Lagrangians can a QFT have?
I just stumbled across a presentation by Tachikawa about "What is Quantum Field Theory". He has an interesting perspective that we should think of (at least a subset of) quantum field ...
- 1,014
4
votes
0
answers
60
views
Thermodynamic free energy of interacting system
This question concerns an interacting system's thermodynamic free energy $\Omega$. Generally speaking, The action $S$ for an interacting system has the following form:
\begin{equation}
S(\phi,\psi) = ...
- 2,038
4
votes
0
answers
100
views
Functional determinant: linking Series, Heat-Kernel and Zeta function
I would like to express a functional determinant as a series of diagrams, using the zeta function renormalization applied to the heat-kernel method, but I don't know if it's possible. Let me explain:
...
- 2,613
4
votes
0
answers
188
views
Feynman Rules from Generating Functional
For the following Lagrangian:
$$\mathcal{L}= \overline \psi \left(i \gamma^{\mu}D_{\mu} - m \right)\psi -\frac{1}{2}\left(F_{\mu\nu}\right)^2,$$
I'm trying to find the Feynman rules. I know that the ...
- 1,213
4
votes
0
answers
311
views
Extra $i$ in grand canonical partition function: why the Wick rotation?
Going through my notes I stumbled upon something I can't wrap my head around.
I'd like to write the grand canonical partition function for a system of identical charged particles (charge $e$) ...
- 616
3
votes
0
answers
43
views
Physical observables in the XY/sine-Gordon duality
My question is, during the duality map, real physical quantities seem to acquire a prefactor of $i$ and become purely imaginary. And I feel uncomfortable.
Take bosonic current for example. Consider ...
- 91
3
votes
0
answers
45
views
Is it OK to do this manipulation at the partition function level? (auxiliary fields in quadratic gravity)
Background
I am working with the following action in the Euclidean signature ($C^2$ is the Weyl quadratic term):
\begin{equation}
S_B = -\frac{1}{2\kappa^2}\int d^4x\sqrt{g}\left(2\Lambda_C+\zeta R-\...
- 2,613
3
votes
0
answers
158
views
Wouldn't a simple scalar field fix the non-renormalizability of gravity?
It is well known that quadratic gravity is renormalizable. On the other hand it is possible to transform the partition function of Einstein-Hilbert + free minimally coupled complex scalar field into a ...
- 2,613
3
votes
0
answers
66
views
About the various ensembles in Thermodynamics
The properties of a system in thermodynamical equilibrium are described by a partition function:
$$
\mathcal{Z} = \text{Tr} \ e^{-\beta E} = \sum_n e^{-\beta E_n}
$$
This defines so called canonical ...
- 4,883
2
votes
0
answers
32
views
Question about the measure in the partition function of a lattice Yang-Mills theory
This can seem like a dumb question but the partition function of a lattice pure gauge field theory in euclidean space is:
\begin{equation}
Z=\int \prod_{x,\mu} dU_\mu(x)\,e^{-S_W[U_\mu(x)]}\,\,\,,\,\,\...
- 2,613
2
votes
0
answers
148
views
Indexes in the Gaussian functional integral
This is a question spawning from a comment made to my previous question. There I was asking about taking some functional derivative in the effective action of the non-linear sigma model. The comment ...
- 6,067
2
votes
0
answers
148
views
Physical meaning of $\langle 0|S(+\infty,-\infty)|0 \rangle$
when I am reading text book Introduction to Many body physics Piers Coleman 2nd editor, Equation (5.26). I got confused about the meaning of $\langle0|S(+\infty,-\infty)|0\rangle$.
first problem
$|...
- 1,113