The analyticity tag has no wiki summary.
11
votes
4answers
677 views
Is the world $C^\infty$?
While it is quite common to use piecewise constant functions to describe reality, e.g. the optical properties of a layered system, or the Fermi–Dirac statistics at (the impossible to reach exactly) ...
11
votes
5answers
472 views
Binary Black Hole Solution of General Relativity?
This is rather a technical question for experts in General Relativity. An accessible link would be an accepable answer, although any additional discussion is welcome.
GR has well known solutions ...
3
votes
1answer
478 views
Is there an analytical solution for fluid flow in a square duct?
I couldn't find one but assumed it must exist. Tried to find it on the back of an envelope, but got to an ugly differential equation I can't solve.
I'm assuming a square duct of infinite length, ...
7
votes
4answers
2k views
What is the connection between Poisson brackets and commutators?
The Poisson bracket is defined as:
$$\{f,g\} = \sum_{i=1}^{N} \left[
\frac{\partial f}{\partial q_{i}} \frac{\partial g}{\partial p_{i}} -
\frac{\partial f}{\partial p_{i}} \frac{\partial ...
4
votes
1answer
320 views
A confusion from Weinberg's QFT text (a vanishing term in Lippmann-Schwinger equation)
I was reviewing the first few chapters of Weinberg Vol I and found a hole in my understanding in page 112, where he tried to show in the asymptotic past $t=−∞$, the in states coincide with a free ...
