6
votes
Accepted
Systems of (hyperbolic) 2nd order PDEs with lower order constraints
Yes, there is a standard procedure to analyze such systems, essentially, it is Cartan's method of prolongation combined with his theory of involutive systems. There are other approaches as well, but ...
- 106k
5
votes
Accepted
Wick product of free fields and wave front sets in the sense of Lars Hörmander
The answer to both questions is no. This is due to two facts:
The Klein-Gordon two-point distribution $\omega_2(x,y)=\langle\Omega,\phi(x)\phi(y)\Omega\rangle$ in $\mathbb{R}^4$, where $\Omega_1=\...
- 7,099
1
vote
Accepted
Recursive relation to represent the last element of a matrix using determinant
Check out https://en.wikipedia.org/wiki/Minor_(linear_algebra)
Cramer's rule says that
$$R^{(N+1)}=\frac{1}{\det M^{(N+1)}}C^\top,$$
with $C$ the cofactor matrix of $M^{(N+1)}$. The $(N+1,N+1)$ ...
- 178k
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