# Tagged Questions

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### how can i solve this nonlinear problem?

let be the differential equation in dimension $n > 3$ or $n =3$ $$-\Delta u =|grau|^{2}u$$ (1) with the constraint that the vector 'u' $|u|=1$ then how could i prove that the unitary ...
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### Method to compute fundamental solutions which are distributions

The Malgrange-Ehrenpreis theorem tells us that there is a fundamental solution for any linear differential operator of constants coefficients. The original proof was not constructive (it was based on ...
### Solve $f(x)=\int_{x-1}^{x+1} f(t) \mathrm{d}t$
Solve $f(x)=\int_{x-1}^{x+1} f(t) \mathrm{d}t$. When $f$ is a function, it looks like the only solution is $f(x)=0$. But what if we allow distributions, such as the Dirac delta?
### Solving $x\partial_x f = 0$ over distributions
Solving $x\partial_x f = 0$ over 'normal' functions is the same as solving $\partial_x f = 0$, i.e. one gets $f(x)=c_1$ as the complete answer. But over distributions (if my calculations are ...