I'm having trouble with the following:
Does there exist in $R^3\setminus\{0\}$:
- a vector field F such that $div F = 0$, but is not solenoid (doesn't exist B such that F = ∇ × B)?
- vector field F which is not potential (doesn't exist function $f$ for which is $F = ∇f$), but for which holds $∇×F = 0$?
How to solve this? Can this be generalized on $R^n\setminus \{0\}?$
Any help is welcome. Thanks in advance.