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Dec 16, 2012 at 12:37 comment added Alexander Isaev Michael, one example of such a polynomial is |z|4+|w|4−4|z|2|w|2+i(|z|2−|w|2).
Dec 15, 2012 at 2:24 answer added Robert Bryant timeline score: 4
Dec 14, 2012 at 19:44 comment added Michael Renardy Do you have an example of such a polynomial that is a function of |z| and |w|? I note that $|z|^2-|w|^2$ does have zeros on the unit sphere.
Dec 14, 2012 at 14:18 answer added Alexandre Eremenko timeline score: 1
Dec 14, 2012 at 13:58 comment added Dima Pasechnik It looks like you have harmonic polynomials on $\mathbb{R}^4$. You can compute the dimensions of the spaces of homogeneous harmonic polynomials, and I guess the condition $f(0)=0$ alone would not suffice to cut out only the functions of $|z|$ and $|w|$.
Dec 14, 2012 at 11:50 comment added Alexander For example, the harmonic function $|z|^2-|w|^2$ is a function of $|z|$ and $|w|$ alone. By the way, in my question I should have probably added "after a linear change of the real variables".
Dec 14, 2012 at 11:31 comment added Michael Renardy Maybe he means a polynomial in z,w,$\bar z$ and $\bar w$.
Dec 14, 2012 at 11:01 comment added Pietro Majer I don't quite understand. A non-constant polynomial $f(z,w)\in\mathbb{C}[z,w]$ is never a function of $|z|$ and $|w|$ alone. Maybe you mean something different?
Dec 14, 2012 at 10:08 history asked Alexander CC BY-SA 3.0