For a complex polynnomialpolynomial $\sum_0^n a_i z^i$ the sum of roots is readily given by the Viets'sVieta's formula.However However, after trying to find out the sum of moduli of roots in terms of the coefficients, I feel like it should not be algebraically computable in terms of coefficients.Then Then I tried to figure out some bounds for the mean of moduli.I I realised that a there we can triviallytrivially compute aa class of boundbounds by replacing each each modulus by some any bound for roots like Cauch'sCauchy's bound .However However, I could not think of some better way.I I have the following questions:
Q.No1Is Is it possible to find some good bounds for the average of the moduli of roots of a complex polynomial with complex roots with known coefficients?
Q.No.2Now Now consider a random polynomial of degree $n$ with coefficients distributed as iid standard normal variates.How How can we find the expectation of the mean of moduli of the roots ,especially especially for finite degree polynomials?a
Of the many things I was trying ,may maybe the following is of some interest.
For any polynomial $\sum_0^n a_i z^i,$ we may note that
$$\text{ |Product of roots| }=\left|\frac{a_0}{a_n} \right|$$
so if $z_{min}$ is the root min minimum modulus,then then $$ |z_{min}| \geq \left(\left|\frac{a_0}{a_n} \right| \right)^{1/n} $$ so that
$$ \frac{\sum_1^n |z_i|}{n} \geq \left(\left|\frac{a_0}{a_n} \right| \right)^{1/n} $$
I don't know ,however however,how how good that bound is and whether we can find some good ones.I I will be obliged for any help/lnkslinks/suggestions
corrected spelling, fixed typo's, improved formatting