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On maximum modulus of polynomials. - MaRDI portal

On maximum modulus of polynomials. (Q2711297)

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On maximum modulus of polynomials.
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    30 October 2001
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    modulus of polynomial
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    On maximum modulus of polynomials. (English)
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    Let \(f\) be an arbitrary entire function and let \(M(f,r)= \max_{ | z|=r} | f(z)|\). If it is known that for every polynomial \(p\) of degree \(n\) we have NEWLINE\[NEWLINEM(p,kR) \leq{R^n+R^n \over 2}M(p,k),\quad R\geq 1,k> 0,NEWLINE\]NEWLINE NEWLINE\[NEWLINEM(p,kR) \geq\left({1+R \over 2}\right)^n \left({2R\over 1+R}\right)^n M(p,k)= R^nM(p,k),\;k>0,\;0<R\leq 1.NEWLINE\]NEWLINE If \(p\) has no zeros in \(| z|<k\), then NEWLINE\[NEWLINEM (p,kR)\leq {R^n+1\over 2}M(p,k),\;R\geq 1,\;k>0,NEWLINE\]NEWLINE NEWLINE\[NEWLINEM(p,kR)\geq \left({1+R \over 2} \right)^n M(p,k),\;0<R\leq 1,\;k>0.NEWLINE\]NEWLINE NEWLINENEWLINEIn this paper are investigated the cases if some but not all the zeros of a polynomial \(p\) lie in \(| z|<k\). The following conjecture is investigated. NEWLINENEWLINEConjecture: If \(p\) is a polynomial of degree \(n\), then NEWLINE\[NEWLINEM(p,kR)\leq {R^n+R^{n(k,0)} \over 2}M(p,k),\;R\geq 1,\;k>0,NEWLINE\]NEWLINE NEWLINE\[NEWLINEM(p,kR) \geq\left( {1+R\over 2}\right)^n \left({2R\over 1+R}\right)^{n (k,0)}M (p,k),\;k>0,\;0<R\leq 1,NEWLINE\]NEWLINE where \(n(k,0)\) is equal to the number of zeros of \(p\) in \(| z|\leq k\).NEWLINENEWLINEFor the entire collection see [Zbl 0958.00011].
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