L p inequalities for the growth of polynomials with restricted zeros

Nisar A. Rather; Suhail Gulzar; Aijaz A. Bhat

Archivum Mathematicum (2022)

  • Volume: 058, Issue: 3, page 159-167
  • ISSN: 0044-8753

Abstract

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Let P ( z ) = ν = 0 n a ν z ν be a polynomial of degree at most n which does not vanish in the disk | z | < 1 , then for 1 p < and R > 1 , Boas and Rahman proved P ( R z ) p ( R n + z p / 1 + z p ) P p . In this paper, we improve the above inequality for 0 p < by involving some of the coefficients of the polynomial P ( z ) . Analogous result for the class of polynomials P ( z ) having no zero in | z | > 1 is also given.

How to cite

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Rather, Nisar A., Gulzar, Suhail, and Bhat, Aijaz A.. "$L_{p}$ inequalities for the growth of polynomials with restricted zeros." Archivum Mathematicum 058.3 (2022): 159-167. <http://eudml.org/doc/298353>.

@article{Rather2022,
abstract = {Let $P(z)=\sum _\{\nu =0\}^\{n\}a_\{\nu \}z^\{\nu \}$ be a polynomial of degree at most $n$ which does not vanish in the disk $|z|<1$, then for $1\le p<\infty $ and $R>1$, Boas and Rahman proved \[\left\Vert P(Rz)\right\Vert \_\{p\}\le \big (\left\Vert R^\{n\}+z\right\Vert \_\{p\}/\left\Vert 1+z\right\Vert \_\{p\}\big )\left\Vert P\right\Vert \_\{p\}.\] In this paper, we improve the above inequality for $0\le p < \infty $ by involving some of the coefficients of the polynomial $P(z)$. Analogous result for the class of polynomials $P(z)$ having no zero in $|z|>1$ is also given.},
author = {Rather, Nisar A., Gulzar, Suhail, Bhat, Aijaz A.},
journal = {Archivum Mathematicum},
keywords = {polynomials; integral inequalities; complex domain},
language = {eng},
number = {3},
pages = {159-167},
publisher = {Department of Mathematics, Faculty of Science of Masaryk University, Brno},
title = {$L_\{p\}$ inequalities for the growth of polynomials with restricted zeros},
url = {http://eudml.org/doc/298353},
volume = {058},
year = {2022},
}

TY - JOUR
AU - Rather, Nisar A.
AU - Gulzar, Suhail
AU - Bhat, Aijaz A.
TI - $L_{p}$ inequalities for the growth of polynomials with restricted zeros
JO - Archivum Mathematicum
PY - 2022
PB - Department of Mathematics, Faculty of Science of Masaryk University, Brno
VL - 058
IS - 3
SP - 159
EP - 167
AB - Let $P(z)=\sum _{\nu =0}^{n}a_{\nu }z^{\nu }$ be a polynomial of degree at most $n$ which does not vanish in the disk $|z|<1$, then for $1\le p<\infty $ and $R>1$, Boas and Rahman proved \[\left\Vert P(Rz)\right\Vert _{p}\le \big (\left\Vert R^{n}+z\right\Vert _{p}/\left\Vert 1+z\right\Vert _{p}\big )\left\Vert P\right\Vert _{p}.\] In this paper, we improve the above inequality for $0\le p < \infty $ by involving some of the coefficients of the polynomial $P(z)$. Analogous result for the class of polynomials $P(z)$ having no zero in $|z|>1$ is also given.
LA - eng
KW - polynomials; integral inequalities; complex domain
UR - http://eudml.org/doc/298353
ER -

References

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  2. Arestov, V., 10.1070/IM1982v018n01ABEH001375, Math. USSR-Izv 18 (1982), 1–17. (1982) MR0607574DOI10.1070/IM1982v018n01ABEH001375
  3. Aziz, A., 10.1016/0021-9045(88)90089-5, J. Approx. Theory 55 (1988), 232–239. (1988) MR0965219DOI10.1016/0021-9045(88)90089-5
  4. Boas, R.P., Rahman, Q.I., 10.1007/BF00253927, Arch. Rational Mech. Anal. 11 (1962), 34–39. (1962) MR0158994DOI10.1007/BF00253927
  5. Pólya, G., Szegö, G., Aufgaben and Lehrsätze aus der Analysis, Springer-Verlag, Berlin, 1925. (1925) MR0015435
  6. Rahman, Q.I., Schmeisser, G., Analytic theory of polynomials, Oxford University Press, 1922. (1922) MR1954841
  7. Rahman, Q.I., Schmeisser, G., 10.1016/0021-9045(88)90073-1, J. Approx. Theory 53 (1988), 26–32. (1988) MR0937140DOI10.1016/0021-9045(88)90073-1
  8. Royden, H.L., Real Analysis, Macmillan Pub. Co., Inc., New York, 1968. (1968) MR0151555
  9. Turán, P., Über die Ableitung von Polynomen, Compositio Math. 7 (1939), 89–95. (1939) MR0000228

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