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Papers by Santanu Bag
Annals of Functional Analysis, 2021
We obtain bounds for the numerical radius of 2 × 2 operator matrices which improve on the existin... more We obtain bounds for the numerical radius of 2 × 2 operator matrices which improve on the existing bounds. We also show that the inequalities obtained here generalize the existing ones. As an application of the results obtained here we estimate the bounds for the zeros of a monic polynomial and illustrate with numerical examples that the bounds are better than the existing ones.
Applied Mathematics and Computation, 2013
ABSTRACT The estimation of zeros of a polynomial have been done by many mathematicians over the y... more ABSTRACT The estimation of zeros of a polynomial have been done by many mathematicians over the years using various approaches. In this paper we estimate the upper bound for the zeros of a given polynomial using Hilbert space technique involving Frobenius companion matrix and numerical radius. We first obtain numerical range and numerical radius for certain class of matrices and use them to estimate the bounds for zeros of a given polynomial. We illustrate with examples to show that the estimations obtained here is better than the previously known estimations. We also obtain a sequence of real numbers which converges exactly to the spectral radius of some special class of matrices.
Annals of Functional Analysis, 2021
We obtain bounds for the numerical radius of 2 × 2 operator matrices which improve on the existin... more We obtain bounds for the numerical radius of 2 × 2 operator matrices which improve on the existing bounds. We also show that the inequalities obtained here generalize the existing ones. As an application of the results obtained here we estimate the bounds for the zeros of a monic polynomial and illustrate with numerical examples that the bounds are better than the existing ones.
Applied Mathematics and Computation, 2013
ABSTRACT The estimation of zeros of a polynomial have been done by many mathematicians over the y... more ABSTRACT The estimation of zeros of a polynomial have been done by many mathematicians over the years using various approaches. In this paper we estimate the upper bound for the zeros of a given polynomial using Hilbert space technique involving Frobenius companion matrix and numerical radius. We first obtain numerical range and numerical radius for certain class of matrices and use them to estimate the bounds for zeros of a given polynomial. We illustrate with examples to show that the estimations obtained here is better than the previously known estimations. We also obtain a sequence of real numbers which converges exactly to the spectral radius of some special class of matrices.