首页 | 本学科首页   官方微博 | 高级检索  
     检索      


Algebraic polynomials with non-identical random coefficients
Authors:K Farahmand  A Nezakati
Institution:Department of Mathematics, University of Ulster at Jordanstown, Co. Antrim, BT37 0QB, United Kingdom ; Department of Statistics, School of Mathematical Sciences, Ferdowsi University of Mashhad, P.O. Box 1159-91775, Mashhan, Iran
Abstract:There are many known asymptotic estimates for the expected number of real zeros of a random algebraic polynomial $a_0 +a_1 x+ a_2 x^2+ \cdots +a_{n-1}x^{n-1}.$ The coefficients $a_j$ $(j=0, 1, 2, \dotsc, n-1)$ are mostly assumed to be independent identical normal random variables with mean zero and variance unity. In this case, for all $n$ sufficiently large, the above expected value is shown to be $O(\log n)$. Also, it is known that if the $a_j$ have non-identical variance $\binom{n-1}{j}$, then the expected number of real zeros increases to $O(\sqrt{n})$. It is, therefore, natural to assume that for other classes of distributions of the coefficients in which the variance of the coefficients is picked at the middle term, we would also expect a greater number of zeros than $O(\log n)$. In this work for two different choices of variance for the coefficients we show that this is not the case. Although we show asymptotically that there is some increase in the number of real zeros, they still remain $O(\log n)$. In fact, so far the case of $\mbox{var}(a_j)={\binom{n-1}{j}}$ is the only case that can significantly increase the expected number of real zeros.

Keywords:Number of real zeros  real roots  random algebraic polynomials  Kac-Rice formula  non-identical random variables
点击此处可从《Proceedings of the American Mathematical Society》浏览原始摘要信息
点击此处可从《Proceedings of the American Mathematical Society》下载免费的PDF全文
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号