Generalized polar varieties and an efficient real elimination

Bernd Bank; Marc Giusti; Joos Heintz; Luis M. Pardo

Kybernetika (2004)

  • Volume: 40, Issue: 5, page [519]-550
  • ISSN: 0023-5954

Abstract

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Let W be a closed algebraic subvariety of the n -dimensional projective space over the complex or real numbers and suppose that W is non-empty and equidimensional. In this paper we generalize the classic notion of polar variety of W associated with a given linear subvariety of the ambient space of W . As particular instances of this new notion of generalized polar variety we reobtain the classic ones and two new types of polar varieties, called dual and (in case that W is affine) conic. We show that for a generic choice of their parameters the generalized polar varieties of W are empty or equidimensional and, if W is smooth, that their ideals of definition are Cohen-Macaulay. In the case that the variety W is affine and smooth and has a complete intersection ideal of definition, we are able, for a generic parameter choice, to describe locally the generalized polar varieties of W by explicit equations. Finally, we use this description in order to design a new, highly efficient elimination procedure for the following algorithmic task: In case, that the variety W is -definable and affine, having a complete intersection ideal of definition, and that the real trace of W is non-empty and smooth, find for each connected component of the real trace of W a representative point.

How to cite

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Bank, Bernd, et al. "Generalized polar varieties and an efficient real elimination." Kybernetika 40.5 (2004): [519]-550. <http://eudml.org/doc/33718>.

@article{Bank2004,
abstract = {Let $W$ be a closed algebraic subvariety of the $n$-dimensional projective space over the complex or real numbers and suppose that $W$ is non-empty and equidimensional. In this paper we generalize the classic notion of polar variety of $W$ associated with a given linear subvariety of the ambient space of $W$. As particular instances of this new notion of generalized polar variety we reobtain the classic ones and two new types of polar varieties, called dual and (in case that $W$ is affine) conic. We show that for a generic choice of their parameters the generalized polar varieties of $W$ are empty or equidimensional and, if $W$ is smooth, that their ideals of definition are Cohen-Macaulay. In the case that the variety $W$ is affine and smooth and has a complete intersection ideal of definition, we are able, for a generic parameter choice, to describe locally the generalized polar varieties of $W$ by explicit equations. Finally, we use this description in order to design a new, highly efficient elimination procedure for the following algorithmic task: In case, that the variety $W$ is $\mathbb \{Q\}$-definable and affine, having a complete intersection ideal of definition, and that the real trace of $W$ is non-empty and smooth, find for each connected component of the real trace of $W$ a representative point.},
author = {Bank, Bernd, Giusti, Marc, Heintz, Joos, Pardo, Luis M.},
journal = {Kybernetika},
keywords = {Geometry of polar varieties and its generalizations; geometric degree; real polynomial equation solving; elimination procedure; arithmetic circuit; arithmetic network; complexity; polar variety; geometric degree; elimination procedure; arithmetic circuit; arithmetic network; complexity},
language = {eng},
number = {5},
pages = {[519]-550},
publisher = {Institute of Information Theory and Automation AS CR},
title = {Generalized polar varieties and an efficient real elimination},
url = {http://eudml.org/doc/33718},
volume = {40},
year = {2004},
}

TY - JOUR
AU - Bank, Bernd
AU - Giusti, Marc
AU - Heintz, Joos
AU - Pardo, Luis M.
TI - Generalized polar varieties and an efficient real elimination
JO - Kybernetika
PY - 2004
PB - Institute of Information Theory and Automation AS CR
VL - 40
IS - 5
SP - [519]
EP - 550
AB - Let $W$ be a closed algebraic subvariety of the $n$-dimensional projective space over the complex or real numbers and suppose that $W$ is non-empty and equidimensional. In this paper we generalize the classic notion of polar variety of $W$ associated with a given linear subvariety of the ambient space of $W$. As particular instances of this new notion of generalized polar variety we reobtain the classic ones and two new types of polar varieties, called dual and (in case that $W$ is affine) conic. We show that for a generic choice of their parameters the generalized polar varieties of $W$ are empty or equidimensional and, if $W$ is smooth, that their ideals of definition are Cohen-Macaulay. In the case that the variety $W$ is affine and smooth and has a complete intersection ideal of definition, we are able, for a generic parameter choice, to describe locally the generalized polar varieties of $W$ by explicit equations. Finally, we use this description in order to design a new, highly efficient elimination procedure for the following algorithmic task: In case, that the variety $W$ is $\mathbb {Q}$-definable and affine, having a complete intersection ideal of definition, and that the real trace of $W$ is non-empty and smooth, find for each connected component of the real trace of $W$ a representative point.
LA - eng
KW - Geometry of polar varieties and its generalizations; geometric degree; real polynomial equation solving; elimination procedure; arithmetic circuit; arithmetic network; complexity; polar variety; geometric degree; elimination procedure; arithmetic circuit; arithmetic network; complexity
UR - http://eudml.org/doc/33718
ER -

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