%0 Journal Article %T A universal constant for semistable limit cycles %A Art¨¦s %A Joan C. %A Llibre %A Jaume %A Teixeira %A Marco Antonio %J Computational & Applied Mathematics %D 2011 %I Scientific Electronic Library Online %R 10.1590/S1807-03022011000200012 %X we consider one-parameter families of 2-dimensional vector fields x¦Ì having in a convenient region r a semistable limit cycle of multiplicity 2m when ¦Ì = 0, no limit cycles if ¦Ì < 0, and two limit cycles one stable and the other unstable if ¦Ì > 0. we show, analytically for some particular families and numerically for others, that associated to the semistable limit cycle and for positive integers n sufficiently large there is a power law in the parameter ¦Ì of the form ¦Ìn ¡Ö cn¦Á< 0 with c, ¦Á ¡Ê r, such that the orbit of x¦Ìn through a point of p ¡Ê r reaches the position of the semistable limit cycle of x0 after given n turns. the exponent ¦Á of this power law depends only on the multiplicity of the semistable limit cycle, and is independent of the initial point p ¡Ê r and of the family x¦Ì. in fact ¦Á = -2m/(2m - 1). moreover the constant c is independent of the initial point p ¡Ê r, but it depends on the family x¦Ì and on the multiplicity 2m of the limit cycle ¦Ã. %K semistable limit cycle %K semistable fixed point %K universal constant %K power law. %U http://www.scielo.br/scielo.php?script=sci_abstract&pid=S1807-03022011000200012&lng=en&nrm=iso&tlng=en