Title: Higher bifurcation currents, neutral cycles and the Mandelbrot set

Authors: Thomas Gauthier

Issue: Volume 63 (2014), Issue 4, 917-937


We prove that, given any $\theta_1,\ldots,\theta_{2d-2}in \R\setminus\Z$, the support of the bifurcation measure of the moduli space of degree $d$ rational maps coincides with the closure of classes of maps having $2d-2$ neutral cycles of respective multipliers $e^{2i\pi\theta_1},\ldots,e^{2i\pi\theta_{2d-2}}$. To this end, we generalize a famous result of McMullen, proving that homeo\-morphic copies of $(\partial \Mand)^{k}$ are dense in the support of the $k^{\mbox{\tiny th}}$-bifurcation current $T^k_{\mbox{\tiny bif}}$ in general families of rational maps, where $\Mand$ is the Mandelbrot set. As a consequence, we also get sharp dimension estimates for the supports of the bifurcation currents in any family.