 One of their most important results is that the Mandelbrot set is connected.Hubbard graduated with a Doctorat d'État from Université de Paris-Sud in 1973 under the direction of Adrien Douady; his thesis was entitled "Sur Les Sections Analytiques de La Courbe Universelle de Teichmüller" and was published by the American Mathematical Society.Hubbard has a variety of mathematical interests ranging from complex analysis to differential geometry.