Seminars & Colloquia Calendar

Abstract: The Euler-Poisson equations are a classical model in the theory of stellar structure. When a star has nonzero angular momentum, it will deform from a spherical shape and settle at a steady state called a rotating star solution. An extensive literature has established the existence of such solutions for given angular velocity profile, including the case of differential rotation, where different parts of the star rotate at different speeds. However, all of the existing results only allow the angular velocity to depend on the distance to the rotation axis, but not on the distance to the equatorial plane. In this talk, I will present the first result that allows a general rotation profile, without restrictions. This enables us to model the rotation of our own Sun. I will also explain a hidden connection between the restriction on the rotation profile and the constancy of entropy across the star. Consequently, the new result is the first one that allows a genuinely changing entropy within the star. This is joint work with Juhi Jang and Walter Strauss.