Astromaterial Science and Nuclear Pasta

Prof. Charles Horowitz (host Alford/Dickhoff), Department of Physics, Indiana University, Bloomington
September 14, 2017 at 3:00 pm
241 Compton
Event Description 

We define Astromaterial Science as the study of materials, in astronomical objects, that are qualitatively denser than materials on earth. Astromaterials can have unique properties, related to their density, such as extraordinary mechanical strength, or alternatively be organized in ways similar to more conventional materials. Coulomb crystals form in the interior of cold white dwarfs and make up the crust of neutron stars. Large-scale molecular dynamics simulations suggest that neutron star crust is the strongest material known, some ten billion times stronger than steel. It can support centimeter high mountains that, on rapidly rotating neutron stars, may radiate detectable gravitational waves. Nuclear pasta is an example of a soft astromaterial. It is expected near the base of the neutron star crust at densities of ten to the fourteen grams per cubic centimeter. Competition between nuclear attraction and Coulomb repulsion rearrange the neutrons and protons into com plex shapes such as flat sheets (lasagna) or thin tubes (spaghetti). Biological membranes are observed with similar shapes. We illustrate some of the shapes that form in large scale molecular dynamics simulations, and discuss their transport properties including shear viscosity, thermal conductivity, electrical conductivity, and neutrino opacity. We present observations of magnetic field decay and crust cooling of neutron stars that may be sensitive to the presence of spiral defects in nuclear pasta.

[Talk based on arXiv:1606.03646, Rev. Mod. Phys. in press.]

Coffee: 2:30 pm, 241 Compton