Nuclear pasta structures at high temperatures

Xia, C.-J.*; 丸山 敏毅  ; 安武 伸俊*; 巽 敏隆*

Xia, C.-J.*; Maruyama, Toshiki; Yasutake, Nobutoshi*; Tatsumi, Toshitaka*

We study nuclear pasta structures at high temperatures within a relativistic mean field model and Thomas-Fermi approximation. Typical structures (droplet, rod, slab, tube, and bubble) are obtained, which form various crystalline configurations. The properties of those nuclear pastas are examined in a three-dimensional geometry with reflection symmetry, where the optimum lattice constants are fixed minimizing the free energy under spherical or cylindrical approximations for Wigner-Seitz cells. For fixed densities and temperatures, the differences of the free energies per baryon for various shapes and lattice structures are typically on the order of tens of keV, suggesting the coexistence of those structures. If we further increase temperature, eventually the non-uniform structures of nuclear pasta become unstable and are converted into uniform nuclear matter. The phase diagrams of nuclear matter are estimated, which is useful for understanding the various phenomena in neutron stars.