Physics

Abstract: The inspiral of compact objects like black holes or neutron stars can be approximated using point masses very well. However, very interesting astronomical information is contained in effects to gravitational waves arising from the object's higher multipoles (or their finite size). Some of these effects can be modeled by an extension of the point mass action. Based on such an action, contributions of dipole (i.e., spin) and quadrupole to the post-Newtonian (PN) approximation can be obtained. The quadrupole effects are the first which encode information of the internal structure of the compact objects, e.g., they allow an distinction between black holes and neutron stars and also different equations of state.

Abstract: An extension of the canonical formalism of Arnowitt, Deser, and Misner from point-masses to spinning objects is presented. The derivation of this extension is based on an action functional and is similar to the original derivation of Arnowitt, Deser, and Misner for non-spinning objects. This action approach currently covers the pole-dipole approximation of self-gravitating extended bodies to linear order in spin. As an application, spin contributions to the conservative next-to-leading order in the post-Newtonian approximation scheme are presented. Also higher orders and radiation reaction effects in the Hamiltonian due to spin are discussed.

Abstract: The extension of the canonical formalism of Arnowitt, Deser and Misner from point-masses to spinning objects is a long standing problem in General Relativity. Two independent approaches to a solution of this problem are given in this talk. The first is based on an explicit order-by-order construction of the canonical formalism within the post-Newtonian approximation scheme. Here the global Poincare algebra is the important consistency condition. The second approach is based on an action functional and is similar to the original derivation of Arnowitt, Deser and Misner for non-spinning objects. A comparison to the canonical formulation of the Dirac field coupled to gravity is made. As an application, spin and quadrupole contributions to next-to-leading order in the post-Newtonian approximation scheme are presented.