Nuclear astrophysics is a field at the intersection of nuclear physics and astrophysics, which seeks to understand the nuclear engines of astronomical objects and the origin of the chemical elements. This white paper summarizes progress and status of the field, the new open questions that have emerged, and the tremendous scientific opportunities that have opened up with major advances in capabilities across an ever growing number of disciplines and subfields that need to be integrated. We take a holistic view of the field discussing the unique challenges and opportunities in nuclear astrophysics in regards to science, diversity, education, and the interdisciplinarity and breadth of the field. Clearly nuclear astrophysics is a dynamic field with a bright future that is entering a new era of discovery opportunities.

In this paper, we intend to establish a rigorous mathematical relation between the Gibbons–Hawking–York (GHY) boundary term and the conserved symmetric current which arises due to Noether’s second theorem. The GHY term is necessary to ensure that the equations of motion in general relativity are well-posed, and it is a key ingredient in the thermodynamics of black holes and the derivation of the Bekenstein–Hawking entropy. Noether’s second theorem on the other hand relates the symmetries of the action to conserved quantities of the system. In this paper, we prove that the connection between the GHY term and Noether’s second theorem can be established by considering a diffeomorphism that preserves the boundary condition of the surface integral. Additionally, we also derive the associated conserved current and charge.

No abstract

No abstract

In this paper, we investigate some basic properties of proto-neutron star (NS) stability and its formation based on the Raychaudhuri equation and consequence of geodesic congruence of rotating space-time structure surrounding an ideal isotropic fluid under the consideration of gravitational collapse. We also consider the formation of a newly born NS under the effect of Raychaudhuri equation coupled with the Tolman-Oppenheimer-Volkoff (TOV) equation in a dragged frame for comoving coordinates. The stability criteria of a newly born NS is also explored under such conditions. In the view of our proposal, we eventually deduce that along with TOV equation, Raychaudhuri equation may provide a structural stability of surrounding space-time from further collapse to singularity for a newly born NS.