407 research outputs found
The Nuclear Physics of Neutron Stars
We explore the unique and fascinating structure of neutron stars. Although
neutron stars are of interest in many areas of Physics, our aim is to provide
an intellectual bridge between Nuclear Physics and Astrophysics. We argue
against the naive perception of a neutron star as a uniform assembly of
neutrons packed to enormous densities. Rather, by focusing on the many exotic
phases that are speculated to exist in a neutron star, we show how the reality
is different and far more interesting.Comment: 8 pages and 4 figures. Excerpts from a lecture presented at the
Seventh European Summer School on Experimental Nuclear Astrophysics; Catania,
IT (September, 2013
Symmetry Energy Constraints from Giant Resonances: A Theoretical Overview
Giant resonances encapsulate the dynamic response of the nuclear ground state
to external perturbations. As such, they offer a unique view of the nucleus
that is often not accessible otherwise. Although interesting in their own
right, giant resonances are also enormously valuable in providing stringent
constraints on the equation of state of asymmetric matter. We this view in
mind, we focus on two modes of excitation that are essential in reaching this
goal: the isoscalar giant monopole resonance (GMR) and the isovector giant
dipole resonance (GDR). GMR energies in heavy nuclei are sensitive to the
symmetry energy because they probe the incompressibility of neutron-rich
matter. Unfortunately, access to the symmetry energy is hindered by the
relatively low neutron-proton asymmetry of stable nuclei. Thus, the measurement
of GMR energies in exotic nuclei is strongly encouraged. In the case of the
GDR, we find the electric dipole polarizability of paramount importance.
Indeed, the electric dipole polarizability appears as one of two laboratory
observables -- with the neutron-skin thickness being the other -- that are
highly sensitive to the density dependence of the symmetry energy. Finally, we
identify the softness of skin and the nature of the pygmy resonance as
important unsolved problems in nuclear structure.Comment: 18 pages, 12 figures, submitted to EPJA "Special Issue on Symmetry
Energy
Relativistic density functional theory for finite nuclei and neutron stars
The main goal of the present contribution is a pedagogical introduction to
the fascinating world of neutron stars by relying on relativistic density
functional theory. Density functional theory provides a powerful--and perhaps
unique--framework for the calculation of both the properties of finite nuclei
and neutron stars. Given the enormous densities that may be reached in the core
of neutron stars, it is essential that such theoretical framework incorporates
from the outset the basic principles of Lorentz covariance and special
relativity. After a brief historical perspective, we present the necessary
details required to compute the equation of state of dense, neutron-rich
matter. As the equation of state is all that is needed to compute the structure
of neutron stars, we discuss how nuclear physics--particularly certain kind of
laboratory experiments--can provide significant constrains on the behavior of
neutron-rich matter.Comment: Contributing chapter to the book "Relativistic Density Functional for
Nuclear Structure"; World Scientific Publishing Company (Singapore); Editor
Prof. Jie Meng (Peking University
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