Description
Neutron stars are rich laboratories for physics, combining all four fundamental interactions and
many phenomena associated with them under extreme conditions. One of the most intriguing
questions is: what do we find in the core of such a compact object?
There has been a wide consensus in nearly all theoretical approaches for neutron star matter
that hyperons may appear in the inner core of neutron stars at densities of about twice the nuclear
saturation density. However, introducing hyperons as an additional species, the equationof-
state is softened. This usually results in a significant reduction of the maximum mass. The
recent observations of massive neutron stars with about twice the solar mass and the expected
appearance of hyperons at about two times nuclear density remains an unresolved mystery in
neutron star physics, the so-called “hyperon puzzle”.
Hadrons with strangeness embedded in the nuclear environment, hypernuclei or strange atoms,
are the only available tool to approach the many-body aspect of the three-flavor strong interaction.
These studies need to be accompanied by elementary scattering experiments and
interferometric studies as well as modern theoretical developements. In parallel, strangeness
physics and hypernuclear theory are demanded to develop scenarios to overcome the still persisting
uncertainties on mixed systems of strange and ordinary matter.