Speaker
Description
Scalars sporting a coupling to nucleons with masses $m_\phi$<1 MeV might be copiously produced in cold isolated neutron stars (NSs). Despite NSs can be only used as probes complementary to the classic supernova (SN) 1987A cooling bound in the case of axions, I will discuss how the shallow temperature dependence of the scalar emissivity leads to a huge enhancement in the effect of scalars on the cooling process of NSs. The absence of any evidence of exotic energy losses allowed us to introduce the most stringent constraint on the scalar-nucleon coupling, superseding all existing limits across six orders of magnitude in the scalar mass. These arguments also lead to the most stringent bounds on the strength of fifth forces acting on micro- to picometer length scales.