SPIN COMPACT OBJECTS · Fundamental Physics with the Spin of Compact Objects

Modern physics presents a number of challenges about the behaviour of the four fundamental forces of Nature which are beyond current technological capabilities of Earth-based labs. The existence of gravitational waves, their emission processes and the determination of the true ground state of ultra-dense matter are fascinating problems that can only be addressed with exceptional astrophysical laboratories like compact objects. In particular neutron stars and black holes, provide a unique opportunity to advance our understanding of these fundamental physics problems. The spin of neutron stars is perhaps the best observable that carries a large amount of information on the behaviour of matter in curved space-times and at ultra-high densities. Indeed the efficiency of gravitational wave emission mechanisms and the binding energy of sub-nuclear particles do depend on the spin period of neutron stars. In this project I address the problem of the existence of neutron stars in X-ray binaries with spin periods of less than 1 millisecond and propose to perform the deepest pulse search ever done on neutron star low mass X-ray binaries. These sub-millisecond objects, if found, are spinning sufficiently fast that strong model-independent constraints can be placed on the equation of state of ultra-dense matter and on the efficiency of gravitational wave emission mechanisms. I discuss then a possible new way to determine the spin of compact objects through a yet poorly explored quantum property of light. Finally, I propose to constrain gravitational wave emission mechanisms based on an enlarged sample size of neutron star spin frequencies which might help to pinpoint the best neutron star candidates for future direct gravitational wave searches.