Exploring Fundamental Physics with Neutron Stars
EXPLORING FUNDAMENTAL PHYSICS WITH NEUTRON STARS PIERRE M. PIZZOCHERO Dipartimento di Fisica, Università degli Studi di Milano, and Istituto Nazionale di Fisica Nucleare, sezione di Milano, Via Celoria 16, 20133 Milano, Italy ABSTRACT In this lecture, we give a First introduction to neutron stars, based on Fundamental physical principles. AFter outlining their outstanding macroscopic properties, as obtained From observations, we inFer the extreme conditions oF matter in their interiors. We then describe two crucial physical phenomena which characterize compact stars, namely the gravitational stability of strongly degenerate matter and the neutronization of nuclear matter with increasing density, and explain how the Formation and properties of neutron stars are a direct consequence oF the extreme compression of matter under strong gravity. Finally, we describe how multi-wavelength observations of diFFerent external macroscopic Features (e.g. maximum mass, surface temperature, pulsar glitches) can give invaluable inFormation about the exotic internal microscopic scenario: super-dense, isospin-asymmetric, superFluid, bulk hadronic matter (probably deconFined in the most central regions) which can be Found nowhere else in the Universe. Indeed, neutrons stars represent a unique probe to study the properties of the low-temperature, high-density sector of the QCD phase diagram. Moreover, binary systems of compact stars allow to make extremely precise measurements of the properties of curved space-time in the strong Field regime, as well as being efFicient sources oF gravitational waves. I – INTRODUCTION Neutron stars are probably the most exotic objects in the Universe: indeed, they present extreme and quite unique properties both in their macrophysics, controlled by the long-range gravitational and electromagnetic interactions, and in their microphysics, controlled by the short-range weak and strong nuclear interactions.
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