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SUMMARY:Giorgio Almirante "Fraction superfluide dans la croûte interne de
 s étoiles à neutrons"
DTSTART:20251014T120000Z
DTEND:20251014T140000Z
DTSTAMP:20260819T110200Z
UID:indico-event-12283@indico.ijclab.in2p3.fr
DESCRIPTION:Fraction superfluide dans la croûte interne des étoiles à n
 eutrons / Superfluid fraction in the inner crust of neutron stars\nAbstrac
 t :\nNeutron stars are fascinating astrophysical objects\, containing matt
 er at densities that exceeds the density of atomic nuclei. Among the most 
 puzzling phenomena associated with them are pulsar glitches. Pulsars are r
 apidly rotating neutron stars\, emitting beams of radiation from their mag
 netic poles and acting as the most precise clocks in the Universe\, even s
 urpassing the accuracy of atomic clocks on Earth. Occasionally\, however\,
  they exhibit sudden increases in their rotational frequency\, events know
 n as glitches. These unexpected spin-ups are thought to arise from complex
  interactions between different internal components of the star. Several t
 heoretical models have been proposed to explain glitches\, most of them re
 lying on superfluidity in parts of the star. Superfluidity\, the possibili
 ty of a fluid to flow without viscosity at very low temperature\, has been
  studied on Earth in liquid helium and ultracold atoms. It is believed tha
 t also matter under extreme conditions inside neutron stars exhibits this 
 fascinating phenomenon. Despite decades of effort\, many uncertainties rem
 ain\, particularly concerning the deepest layers of the neutron star core.
  In the outer core\, it is expected that extremely neutron-rich nuclear ma
 tter coexists with electrons and\, at higher densities\, muons. The crust 
 is thought to be a lattice of nuclear clusters immersed in an electron gas
 . The transition from the outer to the inner crust is where neutrons begin
  to "drip" from nuclei\, eventually leading to a superfluid neutron gas be
 tween the nuclear clusters. The exotic phases within the inner crust are c
 entral to the star thermal and hydrodynamic behavior. This Thesis focuses 
 on a quantum mechanical description of the inner crust. Modeling this requ
 ires solving the nuclear many-body problem using realistic interactions an
 d accounting for the crystal structure and periodicity\, as well as the pr
 esence of superfluid neutron matter. A central aspect of this work is dete
 rmining the superfluid density\, which is a quantity directly related to t
 he effective mass of nuclear clusters moving through the neutron gas. This
  parameter influences the thermodynamics and hydrodynamics of neutron star
 s and has observable consequences\, such as in the thermal evolution and p
 ulsar glitches. In this Thesis\, Hartree-Fock-Bogoliubov calculations with
  Bloch boundary conditions are used to model the inner crust. In order to 
 get the most reliable results\, modern energy density functionals are impl
 emented\, together with a realistic pairing interaction. For the extractio
 n of the superfluid density\, a framework based on a Galilean transformati
 on is constructed\, allowing one to get this quantity within a time-indepe
 ndent calculation. Together with fully self-consistent numerical results\,
  this Thesis provides also a derivation of the expression for the superflu
 id density in the Bardeen-Cooper-Schrieffer approximation. This allows one
  to evaluate this quantity directly from the single-particle band structur
 e\, thus offering a benchmark for complete results and providing insight i
 nto the interplay between periodicity and superfluidity. The goal of this 
 Thesis is to clarify the role of superfluidity and provide a more precise 
 determination of the superfluid density\, contributing to our understandin
 g of glitch mechanisms and more generally the behavior of neutron star mat
 ter.\n \n \n\nhttps://indico.ijclab.in2p3.fr/event/12283/
LOCATION:100/0-MXX - Salle des Conseils (IJCLab)
URL:https://indico.ijclab.in2p3.fr/event/12283/
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