H/F doctoral student in theoretical physics

The thesis project will be carried out at the « Laboratoire de Physique des 2 infinis Irène Joliot-Curie » (IJCLab), which is a mixed research unit (UMR) of the CNRS (IN2P3), the Université Paris-Saclay, and the Université de Paris, located 20 km south of Paris on the campus of Orsay and easily accessible by public transport (RER) within 35 minutes from the center of Paris. IJCLab was created in 2020 from the merger of five laboratories (CSNSM, IMNC, IPN, LAL, and LPT). It has about 220 permanent and 200 non-permanent scientists, including 120 doctoral students, and 340 engineers, technicians and administrative staff. The research fields of the laboratory are nuclear physics, high energy physics, theoretical physics, astroparticles, astrophysics and cosmology, particle accelerators, energy and environment, and health physics.
The PhD student will work in the theoretical nuclear physics group (about 17 people) which is part of the theory department (about 55 people) of the laboratory. The theory department covers a large spectrum of topics: mathematical physics, cosmology, physics beyond the standard model, flavor physics, QCD, nuclear physics, and statistical physics. In the field of nuclear astrophysics, we maintain close links with the experimentalists and observers of the nuclear-physics department and the astroparticle, astrophysics, and cosmology department. We have also collaborations with other nearby laboratories, such as CEA Saclay and Observatoire de Paris-Meudon.
The student will be enrolled in Université Paris-Saclay (doctoral school PHENIICS).

Neutron stars are very dense astrophysical objects produced in core-collapse supernova explosions. A huge progress has been made recently and will be made within the next decades in the observation of these objects with new radiotelescopes or in visible, X-ray, or gamma. From the nuclear-physics point of view, they can be considered natural laboratories for the study of nuclear matter under extreme conditions of asymmetry (many more neutrons than protons) and density. Among the fascinating properties of these stars is their superfluidity, caused by Cooper pairing of neutrons. It can be observed via the glitch phenomenon, i.e., the abrupt change of the rotation frequency of pulsars.
For the understanding of the observed glitches, the density of superfluid neutrons in the inner crust of neutron stars plays a key role. In that region, superfluid neutrons coexist with a solid crystal lattice of nuclei. Hence, the physics of the solid crust is particularly rich and combines elements of nuclear physics, astrophysics, and solid-state physics. Previous calculations of the density of superfluid neutrons have used the superfluid hydrodynamics approach or band-structure theory (analogous to the one used for electrons in solid-state physics).
In contrast to the hydrodynamical calculations, the band-structure calculations predict a clearly insufficient superfluid fraction to explain the glitch observations. The aim of this thesis is to reconcile these two theoretical approaches and to give a reliable result for the superfluid fraction, by including the effects of neutron pairing and the change of the order parameter due to the superfluid flow in a consistent way into the band structure calculations. This includes formal developments and their numerical implementation.
More details and references for further reading can be found here: https://www.adum.fr/as/ed/voirproposition.pl?site=PSaclay&matricule_prop...