Detecting superfluid transition in the pulsar core
Partha Bagchi (School of Physical Sciences, National Institute of Science Education and Research, Bhubaneswar, India), Biswanath Layek (Department of Physics, Birla Institute of Technology and Science, Pilani-333031, India), Dheeraj Saini (Physics Department, The LNM Institute of Information Technology, Jaipur-302031, India), Anjishnu Sarkar (Physics Department, The LNM Institute of Information Technology, Jaipur-302031, India), Ajit M. Srivastava (Institute of Physics, Sachivalaya Marg, Bhubaneswar-751005, India), Deepthi Godaba Venkata (Department of Physics, Birla Institute of Technology and Science, Pilani-333031, India)
arXiv:2403.11539v1 Announce Type: new
Abstract: It is believed that the core of a neutron star can be host to various novel phases of matter, from nucleon superfluid phase to exotic high baryon density QCD phases. Different observational signals for such phase transitions have been discussed in the literature. Here, we point out a unique phenomenon associated with phase transition to a superfluid phase, which may be the nucleon superfluid phase or a phase like the CFL phase, allowing for superfluid vortices. In any superfluid phase transition, a random network of vortices forms via the so-called Kibble-Zurek mechanism, which eventually mostly decays away, finally leaving primarily vortices arising from the initial angular momentum of the core. This transient, random vortex network can have a non-zero net angular momentum for the superfluid component, which will generally be oriented in an arbitrary direction. This is in contrast to the final vortices, which arise from initial rotation and hence have the initial angular momentum of the neutron star. The angular momentum of the random vortex network is balanced by an equal and opposite angular momentum in the normal fluid due to the conservation of angular momentum, thereby imparting an arbitrarily oriented angular momentum component to the outer shell of the neutron star. This will affect the pulse timing and pulse profile of a pulsar. These changes in the pulses will decay away in a characteristic manner as the random vortex network decays, obeying specific scaling laws leading to universal features for the detection of superfluid transitions occurring in a pulsar core.arXiv:2403.11539v1 Announce Type: new
Abstract: It is believed that the core of a neutron star can be host to various novel phases of matter, from nucleon superfluid phase to exotic high baryon density QCD phases. Different observational signals for such phase transitions have been discussed in the literature. Here, we point out a unique phenomenon associated with phase transition to a superfluid phase, which may be the nucleon superfluid phase or a phase like the CFL phase, allowing for superfluid vortices. In any superfluid phase transition, a random network of vortices forms via the so-called Kibble-Zurek mechanism, which eventually mostly decays away, finally leaving primarily vortices arising from the initial angular momentum of the core. This transient, random vortex network can have a non-zero net angular momentum for the superfluid component, which will generally be oriented in an arbitrary direction. This is in contrast to the final vortices, which arise from initial rotation and hence have the initial angular momentum of the neutron star. The angular momentum of the random vortex network is balanced by an equal and opposite angular momentum in the normal fluid due to the conservation of angular momentum, thereby imparting an arbitrarily oriented angular momentum component to the outer shell of the neutron star. This will affect the pulse timing and pulse profile of a pulsar. These changes in the pulses will decay away in a characteristic manner as the random vortex network decays, obeying specific scaling laws leading to universal features for the detection of superfluid transitions occurring in a pulsar core.