Ferromagnetism in nuclear matter(and how it relates to neutron stars)

Jacobus Diener (PhD student)Supervisors:

Prof FG Scholtz and Prof HB Geyer

Department of PhysicsStellenbosch University

Neutron stars/Pulsars• Remnant core of massive star that explode

in a core-collapse supernovaOne of the most dense states of matter

Crab NebulaHST image from http://chandra.harvard.edu/

Neutron stars/Pulsars• Commonly

observed as pulsarsRapidly rotating

neutron star with radio-emissions at magnetic poles

Glitches: Sudden spin-up in rotation frequency

Magnetars: Pulsars with super-strong magnetic field

www.astrocu.unam.mx/neutrones/dany.html

Glitches• Sudden spin-ups in period of pulsar

Crust and interior are differentially rotating Neutron superfluidSpin-ups relating to decoupling of vortices at

crustal boundary

• “A” parameter from observational data, available from HartRAO

• Ires dependent on equation of state of interior

Ares

crust

I

I

Link et al, PRL 83 (17) 1999

Magnetars

• Pulsars with super-strong magnetic fields (SGR, AXP)~1015 Gauss magnetic field (normally 1012

Gauss)Dynamo actionFerromagnetic phase

• Ferromagnetism: Alignment of intrinsic spins of particles in pulsar interiorRelativistic description of ferromagnetism

Ferromagnetism

• Spontaneous alignment of spin to minimize the energy of the systemTransition density

• Need to know matter present as well as equation of state of interior of pulsar (magnetar)

http://www.tf.uni-kiel.de/matwis/

F. Weber, Prog. Part. Nucl. Phys. 54 (2005)

Model for pulsar matter• Relativistic, effective field theory

Meson mediate interaction between nucleons

Describe ferromagnetism in this settingEquation of state

• General Relativity to model rapidly rotating ultra-dense fluid

• Observational dataHartRAO

Constraining equation of state

Conclusion• Pulsars are extra-terrestrial laboratories

for nuclear physicistsTest descriptions of nuclear matter

• Provides theoretical interpretation for pulsar observations

• Need for observers and theorist to work together

Word of thanks

• SA SKA project and Stellenbosch University for supporting this research

• Kim and Annah who deals with all the bursary admin