Parity nonconservation and stellar collapse
ACCORDING to the current theory, the evolution of sufficiently massive stars leads eventually to gravitational instability and collapse. After thermonuclear burning has stopped, dense stellar cores become unstable and collapse to form neutron stars (pulsars) or black holes. In both cases energy of the order of 0.1 Mc2 is released, mostly in the form of neutrinos and gravitational waves. As the radius of the core decreases, its magnetic field grows (magnetic flux is conserved) and can reach huge values of order 1012–1013 G. Even greater azimuthal fields (∼3 × 1015 G) can be generated by differential rotation of the core1. It will be shown here that neutrino emission in the collapse is asymmetric, as a result of parity nonconservation in weak interactions. Neutrinos and antineutrinos are emitted preferentially in the direction parallel to the local magnetic field of the collapsing core.
Cosmology, astrophysics and elementary particle physics
The Universe provides a laboratory in which it is possible to test the laws of physics in conditions which cannot be achieved in a terrestrial laboratory. The author assumes that the laws of physics are unchanging in space and time and discusses how modern developments in elementary particle physics influence our understanding of the Universe and conversely the possibility that astronomical observations may give information about elementary particle physics. In particular he studies the physics of the early Universe and discusses the role of new particles such as heavy leptons, neutrinos and quarks and the possible relationship of the net baryon number of the Universe to unified models of elementary particle physics. He considers the role of neutrinos in stellar evolution, particularly in the explosion of supernovae and in the cooling of neutron stars. Black holes are also discussed.
The gravitational collapse of iron-oxygen stars with masses of 2M⊙ and 10M⊙ II
The collapse of iron-oxygen stars with masses of 2M⊙ has been calculated. The commencement of the collapse is due to dissociation of iron-group nuclei into free nucleons. After a while, the collapse proceeds in consequence of intensive energy losses due to neutrino volume radiation. At an intermediate stage of the collapse, the core — opaque with respect to neutrino radiation (neutrino core) — is formed inside the collapsing star. Both the gradual increase of the mass of the neutrino core and the partial absorption of neutrinos radiated from the surface of the neutrino core by the stellar envelope (deposition) were taken into account in our calculations. The kinetics of oxygen burning in the outer layers of the envelope was also allowed for. Neither the deposition, nor the oxygen burning, result in ejection of stellar envelopes.