We argue that (0, 1) heterotic string models with 4 non-heterotic spacetime dimensions may provide an instability of the vacuum to gravitational polarization in globally strong gravitational fields. This instability would be triggered during gravitational collapse by a nonlocal quantum switching process, and lead to the formation of regions of a high temperature broken symmetry phase which woul...

Thermal duality is a relationship between the behaviour of heterotic string models of the E(8)xE(8) or SO(32) types at inversely related temperatures, a variant of T duality in the Euclidean regime. This duality would have consequences for the nature of the Hagedorn transition in these string models. We propose that the vacuum admits a family of deformations in situations where there are closed...

We review the status of the weak cosmic censorship conjecture, which asserts, in essence, that all singularities of gravitational collapse are hidden within black holes. Although little progress has been made toward a general proof (or disproof) of this conjecture, there has been some notable recent progress in the study of some examples and special cases related to the conjecture. These result...

As first discovered by Choptuik, the black hole threshold in the space of initial data for general relativity shows both surprising structure and surprising simplicity. Universality, power-law scaling of the black hole mass, and scale echoing have given rise to the term "critical phenomena". They are explained by the existence of exact solutions which are attractors within the black hole thresh...

The gravitational collapse of a magnetised medium is investigated by studying qualitatively the convergence of a timelike family of non-geodesic worldlines in the presence of a magnetic field. Focusing on the field’s tension we illustrate how the winding of the magnetic forcelines due to the fluid’s rotation assists the collapse, while shear-like distortions in the distribution of the field’s g...

We apply the principle of energy conservation to the motion of the test particle in gravitational field by requiring that its energy, gained by gravitation, has to be balanced by decrease of its rest mass. Due to the change of mass in gravitational field Newton's force law between gravitating bodies is modified, too. With this modified force law we build up the the classical field theory of gra...

We study the gravitational collapse of a self-gravitating charged scalar-field. Starting with a regular spacetime, we follow the evolution through the formation of an apparent horizon, a Cauchy horizon and a final central singularity. We find a null, weak, mass-inflation singularity along the Cauchy horizon, which is a precursor of a strong, spacelike singularity along the r = 0 hypersurface. T...

We model gravitational collapse leading to star formation in a wide range of isolated disk galaxies using a three-dimensional, smoothed particle hydrodynamics code. The model galaxies include a dark matter halo and a disk of stars and isothermal gas. Absorbing sink particles are used to directly measure the mass of gravitationally collapsing gas. They reach masses characteristic of stellar clus...

We study the gravitational radiation from gravitational collapses of rapidly rotating neutron stars induced by a phase-transition from normal nuclear matter to a mixed phase of quark and nuclear matter in the core of the stars. The study is based on self-consistent three dimensional hydrodynamic simulations with Newtonian gravity and a high resolution shock capturing scheme, and the quadrupole ...