Perturbations of a topological defect as a theory of scalar fields interacting with an external vector potential

This is a revised version of gr-qc/930403

No-horizon theorem for spacetimes with spacelike G1 isometry groups

We consider four-dimensional spacetimes $(M,{\mathbf g})$ which obey the Einstein equations ${\mathbf G}={\mathbf T}$, and admit a global spacelike $G_{1}={\mathbb R}$ isometry group. By means of dimensional reduction and local analyis on the reduced (2+1) spacetime, we obtain a sufficient condition on ${\mathbf T}$ which guarantees that $(M,{\mathbf g})$ cannot contain apparent horizons. Given any (3+1) spacetime with spacelike translational isometry, the no-horizon condition can be readily tested without the need for dimensional reduction. This provides thus a useful and encompassing apparent horizon test for $G_{1}$-symmetric spacetimes. We argue that this adds further evidence towards the validity of the hoop conjecture, and signals possible violations of strong cosmic censorship.Comment: 8 pages, LaTeX, uses IOP package; published in Class. Quantum Gra

Is Happiness a trait?

ABSTRACT One of the ideological foundations of the modern welfare states is the belief that people can be made happier by providing them with better living conditions. This belief is challenged by the theory that happiness is a fixed 'trait', rather than a variable 'state'. This theory figures both at the individual level and at the societal level. The individual level variant depicts happiness as an aspect of personal character; rooted in inborn temperament or acquired disposition. The societal variant sees happiness as a matter of national character; embedded in shared values and beliefs. Both variants imply that a better society makes no happier people. Happiness can be regarded as a trait if it meets three criteria: 1) temporal stability, 2) cross-situational consistency, and 3) inner causation. This paper checks whether that is, indeed, the case. The theory that happiness is a personal-character-trait is tested in a (meta) analysis of longitudinal studies. The results are: 1) Happiness is quite stable on the short term, but not in the long run, neither relatively nor absoloutely. 2) Happiness is not insensitive to fortune or adversity. 3) Happiness is not entirely built-in: its genetic basis is at best modest and psychological factors explain only part of its variance. The theory that happiness is a national-character-trait is tested in an analysis of differences in average happiness between nations. The results point in the same direction: 1) Though generally fairly stable over the last decades, nation-happiness has changed profoundly in some cases both absolutely and relatively. 2) Average happiness in nations is clearly not indep