1,828 research outputs found
Comment on ``Theorem for nonrotating singularity-free universes''
We show that Raychaudhuri's recently proposed theorem on nonrotating
universes cannot be used to rule out realistic singularity-free descriptions of
the universe, as suggested by him in PRL 80, 654 (1998).Comment: 1 page, to appear in Phys.Rev.Let
Pseudoclassical Model of Spinning Particle with Anomalous Magnetic Momentum
A generalization of the pseudoclassical action of a spinning particle in the
presence of an anomalous magnetic momentum is given. The action is written in
reparametrization and supergauge invariant form. The Dirac quantization, based
on the Hamiltonian analyses of the model, leads to the Dirac-Pauli equation for
a particle with an anomalous magnetic momentum in an external electromagnetic
field. Due to the structure of first-class constraints in that case, the Dirac
quantization demands for consistency to take into account an operators ordering
problem.Comment: 9 pages, IFUSP/P-100
Homogeneous cosmologies and the Maupertuis-Jacobi principle
A recent work showing that homogeneous and isotropic cosmologies involving
scalar fields are equivalent to the geodesics of certain effective manifolds is
generalized to the non-minimally coupled and anisotropic cases. As the
Maupertuis-Jacobi principle in classical mechanics, such result permits us to
infer some dynamical properties of cosmological models from the geometry of the
associated effective manifolds, allowing us to go a step further in the study
of cosmological dynamics. By means of some explicit examples, we show how the
geometrical analysis can simplify considerably the dynamical analysis of
cosmological models.Comment: 5 page
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