Global topological k-defects

We consider global topological defects in symmetry breaking models with a non-canonical kinetic term. Apart from a mass parameter entering the potential, one additional dimensional parameter arises in such models -- a ``kinetic'' mass. The properties of defects in these models are quite different from ``standard'' global domain walls, vortices and monopoles, if their kinetic mass scale is smaller than their symmetry breaking scale. In particular, depending on the concrete form of the kinetic term, the typical size of such a defect can be either much larger or much smaller than the size of a standard defect with the same potential term. The characteristic mass of a non-standard defect, which might have been formed during a phase transition in the early universe, depends on both the temperature of a phase transition and the kinetic mass.Comment: 7 pages, 3 figures; v2: references added, matches the published versio

Ultra-hard fluid and scalar field in the Kerr-Newman metric

An analytic solution for the accretion of ultra-hard perfect fluid onto a moving Kerr-Newman black hole is found. This solution is a generalization of the previously known solution by Petrich, Shapiro and Teukolsky for a Kerr black hole. Our solution is not applicable for an extreme black hole due to violation of the test fluid approximation. We also present a stationary solution for a massless scalar field in the metric of a Kerr-Newman naked singularity.Comment: 9 pages, 3 figures, revtex4; v2: presentation improved, figures added, matches published versio

Stationary Configurations Imply Shift Symmetry: No Bondi Accretion for Quintessence / k-Essence

In this paper we show that, for general scalar fields, stationary configurations are possible for shift symmetric theories only. This symmetry with respect to constant translations in field space should either be manifest in the original field variables or reveal itself after an appropriate field redefinition. In particular this result implies that neither k-Essence nor Quintessence can have exact steady state / Bondi accretion onto Black Holes. We also discuss the role of field redefinitions in k-Essence theories. Here we study the transformation properties of observables and other variables in k-Essence and emphasize which of them are covariant under field redefinitions. Finally we find that stationary field configurations are necessarily linear in Killing time, provided that shift symmetry is realized in terms of these field variables.Comment: 8 page

Gravitational radiation from rotating monopole-string systems

We study the gravitational radiation from a rotating monopole-antimonopole pair connected by a string. While at not too high frequencies the emitted gravitational spectrum is described asymptotically by $P_n\propto n^{-1}$, the spectrum is exponentially suppressed in the high-frequency limit, $P_n\propto \exp(-n/n_{\rm cr})$. Below $n_{\rm cr}$, the emitted spectrum of gravitational waves is very similar to the case of an oscillating monopole pair connected by a string, and we argue therefore that the spectrum found holds approximately for any moving monopole-string system. As application, we discuss the stochastic gravitational wave background generated by monopole-antimonopole pairs connected by strings in the early Universe and gravitational wave bursts emitted at present by monopole-string networks. We confirm that advanced gravitational wave detectors have the potential to detect a signal for string tensions as small as $G\mu\sim 10^{-13}$.Comment: 8 pages, 2 figures, revtex4; v2: minor corrections, matches published versio