Non-standard interaction effects on astrophysical neutrino fluxes

We investigate new physics effects in the production and detection of high energy neutrinos at neutrino telescopes. Analysing the flavor ratios \phi_\mu/\phi_\tau and \phi_\mu/(\phi_\tau+\phi_e), we find that the Standard Model predictions for them can be sensibly altered by new physics effects.Comment: 21 pages, 9 figures, REVTeX

Pulse retrieval and soliton formation in a non-standard scheme for dynamic electromagnetically induced transparency

We examine in detail an alternative method of retrieving the information written into an atomic ensemble of three-level atoms using electromagnetically induced transparency. We find that the behavior of the retrieved pulse is strongly influenced by the relative collective atom-light coupling strengths of the two relevant transitions. When the collective atom-light coupling strength for the retrieval beam is the stronger of the two transitions, regeneration of the stored pulse is possible. Otherwise, we show the retrieval process can lead to creation of soliton-like pulses.Comment: 11 figure

Searching for binary central stars of planetary nebulae with Kepler

The Kepler Observatory offers unprecedented photometric precision (<1 mmag) and cadence for monitoring the central stars of planetary nebulae, allowing the detection of tiny periodic light curve variations, a possible signature of binarity. With this precision free from the observational gaps dictated by weather and lunar cycles, we are able to detect companions at much larger separations and with much smaller radii than ever before. We have been awarded observing time to obtain light-curves of the central stars of the six confirmed and possible planetary nebulae in the Kepler field, including the newly discovered object Kn 61, at cadences of both 30 min and 1 min. Of these six objects, we could confirm for three a periodic variability consistent with binarity. Two others are variables, but the initial data set presents only weak periodicities. For the central star of Kn 61, Kepler data will be available in the near future

Dynamics of spin 1/2 quantum plasmas

The fully nonlinear governing equations for spin 1/2 quantum plasmas are presented. Starting from the Pauli equation, the relevant plasma equations are derived, and it is shown that nontrivial quantum spin couplings arise, enabling studies of the combined collective and spin dynamics. The linear response of the quantum plasma in an electron--ion system is obtained and analyzed. Applications of the theory to solid state and astrophysical systems as well as dusty plasmas are pointed out.Comment: 4 pages, 2 figures, to appear in Physical Review Letter

Graviton mediated photon-photon scattering in general relativity

In this paper we consider photon-photon scattering due to self-induced gravitational perturbations on a Minkowski background. We focus on four-wave interaction between plane waves with weakly space and time dependent amplitudes, since interaction involving a fewer number of waves is excluded by energy-momentum conservation. The Einstein-Maxwell system is solved perturbatively to third order in the field amplitudes and the coupling coefficients are found for arbitrary polarizations in the center of mass system. Comparisons with calculations based on quantum field theoretical methods are made, and the small discrepances are explained.Comment: 5 pages, 3 figure

A possibility to measure elastic photon--photon scattering in vacuum

Photon--photon scattering in vacuum due to the interaction with virtual electron-positron pairs is a consequence of quantum electrodynamics. A way for detecting this phenomenon has been devised based on interacting modes generated in microwave waveguides or cavities [G. Brodin, M. Marklund and L. Stenflo, Phys. Rev. Lett. \textbf{87} 171801 (2001)]. Here we materialize these ideas, suggest a concrete cavity geometry, make quantitative estimates and propose experimental details. It is found that detection of photon-photon scattering can be within the reach of present day technology.Comment: 7 pages, 3 figure

Invertible Dirac operators and handle attachments on manifolds with boundary

For spin manifolds with boundary we consider Riemannian metrics which are product near the boundary and are such that the corresponding Dirac operator is invertible when half-infinite cylinders are attached at the boundary. The main result of this paper is that these properties of a metric can be preserved when the metric is extended over a handle of codimension at least two attached at the boundary. Applications of this result include the construction of non-isotopic metrics with invertible Dirac operator, and a concordance existence and classification theorem.Comment: Accepted for publication in Journal of Topology and Analysi

Gravitational dynamics for all tensorial spacetimes carrying predictive, interpretable and quantizable matter

Only a severely restricted class of tensor fields can provide classical spacetime geometries, namely those that can carry matter field equations that are predictive, interpretable and quantizable. These three conditions on matter translate into three corresponding algebraic conditions on the underlying tensorial geometry, namely to be hyperbolic, time-orientable and energy-distinguishing. Lorentzian metrics, on which general relativity and the standard model of particle physics are built, present just the simplest tensorial spacetime geometry satisfying these conditions. The problem of finding gravitational dynamics---for the general tensorial spacetime geometries satisfying the above minimum requirements---is reformulated in this paper as a system of linear partial differential equations, in the sense that their solutions yield the actions governing the corresponding spacetime geometry. Thus the search for modified gravitational dynamics is reduced to a clear mathematical task.Comment: 47 pages, no figures, minor update

The `s-rule' exclusion principle and vacuum interpolation in worldvolume dynamics

We show how the worldvolume realization of the Hanany-Witten effect for a supersymmetric D5-brane in a D3 background also provides a classical realization of the `s-rule' exclusion principle. Despite the supersymmetry, the force on the D5-brane vanishes only in the D5 `ground state', which is shown to interpolate between 6-dimensional Minkowski space and an $OSp(4^*|4)$-invariant $adS_2\times S^4$ geometry. The M-theory analogue of these results is briefly discussed.Comment: 25 pages, 9 figures, LaTeX JHEP styl