Stretched Horizon for Non-Supersymmetric Black Holes

We review the idea of stretched horizon for extremal black holes in supersymmetric string theories, and we compute it for non-supersymmetric black holes in four dimensions. Only for small masses of the order of the Veneziano wavelength is the stretched horizon bigger than the event horizon.Comment: 4 pages, 2 figures, to appear in the Proceedings of the VIII Mexican School, Oaxaca, AI

The Capabilities of Monochromatic EC Neutrino Beams with the SPS Upgrade

The goal for future neutrino facilities is the determination of the U(e3) mixing and CP violation in neutrino oscillations. This will require precision experiments with a very intense neutrino source and energy control. With this objective in mind, the creation of monochromatic neutrino beams from the electron capture decay of boosted ions by the SPS of CERN has been proposed. We discuss the capabilities of such a facility as a function of the energy of the boost and the baseline for the detector. We conclude that the SPS upgrade to 1000 GeV is crucial to reach a better sensitivity to CP violation iff it is accompanied by a longer baseline. We compare the physics potential for two different configurations: I) $\gamma=90$ and $\gamma=195$ (maximum achievable at present SPS) to Frejus; II) $\gamma=195$ and $\gamma=440$ (maximum achievable at upgraded SPS) to Canfranc. The main conclusion is that, whereas the gain in the determination of U(e3) is rather modest, setup II provides much better sensitivity to CP violation.Comment: 4 pages, 5 figures, To appear in the proceedings of International Europhysics Conference on High Energy Physics (EPS-HEP2007), Manchester, England, 19-25 July 200

Phenolics, depsides and triterpenes from the chilean lichen pseudocyphellaria nudata (zahlbr.) D.J. Galloway

Indexación: ScieloThe lichen Pseudocyphellaria nudata is a species endemic to southern South América. From the lichen tallus, methyl orsellinate, 2-methoxy-3,6-dimethyl-4-hydroxybenzaldehyde, methyl-evernate, tenuiorin, hopan-6ß,22-diol and hopan-6α,76,22-triol were isolated and identified as the main lichen constituents. This is the first report of the occurrence of 2-methoxy-3,6-dimethyl-4-hydroxybenzaldehyde in lichens.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=s0717-97072008000300017&nrm=is

Pulsar spin-down: the glitch-dominated rotation of PSR J0537-6910

The young, fast-spinning, X-ray pulsar J0537-6910 displays an extreme glitch activity, with large spin-ups interrupting its decelerating rotation every ~100 days. We present nearly 13 years of timing data from this pulsar, obtained with the {\it Rossi X-ray Timing Explorer}. We discovered 22 new glitches and performed a consistent analysis of all 45 glitches detected in the complete data span. Our results corroborate the previously reported strong correlation between glitch spin-up size and the time to the next glitch, a relation that has not been observed so far in any other pulsar. The spin evolution is dominated by the glitches, which occur at a rate ~3.5 per year, and the post-glitch recoveries, which prevail the entire inter-glitch intervals. This distinctive behaviour provides invaluable insights into the physics of glitches. The observations can be explained with a multi-component model which accounts for the dynamics of the neutron superfluid present in the crust and core of neutron stars. We place limits on the moment of inertia of the component responsible for the spin-up and, ignoring differential rotation, the velocity difference it can sustain with the crust. Contrary to its rapid decrease between glitches, the spin-down rate increased over the 13 years, and we find the long-term braking index $n_{\rm l}=-1.22(4)$, the only negative braking index seen in a young pulsar. We briefly discuss the plausible interpretations of this result, which is in stark contrast to the predictions of standard models of pulsar spin-down.Comment: Minor changes to match the MNRAS accepted versio

Perspectives in Neutrino Physics: Monochromatic Neutrino Beams

In the last few years spectacular results have been achieved with the demonstration of non vanishing neutrino masses and flavour mixing. The ultimate goal is the understanding of the origin of these properties from new physics. In this road, the last unknown mixing $[U_{e3}]$ must be determined. If it is proved to be non-zero, the possibility is open for Charge Conjugation-Parity (CP) violation in the lepton sector. This will require precision experiments with a very intense neutrino source. Here a novel method to create a monochromatic neutrino beam, an old dream for neutrino physics, is proposed based on the recent discovery of nuclei that decay fast through electron capture. Such nuclei will generate a monochromatic directional neutrino beam when decaying at high energy in a storage ring with long straight sections. We also show that the capacity of such a facility to discover new physics is impressive, so that fine tuning of the boosted neutrino energy allows precision measurements of the oscillation parameters even for a $[U_{e3}]$ mixing as small as 1 degree. We can thus open a window to the discovery of CP violation in neutrino oscillations.Comment: 15 pages, 7 figures. Contribution to the proceedings of GUSTAVOFEST - Symposium in Honour of Gustavo C. Branco: CP Violation and the Flavour Puzzle, Lisbon, Portugal, 19-20 July 200

Physics Reach with a Monochromatic Neutrino Beam from Electron Capture

Neutrino oscillation experiments from different sources have demonstrated non-vanishing neutrino masses and flavour mixings. The next experiments have to address the determination of the connecting mixing U(e3) and the existence of the CP violating phase. Whereas U(e3) measures the strength of the oscillation probability in appearance experiments, the CP phase acts as a phase-shift in the interference pattern. Here we propose to separate these two parameters by energy dependence, using the novel idea of a monochromatic neutrino beam facility based on the acceleration of ions that decay fast through electron capture. Fine tuning of the boosted neutrino energy allows precision measurements able to open a window for the discovery of CP violation, even for a mixing as small as 1 degree.Comment: 4 pages, 1 figure. Talk given at the International Europhysics Conference on High Energy Physics, HEP-EPS 2005, Lisbon, Portugal, July 21-27, 200

The enigmatic spin evolution of PSR J0537-6910: r-modes, gravitational waves and the case for continued timing

We discuss the unique spin evolution of the young X-ray pulsar PSR J0537-6910, a system in which the regular spin down is interrupted by glitches every few months. Drawing on the complete timing data from the Rossi X-ray Timing Explorer (RXTE, from 1999-2011), we argue that a trend in the inter-glitch behaviour points to an effective braking index close to $n=7$, much larger than expected. This value is interesting because it would accord with the neutron star spinning down due to gravitational waves from an unstable r-mode. We discuss to what extent this, admittedly speculative, scenario may be consistent and if the associated gravitational-wave signal would be within reach of ground based detectors. Our estimates suggest that one may, indeed, be able to use future observations to test the idea. Further precision timing would help enhance the achievable sensitivity and we advocate a joint observing campaign between the Neutron Star Interior Composition ExploreR (NICER) and the LIGO-Virgo network.Comment: 10 pages, 4 figures, emulate ApJ forma

An amplitude-phase (Ermakov-Lewis) approach for the Jackiw-Pi model of bilayer graphene

In the context of bilayer graphene we use the simple gauge model of Jackiw and Pi to construct its numerical solutions in powers of the bias potential V according to a general scheme due to Kravchenko. Next, using this numerical solutions, we develop the Ermakov-Lewis approach for the same model. This leads us to numerical calculations of the Lewis-Riesenfeld phases that could be of forthcoming experimental interest for bilayer graphene. We also present a generalization of the Ioffe-Korsch nonlinear Darboux transformationComment: FTC, 11 pp, 5 figure