The Growth-Volatility Relationship: New Evidence Based on Stochastic Volatility in Mean Models

This paper models the relationship between growth and volatility for G7 economies in the time period 1960-2009. It delivers for the first time estimates of this relationship based on a logarithm variant of stochastic volatility in mean (SV-M) models. The relationship appears significantly positive in Germany and Italy, but insignificant in other countries. We also show that output volatility has increased in all countries since the beginning of the financial crisis, which illustrates the end of the great moderation. For comparison, the paper also delivers estimates based on a logarithm variant of GARCH in mean (log-GARCH-M) models, the class of time series models previously used in the literature to estimate the growth-volatility relationship. We show that SV-M models deliver results preferable to those of log-GARCH-M models, despite the high computational cost of their estimation. SV-M models fit generally better data than log-GARCH-M ones. As their residuals do not violate distribution assumptions, they do not deliver dubious conclusions concerning the significance of the relationship, which is the case of the log-GARCH-model for France, the UK and the US. Finally, SV-M models suggest a positive impact of unexpected volatility on output growth, which is not taken into account by log-GARCH-M models.Growth, Volatility, Sequential Monte-Carlo Methods.

Centaurus A as the Source of ultra-high energy cosmic rays?

We present numerical simulations for energy spectra and angular distributions of nucleons above 10^{19} eV injected by the radio-galaxy Centaurus A at a distance 3.4 Mpc and propagating in extra-galactic magnetic fields in the sub-micro Gauss range. We show that field strengths B~0.3 micro Gauss, as proposed by Farrar and Piran, cannot provide sufficient angular deflection to explain the observational data. A magnetic field of intensity ~1 micro Gauss could reproduce the observed large-scale isotropy and could marginally explain the observed energy spectrum. However, it would not readily account for the E=320 plusminus 93 EeV Fly's Eye event that was detected at an angle 136 degrees away from Cen-A. Such a strong magnetic field also saturates observational upper limits from Faraday rotation observations and X-ray bremsstrahlung emission from the ambient gas (assuming equipartition of energy). This scenario may already be tested by improving magnetic field limits with existing instruments. We also show that high energy cosmic ray experiments now under construction will be able to detect the level of anisotropy predicted by this scenario. We conclude that for magnetic fields B~0.1-0.5 micro Gauss, considered as more reasonable for the local Supercluster environment, in all likelihood at least a few sources within ~10 Mpc from the Earth should contribute to the observed ultra high energy cosmic ray flux.Comment: 7 latex pages, 7 postscript figures included; for related numerical simulations see also http://www.iap.fr/users/sigl/r2e.htm

The impact of tidal errors on the determination of the Lense-Thirring effect from satellite laser ranging

The general relativistic Lense-Thirring effect can be detected by means of a suitable combination of orbital residuals of the laser-ranged LAGEOS and LAGEOS II satellites. While this observable is not affected by the orbital perturbation induced by the zonal Earth solid and ocean tides, it is sensitive to those generated by the tesseral and sectorial tides. The assessment of their influence on the measurement of the parameter mu, with which the gravitomagnetic effect is accounted for, is the goal of this paper. After simulating the combined residual curve by calculating accurately the mismodeling of the more effective tidal perturbations, it has been found that, while the solid tides affect the recovery of mu at a level always well below 1%, for the ocean tides and the other long-period signals Delta mu depends strongly on the observational period and the noise level: Delta mu(tides) amounts to almost 2% after 7 years. The aliasing effect of K1 l=3 p=1 tide and SRP(4241) solar radiation pressure harmonic, with periods longer than 4 years, on the perigee of LAGEOS II yield to a maximum systematic uncertainty on \m_{LT} of less than 4% over different observational periods. The zonal 18.6-year tide does not affect the combined residuals.Comment: 24 pages, 4 tables, 6 figures, submitted to Int. Journal of Mod. Phys. D. Changes in auctorship, references and conten

The E1B19K-deleted oncolytic adenovirus mutant Ad Delta 19K sensitizes pancreatic cancer cells to drug-induced DNA-damage by down-regulating Claspin and Mre11

This study was supported by a generous grant from the UK charity Pancreatic Cancer Research Fund (PCRF) and by the BCI CRUK Centre Grant [grant number C16420/A18066]

Trans-Planckian Dark Energy?

It has recently been proposed by Mersini et al. 01, Bastero-Gil and Mersini 02 that the dark energy could be attributed to the cosmological properties of a scalar field with a non-standard dispersion relation that decreases exponentially at wave-numbers larger than Planck scale (k_phys > M_Planck). In this scenario, the energy density stored in the modes of trans-Planckian wave-numbers but sub-Hubble frequencies produced by amplification of the vacuum quantum fluctuations would account naturally for the dark energy. The present article examines this model in detail and shows step by step that it does not work. In particular, we show that this model cannot make definite predictions since there is no well-defined vacuum state in the region of wave-numbers considered, hence the initial data cannot be specified unambiguously. We also show that for most choices of initial data this scenario implies the production of a large amount of energy density (of order M_Planck^4) for modes with momenta of order M_Planck, far in excess of the background energy density. We evaluate the amount of fine-tuning in the initial data necessary to avoid this back-reaction problem and find it is of order H/M_Planck. We also argue that the equation of state of the trans-Planckian modes is not vacuum-like. Therefore this model does not provide a suitable explanation for the dark energy.Comment: RevTeX - 15 pages, 7 figures: final version to appear in PRD, minor changes, 1 figure adde

Surgical Case Scheduling with sterilizing activity constraints

International audienc