Cosmology and perturbations in massive gravity

We study perturbations around some cosmological backgrounds in the dRGT theory of massive gravity. We develop a general formalism to calculate the perturbations around any background. We derive the Lagrangian for fluctuations in the small scale limit, and for the open FRW solution we repeat the analysis around the full background. We find that the perturbations display similar properties: the longitudinal modes of the massive graviton are instantaneous at quadratic level, but they acquire a time-kinetic term at cubic order.Comment: 17 pages. v2: references added, minor changes to match PRD published versio

The Bologna submillisecond pulsar survey

Since the discovery of the original millisecond pulsar, no pulsars with a shorter spin period (P<1.56 ms) were found. However, according to the most popular equations of state, the theoretical limiting spin period of a neutron star can be much shorter. On the other hand, most of the large scale searches for millisecond pulsars carried out so far were strongly biased against the detection of ultrashort periodicities. In this paper we describe a new large scale pulsar survey with a minimum detectable period much shorter than previous searches.Comment: 4 pages, two included figures, to be published in proceedings of "Pulsar Astronomy -- 2000 and Beyond", ASP Conf. Se

The need to develop a multidisciplinary expertise for the microbiological safety of operating theatres

Operating theatre ventilation systems and microbial air contamination in total joint replacement surgery: results of the GISIO-ISChIA study

Non-Gaussianity after BICEP2

We analyze primordial non-Gaussianity in single field inflationary models when the tensor/scalar ratio is large. Our results show that detectable levels of non-Gaussianity $f_{NL} \sim 50$ are still possible in the simplest class of models described by the effective theory of inflation. However, the shape is very tightly constrained, making a sharp prediction that could be confirmed or falsified by a future detection of non-Gaussianity.Comment: 5 pages, 2 figures. References and minor clarifications added. Version published in Phys. Rev. Let

Density Estimation and Combination under Model Ambiguity

This paper proposes a method for estimating the probability density of a variable of interest in the presence of model ambiguity. In the first step, each candidate parametric model is estimated minimizing the Kullback-Leibler "distance" (KLD) from a reference nonparametric density estimate. Given that the KLD represents a measure of uncertainty about the true structure, in the second step, its information content is used to rank and combine the estimated models. The paper shows that the resulting parameters estimator is root-n consistent and asymptotically normally distributed. The KLD between the nonparametric and the parametric density estimates is also shown to be asymptotically normally distributed. This result leads to determining the weights in the model combination, using the distribution function of a Normal centered on the average performance of all plausible models. As such, this combination technique does not require the true structure to belong to the set of competing models and is computationally simple. I apply the proposed method to estimate the density function of daily stock returns under different phases of the business cycle. The results indicate that the double Gamma distribution is more adequate than the Gaussian distribution in modeling stock returns, and that the combination outperforms each individual candidate model both in- and out-of-sampledensity forecasting, kullback-Leibler information, model combination

Field-induced Coulomb coupling in semiconductor macroatoms: application to "single-electron" quantum devices

A novel approach for the control of exciton-exciton Coulomb coupling in semiconductor macroatoms/molecules is proposed. We show that by applying properly tailored external fields, we can induce ---or significantly reinforce--- excitonic dipoles, which in turn allows to control and magnify intra- as well as inter-dot few-exciton effects. Such dipole-dipole interaction mechanism will be accounted for within a simple analytical model, which is found to be in good agreement with fully three-dimensional calculations. The proposed approach may play an important role for the design and realization of fully-optical quantum gates as well as ultrafast optical switches