Flavor and energy inference for the high-energy IceCube neutrinos

We present a flavor and energy inference analysis for each high-energy neutrino event observed by the IceCube observatory during six years of data taking. Our goal is to obtain, for the first time, an estimate of the posterior probability distribution for the most relevant properties, such as the neutrino energy and flavor, of the neutrino-nucleon interactions producing shower and track events in the IceCube detector. For each event the main observables in the IceCube detector are the deposited energy and the event topology (showers or tracks) produced by the Cherenkov light by the transit through a medium of charged particles created in neutrino interactions. It is crucial to reconstruct from these observables the properties of the neutrino which generated such event. Here we describe how to achieve this goal using Bayesian inference and Markov chain Monte Carlo methods

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

Anisotropies in Non-Thermal Distortions of Cosmic Light from Photon-Axion Conversion

Ultralight axions which couple sufficiently strongly to photons can leave imprints on the sky at diverse frequencies by mixing with cosmic light in the presence of background magnetic fields. We explore such direction dependent grey-body distortions of the CMB spectrum, enhanced by resonant conditions in the IGM plasma. We also find that if such axions are produced in the early universe and represent a subdominant dark radiation component today, they could convert into X-rays in supervoids, and brighten them at X-ray frequencies.Comment: 11 pages, 1 figur

A semi-Markov model for price returns

We study the high frequency price dynamics of traded stocks by a model of returns using a semi-Markov approach. More precisely we assume that the intraday return are described by a discrete time homogeneous semi-Markov process and the overnight returns are modeled by a Markov chain. Based on this assumptions we derived the equations for the first passage time distribution and the volatility autocorreletion function. Theoretical results have been compared with empirical findings from real data. In particular we analyzed high frequency data from the Italian stock market from first of January 2007 until end of December 2010. The semi-Markov hypothesis is also tested through a nonparametric test of hypothesis

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

Pairing of few Fermi atoms in one dimension

We study a few Fermi atoms interacting through attractive contact forces in a one-dimensional trap by means of numerical exact diagonalization. From the combined analysis of energies and wave functions of correlated ground and excited states we find evidence of BCS-like pairing even for very few atoms. For moderate interaction strength, we reproduce the even-odd oscillation of the separation energy observed in [G. Zuern, A. N. Wenz, S. Murmann, A. Bergschneider, T. Lompe, and S. Jochim, Phys. Rev. Lett. 111, 175302 (2013)]. For strong interatomic attraction the arrangement of dimers in the trap differs from the homogeneous case as a consequence of Pauli blockade in real space.Comment: Major revision to appear in Physical Review