Coalescing binaries as possible standard candles

Gravitational waves detected from well-localized inspiraling binaries would allow to determine, directly and independently, both binary luminosity and redshift. In this case, such systems could behave as "standard candles" providing an excellent probe of cosmic distances up to $z <0.1$ and thus complementing other indicators of cosmological distance ladder.Comment: 6 pages, 5 figures. accepted in Astroparticle Physic

Gravitational and electromagnetic emission by magnetized coalescing binary systems

We discuss the possibility to obtain an electromagnetic emission accompanying the gravitational waves emitted in the coalescence of a compact binary system. Motivated by the existence of black hole configurations with open magnetic field lines along the rotation axis, we consider a magnetic dipole in the system, the evolution of which leads to (i) electromagnetic radiation, and (ii) a contribution to the gravitational radiation, the luminosity of both being evaluated. Starting from the observations on magnetars, we impose upper limits for both the electromagnetic emission and the contribution of the magnetic dipole to the gravitational wave emission. Adopting this model for the evolution of neutron star binaries leading to short gamma ray bursts, we compare the correction originated by the electromagnetic field to the gravitational waves emission, finding that they are comparable for particular values of the magnetic field and of the orbital radius of the binary system. Finally we calculate the electromagnetic and gravitational wave energy outputs which result comparable for some values of magnetic field and radius.Comment: 9 pages, 3 figures, to appear in Astroph. Sp.Scienc

Epistemic Logic Programs: a Novel Perspective and Some Extensions

Epistemic Logic Programs (ELPs), which propose an extension to Answer Set Programming (ASP) with epistemic operators, have their semantic defined, in various ways, in terms of world views, which are sets of belief sets. Several semantic approaches have in fact been proposed over time to characterize world views, and, recently, to also characterize semantic properties that should be met by any semantics for ELPs. We propose a new semantics, easy also from the computational point of view, but effective, also in order to compare the different semantic approaches. We also propose a significant extension to the ELP approach, by allowing epistemic atoms in rule heads

Epistemic Logic Programs: an Approach to Semantic Comparison

Epistemic Logic Programs (ELPs) extend Answer Set Programming (ASP) with epistemic operators. The semantics of such programs is provided in terms of world views, which are sets of belief sets. Several semantic approaches have been proposed over time to characterize world views. Recent work has introduced semantic properties that should be met by any semantics for ELPs. We propose a new method, easy but, we believe, effective, to compare the different semantic approaches

Temporalizing Epistemic Logic L-DINF

Agents and Multi-Agent Systems (MAS) are a technology that has many fields of application, which extend also to human sciences and where Computational Logic has been widely applied. In this paper, we join together two of our long-lasting lines of work in this field. In particular, we introduce time and time intervals into the epistemic logic L-DINF, that copes with group dynamics in MAS

The structure of the plasma sheet-lobe boundary in the Earth's magnetotail

The structure of the magnetotail plasma sheet-plasma lobe boundary was studied by observing the properties of tailward flowing O+ ion beams, detected by the ISEE 2 plasma experiment inside the boundary during three time periods. The computed value of the north-south electric field component as well as the O+ parameters are shown to change at the boundary. The results are related to other observations made in this region. The O+ parameters and the Ez component behavior are shown to be consistent with that expected from the topology of the electric field lines in the tail as mapped from the ionosphere

Comparative fragility methods for seismic assessment of masonry buildings located in Muccia (Italy)

The current paper focuses on a sector of the historic centre of Muccia, in the district of Macerata (Italy), affected by the seismic sequence that involved Central Italy in 2016. The main goal is comparison, in terms of fragility curves, among two vulnerability assessment methodologies (empirical and mechanical). The study area has been structurally and typologically identified according to the Building Typology Matrix (BTM). Physical vulnerability analysis of the urban-sector was performed through application of an index-based method, specifically for masonry building aggregates. An isolated masonry building, damaged after the seismic sequences, has been selected as a case study. For the assessed building, empirical fragility curves are presented according to Guagenti & Petrini’s correlation law. Furthermore, a numerical model has been set up by using the macro-element approach, which has allowed to perform non-linear static analyses. Mechanical properties of masonry were defined according to the New Technical Codes for Constructions (NTC18), assuming a limited knowledge level (LC1). Refined mechanical fragility functions have been derived and compared to the empirical ones. Analysis results have shown that the empirical method tends to overestimate by 5% and 10% the expected damage for slight and moderate thresholds. For PGA values greater than 0,3 g the damage levels decreased by 30% and 20%, with reference to the near collapse and collapse conditions, respectively

Large parallel and perpendicular electric fields on electron spatial scales in the terrestrial bow shock

Large parallel ($\leq$ 100 mV/m) and perpendicular ($\leq$ 600 mV/m) electric fields were measured in the Earth's bow shock by the vector electric field experiment on the Polar satellite. These are the first reported direct measurements of parallel electric fields in a collisionless shock. These fields exist on spatial scales comparable to or less than the electron skin depth (a few kilometers) and correspond to magnetic field-aligned potentials of tens of volts and perpendicular potentials up to a kilovolt. The perpendicular fields are amongst the largest ever measured in space, with energy densities of $\epsilon_0 E^2/ n k_b T_e$ of order 10%. The measured parallel electric field implies that the electrons can be demagnetized, which may result in stochastic (rather than coherent) electron heating

A regularized procedure to generate a deep learning model for topology optimization of electromagnetic devices

The use of behavioral models based on deep learning (DL) to accelerate electromagnetic field computations has recently been proposed to solve complex electromagnetic problems. Such problems usually require time-consuming numerical analysis, while DL allows achieving the topo-logically optimized design of electromagnetic devices using desktop class computers and reasonable computation times. An unparametrized bitmap representation of the geometries to be optimized, which is a highly desirable feature needed to discover completely new solutions, is perfectly managed by DL models. On the other hand, optimization algorithms do not easily cope with high dimensional input data, particularly because it is difficult to enforce the searched solutions as feasible and make them belong to expected manifolds. In this work, we propose the use of a variational autoencoder as a data regularization/augmentation tool in the context of topology optimization. The optimization was carried out using a gradient descent algorithm, and the DL neural network was used as a surrogate model to accelerate the resolution of single trial cases in the due course of optimization. The varia-tional autoencoder and the surrogate model were simultaneously trained in a multi-model custom training loop that minimizes total loss—which is the combination of the two models’ losses. In this paper, using the TEAM 25 problem (a benchmark problem for the assessment of electromagnetic numerical field analysis) as a test bench, we will provide a comparison between the computational times and design quality for a “classical” approach and the DL-based approach. Preliminary results show that the variational autoencoder manages regularizing the resolution process and transforms a constrained optimization into an unconstrained one, improving both the quality of the final solution and the performance of the resolution process