Semantic Enrichment of Scientific Documents with Semantic Lenses – Developing methodologies, tools and prototypes for their concrete use

Con questa dissertazione di tesi miro ad illustrare i risultati della mia ricerca nel campo del Semantic Publishing, consistenti nello sviluppo di un insieme di metodologie, strumenti e prototipi, uniti allo studio di un caso d‟uso concreto, finalizzati all‟applicazione ed alla focalizzazione di Lenti Semantiche (Semantic Lenses).

Radio follow-up of the gamma-ray flaring gravitational lens B0218+357

B0218+357 è un blazar soggetto al lensing che si trova a z=0.944. Questo sistema consiste in due componenti compatte (A e B) e un anello di Einstein. Recentemente è stato associato ad una sorgente gamma soggetta a burst osservata con il satellite Fermi-LAT. Questo blazar ha mostrato una forte variabilità in banda γ da agosto a settembre del 2012. Gli episodi di variabilità osservati hanno consentito di misurare per la prima volta in banda gamma il ritardo temporale previsto dalla teoria del lensing gravitazionale. Le osservazioni in banda gamma sono state seguite da un programma di monitoring con il Very Long Baseline Array (VLBA) in banda radio con lo scopo di verificare l’esistenza di una correlazione tra l’emissione nelle due bande. In questa Tesi tali osservazioni radio sono state analizzate con lo scopo di studiare la variabilità di B0218+357 e, quindi, attestare la connessione tra l’emissione alle alte energie e quella in banda radio. L’obiettivo principale di questo lavoro di Tesi è quello di studiare l’evoluzione della densità di flusso, dell’indice spettrale e della morfologia delle immagini A e B e delle loro sottocomponenti. I dati analizzati sono stati ottenuti con l’interferometro VLBA a tre frequenze di osser- vazione: 2.3, 8.4 GHz (4 epoche con osservazioni simultanee alle due frequenze) e 22 GHz (16 epoche). Le osservazioni hanno coperto un periodo di circa due mesi, subito successivo al flare in banda gamma. La riduzione dei dati è stata effettuata con il pacchetto AIPS. Dall’analisi delle immagini, nella componente B è possibile riconoscere la tipica struttura nucleo-getto chiaramente a tutte e tre le frequenze, invece nella componente A questa struttura è identificabile solo a 22 GHz. A 2.3 e 8.4 GHz la risoluzione non è sufficiente a risolvere nucleo e getto della componente A e l’emissione diffusa risulta dominante. Utilizzando il metodo dello stacking sulle immagini a 2.3 GHz, è stato possibile rivelare le parti più brillanti dell’Einstein ring associato a questa sorgente. Questo è stato possibile poiché la sorgente non ha mostrato alcun segno di variabilità significativa né di struttura né di flusso nelle componenti. Quindi dall’analisi delle curve di luce delle due componenti A e B non è emersa una variabilità significativa chiaramente associabile al flare osservato in banda gamma. Per verificare questo risultato, le curve di luce ottenute sono state confrontate con le osservazioni del radio telescopio OVRO (15 GHz) nel periodo corrispondente alle nostre osservazioni. La curva di luce OVRO è risultata in pieno accordo con le curve di luce ottenute durante questo lavoro di tesi e ha confermato che B0218+257 non ha mostrato un’importante attività radio nel periodo delle osservazioni VLBA. In definitiva, la mancanza di variabilità radio associata a quella osservata nei raggi gamma può essere dovuta al fatto che la regione in cui si è originato il flare gamma è otticamente spessa alle lunghezze d’onda radio, oppure non esiste una precisa correlazione tra le due emissioni, rimanendo quindi un problema aperto da investigare.

Fermion masses, leptogenesis and gravitational waves in SO(10)

Grand Unification Theories (GUTs) predict the unification of three of the fundamental forces and are a possible extension of the Standard Model, some of them predict neutrino mass and baryon asymmetry. We consider a minimal non-supersymmetric $SO(10)$ GUT model that can reproduce the observed fermionic masses and mixing parameters of the Standard Model. We calculate the scales of spontaneous symmetry breaking from the GUT to the Standard Model gauge group using two-loop renormalisation group equations. This procedure determines the proton decay rate and the scale of $U(1)_{B-L}$ breaking, which generates cosmic strings, and the right-handed neutrino mass scales. Consequently, the regions of parameter space where thermal leptogenesis is viable are identified and correlated with the fermion masses and mixing, the neutrinoless double beta decay rate, the proton decay rate, and the gravitational wave signal resulting from the network of cosmic strings. We demonstrate that this framework, which can explain the Standard Model fermion masses and mixing and the observed baryon asymmetry, will be highly constrained by the next generation of gravitational wave detectors and neutrino oscillation experiments which will also constrain the proton lifetime

Gravitational microscope in MACSJ1206: unveiling galaxy cluster member mass distribution

Gravitational lensing is a powerful tool to investigate the properties of the distribution of matter, be it barionic or dark. In this work we take advantage of Strong Gravitational Lensing to infer the properties of one of the galaxy-scale substructures that makes up the cluster MACSJ1206. It is relatively easy to model the morphology of the visible components of a galaxy, while the morphology of the dark matter distribution cannot be so easily constrained. Being sensitive to the whole mass, strong lensing provides a way to probe DM distribution, and this is the reason why it is the best tool to study the substructure. The goal of this work consists of performing an analysis of the substructure previously mentioned, an early type galaxy (ETG), by analyzing the highly magnified Einstein ring around it, in order to put stringent constraints on its matter distribution, that, for an ETG, is commonly well described by an isothermal profilele. This turns out to be interesting for three main different reasons. It is well known that galaxies in clusters are subject to interaction processes, both dynamic and hydrodynamic, that can significantly modify the distribution of matter within them. Therefore, finding a different profile from the one usually expected could be a sign that the galaxy has undergone processes that have changed its structure. Studying the mass distribution also means studying the dark matter component, which not only still presents great questions today, but which is also not obviously distributed in the same way as in an isolated galaxy. What emerges from the analysis is that the total mass distribution of the galaxy under examination turns out to have a slope much steeper than the isothermal usually expected.

Gravitational waves as dark sirens: an astrophysical and cosmological analysis

Despite the success of the ΛCDM model in describing the Universe, a possible tension between early- and late-Universe cosmological measurements is calling for new independent cosmological probes. Amongst the most promising ones, gravitational waves (GWs) can provide a self-calibrated measurement of the luminosity distance. However, to obtain cosmological constraints, additional information is needed to break the degeneracy between parameters in the gravitational waveform. In this thesis, we exploit the latest LIGO-Virgo-KAGRA Gravitational Wave Transient Catalog (GWTC-3) of GW sources to constrain the background cosmological parameters together with the astrophysical properties of Binary Black Holes (BBHs), using information from their mass distribution. We expand the public code MGCosmoPop, previously used for the application of this technique, by implementing a state-of-the-art model for the mass distribution, needed to account for the presence of non-trivial features, i.e. a truncated power law with two additional Gaussian peaks, referred to as Multipeak. We then analyse GWTC-3 comparing this model with simpler and more commonly adopted ones, both in the case of fixed and varying cosmology, and assess their goodness-of-fit with different model selection criteria, and their constraining power on the cosmological and population parameters. We also start to explore different sampling methods, namely Markov Chain Monte Carlo and Nested Sampling, comparing their performances and evaluating the advantages of both. We find concurring evidence that the Multipeak model is favoured by the data, in line with previous results, and show that this conclusion is robust to the variation of the cosmological parameters. We find a constraint on the Hubble constant of H0 = 61.10+38.65−22.43 km/s/Mpc (68% C.L.), which shows the potential of this method in providing independent constraints on cosmological parameters. The results obtained in this work have been included in [1].

Spectral distortions of the cosmic microwave background and small-scale gravitational waves as new windows on the Early Universe

In this thesis, we explore constraints which can be put on the primordial power spectrum of curvature perturbations beyond the scales probed by anisotropies of the cosmic microwave background and galaxy surveys. We exploit present and future measurements of CMB spectral distortions, and their synergy with CMB anisotropies, as well existing and future upper limits on the stochastic background of gravitational waves. We derive for the first time phenomenological templates that fit small-scale bumps in the primordial power spectrum generated in multi-field models of inflation. By using such templates, we study for the first time imprints of primordial peaks on anisotropies and spectral distortions of the cosmic microwave background and we investigate their contribution to the stochastic background of gravitational waves. Through a Monte Carlo Markov Chain analysis we infer for the first time the constraints on the amplitude, the width and the location of such bumps using Planck and FIRAS data. We also forecast how a future spectrometer like PIXIE could improve FIRAS boundaries. The results derived in this thesis have implications for the possibility of primordial black holes from inflation.