Vito Levi. Conversazioni e dialoghi musicali. Radio Trieste 1945-1954

Nel contesto dell’articolato percorso didattico e critico di Vito Levi spicca anche una rilevante produzione radiofonica, tra cui una Serie di 30 lezioni di Storia della musica tenute in forma dialogata alla Radio (1946-47) , accanto a un’ulteriore Serie di 30 conversazioni di argomento musicale tenute alla Radio di Trieste (1953-54) : due raccolte che rappresentano un’indagine a tutto campo attorno al mondo dei suoni, dalle origini ai giorni nostri, testimonianza della particolare capacità sintetica dell’autore nel tratteggiare e illuminare vividamente epoche, problematiche ed espressioni musicali

Processi cognitivi nell'analisi delle classi verbali dell'italiano: un approccio sperimentale

International audienceL'analisi della flessione, soprattutto verbale, nelle lingue romanze ha ricevuto un notevole impulso negli ultimi anni, in particolare dall'apporto alla ricerca in linguistica teorica di discipline come la psicolinguistica o le scienze cognitive. In questo articolo intendiamo riesaminare la ripartizione dei verbi italiani in classi, e osservare come la teoria morfologica e l'analisi sperimentale possano dare risultati convergenti e contribuire a mettere in luce i processi mentali che costituiscono la base della competenza morfologica dei parlanti (cf. Pirrelli 2007a; 2007b e, per un'illustrazione, Bonami et al. 2008). Nella prima parte, proporremo uno stato dell'arte della ricerca in morfologia flessiva, in particolare nell'ambito del modello "Parole e paradigmi", e suggeriremo una proposta di modellazione del sistema verbale dell'italiano. In particolar modo, ci soffermeremo sul concetto di regolarità, ossia sui criteri che servono a classificare i verbi, e in generale i lessemi, in regolari e irregolari. Nella seconda parte, renderemo conto dei risultati di una ricerca psicolinguistica, i cui risultati confermano, in maniera abbastanza prevedibile, l'esistenza di una macroclasse in italiano (quella dei verbi in -are). Per le altre classi, invece, la situazione è più complessa: anche i modelli di coniugazione generalmente considerati non regolari o semiregolari (ad esempio i verbi ad infinito in -ere atono) costituiscono poli di attrazione importanti nell'organizzazione delle forme flesse dell'italiano e sono facilmente estesi da parte dei locutori

Cosmic radiation backgrounds from primordial black holes

Recent measurements of the cosmic X-ray and radio backgrounds (CXB/CRB, respectively) obtained with Chandra and ARCADE2 report signals in excess of those expected from known sources, suggesting the presence of a yet undiscovered population of emitters. We investigate the hypothesis that such excesses are due to primordial black holes (PBHs) which may constitute a substantial fraction of dark matter (DM). We present a novel semi-analytical model which predicts X-ray and radio emission due to gas accretion onto PBHs, assuming that they are distributed both inside DM halos and in the intergalactic medium (IGM). Our model includes a self-consistent treatment of heating/ionization feedback on the surrounding environment. We find that (i) the emission from PBHs accreting in the IGM is subdominant at all times ($1\% \leq I_{\rm IGM}/I_{\rm tot} \leq 40\%$); (ii) most of the CXB/CRB emission comes from PBHs in DM mini-halos ($M_h \leq 10^6\ M_{\odot}$) at early epochs ($z>6$). While a small fraction ($f_{\rm PBH} \simeq 0.3\%$) of DM in the form of PBHs can account for the total observed CXB excess, the CRB one cannot be explained by PBHs. Our results set the strongest existing constraint on $f_{\rm PBH} \leq 3\times 10^{-4}\ (30/M_{\rm PBH})$ in the mass range $1-1000\, M_\odot$. Finally, we comment on the implications of our results on the global $\rm H_I$ 21cm signal.Comment: 13 pages, 10 figures, 2 tables. Accepted for publication in MNRA

The Filippov moments solution on the intersection of two and three manifolds

In this thesis, we study the Filippov moments solution for differential equations with discontinuous right-hand side. In particular, our aim is to define a suitable Filippov sliding vector field on a co-dimension $2$ manifold $\Sigma$, intersection of two co-dimension $1$ manifolds with linearly independent normals, and then to study the dynamics provided by this selection. More specifically, we devote Chapter 1 to motivate our interest in this subject, presenting several problems from control theory, non-smooth dynamics, vehicle motion and neural networks. We then introduce the co-dimension $1$ case and basic notations, from which we set up, in the most general context, our specific problem. In Chapter 2 we propose and compare several approaches in selecting a Filippov sliding vector field for the particular case of $\Sigma$ nodally attractive: amongst these proposals, in Chapter 3 we focus on what we called \emph{moments solution}, that is the main and novel mathematical object presented and studied in this thesis. There, we extend the validity of the moments solution to $\Sigma$ attractive under general sliding conditions, proving interesting results about the smoothness of the Filippov sliding vector field on $\Sigma$, tangential exit at first-order exit points, uniqueness at potential exit points among all other admissible solutions. In Chapter 4 we propose a completely new and different perspective from which one can look at the problem: we study minimum variation solutions for Filippov sliding vector fields in $\R^{3}$, taking advantage of the relatively easy form of the Euler-Lagrange equation provided by the analysis, and of the orbital equivalence that we have in the eventuality $\Sigma$ does not have any equilibrium points on it; we further remove this assumption and extend our results. In Chapter 5 examples and numerical implementations are given, with which we corroborate our theoretical results and show that selecting a Filippov sliding vector field on $\Sigma$ without the required properties of smoothness and exit at first-order exit points ends up dynamics that make no sense, developing undesirable singularities. Finally, Chapter 6 presents an extension of the moments method to co-dimension $3$ and higher: this is the first result which provides a unique admissible solution for this problem.Ph.D

X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies

In this thesis, I have investigated the evolution of the high-redshift (z > 3) AGN population by collecting data from some of the major Chandra and XMM-Newton surveys. The final sample (141 sources) is one of the largest selected at z> 3 in the X- rays and it is characterised by a very high redshift completeness (98%). I derived the spectral slopes and obscurations through a spectral anaysis and I assessed the high-z evolution by deriving the luminosity function and the number counts of the sample. The best representation of the AGN evolution is a pure density evolution (PDE) model: the AGN space density is found to decrease by a factor of 10 from z=3 to z=5. I also found that about 50% of AGN are obscured by large column densities (logNH > 23). By comparing these data with those in the Local Universe, I found a positive evolution of the obscured AGN fraction with redshift, especially for luminous (logLx > 44) AGN. I also studied the gas content of z < 1 AGN-hosting galaxies and compared it with that of inactive galaxies. For the first time, I applied to AGN a method to derive the gas mass previously used for inactive galaxies only. AGN are found to live preferentially in gas-rich galaxies. This result on the one hand can help us in understanding the AGN triggering mechanisms, on the other hand explains why AGN are preferentially hosted by star-forming galaxies

Phase estimation via quantum interferometry for noisy detectors

The sensitivity in optical interferometry is strongly affected by losses during the signal propagation or at the detection stage. The optimal quantum states of the probing signals in the presence of loss were recently found. However, in many cases of practical interest, their associated accuracy is worse than the one obtainable without employing quantum resources (e.g. entanglement and squeezing) but neglecting the detector's loss. Here we detail an experiment that can reach the latter even in the presence of imperfect detectors: it employs a phase-sensitive amplification of the signals after the phase sensing, before the detection. We experimentally demonstrated the feasibility of a phase estimation experiment able to reach its optimal working regime. Since our method uses coherent states as input signals, it is a practical technique that can be used for high-sensitivity interferometry and, in contrast to the optimal strategies, does not require one to have an exact characterization of the loss beforehand.Comment: 4 pages + supplementary information (10 pages), 3 + 4 figure