arXiv subjects

Giulio Tirabassi

Publications and source records attributed to Giulio Tirabassi.

5 recordsLinked to original sources

arXiv2024

Point process analysis of geographical diffusion of news in Argentina

The diffusion of information plays a crucial role in a society, affecting its economy and the well-being of the population. Characterizing the diffusion process is challenging because it is highly non-stationary and varies with the media type. To understand the spreading of newspaper news in Argentina, we collected data from more than 27000 articles published in six main provinces during four months. We classified the articles into 20 thematic axes and obtained a set of time series that capture daily newspaper attention on different topics in different provinces. To analyze the data we use a point process approach. For each topic, $n$, and for all pairs of provinces, $i$ and $j$, we use two measures to quantify the synchronicity of the events, $Q_s(i,j)$, which quantifies the number of events that occur almost simultaneously in $i$ and $j$, and $Q_a(i,j)$, which quantifies the direction of news spreading. Our analysis unveils how fast the information diffusion process is, showing pairs of provinces with very similar and almost simultaneous temporal variations of media attention. On the other hand, we also calculate other measures computed from the raw time series, such as Granger Causality and Transfer Entropy, which do not perform well in this context because they often return opposite directions of information transfer. We interpret this as due to different factors such as the characteristics of the data, which is highly non-stationary and the features of the information diffusion process, which is very fast and probably acts at a sub-resolution time scale.

physics.soc-ph↗

arXiv2022

Image classification using collective optical modes of an array of nanolasers

Recent advancements in nanolaser design and manufacturing open up unprecedented perspectives in terms of high integration densities and ultra-low power consumption, making these devices ideal for high-performance optical computing systems. In this work we exploit the symmetry properties of the collective modes of a nanolaser array for binary image classification. The implementation is based on a 8x8 array, and relies on the activation of a collective optical mode of the array, the so-called "zero mode", under spatially modulated pump patterns. We demonstrate that a simple training strategy allows us to achieve an overall success rate of 98% in binary image recognition.

cs.ET↗

arXiv2017

Inferring directed climatic interactions with renormalized partial directed coherence and directed partial correlation

Inferring interactions between processes promises deeper insight into mechanisms underlying network phenomena. Renormalised partial directed coherence (rPDC) is a frequency-domain representation of the concept of Granger causality while directed partial correlation (DPC) is an alternative approach for quantifying Granger causality in the time domain. Both methodologies have been successfully applied to neurophysiological signals for detecting directed relationships. This paper introduces their application to climatological time series. We first discuss the application to ENSO -- Monsoon interaction, and then apply the methodologies to the more challenging air-sea interaction in the South Atlantic Convergence Zone (SACZ). While in the first case the results obtained are fully consistent with present knowledge in climate modeling, in the second case the results are, as expected, less clear, and to fully elucidate the SACZ air-sea interaction, further investigations on the specificity and sensitivity of these methodologies are needed.

physics.ao-ph↗

arXiv2013

Self-collimated axial jets seeds from thin accretion disks

We show how an appropriate stationary crystalline structure of the magnetic field can induce a partial fragmentation of the accretion disk, generating an axial jet seed composed of hot plasma twisted in a funnel-like structure due to the rotation of the system. The most important feature we outline is the high degree of collimation, naturally following from the basic assumptions underlying the crystalline structure. The presence of non-zero dissipative effects allows the plasma ejection throughout the axial jet seed and the predicted values of the accretion rate are in agreement with observations.

astro-ph.SR↗

arXiv2013

On the Effects of Lag-Times in Networks Constructed from Similarities of Monthly Fluctuations of Climate Fields

The complex network framework has been successfully applied to the analysis of climatological data, providing, for example, a better understanding of the mechanisms underlying reduced predictability during El Niño or La Niña years. Despite the large interest that climate networks have attracted, several issues remain to be investigated. Here we focus in the influence of the periodic solar forcing in climate networks constructed via similarities of monthly averaged surface air temperature (SAT) anomalies. We shift the time series in each pair of nodes such as to superpose their seasonal cycles. In this way, when two nodes are located in different hemispheres we are able to quantify the similarity of SAT anomalies during the winters and during the summers. We find that data time-shifting does not significantly modify the network area weighted connectivity (AWC), which is the fraction of the total area of the Earth to which each node is con- nected. This unexpected network property can be understood in terms of how data time-shifting modifies the strength of the links connecting geographical regions in different hemispheres, and how these modifications are washed out by averaging the AWC.

physics.ao-ph↗