Direct numerical computation of disorder parameters

In the framework of various statistical models as well as of mechanisms for color confinement, disorder parameters can be developed which are generally expressed as ratios of partition functions and whose numerical determination is usually challenging. We develop an efficient method for their computation and apply it to the study of dual superconductivity in 4d compact U(1) gauge theory.Comment: 5 pages, 6 figures. Final revised version published in PR

Grammatizzazioni dello spazio-corpo: tra algoritmizzazione ed eccedenze

Lo spazio definito dalle nuove tecnologie digitali viene sempre più frequentemente descritto attorno ai concetti problematici di condivisione, cooperazione, moltiplicazione dei punti di enunciazione, facilitazione e accesso (più) democratico ai beni e ai servizi. Più realisticamente può essere raccontato come uno spazio fondato sulla chimera della neutralità e della calcolabilità dell'esistente. A partire dal tentativo continuo (e mai compiuto) di gestione delle pluri-potenzialità dello spazio-corpo attraverso la grammatizzazione algoritmica, ci interessa indagare la cartografia degli anfratti, delle zone di accumulo dell'ingestibile, coestensivi o conflittuali alla spazialità definita dal digitale. Fuggiamo tuttavia l'idea che le stesse spazialità definite dall'umano, dalla macchina, dal digitale, siano segmentate e definite autonomamente e senza ibridazioni. Partiamo piuttosto dal presupposto per il quale lo spazio-corpo è di per sé macchinico in quanto spazio dove è possibile esternalizzarele funzioni del capitale fisso (Marazzi, 2005); uno spazio che accoglie quelli che, nel linguaggio marxiano, si definiscono mezzi di produzione e che includono conoscenze acquisite, grammatiche produttive ed esperienze di lavoro passate. Questa porosità si traduce in uno spazio dove la macchina digitale e il vivente appaiono co-innervati in un intreccio macchinico vivo che coinvolge corpi, relazioni sociali, infrastrutture di comunicazione e network digitali. Se da una parte non è difficile immaginare la permeabilità di questo spazio macchinico vivente alla grammatizzazione inscritta nei codici algoritmici che stanno alla base delle nuove tecnologie digitali (Pasquinelli, 2014) dall’altra è necessario individuare quelle aree di impermeabilità, di frizione e di resistenza alla calcolabilità/automazione che mostrano come lo spazio-corpo possa riconfigurarsi in quanto terreno di lotta e di sperimentazione di pratiche liberanti e forme di autonomia o più drammaticamente di effetti drammatici indesiderati. E' il caso della necropolotica (Romagnoli 2012), quella particolare modalità di esercizio del biopotere che descrive il processo di avvelenamento del corpo che mangia i frutti e respira i fumi di un ciclo produttivo che ha ipotecato la stessa biosfera per l'accumulazione forsennata di profitto. Oppure è il caso della sessualità, che per quanto soggetta a sottilissime forme di biocontrollo ne eccede continuamente i perimetri per sondare spazialità sempre nuove ed irriducibili. O ancora, si pensi alle spazialità ibride che si producono attraverso le pratiche politiche collettive, spazialità per le quali l'ibridazione macchinica viene sottoposta simultaneamente a processi di cattura e di liberazione assolutamente non controllabili dalle grammatizzazioni algoritmiche

Covariant EBK quantization of the electromagnetic two-body problem

We discuss a method to transform the covariant Fokker action into an implicit two-degree-of-freedom Hamiltonian for the electromagnetic two-body problem with arbitrary masses. This dynamical system appeared 100 years ago and it was popularized in the 1940's by the still incomplete Wheeler and Feynman program to quantize it as a means to overcome the divergencies of perturbative QED. Our finite-dimensional implicit Hamiltonian is closed and involves no series expansions. The Hamiltonian formalism is then used to motivate an EBK quantization based on the classical trajectories with a non-perturbative formula that predicts energies free of infinities.Comment: 21 page

Recent Advances in Fairness Analysis of User Profiling Approaches in E-Commerce with Graph Neural Networks

User profiling is a critical procedure for e-commerce applications that captures online users’ attributes, understands user models, supports the provision of tailor-made goods and services, and improves user satisfaction. With the advent of novel technologies like Graph Neural Networks (GNNs), the performance of user profiling approaches has improved by leaps and bounds, in step with the growing concern about data and algorithmic fairness. This paper provides an overview of recent advances in the fairness analysis of GNN-based models for user profiling in the e-commerce domain. We present the results of our recent works addressing the need for an accurate analysis of state-of-the-art models and the lack of a unified tool for enabling any user to perform a fairness analysis on a specific dataset by leveraging the most performing models in this context. Our goal is to foster discussions on the potential implications of our work within the community, not only from a technical view but also from domain experts’ perspective

Do Graph Neural Networks Build Fair User Models? Assessing Disparate Impact and Mistreatment in Behavioural User Profiling

Recent approaches to behavioural user profiling employ Graph Neural Networks (GNNs) to turn users' interactions with a platform into actionable knowledge. The effectiveness of an approach is usually assessed with accuracy-based perspectives, where the capability to predict user features (such as gender or age) is evaluated. In this work, we perform a beyond-accuracy analysis of the state-of-the-art approaches to assess the presence of disparate impact and disparate mistreatment, meaning that users characterised by a given sensitive feature are unintentionally, but systematically, classified worse than their counterparts. Our analysis on two real-world datasets shows that different user profiling paradigms can impact fairness results. The source code and the preprocessed datasets are available at: https://github.com/erasmopurif/do_gnns_build_fair_models

Improved analysis of the bounds from the electroweak precision tests on the 4-site model

We present a new complete analysis of the electroweak precision observables within the recently proposed 4-site Higgsless model, which is based on the SU(2)_L x SU(2)_1 x SU(2)_2 x U(1)_Y gauge symmetry and predicts six extra gauge bosons, W_{1,2} and Z_{1,2}. Within the epsilon_i (i=1,2,3,b) parametrization, we compute for the first time the EWPT bounds via a complete numerical algorithm going beyond commonly used approximations. Both epsilon_{1,3} impose strong constraints. Hence, it is mandatory to consider them jointly when extracting EWPT bounds and to fully take in to account the correlations among the electroweak precison measurements. The phenomenological consequence is that the extra gauge bosons must be heavier than 250 GeV. Their couplings to SM fermions, even if bounded, might be of the same order of magnitude than the SM ones. In contrast to other Higgsless models, the 4-site model is not fermiophobic. The new gauge bosons could thus be discovered in the favoured Drell-Yan channel already during the present run of the LHC experiment.Comment: Latex file, 35 pages, 10 figures, corrected typos, published versio

Molecular Characterization and Functional Analysis of the Hb-hsp90-1 Gene in Relation to Temperature Changes in Heterorhabditis bacteriophora

Understanding how entomopathogenic nematodes respond to temperature changes and have adapted to the local environment is crucial to improve their potential as biocontrol agents. In order to improve understanding of Heterorhabditis bacteriophora’s potential adaptability to future climate changes, full-length cDNA and the corresponding gene of heat shock protein 90 (Hsp90) were isolated and fully characterized. The reproductive potential of the Apulian strain of H. bacteriophora increased when the temperature rose from 23 to 30°C, but no reproduction was found at 12°C. Expression analyses revealed that Hb-hsp90-1 was differentially expressed in Infective Juveniles (IJs) and adults (hermaphrodites, females and males). Up-regulation of Hb-hsp90-1 was higher during the recovery process in Galleria mellonella larvae than adults, thus confirming the protective role of Hb-hsp90-1 in coping with the host environment. Silencing of Hb-hsp90-1 resulted in a significant reduction (76%) in the expression level. Silenced IJs took longer than untreated nematodes to infect G. mellonella, showing that Hb-hsp90-1 could be also involved in chemosensation. Furthermore, the number of adults and IJs recovered from G. mellonella infected with silenced nematodes and incubated at 30°C was higher than that obtained from G. mellonella infected with untreated nematodes. These data confirm the crucial role of Hb-hsp90-1 allowing acclimation to increased temperatures and modulation of the recovery process

Assessment of poststress left ventricular ejection fraction by gated SPECT: comparison with equilibrium radionuclide angiocardiography

PURPOSE: We compared left ventricular (LV) ejection fraction obtained by gated SPECT with that obtained by equilibrium radionuclide angiocardiography in a large cohort of patients. METHODS: Within 1 week, 514 subjects with suspected or known coronary artery disease underwent same-day stress-rest (99m)Tc-sestamibi gated SPECT and radionuclide angiocardiography. For both studies, data were acquired 30 min after completion of exercise and after 3 h rest. RESULTS: In the overall study population, a good correlation between ejection fraction measured by gated SPECT and by radionuclide angiocardiography was observed at rest (r=0.82, p<0.0001) and after stress (r=0.83, p<0.0001). In Bland-Altman analysis, the mean differences in ejection fraction (radionuclide angiocardiography minus gated SPECT) were -0.6% at rest and 1.7% after stress. In subjects with normal perfusion (n=362), a good correlation between ejection fraction measured by gated SPECT and by radionuclide angiocardiography was observed at rest (r=0.72, p<0.0001) and after stress (r=0.70, p<0.0001) and the mean differences in ejection fraction were -0.9% at rest and 1.4% after stress. Also in patients with abnormal perfusion (n=152), a good correlation between the two techniques was observed both at rest (r=0.89, p<0.0001) and after stress (r=0.90, p<0.0001) and the mean differences in ejection fraction were 0.1% at rest and 2.5% after stress. CONCLUSION: In a large study population, a good agreement was observed in the evaluation of LV ejection fraction between gated SPECT and radionuclide angiocardiography. However, in patients with perfusion abnormalities, a slight underestimation in poststress LV ejection fraction was observed using gated SPECT as compared to equilibrium radionuclide angiocardiography