On the extraction of spectral densities from lattice correlators

Hadronic spectral densities are important quantities whose non-perturbative knowledge allows for calculating phenomenologically relevant observables, such as inclusive hadronic cross-sections and non-leptonic decay-rates. The extraction of spectral densities from lattice correlators is a notoriously difficult problem because lattice simulations are performed in Euclidean time and lattice data are unavoidably affected by statistical and systematic uncertainties. In this paper we present a new method for extracting hadronic spectral densities from lattice correlators. The method allows for choosing a smearing function at the beginning of the procedure and it provides results for the spectral densities smeared with this function together with reliable estimates of the associated uncertainties. The same smearing function can be used in the analysis of correlators obtained on different volumes, such that the infinite volume limit can be studied in a consistent way. While the method is described by using the language of lattice simulations, in reality it is completely general and can profitably be used to cope with inverse problems arising in different fields of research.Comment: 15 pages, 14 figures. Updated to match published versio

Sostanze, attori e sensi: la temporalità della percezione nel corso dei rituali nahua

Questo articolo esamina la dimensione sensoriale degli oggetti, delle parole e delle azioni utilizzate nelle pratiche rituali dai Nahua della Sierra Norte di Puebla (Messico), le cui proprietà mutano nelle diverse fasi del rito e in funzione dei protagonisti – tanto umani quanto extraumani – che sono ritenuti presenti sulla scena rituale. Sulla base di alcuni esempi etnografici concernenti la terapia rituale di mali che interessano la sfera emozionale e animica e le offerte destinate ai defunti in occasione della loro celebrazione liturgica dei primi di novembre, si propone una interpretazione che metta in luce come le diverse facoltà percettive degli attori e dei destinatari del rito emergano con chiarezza dalla successione temporale delle fasi dei riti nahua, nelle quali i singoli sensi determinano variabili modalità di appropriazione e fruizione dei beni e delle essenze messi in circolazione nel corso degli atti rituali.This article examines the sensory dimension of the objects, words and actions used in ritual practices by the Nahua of the Sierra Norte of Puebla (Mexico), whose properties change through the different phases and according to the characters – both human and extra-human – who are believed to be present on the ritual scene. Based on some ethnographic examples concerning the ritual therapy of ailments affecting the emotional sphere and the human souls, as well as the offerings given to the dead on the occasion of their celebration in early November, I suggest that the different perceptive faculties of the actors and recipients of Nahua ritual clearly emerge from the temporal succession of the acts performed, in which the senses determine a variety of ways for appropriating and using the goods and essences that circulate during ritual acts

Síntesis controvertidas. Consideraciones en torno a los límites del concepto de sincretismo.

Sin resume

Miguel León-Portilla e il riscatto della civiltà nahua

In questa nota si delinea il profilo dello studioso messicano, storico, letterato e linguista, massimo conoscitore della produzione letteraria delle genti di lingua nahuatl che dominavano l’Altopiano centrale del Messico al momento della Conquista spagnola, agli inizi del XVI secolo. Si mette in evidenza il contributo innovativo di León-Portilla sull’atteggiamento degli studiosi nei confronti delle civiltà amerindiane e nei processi culturali e politici che hanno contribuito a conferire dignità e autonomia politica ai loro discendenti.This note outlines the profile of this eminent Mexican scholar, historian, and linguist, the greatest expert of the literary production of the Nahuatl-speaking peoples who dominated Mexico’s Central Plateau at the time of the Spanish Conquest, at the beginning of the 16th century. I highlight the innovative contribution León-Portilla gave to the attitude of scholars towards Amerindian civilizations and to the cultural and political processes that have contributed to giving dignity and political autonomy to their descendants

Weak Kerr Nonlinearity Boosts the Performance of Frequency-Multiplexed Photonic Extreme Learning Machines: A Multifaceted Approach

We provide a theoretical, numerical, and experimental investigation of the Kerr nonlinearity impact on the performance of a frequency-multiplexed Extreme Learning Machine (ELM). In such ELM, the neuron signals are encoded in the lines of a frequency comb. The Kerr nonlinearity facilitates the randomized neuron connections allowing for efficient information mixing. A programmable spectral filter applies the output weights. The system operates in a continuous-wave regime. Even at low input peak powers, the resulting weak Kerr nonlinearity is sufficient to significantly boost the performance on several tasks. This boost already arises when one uses only the very small Kerr nonlinearity present in a 20-meter long erbium-doped fiber amplifier. In contrast, a subsequent propagation in 540 meters of a single-mode fiber improves the performance only slightly, whereas additional information mixing with a phase modulator does not result in a further improvement at all. We introduce a model to show that, in frequency-multiplexed ELMs, the Kerr nonlinearity mixes information via four-wave mixing, rather than via self- or cross-phase modulation. At low powers, this effect is quartic in the comb-line amplitudes. Numerical simulations validate our experimental results and interpretation

Photonic Extreme Learning Machine based on frequency multiplexing

The optical domain is a promising field for physical implementation of neural networks, due to the speed and parallelism of optics. Extreme Learning Machines (ELMs) are feed-forward neural networks in which only output weights are trained, while internal connections are randomly selected and left untrained. Here we report on a photonic ELM based on a frequency-multiplexed fiber setup. Multiplication by output weights can be performed either offline on a computer, or optically by a programmable spectral filter. We present both numerical simulations and experimental results on classification tasks and a nonlinear channel equalization task.Comment: 22 pages, 16 figure

Fuori di sé. Viaggi ‘sciamanici’ ed esperienze di malattia nel Messico indigeno e meticcio

L'articolo esamina le concezioni indigene intorno alla percezione del mondo esterno e alla mobilità nello spazio – anche al di fuori dell’involucro corporeo – di quella componente della persona che è ritenuta il centro cognitivo individuale. In particolare, si esaminano le modalità con cui i Nahua percepiscono, rappresentano, diagnosticano e curano le malattie, esaminando alcune narrazioni al riguardo degli specialisti rituali. Infine, si riflette circa il fascino evocativo e la forza esplicativa che simili concezioni indigene posseggono anche al di fuori del contesto nahua, attraverso la drammatica testimonianza di un meticcio che proprio in tali concezioni ha reperito gli strumenti per rappresentarsi e dare un significato al profondo disorientamento sensoriale che una grave malattia neurologica gli aveva inflitto.The article examines indigenous concepts around the perception of the outside world and mobility in space - even outside of the housing body - that part of the person who is believed to be the individual's cognitive center. In particular, we examine the ways in which the Nahua perceive, represent, diagnose and treat illnesses, examining some narratives about the ritual specialists. Finally, it reflects about the evocative charm and the explanatory power that they possess similar indigenous conceptions, even outside the context of the Nahua, through the dramatic testimony of a half-breed who in these concepts has retrieved the tools to represent and make sense of profound disorientation sensory severe neurological disease had inflicted on him

Tlacochitta: ‘Vedere cose dormendo’. Enunciati e riflessioni sulle pratiche oniriche tra i Nahua del Messico

L’articolo esamina le concezioni e le pratiche intorno alla dimensione del sogno dei Nahua del Messico, tanto preispanici quanto odierni. Per la civiltà precolombiana degli Aztechi si prendono in considerazione le testimonianze storiche di cronisti ed evangelizzatori, così come i repertori linguistici e i testi in lingua nahuatl redatti nel primo periodo coloniale. Per il presente, ci si basa sulla documentazione etnografica raccolta dall’autore presso i Nahua del municipio di Cuetzalan (Puebla), mettendo in luce il rapporto tra le diverse componenti spirituali e l’attività onirica, il ruolo dei sogni nella “chiamata” alla professione degli specialisti rituali, la capacità di questi di esercitare un controllo attivo dei propri sogni, nonché le insidie che i viaggi onirici comportano per l’integrità della persona. La sfera onirica presenta per i Nahua un ambito in cui il confine tra il mondo umano e quello extraumano diviene poroso e che consente l’accesso a forme di conoscenza e di agentività precluse nello stato di veglia. Il sogno infine risulta un’esperienza fortemente socializzata, nella quale i modelli tradizionali forniscono strumenti cognitivi e operativi con cui conferire senso a episodi critici dell’esistenza e individuare per essi risposte non prive di efficacia.The article examines the conceptions and practices concerning dreams of the Nahuas of pre-Hispanic and contemporary Mexico. For the pre-Columbian Aztec civilization, the study is based on the historical testimonies of chroniclers and evangelizers, as well as the linguistic re pertoires and Nahuatl texts written during the early colonial period. As for the contemporary Nahuas, the author presents and analyses the ethnographic data he has collected in the municipality of Cuetzalan (Puebla), highlighting the relationship between the different spiritual components and the dream activity, the role of dreams in the professional "call" of ritual specialists, their ability to exercise an active control on dreaming, as well as the threats that dreams can imply for the integrity of the person. For the Nahuas, dreaming constitutes a domain in which the boundary between the human and extra-human world becomes porous and which allows access to forms of knowledge and agency that are precluded in the waking state. Finally, dreaming is a highly socialized experience, in which traditional models provide cognitive and operational tools with which to confer meaning to critical existential experiences and identify responses that often prove effective

Numerical studies of composite Higgs models

The Standard Model (SM) of particle physics describes the strong and electro-weak interactions with remarkable accuracy. Despite its success open questions, such as the Naturalness problem of the Higgs boson’s mass, suggest that the SM has to be considered an effective theory valid up to a certain cutoff scale at least in the TeV range. Models in which the Higgs boson emerges as a composite state extend the SM in order to solve its issues in the Higgs sector. These theories postulate the existence of new interactions and fundamental particles, offering a rich and interesting phenomenology. A quantitative understanding of their dynamics is crucial in order to aid the direct search of new physics. Due to the non-perturbative nature of such interactions, analytical solutions are often not reliable. Nonetheless, numerical simulations can be used within the established framework of lattice gauge theories. Within this context, this work develops numerical and analytical tools towards a quantitative, nonperturbative understanding of composite Higgs models. The focus will be centred around two gauge theories, described respectively by the gauge groups SU(4) and Sp(4), with fermions transforming in multiple representations of the gauge group. The discussion will be articulated around the phenomenology of these theories, the strategies for simulating them on the lattice, and the development of techniques that allow to unfold their dynamics

Comer (con) los difuntos: las ofrendas comestibles de Todos los Santos y las lógicas de la comensalía entre vivos y muertos en la Sierra de Puebla

Basandosi sui materiali etnographici raccolti tra i Nahua della Sierra Norte of Puebla, l'articolo cerca di cogliere la logia che ispira la composizione, la forma, la quantità delle offerte e i contenuti delle parole rituali rivolte ai defunti in occasione della festa di Todos los Santos: il simbolismo mortuario degli alimenti disposti sugli altari domestici rivela il loro latente significato antropofagico e dimostra che l'intera celebrazione è sostanzialmente strutturata sul principio di reciprocità e mira a soddisfare gli appetiti dei trapassati, al fine di distoglierli dal rivolgere la propria fame nei confronti dei viventi.La sequenza temporale in base alla quale i diversi attori rituali consumano le offerte commestibili mette in luce i diversi modi in cui i vivi e i morti divorano gli uni le raffigurazioni degli altri.each other’s representations.On the base of ethnographic data collected among the Nahua of the Northern Sierra of Puebla, I try to understand the logic that inspires the composition, form and quantity of the offerings and the content of the ritual words addressed to the deceased in Todos los Santos: the mortuary symbolism of the kinds of food arranged on the altars reveals its latent anthropophagical meaning and demonstrates that the entire celebration is essentially structured according to the principle of reciprocity, and aims to satisfying the appetites of the deceased, in order to prevent them from diverting their hunger towards the living. The temporal sequence according to which the various ritual agents eat the food offerings brings to light the various ways in which the living and the dead eat each other’s representations