Topology in full QCD at high temperature: a multicanonical approach

We investigate the topological properties of $N_f = 2+1$ QCD with physical quark masses, at temperatures around 500 MeV. With the aim of obtaining a reliable sampling of topological modes in a regime where the fluctuations of the topological charge $Q$ are very rare, we adopt a multicanonical approach, adding a bias potential to the action which enhances the probability of suppressed topological sectors. This method permits to gain up to three orders of magnitude in computational power in the explored temperature regime. Results at different lattice spacings and physical spatial volumes reveal no significant finite size effects and the presence, instead, of large finite cut-off effects, with the topological susceptibility which decreases by 3-4 orders of magnitude while moving from $a \simeq 0.06$ fm towards the continuum limit. The continuum extrapolation is in agreeement with previous lattice determinations with smaller uncertainties but obtained based on ansatzes justified by several theoretical assumptions. The parameter $b_2$, related to the fourth order coefficient in the Taylor expansion of the free energy density $f(\theta)$, has instead a smooth continuum extrapolation which is in agreement with the dilute instanton gas approximation (DIGA); moreover, a direct measurement of the relative weights of the different topological sectors gives an even stronger support to the validity of DIGA.Comment: 23 pages, 13 figure

Are We Using Autoencoders in a Wrong Way?

Autoencoders are certainly among the most studied and used Deep Learning models: the idea behind them is to train a model in order to reconstruct the same input data. The peculiarity of these models is to compress the information through a bottleneck, creating what is called Latent Space. Autoencoders are generally used for dimensionality reduction, anomaly detection and feature extraction. These models have been extensively studied and updated, given their high simplicity and power. Examples are (i) the Denoising Autoencoder, where the model is trained to reconstruct an image from a noisy one; (ii) Sparse Autoencoder, where the bottleneck is created by a regularization term in the loss function; (iii) Variational Autoencoder, where the latent space is used to generate new consistent data. In this article, we revisited the standard training for the undercomplete Autoencoder modifying the shape of the latent space without using any explicit regularization term in the loss function. We forced the model to reconstruct not the same observation in input, but another one sampled from the same class distribution. We also explored the behaviour of the latent space in the case of reconstruction of a random sample from the whole dataset

Non-Perturbative Renormalisation and Kaon Physics

A general review is presented on the problem of non perturbative computation of the $K\to\pi\pi$ transition amplitude.Comment: 8 pages, Latex, uses espcrc2.sty, Talk given at LATTICE9

Deep Inelastic Scattering in Improved Lattice QCD. II. The second moment of structure functions

In this paper we present the 1-loop perturbative computation of the renormalization constants and mixing coefficients of the lattice quark operators of rank three whose hadronic elements enter in the determination of the second moment of Deep Inelastic Scattering (DIS) structure functions. We have employed in our calculations the nearest-neighbor improved ``clover-leaf'' lattice QCD action. The interest of using this action in Monte Carlo simulations lies in the fact that all terms which in the continuum limit are effectively of order $a$ ($a$ being the lattice spacing) have been demonstrated to be absent from on-shell hadronic lattice matrix elements. We have limited our computations to the quenched case, in which quark operators do not mix with gluon operators. We have studied the transformation properties under the hypercubic group of the operators up to the rank five (which are related to moments up to the fourth of DIS structure functions), and we discuss the choice of the operators considered in this paper together with the feasibility of lattice computations for operators of higher ranks. To perform the huge amount of calculations required for the evaluation of all the relevant Feynman diagrams, we have extensively used the symbolic manipulation languages Schoonschip and Form.Comment: 30 pages, latex + elsart + feynman (complete postscript file available upon request to [email protected]); submitted to Nuclear Physics

The Second Moment of the Pion Light Cone Wave Function

We present a preliminary result for second moment of the light cone wave function of the pion. This parameter is the subject of a discrepancy between theoretical predictions (coming from lattice and sum rules) and a recent experimental result (that remarkably agrees with purely perturbative predictions). In this work we exploit lattice hypercubic symmetries to remove power divergences and, moreover, implement a full 1-loop matching for all the contributing operators.Comment: 3 pages, proceedings of the Lattice 2002 conferenc

New insights in pediatric inflammatory bowel diseases: from disease pathogenesis to clinical and therapeutic management

Inflammatory bowel diseases (IBD), including Crohn’s disease (CD), Ulcerative colitis (UC) and IBD-unclassified (IBD-U) is a group of life-long chronic and relapsing inflammatory disorders of the gastrointestinal tract whose etiology has not been completely understood. The most recent evidences involve a complex interaction between host genetic, environmental and microbial influences, resulting in a dysregulated mucosal immune response against the commensal intestinal microbiota. Although the incidence and prevalence of IBD differ among countries, the general trend clearly highlights an overall increase over the past few decades in western countries, especially in adolescence and young adulthood. Paediatric IBD has several specific considerations when compared with adult IBD. These certainly include the relevant issues related to growth, development, pubertal maturation, bone health, and psychological impact on the patient and family, but also the unique features related to paediatric IBD phenotype, which is well-renowned to represent both a diagnostic and therapeutic challenge, being characterized by higher severity, including poor response to medical treatment, presence of extra-intestinal manifestations (EIM), and increased risk of surgery. This thesis project aims to provide new insights in paediatric IBD pathogenesis, to characterize the phenotype and the disease course of IBD in paediatric age and to improve the clinical and therapeutic strategies for the management of paediatric IBD

Axion phenomenology and θ\theta-dependence from Nf=2+1N_f = 2+1 lattice QCD

We investigate the topological properties of $N_f = 2+1$ QCD with physical quark masses, both at zero and finite temperature. We adopt stout improved staggered fermions and explore a range of lattice spacings $a \sim 0.05 - 0.12$ fm. At zero temperature we estimate both finite size and finite cut-off effects, comparing our continuum extrapolated results for the topological susceptibility $\chi$ with predictions from chiral perturbation theory. At finite temperature, we explore a region going from $T_c$ up to around $4\, T_c$, where we provide continuum extrapolated results for the topological susceptibility and for the fourth moment of the topological charge distribution. While the latter converges to the dilute instanton gas prediction the former differs strongly both in the size and in the temperature dependence. This results in a shift of the axion dark matter window of almost one order of magnitude with respect to the instanton computation.Comment: 24 pages, 12 figures, 5 tables, final version published in JHE

Recent progress on QCD inputs for axion phenomenology

The properties of the QCD axion are strictly related to the dependence of strong interactions on the topological parameter theta. We present a determination of the topological properties of QCD for temperatures up to around 600 MeV, obtained by lattice QCD simulations with 2+1 flavors and physical quark masses. Numerical results for the topological susceptibility, when compared to instanton gas computations, differ both in size and in the temperature dependence. We discuss the implications of such findings for axion phenomenology, also in comparison to similar studies in the literature, and the prospects for future investigations.Comment: Invited talk at XII Quark Confinement, 29 August - 3 September, 2016, Thessaloniki, Greece, 9 pages, 6 figure

Impact of the Rome II paediatric criteria on the appropriateness of the upper and lower gastrointestinal endoscopy in children.

BACKGROUND: The demand for paediatric gastrointestinal (GI) endoscopy has increased, resulting in a significant rise of overall costs. AIM: To assess the clinical impact of the Rome II criteria for functional gastrointestinal disorders when selecting paediatric patients who underwent GI endoscopy. METHODS: The indications and findings of GI endoscopic procedures performed before and after the publication of the Rome II criteria were evaluated retrospectively. RESULTS: Upper GI endoscopy was performed in 1124 children, whereas colonoscopy was performed in 500 subjects. A total of 607 (54%) oesophago-gastro-duodenoscopies (OGDs) were positive and 517 (46%) were negative, whereas 306 (61.1%) colonoscopies were positive and 194 (38.9%) were negative. Of the 1624 procedures, 26% were considered inappropriate according to the Rome II criteria. Inappropriate procedures decreased significantly after publication of the Rome II criteria (OR, 3.7; 95% CI, 1.8-7.5). Of 1202 appropriate GI endoscopies, 502 OGD (62.7%) were significantly contributive, compared with only 105 (32.5%) of the 323 inappropriate procedures (OR, 3.5; 95% CI, 2.6-4.6), whereas 265 (65.8%) colonoscopies were significantly contributive, compared with only 41 (42.3%) of the 97 inappropriate procedures (OR, 2.6; 95% CI, 1.6-4.1). CONCLUSIONS: The use of the criteria for functional gastrointestinal disorders makes a significant positive impact, they should reduce unnecessary paediatric GI endoscopy

AI for Health and Well Being @SI Lab

This presentation was delivered in the framework of a bilateral meeting between CNR and IVI on September 5, 2023