Evidence for a conformal phase in SU(N) gauge theories

We discuss the existence of a conformal phase in SU(N) gauge theories in four dimensions. In this lattice study we explore the model in the bare parameter space, varying the lattice coupling and bare mass. Simulations are carried out with three colors and twelve flavors of dynamical staggered fermions in the fundamental representation. The analysis of the chiral order parameter and the mass spectrum of the theory indicates the restoration of chiral symmetry at zero temperature and the presence of a Coulomb-like phase, depicting a scenario compatible with the existence of an infrared stable fixed point at nonzero coupling. Our analysis supports the conclusion that the onset of the conformal window for QCD-like theories is smaller than Nf=12, before the loss of asymptotic freedom at sixteen and a half flavors. We discuss open questions and future directions.Comment: 11 pages, 11 figures; extended analysis, conclusions unchanged. (version to appear in PRD

Caratteristiche e provenienza dei marmi

I frammenti lapidei considerati nel presente contributo sono stati in buona parte rinvenuti accatastati a poca distanza dai resti di fornaci (calcare) funzionali alla trasformazione delle pietre in calce. Si pu\uf2 ipotizzare che gli elementi recuperati fossero destinati alla calcinazione anche perch\ue9 costituiti esclusivamente da litotipi calcarei (marmi bianchi e colorati, calcari, arenarie calcaree). Assenti, invece, sono risultate essere le pietre non calcaree e comunemente utilizzate in et\ue0 romana come graniti, porfidi, andesiti o marmi dolomitici, non idonee alla produzione di calce

One,Two,Zero: Scales of Strong Interactions

We discuss our results on QCD with a number of fundamental fermions ranging from zero to sixteen. These theories exhibit a wide array of fascinating phenomena which have been under close scrutiny, especially in recent years, first and foremost is the approach to conformality. To keep this review focused, we have chosen scale generation, or lack thereof as a guiding theme, however the discussion will be set in the general framework of the analysis of the phases and phase transitions of strong interactions at zero and nonzero temperature.Comment: 15 pages, prepared for IJMPA Special Issue 'Recent Nonperturbative Developments in QCD-like Theories

On the particle spectrum and the conformal window

We study the SU(3) gauge theory with twelve flavours of fermions in the fundamental representation as a prototype of non-Abelian gauge theories inside the conformal window. Guided by the pattern of underlying symmetries, chiral and conformal, we analyze the two-point functions theoretically and on the lattice, and determine the finite size scaling and the infinite volume fermion mass dependence of the would-be hadron masses. We show that the spectrum in the Coulomb phase of the system can be described in the context of a universal scaling analysis and we provide the nonperturbative determination of the fermion mass anomalous dimension gamma*=0.235(46) at the infrared fixed point. We comment on the agreement with the four-loop perturbative prediction for this quantity and we provide a unified description of all existing lattice results for the spectrum of this system, them being in the Coulomb phase or the asymptotically free phase. Our results corroborate the view that the fixed point we are studying is not associated to a physical singularity along the bare coupling line and estimates of physical observables can be attempted on either side of the fixed point. Finally, we observe the restoration of the U(1) axial symmetry in the two-point functions.Comment: 40 pages, 22 figure

Chiral symmetry restoration in QCD with many flavours

We discuss the phases of QCD in the parameter space spanned by the number of light flavours and the temperature with respect to the realisation of chiral and conformal symmetries. The intriguing interplay of these symmetries is best studied by means of lattice simulations, and some selected results from our recent work are presented here.Comment: 10 pages, proceedings of the 9th International Workshop on Critical Point and Onset of Deconfinement, 17-21 November, 2014, ZiF, Bielefeld, German

Chiral symmetry of QCD with twelve light flavors

We study QCD with twelve light flavors at intermediate values of the bare lattice coupling. We contrast the results for the order parameter with different theoretical models motivated by the physics of the Goldstone phase and of the symmetric phase, and we perform a model independent analysis of the meson spectrum inspired by universal properties of chiral symmetry. Our analysis favors chiral symmetry restoration.Comment: 7 pages, 3 figures. To appear in the proceedings of the XXVIII International Symposium on Lattice Field Theory, Lattice2010, June 14-19, 2010, Villasimius, Ital

Reperti lapidei di et\ue0 romana rinvenuti a Fornovo Taro: provenienza e circolazione

Nelle collezioni del Museo Archeologico Nazionale di Parma tra i reperti litici di et\ue0 romana figurano anche tre oggetti recuperati a Fornovo Taro o nelle sue adiacenze diversi per contesto di ritrovamento e destinazione d\u2019uso, di cui si \ue8 analizzata la pietra ai fini di determinarne la provenienza e le possibili rotte commerciali. In particolare sono stati presi in esame:- una epigrafe frammentaria (n.inv. L 49), databile al II secolo d.C., gi\ue0 murata in uno dei pilastri della Pieve ed entrata a far parte delle collezioni museali nel 18671; - una piccola scultura raffigurante Afrodite accovacciata secondo il modello dello scultore ellenistico Doidalsas (n.inv. MANPr 31963), recuperata negli anni Ottanta del secolo scorso al margine occidentale di Piazza IV Novembre, databile ai primi decenni sempre del II secolo d.C.2; - una base di colonna (mancante di n.inv. e abbreviata con la sigla BCG), recuperata nel 1980 a Roncolungo di Sivizzano tra i materiali accatastati ai margini della strada statale dal proprietario del terreno in attesa di disfarsene