Algebra of Non-Local Charges in Supersymmetric Non-Linear Sigma Models

We propose a graphic method to derive the classical algebra (Dirac brackets) of non-local conserved charges in the two dimensional supersymmetric non-linear $O(N)$ sigma model. As in the purely bosonic theory we find a cubic Yangian algebra. We also consider the extension of graphic methods to other integrable theories.Comment: LateX file, 19 pages, figures included with epsf; file with figures has been replace

Classical and quantum N=1 super W∞W_\infty-algebras

We construct higher-spin N=1 super algebras as extensions of the super Virasoro algebra containing generators for all spins $s\ge 3/2$. We find two distinct classical (Poisson) algebras on the phase super space. Our results indicate that only one of them can be consistently quantized.Comment: 10 pages, latex, no figure

Superloop Equations and Two Dimensional Supergravity

We propose a discrete model whose continuum limit reproduces the string susceptibility and the scaling dimensions of $(2,4m)$-minimal superconformal models coupled to $2D$-supergravity. The basic assumption in our presentation is a set of super-Virasoro constraints imposed on the partition function. We recover the Neveu-Schwarz and Ramond sectors of the theory, and we are also able to evaluate all planar loop correlation functions in the continuum limit. We find evidence to identify the integrable hierarchy of non-linear equations describing the double scaling limit as a supersymmetric generalization of KP studied by Rabin.Comment: 34 page

The Algebra of Non-Local Charges in Non-Linear Sigma Models

We obtain the exact Dirac algebra obeyed by the conserved non-local charges in bosonic non-linear sigma models. Part of the computation is specialized for a symmetry group $O(N)$. As it turns out the algebra corresponds to a cubic deformation of the Kac-Moody algebra. The non-linear terms are computed in closed form. In each Dirac bracket we only find highest order terms (as explained in the paper), defining a saturated algebra. We generalize the results for the presence of a Wess-Zumino term. The algebra is very similar to the previous one, containing now a calculable correction of order one unit lower.Comment: 27 pages + figures available via ftp, Plain TeX, IFUSP/P-106

Higher spin constraints and the super (W∞2⊕W1+∞2)( W_{\infty\over 2}\oplus W_{{1+\infty}\over 2}) algebra in the super eigenvalue model

We show that the partition function of the super eigenvalue model satisfies an infinite set of constraints with even spins $s=4,6,\cdots,\infty$. These constraints are associated with half of the bosonic generators of the super $\left( W_{\infty \over 2}\oplus W_{{1+\infty}\over 2}\right)$ algebra. The simplest constraint $(s=4)$ is shown to be reducible to the super Virasoro constraints, previously used to construct the model. All results hold for finite $N$.Comment: 14 pages, latex, no figure

Costruire il proprio progetto di vita professionale al liceo con l’E-Portfolio: tra autoriflessione e dialogo

The formulation of the professional life project makes a fundamental contribution to the formation of young people’s identity, since it implies a constant confrontation between the realism of the world of work and the image that young people have of themselves. The most recent Guidelines for guidance (MIM, 2022), attach particular importance to the E-Portfolio as a guidance tool that promotes the student’s educational-professional choices after leaving school. Possible ways in which the use of the E-Portfolio promotes the student's awareness and control of the learning process through the documentation of his or her experiences, interests, competences and educational goals, as well as an in-depth reflection on his or her future work, are shown. Finally, the E-Portfolio is presented as a useful “empirical basis” for conducting the guidance interview repeatedly, understood as a dialogical space in which the tutor-teacher can activate an effective communication dynamic with students and their parents

High entropy alloys obtained by field assisted powder metallurgy route: SPS and microwave heating

The aim of this work was to investigate the field assisted powder metallurgy route for producing HEAs at equimolar composition, i.e. FeCoNiCrAl, starting from metal powders. Both mixed, mechanically activated and mechanically alloyed powders have been used. The powders obtained by mechanical alloying were synthesized only by SPS, whereas the remaining ones were sintered by SPS or microwave heating. The investigated field assisted sintering techniques allowed an extremely short alloying time, high energy density on the load and negligible contamination by the surrounding environment. Both the conducted sintering-synthesis technology resulted not definitive to produce chemical homogeneity and to obtain a single stable structure. Thus a subsequently heat treatment was required. The post heat treatment, indeed, led to a single crystalline structure (FCC) and the material was fully recrystallized. After heat treatment samples are isomorphic: they exhibit two different phases with the same FCC cell, but different chemical composition, in detail Fe-Cr richer and Al-Ni richer. SPS-ed samples present a reduced porosity, while microwave processed ones are much more porous and this is reflected in the mechanical properties

Sviluppo di un acciaio per lavorazione a caldo rinforzato tramite alligazione meccanica

I compositi a matrice metallica combinano elevata durezza e buona tenacità offrendo la possibilità di modularele loro proprietà attraverso la scelta più opportuna del tipo, frazione e dimensioni del rinforzo. La produzione dicompositi a matrice metallica basati su acciai per lavorazioni a caldo è stata poco sviluppata in letteratura. Inquesto lavoro è stata investigata la possibilità di produrre un acciaio per lavorazioni a caldo AISI H13 rinforzatocon particelle ceramiche di diversa natura quali carburi (TiC), nitruri (TiN) e boruri (TiB2). Questi compostirisultano particolarmente promettenti per applicazioni ad alta temperatura data la loro elevata stabilità termica.Le polveri composite sono state prodotte tramite macinazione meccanica, ottenendo un affinamento dellamicrostruttura e una fine distribuzione delle particelle di rinforzo. Le polveri composite sono state sinterizzatetramite la tecnica Spark Plasma, in modo da preservare la fine microstruttura prodotta durante macinazionee limitare l’interazione tra matrice e particelle rinforzanti. Il composito con il 20%vol di TiB2 mostra la migliordensificazione raggiungendo quasi densità teorica. L’analisi diffrattometrica ai raggi-x di questo materialeevidenzia però la formazione di composti secondari, quali Fe2B e TiC, indicando una parziale decomposizione delTiB2. Tra i materiali sinterizzati, il composito il TiC mostra il maggior incremento di durezza