Neutrino Mass Models: From Type III See-saw to Non-Commutative Geometry

Today we know that neutrinos are massive, but we ignore both the origin of their masses and the reason why those masses are so tiny. A natural mechanism that can explain the smallness of neutrino masses is the See-saw Mechanism, that in this work is studied in its Type III variant. However, even in the scope of the See-saw Mechanism, the origin of the huge neutrino Majorana mass (which is a fundamental prerequisite for any see-saw model) remains to be explained. A possible explanation can be found in Twisted Non-Commutative Geometry (NCG): for particular twists of the so-called Connes Model (which is the NCG formulation of the Standard Model) a new scalar field appears naturally, whose vacuum expectation value generates a Majorana mass for the neutrinos, and the order of magnitude of said v.e.v. is precisely the natural scale of the Majorana mass of See-saw Mechanisms (10^15 GeV). In this work, three different twists of the Connes Model are studied, paying particular attention to the new boson field content, their gauge transformations, as well as the fermionic actions of each model

Non perturbative physics from NSPT: renormalons, the gluon condensate and all that

Numerical Stochastic Perturbation Theory (NSPT) enables very high order computations in Lattice Gauge Theories. We report on the determination of the gluon condensate from lattice QCD measurements of the basic plaquette. This is a long standing problem, which was eventually solved a few years ago in pure gauge. In this context NSPT is crucial: it is actually the only tool enabling the subtraction of the power divergent contribution associated to the identity operator in the OPE for the plaquette. This subtraction is actually a delicate issue, since the perturbative expansion of the plaquette is on general ground expected to be an asymptotic one, due to renormalons. This in turn results in ambiguities and the separation of scales in the OPE does not correspond to a separation of perturbative and non-perturbative contributions. All in all, one needs to absorb the ambiguities attached to the perturbative series into the definition of the condensate itself, i.e. one needs a prescription. A possible one amounts to summing the perturbative series up to its minimal term, which means computing up to orders which only NSPT can aim at. Our computation is the first one in QCD, with massless staggered fermions. In order to remove the zero-mode of the gauge field, twisted boundary conditions are adopted for the latter, consistently coupled to fermions in the fundamental representation supplemented with smell degrees of freedom.Comment: 7 pages, 4 figures. Talk given at the 36th Annual International Symposium on Lattice Field Theory, 22-28 July 2018, Michigan State University, East Lansing, Michigan, US

A critical survey of twisted spectral triples beyond the Standard Model

We review the applications of twisted spectral triples to the Standard Model. The initial motivation was to generate a scalar field, required to stabilise the electroweak vacuum and fit the Higgs mass, while respecting the first-order condition. Ultimately, it turns out that the truest interest of the twist lies in a new -- and unexpected -- field of 1-forms, which is related to the transition from Euclidean to Lorentzian signature

Twisted Standard Model in noncommutative geometry I: the field content

Noncommutative geometry provides both a unified description of the Standard Model of particle physics together with Einstein-Hilbert action (in euclidean signature) and some tools to go beyond the Standard Model. In this paper, we extend to the full noncommutative geometry of the Standard Model the twist (in the sense of Connes-Moscovici) initially worked out for the electroweak sector and the free Dirac operator only. Namely, we apply the twist also to the strong interaction sector and the finite part of the Dirac operator. To do so, we are forced to take into account a violation of the twisted first-order condition. As a result, we still obtain the extra scalar field required to stabilise the electroweak vacuum and fit the Higgs mass, but it now has two chiral components. We also get the additive field of 1-forms already pointed out in the electroweak model, but with a richer structure. Finally, we obtain a pair of Higgs doublets, which are expected to combine into a single Higgs doublet in the action formula, as will be investigated in the second part of this work.Comment: Violation of the twisted first-order condition now taken into account. Results unchange

Percorsi alternativi tra i sentieri del linguaggio a partire da «Claros del bosque»

En aquest treball tractarem concretament l’obra de Zambrano Claros del bosque, de l’any 1977, en la qual, segons diversos experts en la seva obra, veiem posada en pràctica la seva razón poética. En particular, ens centrarem en algunes parts del text que considerem més significatives en relació amb el tema que tractem aquí, és a dir, el paper de les paraules i el llenguatge dins la visió filosòfica més global de l’autora. In this paper we will deal specifically with Zambrano’s 1977 work Claros del bosque, in which, according to several experts on her work, we see her razón poética put into practice. In particular, we will focus on certain parts of the text that we consider most significant in terms of the specific theme we are dealing with here, namely the role of words and language within the author’s overall philosophical vision. En este trabajo trataremos concretamente de la obra de Zambrano Claros del bosque, del año 1977, en la que, según diversos expertos en su obra, pone en práctica su razón poética. En particular, nos centraremos en algunas partes del texto que consideramos más significativas en relación con el tema que aquí estudiamos, es decir, el papel de las palabras y el lenguaje en la visión filosófica más global de la autora. In questo lavoro ci occuperemo nello specifico dell’opera di Zambrano Claros del bosque, del 1977, in cui, secondo diversi esperti della sua opera, vediamo messa in atto la sua razón poética. In particolare ci focalizzeremo su alcune parti del testo che riteniamo più significative per quel che pertiene al tema specifico di cui qui ci stiamo occupando, vale a dire il ruolo della parola e del linguaggio all’interno della più complessiva visione filosofica dell’Autrice.

Probing large-order perturbative expansions in lattice gauge theories with fermions

Many perturbative expansions in quantum field theories are believed to be plagued by factorial divergences. This can be seen as a reflection of the fact that an all-order perturbative computation cannot give a complete description of the theory, as it misses all the nonperturbative features. In some cases the divergence is related to the existence of condensates, and being able to keep the asymptotic behaviour of the series under control is necessary to provide a sound definition of the condensates themselves. The goal of this work is to investigate the large-order behaviour of perturbative expansions in gauge theories. In order to achieve that, we employ Numerical Stochastic Perturbation Theory (NSPT), a numerical technique that allows for perturbative computations in quantum field theory. We present an implementation of NSPT that is able to yield results for high orders in the perturbative expansion of lattice gauge theories coupled to fermions. Performing calculations with fermions requires to overcome some challenges, due for example to the lack of chiral symmetry, or to the presence of doublers. Moreover, twisted boundary conditions (TBC), used to remove the gauge zero-momentum mode that spoils the convergence of the stochastic process, cannot accommodate easily fermions in all representations. In particular, we are forced to introduce a smell degree of freedom in order to include fermions in the fundamental representation with TBC. As a first application, we compute with NSPT the critical mass of two flavours of Wilson fermions up to order O(β-7) in a SU(3) gauge theory. We also implement, for the first time, staggered fermions in NSPT. The residual chiral symmetry of staggered fermions protects the theory from an additive mass renormalisation. We compute the perturbative expansion of the plaquette with two flavours of massless staggered fermions up to order O(β-35) in a SU(3) gauge theory, and investigate the renormalon behaviour of such series. We are able to subtract the power divergence in the Operator Product Expansion (OPE) for the plaquette and estimate the gluon condensate in massless QCD. Our results confirm that NSPT provides a viable way to probe systematically the asymptotic behaviour of perturbative series in QCD and, eventually, gauge theories with fermions in higher representations

Bodies and Natures

In the following paper, we will focus in particular on the research and reflections carried out by the French anthropologist Philippe Descola, who offers us a useful perspective to radically rethink the conceptualisation that, through a millenary movement, has led our Western culture, represented by what he calls the Moderns (borrowing an expression from Bruno Latour), to objectify the natural environment and to deploy it as a separate and unmanageable entity to be dominated.In the following paper, we will focus in particular on the research and reflections carried out by the French anthropologist Philippe Descola, who offers us a useful perspective to radically rethink the conceptualisation that, through a millenary movement, has led our Western culture, represented by what he calls the Moderns (borrowing an expression from Bruno Latour), to objectify the natural environment and to deploy it as a separate and unmanageable entity to be dominated

Rationale for an association between PD1 checkpoint inhibition and therapeutic vaccination against HIV

The pathogenesis of HIV immunodeficiency is mainly dependent on the cytopatic effects exerted by the virus against infected CD4+ T cells. However, CD4+ T cell loss cannot be the only pathogenic factor since severe opportunistic infections may develop in HIV infected patients with normal CD4+ T cell counts and since the recent START study indicated that absolute CD4+ T cell counts are not predictive for AIDS and non-AIDS events. Recently our group demonstrated that CD8+CD28-CD127lowCD39+ regulatory T lymphocytes, previously found highly concentrated within tumor microenvironment, circulate with elevated frequency in the peripheral blood of HIV infected patients. Here, we show that these cells, that at least in part are HIV specific, express the PD1 immune checkpoint. Based on these evidences and considerations, in this Perspective article we speculate on the opportunity to treat HIV infected patients with anti-PD1 immune checkpoint inhibitors as a way to counteract the T regulatory cell compartment and to unleash virus-specific immune responses. In order to potentiate the immune responses against HIV we also propose the potential utility to associate immune checkpoint inhibition with HIV-specific therapeutic vaccination, reminiscent of what currently applied in oncologic protocols. We suggest that such an innovative strategy could permit drug-sparing regimens and, perhaps, lead to eradication of the infection in some patients

Global bounds on the Type-III Seesaw

We derive general bounds on the Type-III Seesaw parameters from a global fit to flavor and electroweak precision data. We explore and compare three Type-III Seesaw realizations: a general scenario, where an arbitrary number of heavy triplets is integrated out without any further assumption, and the more constrained cases in which only 3 or 2 (minimal scenario) additional heavy states are included. The latter assumption implies rather non-trivial correlations in the Yukawa flavor structure of the model so as to reproduce the neutrino masses and mixings as measured in neutrino oscillations experiments and thus qualitative differences can be found with the more general scenario. In particular, we find that, while the bounds on most elements of the dimension 6 operator coefficients are of order 10−4 for the general and 3-triplet cases, the 2-triplet scenario is more strongly constrained with bounds between 10−5 and 10−7 for the different flavours. We also discuss how these correlations affect the present CMS constraints on the Type-III Seesaw in the minimal 2-triplet scenario