4,163 research outputs found

    Finiteness and orbifold Vertex Operator Algebras

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    In this paper, I investigate the ascending chain condition of right ideals in the case of vertex operator algebras satisfying a finiteness and/or a simplicity condition. Possible applications to the study of finiteness of orbifold VOAs is discussed.Comment: 12 pages, comments are welcom

    Subresultants in multiple roots: an extremal case

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    We provide explicit formulae for the coefficients of the order-d polynomial subresultant of (x-\alpha)^m and (x-\beta)^n with respect to the set of Bernstein polynomials \{(x-\alpha)^j(x-\beta)^{d-j}, \, 0\le j\le d\}. They are given by hypergeometric expressions arising from determinants of binomial Hankel matrices.Comment: 18 pages, uses elsart. Revised version accepted for publication at Linear Algebra and its Application

    Green public procurement criteria for road infrastructures: State of the art and proposal of a weighted sum multicriteria analysis to assessenvironmental impacts

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    In the last years, the attention to environmental issue is growing, demonstrating the interest to protect the nature and to better use the non-renewable resources. At international level, and especially in the European Community, for different trades, a wide production of voluntary documents and institutional acts proves the interest and the need for a green economy. An innovative approach may lead to the experience of Green Public Procurements (GPP), to protect the environment as a public interest and to promote technological developments. So far, the experiences of GPP are limited, not entirely positive and in the field of road infrastructures almost entirely absent. Construction and maintenance of road infrastructures is objectively more complex than purchasing goods or services. The paper proposes the integration of the weighted sum multi-criteria analysis into existing procedures. The methodology needs for environmental labels related to materials, machines and works which contribute to the final product "road". The labels are recognized at international level and consistent with procedures, conditions and criteria currently published in road tenders, therefore the approach can be followed to pursue the environmental sustainability of road infrastructures without compromising the economic attention

    Regulation of T cell lymphokine production by killer cell inhibitory receptor recognition of self HLA class I alleles.

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    The killer cell inhibitory receptors (KIRs) are surface glycoproteins expressed by natural killer (NK) and T cells that specifically recognize defined groups of polymorphic human histocompatibility leukocyte antigen (HLA) class I molecules. Interactions between KIRs on NK or T cells and major histocompatibility complex (MHC) class I molecules on potential target cells inhibit cell-mediated cytotoxicity, presumably by delivering a negative signal preventing lymphocyte activation. In this study we examined whether KIRs also regulate cytokine production induced in response to T cell receptor-dependent T cell activation. CD4+ and CD8+ T cell clones were stimulated by bacterial superantigens in the presence or absence of monoclonal antibodies (mAbs) against the KIR NKB1 or MHC class I molecules, and production of tumor necrosis factor alpha and interferon gamma was evaluated. When bacterial superantigen was presented by an autologous antigen-presenting cell (APC) to a KIR+ T cell clone, cytokine production was always enhanced in the presence of anti-MHC class I mAb. Similarly, anti-KIR mAb also augmented cytokine production, provided that the APC expressed a HLA class I allele recognized by the KIR. These results suggest that recognition of autologous MHC class I molecules by KIR+ T cells provides a regulatory mechanism acting to modulate the potency of their responses to antigenic challenge

    The Noncommutative Geometry of the Quantum Projective Plane

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    We study the spectral geometry of the quantum projective plane CP^2_q, a deformation of the complex projective plane CP^2, the simplest example of a spin^c manifold which is not spin. In particular, we construct a Dirac operator D which gives a 0^+ summable spectral triple, equivariant under U_q(su(3)). The square of D is a central element for which left and right actions on spinors coincide, a fact that is exploited to compute explicitly its spectrum.Comment: v2: 26 pages. Paper completely reorganized; no major change, several minor one

    La riforma del bicameralismo italiano al traino dell’inesistente federalismo ovvero quando il bluff delle parole è smascherato dal niente dei fatti

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    Lo scritto, muovendo da una ricostruzione delle ragioni storiche del bicameralismo perfetto italiano (riconducibili all’esigenza di ampliare i “luoghi” e i “modi” attraverso i quali potesse esprimersi la rappresentanza politica nazionale, nonché alla preoccupazione di dotare l’ordinamento di un quadro procedurale che assicurasse la maggiore ponderazione possibile dell’indirizzo politico di maggioranza), mette in luce come l’attuale crisi del Parlamento non dipenda dalla presenza di due Camere dotate dei medesimi poteri. Lo svilimento della forma di governo parlamentare prevista dal dettato costituzionale è invece il frutto di una esaltazione del ruolo del Governo impostosi in via di prassi (nonostante la ricorrente “lamentela” secondo cui nel nostro ordinamento, se non si cambia il dettato costituzionale, sono destinati ad operare solo Governi “deboli”) e dell’assenza di rappresentatività delle Camere dovuta alla legge elettorale vigente (c.d. porcellum), in ragione della quale i deputati e i senatori non sono selezionati dagli elettori ma fiduciari dei loro capi-partito, che ne influenzano l’attività. Il problema che si impone con urgenza nel nostro ordinamento è dunque la rivitalizzazione dell’organo parlamentare che passa esclusivamente dal superamento dell’attuale, vergognoso sistema elettorale. Una volta che si riuscisse a ritornare ad una funzione genuinamente rappresentativa delle Assemblee elettive, sarebbe probabilmente utile al rilancio del Parlamento italiano correggere l’attuale bicameralismo partendo da una Camera delle Regioni, portando così a degno completamento il coraggioso disegno regionalistico dei Costituenti (al quale nemmeno il modello proposto dalla Lega Nord nel nome addirittura del “federalismo”, peraltro mai concretizzatosi in Italia, si avvicinava). La proposta attualmente in discussione al Senato di ripensamento del bicameralismo con riguardo al procedimento legislativo è una proposta di modifica “minimale” dell’attuale assetto costituzionale, probabilmente inutile al fine di una semplificazione e velocizzazione dell’iter legis, che, ove fosse approvata, produrrebbe piuttosto un rafforzamento delle prerogative dell’Esecutivo da usare in Parlamento, senza tuttavia variare nella sostanza la struttura organizzativa delle Camere e l’attuale sistema bicamerale

    Wick Rotation and Fermion Doubling in Noncommutative Geometry

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    In this paper, we discuss two features of the noncommmutative geometry and spectral action approach to the Standard Model: the fact that the model is inherently Euclidean, and that it requires a quadrupling of the fermionic degrees of freedom. We show how the two issues are intimately related. We give a precise prescription for the Wick rotation from the Euclidean theory to the Lorentzian one, eliminating the extra degrees of freedom. This requires not only projecting out mirror fermions, as has been done so far, and which leads to the correct Pfaffian, but also the elimination of the remaining extra degrees of freedom. The remaining doubling has to be removed in order to recover the correct Fock space of the physical (Lorentzian) theory. In order to get a Spin(1,3) invariant Lorentzian theory from a Spin(4) invariant Euclidean theory such an elimination must be performed after the Wick rotation. Differences between the Euclidean and Lorentzian case are described in detail, in a pedagogical way.Comment: Minor changes. To appear in PRD. 25 page
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