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Search Results: 1 - 10 of 511 matches for " Nardi "
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Topics in Leptogenesis
Nardi, Enrico
High Energy Physics - Phenomenology , 2007, DOI: 10.1063/1.2751943
Abstract: Baryogenesis via leptogenesis provides an appealing mechanism to explain the observed baryon asymmetry of the Universe. Recent refinements in the understanding of the dynamics of leptogenesis include detailed studies of the effects of lepton flavors and of the role possibly played by the lepton asymmetries generated in the decays of the heavier singlet neutrinos $N_{2,3}$. In this talk I present a short review of these recent developments in the theory of leptogenesis.
Recent Issues in Leptogenesis
Nardi, Enrico
High Energy Physics - Phenomenology , 2007,
Abstract: Baryogenesis via leptogenesis provides an appealing mechanism to explain the observed baryon asymmetry of the Universe. Recent refinements in the understanding of the dynamics of leptogenesis include detailed studies of the effects of lepton flavors and of the role possibly played by the lepton asymmetries generated in the decays of the heavier singlet neutrinos $N_{2,3}$. A review of these recent developments in the theory of leptogenesis is presented.
La depresión adolescente
Bernardo Nardi
Psicoperspectivas : Individuo y Sociedad , 2008,
Abstract: Este artículo trata principalmente de la depresión adolescente, en sus diversas expresiones en las diferentes Organizaciones de Significado Personal (OSP): Trastornos alimenticios psicógenos (DAP), Fóbicas (FOB), Obsesiva (OBS) y Depresiva (DEP). Se revisan las diferentes sintomatologías que adquiere la depresión adolescente en las diferentes organizaciones, como también el diagnóstico, y las modalidades de intervención. Así mismo, el autor se focaliza en la explicación post racionalista de este período del ciclo vital del trastorno y su sintomatología, más que en la descripción sintomática de la misma, enfatizando más el proceso que en la indagación sobre las causas. El autor desarrolla un modelo de intervención del tipo procesal sistémico para abordar los diferentes aspectos psicoterapéuticos.
Rol de los procesos filogenéticos y ontogenéticos en el desarrollo de las organizaciones de significado personal
Bernardo Nardi
Psicoperspectivas : Individuo y Sociedad , 2008,
Abstract: En el estudio del desarrollo de las organizaciones de significado personal (OSP) dos preguntas asumen una particular importancia: cuáles son los factores concurrentes invariantes que determinan el cierre organizacional específico típico de cada OSP? y cuál es el significado adaptativo que ha llevado a la aparición y a la mantención de las OSP, desde los orígenes de la humanidad hasta hoy y en la historia personal de cada sujeto? Han sido identificados tres aspectos fundamentales: 1) regulación de la distancia (eje protección-separación, arcaico, basado en una modalidad concreta de pensamiento) que lleva al emerger de las OSP FOB-Prone, centradas en el control de las condiciones de protección/libertad; y DEP-Prone, basadas en el manejo de la separación y de la autodeterminación; 2) atención hacia lo externo (eje baja-alta sintonización) que requiere modalidades abstractas de pensamiento y que está a la base de las OSP con enfoque interior DEP-Prone y FOB-Prone y de las OSP con enfoque exterior DAP-Prone y OBS-Prone; 3) coherencia comunicativa (eje comunicaciones indefinidas ambiguas-definidas ambivalentes) que requieren competencias abstractas y que lleva a tomar en cuenta ya sean los aspectos difuminados de la realidad en los desarrollos DAP-Prone o aquellos antitéticos en los desarrollos OBS-Prone.
Memories of science education in Brazil: the physics education research
Roberto Nardi
Investiga??es em Ensino de Ciências , 2005,
Abstract: Recordings made in the last few decades, like as papers, congresses proceedings, research groups reports and interviews recently taken among researchers, allowed to rescue some details of the path drawn by the Physics Education research in Brazil. The interpretation of certain sense effects conferred by the interviewees and other in the recordings analyzed, allows us to perceive the plurality of this area of study, the diversity of factors considered important to its constitution and some characteristics of the research in this area.
Performing Electronic Dance Music: mimesis, reflexivity and the commodification of listening
NARDI, Carlo
Contemporanea : Revista de Comunica??o e Cultura , 2012,
Abstract: Recent changes in the economy of music have induced some musicians in the electronic ance scene to adapt their repertoire to concert performance. However, this conversion is far from being unproblematic, as electronic dance music, being based on additive operations, programming and merging of roles, resists, to an extent, live performance. I will then examine some of the strategies that musicians adopt in order to bring into the performance an element of actuality, focusing on the sensorial implications of this process. The stage concert, however, challenges not only the modes of production, but also the ideology of club culture, which is based on participation and inclusiveness. Mimesis, as a means to establish contact with the audience through identification, allows overcoming the division drawn by the stage. On the other hand, reflexivity, as a way to acknowledge the different roles at play, counteracts the role of mimesis and restores the distinction between audience and performer, thus substantiating the condition that prompted this transformation and that entails, in the first place, the commodification of musical experience.
Signals of Unconventional E$_6$ Models at $e^+e^-$ Colliders
Enrico Nardi
Physics , 1993, DOI: 10.1103/PhysRevD.49.4394
Abstract: Generation dependent discrete symmetries often appear in models derived from superstring theories. In particular, in the framework of E$_6$ models the presence of such symmetries is required in order to allow for the radiative generation of naturally small neutrino masses. Recently it was shown that by imposing suitable generation dependent discrete symmetries, a class of models can be consistently constructed in which the three sets of known fermions in each generation do not have the same assignments with respect to the {\bf 27} representation of E$_6$. In this scenario, the different embedding in the gauge group of the three generations implies in particular that the known charged leptons couple in a non--universal way to the new neutral gauge bosons $(Z_\beta)$ present in these models. We exploit this fact to study the signature of this class of models at present and future $e^+e^-$ colliders. We show that some signals of deviation from lepton universality as well as some other discrepancies with the standard model predictions which have been observed at the TRISTAN collider in the production rate of $\mu$ and $\tau$, can be accounted for if the $Z_\beta$ mass is not much heavier than 300 GeV. We also study the discovery limits for lepton universality violation of this type at LEP-2 and at the 500 GeV $e^+e^-$ Next Linear Collider (NLC). We show that models predicting unconventional assignments for the leptons will give an unmistakable signature, when the $Z_\beta$ mass is as heavy as $\sim 800$ GeV (LEP-2) and $\sim 2$ TeV (NLC).
Unconventional superstring derived E$_{\bf 6}$ models and neutrino phenomenology
Enrico Nardi
Physics , 1993, DOI: 10.1103/PhysRevD.48.3277
Abstract: Conventional superstring derived E$_6$ models can accommodate small neutrino masses if a discrete symmetry is imposed which forbids tree level Dirac neutrino masses but allows for radiative mass generation. Since the only possible symmetries of this kind are known to be generation dependent, we explore the possibility that the three sets of light states in each generation do not have the same assignments with respect to the 27 of $E_6$, leading to non universal gauge interactions under the additional $U(1)'$ factors for the known fermions. We argue that models realising such a scenario are viable, with their structure being constrained mainly by the requirement of the absence of flavor changing neutral currents in the Higgs sector. Moreover, in contrast to the standard case, rank 6 models are not disfavoured with respect to rank 5. By requiring the number of light neutral states to be minimal, these models have an almost unique pattern of neutrino masses and mixings. We construct a model based on the unconventional assignment scenario in which (with a natural choice of the parameters) $m_{\nut}\sim O(10)$eV is generated at one loop, $m_{\num}$ is generated at two loops and lies in a range interesting for the solar neutrino problem, and $\nue$ remains massless. In addition, since baryon and lepton number are conserved, there is no proton decay in the model. To illustrate the non-standard phenomenology implied by our scheme we also discuss a second scenario in which an attempt for solving the solar neutrino puzzle with matter enhanced oscillations and practically massless neutrinos can be formulated, and in which peculiar effects for the $\num$ --> $\nut$ conversion of the upward-going atmospheric neutrinos could arise as well.
Top-Charm flavor changing contributions to the effective $bsZ$ vertex
Enrico Nardi
Physics , 1995, DOI: 10.1016/0370-2693(95)01308-3
Abstract: We analyze the effects of a tree level flavor changing $tcZ$ vertex induced by a mixing with new isosinglet $Q=2/3$ quarks, on the effective $bsZ$ vertex. We compute the contributions arising from the new electroweak penguin diagrams involving one insertion of the $tcZ$ vertex. We show that a generalized GIM mechanism ensures the cancellation of the mass independent terms as well as of the new divergences. Unexpectedly, the presence of a $tcZ$ coupling cannot enhance the rates for the $Z$ mediated flavor changing decays \bsll\ and \bsnn, implying that these processes cannot be used to set limits on the $tcZ$ coupling. The additional effects of the heavy isosinglets are compared with the well studied effects of new isodoublets appearing in multi-generational models.
Renormalization Group Induced Neutrino Mass in Supersymmetry without R-parity
Enrico Nardi
Physics , 1996, DOI: 10.1103/PhysRevD.55.5772
Abstract: We study supersymmetric models without R parity and with universal soft supersymmetry breaking terms. We show that as a result of the renormalization group flow of the parameters, a misalignment between the directions in field space of the down-type Higgs vacuum expectation value $v_d$ and of the $\mu$ term is always generated. This misalignment induces a mixing between the neutrinos and the neutralinos, resulting in one massive neutrino. By means of a simple approximate analytical expression, we study the dependence on the different parameters that contribute to the misalignment and to $m_\nu$. In large part of the parameter space this effect dominates over the standard one-loop contributions to $m_\nu$; we estimate 1 MeV $\lsim m_\nu \lsim 1 GeV$. Laboratory, cosmological and astrophysical constraints imply $m_\nu \lsim 100 eV$. To be phenomenologically viable, these models must be supplemented with some additional mechanism to ensure approximate alignment and to suppress $m_\nu$.
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