5,573 research outputs found

    Leptogenesis, Z' bosons, and the reheating temperature of the Universe

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    We study the impact for leptogenesis of new U(1) gauge bosons coupled to the heavy Majorana neutrinos. They can significantly enhance the efficiency of thermal scenarios in the weak washout regime as long as the Z' masses are not much larger than the reheating temperature (MZ′<10TrhM_{Z'}<10 T_{rh}), with the highest efficiencies obtained for Z' bosons considerably heavier than the heavy neutrinos (MZ′>100M1M_{Z'} > 100 M_1). We show how the allowed region of the parameter space is modified in the presence of a Z' and we also obtain the minimum reheating temperature that is required for these models to be successful.Comment: 14 pages, 6 figures; One figure added, discussion on the reheating temperature extende

    Charge state of C10 and C5 energetic cluster ions in amorphous carbon targets: simulations

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    We present here detailed simulations of the interaction of energetic C10 and C5 clusters at the energies of 1, 2, and 4 MeV per carbon atom with an amorphous carbon target. The spatial evolution of the cluster components is simulated accounting for both scattering and Coulomb explosion. The former is calculated by means of the Monte Carlo method while the latter is computed by means of molecular dynamics. The charge state of the individual cluster components is calculated as a function of penetration depth, and is determined by the competition between electron ionization and recombination. The results of calculations of the effect of the neighbouring cluster components on the suppression of the values of the charge state are presented and compared to the experimental values of Brunelle et al. Charge state suppression calculations for the 2 MeV/C clusters for both C10 and C5 agree well with the experimental results for penetration depths of less than about 500 and 250 Ã… respectively, assuming the intracluster Coulomb potential is screened by four target valence electrons. At 4 MeV/C the results are similar although less screening is required; a possible explanation is the inability of the plasma to completely screen the higher velocity projectiles. The 1 MeV/C calculated results however differ in their behaviour from the 2 and 4 MeV/C cases

    The matching problem between functional shapes via a BV-penalty term: a Γ\Gamma-convergence result

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    In this paper we study a variant of the matching model between functional shapes introduced in \cite{ABN}. Such a model allows to compare surfaces equipped with a signal and the matching energy is defined by the L2L^2-norm of the signal on the surface and a varifold-type attachment term. In this work we study the problem with fixed geometry which means that we optimize the initial signal (supported on the initial surface) with respect to a target signal supported on a different surface. In particular, we consider a BVBV or H1H^1-penalty for the signal instead of its L2L^2-norm. Several numerical examples are shown in order to prove that the BVBV-penalty improves the quality of the matching. Moreover, we prove a Γ\Gamma-convergence result for the discrete matching energy towards the continuous-one

    Supersymmetric Leptogenesis

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    We study leptogenesis in the supersymmetric standard model plus the seesaw. We identify important qualitative differences that characterize supersymmetric leptogenesis with respect to the non-supersymmetric case. The lepton number asymmetries in fermions and scalars do not equilibrate, and are related via a non-vanishing gaugino chemical potential. Due to the presence of new anomalous symmetries, electroweak sphalerons couple to winos and higgsinos, and QCD sphalerons couple to gluinos, thus modifying the corresponding chemical equilibrium conditions. A new constraint on particles chemical potentials corresponding to an exactly conserved RR-charge, that also involves the number density asymmetry of the heavy sneutrinos, appears. These new ingredients determine the 3×43\times 4 matrices that mix up the density asymmetries of the lepton flavours and of the heavy sneutrinos. We explain why in all temperature ranges the particle thermodynamic system is characterized by the same number of independent quantities. Numerical differences with respect to usual treatment remain at the O(1){\cal O}(1) level.Comment: 30 pages, 2 figures. Typos corrected, one reference added. Version published in JCA

    Identifying Unconventional E6_{\bf 6} Models at e+e−e^+ e^- Colliders

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    Recently it was shown that, in the framework of superstring inspired \E models, the presence of generation dependent discrete symmetries allows us to construct a phenomenologically viable class of models in which the three generations of fermions do not have the same embedding within the fundamental {\bf 27} dimensional representation of E6_6. In this scenario, these different embeddings of the conventional fermions imply that the left-handed charged leptons and the right-handed dd-type quarks are coupled in a non--universal way to the new neutral gauge bosons (Zθ)(Z_\theta) present in these models. It was also shown that a unique signature for this scenario, would be a deviation from unity for the ratio of cross sections for the production of two different lepton species in e+e−e^+e^- annihilation. However, several different scenarios are possible, depending on the particular assignment chosen for eLe_L, μL\mu_L and Ï„L\tau_L and for the right-handed dd-type quarks, as well as on the type of ZθZ_\theta boson. Such scenarios can not be disentangled from one another by means of cross section measurements alone. In this paper we examine the possibility of identifying the pattern of embeddings through measurements of polarized and unpolarized asymmetries for fermion pair-production at the 500 GeV e+e−e^+e^- Next Linear Collider (NLC). We show that it will be possible to identify the different patterns of unconventional assignments for the left-handed leptons and for the bRb_R quark, for ZθZ_\theta masses as large as ∼1.5\sim 1.5 TeV.Comment: Plain Tex, 15 pages, + 9 figure available upon request ([email protected] or [email protected]), UM-TH 93--1

    Explikative Verfahren in sozialwissenschaftlichen Texten. Eine handlungstheoretische Perspektive am Bespiel von infatti und n\ue4mlich.

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    La funzione dei testi accademico-scientifici \ue8 di trasmettere il sapere e di attivare nel lettore processi di costruzione, trasformazione e potenziamento del sapere, a questo scopo vengono utilizzati procedimenti esplicativi. Nel presente contributo viene analizzato l\u2019uso funzionale di infatti e n\ue4mlich in relazione a procedimenti esplicativi in un corpus di testi nell\u2019ambito delle scienze sociali. Seguendo un approccio pragmatico-funzionale viene illustrato il ruolo dei due connettori nel trasferimento e nell\u2019elaborazione del sapere mediante l\u2019azione comunicativa: iniziando da una categorizzazione etimologica ne viene analizzata la ricorrenza nei testi esaminati con particolare attenzione all\u2019intersecazione della loro funzionalit\ue0. Nel paragrafo finale si illustrano le ricadute didattiche dell\u2019uso di entrambi i connettori in tedesco ed in italiano. Wissenschaftstexte haben die Funktion, Wissen zu tradieren und bei den Lesenden kognitive Prozesse wie Wissensaufbau, -umbau und -ausbau auszul\uf6sen. Zu diesem Zweck bedienen sich die Autoren explikativer Verfahren, deren sprachliche Umsetzung Gegenstand dieses Beitrags ist. Aus einer handlungstheoretischen Perspektive werde ich den funktionalen Gebrauch von infatti und n\ue4mlich im Zusammenhang explikativer Verfahren in einem kleinen Korpus sozialwissenschaftlicher Texte n\ue4her beleuchten. Dabei geht es vor allem darum, die Rolle der beiden Ausdr\ufccke beim Prozess des Wissenstransfers und der Wissensverarbeitung zu analysieren. Nach einer kurzen Einf\ufchrung \ufcber funktionale Zwecke sozialwissenschaftlicher Texte, werde ich das Korpus pr\ue4sentieren und auf die funktional-pragmatische Kategorisierung beider Ausdrucksmittel so wie auf ihre Funktion im Verst\ue4ndigungshandeln eingehen. Dann werde ich ihr Vorkommen in den analysierten Texten untersuchen. Schlie flich werde ich die M\uf6glichkeit einer sich \ufcberschneidenden Funktionalit\ue4t der Ausdr\ufccke und ihre didaktischen Konsequenzen kommentieren

    Zur Erl\ue4uterung und Begr\ufcndung der eigenen Stellungnahme in DaF-Texten: Eine funktional-pragmatische Perspektive

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    Pubblicazione elettronica sul sito dell'Universit\ue0 di Augsburg, Germania al seguente indirizzo: http://opus.bibliothek.uni-augsburg.de/volltexte/2010/1547/pdf/RostRoth_Hirataka_Pragmatik.pd
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