Leptogenesis in the two right-handed neutrino model revisited

We revisit leptogenesis in the minimal non-supersymmetric type I see-saw mechanism with two right-handed (RH) neutrinos, including flavour effects and allowing both RH neutrinos N_1 and N_2 to contribute, rather than just the lightest RH neutrino N_1 that has hitherto been considered. By performing scans over parameter space in terms of the single complex angle z of the orthogonal matrix R, for a range of PMNS parameters, we find that in regions around z \sim \pm \pi/2, for the case of a normal mass hierarchy, the N_2 contribution can dominate the contribution to leptogenesis, allowing the lightest RH neutrino mass to be decreased by about an order of magnitude in these regions, down to M_1 \sim 1.3*10^11 GeV for vanishing initial N_2-abundance, with the numerical results supported by analytic estimates. We show that the regions around z \sim \pm \pi /2 correspond to light sequential dominance, so the new results in this paper may be relevant to unified model building.Comment: 41 pages, 10 figures; v2 matches published version in PR

Flavor effects on leptogenesis predictions

Flavor effects in leptogenesis reduce the region of the see-saw parameter space where the final predictions do not depend on the initial conditions, the strong wash-out regime. In this case we show that the lowest bounds holding on the lightest right-handed (RH) neutrino mass and on the reheating temperature for hierarchical heavy neutrinos, do not get relaxed compared to the usual ones in the one-flavor approximation, M_1 (T_reh) \gtrsim 3 (1.5) x 10^9 GeV. Flavor effects can however relax down to these minimal values the lower bounds holding for fixed large values of the decay parameter K_1. We discuss a relevant definite example showing that, when the known information on the neutrino mixing matrix is employed, the lower bounds for K_1 \gg 10, are relaxed by a factor 2-3 for light hierarchical neutrinos, without any dependence on \theta_13 and on possible phases. On the other hand, going beyond the limit of light hierarchical neutrinos and taking into account Majorana phases, the lower bounds can be relaxed by one order of magnitude. Therefore, Majorana phases can play an important role in leptogenesis when flavor effects are included

Active-sterile neutrino oscillations in the early Universe: asymmetry generation at low |delta m^2| and the Landau-Zener approximation

It is well established that active-sterile neutrino oscillations generate large neutrino asymmetries for very small mixing angles ($\sin^2 2\theta_0\lesssim 10^{-4}$), negative values of $\delta m^2$ and provided that $|\delta m^2|\gtrsim 10^{-4} {\rm eV^2}$. By numerically solving the quantum kinetic equations, we show that the generation still occurs at much lower values of $|\delta m^2|$. We also describe the borders of the generation at small mixing angles and show how our numerical results can be analytically understood within the framework of the Landau-Zener approximation thereby extending previous work based on the adiabatic limit. This approximate approach leads to a fair description of the MSW dominated regime of the neutrino asymmetry evolution and is also able to correctly reproduce its final value. We also briefly discuss the impact that neutrino asymmetry generation could have on big bang nucleosynthesis, CMBR and relic neutrinos.Comment: 29 pages, 8 figures; to appear on Phys. ReV. D; figure 7 added, new curves in figure 5a, new figure

Leptogenesis beyond the limit of hierarchical heavy neutrino masses

We calculate the baryon asymmetry of the Universe in thermal leptogenesis beyond the usual lightest right-handed (RH) neutrino dominated scenario (N_1DS) and in particular beyond the hierarchical limit (HL), M_1 << M_2 << M_3, for the RH neutrino mass spectrum. After providing some orientation among the large variety of models, we first revisit the central role of the N_1DS, with new insights on the dynamics of the asymmetry generation and then discuss the main routes departing from it, focusing on models beyond the HL. We study in detail two examples of `strong-strong' wash-out scenarios: one with `maximal phase' and the limit of very large M_3, studying the effects arising when delta_2=(M_2-M_1)/M_1 is small. We extend analytical methods already applied to the N_1DS showing, for example, that, in the degenerate limit (DL), the efficiency factors of the RH neutrinos become equal with the single decay parameter replaced by the sum. Both cases disprove the misconception that close RH neutrino masses necessarily lead to a final asymmetry enhancement and to a relaxation of the lower bounds on M_1 and on the initial temperature of the radiation-dominated expansion. We also explain why leptogenesis tends to favor normal hierarchy compared to inverted hierarchy for the left-handed neutrino masses.Comment: 30 pages, 8 figures; corrected typo in Eq. (67); shortened Introduction, Section 3 and Conclusions; one figure removed; added 2 references; to appear in JCA

Common fixed points of g-quasicontractions and related mappings in 0-complete partial metric spaces

Common fixed point results are obtained in 0-complete partial metric spaces under various contractive conditions, including g-quasicontractions and mappings with a contractive iterate. In this way, several results obtained recently are generalized. Examples are provided when these results can be applied and neither corresponding metric results nor the results with the standard completeness assumption of the underlying partial metric space can

Common fixed points for self-mappings on partial metric spaces

In this paper, we prove some results of a common fixed point for two self-mappings on partial metric spaces. Our results generalize some interesting results of Ilic et al. (Appl. Math. Lett. 24:1326-1330, 2011). We conclude with a result of the existence of a fixed point for set-valued mappings in the context of 0-complete partial metric spaces

Skeletal, dental and profilometric effects of Sabbagh Universal Spring 2 (SUS2) in a patient at the end of growth: a case report

Introduction: Malocclusions, which present a severe skeletal component, are difficult to solve through orthodontic treatment inpatients at the end of growth and often require a combined orthodontic-surgical treatment. The mandibular propulsion appliances "no compliance" now offer new possibilities for functional orthopedic treatment in borderline cases. Case presentation: A patient at the end of growth with a severe malocclusion (Class II Division 1), open bite with arches\u27 transversaldiscrepancy, refused the hypothesis of an orthodontic-surgical treatment, which represents the gold standard in such occlusal andskeletal problems, especially in subjects at the end of growth; consequently, a complex orthopedic-orthodontic treatment was chosen as the second choice. The patient has been successfully treated also through the use of SUS2 (Sabbagh Universal Spring 2; Dentaurum, Ispringen, Germany), a "no compliance" fixed functional appliance, which carried out a significant sagittal correction. Conclusion: The case report especially highlights the important sagittal correction obtained through the use of SUS2. The SUS2 had a functional outcome, which resulted in the maxillary growth stop and an effective sagittal mandibular growth increase. The SUS2effects, enhanced by elastics biomechanics, led to the bite closure and at the achievement of Class I occlusion

Radiative Inflation and Dark Energy

We propose a model based on radiative symmetry breaking that combines inflation with Dark Energy and is consistent with the WMAP 7-year regions. The radiative inflationary potential leads to the prediction of a spectral index 0.955 \lesssim n_S \lesssim 0.967 and a tensor to scalar ratio 0.142 \lesssim r \lesssim 0.186, both consistent with current data but testable by the Planck experiment. The radiative symmetry breaking close to the Planck scale gives rise to a pseudo Nambu-Goldstone boson with a gravitationally suppressed mass which can naturally play the role of a quintessence field responsible for Dark Energy. Finally, we present a possible extra dimensional scenario in which our model could be realised.Comment: 15 pages, 4 figures; v2: references added, appendix added, Section 5 slightly modified; content matches published versio

Transfer of Axial Chirality to the Nanoscale Endows Carbon Nanodots with Circularly Polarized Luminescence

We report the synthesis, purification and characterization of chiral carbon nanodots starting from atropoisomeric precursors. The obtained atropoisomeric carbon nanodots are soluble in organic solvents and have good thermal stability, which are desirable features for technological applications. The synthetic protocol is robust, as it supports a number of variations in terms of molecular doping agents. Remarkably, the combination of axially chiral precursors and 1,4-benzoquinone as doping agent results in green-emissive carbon dots displaying circularly polarized luminescence. Dissymmetry factors of |3.5|×10−4 are obtained in solution, without the need of any additional element of chirality. Introducing axial chirality expands the strategies available to tailor the properties of carbon nanodots, paving the way for carbon nanoparticles that combine good processability in organic solvents with engineered advanced chiroptical properties