On Higgs and sphaleron effects during the leptogenesis era

We discuss the effects of various processes that can be active during the leptogenesis era, and present the Boltzmann equations that take them into account appropriately. A non-vanishing Higgs number asymmetry is always present, enhancing the washout of the lepton asymmetry. This is the main new effect when leptogenesis takes place at $T>10^{12}$ GeV, reducing the final baryon asymmetry and tightening the leptogenesis bound on the neutrino masses. If leptogenesis occurs at lower temperatures, electroweak sphalerons partially transfer the lepton asymmetry to a baryonic one, while Yukawa interactions and QCD sphalerons partially transfer the asymmetries of the left-handed fields to the right-handed ones, suppressing the washout processes. Depending on the specific temperature range in which leptogenesis occurs, the final baryon asymmetry can be enhanced or suppressed by factors of order 20%--40% with respect to the case when these effects are altogether ignored.Comment: one reference adde

On fast CP violating interactions in leptogenesis

We show that when the relevant CP violating interactions in leptogenesis are fast, the different matter density asymmetries are determined at each instant by a balance condition between the amount of asymmetry being created and destroyed. This fact allows to understand in a simple way many features of leptogenesis in the strong washout regime. In particular, we find some non-trivial effects of flavour changing interactions that conserve lepton number, which are specially relevant in models for leptogenesis that rely heavily on flavour effects.Comment: V2: To match published version in JCAP. Minor changes, including one figure, with respect to V1. 17 pages, 4 figure

Metabolic responses to arsenite in rice seedlings that differed in grain arsenic concentration

© Crop Science Society of America. Arsenic (As) occurs naturally in the environment, and is present in all edible and nonedible plant tissues. Plants have multiple mechanisms to prevent plant injury by heavy metals such as As. These same mechanisms could be used to reduce accumulation of As in rice (Oryza sativa L.) grains. From previous study of 1765 international rice accessions, specific accessions were identified as having exceptionally high grain As concentrations (grain As accumulators) and others low grain As (grain As excluders). This study investigated As uptake, transport, and metabolism in six previously identified lines to determine which physiological responses, if any, were associated with accumulation or exclusion of As in grains. Hydroponically grown seedlings were treated with 0 (controls) or 100 mM arsenite [As(III)], and then whole seedlings were analyzed for concentrations of As plus key compounds involved in heavy metal metabolism. Both grain accumulators and grain excluders actively concentrated As within their roots, and both groups had 10-fold higher As concentrations in roots than leaves. In response to As(III), roots of both grain excluders and grain accumulators increased in cysteine and phytochelatin (PC) production, which suggests PC sequestration of As. In contrast, only grain excluders doubled in leaf glutathione (GSH) concentration by 72 h after As(III) addition. Because PC concentrations remained constant in leaves, it appears that the additional leaf GSH in the grain excluders was not used to produce more PC but may instead be forming As-GSH adducts, which also aid in As sequestration

The importance of flavor in leptogenesis

We study leptogenesis from the out-of-equilibrium decays of the lightest heavy neutrino $N_1$ in the medium (low) temperature regime, T\lsim 10^{12} GeV ($10^{10}$ GeV), where the rates of processes mediated by the $\tau$ (and $\mu$) Yukawa coupling are non negligible, implying that the effects of lepton flavors must be taken into account. We find important quantitative and qualitative differences with respect to the case where flavor effects are ignored: (i) The cosmic baryon asymmetry can be enhanced by up to one order of magnitude; (ii) The sign of the asymmetry can be opposite to what one would predict from the sign of the total lepton asymmetry $\epsilon_1$; (iii) Successful leptogenesis is possible even with $\epsilon_1=0$.Comment: 27 pages, 2 figures. Added 3 reference