Chiral fermion mass and dispersion relations at finite temperature in the presence of hypermagnetic fields

We study the modifications to the real part of the thermal self-energy for chiral fermions in the presence of a constant external hypermagnetic field. We compute the dispersion relation for fermions occupying a given Landau level to first order in g'^2, g^2 and g_phi^2 and to all orders in g'B, where g' and g are the U(1)_Y and SU(2)_L couplings of the standard model, respectively, g_phi is the fermion Yukawa coupling, and B is the hypermagnetic field strength. We show that in the limit where the temperature is large compared to sqrt{g'B}, left- and right-handed modes acquire finite and different B-dependent masses due to the chiral nature of their coupling with the external field. Given the current bounds on the strength of primordial magnetic fields, we argue that the above is the relevant scenario to study the effects of magnetic fields on the propagation of fermions prior and during the electroweak phase transition.Comment: 11 pages 4 figures, published versio

The Importance of Campos Ecosystem as a World Food Producer and as a Provider of Ecosystem Services

The Campos ecosystem represent one of the largest grassland areas on the world, with great biodiversity in plants and animals. It contributes to improve world food security, based on ruminant livestock production, providing animal protein to feed more than 160.000.000 people. The research agenda for Campos ecosystem demands attention on the productivity and increasing variability phenomena, overgrazing, biodiversity standards and water contamination among other factors. It provides services including genetic resources, carbon storage, control of soil erosion, nutrient recycling, water production with low nutrient concentration and pest control. Overall, there is available technology to improve long-term livestock productivity and preserve current environmental indicators and improve sustainability, contributing to supply increasing world food demand