Leptogenesis is a class of scenarios where the baryon asymmetry of the Universe is produced from a lepton asymmetry generated in the decays of a heavy sterile neutrino. We explain the motivation for leptogenesis. We review the basic mechanism, and describe subclasses of models. We then focus on recent developments in the understanding of leptogenesis: finite temperature effects, spectator processes, and in particular the significance of flavor physics.Comment: 111 pages, 8 figures. Added Sect. 3 on anomalous B+L violation. Corrected equations (6.30) and (6.31). Added Sect. 9.1 with a simple example of the effects of flavours. Revised Sect. 10.1 on susy leptogenesis. Added several references, and other minor improvements. To be published in Physics Report

We study leptogenesis from the out-of-equilibrium decays of the lightest heavy neutrino N 1 in the medium (low) temperature regime, T < ∼ 10 12 GeV (10 10 GeV), where the rates of processes mediated by the τ (and µ) 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 ǫ 1 ; (iii) Successful leptogenesis is possible even with ǫ 1 = 0. * enrico.nardi@lnf.infn.it † yosef.nir@weizmann.ac.il

NOTE: First draft. We welcome comments, corrections, suggestions. For missing references we kindly ask to specify in relation to which topic and at which point of the review it would be appropriate to include a citation. We will not be able to address unspecifed requests.

(2017) 'Redening the axion window.', Physical review letters., 118 (3). 031801.Further information on publisher's website:https://doi.org/10.1103/PhysRevLett.118.031801Publisher's copyright statement:Reprinted with permission from the American Physical Society: Physical Review Letters 118, 031801 c (2017) by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modied, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. A major goal of axion searches is to reach inside the parameter space region of realistic axion models. Currently, the boundaries of this region depend on somewhat arbitrary criteria, and it would be desirable to specify them in terms of precise phenomenological requirements. We consider hadronic axion models and classify the representations R Q of the new heavy quarks Q. By requiring that (i) the Q's are sufficiently short lived to avoid issues with long-lived strongly interacting relics, (ii) no Landau poles are induced below the Planck scale; 15 cases are selected which define a phenomenologically preferred axion window bounded by a maximum (minimum) value of the axion-photon coupling about 2 times (4 times) larger than is commonly assumed. Allowing for more than one R Q , larger couplings, as well as complete axion-photon decoupling, become possible.