Axion Cosmology

1. Introduction 2. Models: the QCD axion; the strong CP problem; PQWW, KSVZ, DFSZ; anomalies, instantons and the potential; couplings; axions in string theory 3. Production and I.C.'s: SSB and non-perturbative physics; the axion field during inflation and PQ SSB; cosmological populations - decay of parent, topological defects, thermal production, vacuum realignment 4. The Cosmological Field: action; background evolution; misalignment for QCD axion and ALPs; cosmological perturbation theory - i.c.'s, early time treatment, axion sound speed and Jeans scale, transfer functions and WDM; the Schrodinger picture; simualting axions; BEC 5. CMB and LSS: Primary anisotropies; matter power; combined constraints; Isocurvature and inflation 6. Galaxy Formation; halo mass function; high-z and the EOR; density profiles; the CDM small-scale crises 7. Accelerated expansion: the c.c. problem; axion inflation (natural and monodromy) 8. Gravitational interactions with black holes and pulsars 9. Non-gravitational interactions: stellar astrophysics; LSW; vacuum birefringence; axion forces; direct detection with ADMX and CASPEr; Axion decays; dark radiation; astrophysical magnetic fields; cosmological birefringence 10. Conclusions A Theta vacua of gauge theories B EFT for cosmologists C Friedmann equations D Cosmological fluids E Bayes Theorem and priors F Degeneracies and sampling G Sheth-Tormen HMFComment: v2 greatly extended: 111 pages, 38 figures. Accepted for publication in Physics Report

Axions and ALPs: a very short introduction

The QCD axion was originally predicted as a dynamical solution to the strong CP problem. Axion like particles (ALPs) are also a generic prediction of many high energy physics models including string theory. Theoretical models for axions are reviewed, giving a generic multi-axion action with couplings to the standard model. The couplings and masses of these axions can span many orders of magnitude, and cosmology leads us to consider several distinct populations of axions behaving as coherent condensates, or relativistic particles. Light, stable axions are a mainstay dark matter candidate. Axion cosmology and calculation of the relic density are reviewed. A very brief survey is given of the phenomenology of axions arising from their direct couplings to the standard model, and their distinctive gravitational interactions.Comment: This article is a longer version of material contributed to the 13th Patras Workshop on Axions, WIMPs and WISPs, Thessaloniki, May 15 to 19, 201

A geometric description of the m-cluster categories of type D_n

We show that the m-cluster category of type D_n is equivalent to a certain geometrically-defined category of arcs in a punctured regular nm-m+1-gon. This generalises a result of Schiffler for m=1. We use the notion of the mth power of a translation quiver to realise the m-cluster category in terms of the cluster category.Comment: 14 pages, 11 figure

Coloured quivers for rigid objects and partial triangulations: The unpunctured case

We associate a coloured quiver to a rigid object in a Hom-finite 2-Calabi--Yau triangulated category and to a partial triangulation on a marked (unpunctured) Riemann surface. We show that, in the case where the category is the generalised cluster category associated to a surface, the coloured quivers coincide. We also show that compatible notions of mutation can be defined and give an explicit description in the case of a disk. A partial description is given in the general 2-Calabi-Yau case. We show further that Iyama-Yoshino reduction can be interpreted as cutting along an arc in the surface.Comment: 29 pages, 17 figures. Discussion in Section 6 clarified and expanded. Some minor corrections, clarification of notatio