30,325 research outputs found
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
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
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
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