scholarly journals Aligned natural inflation in the Large Volume Scenario

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Stephen Angus ◽  
Kang-Sin Choi ◽  
Chang Sub Shin
Keyword(s):  
Convex Hull ◽  
Large Volume ◽  
Decay Constant ◽  
Small Volume ◽  
Theory Model ◽  
Axion Mass ◽  
Decay Constants ◽  
Alignment Mechanism ◽  
Axion Decay ◽  
Effective Decay

Abstract We embed natural inflation in an explict string theory model and derive observables in cosmology. We achieve this by compactifying the type IIB string on a Calabi-Yau orientifold, stabilizing moduli via the Large Volume Scenario, and configuring axions using D7-brane stacks. In order to obtain a large effective decay constant, we employ the Kim-Nilles-Peloso alignment mechanism, with the required multiple axions arising naturally from generically anisotropic bulk geometries. The bulk volumes, and hence the axion decay constants, are stabilized by generalized one-loop corrections and subject to various conditions: the Kähler cone condition on the string geometry; the convex hull condition of the weak gravity conjecture; and the constraint from the power spectrum of scalar perturbations. We find that all constraints can be satisfied in a geometry with relatively small volume and thus heavy bulk axion mass. We also covariantize the convex hull condition for the axion-dilaton-instanton system and verify the normalization of the extremal bound.

scholarly journals Axions and anomalous U(1)’s

2018 ◽  
Vol 33 (34) ◽  
pp. 1845001 ◽  
Author(s):  
Quentin Bonnefoy ◽  
Emilian Dudas
Keyword(s):  
Decay Constant ◽  
Vacuum Expectation ◽  
Expectation Values ◽  
Charged Scalar ◽  
Gauge Groups ◽  
Axion Mass ◽  
Decay Constants ◽  
Nonperturbative Effect ◽  
String Models ◽  
Axion Decay

Inspired by recent studies of high-scale decay constant or flavorful QCD axions, we review and clarify their existence in effective string models with anomalous U(1) gauge groups. We find that such models, when coupled to charged scalars getting vacuum expectation values, always have one light axion, whose mass can only come from nonperturbative effects. If the main nonperturbative effect is from QCD, then it becomes a Peccei–Quinn axion candidate for solving the strong CP problem. We then study simple models with universal Green–Schwarz mechanism and only one charged scalar field: in the minimal gaugino condensation case the axion mass is tied to the supersymmetry breaking scale and cannot be light enough, but slightly refined models maintain a massless axion all the way down to the QCD scale. Both kinds of models can be extended to yield intermediate scale axion decay constants. Finally, we gauge flavorful axion models under an anomalous U(1) and discuss the axion couplings which arise.

scholarly journals Digging into Axion Physics with (Baby)IAXO

Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 37
Author(s):  
Theopisti Dafni ◽  
Javier Galán
Keyword(s):  
Decay Constant ◽  
Fourth Generation ◽  
Special Issue ◽  
X Ray ◽  
Axion Mass ◽  
Wide Range ◽  
Discovery Potential ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
Main Candidate

Dark matter searches have been ongoing for three decades; the lack of a positive discovery of the main candidate, the WIMP, after dedicated efforts, has put axions and axion-like particles in the spotlight. The three main techniques employed to search for them complement each other well in covering a wide range in the parameter space defined by the axion decay constant and the axion mass. The International AXion Observatory (IAXO) is an international collaboration planning to build the fourth generation axion helioscope, with an unparalleled expected sensitivity and discovery potential. The distinguishing characteristic of IAXO is that it will feature a magnet that is designed to maximise the relevant parameters in sensitivity and which will be equipped with X-ray focusing devices and detectors that have been developed for axion physics. In this paper, we review aspects that motivate IAXO and its prototype, BabyIAXO, in the axion, and ALPs landscape. As part of this Special Issue, some emphasis is given on Spanish participation in the project, of which CAPA (Centro de Astropartículas y Física de Altas Energías of the Universidad de Zaragoza) is a strong promoter.

ON THE RELAXATION OF SUPERSTRING AXION MINI-CLUSTERS

2003 ◽  
Vol 18 (14) ◽  
pp. 947-953 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Decay Constant ◽  
Galactic Center ◽  
Coupling Parameter ◽  
Relaxation Mechanism ◽  
Superstring Theory ◽  
Decay Constants ◽  
Model Independent ◽  
Age Of The Universe ◽  
Axion Decay ◽  
The Universe

The cosmological axion theory leads to the prediction of axionic mini-clusters of mass M ~ 10-9M⊙, which form at the time t e of equipartition of matter and radiation. By applying the two-body relaxation formula of Spitzer and Hart, we show, for the heterotic superstring theory of Gross et al., that these mini-clusters, considered as point masses, themselves cluster into axion mini-stars of mass [Formula: see text] within the age of the Universe t0 only if they are located within a distance R ~ 0.1 pc of the Galactic Center. Here, λ ≡ fB/fA is the ratio of the second to model-independent axion decay constants, assuming the QCD decay constant to be in the range [Formula: see text], and [Formula: see text] is the strong-interaction coupling parameter. Thus, if axion mini-stars are to explain the microlensing observations by the EROS and MACHO groups towards the Galactic Bulge and the Large and Small Magellanic Clouds, then a collisionless relaxation mechanism is required, as proposed by Seidel and Suen (essentially the violent relaxation of Lynden–Bell), or the four-axion self-interaction effect considered by Tkachev.

scholarly journals Maximal axion misalignment from a minimal model

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Junwu Huang ◽  
Amalia Madden ◽  
Davide Racco ◽  
Mario Reig
Keyword(s):  
Phase Transition ◽  
Dark Matter ◽  
Decay Constant ◽  
Axion Mass ◽  
Qcd Phase Transition ◽  
Axion Field ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
The Universe ◽  
Simple Dynamical Model

Abstract The QCD axion is one of the best motivated dark matter candidates. The misalignment mechanism is well known to produce an abundance of the QCD axion consistent with dark matter for an axion decay constant of order 1012 GeV. For a smaller decay constant, the QCD axion, with Peccei-Quinn symmetry broken during inflation, makes up only a fraction of dark matter unless the axion field starts oscillating very close to the top of its potential, in a scenario called “large-misalignment”. In this scenario, QCD axion dark matter with a small axion decay constant is partially comprised of very dense structures. We present a simple dynamical model realising the large-misalignment mechanism. During inflation, the axion classically rolls down its potential approaching its minimum. After inflation, the Universe reheats to a high temperature and a modulus (real scalar field) changes the sign of its minimum dynamically, which changes the sign of the mass of a vector-like fermion charged under QCD. As a result, the minimum of the axion potential during inflation becomes the maximum of the potential after the Universe has cooled through the QCD phase transition and the axion starts oscillating. In this model, we can produce QCD axion dark matter with a decay constant as low as 6 × 109 GeV and an axion mass up to 1 meV. We also summarise the phenomenological implications of this mechanism for dark matter experiments and colliders.

scholarly journals Strong CP problem and axion dark matter with small instantons

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Ryuichiro Kitano ◽  
Wen Yin
Keyword(s):  
Dark Matter ◽  
Decay Constant ◽  
Strongly Coupled ◽  
Axion Mass ◽  
High Energies ◽  
Mass Correction ◽  
Large Correction ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
The Universe

Abstract The axion mass receives a large correction from small instantons if the QCD gets strongly coupled at high energies. We discuss the size of the new CP violating phases caused by the fact that the small instantons are sensitive to the UV physics. We also discuss the effects of the mass correction on the axion abundance of the Universe. Taking the small-instanton contributions into account, we propose a natural scenario of axion dark matter where the axion decay constant is as large as 1015-16 GeV. The scenario works in the high-scale inflation models.

scholarly journals An asymptotic formula for the pion decay constant in a large volume

2004 ◽  
Vol 590 (3-4) ◽  
pp. 258-264 ◽  
Author(s):  
Gilberto Colangelo ◽  
Christoph Haefeli
Keyword(s):  
Asymptotic Formula ◽  
Large Volume ◽  
Decay Constant ◽  
Pion Decay ◽  
Pion Decay Constant

scholarly journals Cosmologically allowed regions for the axion decay constant F

2018 ◽  
Vol 782 ◽  
pp. 181-184 ◽  
Author(s):  
Masahiro Kawasaki ◽  
Eisuke Sonomoto ◽  
Tsutomu T. Yanagida
Keyword(s):  
Decay Constant ◽  
Axion Decay Constant ◽  
Axion Decay

Substituent positional effect on radiative lifetimes of anthracene sulphonates

1980 ◽  
Vol 58 (10) ◽  
pp. 1046-1050 ◽  
Author(s):  
A. K. Gupta ◽  
Sekhar Basu ◽  
K. K. Rohatgi-Mukherjee
Keyword(s):  
Sharp Increase ◽  
Decay Constant ◽  
Radiative Decay ◽  
Steric Effect ◽  
Single Photon ◽  
Photon Counting ◽  
Molecular Geometry ◽  
Single Photon Counting ◽  
Decay Constants ◽  
Exciplex Formation

Excited state lifetimes of anthracene-1-sulphonate, anthracene-2-sulphonate, anthracene-1,5-disulphonate, and anthracene-1,8-disulphonate have been studied by photoselection and single photon counting methods. Experimental lifetimes are compared with theoretical values. For anthracene- monosulphonates, exciplex formation with water is proposed. In the case of anthracene-1,8-disulphonate, distortion in molecular geometry is found responsible for the higher non-radiative decay constant. Summation of nonradiative decay constants, Σki, increase in the series [Formula: see text]. The sharp increase for 1,8-AS is perhaps due to distortion of the molecular geometry due to steric effect of two bulky and charged —SO3− groups on the same side of the anthracene skeleton.

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