ON THE SUPERSTRING AXION MINI-STAR

1998 ◽  
Vol 13 (13) ◽  
pp. 1007-1017 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Gravitational Collapse ◽  
Mass Formula ◽  
Decay Constant ◽  
Gravitational Constant ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Planck Mass ◽  
Upper Limit ◽  
Axion Decay Constant ◽  
Axion Decay

The theory of the pressure-free-boson mini-star of mass M, whose radius r=2GM/v2 is equated via the indeterminacy principle to ℏ/mv, where [Formula: see text] is the Newton gravitational constant, M P being the Planck mass and m the mass of the boson, travelling at velocity v, is applied to the superstring axion. For a bounded object, the upper limit to the axion potential [Formula: see text] constrains the axions to move at non-relativistic velocities [Formula: see text] where [Formula: see text] GeV is the axion decay constant, predicting the existence of an axion mini-star of mass [Formula: see text]. Such objects can in principle form by gravitational collapse below the temperature T≈100 eV, and are tentatively identified with the microlensing objects recently detected in our Galaxy and in the direction of the Large Magellanic Cloud.

scholarly journals An Upper Limit on the Mass of a Central Black Hole in the Large Magellanic Cloud from the Stellar Rotation Field

2017 ◽  
Vol 846 (1) ◽  
pp. 14 ◽  
Author(s):  
H. Boyce ◽  
N. Lützgendorf ◽  
R. P. van der Marel ◽  
H. Baumgardt ◽  
M. Kissler-Patig ◽  
...  
Keyword(s):  
Black Hole ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Stellar Rotation ◽  
Central Black Hole ◽  
Upper Limit ◽  
Rotation Field

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

scholarly journals Numerical analysis of Coleman–de Luccia tunneling

2016 ◽  
Vol 31 (24) ◽  
pp. 1650131 ◽  
Author(s):  
Yuhei Goto ◽  
Kazumi Okuyama
Keyword(s):  
Decay Constant ◽  
Periodic Potential ◽  
Thin Wall ◽  
False Vacuum ◽  
Vacuum Decay ◽  
Text Type ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
Range Of Values ◽  
Type Potential

In this paper, we study the false vacuum decay of a single scalar field [Formula: see text] coupled to gravity described by the Coleman–de Luccia (CdL) instanton. We show that it is possible to numerically calculate the bounce factor, which is related to the CdL tunneling rate, without using the thin-wall approximation. In this paper, we consider [Formula: see text]- and [Formula: see text]-type potentials as examples, which have cosmological and phenomenological applications. Especially, in the [Formula: see text]-type potential, we show that the range of values in which axion decay constant can take is restricted by the form of the periodic potential if the CdL tunneling occurs.

The Kinematics and Age of the Planetary Nebulae in the Large Magellanic Cloud

1986 ◽  
Vol 6 (4) ◽  
pp. 464-467 ◽  
Author(s):  
Stephen J. Meatheringham ◽  
Michael A. Dopita
Keyword(s):  
Rotation Curve ◽  
Velocity Dispersion ◽  
Transverse Velocity ◽  
Planetary Nebulae ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Upper Limit ◽  
Mass Estimate ◽  
Remnant Mass

AbstractAn HI survey of the Large Magellanic Cloud (LMC) has been reanalyzed to find the transverse velocity of the LMC, and derive an upper limit of 4.5 × 1011M⊙for the mass of our Galaxy out to 50 kpc. A rotation curve is derived for the LMC from the HI data giving a best mass estimate of (4.0±0.4)×109M⊙. Velocity observations of 97 planetary nebulae (PN) in the Large Cloud are used to compare the old and young components. Our results are found to be at odds with an earlier sample of 9 old clusters, which is interpreted as being due to the low number of objects in that sample. The w-component of velocity dispersion of the PN population is 35 km s-1and that of the HI 10 km s-1. If this difference is a result of stellar diffusion then the average age of the PN population is 1.3 × 109yr, implying a precursor mass of 1.8 M⊙and a remnant mass of 0.63 M⊙.

scholarly journals Challenges for an axion explanation of the muon g − 2 measurement

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Manuel A. Buen-Abad ◽  
JiJi Fan ◽  
Matthew Reece ◽  
Chen Sun
Keyword(s):  
Decay Constant ◽  
Standard Model Prediction ◽  
New Physics ◽  
Effective Theory ◽  
General Sense ◽  
Weak Scale ◽  
Initial Application ◽  
The Standard Model ◽  
Axion Decay Constant ◽  
Axion Decay

Abstract The discrepancy between the muon g − 2 measurement and the Standard Model prediction points to new physics around or below the weak scale. It is tantalizing to consider the loop effects of a heavy axion (in the general sense, also known as an axion-like particle) coupling to leptons and photons as an explanation for this discrepancy. We provide an updated analysis of the necessary couplings, including two-loop contributions, and find that the new physics operators point to an axion decay constant on the order of 10s of GeV. This poses major problems for such an explanation, as the axion couplings to leptons and photons must be generated at low scales. We outline some possibilities for how such couplings can arise, and find that these scenarios predict new charged matter at or below the weak scale and new scalars can mix with the Higgs boson, raising numerous phenomenological challenges. These scenarios also all predict additional contributions to the muon g−2 itself, calling the initial application of the axion effective theory into question. We conclude that there is little reason to favor an axion explanation of the muon g – 2 measurement relative to other models postulating new weak-scale matter.

scholarly journals Upper Limit to the Distance to the Large Magellanic Cloud

1998 ◽  
Vol 494 (1) ◽  
pp. 118-124 ◽  
Author(s):  
Andrew Gould ◽  
Osamu Uza
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Upper Limit

Axions from heterotic stringThis paper was presented at the Theory CANADA 4 conference, held at Centre de recherches mathématiques, Montréal, Québec, Canada on 4–7 June 2008.

2009 ◽  
Vol 87 (3) ◽  
pp. 267-270
Author(s):  
Keshav Dasgupta ◽  
Hassan Firouzjahi ◽  
Rhiannon Gwyn
Keyword(s):  
String Theory ◽  
Decay Constant ◽  
Mass Scale ◽  
Heterotic String ◽  
Explicit Model ◽  
Heterotic String Theory ◽  
Natural Mechanism ◽  
Axion Decay Constant ◽  
Axion Decay

We study the axion in a warped heterotic background. It is shown that the axion decay constant, fa, is sensitive to the warped mass scale of the throat. As an explicit model, we construct a novel AdS-like geometry in heterotic string theory. We demonstrate that in this background fa is given by the mass scale of the longest throat in the compactification. The question of obtaining fa within the required bound 109–1012 GeV is reduced to the construction of a throat inside the heterotic string theory compactification with warped mass scale in the above range. This provides a natural mechanism for realising the axion in heterotic string theory.

scholarly journals The stochastic axiverse

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Mario Reig
Keyword(s):  
Black Hole ◽  
Dark Energy ◽  
Decay Constant ◽  
Planck Scale ◽  
Potential Minimum ◽  
Long Period ◽  
Cmb Polarization ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
Fundamental Requirement

Abstract In addition to spectacular signatures such as black hole superradiance and the rotation of CMB polarization, the plenitude of axions appearing in the string axiverse may have potentially dangerous implications. An example is the cosmological overproduction of relic axions and moduli by the misalignment mechanism, more pronounced in regions where the signals mentioned above may be observable, that is for large axion decay constant. In this work, we study the minimal requirements to soften this problem and show that the fundamental requirement is a long period of low-scale inflation. However, in this case, if the inflationary Hubble scale is lower than around O(100) eV, no relic DM axion is produced in the early Universe. Cosmological production of some axions may be activated, via the misalignment mechanism, if their potential minimum changes between inflation and today. As a particular example, we study in detail how the maximal-misalignment mechanism dilutes the effect of dangerous axions and allows the production of axion DM in a controlled way. In this case, the potential of the axion that realises the mechanism shifts by a factor ∆θ = π between the inflationary epoch and today, and the axion starts to oscillate from the top of its potential. We also show that axions with masses ma ∼ O(1 − 100) H0 realising the maximal-misalignment mechanism generically behave as dark energy with a decay constant that can take values well below the Planck scale, avoiding problems associated to super-Planckian scales. Finally, we briefly study the basic phenomenological implications of the mechanism and comment on the compatibility of this type of maximally-misaligned quintessence with the swampland criteria.

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