On the possibility of large axion decay constants
By T. Banks, M. Dine, P. Fox, E. Gorbatov. 2003
357 citations recorded by the source corpus.
The decay constant of the QCD axion is required by observation to be small compared with the Planck scale. In theories of `natural inflation' and certain proposed anthropic solutions of the cosmological constant problem it would be interesting to obtain a large decay constant for axion-like fields from microscopic physics. String theory is the only context in which one can sensibly address this question. Here we survey a number of periodic fields in string theory in a variety of string vacua. In some examples, the decay constant can be parametrically larger than the Planck scale but the effective action then contains appreciable harmonics of order fA/Mp. As a result, these fields are no better inflaton candidates than Planck scale axions.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/4f82dfd77a6b0cc0c586cabfa2c9b18d7b48c682
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Citations in the corpus
- Phenomenology of a pseudo-scalar inflaton: naturally large nongaussianity (2011, background): “It has also been conjectured that f > Mp cannot be realized in a controlled limit of string theory [17].”
- Backreacted axion field ranges in string theory (2016, neutral): “On the other hand an analysis of possible axion periodicity lengths appears to suggest that a super-Planckian period for a fundamental string axion is not achievable, see [17] for the key original paper and [18] for the most recent analysis (while for example [19,20] study possible exceptions).”
- On Inflation in String Theory (2003, neutral): “ssible in future to find an adequate model in string theory with a simple axion-type evolution in the spirit of the axion-valley model. One may try to use various studies of axions in string theory in [70, 71, 72, 73, 74] towards cosmology of string theoretic axions and stringy axion-type inflation wi”
- An ignoble approach to large field inflation (2010, background): “The first inequality arises from the conjecture that super-Planckian decay constants do not exist in quantum gravity [4, 6].”
- Gravity Waves and Linear Inflation from Axion Monodromy (2008, background): “However, in the case of axions it has been argued that the field range contained within a single period is generally sub-Planckian in string theory [8], leading to proposals to extend the field range by combining many axions [9].”
- Perturbations in Chromo-Natural Inflation (2013, background): “It has thus far proved impossible to realize such a set-up in a UV-complete model such as string theory [7].”
- A review of axion inflation in the era of Planck (2013, background): “However, also in this case the limit appears to apply, since all known controlled string theory constructions are characterized by f < MPl [8, 9].”
- Recent Progress in the Physics of Axions and Axion-Like Particles (2020, background): “In that description, the gauge equivalence of A(p) on a p-cycle in Y , which determines the value of fa, is fixed by the couplings and scales involved in the compactification [4, 45, 46].”
- Hilltop inflation (2005, background): “(7)It is claimed [32] that f ≫ MP is unlikely in the context of string theory, at least if φ is a modulus.”
- Ultralight scalars as cosmological dark matter (2016, background): “For applications to inflation, some authors have attempted to increase F beyond the upper bound of ∼ 10(18) GeV, but this has proved difficult [25], except in models in which μ is so large that the axion is not relevant.”
- Inflation and String Theory (2014, background): “And indeed, direct searches for axions with f & Mpl in parametrically controlled string compactifications have been unsuccessful [46, 47].”
- Oscillations in the CMB from axion monodromy inflation (2009, background): “Going beyond our approximations, the model also predicts a small amount of running of the scalar spectral index, of order 10−4, from terms of higher order in the MPl/φ expansion.”
- Constraints on axion inflation from the weak gravity conjecture (2015, background): “The story here regarding decay constant alignment is reminiscent of that observed in [24] regarding the single axion case and [28] regarding the many axion one.”