### Abstract

New PKS 1830-211 radio frequency observations of methanol at a redshift of 0.885 82 have established the most stringent limits on changes in the proton to electron mass ratio μ to date. The observations place the limit of δμ/μ ≤ (0.0 ± 1.0) × 10^{-7} which is approximately a factor of 4 lower than the previous lowest limit at a redshift of 0.6742. This stringent limit at a look back time of roughly half the age of the Universe has profound implications for rolling scalar field cosmologies and the new physics that they require. Many of these cosmologies invoke a scalar field φ that is also coupled to the electromagnetic field causing the values of the fundamental constants, μ and the fine structure constant a to roll with time. If the lowest expected value of the coupling to μ, ζ_{μ}, is invoked, the new limit requires a limit on the dark energy equation of state parameter w such that (w + 1) ≤ 0.001 at a redshift of 0.885 82. This eliminates almost all of the expected parameter space for such cosmologies and new physics that have a coupling to the electromagnetic field. In these cases, the limit requires that w must be extremely close to -1 for the last half of the age of the universe or that the coupling of the rolling scalar field to μ and the electromagnetic field be significantly below or at the limit of its expected range. The new observations solidify the role of fundamental constants in providing probes of the possible cosmologies and new physics to explain the acceleration of the expansion of the universe.

Original language | English (US) |
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Pages (from-to) | 2576-2579 |

Number of pages | 4 |

Journal | Monthly Notices of the Royal Astronomical Society |

Volume | 431 |

Issue number | 3 |

DOIs | |

Publication status | Published - May 2013 |

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### Keywords

- Cosmological parameters
- Cosmology: theory
- Dark energy
- Early universe

### ASJC Scopus subject areas

- Space and Planetary Science
- Astronomy and Astrophysics