The cosmological evolution of the nucleon mass and the electroweak coupling constants

Abstract

Starting from astrophysical indications that the fine structure constant might undergo a small cosmological time shift, we discuss the implications of such an effect from the point of view of particle physics. Grand unification implies small time shifts for the nucleon mass, the magnetic moment of the nucleon and the weak coupling constant as well. The relative change of the nucleon mass is about 40 times larger than the relative change of α. Laboratory measurements using very advanced methods in quantum optics might soon reveal small time shifts of the nucleon mass, the magnetic moment of the nucleon and the fine structure constant.

Testing the time-invariance of fundamental constants using microwave spectroscopy on cold diatomic radicals

“…Due to its large vapor pressure and small polarisability, it is straightforward to produce an intense beam of CO molecules. Using pulsed laser light around 206 or 199 nm, the spin forbidden a 3 …”

“…Possible variations can be detected from a wide variety of physical phenomena, but the extreme accuracy that can be obtained in the determination of frequencies or wavelengths of spectral lines in atoms and molecules makes spectroscopy the ideal testing ground for searches of varying a and m. 2 The proton-electron mass ratio is of particular interest as theoretical models predict that the variation of m could be significantly larger than the variation of a. Calmet and Fritsch, for instance, predict that the variation of m is 38 times larger than the variation of a. 3 Recent astrophysical data suggest that the fine structure constant, a, has increased over cosmological time. The combined analysis over more than 100 quasar systems has produced a value of a relative change of Da/a ¼ À0.57 AE 0.10 Â 10 À5 , which is at the 5s significance level.…”

Time-varying coupling strengths, nuclear forces and unification

“…The relation between a time-varying fine structure constant and other observables in particle physics was also treated in [11,12,13]. In [11] the resulting variation in the vacuum energy V 0 was estimated from general principles of QFT and found to be enormously larger than the cosmological bounds; hence, the authors concluded that a large number of implausibly accurate fine-tunings would be necessary for a time variation of the size that has been claimed to be consistent with field theory and cosmology.…”

“…Calmet and Fritszch [12] calculate some of the consequences for low-energy physics of changing α, within a GUT-like theory which constrains the SM gauge couplings to be equal at a particular energy scale (or at least to satisfy some fixed relation). They consider exclusively the effects on the strong interactions, with the unstated assumption that the mechanisms of electroweak symmetry-breaking, supersymmetry-breaking and fermion mass generation are held constant despite varying the unified coupling, hence that the quark and lepton masses, as well as W and Z masses, remain unchanged.…”

“…The constraints from the dinucleon system will in general apply to a different combination of theory parameters from those arising from nucleosynthesis -taking the two together bounds the variation of fundamental parameters in two directions. (In addition, there are many other observational bounds applying at various much later epochs, discussed for example in [12], including some from direct laboratory measurement.) We also point out for the first time and estimate the effect of changing the deuteron binding energy on the process of helium formation at nucleosynthesis, which may give rise to stronger bounds.…”