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Register a new userUnifying cosmological and recent time variations of fundamental couplings
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A number of positive and null results on the time variation of fundamental constants have been reported. It is difficult to judge whether or not these claims are mutually consistent, since the observable quantities depend on several parameters, namely the coupling strengths and masses of particles. The evolution of these coupling-parameters over cosmological history is also a priori unknown. A direct comparison requires a relation between the couplings. We explore several distinct scenarios based on unification of gauge couplings, providing a representative (though not exhaustive) sample of such relations. For each scenario we obtain a characteristic time dependence and discuss whether a monotonic time evolution is allowed. For all scenarios, some contradictions between different observations appear. We show how a clear observational determination of non-zero variations would test the dominant mechanism of varying couplings within unified theories.
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Scalar field dynamics may give rise to a nonzero cosmological variation of fundamental constants. Within different scenarios based on the unification of gauge couplings, the various claimed observations and bounds may be combined in order to trace or restrict the time history of the couplings and masses. If the scalar field is responsible for a dynamical dark energy or quintessence, cosmological information becomes available for its time evolution. Combining this information with the time variation of couplings, one can determine the interaction strength between the scalar and atoms, which may be observed by tests of the Weak Equivalence Principle. We compute bounds on the present rate of coupling variation from experiments testing the differential accelerations for bodies with equal mass and different composition and compare the sensitivity of various methods. In particular, we discuss two specific models of scalar evolution: crossover quintessence and growing neutrino models.
We compute the time variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine structure constant and Newtons constant) within the context of the so-called running vacuum models (RVMs) of the cosmic evolution. Recently, compelling evidence has been provided showing that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance $Lambda$CDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level $gtrsim3sigma$. Here we use such remarkable status of the RVMs to make definite predictions on the cosmic time variation of the fundamental constants. It turns out that the predicted variations are close to the present observational limits. Furthermore, we find that the time variation of the dark matter particles should be crucially involved in the total mass variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the micro and macro connection (viz. the dynamical feedback between the evolution of the cosmological parameters and the time variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS).
We point out that in models of macroscopic topological defects composed of one or more scalar fields that interact with standard-model fields via scalar-type couplings, the back-action of ambient matter on the scalar field(s) produces an environmental dependence of the fundamental constants of nature, as well as spatial variations of the fundamental constants in the vicinity of dense bodies such as Earth due to the formation of a bubble-like defect structure surrounding the dense body. In sufficiently dense environments, spontaneous symmetry breaking may be inhibited altogether for $phi^2$ interactions, potentially delaying the cosmological production of topological defects. We derive bounds on non-transient variations of the fundamental constants from torsion-pendulum experiments that search for equivalence-principle-violating forces, experiments comparing the frequencies of ground- and space-based atomic clocks, as well as ground-based clocks at different heights in the recent Tokyo Skytree experiment, and measurements comparing atomic and molecular transition frequencies in terrestrial and low-density astrophysical environments. Our results constrain the present-day mass-energy fraction of the Universe due to a network of infinite domain walls produced shortly after the BBN or CMB epochs to be $Omega_{textrm{walls},0} ll 10^{-10}$ for the symmetron model with a $phi^4$ potential and $phi^2$ interactions, improving over CMB quadrupolar temperature anisotropy bounds by at least 5 orders of magnitude. Our newly derived bounds on domain walls with $phi^2$ interactions via their effects of non-transient variations of the fundamental constants are significantly more stringent than previously reported clock- and cavity-based limits on passing domain walls via transient signatures and previous bounds from different types of non-transient signatures, under the same set of assumptions.
Very recently, the CMS collaboration has reported a search for the production for a Standard Model (SM) Higgs boson in association with a top quark pair ($t bar{t} H$) at the LHC Run-2 and a best fit $t bar{t} H$ yield of $1.5 pm 0.5$ times the SM prediction with an observed significance of $3.3 sigma$. We study a possibility of whether or not this observed deviation can be explained by anomalous Higgs Yukawa couplings with the top and the bottom quarks, along with the LHC Run-1 data for the Higgs boson properties. We find that anomalous top and bottom Yukawa couplings with about $0-20$% and $10-40$% reductions from their SM values, respectively, can simultaneously fit the recent CMS result and the LHC Run-1 data.
Inflationary scenarios motivated by the Minimal Supersymmetric Standard Model (MSSM) where five scalar fields are non-minimally coupled to gravity are considered. The potential of the model and the function of non-minimal coupling are polynomials of two Higgs doublet convolutions. We show that the use of the strong coupling approximation allows to obtain inflationary parameters in the case when a combination of the four scalar fields plays a role of inflaton. Numerical calculations show that the cosmological evolution leads to inflationary scenarios fully compatible with observational data for different values of the MSSM mixing angle $beta$.
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