Search

We present two new one-parameter families of scheme transformations and apply these to study the scheme dependence of the infrared zero in the beta function of an asymptotically free non-Abelian gauge theory up to four-loop order. Our results provide a further quantitative measure of this scheme dependence, showing that for moderate values of the gauge coupling and the parameter specifying the scheme transformation, this dependence is relatively mild. We also remark on a generalized multi-parameter family of rational scheme transformations. [ABSTRACT FROM AUTHOR]

Taking the recently reported nonzero rotation angle of the cosmic microwave background (CMB) linear polarization β=0.35±0.14  deg as the hint for a pseudo-Nambu-Goldstone boson quintessence dark energy (DE), we study the electroweak (EW) axion quintessence DE model where the axion mass is generated by the EW instantons. We find that the observed value of β implies a nontrivial U(1) electromagnetic anomaly coefficient (cγ), once the current constraint on the DE equation of state is also taken into account. With the aid of the hypothetical high energy structure of the model inspired by the experimentally inferred cγ, the model is shown to be able to make a prediction for the current equation of state (wDE,0) of the quintessence DE. This is expected to make our scenario distinguishable in comparison with the cosmological constant (w=-1) and testable in the future when the error in the future measurement of wDE,0 is reduced to Ϭ(1)% level (δw=Ϭ(10-2)). [ABSTRACT FROM AUTHOR]

We study an inevitable cosmological consequence in PeV-scale SUSY-breaking scenarios. We focus on the SUSY-breaking scale corresponding to the gravitino mass m3/2=100 eV-1 keV. We argue that the presence of an early matter-dominated era and the resulting entropy production are requisite for the Universe with this gravitino mass. We infer the model-independent minimum amount of the entropy production Δ by requiring that the number of dwarf satellite galaxies Nsat in the Milky Way exceed the currently observed value, i.e., Nsat≳63. This entropy production is inevitably imprinted on the primordial gravitational waves (PGWs) produced during the inflationary era. We study how the information on the value of Δ and the time of entropy production are encoded in the PGW spectrum ΩGW. If the future GW surveys observe a suppression feature in the PGW spectrum for the frequency range O(10-10) Hz≲fGW≲O(10-5) Hz, it works as a smoking gun for PeV SUSY-breaking scenarios. Even if they do not, our study can be used to rule out all such scenarios. [ABSTRACT FROM AUTHOR]

The extension of the Standard Model by assuming U(1)B-L gauge symmetry is very well motivated since it naturally explains the presence of heavy right-handed neutrinos required to account for the small active neutrino masses via the seesaw mechanism and thermal leptogenesis. Traditionally, we introduce three right-handed neutrinos to cancel the [U(1)B-L]³ anomaly. However, it suffices to introduce two heavy right-handed neutrinos for these purposes and therefore we can replace one right-handed neutrino by new chiral fermions to cancel the U(1)B-L gauge anomaly. Then, one of the chiral fermions can naturally play a role of a dark matter candidate. In this paper, we demonstrate how this framework produces a dark matter candidate which can address the so-called "core-cusp problem". As one of the small-scale problems that the Λ cold dark matter paradigm encounters, it may imply an important clue for the nature of dark matter. One of resolutions among many is hypothesizing that sub-keV fermion dark matter halos in dwarf spheroidal galaxies are in a (quasi) degenerate configuration. We show how the degenerate sub-keV fermion dark matter candidate can be nonthermally originated in our model and thus can be consistent with the Lyman-a forest observation. Thereby, the small neutrino mass, baryon asymmetry, and the sub-keV dark matter become consequences of the broken B-L gauge symmetry. [ABSTRACT FROM AUTHOR]

We present a dark sector model addressing both the Hubble tension and the core-cusp problem. The model is based on a hidden Abelian gauge symmetry group with some chiral fermions required by the anomaly cancellation conditions, producing a candidate for the decaying fermion dark matter as a solution to the Hubble tension. Moreover, the sub-keV mass regime and the thermal history of the dark sector help the dark matter candidate resolve the core-cusp problem occurring in the standard Λ cold dark matter cosmology. [ABSTRACT FROM AUTHOR]

We present a solution to the strong CP problem that relies on the horizontal gauge symmetry and CP invariance in a full theory. Similar to other Nelson-Barr-type solutions, CP violation in both the strong and weak sectors of the Standard Model (SM) is attributed to the condensation of complex scalars Φ in the model. The model is differentiated from others in that it explains the hierarchy in the quark-Higgs Yukawa coupling in the SM based on a series of sequential breakings of the horizontal SU(3)f gauge symmetry. The experimental constraint θ̅≲10-10 requires ⟨Φ⟩≲1013-1014 GeV (the vacuum expectation value of complex scalars) and λ≲10-6 (the scalar quartic coupling). We show that this small coupling is natural in the sense of 't Hooft naturalness. Compared to other Nelson-Barr-type models with a CP-breaking scale ΛCP≲108 GeV, our model is more advantageous in terms of consistency with thermal leptogenesis. [ABSTRACT FROM AUTHOR]

We investigate whether the beta function of the finite-N Gross-Neveu model, as calculated up to the four-loop level, exhibits evidence for an infrared zero. As part of our analysis, we calculate and analyze Padé approximants to this beta function and evaluate effects of scheme dependence. From our study, we find that in the range of coupling where the perturbative calculation of the four-loop beta function is reliable, it does not exhibit robust evidence for an infrared zero. [ABSTRACT FROM AUTHOR]

We present an integral formalism for constructing scheme transformations in a quantum field theory. We apply this to generate several new useful scheme transformations. A comparative analysis is given of these scheme transformations in terms of their series expansion coefficients and their resultant effect on the interaction coupling, in particular at a zero of the beta function away from the origin in coupling-constant space. [ABSTRACT FROM AUTHOR]