Abstract: The CPT symmetry, which combines Charge Conjugation, Parity, and Time Reversal, is a cornerstone of our model-building method, and its probable violation will endanger the most extended tool we presently utilize to explain physics, namely local relativistic quantum fields. However, the kaon system's conservation constraints appear to be rather severe. We will show in this paper that neutrino oscillation experiments can enhance this limit by many orders of magnitude, making them an excellent instrument for investigating the basis of our understanding of Nature. As a result, verifying CPT invariance does not evaluate a specific model, but rather the entire paradigm. Therefore, as the CPT's status in the neutrino sector, linked or not to Lorentz invariance violation, will be assessed at an unprecedented level by current and future long baseline experiments, distinguishing it from comparable experimental fingerprints coming from non-standard interactions is critical. Whether the entire paradigm or simply the conventional model of neutrinos is at jeopardy is significantly dependent on this.

Abstract: We consider the possibility that the cosmic neutrino background might have a nonthermal spectrum, and investigate its effect on cosmological parameters relative to standard A-cold dark matter (ACDM) cosmology. As a specific model, we consider a thermal y- distortion, which alters the distribution function of the neutrino background by depleting the population of low-energy neutrinos and enhancing the highenergy tail. We constrain the thermal y- parameter of the cosmic neutrino background using cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements, and place a 95%-confidence upper bound of y <= 0.043. The y- parameter increases the number of effective relativistic degrees of freedom, reducing the sound horizon radius and increasing the best-fit value for the Hubble constant H 0 . We obtain an upper bound on the Hubble constant of H 0 = 71.12 km/s/Mpc at 95% confidence, substantially reducing the tension between CMB/BAO constraints and direct measurement of the expansion rate from type-Ia supernovae. Including a spectral distortion also allows for a higher value of the spectral index of scalar fluctuations, with a best-fit of n S = 0.9720 +/- 0.0063, and a 95%-confidence upper bound of n S <= 0.9842.

Abstract: The details of the minimal cosmological standard model (MCSM) proposed in [The minimal cosmological standard model, arXiv:2403.05390.] are discussed. The model is based on the scalesymmetry and the global Peccei-Quinn (PQ) symmetry with a key assumption that the latter is broken only in the gravity sector in a scale-invariant manner. We show that the model provides a quite simple unified framework for the unknown history of the Universe from inflation to the epoch of big-bang nucleosynthesis, simultaneously addressing key puzzles of high energy theory and cosmology: (i) the origin of scales, (ii) primordial inflation, (iii) matter-antimatter asymmetry, (iv) tiny neutrino masses, (v) dark matter, and (vi) the strong CP-problem. Scale symmetry can be exact, and the Planck scale is dynamically generated. The presence of Gauss-Bonnet term may safely retain dangerous nonperturbative symmetry-breaking effects negligible, allowing a large-field trans-Planckian inflation along the PQ-field. Isocurvature perturbations of axi-Majorons are suppressed. A sizable amount of PQ-number asymmetry is generated at the end of inflation, and conserved afterward. Domain wall problem is absent due to the nonrestoration of the symmetry and the nonzero PQ-number asymmetry. Baryogenesis can be realized by either the transfer of the PQ-number asymmetry through the seesaw sector, or by resonant leptogenesis. Dark matter is purely cold axi-Majorons from the misalignment contribution with the symmetry-breaking scale of O(1012) GeV. Hot axi-Majorons from the decay of the inflaton become a natural source for a sizable amount of dark radiation. Inflationary gravitational waves have information about the mass parameters of the lightest left-handed and right-handed neutrinos, thanks to the presence of an early matterdomination era driven by the long-lived lightest right-handed neutrino species.

Abstract: In this work, we develop a model for Higgs-like composites based on two generations of right-handed neutrinos that condense. We analyze the spontaneous symmetry breaking of the theory with two explicit breakings, setting the different scales of the model and obtaining massive bosons as a result. Finally, we calculate the gravitational wave imprint left by the phase transition associated with the symmetry breaking of a generic potential dictated by the symmetries of the composites.

Abstract: In this work, we explore the flavor-changing decays H-i -> bs in a general supersymmetric scenario. In these models the flavor-changing decays arise at loop level, but-because they originate from a dimension-four operator-they do not decouple and may provide a first sign of new physics for heavy masses beyond the reach of colliders. In the framework of the minimal supersymmetric extension of the Standard Model, we find that the largest branching ratio of the lightest Higgs (H-1) is O(10(-6)) after imposing present experimental constraints, while heavy Higgs states may still present branching ratios O(10(-3)). In a more general supersymmetric scenario, where additional Higgs states may modify the Higgs mixings, the branching ratio BR(H-1 -> bs) can reach values O(10(-4)), while heavy Higgses still remain at O(10(-3)). Although these values are clearly out of reach for the LHC, a full study in a linear collider environment could be worth pursuing.