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  • Reconstruction of aether scalar tensor theory for variouscosmological scenarios
    2024, 48(4): 045105-045105-7. doi: 10.1088/1674-1137/ad2360
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    In this paper, we present several explicit reconstructions for the aether scalar tensor (AeST) theory derived from the background of the Friedmann-Lemaître-Robertson-Walker cosmological evolution. It is shown that the Einstein-Hilbert Lagrangian with a positive cosmological constant is the only Lagrangian capable of accurately replicating the exact expansion history of the Λ cold dark matter (ΛCDM) universe filled solely with dust-like matter. However, the ΛCDM-era can be produced within the framework of the AeST theory for some other fluids, including a perfect fluid with $ p=-(1/3)\rho $, multifluids, and nonisentropic perfect fluids. Moreover, we demonstrate that the ΛCDM-era can be replicated with no real matter field for the AeST theory. The cosmic evolution resulting from both the power-law and de-Sitter solutions can also be obtained.
  • Leptonic di-flavor and di-number violation processes at high energy ${{ {\boldsymbol\mu}^{\bf\pm}}{\boldsymbol\mu}^{\bf\pm}} $ colliders
    2024, 48(4): 043101-043101-17. doi: 10.1088/1674-1137/ad17b0
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    The leptonic di-flavor violation (LFV) processes $ \mu^\pm \mu^\pm \rightarrow e^\pm e^\pm $ and $ \mu^\pm \mu^\pm \rightarrow \tau^\pm \tau^\pm $ and leptonic di-number violation (LNV) processes $ \mu^\pm \mu^\pm \rightarrow W^\pm _iW^\pm _j $ ($ i,\;j=1,\;2 $) at same-sign high energy $ \mu^\pm \mu^\pm $ colliders are studied. The new physics (NP) factors that may play roles in these processes are highlighted by cataloging them into three types. Taking into account the experimental constraints, the processes at $ \mu^\pm\mu^\pm $ colliders are computed, and the results are presented properly. The results lead to the conclusion that observing the NP factors through the LFV and LNV processes at TeV-energy $ \mu^\pm\mu^\pm $ colliders has significant advantages that cannot be achieved elsewhere. Therefore, once the techniques for muon acceleration and collision are developed successfully, the option of building same-sign high energy muon colliders should be seriously considered.
  • Higgs inflation model with non-minimal coupling in hybrid Palatini approach
    2024, 48(4): 045104-045104-9. doi: 10.1088/1674-1137/ad1dcd
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    In this paper, we propose a hybrid metric Palatini approach in which the Palatini scalar curvature is non minimally coupled to the scalar field. We derive Einstein's field equations, i.e., the equations of motion of the scalar field. Furthermore, the background and perturbative parameters are obtained by means of Friedmann equations in the slow roll regime. The analysis of cosmological perturbations allowed us to obtain the main inflationary parameters, e.g., the scalar spectral index$ n_s $and tensor to scalar ratio r. From this perspective, as an application of our analysis, we consider the Higgs field with quartic potential, which plays the inflaton role, and show that predictions of Higgs hybrid inflation are in good agreement with recent observational data [Astron. Astrophys. 641, 61 (2020)].
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