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Register a new userUnified Interpretation of Scalegenesis in Conformally Extended Standard Models
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We present a universal interpretation for a class of conformal extended standard models including Higgs portal interactions realized in low-energy effective theories. The scale generation mechanism in this class (scalegenesis) arises along the (nearly) conformal/flat direction for the scale symmetry breaking, where the electroweak-symmetry breaking structure is achieved in a similar way to the standard models. A dynamical origin for the Higgs portal coupling can provide the discriminator for the low-energy ``universality class, to be probed in forthcoming collider experiments.
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The gravitational wave (GW) background produced at the cosmological chiral phase transition in a conformal extension of the standard model is studied. To obtain the bounce solution of coupled field equations we implement an iterative method. We find that the corresponding $O(3)$ symmetric Euclidean action $S_3$ divided by the temperature $T$ has a simple behavior near the critical temperature $T_C$: $S_3/T propto (1-T/T_C)^{-gamma}$, which is subsequently used to determine the transitions inverse duration $beta$ normalized to the Hubble parameter $H$. It turns out that $beta/H gtrsim 10^3$, implying that the sound wave period $tau_text{sw}$ as an active GW source, too, can be much shorter than the Hubble time. We therefore compute $tau_text{sw} H$ and use it as the reduction factor for the sound wave contribution. The signal-to-noise ratio (SNR) for Deci-Hertz Interferometer Gravitational Wave Observatory (DECIGO) and Big Bang Observer (BBO) is evaluated, with the result: SNR$^text{DECIGO} lesssim 1.2$ and SNR$^text{BBO} lesssim 12.0$ for five years observation, from which we conclude that the GW signal predicted by the model in the optimistic case could be detected at BBO.
We review the gauge hierarchy problem in the standard model. We discuss the meaning of the quadratic divergence in terms of the Wilsonian renormalization group. Classical scale symmetry, which prohibits dimensionful parameters in the bare action, could play a key role for the understanding of the origin of the electroweak scale. We discuss the scale-generation mechanism, i.e. scalegenesis in scale invariant theories. In this paper, we introduce a scale invariant extension of the SM based on a strongly interacting scalar-gauge theory. It is discussed that asymptotically safe quantum gravity provides a hint about solutions to the gauge hierarchy problem.
The tremendous phenomenological success of the Standard Model (SM) suggests that its flavor structure and gauge interactions may not be arbitrary but should have a fundamental first-principle explanation. In this work, we explore how the basic distinctive properties of the SM dynamically emerge from a unified New Physics framework tying together both flavour physics and Grand Unified Theory (GUT) concepts. This framework is suggested by the gauge Left-Right-Color-Family Grand Unification under the exceptional $mathrm{E}_8$ symmetry that, via an orbifolding mechanism, yields a supersymmetric chiral GUT containing the SM. Among the most appealing emergent properties of this theory is the Higgs-matter unification with a highly-constrained massless chiral sector featuring two universal Yukawa couplings close to the GUT scale. At the electroweak scale, the minimal SM-like effective field theory limit of this GUT represents a specific flavored three-Higgs doublet model consistent with the observed large hierarchies in the quark mass spectra and mixing already at tree level.
We investigate the general group structure of gauge-Higgs unified models. We find that a given embedding of the sm gauge group will imply the presence of additional light vectors, except for a small set of special cases, which we determine; the arguments presented are independent of the compactification scheme. For this set of models we then find those that can both accommodate quarks and have a vanishing oblique T-parameter at tree-level. We show that none of the resulting models can have $|sw| sim1/2 $ (the sine of the weak-mixing angle) at tree-level and briefly discuss possible solutions to this problem.
We revisit a recently proposed scale invariant extension of the standard model, in which the scalar bi-linear condensate in a strongly interacting hidden sector dynamically breaks scale symmetry, thereby triggering electroweak symmetry breaking. Relaxing the previously made assumption on $U(N_f)$ flavor symmetry we find that the presence of the would-be dark matter candidate opens a new annihilation process of dark matter at finite temperature, such that the model can satisfy stringent constraints of the future experiments of the dark matter direct detection.
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