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Register a new userThe Selfish Higgs
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Added by
Gian Francesco Giudice
Publication date
2019
fields
Physics
and research's language is
English
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We propose a mechanism to solve the Higgs naturalness problem through a cosmological selection process. The discharging of excited field configurations through membrane nucleation leads to discrete jumps of the cosmological constant and the Higgs mass, which vary in a correlated way. The resulting multitude of universes are all empty, except for those in which the cosmological constant and the Higgs mass are both nearly vanishing. Only under these critical conditions can inflation be activated and create a non-empty universe.
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Light scalar fields that couple to matter through the Higgs portal mediate long range fifth forces. We show how the mixing of a light scalar with the Higgs field can lead to this fifth force being screened around macroscopic objects. This behaviour can only be seen by considering both scalar fields as dynamical, and is missed if the mixing between the Higgs field and the scalar field is not taken into account. We explain under which conditions the naive integrating out procedure fails, i.e. when the mass matrix of the Higgs-scalars system has a nearly vanishing mass eigenvalue. The resulting flat direction in field space can be lifted at the quadratic order in the presence of matter and the resulting fifth force mediated by the Higgs portal can be screened either when the gravitating objects are large enough or their surface Newton potential exceeds a threshold. Finally we discuss the implications of these results for nearly massless relaxion models.
We make an estimate of the likelihood function for the Higgs vacuum expectation value by imposing anthropic constraints on the existence of atoms while allowing the other parameters of the Standard Model to also be variable. We argue that the most important extra ingredients are the Yukawa couplings, and for the intrinsic distribution of Yukawa couplings we use the scale invariant distribution which is favored phenomenologically. The result is successful phenomenologically, favoring values close to the observed vev. We also discuss modifications that could change these conclusions. Our work supports the hypothesis that the anthropic constraints could be the origin of the small value of the Higgs vev.
If the electroweak Higgs vacuum expectation value $v$ in early universe is $sim 1 %$ higher than its present value $v_0=246$ GeV, the $^7$Li puzzle in BBN and the CMB/$Lambda$CDM tension with late-universe measurements on Hubble parameter are mitigated. We propose a model of an axion coupled to the Higgs field, named ``axi-Higgs, with its mass $m_a sim 10^{-30} - 10^{-29},{rm eV}$ and decay constant $f_a sim 10^{17} - 10^{18},{rm GeV}$, to achieve this goal. The axion initial value $a_{rm ini}$ yields an initial $Delta v_{rm ini}/v_0 sim 0.01$ throughout the BBN-recombination epoch and a percent level contribution to the total matter density today. Because of its very large de Broglie wavelength, this axion matter density $omega_a$ suppresses the matter power spectrum, alleviating the CMB/$Lambda$CDM $S_8/sigma_8$ tension with the weak-lensing data. It also explains the recently reported isotropic cosmic birefringence by its coupling with photons. Adding the axion ($m sim 10^{-22},$eV) in the fuzzy dark matter model to the axi-Higgs model allows bigger $Delta v_{rm rec}$ and $omega_a$ to address the Hubble and $S_8/sigma_8$ tensions simultaneously. The model predicts that $Delta v$ may be detected by the spectral measurements of quasars, while its oscillation may be observed in the atomic clock measurements.
The relic gravitational wave background due to tensor linear perturbations generated during Higgs inflation is computed. Both the Standard Model and a well-motivated phenomenological completion (that accounts for all the experimentally confirmed evidence of new physics) are considered. We focus on critical Higgs inflation, which improves on the non-critical version and features an amplification of the tensor fluctuations. The latter property allows us to establish that future space-borne interferometers, such as DECIGO, BBO and ALIA, may detect the corresponding primordial gravitational waves.
We study $R^2$-Higgs inflation in a model with two Higgs doublets. The context is the general two Higgs doublet model where the Higgs sector of the Standard Model is extended by an additional Higgs doublet. We first discuss the required inflationary dynamics in this two Higgs doublet model, which includes four scalar fields, in the covariant formalism allowing a nonminimal coupling between the Higgs-squared and the Ricci scalar $R$, as well as the $R^2$ term. We find that the parameter space favored by $R^2$-Higgs inflation requires nearly degenerate $m_mathsf{H}$, $m_A$ and $m_{mathsf{H}^pm}$, where $mathsf{H}$, $A$, and $mathsf{H}^pm$ are the extra CP even, CP odd, and charged Higgs bosons in the general two Higgs doublet model taking renormalization group evolutions of the parameters into account. Discovery of such heavy scalars at the Large Hadron Collider are possible if they are in the sub-TeV mass range. Indirect evidences may also emerge at the LHCb and Belle-II experiments, however, to probe the quasi degenerate mass spectra one would likely require future lepton colliders such as the International Linear Collider and the Future Circular Collider.
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