Higgs inflation at the critical point

Higgs inflation can occur if the Standard Model (SM) is a self-consistent effective field theory up to inflationary scale. This leads to an upper bound on the top Yukawa coupling, y(t)(phys) < y(t)(crit) and thus on the mass of the top quark m(t). If m(t) is more than a few hundred of MeV below the critical value, the Higgs inflation predicts the universal values of inflationary indexes, r similar or equal to 0.003 and n(s) similar or equal to 0.97, independently on the SM parameters. We show that in the vicinity of the critical point y(t)(crit) the inflationary indexes acquire an essential dependence on m(t) and on the mass of the Higgs boson M-h. In particular, the amplitude of the gravitational waves can exceed considerably the universal value. (C) 2014 Elsevier B.V.

Standard Model Higgs boson mass from inflation

Amaury Magnin

We analyse one-loop radiative corrections to the inflationary potential in the theory, where inflation is driven by the Standard Model Higgs field. We show that inflation is possible provided the Higgs mass mH lies in the interval mmin < mH < mmax, where mmin = [136.7 + (mt - 171.2) × 1.95] GeV, mmax = [184.5 + (mt - 171.2) × 0.5] GeV and mt is the mass of the top quark. In the renormalization scheme associated with the Einstein frame the predictions of the spectral index of scalar fluctuations and of the tensor-to-scalar ratio practically do not depend on the Higgs mass within the admitted region and are equal to ns = 0.97 and r = 0.0034 correspondingly. © 2009.

2009

Composite Higgs as a Viable Scenario for Electro-Weak Symmetry Breaking

Jan Mrazek

This thesis presents a general discussion of the Composite Higgs scenario of Electro-Weak Symmetry Breaking (EWSB). We start by reviewing the Standard Model of Electro-Weak interaction, discussing its experimental tests and conceptual pitfalls. Emphasis is given to the effective field theory point of view. In particular, the inherent tension related to the stability of the Electro-Weak scale motivates us to explore the possibility of having the Higgs field emerging as a Nambu-Goldstone boson from a new strongly coupled sector. Our construction is to a large extent inspired by the picture of the long range dynamics of QCD. The main ingredients are the symmetry of the UV theory, the pattern of its spontaneous breakdown and the sources of explicit breaking. In QCD, the latter are provided by the light quark masses and by the electromagnetic interaction. In Composite Higgs models, the most relevant symmetry breaking couplings are those related to the generation of the third family quark Yukawas through partial compositeness. They generate a potential for the Higgs and thus trigger EWSB. The constraints on the scenario are exposed, with a particular emphasis on the composite Two Higgs Doublet Model (THDM). While a residual SO(4) symmetry is sufficient to ensure a realistic phenomenology in presence of a single composite Higgs doublet, an extended Higgs sector needs more symmetries. For two doublets we show how either CP or a ℤ2 symmetry can play this role and construct a model for each realisation relying on the SO(6)/SO(4) × SO(2) coset. Finally, we discuss the phenomenology of this scenario. In particular, we present de differences between an elementary and a composite THDM. We also conclude that composite fermions associated to the third family quarks seem to be the most promising experimental handles for these models. We discuss their discovery range at the LHC, and the possibility of measuring the structure of their couplings. This knowledge would allow important insight into the strong dynamics.

EPFL2011

Living beyond the edge: Higgs inflation and vacuum metastability

Javier Rubio

The measurements of the Higgs mass and top Yukawa coupling indicate that we live in a very special universe, at the edge of the absolute stability of the electroweak vacuum. If fully stable, the Standard Model (SM) can be extended all the way up to the inflationary scale and the Higgs field, nonminimally coupled to gravity with strength xi, can be responsible for inflation. We show that the successful Higgs inflation scenario can also take place if the SM vacuum is not absolutely stable. This conclusion is based on two effects that were overlooked previously. The first one is associated with the effective renormalization of the SM couplings at the energy scale M-P/xi, where M-P is the Planck scale. The second one is a symmetry restoration after inflation due to high temperature effects that leads to the (temporary) disappearance of the vacuum at Planck values of the Higgs field.

Amer Physical Soc2015

Composite Higgs as a Viable Scenario for Electro-Weak Symmetry Breaking

Jan Mrazek

EPFL2011