Louis Yang

Postinflationary higgs relaxation and the origin of matter-antimatter asymmetry

The recent measurement of the Higgs boson mass implies a relatively slow rise of the standard model Higgs potential at large scales, and a possible second minimum at even larger scales. Consequently, the Higgs field may develop a large vacuum expectation value during inflation. The relaxation of the Higgs field from its large postinflationary value to the minimum of the effective potential represents an important stage in the evolution of the Universe. During this epoch, the time-dependent Higgs condensate can create an effective chemical potential for the lepton number, leading to a generation of the lepton asymmetry in the presence of some large right-handed Majorana neutrino masses. The electroweak sphalerons redistribute this asymmetry between leptons and baryons. This Higgs relaxation leptogenesis can explain the observed matter-antimatter asymmetry of the Universe even if the standard model is valid up to the scale of inflation, and any new physics is suppressed by that high scale.

Observational constraints on exponential gravity

We study the observational constraints on the exponential gravity model of f(R)=-{beta}R{sub s}(1-e{sup -R/R}{sub s}). We use the latest observational data including Supernova Cosmology Project Union2 compilation, Two-Degree Field Galaxy Redshift Survey, Sloan Digital Sky Survey Data Release 7, and Seven-Year Wilkinson Microwave Anisotropy Probe in our analysis. From these observations, we obtain a lower bound on the model parameter {beta} at 1.27 (95% C.L.) but no appreciable upper bound. The constraint on the present matter density parameter is 0.245<{Omega}{sub m}{sup 0}<0.311 (95% C.L.). We also find out the best-fit value of model parameters on several cases.

Leptogenesis via neutrino production during Higgs condensate relaxation

© 2015 American Physical Society. During inflation, scalar fields, including the Higgs boson, may acquire a nonzero vacuum expectation value, which must later relax to the equilibrium value during reheating. In the presence of the time-dependent condensate, the vacuum state can evolve into a state with a nonzero particle number. We show that, in the presence of lepton-number violation in the neutrino sector, the particle production can explain the observed matter-antimatter asymmetry of the Universe. We find that this form of leptogenesis is particularly effective when the Higgs condensate decays rapidly and at low reheat scale. As part of the calculation, we present some exact results for the Bogoliubov transformations for Majorana fermions with a nonzero time-dependent chemical potential, in addition to a time-dependent mass.

Singularity Phenomena in Viable f(R) Gravity

The curvature singularity in viable f(R) gravity models is examined when the background density is dense. This singularity could be eliminated by adding the

HELICAL MAGNETIC FIELDS IN THE NGC 1333 IRAS 4A PROTOSTELLAR OUTFLOWS

R^{2}

Leptogenesis via Higgs condensate relaxation

term in the Lagrangian. Some of cosmological consequences, in particular the source for the scalar mode of gravitational waves, are discussed.

Leptogenesis via the 750 GeV pseudoscalar

We present Submillimeter Array (SMA) polarization observations of the CO

Baryogenesis via elementary Goldstone Higgs relaxation

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Relaxation leptogenesis, isocurvature perturbations, and the cosmic infrared background

= 3--2 line toward the NGC1333 IRAS 4A. The CO Stokes

Big Bang Nucleosynthesis Constraint on Baryonic Isocurvature Perturbations

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