Eung Jin Chun

Axino mass in supergravity models

We analyze the mass of the axino, the fermionic superpartner of the axion, in general supergravity models incorporating a Peccei-Quinn symmetry and determine the cosmological constraints on this mass. In particular, we derive a simple criterion to identify models with an LSP axino which has a mass of O(m322ƒPQ) = O (keV) and can serve as a candidate for (warm) dark matter. We point out that such models have very special properties and in addition, the small axino mass has to be protected against radiative corrections by demanding small couplings in the Peccei-Quinn sector. Generically, we find an axino mass of order m32. Such masses are constrained by the requirement of an axino decay which occurs before the decoupling of the ordinary LSP. Especially, for a large Peccei-Quinn scale fPQ > 1011 GeV this constraint might be difficult to fulfill.

Cosmological Implications of Radiatively Generated Axion Scale

Abstract We study cosmological implications of supersymmetric axion models in which the axion scale is generated radiatively. Such models lead to the so-called thermal inflation and subsequent reheating should be constrained not to yield to a too large axion energy density at the time of nucleosynthesis. We examine how plausible it is that this nucleosynthesis constraint is satisfied for both hadronic and Dine-Fischler-Srednicki-Zhitnitskii type axion models. Baryogenesis and the possibility for raising up the cosmological upper bound on the axion scale in thermal inflation scenario are also discussed.

One loop corrected neutrino masses and mixing in supersymmetric standard model without R-parity

We provide, in the R-parity violating supersymmetric standard model, a comprehensive analysis for sneutrino minimization from the one-loop effective scalar potential, and also for one-loop renormalized neutrino masses and mixing by calculating the effective neutrino mass matrix in the weak basis. Applying our results to theories with gauge mediated supersymmetry breaking, we show how atmospheric and solar neutrino oscillations can be accommodated simultaneously in this framework. It is observed that the one-loop correction to sneutrino vacuum expectation values leads to a significant effect on the determination of the neutrino masses and mixing.

Dark matter in the Kim-Nilles mechanism

The Kim-Nilles mechanism relates the

Neutrino oscillations and R-parity violating collider signals

\mu

Supersymmetry hierarchy problems and anomalous horizontal U(1) symmetry

term with the axion scale

Quark and lepton mass matrices from horizontal U(1) symmetry

f_a

Quasi Goldstone fermion as a sterile neutrino

, leading to the axino-Higgsino-Higgs Yukawa coupling of order

Three neutrino Delta m**2 scales and singular seesaw mechanism

\mu/f_a

Mixed axion/gravitino dark matter from SUSY models with heavy axinos

. This can bring a dangerous thermal production of axinos. If the axino is stable, its mass has to be as small as