Asymptotically Free Natural SUSY Twin Higgs

Twin Higgs (TH) models explain the absence of new colored particles responsible for natural electroweak symmetry breaking (EWSB). All known ultraviolet completions of TH models require some non-perturbative dynamics below the Planck scale. We propose a supersymmetric model in which the TH mechanism is introduced by a new asymptotically free gauge interaction. The model features natural EWSB for squarks and gluino heavier than 2 TeV even if supersymmetry breaking is mediated around the Planck scale, and has interesting flavor phenomenology including the top quark decay into the Higgs and the up quark which may be discovered at the LHC.Comment: 5 pages, 3 figure

Unified Model of Chaotic Inflation and Dynamical Supersymmetry Breaking

The large hierarchy between the Planck scale and the weak scale can be explained by the dynamical breaking of supersymmetry in strongly coupled gauge theories. Similarly, the hierarchy between the Planck scale and the energy scale of inflation may also originate from strong dynamics, which dynamically generate the inflaton potential. We present a model of the hidden sector which unifies these two ideas, i.e., in which the scales of inflation and supersymmetry breaking are provided by the dynamics of the same gauge group. The resultant inflation model is chaotic inflation with a fractional power-law potential in accord with the upper bound on the tensor-to-scalar ratio. The supersymmetry breaking scale can be much smaller than the inflation scale, so that the solution to the large hierarchy problem of the weak scale remains intact. As an intrinsic feature of our model, we find that the sgoldstino, which might disturb the inflationary dynamics, is automatically stabilized during inflation by dynamically generated corrections in the strongly coupled sector. This renders our model a field-theoretical realization of what is sometimes referred to as sgoldstino-less inflation.Comment: 6 pages, 1 figur

Supersymmetric D-term Twin Higgs

We propose a new type of supersymmetric Twin Higgs model where the SU(4) invariant quartic term is provided by a D-term potential of a new U(1) gauge symmetry. In the model the 125 GeV Higgs mass can be obtained for stop masses below 1 TeV, and a tuning required to obtain the correct electroweak scale can be as low as 20 %. A stop mass of about 2 TeV is also possible with tuning of order O(10) %.Comment: 27 pages, 5 figures; v2: appendix extended, matches version published in JHE

QCD axion dark matter from long-lived domain walls during matter domination

The domain wall problem of the Peccei-Quinn mechanism can be solved if the Peccei-Quinn symmetry is explicitly broken by a small amount. Domain walls decay into axions, which may account for dark matter of the universe. This scheme is however strongly constrained by overproduction of axions unless the phase of the explicit breaking term is tuned. We investigate the case where the universe is matter-dominated around the temperature of the MeV scale and domain walls decay during this matter dominated epoch. We show how the viable parameter space is expanded.Comment: 13 pages, 2 figure

Minimal Non-Abelian Supersymmetric Twin Higgs

We propose a minimal supersymmetric Twin Higgs model that can accommodate tuning of the electroweak scale for heavy stops better than 10% with high mediation scales of supersymmetry breaking. A crucial ingredient of this model is a new SU(2)_X gauge symmetry which provides a D-term potential that generates a large SU(4) invariant coupling for the Higgs sector and only small set of particles charged under SU(2)_X, which allows the model to be perturbative around the Planck scale. The new gauge interaction drives the top yukawa coupling small at higher energy scales, which also reduces the tuning.Comment: 24 pages, 7 figures, matched to the published versio

Thermalization after/during Reheating

If reheating of the Universe takes place via Planck-suppressed decay, it seems that the thermalization of produced particles might be delayed, since they have large energy/small number densities and number violating large angle scatterings which decrease the momentum of particles by large amount are inefficient correspondingly. In this paper, we study the thermalization of such "under occupied" decay products in detail, following recent developments in understanding the thermalization of non-abelian plasma. Contrary to the above naive expectation, it is shown that in most cases thermalization after/during reheating occurs instantaneously by properly taking account of scatterings with small angles and of particles with small momenta. In particular, the condition for instantaneous thermalization before the completion of reheating is found to be $\alpha^{8/5} \gg (m_\phi / M_{\rm pl}) (M_{\rm pl}^2 \Gamma_\phi / m_\phi^3)^{1/5}$, which is much milder than that obtained in previous works with small angle scatterings taken into account.Comment: 20 pages, 4 figures; v2: discussion on abelian gauge theory is modified; v3: published versio