Diphoton Excess as a Hidden Monopole

We provide a theory with a monopole of a strongly-interacting hidden U(1) gauge symmetry that can explain the 750-GeV diphoton excess reported by ATLAS and CMS. The excess results from the resonance of monopole, which is produced via gluon fusion and decays into two photons. In the low energy, there are only mesons and a monopole in our model because any baryons cannot be gauge invariant in terms of strongly interacting Abelian symmetry. This is advantageous of our model because there is no unwanted relics around the BBN epoch.Comment: 6 pages, 1 figur

Semi-direct Gauge Mediation in Conformal Windows of Vector-like Gauge Theories

Direct gauge mediation models using the Intriligator-Seiberg-Shih (ISS) metastable vacua suffer from the Landau pole problem of the standard model gauge couplings and the existence of R symmetry forbidding gaugino masses. These problems may be solved by using the recently proposed SUSY breaking models in a conformal window of the vector-like $SU(N_C)$ gauge theory with gauge singlets. In this paper we propose a model of gauge mediation based on the SUSY-breaking model in the conformal window, and study the dynamics for the SUSY breaking. In the model, there are massive vector-like bifundamental fields charged under both $SU(N_C)$ and the standard model gauge group, and our model can be regarded as a semi-direct gauge mediation model. The color number $N_C$ can be small to avoid the Landau pole problem, and the R symmetry is also broken under a reasonable assumption on the strong dynamics of the model. The model possesses only one free parameter, and the gaugino and sfermion masses are naturally of the same order.Comment: 21 pages, 1 figur

Relaxing a constraint on the number of messengers in a low-scale gauge mediation

We propose a mechanism for relaxing a constraint on the number of messengers in low-scale gauge mediation models. The Landau pole problem for the standard-model gauge coupling constants in the low-scale gauge mediation can be circumvented by using our mechanism. An essential ingredient is a large positive anomalous dimension of messenger fields given by a large Yukawa coupling in a conformal field theory at high energies. The positive anomalous dimension reduces the contribution of the messengers to the beta function of the standard-model gauge couplings.Comment: 22pages; v2:explanations expanded in sec.3.2, reference adde

Non-linear Evolution of Matter Power Spectrum in Modified Theory of Gravity

We present a formalism to calculate the non-linear matter power spectrum in modified gravity models that explain the late-time acceleration of the Universe without dark energy. Any successful modified gravity models should contain a mechanism to recover General Relativity (GR) on small scales in order to avoid the stringent constrains on deviations from GR at solar system scales. Based on our formalism, the quasi non-linear power spectrum in the Dvali-Gabadadze-Porratti (DGP) braneworld models and $f(R)$ gravity models are derived by taking into account the mechanism to recover GR properly. We also extrapolate our predictions to fully non-linear scales using the Parametrized Post Friedmann (PPF) framework. In $f(R)$ gravity models, the predicted non-linear power spectrum is shown to reproduce N-body results. We find that the mechanism to recover GR suppresses the difference between the modified gravity models and dark energy models with the same expansion history, but the difference remains large at weakly non-linear regime in these models. Our formalism is applicable to a wide variety of modified gravity models and it is ready to use once consistent models for modified gravity are developed.Comment: 25 pages, 8 figures, comparison to N-body simulations in DGP added, published in PR