Self-tuning solutions of the cosmological constant

I briefly review the cosmological constant problem and attempts toward its solution, and present the first nontrivial example for the self-tuning mechanism with a $1/H^2$ term with the antisymmetric field strength $H_{MNPQ}$ in a 5D RS-II setup.Comment: Latex file of 9 pages. Talk presented at SUSY'01, Dubna, Russia, 11--17 June 200

Towards unity of families: anti-SU(7) from Z(12-I) orbifold compactification

The problem of families, "Why are there three families of fermions?", is a long awaited question to be answered within a reasonable framework. We propose anti-SU($N$) groups for the unification of families in grand unification (GUT) groups, where the separation of color and weak gauge groups in the GUT is achieved by antisymmetric tensor Brout-Englert-Higgs boson instead of an adjoint representation. Theories of anti-SU($N$)'s are proposed for the unification of families. The minimal model is found as \antiSD \, GUT with the fermion representation [3]+2[2]+8[\bar-1]. We present an example in a Z(12-I) orbifold compactification, where the missing partner mechanism is also realized.Comment: 24 page

Axionic domain wall number related to U(1)anom_{\rm anom} global symmetry

The QCD axion with $f_a$ at an intermediate scale, 10**9-10**12 GeV, seems in conflict with the gravity spoil of global symmetries and may face the axionic domain wall problem. We point out that the string compactifications with an anomalous U(1) gauge symmetry, allowing desirable chiral matter spectra, circumvent these two problems simultaneously.Comment: 8 pages, 2 figure

Is an axizilla possible for di-photon resonance?

Heavy axion-like particles, called axizillas, are simple extensions of the standard model(SM). An axizilla is required not to couple to the quarks, leptons, and Brout-Englert-Higgs doublets of the SM, but couple to the gauge anomalies of the $W^\pm, Z$ and photon. It is possible to have its branching ratios(BRs) to two photons greater than 10% and to two $Z$'s less than 10%. To have a (production cross section)$\cdot$(BR to di-photons) at a $10^{-38}\,\textrm{cm}^2$ level, a TeV scale heavy quark $Q$ is required for the gluon--quark fusion process. The decay of $Q$ to axizilla plus quark, and the subsequent decay of the axizilla to two photons can be fitted at the required level of $10^{-38}\,\textrm{cm}^2$.Comment: 9 pages of latex file with 3 figure