arXiv subjects

Kei-Jiro Takahashi

Publications and source records attributed to Kei-Jiro Takahashi.

3 recordsLinked to original sources

arXiv2008

Type IIA orientifolds and orbifolds on non-factorizable tori

We investigate Type II orientifolds on non-factorizable torus with and without its oribifolding. We explicitly calculate the Ramond-Ramond tadpole from string one-loop amplitudes, and confirm that the consistent number of orientifold planes is directly derived from the Lefschetz fixed point theorem. We furthermore classify orientifolds on non-factorizable Z_N x Z_M orbifolds, and construct new supersymmetric Type IIA orientifold models on them.

hep-th↗

arXiv2008

Three-Family Models from a Heterotic Orbifold on the E_6 Root Lattice

We classify N=1 orbifolds on the E_6 root lattice and investigate explicit model constructions on the Z_3xZ_3 orbifold in heterotic string theory. Interestingly some of the twisted sectors from the Z_3xZ_3 orbifold on the E_6 root lattice have just three fixed tori respectively, and generate three degenerate massless states. We also found three point functions with flavor mixing terms. We assume only non-standard gauge embeddings and find that they lead to three-family SU(5) and SO(10) GUT-like models. These models also include strongly coupled sectors in the low energy and messenger states charged with both hidden and visible sectors.

hep-th↗

arXiv2007

Heterotic orbifold models on Lie lattice with discrete torsion

We provide a new class of Z_N x Z_M heterotic orbifolds on non-factorisable tori, whose boundary conditions are defined by Lie lattices. Generally, point groups of these orbifolds are generated by Weyl reflections and outer automorphisms of the lattices. We classify abelian orbifolds with and without discrete torsion. Then we find that some of these models have smaller Euler numbers than those of models on factorisable tori T^2 x T^2 x T^2. There is a possibility that these orbifolds provide smaller generation numbers of N=1 chiral matter fields than factorisable models.

hep-th↗