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Jiro Hashiba

Publications and source records attributed to Jiro Hashiba.

5 recordsLinked to original sources
arXiv2018

Dark Energy from Eternal Pair-production of Fermions

We study a toy model in which Majorana or Dirac fermions behave as the source for a small vacuum energy in the present Universe. In the model, a self-interacting scalar boson coupled with fermions induces attractive and repulsive interactions between the fermions simultaneously. These interactions allow for the existence of a metastable state with positive energy density comprised of fermions degenerate inside a Fermi surface. The energy density of the metastable state remains constant as the Universe expands. This is because pair-productions of fermions from the vacuum continuously take place at no energy cost and keep supplying fermions uniformly to the Universe. The observed vacuum energy density $\sim 10^{-47}~\textrm{GeV}^4$ is reproduced for the fermion and scalar mass of the order $10^{-3}~\textrm{eV}$.

hep-ph↗
arXiv2000

Landau-Ginzburg Description of D-branes on ALE Spaces

We study the Landau-Ginzburg (LG) mirror theory of the non-linear sigma model on the ALE space ${\cal M}$ obtained by resolving the singularity of the orbifold ${\bf C}^2/{\bf Z}_N$. In the LG description, the data of the BPS spectrum and the lines of marginal stability are encoded in the special Lagrangian submanifolds of the mirror manifold $\hat{\cal M}$. Our LG description is quite simple as compared with the quiver gauge theory analysis near the orbifold point. Furthermore our mirror analysis can be applied to any point on the moduli space of ${\cal M}$.

hep-th↗
arXiv2000

String Junctions in B Field Background

It has been recently shown that F-theory on K3 with background B fields (NSNS and RR 2-forms) is dual to the CHL string in 8 dimensions. In this paper, we reexamine this duality in terms of string junctions in type IIB string theory. It is in particular stressed that certain 7-brane configurations produce Sp gauge groups in a novel way.

hep-th↗
arXiv1999

Geometry and N=2 Exceptional Gauge Theories

We find the Seiberg-Witten geometry for four dimensional N=2 supersymmetric E_6 gauge theories with massless fundamental hypermultiplets, by geometrically embedding them in type II string theories compactified on Calabi-Yau threefolds. The resulting geometry completely agrees with that of recent works, which are based on the technique of N=1 confining phase superpotentials. We also derive the Seiberg-Witten geometry for E_7 gauge theories with massive fundamental hypermultiplets.

hep-th↗