Universally Leptophilic Dark Matter From Non-Abelian Discrete Symmetry

The positron anomaly recently reported by the cosmic-ray measurements can be explained by the decaying dark matter scenario, where it decays mainly into leptons with the lifetime of O(10^26) second. When the dark matter is a fermionic particle, the lifetime of this order is known to be obtained by a dimension 6 operator suppressed by the unification scale 10^16 GeV, while such decay operators do not necessarily involve only leptons. In addition, the scenario would be spoiled if there exist lower-dimensional operators inducing the dark matter decay. We show in this letter that a single non-Abelian discrete symmetry such as A_4 is possible to prohibit all such harmful (non-leptonically coupled and lower-dimensional) operators. Moreover, the dark matter decays into charged leptons in a flavor-blind fashion due to the non-Abelian flavor symmetry, which results in perfect agreements not only with the PAMELA data but also with the latest Fermi-LAT data reported very recently. We also discuss some relevance between the discrete symmetry and neutrino physics.Comment: 13 pages, 2 tables, 1 figur

Lefschetz fibrations with small slope

We construct Lefschetz fibrations over $S^2$ which do not satisfy the slope inequality. This gives a negative answer to a question of Hain.Comment: 9 pages, 2 figures, Main changes are the corrections of the statement and proof of Theorem 1.5. This version correct the statements and proofs of Corollary 1.3 and 1.

Charpy absorbed energy in simulated heat-affected zone of laser-arc hybrid welded joints by high-strength steel for bridge structures

The application of laser-arc hybrid welding (so-called, hybrid welding) to the fabrication of steel bridge members has recently been investigated. One-pass full-penetration butt joints of steels for bridge high-performance structure (SBHS400 and SBHS500) with a thickness of 15 mm were performed by hybrid welding. The sound butt joints by hybrid welding were confirmed by a series of tests. The Charpy impact test was performed on the test pieces extracted from the hybrid welded butt joints with specified test temperatures. A phenomenon known as fracture path deviation (FPD) occurred in most test pieces, due to a large variation in material properties of the heat-affected zone (HAZ), resulting in the difficulty of estimating the toughness of HAZ in hybrid welded joints. Therefore, the Charpy impact test was conducted on the test pieces subjected to the welding thermal cycle tests of hybrid welding, which can exclude the heterogeneity of material properties and obtain the Charpy absorbed energy of the HAZ with high accuracy. The test results indicated that FPD was not observed in all thermal cycle simulated test pieces because the uniform metallographic structures in the vicinity of the notch were formed by the simulated thermal cycle tests, and all thermal cycle simulated test pieces satisfied 47 J at the specified test temperatures, a value that prevents brittle fracture for SBHS. Besides, for investigating the effect of the high Charpy absorbed energy guaranteed by SBHS on the toughness of hybrid welded joints, the Charpy absorbed energy of the thermal cycle simulated test pieces of SBHS and those of conventional steel (SM400B) were compared. The results showed that some of the thermal cycle simulated test pieces of SM400B failed to satisfy 27 J, suggesting that SBHS may ensure a Charpy absorbed energy of 47 J or more in the HAZ of hybrid welded joints.Chen G., Hirohata M., Sakai N., et al. Charpy absorbed energy in simulated heat-affected zone of laser-arc hybrid welded joints by high-strength steel for bridge structures. International Journal of Advanced Manufacturing Technology 127, 2655 (2023); https://doi.org/10.1007/s00170-023-11420-2

Effective theoretical approach of Gauge-Higgs unification model and its phenomenological applications

We derive the low energy effective theory of Gauge-Higgs unification (GHU) models in the usual four dimensional framework. We find that the theories are described by only the zero-modes with a particular renormalization condition in which essential informations about GHU models are included. We call this condition ``Gauge-Higgs condition'' in this letter. In other wards, we can describe the low energy theory as the SM with this condition if GHU is a model as the UV completion of the Standard Model. This approach will be a powerful tool to construct realistic models for GHU and to investigate their low energy phenomena.Comment: 18 pages, 2 figures; Two paragraphs discussing the applicable scope of this approach are adde