Flavor structure and coupling selection rule from intersecting D-branes

We study flavor structure and the coupling selection rule in intersecting D-brane configurations. We formulate the selection rule for Yukawa couplings and its extensions to generic n-point couplings. We investigate the possible flavor structure, which can appear from intersecting D-brane configuration, and it is found that their couplings are determined by discrete abelian symmetry. Our studies on the flavor structure and the coupling selection rule show that the minimal matter content of the supersymmetric standard model would have difficulty to derive realistic Yukawa matrices from stringy 3-point couplings at the tree-level. However, extended models have a richer structure, leading to non-trivial mass matrices.Comment: 28 pages, latex, 5 figure

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.Comment: 24 pages, 5 figures; v2: a few errors on tables are corrected, typos corrected, version to appear in JHE

Functional mutations in spike glycoprotein of Zaire ebolavirus associated with an increase in infection efficiency

Ebola virus (EBOV) is extremely virulent, and its glycoprotein is necessary for viral entry. EBOV may adapt to its new host humans during outbreaks by acquiring mutations especially in glycoprotein, which allows EBOV to spread more efficiently. To identify these evolutionary selected mutations and examine their effects on viral infectivity, we used experimental–phylogenetic–structural interdisciplinary approaches. In evolutionary analysis of all available Zaire ebolavirus glycoprotein sequences, we detected two codon sites under positive selection, which are located near/within the region critical for the host‐viral membrane fusion, namely alanine‐to‐valine and threonine‐to‐isoleucine mutations at 82 (A82V) and 544 (T544I), respectively. The fine‐scale transmission dynamics of EBOV Makona variants that caused the 2014–2015 outbreak showed that A82V mutant was fixed in the population, whereas T544I was not. Furthermore, pseudotype assays for the Makona glycoprotein showed that the A82V mutation caused a small increase in viral infectivity compared with the T544I mutation. These findings suggest that mutation fixation in EBOV glycoprotein may be associated with their increased infectivity levels; the mutant with a moderate increase in infectivity will fix. Our findings showed that a driving force for Ebola virus evolution via glycoprotein may be a balance between costs and benefits of its virulence

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.Comment: 42 pages, 3 figures, v2: typos corrected, references added, version to appear in Nucl. Phys.

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京都大学0048新制・課程博士博士(理学)甲第13580号理博第3238号新制||理||1478(附属図書館)UT51-2008-C498京都大学大学院理学研究科物理学・宇宙物理学専攻(主査)准教授 小林 達夫, 教授 川合 光, 教授 畑 浩之学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDA