Flavor structure in D-brane models: Majorana neutrino masses

We study the flavor structure in intersecting D-brane models. We study anomalies of the discrete flavor symmetries. We analyze the Majorana neutrino masses, which can be generated by D-brane instanton effects. It is found that a certain pattern of mass matrix is obtained and the cyclic permutation symmetry remains unbroken. As a result, trimaximal mixing matrix can be realized if Dirac neutrino mass and charged lepton mass matrices are diagonal.Comment: 17 pages, 1 figur

Standard Model-like D-brane models and gauge couplings

We systematically search intersecting D-brane models, which just realize the Standard Model chiral matter contents and gauge symmetry. We construct new classes of non-supersymmetric Standard Model-like models. We also study gauge coupling constants of these models. The tree level gauge coupling is a function of compactification moduli, string scale, string coupling and winding number of D-branes. By tuning them, we examine whether the models can explain the experimental values of gauge couplings. As a result, we find that the string scale should be greater than $10^{14-15}$GeV if the compactification scale and the string scale are the same order.Comment: 25 pgaes, 12 figures: v2 appendix adde

Modular symmetry in magnetized/intersecting D-brane models

We study the modular symmetry in four-dimensional low-energy effective field theory, which is derived from type IIB magnetized D-brane models and type IIA intersecting D-brane models. We analyze modular symmetric behaviors of perturbative terms and non-perturbative terms induced by D-brane instanton effects. Anomalies are also investigated and such an analysis on anomalies suggests corrections in effective field theory.Comment: 18 page

Poly-instanton axion inflation

We investigate the axion inflation model derived by poly-instanton effects in type II superstring theories. Poly-instanton effects are instanton effects corrected by another instanton and it can generate the modulus-axion potential with the double exponential function. Although the axion has a period of small value, this potential can have a flat region because its derivatives are exponentially suppressed by non-perturbative effects. From the view point of the cosmic inflation, such potential is interesting. In this paper, we numerically study the possibilities for realizing the cosmic inflation. We also study their spectral index and other cosmological observables, numerically.Comment: 13 pages, 2 figure

Summary of Dissertation Recitals: Three Programs of Choral Music

These three dissertation recitals consist of choral music from varied countries, genres, styles, and periods spanning from 1615 to 2011. The three recitals also represent my work with ensembles of wide‐ranging abilities and skill sets: a mixed‐voice university chorus of music majors and non‐majors, a professional septet, a mixed‐voice chorus of only non‐music majors, and a larger chorus with orchestra. The first recital, "A Celebration of Life," was presented on November 15, 2019 at University Presbyterian Church in Rochester Hills, Michigan, with the Oakland University Chorus for whom I served as interim director for the fall 2019 term. The works included Andrew Balfour’s Ambe, an arrangement of Ralph Vaughan Williams’s Silent Noon, Ruth Moody’s Parting Glass, Richard Dering’s Ave Virgo gloriosa, Benjamin Britten’s The Evening Primrose, Eric Barnum’s Afternoon on a Hill, H.T. Burleigh’s Deep River, Kristin Kuster’s Home, excerpted movements from Maurice Duruflé’s Requiem, Alice Parker’s Bright Morning Stars, and Shawn Kirchner’s Unclouded Day. The second recital, "in angustiis…," was presented on January 31, 2020, at Bethlehem United Church of Christ in Ann Arbor, Michigan with an ad hoc chorus of forty‐four singers, four vocal soloists, and an orchestra of twenty‐five instrumentalists. The works included Francis Poulenc’s Un soir de neige and Joseph Haydn’s Missa in angustiis, also known as his Lord Nelson Mass. The third recital is a compilation of performances with University of Michigan Orpheus Singers, on three separate occasions (February 20, 2020; November 24, 2019; and April 9, 2019), all at Stamps Auditorium in the Walgreen Drama Center; with University of Michigan Men’s Glee Club on May 15, 2019, at First Presbyterian Church of Kirkwood in St. Louis, Missouri; and with University of Michigan Arts Chorale on December 13, 2019, in Stamps Auditorium. The works featured include excerpted movements from Vincent Persichetti’s Flower Songs, Bradley Ellingboe’s Innisfree, Ralph Vaughan Williams’s Epitaph on John Jayberd of Diss, excerpted movements from Francesco Durante’s Vespro Breve, “Den Tod niemand zwingen kunnt” from J.S. Bach’s Christ lag in Todes Banden (BWV 4), and Charles Villiers Stanford’s Magnificat and Nunc Dimittis in G.AMUMusic: ConductingUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/155111/1/shoheik_1.pd

F-term Moduli Stabilization and Uplifting

We study K\"ahler moduli stabilization in IIB superstring theory. We propose a new moduli stabilization mechanism by the supersymmetry-braking chiral superfield which is coupled to K\"ahler moduli in K\"ahler potential. We also study uplifting of the Large Volume Scenario (LVS) by it. In both cases, the form of superpotential is crucial for moduli stabilization. We confirm that our uplifting mechanism does not destabilize the vacuum of the LVS drastically.Comment: 22 pages, 2 figure

Quark hierarchical structures in modular symmetric flavor models at level 6

We study modular symmetric quark flavor models without fine-tuning. Mass matrices are written in terms of modular forms, and modular forms in the vicinity of the modular fixed points become hierarchical depending on their residual charges. Thus modular symmetric flavor models in the vicinity of the modular fixed points have a possibility to describe mass hierarchies without fine-tuning. Since describing quark hierarchies without fine-tuning requires $Z_n$ residual symmetry with $n\geq 6$, we focus on $\Gamma_6$ modular symmetry in the vicinity of the cusp $\tau=i\infty$ where $Z_6$ residual symmetry remains. We use only modular forms belonging to singlet representations of $\Gamma_6$ to make our analysis simple. Consequently, viable quark flavor models are obtained without fine-tuning.Comment: 29 page