Teaching English in a Korean High School : An Experiment

I would like to begin on a personal note. Since 1958, for a span of 24 years, with some interruptions, I have been deeply involved in English language education in Korea. I started as an in~tructor in the English department of Dong.A University in Pusan in 1958, and later moved to Seoul where as a Fulbright grantee I lectured at Seoul National University (College of Education), at Hankuk University of Foreign Studies, at Sunkyunkwan University, and at various other places for nearly a decade. For a number of. years, also, I represented the Fulbright Commission at conferences, seminars, workshops, - and training institutes in virtually every area of Korea. During this time I formed a lot of strong attachments and friendships in the Korean academic community. I have now returned to Korea after a six-year absence, and I know many of my former colleagues are wondering why I am teaching at an undistinguished high school in a provincial Korean city

The Landau-Ginzburg to Calabi-Yau Dictionary for D-Branes

Based on work by Orlov, we give a precise recipe for mapping between B-type D-branes in a Landau-Ginzburg orbifold model (or Gepner model) and the corresponding large-radius Calabi-Yau manifold. The D-branes in Landau-Ginzburg theories correspond to matrix factorizations and the D-branes on the Calabi-Yau manifolds are objects in the derived category. We give several examples including branes on quotient singularities associated to weighted projective spaces. We are able to confirm several conjectures and statements in the literature.Comment: 24 pages, refs added + minor correctio

Design and Overview of the Solar Cruiser Mission

Solar Cruiser is a Small Satellite Technology Demonstration Mission (TDM) of Opportunity to mature solar sail propulsion technology to enable near-term, high-priority breakthrough science missions as defined in the Solar and Space Physics Decadal Survey. Solar Cruiser will demonstrate a “sailcraft” platform with pointing control and attitude stability comparable to traditional platforms, upon which a new class of Heliophysics missions may fly instruments. It will show sailcraft operation (acceleration, navigation, station keeping, inclination change) immediately applicable to near-term missions, and show scalability of sail technologies such as the boom, membrane, deployer, reflectivity control devices for roll momentum management to enable more demanding missions, such as high inclination solar imaging. A team led by the NASA Marshall Space Flight Center is developing the Solar Cruiser with partners Ball Aerospace and Roccor (a Redwire company). Ball is responsible for procuring a Venus class microsat commercial bus from Blue Canyon Technologies, defining all necessary mission-specific modifications, and performing the Integration and Test of the Bus with the Solar Sail System to form the completed sailcraft. Ball will also procure the IRIS radio from Space Dynamics Laboratories and develop the adapter and harnessing that interfaces to the Launch Vehicle. Roccor will integrate the Solar Sail System (SSS), including the sail membrane from their Subcontractor NeXolve, the Triangular, Rollable and Collapsible (TRACTM) Boom, the LISAs (Lightweight Integrated Solar Arrays) and momentum management Reflective Control Devices (RCDs), before providing it to Ball for Integration and Test. Roccor will also build the Active Mass Translator (AMT), which moves the Sail relative to the Bus to control momentum in the pitch/yaw directions, while the RCDs provide roll control. MSFC manages the overall mission and provide the specialized solar sail attitude determination and control system (SSADCS) algorithms and software necessary to fly the sailcraft. The SSADCS software created for this mission will autonomously operate the AMT and RCDs to provide complete momentum control of the sailcraft. Bus-mounted Electric Propulsion thrusters are included to provide auxiliary momentum management, if required. Solar Cruiser will launch as a secondary payload with NASA’s Interstellar Mapping and Acceleration Probe (IMAP)in early 2025. The sailcraft will separate from the launch vehicle on a near-L1 trajectory (Sun-Earth Lagrangian Point 1; sunward of L1 along the Sun-Earth Line) and complete its primary mission in 11 months or less. During this time, Solar Cruiser will complete and fully characterize a large solar sail deployment (1,653 square meters/17,793 square feet), sail operation, station keeping in a sub-L1 halo orbit, inclination changes, and a roll demonstration. This paper provides a mission and sailcraft design overview, including objectives and planned operations of the technology demonstration mission. It presents the latest findings from technology maturation efforts, major program design reviews, and initial launch integration planning

D-branes in Toroidal Orbifolds and Mirror Symmetry

We study D-branes extended in T^2/Z_4 using the mirror description as a tensor product of minimal models. We describe branes in the mirror both as boundary states in minimal models and as matrix factorizations in the corresponding Landau-Ginzburg model. We isolate a minimal set of branes and give a geometric interpretation of these as D1-branes constrained to the orbifold fixed points. This picture is supported both by spacetime arguments and by the explicit construction of the boundary states, adapting the known results for rational boundary states in the minimal models. Similar techniques apply to a larger class of toroidal orbifolds.Comment: 30 pages, 2 figure

Matrix Factorizations and Homological Mirror Symmetry on the Torus

We consider matrix factorizations and homological mirror symmetry on the torus T^2 using a Landau-Ginzburg description. We identify the basic matrix factorizations of the Landau-Ginzburg superpotential and compute the full spectrum, taking into account the explicit dependence on bulk and boundary moduli. We verify homological mirror symmetry by comparing three-point functions in the A-model and the B-model.Comment: 41 pages, 9 figures, v2: reference added, minor corrections and clarifications, version published in JHE

Integrability of the N=2 boundary sine-Gordon model

We construct a boundary Lagrangian for the N=2 supersymmetric sine-Gordon model which preserves (B-type) supersymmetry and integrability to all orders in the bulk coupling constant g. The supersymmetry constraint is expressed in terms of matrix factorisations.Comment: LaTeX, 19 pages, no figures; v2: title changed, minor improvements, refs added, to appear in J. Phys. A: Math. Ge

BPS branes in discrete torsion orbifolds

We investigate D-branes in a Z_3xZ_3 orbifold with discrete torsion. For this class of orbifolds the only known objects which couple to twisted RR potentials have been non-BPS branes. By using more general gluing conditions we construct here a D-brane which is BPS and couples to RR potentials in the twisted and in the untwisted sectors.Comment: 20 pages, LaTe