Masaru Nagura

MIRROR SYMMETRY OF THE K3 SURFACE

We discuss the K3 surface and the complex torus from the viewpoint of “mirror symmetry.” We calculate the periods of some K3 surface and construct a mirror map for the two-point correlation function and the prepotential. We find that there are no instanton corrections of the Yukawa coupling for K3 (also torus), which is expected from the viewpoint of algebraic geometry.

MIRROR SYMMETRY AND AN EXACT CALCULATION OF AN (N–2)-POINT CORRELATION FUNCTION ON A CALABI-YAU MANIFOLD EMBEDDED IN CPN−1

We consider an (N–2)-dimensional Calabi-Yau manifold which is defined as the zero locus of the polynomial of degree N (of the Fermat type) in CPN−1 and its mirror manifold. We introduce an (N–2)-point correlation function (generalized Yukawa coupling) and evaluate it both by solving the Picard-Fuchs equation for period integrals in the mirror manifold and by explicitly calculating the contribution of holomorphic maps of degree 1 to the Yukawa coupling in the Calabi-Yau manifold using the method of algebraic geometry. In enumerating the holomorphic curves in the general-dimensional Calabi-Yau manifolds, we extend the method of counting rational curves on the Calabi-Yau three-fold using the Shubert calculus on Gr(2, N). The agreement of the two calculations for the (N–2)-point function establishes “the mirror symmetry at the correlation function level” in the general-dimensional case.

Experimental Study on Corrosion of Ceramic Materials in Natural Convection Lithium Loop

Abstract Corrosion of candidate materials of insulating coating was investigated in natural convection lithium (Li) loop. The loop was constructed for present study and bulk specimens of Er2O3, Y2O3 and AlN were placed at several positions in the loop. The operation temperature was 400 °C in the low temperature region and 500 °C in the high temperature region. After the exposure, specimens were cleaned and the corrosion characteristics were investigated. The results indicated that the corrosion characteristics of the bulk specimens were similar to those obtained by the static test in the previous study.

EFFECT OF OXYGEN ON CORROSION OF ERBIUM OXIDE IN LITHIUM

Abstract Er2O3 is one promising material for use as an insulating coating in a liquid lithium blanket system. In this study, corrosion of bulk Er2O3 in Li with high or low O concentrations was investigated at 600°C. The tests revealed that the corrosion reaction is accelerated under high O condition and suppressed in low O concentration. From these results we assumed the corrosion reaction and tested with more precise condition. The Er2O3 bulk specimen corroded significantly in Li with more than 300 ppm O. Control of O concentration is essential for a Li blanket system with an Er2O3 coating.

MIRROR SYMMETRY ON ARBITRARY DIMENSIONAL CALABI-YAU MANIFOLD WITH A FEW MODULI

We calculate the B-model on the mirror pair of X2N−2(2, 2, …, 2, 1, 1), which is an (N−2)-dimensional Calabi-Yau manifold and has two marginal operators, i.e. h1,1(X2N−2(2, 2, …, 2, 1, 1))=2. In Ref. 1 we have discussed about mirror symmetry on XN(1, 1, …, 1) and its mirror pair. However, XN(1, 1, …, 1) had only one moduli. In this letter, we extend its methods to the case with a few moduli using toric geometry.

Tritium Release from PbLi Natural Convection Loop Under Neutron Irradiation

Abstract A PbLi thermal convection loop with the flow rate of a few centimeters per second was designed and constructed to perform an in-situ tritium release experiment in a neutron source of the YAYOI reactor of The University of Tokyo. Tritium was generated by the nuclear reaction of Li with neutrons released through a 1-mm-thick steel tube and followed the reactor power with some time lag, which was affected by the hydrogen concentration in the sweep gas. The overall permeation rate coefficients, around 10-5 m/s, were almost the same as those acquired in former works performed in static tests. Formation or reduction of a surface oxide layer on the permeation tube would affect the tritium release behavior.