Abstract:
We consider open strings ending on a D5-brane in the pp-wave background, which is realized in the Penrose limit of $AdS_5 \times S^5$ with an $AdS_4\times S^2$ brane. A complete list of gauge invariant operators in the defect conformal field theory is constructed which is dual to the open string states.

Abstract:
We use the supergravity modes to clarify the role of the prefactor in the light-cone superstring field theory on PP-wave background. We verify some of the proposals of the recent paper hep-th/0205089 and give further evidence for the correspondence between N=4 SYM gauge theory and string theory on PP-wave. We also consider energy-preserving processes and find that they give vanishing cubic interaction Hamiltonian matrix.

Abstract:
We study string interactions among string states with arbitrary impurities in the Type IIB plane wave background using string field theory. We reproduce all string amplitudes from gauge theory by computing matrix elements of the dilatation operator in a previously proposed basis of states. A direct correspondence is found between the string field theory and gauge theory Feynman diagrams.

Abstract:
We study the string modes in the pp-wave light-cone string field theory. First, we clarify the discrepancy between the Neumann coefficients for the supergravity vertex and the zero mode of the full string one. We also repeat our previous manipulation of the prefactor for the string modes and find that the prefactor reduces to the energy difference of the cos modes minus that of the sin modes. Finally, we discuss off-shell three-string processes.

Abstract:
We use the nonabelian action of N coincident D(-1) branes in constant background fields, in the N $\to \infty$ limit, to construct noncommutative D-brane actions in an arbitrary noncommutative description and comment on tachyon condensation from this perspective.

Abstract:
We construct boundary states for the AdS_2 D-branes in AdS_3. We show that, in the semi-classical limit, the boundary states correctly reproduce geometric configurations of these branes. We use the boundary states to compute the one loop free energy of open string stretched between the branes. The result agrees precisely with the open string computation in hep-th/0106129.

Abstract:
This study was investigated to understand the in-depth features and processes of physicists' scientific inquiries. At first, research motives were investigated by interviewing six physicists who were prominent worldwide. As a result, three main types - incompleteness, discovery, and conflict - and nine subtypes of research motivation, were identified. Six additional background factors were found which might affect the design and start of research. Based on these findings, implications for teaching scientific inquiries to students were discussed.

Abstract:
We study open and closed string interactions in the Type IIB plane wave background using open+closed string field theory. We reproduce all string amplitudes from the dual N=2 Sp(N) gauge theory by computing matrix elements of the dilatation operator. A direct diagrammatic correspondence is found between string theory and gauge theory Feynman diagrams. The prefactor and Neumann matrices of open+closed string field theory are separately realized in terms of gauge theory quantities.

Abstract:
We compute string field theory Hamiltonian matrix elements and compare them with matrix elements of the dilatation operator in gauge theory. We get precise agreement between the string field theory and gauge theory computations once the correct cubic Hamiltonian matrix elements in string field theory and a particular basis of states in gauge theory are used. We proceed to compute the matrix elements of the dilatation operator to order g_2^2 in this same basis. This calculation makes a prediction for string field theory Hamiltonian matrix elements to order g_2^2, which have not yet been computed. However, our gauge theory results precisely match the results of the recent computation by Pearson et al. of the order g_2^2 Hamiltonian matrix elements of the string bit model.

Abstract:
van Dokkum and Conroy revisited the unexpectedly strong Na I lines at 8200 A found in some giant elliptical galaxies and interpreted it as evidence for unusually bottom-heavy initial mass function. Jeong et al. later found a large population of galaxies showing equally-extraordinary Na D doublet absorption lines at 5900 A (Na D excess objects: NEOs) and showed that their origins can be different for different types of galaxies. While a Na D excess seems to be related with the interstellar medium (ISM) in late-type galaxies, smooth-looking early-type NEOs show little or no dust extinction and hence no compelling sign of ISM contributions. To further test this finding, we measured the doppler components in the Na D lines. We hypothesized that ISM would have a better (albeit not definite) chance of showing a blueshift doppler departure from the bulk of the stellar population due to outflow caused by either star formation or AGN activities. Many of the late-type NEOs clearly show blueshift in their Na D lines, which is consistent with the former interpretation that the Na D excess found in them is related with star formation-caused gas outflow. On the contrary, smooth-looking early-type NEOs do not show any notable doppler component, which is also consistent with the interpretation of Jeong et al. that the Na D excess in early-type NEOs is likely not related with ISM activities but is purely stellar in origin.