D-branes and Closed String Field Theory

We construct solitonic states in the OSp invariant string field theory, which are BRST invariant in the leading order of regularization parameter. One can show that these solitonic states describe D-branes and ghost D-branes, by calculating the scattering amplitudes.Comment: 8 pages, 2 figures, based on an invited talk presented at the international workshop "Progress of String Theory and Quantum Field Theory" (Osaka City University, December 7-10, 2007), to be published in the proceeding

Observables and Correlation Functions in OSp Invariant String Field Theory

We define BRST invariant observables in the OSp invariant closed string field theory for bosonic strings. We evaluate correlation functions of these observables and show that the S-matrix elements derived from them coincide with those of the light-cone gauge string field theory.Comment: 23 page

Light-Cone Gauge String Field Theory in Noncritical Dimensions

We study light-cone gauge string field theory in noncritical space-time dimensions. Such a theory corresponds to a string theory in a Lorentz noninvariant background. We identify the worldsheet theory for the longitudinal coordinate variables $X^\pm$ and study its properties. It is a CFT with the right value of Virasoro central charge, using which we propose a BRST invariant formulation of the worldsheet theory.Comment: 27 pages, 2 figure

Light-cone Gauge NSR Strings in Noncritical Dimensions

Light-cone gauge NSR string theory in noncritical dimensions should correspond to a string theory with a nonstandard longitudinal part. Supersymmetrizing the bosonic case [arXiv:0909.4675], we formulate a superconformal worldsheet theory for the longitudinal variables X^{\pm}, \psi^{\pm}. We show that with the transverse variables and the ghosts combined, it is possible to construct a nilpotent BRST charge.Comment: 22 pages, 1 figur

D-brane States and Annulus Amplitudes in OSp Invariant Closed String Field Theory

In the OSp invariant closed string field theory, we construct the states corresponding to parallel D-branes that are located at different points in the space-time. Using these states, we evaluate annulus amplitudes. We show that the results coincide with those of first quantized string theory.Comment: 14 pages, 3 figure

Japan's Deflation, Problems in the Financial System, and Monetary Policy

This paper offers three analyses of Japan's macroeconomic experience during the post-1990 period. First, we analyze various facets of deflation during the period, arguing that the deflation of general prices has by no means been a major factor for the stagnating economy. In contrast, the deflation of asset prices was closely related to the economic difficulty of the period. In particular, the negative shocks generated by sharp declines in asset prices in the early 1990s have been propagated and amplified by their interaction with the deterioration in the condition of the financial system. Some statistical evidence supports this view. Second, we analyze the effects of monetary policy adopted by the Bank of Japan (BOJ) to fight deflation since the late 1990s. Given that short-term interest rates were already nearly zero in the mid-1990s, policy measures have focused on creating monetary easing effects beyond those created by zero interest rates alone. We show that the zero interest rate policy, which includes a commitment to maintain a zero interest rate for a longer period than that suggested by a baseline monetary policy rule, has produced strong effects on expected future short-term interest rates and thus the entire yield curve. Third, we argue that the BOJ has successfully prevented a repetition of the 1997-98 type liquidity crisis by directing market operations at addressing the financial-sector problems. These operations have taken the form of containing risk and liquidity premiums, particularly in the money market, through proactive provision of liquidity as well as the BOJ's own risk- taking activity.

D-brane States and Disk Amplitudes in OSp Invariant Closed String Field Theory

We construct solitonic states in the OSp invariant string field theory, which are BRST invariant in the leading order of regularization parameter $\epsilon$. We calculate the disk amplitudes using these solitonic states and show that they describe D-branes and ghost D-branes.Comment: 37 pages, 8 figure

Light-cone Gauge Superstring Field Theory and Dimensional Regularization II

We propose a dimensional regularization scheme to deal with the divergences caused by colliding supercurrents inserted at the interaction points, in the light-cone gauge NSR superstring field theory. We formulate the theory in $d$ dimensions and define the amplitudes as analytic functions of $d$. With an appropriately chosen three-string interaction term and large negative $d$, the tree level amplitudes for the (NS,NS) closed strings can be recast into a BRST invariant form, using the superconformal field theory proposed in Ref.[arXiv:0911.3704]. We show that in the limit $d \to 10$ they coincide with the results of the first quantized theory. Therefore we obtain the desired results without adding any contact interaction terms to the action.Comment: 23 pages; v2: minor modifications; v3: revised argument in section 3, added appendix C, results unchanged; v4: added clarifications, two figures and a footnote; v5: minor modification