Public Debt and the Macroeconomic Stability of Japan

Recently, the outstanding debt of the Japanese government amounts to 695 trillion yen, which implies 139.5% of GDP. In this paper, we constructed three IS-LM type dynamic models and estimate the eigenvalues of their differential systems. Then we confirm whether or not the huge amount of public debt violates the stability conditions for the Japanese economy. Our estimation concludes the Japanese economy to be unstable with the existence of a saddle-point equilibrium. Our simulation also shows that severe tax reform would be required to restore the economic stability. Concretely, the government has to raise the consumption tax rate to 15% from 5%, and in addition, allowing the income elasticities of income taxes and inhabitant taxes to increase by 0.033 each, which is equivalent to tax hikes of about 8.3 trillion yen. We assert that structural reform for the government budget including a tax system is essential and emergent.public debt, Japan, macroeconomic stability, saddle-point equilibrium, structural reform

Broadband and energy-concentrating terahertz coherent perfect absorber based on a self-complementary metasurface

We demonstrate that a self-complementary checkerboard-like metasurface works as a broadband coherent perfect absorber (CPA) when symmetrically illuminated by two counter-propagating incident waves. A theoretical analysis based on wave interference and results of numerical simulations of the proposed metasurface are provided. In addition, we experimentally demonstrate the proposed CPA in the terahertz regime by using a time-domain spectroscopy technique. We observe that the metasurface can work as a CPA below its lowest diffraction frequency. The size of the absorptive areas of the proposed CPA can be much smaller than the incident wavelength. Unlike conventional CPAs, the presented one simultaneously achieves the broadband operation and energy concentration of electromagnetic waves at the deep-subwavelength scale.Comment: 5 pages, 4 figure

Frequency-Independent Response of Self-Complementary Checkerboard Screens

This research resolves a long-standing problem on the electromagnetic response of self-complementary metallic screens with checkerboardlike geometry. Although Babinet's principle implies that they show a frequency-independent response, this unusual characteristic has not been observed yet due to the singularities of the metallic point contacts in the checkerboard geometry. We overcome this difficulty by replacing the point contacts with resistive sheets. The proposed structure is prepared and characterized by terahertz time-domain spectroscopy. It is experimentally confirmed that the resistive checkerboard structures exhibit a flat transmission spectrum over 0.1--1.1 THz. It is also demonstrated that self-complementarity can eliminate even the frequency-dependent transmission characteristics of resonant metamaterials.Comment: 6 pages, 5 figures + Supplemental Material (6 pages, 7 figures

Plane-wave scattering by self-complementary metasurfaces in terms of electromagnetic duality and Babinet's principle

We investigate theoretically electromagnetic plane-wave scattering by self-complementary metasurfaces. By using Babinet's principle extended to metasurfaces with resistive elements, we show that the frequency-independent transmission and reflection are realized for normal incidence of a circularly polarized plane wave onto a self-complementary metasurface, even if there is diffraction. Next, we consider two special classes of self-complementary metasurfaces. We show that self-complementary metasurfaces with rotational symmetry can act as coherent perfect absorbers, and those with translational symmetry compatible with their self-complementarity can split the incident power equally, even for oblique incidences