6,300 research outputs found
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
The -Center Problem in Tree Networks Revisited
We present two improved algorithms for weighted discrete -center problem
for tree networks with vertices. One of our proposed algorithms runs in
time. For all values of , our algorithm
thus runs as fast as or faster than the most efficient time
algorithm obtained by applying Cole's speed-up technique [cole1987] to the
algorithm due to Megiddo and Tamir [megiddo1983], which has remained
unchallenged for nearly 30 years. Our other algorithm, which is more practical,
runs in time, and when it is
faster than Megiddo and Tamir's time algorithm
[megiddo1983]
Observability of hydrogen-rich exospheres in Earth-like exoplanets
(Abridged) The existence of an extended neutral hydrogen exosphere around
small planets can be used as an evidence for the presence of water in their
lower atmosphere but, to date, such feature has not been securely detected in
rocky exoplanets. Planetary exospheres can be observed using transit
spectroscopy of the Lyman- line, which is limited mainly by
interstellar medium absorption in the core of the line, and airglow
contamination from the geocorona when using low-orbit space telescopes. Our
objective is to assess the detectability of the neutral hydrogen exosphere of
an Earth-like planet transiting a nearby M dwarf using Lyman-
spectroscopy and provide the necessary strategies to inform future
observations. The spatial distribution in the upper atmosphere is provided by
an empirical model of the geocorona, and we assume a velocity distribution
based on radiative pressure as the main driver in shaping the exosphere. We
compute the excess absorption in the stellar Lyman- line while in
transit, and use realistic estimates of the uncertainties involved in
observations to determine the observability of the signal. We found that the
signal in Lyman- of the exosphere of an Earth-like exoplanet transiting
M dwarfs with radii between 0.1 and 0.6 R produces an excess absorption
between 50 and 600 ppm. The Lyman- flux of stars decays exponentially
with distance because of interstellar medium absorption, which is the main
observability limitation. Other limits are related to the stellar radial
velocity and instrumental setup. The excess absorption in Lyman- is
observable using LUVOIR/LUMOS in M dwarfs up to a distance of 15 pc. The
analysis of noise-injected data suggests that it would be possible to detect
the exosphere of an Earth-like planet transiting TRAPPIST-1 within 20 transits.Comment: 12 pages, 13 figures, accepted for publication in Astronomy &
Astrophysic
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