Effects of Relativistic Expansion on the Late-time Supernova Light Curves

The effects of relativistic expansion on the late-time supernova light curves are investigated analytically, and a correction term to the (quasi-)exponential decay is obtained by expanding the observed flux in terms of (\beta), where (\beta) is the maximum velocity of the ejecta divided by the speed of light (c). It is shown that the Doppler effect brightens the light curve owing to the delayed decay of radioactive nuclei as well as to the Lorentz boosting of the photon energies. The leading correction term is quadratic in (\beta), thus being proportional to (E_{\rm k}/(M_{\rm ej} c^2)), where (E_{\rm k}) and (M_{\rm ej}) are the kinetic energy of explosion and the ejecta mass. It is also shown that the correction term evolves as a quadratic function of time since the explosion. The relativistic effect is negligibly small at early phases, but becomes of considerable size at late phases. In particular, for supernove having a very large energy(hypernova) or exploding in a jet-like or whatever non-spherical geometry, (^{56})Ni is likely to be boosted to higher velocities and then we might see an appreciable change in flux. However, the actual size of deviation from the (quasi-)exponential decay will be uncertain, depending on other possible effects such as ionization freeze-out and contributions from other energy sources that power the light curve.Comment: 12 pages including 2 figures, submitted to ApJ

Muon g-2 anomaly and 125 GeV Higgs : Extra vector-like quark and LHC prospects

The ATLAS and CMS collaborations recently reported indication of a Higgs boson around 125 GeV. If we add extra vector-like quarks to the MSSM, such a relatively heavy Higgs can be naturally realized in the GMSB framework, simultaneously explaining the muon g-2 anomaly. I will discuss LHC prospects of this attractive model.Comment: 5 pages, 3 figures; talk given at the International Workshop on Grand Unified Theories (GUT2012), Japan, 15-17 March 201

Upper-bounding bias errors in satellite navigation

A satellite navigation system for a safety critical application is required to provide an integrity alert of any malfunction; the probability that a navigation positioning error exceeds a given alert limit without an integrity alert is required to be smaller than a given integrity risk. So far, a little number of applications provide integrity alerts, because signal propagation from a satellite to a receiver depends on diversified phenomena and makes probabilistic upper-bound of possible threats difficult. To widen application fields of satellite navigation, two methods to upper-bound wide classes of bias errors are shown in this paper. The worst bias error in a maximum likelihood estimate caused by an interference signal within a given small power is derived. A novel inequality condition with a clock bias error and magnification coefficients that upper-bounds a horizontal position error is presented. Robustness of the inequality condition is numerically shown based on actual configurations of satellites.Comment: To appear in IEEE Workshop on Statistical Signal Processing, Gold Coast, Australia, 201

Policy Options for Financing the Future Health and Long-term Care Costs in Japan (Subsequently published in "Fiscal Policy and Management in East Asia", Takatoshi Ito and Andrew Rose eds., University of Chicago Press, 2007, pp. 415-442.)

As the Japanese population structure changes, health care and long-term care costs will steadily increase. The current style of financing (pay-as-you-go) will create a large increase in future burden of these costs. This paper studies an alternative policy that prefunds the social insurance benefits for the elderly. During a transition process, the proposed scheme maintains a higher contribution rate in order to accumulate sufficient funds. Under our baseline scenario, the sum of the contribution rates toward health insurance and long-term care insurance increases from 5.06 percent of earnings to 12.41 percent of the same. The rate of increase in overall burdens, including taxes and subsidies, is 63 percent. Our sensitivity analysis has shown that the quantitative implications of the increase in total burdens depend on social cost scenarios, the labor force, and the interest rate. However, labor force scenarios do not have a considerable impact on the rate of burden. As against this, the setting of social costs has a significant impact on the same. Even under the most optimistic scenario, the rate of increase in total burden is 34 percent. Even though we cannot predict the exact amount of the necessary contribution rate that is capable enough to transfer the funded system, what we are sure of is that a significant increase in the contribution rate is inevitable.