Mikio Ikeda

Kyushu University, Hukuoka, Fukuoka, Japan

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Publications (2)0 Total impact

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    ABSTRACT: We give new constraints on the cosmological evolution with a decaying cosmological term from the recent observations of temperature-redshift relations. In our study, the cosmological term is assumed to be a function of the scale factor that increases toward the early universe, and the photon temperature is different from that of the standard ΛCDM model. We can obtain the parameter region derived from the CMB temperature observation.
    11/2012;
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    ABSTRACT: We investigate the cosmic thermal evolution with a vacuum energy which decays into photon at the low-redshift. We assume that the vacuum energy is a function of the scale factor that increases toward the early universe. We put on the constraints using recent observations of both type Ia supernovae (SNIa) by Union-2 compilation and the cosmic microwave background (CMB) temperature at the range of the redshift 0.01 < z < 3. From SNIa, we find that the effects of a decaying vacuum energy on the cosmic expansion rate should be very small but could be possible for z < 1.5. On the other hand, we obtain the severe constraints for parameters from the CMB temperature observations. Although the temperature can be still lower than the case of the standard cosmological model, it should only affect the thermal evolution at the early epoch.
    Advances in Astronomy 12/2011; 2012.