Changes in consumers' behavior when a vertically integrated service is separated —The case of Japanese mobile phone services—

In this paper, I empirically examine the consumer behavior change in the case that the current vertically integrated Japanese mobile phone market was separated by employing the stated preference survey. As a hypothetical vertically separated situation, I assumed the introduction of contents compatibility and handsets compatibility among different mobile phone carriers. My analysis also assumed the introduction of mail address portability. My estimation results yield the following implications: (1) handset compatibility, contents compatibility, and mail address portability reduces consumer's switching costs, and (2) current contents incompatibility is offsetting the network quality difference among carriers.Telecom market, Mobile Phone, Switching costs, Vertically Integrated market, Compatibility, Conjoint analysis, Discrete choice model, Mixed logit model

Which telecom services should be sustained as national minimum services?

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Early evolution of spherical ejecta expanding into the circumstellar matter at ultra-relativistic speeds

We present a new self-similar solution describing early evolution of an ultra-relativistic flow resulting from a collision of homologously expanding spherical ejecta with the circumstellar matter, in which a shock wave propagates in the circumstellar matter while a weak discontinuity propagates in the ejecta at the sound speedComment: 5 pages, 2 figures, accepted for publication in PAS

Multi-quark baryons and color screening at finite temperature

We study baryons in SU(N) gauge theories at finite temperature according to the gauge/string correspondence based on IIB string theory. The baryon is constructed out of D5 brane and $N$ fundamental strings to form a color singlet $N$-quark bound state. At finite temperature and in the deconfining phase, we could find $k(<N)$-quark ``baryons''. Thermal properties of such $k$-quark baryons and also of the $N$-quark baryon are examined. We study the temperature dependence of color screening distance and Debye length of the baryon of $k$-quark and $N$-quark. We also estimate the melting temperature, where the baryons decay into quarks and gluons completely.Comment: 16 pages, 12 figure

D3/D7 holographic Gauge theory and Chemical potential

N=2 supersymmetric Yang-Mills theory with flavor hypermultiplets at finite temperature and in the dS${}_4$ are studied for finite quark number density ($n_b$) by a dual supergravity background with non-trivial dilaton and axion. The quarks and its number density $n_b$ are introduced by embedding a probe D7 brane. We find a critical value of the chemical potential at the limit of $n_b=0$, and it coincides with the effective quark mass given in each theory for $n_b=0$. At this point, a transition of the D7 embedding configurations occurs between their two typical ones. The phase diagrams of this transition are shown in the plane of chemical potential versus temperature and cosmological constant for YM theory at finite temperature and in dS${}_4$ respectively. In this phase transition, the order parameter is considered as $n_b$. % and the critical value of the chemical potential This result seems to be reasonable since both theories are in the quark deconfinement phase.Comment: 17 pages, 8 figure