An Aspect of Spatial and Structural Changes in the Japanese Retail Market

The latest census of commerce shows that a drastic change is undergoing in Japanese retail market, especially in convenience goods market. This article is a case study, concernig the changes in the spatial and structural pattern of urban retail system in Japan. Some consideration on the new trends of market competition are also discussed

Bigravity from gradient expansion

We discuss how the ghost-free bigravity coupled with a single scalar field can be derived from a braneworld setup. We consider DGP two-brane model without radion stabilization. The bulk configuration is solved for given boundary metrics, and it is substituted back into the action to obtain the effective four-dimensional action. In order to obtain the ghost-free bigravity, we consider the gradient expansion in which the brane separation is supposed to be sufficiently small so that two boundary metrics are almost identical. The obtained effective theory is shown to be ghost free as expected, however, the interaction between two gravitons takes the Fierz-Pauli form at the leading order of the gradient expansion, even though we do not use the approximation of linear perturbation. We also find that the radion remains as a scalar field in the four-dimensional effective theory, but its coupling to the metrics is non-trivial.Comment: 16 page

Appearance of Boulware-Deser ghost in bigravity with doubly coupled matter

We discuss the ghost freeness in the case when we add matter coupled to two metrics to the ghost-free bigravity. In this paper we show that the Boulware-Deser ghost generally revives in the presence of doubly coupled matter and that ghost freeness strongly restricts the model of kinetically doubly coupled matter. This result may anticipate difficulties in the attempt to derive the ghost-free bigravity as a low-energy effective theory, starting with a model applicable at high energies.Comment: 15 page

Constraint on ghost-free bigravity from gravitational Cherenkov radiation

We investigate gravitational Cherenkov radiation in a healthy branch of background solutions in the ghost-free bigravity model. In this model, because of the modification of dispersion relations, each polarization mode can possess subluminal phase velocities, and the gravitational Cherenkov radiation could be potentially emitted from a relativistic particle. In the present paper, we derive conditions for the process of the gravitational Cherenkov radiation to occur and estimate the energy emission rate for each polarization mode. We found that the gravitational Cherenkov radiation emitted even from an ultrahigh energy cosmic ray is sufficiently suppressed for the graviton's effective mass less than $100\,{\rm eV}$, and the bigravity model with dark matter coupled to the hidden metric is therefore consistent with observations of high energy cosmic rays.Comment: 13 pages, 2 figures; v

Mapping the ghost free bigravity into braneworld setup

We discuss whether or not bigravity theory can be embedded into the braneworld setup. As a candidate, we consider Dvali-Gabadadze-Porrati two-brane model with the Goldberger-Wise radion stabilization. We will show that we can construct a ghost free model whose low energy spectrum is composed of a massless graviton and a massive graviton with a small mass. As is expected, the behavior of this effective theory is shown to be identical to the ghost free bigravity. Unfortunately, this correspondence breaks down at a relatively low energy due to the limitation of the adopted stabilization mechanism

On variations of Yama Nim and Triangular Nim

Yama Nim is a two heaps Nim game introduced in the second author's Master Thesis, where the player takes more than $2$ tokens from one heap, and return $1$ token to the other heap. Triangular Nim is a generalization, where the player takes several tokens from one heap, and return some tokens (at least one token) to the other heap, so that the total number of the tokens in the heaps decrease strictly. In this paper, we investigate their winning strategies, Grundy numbers, and their variations and generalizations. Particularly interesting is the Wythoff variations, where in addition to the Yama/Triangular Nim moves, the player is allowed to take tokens from both heaps, say $i$ tokens from the first heap and $j$ tokens from the other, under some restrictions for $i$ and $j$. For example when we force $i=j>0$ for the Triangular Nim, then the pair of non-negative integers $(x, y)$ with $x$ less than or equal to $y$ is in the $P$-position if and only if $(x, y) is in {(0, 0), (0, 1), (1, 3), (3, 6), (6, 10), (10, 15), ...}$, namely the winning strategy is described by triangular numbers. In other rulesets, we also found examples where the square numbers, pentagonal numbers, geometric progressions, and so on.Comment: 20 page

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Rhodopsin-mediated light-off-induced protein kinase A activation in mouse rod photoreceptor cells

網膜の知られざる光応答を顕微鏡観察で発見 --光センサー細胞が暗黒に反応した--. 京都大学プレスリリース. 2020-10-14.Detect with PKAchu. 京都大学プレスリリース. 2020-10-30.Light-induced extrasynaptic dopamine release in the retina reduces adenosine 3′, 5′-cyclic monophosphate (cAMP) in rod photoreceptor cells, which is thought to mediate light-dependent desensitization. However, the fine time course of the cAMP dynamics in rods remains elusive due to technical difficulty. Here, we visualized the spatiotemporal regulation of cAMP-dependent protein kinase (PKA) in mouse rods by two-photon live imaging of retinal explants of PKAchu mice, which express a fluorescent biosensor for PKA. Unexpectedly, in addition to the light-on-induced suppression, we observed prominent light-off-induced PKA activation. This activation required photopic light intensity and was confined to the illuminated rods. The estimated maximum spectral sensitivity of 489 nm and loss of the light-off-induced PKA activation in rod-transducin-knockout retinas strongly suggest the involvement of rhodopsin. In support of this notion, rhodopsin-deficient retinal explants showed only the light-on-induced PKA suppression. Taken together, these results suggest that, upon photopic light stimulation, rhodopsin and dopamine signals are integrated to shape the light-off-induced cAMP production and following PKA activation. This may support the dark adaptation of rods