偏光高速度干渉計を用いた音場可視化計測に関する研究

早大学位記番号:新8114早稲田大

New effect in wave-packet scatterings of quantum fields: Saddle points, Lefschetz thimbles, and Stokes phenomenon

We find a new contribution in wave-packet scatterings, which has been overlooked in the standard formulation of S-matrix. As a concrete example, we consider a two-to-two scattering of light scalars $\phi$ by another intermediate heavy scalar $\Phi$, in the Gaussian wave-packet formalism: $\phi\phi\to\Phi\to\phi\phi$. This contribution can be interpreted as an "in-time-boundary effect" of $\Phi$ for the corresponding $\Phi\to\phi\phi$ decay, proposed by Ishikawa et al., with a newly found modification that would cure the previously observed ultraviolet divergence. We show that such an effect can be understood as a Stokes phenomenon in an integral over complex energy plane: The number of relevant saddle points and Lefschetz thimbles (steepest descent paths) discretely changes depending on the configurations of initial and final states in the scattering.Comment: 5 pages with 3 pages of Supplemental Material, 3 figure

An Algorithm for the Assignment Problem with Stochastic Side Constraints

In this paper, we consider the assignment problem with stochastic side constraints, and propose a practical algorithm for solving it. Such a problem may arise, for example, when the assignment requires some scarce resources and the total amounts of those resources are subject to a random variation. Therefore, the problem seems quite general and significant in practice. This algorithm takes a special structure of the problem into account, and may be regarded as a heuristic modification of the method for two-stage linear programming under uncertainty. Although we cannot guarantee that the solution obtained by the proposed algorithm will coincide with the true optimal solution of the problem, our limited computational experience on small test problems indicates that good approximate solutions can be obtained in a fairly small computation time

Brain Imaging of Nicotinic Receptors in Alzheimer's Disease

Neuronal nicotinic acetylcholine receptors (nAChRs) are a family of ligand-gated ion channels which are widely distributed in the human brain. Several lines of evidence suggest that two major subtypes (α4β2 and α7) of nAChRs play an important role in the pathophysiology of Alzheimer's disease (AD). Postmortem studies demonstrated alterations in the density of these subtypes of nAChRs in the brain of patients with AD. Currently, nAChRs are one of the most attractive therapeutic targets for AD. Therefore, several researchers have made an effort to develop novel radioligands that can be used to study quantitatively the distribution of these two subtypes in the human brain with positron emission tomography (PET) and single-photon emission computed tomography (SPECT). In this paper, we discuss the current topics on in vivo imaging of two subtypes of nAChRs in the brain of patients with AD

Whitish daytime radiative cooling using diffuse reflection of non-resonant silica nanoshells

Daytime radiative cooling offers efficient passive cooling of objects by tailoring their spectral responses, holding great promise for green photonics applications. A specular reflector has been utilized in cooling devices to minimize sunlight absorption, but such a glaring surface is visually less appealing, thus undesirable for public use. Here, by exploiting strong diffuse reflection of silica nanoshells in a polymer matrix, daytime radiative cooling below the ambient temperature is experimentally demonstrated, while showing whitish color under sunlight. The cooling device consists of a poly(methyl methacrylate) layer with randomly distributed silica nanoshells and a polydimethylsiloxane (PDMS) layer on an Ag mirror. The non-resonant nanoshells exhibit uniform diffuse reflection over the solar spectrum, while fully transparent for a selective thermal radiation from the underneath PDMS layer. In the temperature measurement under the sunlight irradiation, the device shows 2.3 degrees C cooler than the ambient, which is comparable to or even better than the conventional device without the nanoshells. Our approach provides a simple yet powerful nanophotonic structure for realizing a scalable and practical daytime radiative cooling device without a glaring reflective surface