Project/Area Number 
11640168

Research Category 
GrantinAid for Scientific Research (C)

Allocation Type  Singleyear Grants 
Section  一般 
Research Field 
Basic analysis

Research Institution  Okayama University 
Principal Investigator 
HORA Akihito Okayama Univ., Fac. of Environmental Science and Technology, Associate Professor, 環境理工学部, 助教授 (10212200)

CoInvestigator(Kenkyūbuntansha) 
MURAI Joshin Okayama Univ., Graduate School of Humanities and Social Sciences, Assistant, 大学院・文化科学研究科, 助手 (00294447)
SASAKI Toru Okayama Univ., Fac. of Environmental Science and Technology, Lecturer, 環境理工学部, 講師 (20260664)
HIROKAWA Masao Okayama Univ., Fac. of Science, Associate Professor, 理学部, 助教授 (70282788)

Project Period (FY) 
1999 – 2000

Project Status 
Completed (Fiscal Year 2000)

Budget Amount *help 
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2000: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1999: ¥1,600,000 (Direct Cost: ¥1,600,000)

Keywords  harmonic analysis / probability model / random walk / quantum probability / central limit theorem / spectrum / distanceregular graph / the cutoff phenomenon / 対称群 / スケーリング極限 
Research Abstract 
We studied asymptotic behavior of probability models by using the methods of harmonic analysis. Main results are included in 1. the cutoff phenomenon in random walks and 2. central limit theorems in algebraic probability. 1. The cutoff phenomenon is a sort of critical phenomenon widely observed in the process of convergence to the equilibrium for Markov chains. It is known that the multiplicities of eigenvalues of a transition matrix, which are caused by symmetry of the system, play an important role. In this project, we seeked a rigorous and practical criterion for the cutoff phenomenon beyond verification in individual models and intuitive understanding based on the degeneration of the second eigenvalue. Focusing on distanceregular graphs, we obtained a criterion described in terms of spectral data of the graph. This enables us to find models of the cutoff phenomenon systematically. 2. Quantum central limit theorems form a main stream in algebraic probability. In this project, we studied important relations between independence of noncommutative random variables and central limit theorems, making much of their algebraic and combinatorial aspects. As a concrete result, we mention the asymptotic spectral distribution of the Laplacian operator on a Johnson graph with respect to the Gibbs state under a low temperature and infinite volume limit. This result leads us to the consideration of creators and annihilators on a nontrivial interacting Fock space and hence gives a good working example in this direction.
