Takashi Hara
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Takashi Hara has a total of 4 co-authors. Here are the top co-authors by number of shared publications:
- Gordon Slade
Department of Mathematics and Statistics McMaster University L8S 4K1 Hamilton ON Canada
2 shared publications - Satoshi Adachi
Department of Physics, Faculty of Science, Tokyo Institute of Technology, Meguro 152-8550, Japan
2 shared publications - Tatsuhiko Koike
Department of Physics, Keio University, Hiyoshi, Kohoku, Yokohama 223, Japan
2 shared publications - Gordon Slade
McMaster University
1 shared publication
Latest Publications
- Open Access
The scaling limit of the incipient infinite cluster in high-dimensional percolation. II. Integrated super-Brownian excursion
For independent nearest-neighbour bond percolation on Z^d with d >> 6, we prove that the incipient infinite cluster's two-point function and three-point function converge to those of integrated super-Brownian excursion (ISE) in the scaling limit. The proof is based on an extension of the new expansion for percolation derived in a previous paper, and involves treating the magnetic field as a complex variable. A special case of our result for the two-point function implies that the probability that the cluster of the origin consists of n sites, at the critical point, is given by a multiple of n^{-3/2}, plus an error term of order n^{-3/2-\epsilon} with \epsilon >0. This is a strong statement that the critical exponent delta is given by delta =2.
Open AccessThe scaling limit of the incipient infinite cluster in high-dimensional percolation. II. Integrated super-Brownian excursion
For independent nearest-neighbour bond percolation on Z^d with d >> 6, we prove that the incipient infinite cluster's two-point function and three-point function converge to those of integrated super-Brownian excursion (ISE) in the scaling limit. The proof is based on an extension of the new expansion for percolation derived in a previous paper, and involves treating the magnetic field as a complex variable. A special case of our result for the two-point function implies that the probability that the cluster of the origin consists of n sites, at the critical point, is given by a multiple of n^{-3/2}, plus an error term of order n^{-3/2-\epsilon} with \epsilon >0. This is a strong statement that the critical exponent delta is given by delta =2.
- 1 April 1999
- Published by American Physical Society (APS) in Physical Review D
- Vol. 59 (10) , 104008
Critical behavior in gravitational collapse of a perfect fluid
To confirm the scenario of critical behavior in gravitational collapse in a previous paper we carry out a rather complete analysis for perfect fluids with pressure proportional to density, in a wide range of the adiabatic index γ. In particular, the uniqueness of the relevant mode around a fixed point is established by a Lyapunov analysis. This shows that critical phenomena occur not only for the radiation fluid but also for perfect fluids with We also analyze the stability of other self-similar solutions and also discuss the universality class.- 1 April 1999
- Published by American Physical Society (APS) in Physical Review D
- Vol. 59 (10) , 104008
Critical behavior in gravitational collapse of a perfect fluid
To confirm the scenario of critical behavior in gravitational collapse in a previous paper we carry out a rather complete analysis for perfect fluids with pressure proportional to density, in a wide range of the adiabatic index γ. In particular, the uniqueness of the relevant mode around a fixed point is established by a Lyapunov analysis. This shows that critical phenomena occur not only for the radiation fluid but also for perfect fluids with We also analyze the stability of other self-similar solutions and also discuss the universality class.- Open Access
The scaling limit of the incipient infinite cluster in high-dimensional percolation. I. Critical exponents
This is the first of two papers on the critical behaviour of bond percolation models in high dimensions. In this paper, we obtain strong joint control of the critical exponents eta and delta, for the nearest-neighbour model in very high dimensions d>>6 and for sufficiently spread-out models in all dimensions d>6. The exponent eta describes the low frequency behaviour of the Fourier transform of the critical two-point connectivity function, while delta describes the behaviour of the magnetization at the critical point. Our main result is an asymptotic relation showing that, in a joint sense, eta = 0 and delta = 2. The proof uses a major extension of our earlier expansion method for percolation. This result provides evidence that the scaling limit of the incipient infinite cluster is the random probability measure on R^d known as integrated super-Brownian excursion (ISE), in dimensions above 6. In the sequel to this paper, we extend our methods to prove that the scaling limits of the incipient infinite cluster's two-point and three-point functions are those of ISE for the nearest-neighbour model in dimensions d>>6.
Open AccessThe scaling limit of the incipient infinite cluster in high-dimensional percolation. I. Critical exponents
This is the first of two papers on the critical behaviour of bond percolation models in high dimensions. In this paper, we obtain strong joint control of the critical exponents eta and delta, for the nearest-neighbour model in very high dimensions d>>6 and for sufficiently spread-out models in all dimensions d>6. The exponent eta describes the low frequency behaviour of the Fourier transform of the critical two-point connectivity function, while delta describes the behaviour of the magnetization at the critical point. Our main result is an asymptotic relation showing that, in a joint sense, eta = 0 and delta = 2. The proof uses a major extension of our earlier expansion method for percolation. This result provides evidence that the scaling limit of the incipient infinite cluster is the random probability measure on R^d known as integrated super-Brownian excursion (ISE), in dimensions above 6. In the sequel to this paper, we extend our methods to prove that the scaling limits of the incipient infinite cluster's two-point and three-point functions are those of ISE for the nearest-neighbour model in dimensions d>>6.
- Open Access
The incipient infinite cluster in high-dimensional percolation
We announce our recent proof that, for independent bond percolation in high dimensions, the scaling limits of the incipient infinite cluster's two-point and three-point functions are those of integrated super-Brownian excursion (ISE). The proof uses an extension of the lace expansion for percolation.
Open AccessThe incipient infinite cluster in high-dimensional percolation
We announce our recent proof that, for independent bond percolation in high dimensions, the scaling limits of the incipient infinite cluster's two-point and three-point functions are those of integrated super-Brownian excursion (ISE). The proof uses an extension of the lace expansion for percolation.
- Open Access
Renormalization group and critical behaviour in gravitational collapse
We present a general framework for understanding and analyzing critical behaviour in gravitational collapse. We adopt the method of renormalization group, which has the following advantages. (1) It provides a natural explanation for various types of universality and scaling observed in numerical studies. In particular, universality in initial data space and universality for different models are understood in a unified way. (2) It enables us to perform a detailed analysis of time evolution beyond linear perturbation, by providing rigorous controls on nonlinear terms. Under physically reasonable assumptions we prove: (1) Uniqueness of the relevant mode around a fixed point implies universality in initial data space. (2) The critical exponent $\beta_{BH}$ and the unique positive eigenvalue $\kappa$ of the relevant mode is exactly related by $\beta_{BH} = \beta /\kappa$, where $\beta$ is a scaling exponent. (3) The above (1) and (2) hold also for discretely self-similar case (replacing ``fixed point'' with ``limit cycle''). (4) Universality for diffent models holds under a certain condition. According to the framework, we carry out a rather complete (though not mathematically rigorous) analysis for perfect fluids with pressure proportional to density, in a wide range of the adiabatic index $\gamma$. The uniqueness of the relevant mode around a fixed point is established by Lyapunov analyses. This shows that the critical phenomena occurs not only for the radiation fluid but also for perfect fluids with $1 < \gamma \lesssim 1.88$. The accurate values of critical exponents are calculated for the models.Open AccessRenormalization group and critical behaviour in gravitational collapse
We present a general framework for understanding and analyzing critical behaviour in gravitational collapse. We adopt the method of renormalization group, which has the following advantages. (1) It provides a natural explanation for various types of universality and scaling observed in numerical studies. In particular, universality in initial data space and universality for different models are understood in a unified way. (2) It enables us to perform a detailed analysis of time evolution beyond linear perturbation, by providing rigorous controls on nonlinear terms. Under physically reasonable assumptions we prove: (1) Uniqueness of the relevant mode around a fixed point implies universality in initial data space. (2) The critical exponent $\beta_{BH}$ and the unique positive eigenvalue $\kappa$ of the relevant mode is exactly related by $\beta_{BH} = \beta /\kappa$, where $\beta$ is a scaling exponent. (3) The above (1) and (2) hold also for discretely self-similar case (replacing ``fixed point'' with ``limit cycle''). (4) Universality for diffent models holds under a certain condition. According to the framework, we carry out a rather complete (though not mathematically rigorous) analysis for perfect fluids with pressure proportional to density, in a wide range of the adiabatic index $\gamma$. The uniqueness of the relevant mode around a fixed point is established by Lyapunov analyses. This shows that the critical phenomena occurs not only for the radiation fluid but also for perfect fluids with $1 < \gamma \lesssim 1.88$. The accurate values of critical exponents are calculated for the models.