A Necessary Condition for Individual Time-Steps in SPH Simulations (2008)
Saitoh, Takayuki R., Makino, Junichiro
We show that smoothed particle hydrodynamics method, used with individual time-steps, cannot handle explosion problems. The solution for this problem is to introduce a time-step limiter which reduces...
Trojan Stars in the Galactic Center (2008)
Fujii, Michiko, Iwasawa, Masaki, Funato, Yoko, Makino, Junichiro
We performed, for the first time, the simulation of spiral-in of a star cluster formed close to the Galactic center (GC) using a fully self-consistent N-body simulation of the system of the central...
Saitoh, Takayuki R., Daisaka, Hiroshi, Kokubo, Eiichiro, Makino, Junichiro, Okamoto, Takashi, Tomisaka, Kohji, ...
We investigated the evolution of interacting disk galaxies using high-resolution $N$-body/SPH simulations taking into account the multiphase nature of the interstellar medium (ISM). In our...
Saitoh, Takayuki R., Daisaka, Hiroshi, Kokubo, Eiichiro, Makino, Junichiro, Okamoto, Takashi, Tomisaka, Kohji, ...
We performed 3-dimensional N-body/SPH simulations to study how mass resolution and other model parameters such as the star formation efficiency parameter, C* and the threshold density, nth affect...
Iwasawa, Masaki, Funato, Yoko, Makino, Junichiro
In this paper, we investigate the structures of galaxies which either have or have had three BHs using $N$-body simulations, and compare them with those of galaxies with binary BHs. We found that the...
Environmental effect on the subhalo abundance -- a solution to the missing dwarf problem (2007)
Ishiyama, Tomoaki, Fukushige, Toshiyuki, Makino, Junichiro
Recent high-resolution simulations of the formation of dark-matter halos have shown that the distribution of subhalos is scale-free, in the sense that if scaled by the velocity dispersion of the...
6th and 8th Order Hermite Integrator for N-body Simulations (2007)
Nitadori, Keigo, Makino, Junichiro
We present sixth- and eighth-order Hermite integrators for astrophysical $N$-body simulations, which use the derivatives of accelerations up to second order ({\it snap}) and third order ({\it...
Modeling Dense Stellar Systems (2007)
Hut, Piet, Mineshige, Shin, Heggie, Douglas C., Makino, Junichiro
Black holes and neutron stars present extreme forms of matter that cannot be created as such in a laboratory on Earth. Instead, we have to observe and analyze the experiments that are ongoing in the...
Formation of Protoplanets from Massive Planetesimals in Binary Systems (2007)
Tsukamoto, Yusuke, Makino, Junichiro
More than half of stars reside in binary or multiple star systems and many planets have been found in binary systems. From theoretical point of view, however, whether or not the planetary formation...
Evolution of Collisionally Merged Massive Stars (2007)
Suzuki, Takeru K., Nakasato, Naohito, Baumgardt, Holger, Ibukiyama, Akihiro, Makino, Junichiro, Ebisuzaki, Toshi
We investigate the evolution of collisionally merged stars with mass of ~100 MSun which might be formed in dense star clusters. We assumed that massive stars with several tens Msun collide typically...
PGPG: An Automatic Generator of Pipeline Design for Programmable GRAPE Systems (2007)
Hamada, Tsuyoshi, Fukushige, Toshiyuki, Makino, Junichiro
We have developed PGPG (Pipeline Generator for Programmable GRAPE), a software which generates the low-level design of the pipeline processor and communication software for FPGA-based computing...
Portegies Zwart, Simon F., McMillan, Stephen L.W., Makino, Junichiro
We study the first 100Myr of the evolution of isolated star clusters initially contain- ing 144179 stars, including 13107 (10%) primordial hard binaries. Our calculations in- clude the effects of...
High-Performance Small-Scale Simulation of Star Clusters Evolution on Cray XD1 (2006)
Nitadori, Keigo, Makino, Junichiro, Abe, George
In this paper, we describe the performance of an $N$-body simulation of star cluster with 64k stars on a Cray XD1 system with 400 dual-core Opteron processors. A number of astrophysical $N$-body...
A Time-Symmetric Block Time-Step Algorithm for N-Body Simulations (2006)
Makino, Junichiro, Hut, Piet, Kaplan, Murat, Saygin, Hasan
The method of choice for integrating the equations of motion of the general N-body problem has been to use an individual time step scheme. For the sake of efficiency, block time steps have been the...
Missing Dwarf Problem in Galaxy Clusters (2006)
Kase, Hiroyuki, Makino, Junichiro, Funato, Yoko
We investigated the formation and evolution of CDM subhalos in galaxy-sized and cluster-sized halos by means of N-body simulations. Our aim is to make clear what the ``dwarf galaxy problem'' is. It...
High-Resolution Simulations of a Moon-Forming Impact and Post-Impact Evolution (2006)
Wada, Keiichi, Kokubo, Eiichiro, Makino, Junichiro
In order to examine the ``giant impact hypothesis'' for the Moon formation, we run the first grid-based, high-resolution hydrodynamic simulations for an impact between proto-Earth and a proto-planet....
Three-Body Affairs in the Outer Solar System (2005)
Funato, Yoko, Makino, Junichiro, Hut, Piet, Kokubo, Eiichiro, Kinoshita, Daisuke
Recent observations (Burnes2002,Veillet2002,Margot2002a) have revealed an unexpectedly high binary fraction among the Trans-Neptunian Objects (TNOs) that populate the Kuiper Belt. The TNO binaries...
Evolution of Galactic Nuclei. I. orbital evolution of IMBH (2005)
Matsubayashi, Tatsushi, Makino, Junichiro, Ebisuzaki, Toshikazu
Resent observations and theoretical interpretations suggest that IMBHs (intermediate-mass black hole) are formed in the centers of young and compact star clusters born close to the center of their...
Dynamical friction on satellite galaxies (2005)
Fujii, Michiko, Funato, Yoko, Makino, Junichiro
For a rigid model satellite, Chandrasekhar's dynamical friction formula describes the orbital evolution quite accurately, when the Coulomb logarithm is chosen appropriately. However, it is not known...
Evolution of Massive Blackhole Triples I -- Equal-mass binary-single systems (2005)
Iwasawa, Masaki, Funato, Yoko, Makino, Junichiro
We present the result of $N$-body simulations of dynamical evolution of triple massive blackhole (BH) systems in galactic nuclei. We found that in most cases two of the three BHs merge through...
The ecology of star clusters and intermediate mass black holes in the Galactic bulge (2005)
Zwart, Simon Portegies, Baumgardt, Holger, McMillan, Stephen L. W., Makino, Junichiro, Hut, Piet, Ebisuzaki, Toshi
We simulate the inner 100pc of the Milky-Way Galaxy to study the formation and evolution of the population of star clusters and intermediate mass black holes. For this study we perform extensive...
Nitadori, Keigo, Makino, Junichiro, Hut, Piet
The main performance bottleneck of gravitational N-body codes is the force calculation between two particles. We have succeeded in speeding up this pair-wise force calculation by factors between two...
Modified SIMD architecture suitable for single-chip implementation (2005)
We describe a modified SIMD architecture suitable for single-chip integration of a large number of processing elements, such as 1,000 or more. Important differences from traditional SIMD designs are:...
GRAPE-6A: A single-card GRAPE-6 for parallel PC-GRAPE cluster system (2005)
Fukushige, Toshiyuki, Makino, Junichiro, Kawai, Atsushi
In this paper, we describe the design and performance of GRAPE-6A, a special-purpose computer for gravitational many-body simulations. It was designed to be used with a PC cluster, in which each node...
Black Holes in Massive Star Clusters (2004)
McMillan, Steve, Baumgardt, Holger, Zwart, Simon Portegies, Hut, Piet, Makino, Junichiro
Close encounters and physical collisions between stars in young dense clusters can result in new channels for stellar evolution, and may lead to the formation of very massive stars and black holes...
Which Globular Clusters contain Intermediate-mass Black Holes? (2004)
Baumgardt, Holger, Makino, Junichiro, Hut, Piet
It has been assumed that intermediate-mass black holes (IMBHs) in globular clusters can only reside in the most centrally concentrated clusters, with a so-called `core-collapsed' density profile....
Formation of Omega Centauri by Tidal Stripping of a Dwarf Galaxy (2004)
Ideta, Makoto, Makino, Junichiro
We have investigated whether or not a tidal stripping scenario can reproduce the observed surface-brightness profile of omega Centauri using N-body simulations. Assuming that the progenitor of omega...
Massive Black Holes in Star Clusters. I. Equal-mass clusters (2004)
Baumgardt, Holger, Makino, Junichiro, Ebisuzaki, Toshikazu
In this paper we report results of collisional N-body simulations of the dynamical evolution of equal-mass star clusters containing a massive central black hole. Each cluster is composed of between...
Massive Black Holes in Star Clusters. II. Realistic Cluster Models (2004)
Baumgardt, Holger, Makino, Junichiro, Ebisuzaki, Toshikazu
We have followed the evolution of multi-mass star clusters containing massive central black holes through collisional N-body simulations done on GRAPE6. Each cluster is composed of between 16,384 to...
The formation of massive black holes through collision runaway in dense young star clusters (2004)
Zwart, Simon Portegies, Baumgardt, Holger, Hut, Piet, Makino, Junichiro, McMillan, Stephen
A luminous X-ray source is associated with a cluster (MGG-11) of young stars \~200pc from the center of the starburst galaxy M82. The properties of the X-ray source are best explained by a black hole...
The formation of Kuiper-belt Binaries through Exchange Reactions (2004)
Funato, Yoko, Makino, Junichiro, Hut, Piet, Kokubo, Eiichiro, Kinoshita, Daisuke
Recent observations have revealed an unexpectedly high binary fraction among the Trans-Neptunian Objects (TNOs) that populate the Kuiper-belt. The discovered binaries have four characteristics they...
Makino, Junichiro, Fukushige, Toshiyuki, Koga, Masaki, Namura, Ken
In this paper, we describe the architecture and performance of the GRAPE-6 system, a massively-parallel special-purpose computer for astrophysical $N$-body simulations. GRAPE-6 is the successor of...
Black hole binary mergers (2003)
I overview the current understanding of the evolution of massive black hole (MBH) binaries in the center of the host stellar system. One of the main questions is whether the stellar dynamical effect...
Evolution of Massive Black Hole Binaries (2003)
Makino, Junichiro, Funato, Yoko
We present the result of large-scale N-body simulations of the stellar-dynamical evolution of a massive black-hole binary at the center of a spherical galaxy. We focus on the dependence of the...
Fukushige, Toshiyuki, Kawai, Atsushi, Makino, Junichiro
We investigate the structure of the dark matter halo formed in the cold dark matter scenarios by N-body simulations with parallel treecode on GRAPE cluster systems. We simulated 8 halos with the mass...
Kuiper-belt Binary Formation through Exchange Reactions (2003)
Funato, Yoko, Makino, Junichiro, Hut, Piet, Kokubo, Eiichiro, Kinoshita, Daisuke
Recent observations (Burnes et al 2002,Veillet et al 2002, Margot et al 2002a) have revealed an unexpectedly high binary fraction among the Trans-Neptunian Objects (TNOs) that populate the Kuiper...
A Dynamical Model for the Globular Cluster G1 (2003)
Baumgardt, Holger, Makino, Junichiro, Hut, Piet, McMillan, Steve, Zwart, Simon Portegies
We present a comparison between the observational data on the kinematical structure of G1 in M31, obtained with the Hubble WFPC2 and STIS instruments, and the results of dynamical simulations carried...
Parameters of core-collapse (2003)
Baumgardt, Holger, Heggie, Douglas C., Hut, Piet, Makino, Junichiro
This paper considers the phenomenon of deep core collapse in collisional stellar systems, with stars of equal mass. The collapse takes place on some multiple, $\xi ^{-1}$, of the central relaxation...
Dynamical evolution of star clusters in tidal fields (2002)
Baumgardt, Holger, Makino, Junichiro
We report results of a large set of N-body calculations aimed to study the evolution of multi-mass star clusters in external tidal fields. Our clusters start with the same initial mass-functions, but...
A 29.5 Tflops simulation of planetesimals in Uranus-Neptune region on GRAPE-6 (2002)
Junichiro Makino, Eiichiro Kokubo, Toshiyuki Fukushige
As an entry for the 2002 Gordon Bell performance prize, we report the performance achieved on the GRAPE-6 system for a simulation of the early evolution of the protoplanet-planetesimal system of the...
To Circularize or Not to Circularize? -- Orbital Evolution of Satellite Galaxies (2002)
Hashimoto, Yoshikazu, Funato, Yoko, Makino, Junichiro
We investigated the orbital evolution of satellite galaxies using numerical simulations. It has been long believed that the orbit suffers circularization due to the dynamical friction from the...
We overview our GRAPE (GRAvity PipE) project to develop special-purpose computers for astrophysical N-body simulations. The basic idea of GRAPE is to attach a custom-build computer dedicated to the...
MODEST-1: Integrating Stellar Evolution and Stellar Dynamics (2002)
Hut, Piet, Shara, Michael M., Aarseth, Sverre J., Klessen, Ralf S., Lombardi Jr., James C., Makino, Junichiro, ...
We summarize the main results from MODEST-1, the first workshop on MOdeling DEnse STellar systems. Our goal is to go beyond traditional population synthesis models, by introducing dynamical...
Life Expectancy of the Large Magellanic Cloud (2002)
Yoko Funato, Yoshikazu Hashimoto, Junichiro Makino
We investigated the orbital evolution of sate]lite galaxies using numerical simulations. It has been long believed that the orbit suffers circularization due to the dynamical friction from the...
We present a novel, highly efficient algorithm to parallelize O(N^2) direct summation method for N-body problems with individual timesteps on distributed-memory parallel machines such as Beowulf...
Fukushige, Toshiyuki, Makino, Junichiro
We investigate the structure of the dark matter halo formed in three different cold dark matter scenarios. We performed N-body simulations of formation of 13 cluster-sized halos. In all runs, density...
A 11.55 Tfiops simulation of black holes in a galactic center on GRAPE-6 (2001)
Junichiro Makino, Toshiyuki Fukushige
As an entry for the 2001 Gordon Bell performance prize, we report the performance achieved on the GRAPE-6 system for the simulation of the dynamical evolution of a multiple black hole system in the...
Missing Link Found? --- The ``runaway'' path to supermassive black holes (2001)
Ebisuzaki, Toshikazu, Makino, Junichiro, Tsuru, Takeshi Go, Funato, Yoko, Zwart, Simon Portegies, Hut, Piet, ...
Observations of stellar kinematics, gas dynamics and masers around galactic nuclei have now firmly established that many galaxies host central supermassive black holes (SMBHs) with masses in the...
Pseudoparticle Multipole Method: A Simple Method To Implement High-Accuracy Treecode (2001)
High-accuracy Treecode, Atsushi Kawai, Junichiro Makino
In this letter we describe the pseudoparticle multipole method (P 2 M 2 ), a new method to express multipole expansion by a distribution of pseudoparticles. We can use this distribution of particles...
The lives and deaths of star clusters near the Galactic center (2001)
Zwart, Simon Portegies, Makino, Junichiro, McMillan, Stephen, Hut, Piet
We study the evolution and observability of young, compact star clusters near the Galactic center, such as the Arches and Quintuplet systems. The clusters are modeled by integrating the equations of...
which we call GRAPE-6, will be a heterogeneous multicomputer which combines these two specialized system with general-purpose parallel computer. In the following, we briefly discuss the positioning...
Runaway Collisions in Star Clusters (2000)
Zwart, Simon F. Portegies, Makino, Junichiro, McMillan, Stephen L. W., Hut, Piet
We study the occurrence of physical collisions between stars in young and compact star cluster. The calculations are performed on the GRAPE-4 with the starlab software environment which include the...
Pseudoparticle Multipole Method: A Simple Method to Implement High-Accuracy Treecode (2000)
Kawai, Atsushi, Makino, Junichiro
In this letter we describe the pseudoparticle multipole method (P2M2), a new method to express multipole expansion by a distribution of pseudoparticles. We can use this distribution of particles to...
How many young star clusters exist in the Galactic center? (2000)
Zwart, Simon Portegies, Makino, Junichiro, McMillan, Stephen, Hut, Piet
We study the evolution and observability of young compact star clusters within about 200pc of the Galactic center. Calculations are performed using direct N-body integration on the GRAPE-4, including...
A 1.349 Tflops simulation of black holes in a galactic center on GRAPE-6 (2000)
As an entry for the 2000 Gordon Bell performance prize, we report the performance achieved on a prototype GRAPE-6 system. GRAPE-6 is a special-purpose computer for astrophysical N-body calculations....
Structure of Dark Matter Halos From Hierarchical Clustering (2000)
Fukushige, Toshiyuki, Makino, Junichiro
We investigate the structure of the dark matter halo formed in the cold dark matter scenario using $N$-body simulations. We simulated 12 halos with the mass of $6.6\times 10^{11}M_{\odot}$ to...
A 1.349 Tflops simulation of black holes in a galactic center on GRAPE-6 (2000)
Junichiro Makino, Toshiyuki Fukushige, Masaki Koga
As an entry for the 2000 Gordon Bell performance prize, we report the performance achieved on a prototype GRAPE-6 system. GRAPE-6 is a special-purpose computer for astrophysical N-body calculations....
Direct Simulation of Dense Stellar Systems with GRAPE-6 (2000)
. In this paper we describe the current status of the GRAPE-6 project to develop a special-purpose computer with a peak speed exceeding 100 Tflops for the simulation of astrophysical N-body problems....
Direct Simulation of Dense Stellar Systems with GRAPE-6 (2000)
In this paper we describe the current status of the GRAPE-6 project to develop a special-purpose computer with a peak speed exceeding 100 Tflops for the simulation of astrophysical N-body problems....
GRAPE Project: special-purpose computers for many-body simulations (2000)
In this paper, we overview the GRAPE (GRAvity piPE) project to develop and use special-purpose computers for astrophysical many-body simulations. First, we discuss the trends in semiconductor...
Star cluster ecology IVa: Dissection of an open star cluster---photometry (2000)
Zwart, Simon F. Portegies, McMillan, Stephen L. W., Hut, Piet, Makino, Junichiro
The evolution of star clusters is studied using N-body simulations in which the evolution of single stars and binaries are taken self-consistently into account. Initial conditions are chosen to...
GRAPE-5: A Special-Purpose Computer for N-body Simulation (1999)
Kawai, Atsushi, Fukushige, Toshiyuki, Makino, Junichiro, Taiji, Makoto
We have developed a special-purpose computer for gravitational many-body simulations, GRAPE-5. GRAPE-5 is the successor of GRAPE-3. Both consist of eight custom pipeline chips (G5 chip and GRAPE...
PROGRAPE-1: A Programmable, Multi-Purpose Computer for Many-Body Simulations (1999)
Hamada, Tsuyoshi, Fukushige, Toshiyuki, Kawai, Atsushi, Makino, Junichiro
We have developed PROGRAPE-1 (PROgrammable GRAPE-1), a programmable multi-purpose computer for many-body simulations. The main difference between PROGRAPE-1 and "traditional" GRAPE systems is that...
On the Cusp around Central Black Holes in Luminous Elliptical Galaxies (1999)
Nakano, Taro, Makino, Junichiro
In this letter, we show that a massive black hole (MBH) which falls into the center of a galaxy in dynamical timescale leaves a weak cusp ($\rho \propto r^{-1/2}$) around it, which is in good...
7.0/Mflops Astrophysical N-Body Simulation with Treecode on GRAPE-5 (1999)
Kawai, Atsushi, Fukushige, Toshiyuki, Makino, Junichiro
As an entry for the 1999 Gordon Bell price/performance prize, we report an astrophysical N-body simulation performed with a treecode on GRAPE-5 (Gravity Pipe 5) system, a special-purpose computer for...
Thermal Relaxation in One-Dimensional Self-Gravitating Systems (1999)
In this paper, we study the thermal relaxation in the one-dimensional self-gravitating system, or the so-called sheet model. According to the standard argument, the thermal relaxation time of the...
Thermal Relaxation in One-Dimensional Self-Gravitating Systems (1999)
In this paper, we study the thermal relaxation in the one-dimensional self-gravitating system, or the so-called sheet model. According to the standard argument, the thermal relaxation time of the...
Thermal Relaxation in One-Dimensional Self-Gravitating Systems (1999)
In this paper, we study the thermal relaxation in the one-dimensional self-gravitating system, or the so-called sheet model. According to the standard argument, the thermal relaxation time of the...
Yet another fast multipole method without multipoles - Pseudo-particle multipole method (1999)
In this paper we describe a new approach to implement the O(N) fast multipole method and O(N log N) tree method, which uses pseudoparticles to express the potential field. The new method is similar...
Yet another fast multipole method without multipoles --- Pseudo-particle multipole method (1999)
In this paper we describe a new approach to implement the O(N) fast multipole method and O(N log N) tree method, which uses pseudoparticles to express the potential field. The new method is similar...
A Simple Formulation of the Fast Multipole Method: Pseudo-Particle Multipole Method (1998)
Kawai, Atsushi, Makino, Junichiro
We present the pseudo-particle multipole method (P2M2), a new method to handle multipole expansion in fast multipole method and treecode. This method uses a small number of pseudo-particles to...
Star cluster ecology III: Runaway collisions in young compact star clusters (1998)
Zwart, Simon Portegies, Makino, Junichiro, McMillan, Stephen L. W., Hut, Piet
The evolution of young compact star clusters is studied using N-body simulations in which both stellar evolution and physical collisions between stars are taken into account. The initial conditions...
On the Mass Distribution of Planetesimals in the Early Runaway Stage (1998)
Junichiro Makino, Toshiyuki Fukushige, Yoko Funato
We derive the stationary distribution of the mass of planetesimals from the coagulation equation under the assumption of energy equipartition. In the threedimensional case, we found that the...
On the Mass Distribution of Planetesimals in the Early Runaway Stage (1998)
Junichiro Makino, Toshiyuki Fukushige, Yoko Funato
We derive the stationary distribution of the mass of planetesimals from the coagulation equation under the assumption of energy equipartition. In the threedimensional case, we found that the...
On the Mass Distribution of Planetesimals in the Early Runaway Stage (1998)
Junichiro Makino, Toshiyuki Fukushige, Yoko Funato
We derive the stationary distribution of the mass of planetesimals from the coagulation equation under the assumption of energy equipartition. In the threedimensional case, we found that the...
Merger Rate Of Equal-Mass Spherical Galaxies (1998)
We present cross sections and reaction rates for merging to occur during encounters of equal-mass spherical galaxies. As an application, we determine the rate of galaxy merging in clusters of...
We present cross sections and reaction rates for merging to occur during encounters of equal-mass spherical galaxies. As an application, we determine the rate of galaxy merging in clusters of...
Yet another fast multipole method without multipoles --- Pseudo-particle multipole method (1998)
In this paper we describe a new approach to implement the O(N) fast multipole method and O(N log N) tree method, which uses pseudoparticles to express the potential field. The new method is similar...
Yet another fast multipole method without multipoles --- Pseudo-particle multipole method (1998)
In this paper we describe a new approach to implement the O(N) fast multipole method and $O(N\log N)$ tree method, which uses pseudoparticles to express the potential field. The new method is similar...
In this paper I discuss the relation between widely used "Scientometric" measures and "reputation" of research groups within the scientific community. To this goal, I present the result of the...