Long Wang 교수

Introducing the <scp>dragon</scp> simulation project, we present direct <it>N</it>-body simulations of four massive globular clusters (GCs) with 106 stars and 5 per cent primordial binaries at a high level of accuracy and realism. The GC evolution is computed with <scp>nbody6++gpu</scp> and follows the dynamical and stellar evolution of individual stars and binaries, kicks of neutron stars and black holes (BHs), and the effect of a tidal field. We investigate

Accurate direct <it>N</it>-body simulations help to obtain detailed information about the dynamical evolution of star clusters. They also enable comparisons with analytical models and Fokker-Planck or Monte Carlo methods. <scp>nbody6</scp> is a well-known direct <it>N</it>-body code for star clusters, and <scp>nbody6++</scp> is the extended version designed for large particle number simulations by supercomputers. We present <scp>nbody6++gpu&l

We use the Millennium Simulation, a 10 billion particle simulation of the growth of cosmic structure, to construct a new model of galaxy clustering. We adopt a methodology that falls midway between the traditional semi-analytic approach and the halo occupation distribution (HOD) approach. In our model, we adopt the positions and velocities of the galaxies that are predicted by following the orbits and merging histories of the substructures in the simulation. Rather than using star formation and

ABSTRACT The numerical simulations of massive collisional stellar systems, such as globular clusters (GCs), are very time consuming. Until now, only a few realistic million-body simulations of GCs with a small fraction of binaries ($5{{\ \rm per\ cent}}$) have been performed by using the nbody6++gpu code. Such models took half a year computational time on a Graphic Processing Unit (GPU)-based supercomputer. In this work, we develop a new N-body code, petar, by combining the methods of Barnes–Hut

ABSTRACT Many possible scenarios for the formation of multiple stellar populations (MSPs) in globular clusters (GCs) have been discussed so far, including the involvement of asymptotic giant branch stars, fast-rotating main-sequence stars, very massive main-sequence stars and mass-transferring massive binaries based on stellar evolution modelling. But self-consistent, dynamical simulations of very young GCs are usually not considered. In this work, we perform direct N-body modelling of such syst

Instabilities in planetary systems can result in the ejection of planets from their host system, resulting in free-floating planets (FFPs). If this occurs in a star cluster, the FFP may remain bound to the star cluster for some time and interact with the other cluster members until it is ejected. Here, we use $N$-body simulations to characterise close star-planet and planet-planet encounters and the dynamical fate of the FFP population in star clusters containing $500-2000$ single or binary star

Recently, three stellar sequences separated in age by about 1 Myr were discovered in the Orion Nebula Cluster (ONC; Beccari et al. 2017). Kroupa et al. (2018) suggest that such small dense subpopulations eject all their OB stars via the decay of unstable few-body systems such that the gas can recombine and form new stars. This explains the multisequence phenomenon without introducing an extra mechanism into star formation theory. In this work, we apply the recently updated primordial binary dist

ABSTRACT An accurate and efficient method dealing with the few-body dynamics is important for simulating collisional N-body systems like star clusters and to follow the formation and evolution of compact binaries. We describe such a method which combines the time-transformed explicit symplectic integrator and the slow-down method. The former conserves the Hamiltonian and the angular momentum for a long-term evolution, while the latter significantly reduces the computational cost for a weakly per

Abstract Numerical simulations based on particle methods have been widely used in various fields including astrophysics. To date, various versions of simulation software have been developed by individual researchers or research groups in each field, through a huge amount of time and effort, even though the numerical algorithms used are very similar. To improve the situation, we have developed a framework, called FDPS (Framework for Developing Particle Simulators), which enables researchers to de

ABSTRACT Previous theoretical studies suggest that the Population III (Pop3) stars tend to form in extremely metal-poor gas clouds with approximately $10^5 \ \mathrm{M}_\odot$ embedded in mini dark matter haloes. Very massive stars can form via multiple collisions in Pop3 star clusters and eventually evolve to intermediate-mass black holes (IMBHs). In this work, we conduct star-by-star N-body simulations for modelling the long-term evolution of Pop3 star clusters. We find that if the mini dark m

ABSTRACT Observations found that star clusters contain a large fraction of binaries. Tight binaries are an important heating source that influences the long-term dynamical evolution of star clusters. However, due to the limitation of N-body tool, previous theoretical modelling for globular clusters (GCs) by using direct N-body simulations has not investigated how a large fraction of primordial binaries affect their long-term evolution. In this work, by using the high-performance N-body code, pet

Abstract Recent observations have detected top-heavy IMFs in dense star forming regions like the Arches cluster. Whether such IMFs also exist in old dense stellar systems like globular clusters is difficult to constrain, because massive stars already became black holes (BHs) and neutron stars (NSs). However, studies of stellar dynamics find that BHs/NSs influence the long-term evolution of star clusters. Following Breen & Heggie (2013) and by carrying out two-component N-body simulations, we

This paper considers the minimization of a loss function, whose variables contain both continuous and discrete components. When only noisy measurements of the loss function are available, we propose the mixed simultaneous perturbation stochastic approximation (MSPSA) algorithm that uses the pseudo-gradient information to iteratively update the estimates while maintaining the mixed-variables-type constraints. Our work unifies two practical algorithms: the simultaneous perturbation stochastic appr