Book contents
- Frontmatter
- Contents
- Preface
- Introduction
- Part I Idealized homogeneous systems – basic ideas and gentle relaxation
- Part II Infinite inhomogeneous systems – galaxy clustering
- 20 How does matter fill the Universe?
- 21 Gravitational instability of the infinite expanding gas
- 22 Gravitational graininess initiates clustering
- 23 Growth of the two-galaxy correlation function
- 24 The energy and early scope of clustering
- 25 Later evolution of cosmic correlation energies
- 26 N-body simulations
- 27 Evolving spatial distributions
- 28 Evolving velocity distributions
- 29 Short review of basic thermodynamics
- 30 Gravity and thermodynamics
- 31 Gravithermodynamic instability
- 32 Thermodynamics and galaxy clustering; ξ(r)∝r-2
- 33 Efficiency of gravitational clustering
- 34 Non-linear theory of high order correlations
- 35 Problems and extensions
- 36 Bibliography
- Part III Finite spherical systems – clusters of galaxies, galactic nuclei, globular clusters
- Part IV Finite flattened systems – galaxies
- Index
26 - N-body simulations
Published online by Cambridge University Press: 05 July 2011
- Frontmatter
- Contents
- Preface
- Introduction
- Part I Idealized homogeneous systems – basic ideas and gentle relaxation
- Part II Infinite inhomogeneous systems – galaxy clustering
- 20 How does matter fill the Universe?
- 21 Gravitational instability of the infinite expanding gas
- 22 Gravitational graininess initiates clustering
- 23 Growth of the two-galaxy correlation function
- 24 The energy and early scope of clustering
- 25 Later evolution of cosmic correlation energies
- 26 N-body simulations
- 27 Evolving spatial distributions
- 28 Evolving velocity distributions
- 29 Short review of basic thermodynamics
- 30 Gravity and thermodynamics
- 31 Gravithermodynamic instability
- 32 Thermodynamics and galaxy clustering; ξ(r)∝r-2
- 33 Efficiency of gravitational clustering
- 34 Non-linear theory of high order correlations
- 35 Problems and extensions
- 36 Bibliography
- Part III Finite spherical systems – clusters of galaxies, galactic nuclei, globular clusters
- Part IV Finite flattened systems – galaxies
- Index
Summary
What in the Universe I know can give directions how to go?
W.H. AudenBecause the classical interaction between gravitating point masses is totally understood – the subject has had its Newton – it is possible to solve the clustering problem completely, in principle. All that is necessary is to integrate the equations of motion with the desired initial conditions and read off the answer. Non-linear regimes are dealt with as easily as linear ones. From the time fast computers became available, about 1960, to the present day, a considerable industry has grown up around these numerical solutions. Beginning with the earliest computations for a couple of dozen particles, the power of computers and techniques has improved by more than an order of magnitude each decade. Now it is possible to follow several thousand galaxies for tens of relaxation times with direct integrations.
New numerical techniques are always being developed. Their general goal is more information about increased numbers of particles for longer times. Compromises are often worked, usually sacrificing information for more particles. Since direct integrations retain the most information, and computers always get better, this approach will continue to flourish.
The direct integration method integrates the equations of motion explicitly to retain complete information about all the galaxy positions and velocities at any time.
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- Chapter
- Information
- Gravitational Physics of Stellar and Galactic Systems , pp. 181 - 184Publisher: Cambridge University PressPrint publication year: 1985