N-body units

N-body units
Quantity Expression
Length (R) \frac{1}{R} = \frac{2}{M^2} \sum_{i,j \ne i}^{N} \frac{m_i m_j}{\left| \vec{r_j}-\vec{r_i} \right| }
Mass (M) M = \sum_{i=1}^{N} m_i

N-body units are a completely self-contained system of units used for N-body simulations of self gravitating systems in astrophysics. In this system, the base physical units are chosen so that the total mass, M, the gravitational constant, G, and the virial radius, R, are normalised. The underlying assumption is that the system of N objects (stars) satisfies the virial theorem. The consequence of standard N-body units is that the velocity dispersion of the system is \scriptstyle v = 1/\sqrt{2} and that the dynamical -crossing- time scales as \scriptstyle t = 2\sqrt{2} . The first mention of standard N-body units was by Michel Hénon (1971).[1] They were taken up by Haldan Cohn (1979)[2] and later widely advertised and generalized by Douglas Heggie and Robert Mathieu (1986).[3]

References


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Body armour — was the manufactured use of various materials to provide rigid and dense protection layer to an individual s body surface in combat. As such it could be improvised or designed, partial or fully covering, from light weight to one that is extremely …   Wikipedia

  • Body burden — Body burden, also known as chemical load, is the amount of harmful chemicals present in a person s body. It is determined by biomonitoring, which assesses exposure by measuring the chemicals or their metabolites in human specimens such as blood… …   Wikipedia

  • Units of measurement — Weights and measures redirects here. For other uses, see Weights and measures (disambiguation). The former Weights and Measures office in Seven Sisters, London A unit of measurement is a definite magnitude of a physical quantity, defined and… …   Wikipedia

  • Units for the Reinstatement of Order — The Units for the Reinstatement of Order (Greek: Μονάδες Αποκατάστασης Τάξης, Monades Apokatastasis Taksis), usually abbreviated as MAT, are a special division of the Hellenic Police, whose primary and most famous role is that of riot control.… …   Wikipedia

  • Body Language (Kylie Minogue album) — Infobox Album Name = Body Language Type = Album Artist = Kylie Minogue Released = flagicon|World February 10, 2004 Recorded = 2003 Genre = Pop, Dance, R B Length = 47:51 Label = Parlophone Mushroom Capitol Producer = Sunny Roads Julian Gallagher… …   Wikipedia

  • Units conversion by factor-label — Many, if not most, parameters and measurements in the physical sciences and engineering are expressed as a numerical quantity and a corresponding dimensional unit; for example: 1000 kg/m³, 100 kPa/bar, 50 miles per hour, 1000 Btu/lb. Converting… …   Wikipedia

  • Body farm — For other uses, see Body farm (disambiguation). A body farm is a research facility where human decomposition can be studied in a variety of settings. The aim is to gain a better understanding of the decomposition process, permitting the… …   Wikipedia

  • Body force — A body force is a force that acts on the volume of a body and also can be defined as an external force acting throughout the mass of a body. Gravity is a body force, the forces associated with a non inertial reference frame may be viewed as body… …   Wikipedia

  • Body weight — Although many people prefer the less ambiguous term body mass, the term body weight is overwhelmingly used in daily English speech and in biological and medical science contexts to describe the mass of an organism s body. Body weight is measured… …   Wikipedia

  • Body corporate — In English Law (and as a result, throughout the Commonwealth Realms), body corporate is the legal term for a corporation. It is distinct from a natural person, although it has many of the same legal rights.A body corporate can be either a… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”