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A two-dimensional gas is a collection of objects constrained to move in a planar or other two-dimensional space in a gaseous state. The objects can be: ideal gas elements such as rigid disks undergoing elastic collisions; elementary particles, or any object in physics which obeys laws of motion. The concept of a two-dimensional gas is used either because: * (a) the issue being studied actually takes place in two dimensions (as certain surface molecular phenomena); or, * (b) the two-dimensional form of the problem is more tractable than the analogous mathematically more complex three-dimensional problem. While physicists have studied simple two body interactions on a plane for centuries, the attention given to the two-dimensional gas (having many bodies in motion) is a 20th-century pursuit. Applications have led to better understanding of superconductivity,〔Feld, et al, "Observation of a pairing pseudogap in a two-dimensional gas". ''Nature'' 480, 7375, pp 75–78.〕 gas thermodynamics, certain solid state problems and several questions in quantum mechanics. ==Classical mechanics== Research at Princeton University in the early 1960s〔C.M.Hogan, ''Non-equilibrium statistical mechanics of a two-dimensional gas'', Dissertation, Princeton University, Department of Physics, May 4, 1964〕 posed the question of whether the Maxwell–Boltzmann statistics and other thermodynamic laws could be derived from Newtonian laws applied to multi-body systems rather than through the conventional methods of statistical mechanics. While this question appears intractable from a three-dimensional closed form solution, the problem behaves differently in two-dimensional space. In particular an ideal two-dimensional gas was examined from the standpoint of relaxation time to equilibrium velocity distribution given several arbitrary initial conditions of the ideal gas. Relaxation times were shown to be very fast: on the order of mean free time . In 1996 a computational approach was taken to the classical mechanics non-equilibrium problem of heat flow within a two-dimensional gas.〔D. Risso and P. Cordero, ''Two-Dimensional Gas of Disks: Thermal Conductivity'', ''Journal of Statistical Physics'', volume 82, pages 1453–1466, (1996)〕 This simulation work showed that for N>1500, good agreement with continuous systems is obtained. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Two-dimensional gas」の詳細全文を読む スポンサード リンク
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