# Editing Maxwell speed distribution

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==Derivation== | ==Derivation== | ||

− | According to the '''Shivanian and Lopez-Ruiz model''' <ref>[http:// | + | According to the '''Shivanian and Lopez-Ruiz model''' <ref>[http://arxiv.org/abs/1105.4813 Elyas Shivanian and Ricardo Lopez-Ruiz "A New Model for Ideal Gases. Decay to the Maxwellian Distribution", arXiv:1105.4813v1 24 May (2011)]</ref>, consider an [[ideal gas]] composed of particles having a mass of unity in the three-dimensional (<math>3D</math>) space. As long as there no privileged direction when in equilibrium, we can take any direction in space and study the discrete time evolution of the velocity distribution in that direction. Let us call this axis <math>U</math>. We can complete a Cartesian system with two additional orthogonal axis <math>V,W</math>. If <math>p_n(u){\mathrm d}u</math> represents the probability of finding a particle of the gas with velocity component in the direction <math>U</math> comprised between <math>u</math> and <math>u + {\mathrm d}u</math> at time <math>n</math>, then the probability to have at this time <math>n</math> a particle with a <math>3D</math> velocity <math>(u,v,w)</math> will be <math>p_n(u)p_n(v)p_n(w)</math>. The particles of the gas collide between them, and after a number of interactions of the order of system size, a new velocity distribution is attained at time <math>n+1</math>. Concerning the interaction of particles with the bulk of the gas, we make two simplistic and realistic assumptions in order to obtain the probability of having a velocity <math>x</math> in the direction <math>U</math> at time <math>n+1</math>: (1) Only those particles with an energy greater than <math>x^2</math> at time <math>n</math> can contribute to this velocity <math>x</math> in the direction <math>U</math>, that is, all those particles whose velocities <math>(u,v,w)</math> verify <math> u^2+v^2+w^2\ge x^2</math>; (2) The new velocities after collisions are equally distributed in their permitted ranges, that is, particles with velocity <math>(u,v,w)</math> can generate maximal velocities <math>\pm U_{max}=\pm\sqrt{u^2+v^2+w^2}</math>, then the allowed range of velocities <math>[-U_{max},U_{max}]</math> measures <math>2|U_{max}|</math>, and the contributing probability of these particles to the velocity <math>x</math> will be <math>p_n(u)p_n(v)p_n(w)/(2|U_{max}|)</math>. Taking all together we finally get the expression for the evolution operator <math>\mathcal T </math>. This is: |

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