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22 April 2006 DM vs Alternative Gravities, Edinburgh 1
Dynamical friction and MONDFernando J. Selman
22 April 2006 DM vs Alternative Gravities, Edinburgh 2
The roads to dynamical
friction
Binary collision approximation Chandrasekhar 1942, 1943
Chandrasekhar fluctuating force arguments Uhlenbeck and Ornstein 1930 (non stellar) Chandrasekhar and von Neumann 1943 Ahmad and Cohen (1974) Kandrup (1980) Bekenstein and Maoz (1992) del Popolo (1996)o Colpi and Pallavicini (1998)o Nelson and Tremaine (1999)
Polarization cloud methodo Marochnik (1968)o Kalnajs (1972)o Lynden-Bell and Kalnajs (1972)o Tremaine and Weinberg (1984)o Bekenstein and Zamir (1990)
22 April 2006 DM vs Alternative Gravities, Edinburgh 3
The approximations
Binary collisions Local approximation: infinite and homogeneous system Markov approximation: binary collisions of negligible duration Diffusion approximation: diffusion described by a Fokker-Planck
equation Neglect of self-gravity of response Resonances
22 April 2006 DM vs Alternative Gravities, Edinburgh 4
Chandrasekhar Binary Collisions
Formula
22 April 2006 DM vs Alternative Gravities, Edinburgh 5
Statistics of the fluctuating field
22 April 2006 DM vs Alternative Gravities, Edinburgh 6
Polarization cloud method
22 April 2006 DM vs Alternative Gravities, Edinburgh 7
The frictional drag formulas
22 April 2006 DM vs Alternative Gravities, Edinburgh 8
Caveat: M=10^5Msun, V = 100km/s, 20pc x 30pc
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