# a1005 - d dt = 0 (Liouville s Theorem) . (2) Due February 5...

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ADVANCED DYNAMICS — PHY 4241/5227 HOME AND CLASS WORK – SET 5 (February 1, 2010) (20) Liouville’s Theorem: We defne the velocity in phase space as a 2 n -dimensional vector ~v = ( ˙ q 1 , . . . , ˙ q n , ˙ p 1 , . . . , ˙ p n ). A large collection o± particles can be de- scribed by their density in phase space ρ ( q 1 , . . . , q n , p 1 , . . . , p n ). I± their are no sources or sinks, we have a conserved current ∂ρ ∂t + ( ~v ρ ) = 0 (1) where = ∂q 1 , . . . , ∂q n , ∂p 1 , . . . , ∂p n ! is the gradient in phase space . (a) Expand (1) in sums o± partial derivatives (you get fve terms when you keep coordinates and momenta in separate contributions). (b) Use Hamilton’s equa- tions o± motion to show that two terms cancel out. (c) Combine the remaining terms to
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Unformatted text preview: d dt = 0 (Liouville s Theorem) . (2) Due February 5 in class (6 points). Read M&amp;T chapter 7.12. (21) Poisson brackets are defned by [ g, h ] = X k g q k h p k-h q k g p k ! where g and h are unctions o q i , p i and, possibly, t . Show the ollowing properties (due February 10 beore class, 10 points): 1. dg dt = [ g, H ] + g t . 2. q j = [ q j , H ] . 3. p j = [ p j , H ] . 4. [ x i , x j ] = [ p i , p j ] = 0 ; [ x i , p j ] = ij , 5. [ x i , L j ] = ijk x k , [ p i , L j ] = ijk p k , and [ L i , L j ] = ijk L k , , where the Einstein summation convention is used and L j = jkl x k p l is the i th component o the angular momentum o the system....
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