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Travaux sur les symétries de Lie des équations aux ... - DMA - Ens

Travaux sur les symétries de Lie des équations aux ... - DMA - Ens

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espect to x 1 and (8.96) 2 with respect to x 1 ; solving, we obtain four newrelations:(8.99)X 1x 1 x 1 x = r X 1 + r X 2 + r X 21 x + r Y 2 x 1 + r Y y + r Y x 1 x 1 + r X 2x 1 x 2,Y x 1 x 1 y = r X 1 + r X 2 + r X 2x + r Y 2 x 1 + r Y y + r Y x 1 x 1 + r X 2x 1 x 2,X 2x 1 x 2 y = r X 1 + r X 2 + r X 2x + r Y 2 x 1 + r Y y + r Y x 1 x 1 + r X 2x 1 x 2,X 2x 1 x 1 x = r X 1 + r X 2 + r X 22 x + r Y 2 x 1 + r Y y + r Y x 1 x 1 + r X 2x 1 x 2.We get (8.86) 19 and (8.86) 14 .Next, in (8.81) 5 , we replace: X 1xfrom (8.90); X 21 xfrom (8.98); Y 1 x 1 yfrom (8.97) 2 ; we get:(8.100)Xy 2 = r X 1 + r X 2 + r Xy 1 + r X 2x + r Y 2 x 1 + r Y y + r Y x 1 x 1++ s ∗ X 2x 1 x + 1 s∗ Y yy + s ∗ X 1x 1 y .We differentiate (8.98) with respect to x 1 and we replace: X 1xfrom (8.90);1X 2xfrom (8.98); Y 1 x 1 y from (8.97) 2 ; Y x 1 x 1 x 1 from (8.83) 1; X 2x 1 x 1 xfrom 2(8.99) 4 ; we get:(8.101)X 2x 1 x 1+2 X 1x 1 y = r X 1 +r X 2 +r Xy 1 +r X 2x 2+r Y x 1+r Y y+r Y x 1 x 1+r X 2x 1 x 2.In (8.82) 2 , we replace: X 1xfrom (8.90); X 11 x 1 xfrom (8.97) 1 1 ; Y x 1 y from(8.97) 2 ; and we reorganize:(8.102)2 Xx 2 2 y −6 X x 1 1 y −X x 2 1 x = −2 Y yy+r X 1 +r X 2 +r X 21 x 2+r Y x 1+r Y y+r Y x 1 x 1+r X x 2 1 x 2.Differentiating (8.81) 3 with respect to y, we replace: Y x 1 y from (8.97) 2 ;Y x 1 x 1 y from (8.99) 2 ; and we reorganize:(8.103)X 2x 2 y −2 X 1x 1 y = −Y yy+r X 1 +r X 2 +r X 2x 2+r Y x 1+r Y y+r Y x 1 x 1+r X 2x 1 x 2.For the three unknowns X 2x 1 x, X 1 1 x 1 y , X 2x 2 y, we then solve the four equations(8.101), (8.102), (8.103), (8.83) 4 (in which we replace: X 1xfrom (8.90);1X 2xfrom (8.98); Y 1 x 1 y from (8.97) 2 ; X 1x 1 xfrom (8.97) 1 1 ):(8.104)X 2x 1 x = r X 1 + r X 2 + r X 11 y + r X 2x + r Y 2 x 1 + r Y y + r Y x 1 x 1 + r X 2x 1 x + r Y yy, 2X 1x 1 y = r X 1 + r X 2 + r Xy 1 + r X 2x + r Y 2 x 1 + r Y y + r Y x 1 x 1 + r X 2x 1 x + r Y yy, 2X 2x 2 y = r X 1 + r X 2 + r Xy 1 + r X 2x + r Y 2 x 1 + r Y y + r Y x 1 x 1 + r X 2x 1 x + r Y yy. 2We get (8.86) 6 and (8.86) 10 . Replacing then X 2x 1 x, X 1 1 x 1 yin (8.100) gives(8.105)Xy 2 = r X 1 +r X 2 +r Xy 1 +r X 2x 2+r Y x 1+r Y y+r Y x 1 x 1+r X 2x 1 x 2+r Y yy.This is (8.86) 5 .285

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