ScalingStacks

Démonstration. [01U4]

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Démonstration.

Comme les formes de bidegré (k,k)(k,k) commutent, il suffit de traiter le cas où j=1j=1. Alors

d′′⁡(u1​d′​d′′⁡u2∧⋯∧d′​d′′⁡up∧α)OPEN=d′′⁡u1∧d′​d′′⁡u2∧⋯∧d′​d′′⁡up∧α)+u1​d′​d′′⁡u2∧⋯∧d′​d′′⁡up∧d′′⁡α,\mathop{\mathrm{d}^{\prime\prime}}(u^{1}\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{2}\wedge\dots\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{p}\wedge\alpha)\\ =\mathop{\mathrm{d}^{\prime\prime}}u^{1}\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{2}\wedge\dots\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{p}\wedge\alpha)+u^{1}\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{2}\wedge\dots\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{p}\wedge\mathop{\mathrm{d}^{\prime\prime}}\alpha,

puis

d′​d′′⁡(u1​d′​d′′⁡u2∧⋯∧d′​d′′⁡up∧α)\displaystyle\hskip-28.45274pt\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}(u^{1}\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{2}\wedge\dots\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{p}\wedge\alpha)\hskip-170.71652pt
OPEN=d′​d′′⁡u1∧d′​d′′⁡u2∧⋯∧d′​d′′⁡up∧α)−d′′⁡u1∧d′​d′′⁡u2∧⋯∧d′​d′′⁡up∧d′′⁡α\displaystyle=\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{1}\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{2}\wedge\dots\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{p}\wedge\alpha)-\mathop{\mathrm{d}^{\prime\prime}}u^{1}\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{2}\wedge\dots\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{p}\wedge\mathop{\mathrm{d}^{\prime\prime}}\alpha
+d′u1d′​d′′u2∧⋯∧d′​d′′up∧d′′α−u1d′​d′′u2∧⋯∧d′​d′′up∧d′​d′′α\displaystyle\quad+\mathop{\mathrm{d^{\prime}}}u^{1}\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{2}\wedge\dots\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{p}\wedge\mathop{\mathrm{d}^{\prime\prime}}\alpha-u^{1}\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{2}\wedge\dots\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{p}\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}\alpha
OPEN=d′​d′′⁡u1∧d′​d′′⁡u2∧⋯∧d′​d′′⁡up∧α)−u1​d′​d′′⁡u2∧⋯∧d′​d′′⁡up∧d′​d′′⁡α.\displaystyle=\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{1}\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{2}\wedge\dots\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{p}\wedge\alpha)-u^{1}\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{2}\wedge\dots\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}u^{p}\wedge\mathop{\mathrm{d}^{\prime}\mathrm{d}^{\prime\prime}}\alpha.

L’assertion résulte alors de la formule de Green. ∎

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