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BrainHurts
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Homework Statement
Consider the map [itex]\Phi[/itex] : ℝ4 [itex]\rightarrow[/itex] ℝ2
defined by [itex]\Phi[/itex] (x,y,s,t)=(x2+y, yx2+y2+s2+t2+y)
show that (0,1) is a regular value of [itex]\Phi[/itex] and that the level set [itex]\Phi^{-1}[/itex] is diffeomorphic to S2 (unit sphere)
Homework Equations
The Attempt at a Solution
So I have the Jacobian
D[itex]\Phi[/itex] = [2x 2y 0 0; 2x 2y+1 2s 2t]
the reduced row echelon form of D[itex]\Phi[/itex] is a rank 2 matrix which implies that F is a smooth submersion.
So I guess I'm a little confused on the definition: Let M and N be smooth manifolds
If F:M→N is smooth and let p [itex]\in[/itex] M, then p is a regular point if D[itex]\Phi[/itex] at p is onto.
D[itex]\Phi[/itex] is a rank 2 matrix which implies that D[itex]\Phi[/itex] is onto right?
Another question that I have is that the pre-image of (0,1) under [itex]\Phi[/itex] is a subset of ℝ4 any hints on the diffeomorphism part?