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Multiple Solutions for a Nonlinear Dirichlet Problem via - Mathematics

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Sketch of the Proof of Theorem A:<br />

Now suppose u4 is of one sign. Without loss of generality we can<br />

assume u4 ∈ S2. Let P be a subregion of S2 such that P ∩ K = {u2,u4}.<br />

From (0.3), (0.4), (0.12) and the excision property of Leray-Schauder<br />

degree it follows that<br />

−1 = d(∇J,S2,0)<br />

= dloc(∇J,u2) + dloc(∇J,u4) + d(∇J,S2 \ P,0)<br />

= −1 + (−1) k + d(∇J,S2 \ P,0).<br />

Hence, the existence property of the Leray-Schauder degree implies<br />

there must be another signed solution of (0.1).<br />

MULTIPLE SOLUTIONS FOR A NONLINEAR DIRICHLET PROBLEM VIA MORSE INDEX – 41➲<br />

▲ ▲<br />

➲ ❏ ✘

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