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we see that associating ũ to u produces a one-to-one correspondence between M Ω K (γ1, γ2; x) and<br />

the space � M Ω K (γ1, γ2; x) consisting of the maps ũ : [0, ∞[×[0, 1] → T ∗ M 2 solving ∂ J, ˜ H (ũ) = 0 with<br />

boundary conditions<br />

ũ(s, 0) ∈ N ∗ ∆M ∀s ≥ 0, (176)<br />

ũ(s, 1) ∈ T ∗ q0M × T ∗ q0M ∀s ≥ 0, (177)<br />

π ◦ ũ1(0, 1 − ·) ∈ W u (γ1), π ◦ ũ2(0, ·) ∈ W u (γ2), (178)<br />

lim ũ(s, ·) = ˜x. (179)<br />

s→+∞<br />

Similarly, we have a one-to-one correspondence between M K Υ (γ1, γ2; x) and the space � M K Υ (γ1, γ2; x)<br />

consisting of pairs (α, ũ) where α is a positive number and ũ : Σ + → T ∗ M 2 is a solution of the<br />

problem above, with (176) replaced by<br />

ũ(s, 0) ∈ T ∗ q0 M × T ∗ q0 M ∀s ∈ [0, α], ũ(s, 0) ∈ N ∗ ∆M ∀s ≥ α. (180)<br />

Fix some ũ 0 ∈ � M Ω K (γ1, γ2; x). Since we are looking for solutions near ũ 0 , we can localize the<br />

problem as follows. Let k = m Ω (γ1; L1) + m Ω (γ2; L2). Let q :Êk × Σ + → M 2 be a map such that<br />

q(0, s, t) = π ◦ ũ 0 (s, t) ∀(s, t) ∈ Σ + , q(λ, s, ·) → π ◦ ˜x for s → +∞, ∀λ ∈Êk ,<br />

and such that the mapÊk ∋ λ ↦→ (q1(λ, 0, 1 − ·), q2(λ, 0, ·)) ∈ Ω 1 (M 2 )<br />

is a diffeomorphism onto a neighborhood of π ◦ (˜x1(−·), ˜x2) in W u (γ1) × W u (γ2). By means of a<br />

suitable trivialization of q ∗ (TM 2 ) and using the usual W 1,p Sobolev setting with p > 2, we can<br />

transform the problem of finding mas ũ solving ∂ J, ˜ H (ũ) = 0 together with (177), (178) and (179)<br />

and being close to ũ 0 , into the problem of finding pairs (λ, u) ∈Êk ×W 1,p (Σ + , T ∗Ê2n ), solving an<br />

equation of the form<br />

with boundary conditions<br />

∂u(z) + f(λ, z, u(z)) = 0 ∀z ∈ Σ + , (181)<br />

u(0, t) ∈ N ∗ (0) ∀t ∈ [0, 1], u(s, 1) ∈ N ∗ (0) ∀s ≥ 0. (182)<br />

Then the boundary conditon (176) is translated into<br />

u(s, 0) ∈ N ∗ ∆Ên ∀s ≥ 0, (183)<br />

and the solution ũ 0 corresponds to the solution λ = 0 and u ≡ 0 of (181), (182), and (183). On<br />

the other hand, the problem � M K Υ (γ1, γ2; x) of finding (α, ũ α ) solving ∂ J, ˜ H (ũ α ) = 0 together with<br />

(177), (178), (179) and (180) corresponds to the problem of finding (λ, u) ∈Êk ×W 1,p (Σ + , T ∗Ê2n )<br />

solving (181) with boundary conditions (182) and<br />

u(s, 0) ∈ N ∗ (0) ∀s ∈ [0, α], u(s, 0) ∈ N ∗ ∆Ên ∀s ≥ α. (184)<br />

In order to find a common functional setting, it is convenient to turn the boundary condition (184)<br />

into (183) by means of a suitable conformal change of variables on the half-strip Σ + .<br />

The holomorphic function z ↦→ cosz maps the half strip {0 < Re z < π, Im z > 0} biholomorphically<br />

onto the upper half-planeÀ={Im z > 0}. It is also a homeomorphism between<br />

the closure of these domains. We denote by arccos the determination of the arc-cosine which is<br />

the inverse of this function. Then the function z ↦→ (1 + cos(iπz))/2 is a biholomorphism from<br />

the interior of Σ + toÀ, mapping 0 into 1 and i into 0. Let ǫ > 0. If we conjugate the linear<br />

automorphism z ↦→ (1 + ǫ)z ofÀby the latter biholomorphism, we obtain the following map:<br />

ϕǫ(z) = i<br />

π arccos� (1 + ǫ)cos(iπz) + ǫ � .<br />

98

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