The fate of Landau levels under δ-interactions
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Date
2022
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Abstract
We consider the self-adjoint Landau Hamiltonian H-0 in L-2(R-2) whose spectrum consists of infinitely degenerate eigenvalues Lambda(q), q is an element of Z(+), and the perturbed Landau Hamiltonian H-upsilon = H-0 + upsilon delta(Gamma), where Gamma subset of R-2 is a regular Jordan C-1,C-1-curve and upsilon is an element of L-p(Gamma; R), p > 1, has a constant sign. We investigate ker(H-upsilon - Lambda(q)), q is an element of Z(+), and show that generically
0 <= dim ker(H-upsilon - Lambda(q)) - dim ker(T-q(upsilon delta(Gamma))) < infinity,
where T-q(upsilon delta(Gamma)) = p(q)(upsilon delta(Gamma))p(q), is an operator of Berezin-Toeplitz type, acting in p(q)L(2)(R-2), and p(q) is the orthogonal projection onto ker(H-0 - Lambda(q)). If upsilon not equal 0 and q = 0, then we prove that ker(T-0(upsilon delta(Gamma))) = {0}. If q >= 1 and Gamma = C-r is a circle of radius r, then we show that dim ker(T-q(delta(Cr))) <= q, and the set of r is an element of (0, infinity) for which dim ker(T-q(delta(Cr))) >= 1 is infinite and discrete.
0 <= dim ker(H-upsilon - Lambda(q)) - dim ker(T-q(upsilon delta(Gamma))) < infinity,
where T-q(upsilon delta(Gamma)) = p(q)(upsilon delta(Gamma))p(q), is an operator of Berezin-Toeplitz type, acting in p(q)L(2)(R-2), and p(q) is the orthogonal projection onto ker(H-0 - Lambda(q)). If upsilon not equal 0 and q = 0, then we prove that ker(T-0(upsilon delta(Gamma))) = {0}. If q >= 1 and Gamma = C-r is a circle of radius r, then we show that dim ker(T-q(delta(Cr))) <= q, and the set of r is an element of (0, infinity) for which dim ker(T-q(delta(Cr))) >= 1 is infinite and discrete.
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Landau Hamiltonian, delta-interactions, perturbations of eigenspaces, Berezin-Toeplitz operators, Laguerre polynomials