We consider a system of N pairwise interacting particles described by the Hamiltonian H, where σess(H) = [0, ∞) and none of the particle pairs has a zero energy resonance. The pair potentials are allowed to take both signs and obey certain restrictions regarding the fall off. It is proved that if N ⩾ 4 and none of the Hamiltonians corresponding to the subsystems containing N − 2 or less particles has an eigenvalue equal to zero then H has a finite number of negative energy bound states. This result provides a positive proof to a long-standing conjecture of Amado and Greenwood stating that four bosons with an empty negative continuous spectrum have at most a finite number of negative energy bound states. Additionally, we give a short proof to the theorem of Vugal'ter and Zhislin on the finiteness of the discrete spectrum and pose a conjecture regarding the existence of the “true” four-body Efimov effect.
Abstract We consider a system of three identical bosons in
R3 R 3 with two-body zero-range interactions and a three-body hard-core repulsion of a given radius
a>0 a > 0 . Using a quadratic form approach, we prove that the corresponding Hamiltonian is self-adjoint and bounded from below for any value of a . In particular, this means that the hard-core repulsion is sufficient to prevent the fall to the center phenomenon found by Minlos and Faddeev in their seminal work on the three-body problem in 1961. Furthermore, in the case of infinite two-body scattering length, also known as unitary limit, we prove the Efimov effect, i.e., we show that the Hamiltonian has an infinite sequence of negative eigenvalues
En E n accumulating at zero and fulfilling the asymptotic geometrical law
En+1/En→e−s02πforn→+∞ E n + 1 / E n → e - 2 π s 0 for n → + ∞ holds, where
s0≈1.00624 s 0 ≈ 1.00624 .