Isotropic Contact Forces in Arbitrary Representation: Heterogeneous Few-Body Problems and Low Dimensions
Résumé
The Bethe-Peierls asymptotic approach which models pairwise short-range forces by contact conditions is introduced in arbitrary representation for spatial dimensions less than or equal to three. The formalism is applied in various situations and emphasis is put on the momentum representation. In presence of a transverse harmonic confinement, dimensional reduction toward 2D or 1D physics is derived within this formalism. The energy theorem relating the mean energy of an interacting system to the asymptotic behavior of the one-particle density matrix illustrates the method in its second quantized form. Integral equations that encapsulate the Bethe-Peierls contact condition for few-body systems are derived. In 3D, for three-body systems supporting Efimov states, a nodal condition is introduced in order to obtain universal results from the Skorniakov Ter-Martirosian equation and the Thomas collapse is avoided. Four-body bound states eigenequations are derived and the 2D '3+1' bosonic ground state is computed as a function of the mass ratio.
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