The odd fermion system is considered as a hybrid system consisting of a fermion and many bosons. The effect of antisymmetrization is expressed by a set of many-body forces acting among the bosons and the fermion. The explicit form of these forces has been derived and their influences have been estimated.
An effective boson Hamiltonian is derived from the original Hamiltonian of a many-fermion system. The results show that when the intrinsic motion of bosons is collective and the excitation energies of the system are small, the effective boson-boson interaction can be reduced to a two-body interaction while for odd systems or systems with uncorrelated fermions, there is an additional two-body boson-fermion interaction. Both these interactions can be calculated from the original fermion-fermion ones. Thus, the microscopic foundation of the interacting boson model is established without recourse to mapping procedures.NUCLEAR STRUCTURE Interacting boson model, boson fermion hybrid representation, microscopic foundation.
The problem that usually arises in the study of a quantum system is the integration of the eigenvalue equation of the Hamiltonian, namely the search for eigenstates and the corresponding eigenvalues of energy. The eigenstates, in the representation of the position, are described by eigenfunctions with the same position variable. The relations work modulo a normalization constant. The number of nodes of a function allows to determine its parity: an odd number of nodes characterizes as an antisymmetric function, while a even number of nodes is a symmetric one. The state of a system can be characterized as bosonic or fermionic depending on whether the wave function is even or odd, respectively. The two operators are nilpotent, when applied more than once to an eigenstate, it generates a null ket, regardless of the starting state.
Bosons have symmetric wave function under particle exchange, while fermions have antisymmetric wave functions. This leads to differences in behavior of the two kinds of particles even in the gaseous state. Strong repulsive forces between atoms at close range are due to the Pauli principle that forbids two electrons to be in the same energy or position state. A repulsive Pauli pressure operates similarly in white dwarf stars. Bosons undergo Bose–Einstein condensation because of Bose statistics. The wave function symmetry of particles with spin can affect the magnetic states and the behavior of transport properties, for example, viscosity and thermal conductivity. The symmetry properties of bosons at a beam splitter are demonstrated in the Hong–Ou–Mandel effect or in a Michelson interferometer via the Hanbury Brown-Twiss effect. Researchers see boson bunching and fermion antibunching in experiments considered.
We introduce a new method for deriving the time-dependent Hartree or Hartree-Fock equations as an effective mean-field dynamics from the microscopic Schrödinger equation for fermionic many-particle systems in quantum mechanics. The method is an adaption of the method used in Pickl (Lett. Math. Phys. 97 (2) 151–164 2011 ) for bosonic systems to fermionic systems. It is based on a Gronwall type estimate for a suitable measure of distance between the microscopic solution and an antisymmetrized product state. We use this method to treat a new mean-field limit for fermions with long-range interactions in a large volume. Some of our results hold for singular attractive or repulsive interactions. We can also treat Coulomb interaction assuming either a mild singularity cutoff or certain regularity conditions on the solutions to the Hartree(-Fock) equations. In the considered limit, the kinetic and interaction energy are of the same order, while the average force is subleading. For some interactions, we prove that the Hartree(-Fock) dynamics is a more accurate approximation than a simpler dynamics that one would expect from the subleading force. With our method we also treat the mean-field limit coupled to a semiclassical limit, which was discussed in the literature before, and we recover some of the previous results. All results hold for initial data close (but not necessarily equal) to antisymmetrized product states and we always provide explicit rates of convergence.