Boson-fermion

Thus, the two bosons have an inereased probability density of being at the same point in spaee, while the two fermions have a vanishing probability density of being at the same point. This eonelusion also applies to systems with N identieal partieles. Identical bosons (fermions) behave as though they are under the influence of mutually attractive (repulsive) forces. These apparent forces are called exchange forces, although they are not forces in the mechanical sense, but rather statistical results. 

Iachello, F., and van Isacker, P. (1991), The Interacting Boson-Fermion Model, Cambridge University Press. 

The upper (resp. lower) sign stands for the fields z,Z of bosonic (fermionic) statistics. Integration after the ghost fields yields some numerical factor and the quantum action... 

Particles can be classified as fermions or bosons. Fermions obey the Pauli principle and have antisymmetric wave functions and half-integer spins. (Neutrons, protons, and electrons are fermions.) Bosons do not obey the Pauli principle and have symmetric wave functions and integer spins. (Photons are bosons.)... 

The remaining important aspect is how to derive these properties from a microscopic theory. In this respect, particularly interesting is the interacting boson-fermion model described at this workshop by Micnas [23]. This model is an extension of the method discussed above to mixed systems of bosons and fermions [24]. A symmetry analysis of this system will be presented elsewhere. 

Boson-Fermion Symmetries and Dynamical Supersymmetries for Odd-Odd Nuclei... 

The concept of boson-fermion symmetries and supersymmetries is applied to odd-odd nuclei. 

In this report we discuss the extension of this concept to odd-odd nuclei. Odd-odd nuclei provide richer and more complex structure, and the residual proton-neutron interaction appears explicitly in the boson-fermion interaction. 

Here we discuss the boson-fermion system for odd-odd nuclei using the concept of dynamical symmetry and supersymmetry. The dimension of the fermionic subspace is nv, where n- (nv) is the total number of compo-... 

Experimental Tests of Boson-Fermion Symmetries and Supersymmetries Using Coulomb Excitation with Heavy Ions... 

C.W. de Jager, in Interacting Boson-Boson and Boson-Fermion Systems, p.225, ed. 0. Scholten, (World Scientific, Singapore 1984) [Die83] A.E.L. Dieperink, Prog. Part. Nucl. Phys. 9, 121 (1983). 

Last, but not least, it is important to search for other regions besides the Pt region in which the nuclear structure can be described in terms of supersymmetric boson-fermion theory. The proven existence of several such regions would bring us one step closer to a comprehensive theory of all nuclei. 

BOSE-EINSTEIN CONDENSATION IN A BOSON-FERMION MODEL OF CUPRATES... 

Key words Superconductivity cuprates boson-fermion model Bose-Einstein condensation. 

Bose-Einstein Condensation in a Boson-Fermion Model of Cuprates 135 T.A. Mamedov, and M. de Llano... 

Finally, we stress that the quantum chemical method presented here has the advantage over DFT-based techniques that it also furnishes wavefunctions that can be used to perform computations of spectra, and therefore have a better contact with the experiment. Another advantage of this approach is that, unlike the diffusion Monte-Carlo method, it can coherently be applied to studies of fermion and mixed boson/fermion doped clusters. An example can be found in our recent work on the Raman spectra of (He)w-Br2(X) clusters [27,28]. 

Figure 2. DDF vs. temperature for bosonic and fermionic Li atoms in an optical lattice. Thin solid line fluctuations due to evaporation (12) (scaling factor 7.8), thin dashed line statistical fluctuations (13). Thick solid (dashed) line total fluctuations (W2) for bosonic (fermionic) Li atoms. Parameters Vo = 5 neV, (ns) = 0.1, d = 0.1 pm, cv Li) 3.6 x 106 J.kg-1.K-1, AF Li) = 6.10 10 m and u)v (Li) 2.106 s-1 [Kastberg 1995]. Inset solid (dashed) line static structure factor vs. n forphonons (nearly-free fermions) in a lattice at finite T.

Comprehensive reviews of different versions of the interacting boson and interacting boson-fermion models, as well as surveys of transitions between dynamical symmetries have been published, e.g., by lachello and Arima (1987), lachello and Van Isacker (1991), and Fenyes (2002). 

The equations above refer to scattering of distinguishable particles. For identical bosons (fermions), only even (odd) values of L are allowed and the prefactors are modified. 

Identical bosons (fermions) can collide in even (odd) partial waves. The role of partial waves is discussed in Chapter 1. Here we use f as the corresponding angular momentum quantum number. The first partial-wave contribution for bosons (fermions) is then the -wave with i = 0 (p-wave with = 1) [43]. At ultralow temperatures, only 5-wave collisions are dominant with the consequence that collisions between identical fermions are suppressed. The absence of 5-wave collisions is also the reason why, for instance, direct evaporative cooling cannot be applied to a sample of identical fermions. The situation changes when fermionic atoms are in different internal states, like hyperfine or Zeeman sublevels. The distinguishable particles can then interact in any partial wave. Fermion-composed molecules in 5-wave states are therefore generally associated from ultracold two-component spin mixtures. Interactions in all partial waves are obviously allowed if two different atomic species are involved, regardless of their fermionic or bosonic character. 

Monte Carlo Calculations for Coupled Boson-Fermion Systems. I. 

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