This SystemSix was in development for more than three and a half years. So an aero bike needs to find a balance between beating the wind, the conditions and the terrain without beating you up in the process. The way a bike handles and rides over a variety of surfaces and gradients, and in different conditions, has a major influence on overall speed averages. Now that’s a hard statement to prove or disprove, but in a recent independent test it did have the lowest drag figures in the wind tunnel (203w) compared to the Cervélo S5 (206w), Ridley Noah Fast (213w), Specialized Venge (208w) and Trek Madone (212w).ĭrag figures aren’t the be-all and end-all though. It is important to notice that the ground states of the Kondo lattice and the periodic Anderson model involve complicated effects, which cannot be understood by simple extension of the single- or two-impurity problem.Cannondale claims its new SystemSix is the fastest bike in the world. In this context various questions will be considered here: Does the Fermi surface include conduction electrons only or also the localized electrons? Does the concept of Luttinger liquid apply in this case? The extension of these results to higher dimensions is also discussed. While the former two phases are well understood, the physics of the paramagnetic phase is not worked out in detail yet. The paramagnetic phase may be considered as the generic heavy-fermion state and appears in the weak-coupling limit away from half filling. On the other hand, the half-filled Kondo lattice has a gap in both spin and charge excitations, i.e., it has a spin-liquid ground state. The ferromagnetic phase appears in the limit of low density of conduction electrons and for strong Kondo coupling away from half filling.
We present results on these phases obtained from rigorous and approximate analytical calculations supported by various extensive numerical studies on finite-size systems. The ground-state phase diagram for the one-dimensional Kondo lattice model is determined and shows three distinct phases: a ferromagnetic metallic, an insulating spin liquid, and a paramagnetic metallic state. In this review we summarize recent progress in the understanding of these models, in particular, the one-dimensional Kondo lattice model. These models are relevant for the so-called heavy-fermion and related systems such as the Kondo insulators. The periodic Anderson and Kondo lattice model describe the physics of conduction electrons in extended orbitals interacting with strongly correlated electrons in localized orbitals.
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