Core-induced chaos in diamagnetic lithium.
We present a theoretical study of the connections between quantum and classical descriptions of lithium in a magnetic field. We find that the localized nature of the ionic core causes a breakdown in the generic connections between energy-level statistics and classical motion: classical chaos is observed in a regime where the energy-level distribution is Poissonian. The breakdown arises because the source of chaos is localized on a node of the odd-parity wave function. In addition, we employ the principles of periodic-orbit theory to identify classical trajectories with spectral periodicities. We identify a series of core-scattered recurrences in the Fourier transform of the spectrum and quantitatively describe them by a simple model. Finally, we introduce recurrence counting and demonstrate how it can help relate the classical dynamics to the quantum spectrum. \textcopyright{} 1996 The American Physical Society.
The dependence of the differential cross section ${\mathrm{d}\sigma}/{\mathrm{d}p_{\perp}}$ of inclusive heavy quark production in pp and $\bar{\mathrm{p}}$p collisions on the renormalization and factorization scales is investigated. The implications of our results for experiments at TEVATRON and LHC are discussed. In particular, it is shown that the NLO QCD predictions for $\bar{t}t$ production at the LHC based on the Principle of Minimal Sensitivity are by 30-50% higher than the standard ones.