Library of Congress Cataloging•in•Publication Data. Atoms in strong magnetic fields: quantum mechanical treatment and applications in astrophysics and quantum chaos 1 H. Ruder ... [et al.]. p. cm. Includes bibliographical references and index. \. Atomic transition probabilities. 2. Stars-Magnetic fields. 3. White dwarfs. 4. Neutron stars. 5. Quantum chaos.

The energy values of many low-lying states of the one-electron problem in the presence of a homogeneous magnetic field of arbitrary strength (0<B<or=4.7*108 T) are calculated with high numerical accuracy for a sufficiently dense mesh of B. The wavefunctions are expanded either in terms of spherical harmonics (weak and moderate fields) or in terms of Landau states (strong and very strong fields), with r- or z-dependent expansion functions that are determined with the use of an adopted version of the MCHF code of Froese Fischer (1978). At intermediate field strengths up to 24 expansion terms are included. The structural change of the wavefunctions with magnetic field is discussed quantitatively for a few representative states. As an application, the splittings of the components of the Lyman- alpha , beta , and the Balmer- alpha lines of the hydrogen atom are presented (including the effects of the finite proton mass) as continuous functions of the field strength over the whole range of B considered.

No abstract

No abstract

No abstract

No abstract

To test the lambda-model version of the equilibrium point hypothesis both for feasibility and validity with respect to the control of terrestrial locomotion, we developed a two-dimensional, eleven-segment musculoskeletal model of the human body including 14 muscle-tendon complexes per leg, three-segment feet, and a physiologically based model of foot-ground interaction. Human walking was synthesized by numerical integration of the coupled muscle-tendon and rigid body dynamics. To this end a control algorithm based on the lambda-model was implemented in the model providing muscle stimulation patterns that guaranteed dynamically stable walking including a balanced trunk. Thus, the timing of the movement is not preset by a central pattern generator but emerges from the interaction of the musculoskeletal system with the control algorithm. The control parameters were found in a trial-and-error approach. The feedforward part of the control scheme consists of just two target configurations each of which is composed of a set of one nominal length per muscle (lambda-model). Variation of gravity reveals that (1) the synthesized walking patterns are close to ballistic walking and (2) this muscularly induced natural walking can only be initiated and maintained in the range between about a tenth and three times earth-bound gravity. Our walking patterns are robust both against parameter variations and shuffling of the swing leg. We discuss our model with respect to gravity scaling, speed control, feedback delay, and the terms "equilibrium point hypothesis" and "central pattern generator."

Recently it was pointed out by Shabad and Usov that in the vicinity of pulsars high-energy photons can be captured by the strong magnetic field without creating pairs. We have reconsidered this process and find that the captured "photon" is transformed into bound positronium. This positronium can be ionized by the intense electric fields present in the polar cap region, or by thermal radiation from the neutron star surface, whereby the free electrons and positrons are regained that are urgently required for the models of pulsar radio emission.