Field Theory reformulated without self-energy parts.Divergence-free classical electrodynamics

A manifestly gauge-invariant hamiltonian formulation of classical electrodynamics has been shown to be relativistic invariant by the construction of the adequate generators of the Poincare Lie algebra [Physica, 76, No. 3, 421-444 (1974)]. The original formulation in terms of reduced distribution functions for the particles and the fields is applied here to the case of two charges interacting through a classical electrodynamical field. On the other hand, we have been able in previous work to introduce irreversibility at the fundamental level of description [Ann. Phys., 311, 314-349 (2004)] by reformulating field theory without self-energy parts by integrating all processes associated with self-energy in a kinetic operator, while keeping the equivalence with the original description [Prog. Theor. Phys.,109, 881-909 (2003)]. In this paper, the two approaches are combined to provide a formalism that enables the use of methods of statistical physics to tackle the problem of the divergence of the self-mass. Our approach leads to expressions that are finite even for point-like charged particles: the limit of a infinite cutoff can be taken in an harmless way on self consistent equations. In order to check our theory, we recover the power dissipated by radiation in geometries where the usual mass divergence does not play a roleComment: 82 pages, submitted Annals of Physics, Interpretation revised completel

Field Theory reformulated without Self-energy Parts. The dressing Operator

The reformulation of field theory for avoiding self-energy parts in the dynamical evolution has been applied successfully in the framework of the Lee model, [M. de Haan. Ann. Phys., 311, 314-349 (2004)] enabling a kinetic extension of the description. The basic ingredient is the recognition of these self-energy parts. [M. de Haan and C. George. Trends in Statistical Physics 3 (2000), 115] The original reversible description is embedded in the new one and appears now as a restricted class of initial conditions. [M. de Haan and C. George. Prog. Theor. Phys.,109, 881-909 (2003)] This program is realized here in the reduced formalism for a scalar field, interacting with a two-level atom, beyond the usual rotating wave approximation. The kinetic evolution operator, previously surmised, [M. de Haan. Physica, A171 (1991), 159] is here derived from first principles, justifying the usual practice in optics where the common use of the so-called pole approximation should no longer be viewed as an approximation but as an alternative description in the appropriate formalism. That model illustrates how some dressing of the atomic levels (and vertices), through an appropriate operator, finds its place naturally into the new formalism since the bare and dressed ground states do no longer coincide. Moreover, finite velocity for field propagation is now possible in all cases, without the presence of precursors for multiple detections.Comment: 55 pages. Revised version for Annals of Physics. Typos and English corrections, references and precisions adde

Magnetisation reversal mechanism in Co-Cr media for perpendicular magnetic recording

In this study Co---Cr thin films with perpendicular anisotropy are investigated. Three films with values for Hc of 11, 90 and 170 kA/m have been selected for this paper. Besides the coercivily several other parameters such as the Hc/Hk, Cr-segregation, domain structure, column sizes, etc. were studied by VSM, SEM, NMR, MFM, AFM and selective etching. The anomalous Hall effect (AHE) has been used to record the hysteresis curves of submicron Hall crosses. This very sensitive technique in combination with e-beam lithography and ion-beam etching resulted in the recording of AHE hysteresis loops with dimensions of the Hall crosses as small as 0.3 × 0.3 ¿m2. The AHE loops of three samples, with less than 60 columns, show different micromagnetic properties. Only the sample with Hc1 = 90 kA/m shows clear steps in the curves above the noise level. The largest steps correspond with the reversal of one column and the total number of steps was five times the number of columns for this sample. The different reversal mechanisms observed by the AHE are related to the differences in structure, coercivity and domain size

Pension fund finance and sponsoring companies

Copyright © Cambridge University Press 2012.We present empirical evidence on the funding and portfolio allocation of around 200 Dutch corporate pension funds over the period 1996-2005, with a special focus on the influence of the sponsoring firm. We find that unprofitable and small firms contribute less to their pension funds than profitable and large firms, consistent with theories of capital market imperfections. Sponsor contributions are found to be positively correlated with leverage, suggesting that tax effects play a role. Defined benefit funds invest relatively more in equity and less in bonds than their defined contribution counterparts, which is in accordance with the risk shifting theory

Integrated and ecological nutrient management

This VEGINECO method manual is one of a series of publications resulting from the VEGINECO project. VEGINECO specialises in producing tested and improved multi-objective farming methods for key farming practices – e.g. crop rotation, fertilisation and crop protection – to facilitate the integration of potentially conflicting objectives like economy and ecology. This report describes a methodology for developing nutrient management strategies. In addition, examples of its application under different conditions in Europe are presented