Classical electrodynamics of point charges

A simple mathematical procedure is introduced which allows redefining in an exact way divergent integrals and limits that appear in the basic equations of classical electrodynamics with point charges. In this way all divergences are at once removed without affecting the locality and the relativistic covariance of the theory, and with no need for mass renormalization. The procedure is first used to obtain a finite expression for the electromagnetic energy-momentum of the system. We show that the relativistic Lorentz-Dirac equation can be deduced from the conservation of this electromagnetic energy-momentum plus the usual mechanical term. Then we derive a finite lagrangian, which depends on the particle variables and on the actual electromagnetic potentials at a given time. From this lagrangian the equations of motion of both particles and fields can be derived via Hamilton's variational principle. The hamiltonian formulation of the theory can be obtained in a straightforward way. This leads to an interesting comparison between the resulting divergence-free expression of the hamiltonian functional and the standard renormalization rules for perturbative quantum electrodynamics.Comment: 46 pages, REVTeX . Revised version with added comments and reference

IT-toepassingen in de gezondheidszorg - Bewezen procesverbeteringen in het ziekenhuis.

In this thesis we tried to answer the following research question: “What are the proven effects of IT applications with respect to how they increase efficiency in health care processes?" To answer this question we searched for IT applications which claim to increase the efficiency of health care processes. Today, many IT applications are used in hospitals, but not all of them were suitable to study in this thesis. Therefore we selected four IT applications (EHR, CDSS, CPOE and Scheduling) to investigate. Our research consisted of two parts, first an intensive literature study. Second, we interviewed several IT application suppliers. We compared the results of those two studies to come up with final conclusions. The main problem we tried to investigate in this study is the strength of proof which can be given for some of the claimed effects of the selected IT applications which are applied in hospital environments. From our literature study it appears that only a small amount of effects have been reasonably proven, most of them are bared on just a meager amount of prove. This thesis gives an indication of the current state of the art with respect to available research in this area. The main finding from this thesis is that the increase of efficiency of health care processes due to the use of IT applications has not been proven in literature. Only a few effects have been reasonably proven according to the literature study, most effects have a poor amount of prove. However, the fact that there is no strong proof doesn't mean that the concerning effects will not occur at all, there is just not enough evidence to draw the conclusion that they do occur. The results from this study are, among others, that the impression has been given that health care in general hasn't much interest in checking what the results are from IT applications. This is strange considering that these IT applications get more and more functions which no longer concern just making letters, but also involve critical processes and sensitive information

Hamiltonian Formulation of Two Body Problem in Wheeler-Feynman electrodynamics

A Hamiltonian formulation for the classical problem of electromagnetic interaction of two charged relativistic particles is found.Comment: 22 pages, 8 Uuencoded Postscript figure

A Review of Numerical Simulation Strategies for Hydraulic Fracturing, Natural Fracture Reactivation and Induced Microseismicity Prediction

Hydraulic fracturing, natural fracture reactivation and resulting induced microseismicity are interconnected phenomena involved in shale gas exploitation. Due to their multi-physics and their complexity, deep understanding of these phenomena as well as their mutual interaction require the adoption of coupled mechanical and fluid flow approaches. Modeling these systems is a challenging procedure as the involved processes take place on different scales of space and also require adequate multidisciplinary knowledge. An extensive literature review is presented here to provide knowledge on the modeling approaches adopted for these coupled problems. The review is intended as a guide to select effective modeling approaches for problems of different complexit

Quantum-classical crossover in electrodynamics

A classical field theory is proposed for the electric current and the electromagnetic field interpolating between microscopic and macroscopic domains. It represents a generalization of the density functional for the dynamics of the current and the electromagnetic field in the quantum side of the crossover and reproduces standard classical electrodynamics on the other side. The effective action derived in the closed time path formalism and the equations of motion follow from the variational principle. The polarization of the Dirac-see can be taken into account in the quadratic approximation of the action by the introduction of the deplacement field strengths as in conventional classical electrodynamics. Decoherence appears naturally as a simple one-loop effect in this formalism. It is argued that the radiation time arrow is generated from the quantum boundary conditions in time by decoherence at the quantum-classical crossover and the Abraham-Lorentz force arises from the accelerating charge or from other charges in the macroscopic or the microscopic side, respectively. The functional form of quantum renormalization group, the generalization of the renormalization group method for the density matrix, is proposed to follow the scale dependence through the quantum-classical crossover in a systematical manner.Comment: new references added, few sign errors fixed, to appear in Physical Review

Effects of fault transmissivity on the potential of fault reactivation and induced seismicity : Implications for understanding induced seismicity at Pohang EGS

Funding Information: The project leading to part of the results in this article received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691728 .Peer reviewedPublisher PD

Self-organization in a phonon laser

We make an adaptation of laser modelling equations to describe the behavior of a phonon laser (saser). Our saser consists of an AlGaAs/GaAs double barrier heterostructure designed to generate an intense beam of transversal acoustic (TA) phonons. To study our system, we begin with a Hamiltonian that describes the decay of primary longitudinal optical phonons (LO_1) into secondary (LO_2) and TA (LO_1 -> LO_2 + TA) and its inverse process (recombination). Using this Hamiltonian, a set of coupled equations of motion for the phonons is obtained. We also consider the interaction between the phonons and its reservoirs. These interactions are introduced in the equations of motion leading to a set of coupled Langevin equations. In order to obtain an expression to describe our saser we apply, in the Langevin equations, an adiabatic elimination of some variables of the subsystem. Following the method above we obtain the value of the injection threshold for the operation of our phonon laser. At this threshold occurs a phase transition from a disordered to a coherent state. It is shown that it is not necessary a big "optical" pumping to get a sasing region.Comment: 4 figure

Time evolution of relativistic d + Au and Au + Au collisions

The evolution of charged-particle production in collisions of heavy ions at relativistic energies is investigated as function of centrality in a nonequilibrium-statistical framework. Precise agreement with recent d + Au and Au + Au data at sqrt(s_NN) = 200 GeV is found in a Relativistic Diffusion Model with three sources for particle production. Only the midrapidity source comes very close to local equilibrium, whereas the analyses of the overall pseudorapidity distributions show that the systems remain far from statistical equilibrium.Comment: 16 pages, 5 figures, 1 tabl

A demonstration of Tribler : peer-to-peer television

The success of Peer-to-Peer Television (P2P-TV) systems depends on the inducement of users to cooperate massively and voluntarily. To operationalize our proposed applications of incentives based on psychological backgrounds, we discuss a demonstration of our own P2P-TV system called Tribler. It is a system for downloading, video-on-demand (VoD), and live streaming of Television content. This paper discusses the demonstration of Tribler version 4.0 as the first operationalization of relevant psychological backgrounds