Preface

A century and a half after the formulation of Maxwell's equations, electromagnetism is a domain in spectacular expansion, incorporating continuously the progress in fundamental and applicative physics, from relativity to materials science, and responding, in this way, to the challenges of the modern world.

The present book provides 12 review papers on recent developments in electromagnetism, from fundamentals to electrical engineering. They are grouped in four sections, as follows.

The first one covers fundamental problems of electromagnetic theory.

In van Kampen's paper, linear charge and currents distributions make possible to introduce the main concepts of electromagnetism without use of vector calculus. Special relativity is invoked to demonstrate that electricity and magnetism are, in a sense, two different ways of looking at the same phenomenon: in principle, from either electricity or magnetism and special relativity, the third theory could be derived.

Starting with the standard Maxwell's equations, Ni's paper presents the different types of quantum corrections, and the corresponding equations for nonlinear electrodynamics.

The electromagnetism in curved spaces and the Einstein equivalence principle, together with the different experimental results for the cosmic polarization rotation, are discussed.

In his chapter, Kitano reformulates the electromagnetic theory using differential forms, by taking into consideration the physical perspective, the unit system (physical dimensions), and the geometrical aspects. In this way, he provides a unified, clear and original view of electromagnetism.

The second section is devoted to the interconnections between electromagnetism and quantum and thermal physics.

The topological model of electromagnetism constructed with electromagnetic knots is presented in Ranada's paper. It puts in a new light the classical and quantum aspects

#### X Preface

of the electromagnetic theory, treats electricity and magnetism symmetrically, and gives a theoretical explanation for the quantization of the magnetic flux in superconductors.

Preface XI

magnetic materials to be used, to the multitude of systems created in various laboratories. Detailed numerical studies of the refrigeration effect are done for

Several applications of metamaterials in antenna engineering are exposed in Movahhedi's and Veysi's contributions. In the first paper, the authors propose new backward and forward coupling line couplers with high coupling levels, broad bandwidth and compact sizes. In the second, the possibility of increasing both antenna

**Dr. Victor Barsan**

**Prof. Radu P. Lungu** University of Bucharest,

Bucharest, Romania

Romania

Center for Nuclear Physics IFIN-HH,

National Institute of Physics and Nuclear Engineering,

different geometries, devices, systems and materials.

bandwidth and directivity using metamaterial covers is examined.

As the time-independent wave equations for the classical electric and magnetic field, and for the wave function for a quantum particle, are similar, an interesting analogy can be developed between electromagnetic wave propagation in waveguides, ballistic electron transport in mesoscopic conductors and light propagation in optical fibres. These issues are addressed in Barsan's review.

In Lungu's review, the different types of the thermodynamic potentials of electric and magnetic systems are rigorously derived, starting from the principles of thermodynamics and Maxwell equations. From the general expressions of the potentials, the equations of state and the thermodynamic coefficients are deduced. Finally, using the results previously obtained, some important thermodynamic processes are discussed.

The next section puts together three important problems of electromagnetism – scattering of electromagnetic waves, electromagnetic compatibility and liquid metal flow in strong magnetic fields - treated with numerical methods.

An accurate numerical solution of electromagnetic scattering problems is critically demanded in the simulation of industrial processes and in the study of wave propagation phenomena. Modern techniques use the integral equations to reformulate Maxwell's equations for electric and magnetic fields on the surface of the object. These equations are solved in Carpentieri's contribution, using recent progress in numerical analysis.

The electromagnetic compatibility, i.e. the need of avoiding undesirable effects of electromagnetic interference due to the simultaneous functioning of several electric devices in the same area, is addressed in El Baba's paper. The backward propagation of electromagnetic waves, based on the time reversal invariance of the electromagnetic wave equation, is the starting point of a detailed numerical study of the parasitic electromagnetic fields, in various geometries and environments.

Exact characterization of the liquid-metal lithium passing through a strong magnetic field, which is used in order to confine the high-temperature reacting plasma in a fusion reactor core, is essential for the evaluation of the heat transfer in such a complex device. A 3D calculation is crucial for the precise evaluation of magneto-hydrodynamic flow in the inlet or outlet region of the magnetic field. Such a calculation, attentively discussed and interpreted, is presented in Kumamuru's chapter.

The last section is devoted to applicative issues, starting with magnetic refrigeration technology at room temperature. The ultimate goal of this emerging technology is to develop a standard refrigerator for home use, using the magnetocaloric effect. Bouchekara's chapter describes the magnetic refrigeration technology, from modern magnetic materials to be used, to the multitude of systems created in various laboratories. Detailed numerical studies of the refrigeration effect are done for different geometries, devices, systems and materials.

X Preface

superconductors.

processes are discussed.

analysis.

These issues are addressed in Barsan's review.

of the electromagnetic theory, treats electricity and magnetism symmetrically, and gives a theoretical explanation for the quantization of the magnetic flux in

As the time-independent wave equations for the classical electric and magnetic field, and for the wave function for a quantum particle, are similar, an interesting analogy can be developed between electromagnetic wave propagation in waveguides, ballistic electron transport in mesoscopic conductors and light propagation in optical fibres.

In Lungu's review, the different types of the thermodynamic potentials of electric and magnetic systems are rigorously derived, starting from the principles of thermodynamics and Maxwell equations. From the general expressions of the potentials, the equations of state and the thermodynamic coefficients are deduced. Finally, using the results previously obtained, some important thermodynamic

The next section puts together three important problems of electromagnetism – scattering of electromagnetic waves, electromagnetic compatibility and liquid metal

An accurate numerical solution of electromagnetic scattering problems is critically demanded in the simulation of industrial processes and in the study of wave propagation phenomena. Modern techniques use the integral equations to reformulate Maxwell's equations for electric and magnetic fields on the surface of the object. These equations are solved in Carpentieri's contribution, using recent progress in numerical

The electromagnetic compatibility, i.e. the need of avoiding undesirable effects of electromagnetic interference due to the simultaneous functioning of several electric devices in the same area, is addressed in El Baba's paper. The backward propagation of electromagnetic waves, based on the time reversal invariance of the electromagnetic wave equation, is the starting point of a detailed numerical study of the parasitic

Exact characterization of the liquid-metal lithium passing through a strong magnetic field, which is used in order to confine the high-temperature reacting plasma in a fusion reactor core, is essential for the evaluation of the heat transfer in such a complex device. A 3D calculation is crucial for the precise evaluation of magneto-hydrodynamic flow in the inlet or outlet region of the magnetic field. Such a calculation,

The last section is devoted to applicative issues, starting with magnetic refrigeration technology at room temperature. The ultimate goal of this emerging technology is to develop a standard refrigerator for home use, using the magnetocaloric effect. Bouchekara's chapter describes the magnetic refrigeration technology, from modern

attentively discussed and interpreted, is presented in Kumamuru's chapter.

flow in strong magnetic fields - treated with numerical methods.

electromagnetic fields, in various geometries and environments.

Several applications of metamaterials in antenna engineering are exposed in Movahhedi's and Veysi's contributions. In the first paper, the authors propose new backward and forward coupling line couplers with high coupling levels, broad bandwidth and compact sizes. In the second, the possibility of increasing both antenna bandwidth and directivity using metamaterial covers is examined.

> **Dr. Victor Barsan** Center for Nuclear Physics IFIN-HH, National Institute of Physics and Nuclear Engineering, Bucharest, Romania

> > **Prof. Radu P. Lungu** University of Bucharest, Romania

**Part 1** 

**Fundamentals** 
