A collection of essays in which invited contributors attempt to define the nature of the electron, the quantum particle that has defied characterization for nearly a century.

**From the Editor\'s Preface:**

The electron is the first elementary particle, from both the physical and the historical point of view. It is the door to the microworld, to the physics of elementary particles and phenomena. This book is about electron models.

The year 1997 marked the centenary of the discovery of the electron as a particle by J.J. Thomson. We have already passed the centenary of Planck?s great discovery and the beginning of quantum physics; 2001 marked the 75^{th} anniversary of Schr?dinger?s equation and the beginning of quantum mechanics, while the year 2003 was the 75^{th} anniversary of the Dirac equation and Dirac?s model of the electron.

Today the most widely used theoretical approaches to the physics of the electron and atom are quantum mechanical and field theoretical models based on the non-relativistic Schr?dinger and the relativistic Dirac equations and their probabilistic interpretation. This is the basis of modern quantum field theory. More than 75 years is a long time for a physical theory! This theory is the basis for all contemporary calculations of physical phenomena.

After 75 years most physical theories tend to be supplanted by new theories, or to be modified. The theory?s successes, as well as its difficulties, are now evident to specialists. There is no proof of the uniqueness of the quantum field theory approach to the model of the electron and atom. Are other approaches possible? Quantum field theory may be sufficient to describe the electron, but is it necessary? This theory and its mathematics are very complicated; can we now propose a simpler construction? Is the electron an extended structure, a compound object made up of sub-particles, or is it a point-like elementary particle, which does not consist of any sub-particles? What is the limit of application of modern classical physics (based either on the corpuscular or wave model) in the description of the electron? These and many other questions remain without definitive answers, while experiments on quantum entanglement have given rise to new discussion and debate. New high-precision experimental data, *e.g.*, on the electric and magnetic dipole moments of the electron, may prove decisive.

This book, *What is the electron?*, brings together papers by a number of authors. The main purpose of the book is to present original papers containing new ideas about the electron. *What is the electron?* presents different points of view on the electron, both within the framework of quantum theory and from competing approaches. Original modern models and hypotheses, based on new principles, are well represented. A comparison of different viewpoints (sometimes orthogonal) will aid further development of the physics of the electron.

More than ten different models of the electron are presented here. More than twenty models are discussed briefly. Thus, the book gives a complete picture of contemporary theoretical thinking (traditional and new) about the physics of the electron.

It must be stressed that the vast majority of the authors do not appeal to quantum field theory, quantum mechanics or the probabilistic Copenhagen interpretation. The approaches adopted by these authors consist in using ?lighter? mathematics and a ?lighter? interpretation than in quantum theory. Some of them are sound approaches from the methodological point of view.

The editor will not presume to judge the models or the authors. We will not venture to say which model is better, and why. The reasons are simple. (i) Readers can reach their own conclusions themselves. (ii) Investigation of the electron is by no means finished. (iii) My own point of view is presented in my contribution to the book. So I want my paper to be on an equal footing with other new models of the electron presented here.

The general analysis of the electron models presented here shows that they can be classified as follows: corpuscular and wave, classical and quantum, point and extended, structureless and with structure. The reader can compare and ponder all these approaches! I would like to thank the authors for their contributions.

It is my hope that this volume will prove worthwhile for readers, and encourage them to pursue further investigation of electron models.

**Table of Contents:**

- Preface
- Jaime Keller - A Comprehensive Theory of the Electron from START
- Hidezumi Terazawa - The Electron in the Unified Composite Model of All Fundamental Particles and Forces
- Thomas E. Phipps, Jr. - Prospects for the Point Electron
- Martin Rivas - The Spinning Electron (http://tp.lc.ehu.es/documents/spinning.pdf)
- Claude Daviau - Relativistic Wave Equations, Clifford Algebras and Orthogonal Gauge Groups
- H. Sallhofer - What is the Electron?
- Volodimir Simulik - The Electron as a System of Classical Electromagnetic and Scalar Fields
- Malcolm H. Mac Gregor - What Causes the Electron to Weigh?
- Paolo Lanciani and Roberto Mignani - The Electron in a (3+3)-Dimensional Space-Time
- Vesselin Petkov - Can Studying the Inertial and Gravitational Properties of the Electron Provide us with an Insight into its Nature?
- Horace R. Drew - The Electron as a Periodic Waveform of Spin ? Symmetry
- Fabio Cardone, Alessio Marrani and Roberto Mignani - A Geometrical Meaning of Electron Mass from Breakdown of Lorentz Invariance
- Paramahamsa Tewari - On the Space-Vortex Structure of the Electron
- Milo Wolff and Geoff Haselhurst - Solving Nature\'s Mysteries: Structure of the Electron and Origin of Natural Laws
- William Gaede - Light: Neither Particle nor Transverse Wave
- Fran?oise Tibika-Apfelbaum - A Matter of Life? or Hypothesis on the Role of Electron Waves in Creating \"Order out of Chaos\"
- Adolphe Martin - The Electron as an Extended Structure in Cosmonic Gas