Customer Reviews
Quantum Electrodynamics (QED) made easy - By: Rama Rao, 11 Dec 2008 
The author is one of the greatest physicists of 20th century, & highly regarded as one of the best instructors of physics, but the reader must have some knowledge of science & strong interestin physics, & appreciate optical phenomenon; reflection of light, refraction, etc. Reading this book at first may be boring, but reading for second or third time gives you a good idea about the theory & help you understand the elegance with which the author has conveyed the material. Quantum Electrodynamics (QED) is a fundamental theory of light (photon) - matter (particle) interaction or electric field & charge interaction. The author explains how we can calculate this interaction. There are only three basic actions associated with light & electron interaction. First, a photon goes from place to place; second, an electron goes from place to place; & third, an electron emits or absorbs a photon. Each of this has amplitude - an arrow (vector) that can be calculated according to certain rules. There is no mathematicsin the book but the logic, & assumptions are explained which may be difficult to assimilate unless you like to understand QED.
When an electron travels from one point to anotherin spacetime, it uses multiple paths before arriving at its destination according to quantum physics. It can also absorb or emit light multiple times during its path. Therefore one needs to calculate the probability of its most likely path & also the number of times it absorbs or emits radiation. Emission of light could occur when an electron interacts with positrons (antiparticle) that resultsin their annihilation. QED incorporates corrections to one or more photons being emitted & absorbedin its path & also all other possible paths the electron may take. All these are considered to calculate the mist likely path for its travel.
The second factor to be includedin the calculation is that light has amplitude to go faster or slower than the conventional speed of light. Therefore the emission & absorption of light between two electrons could occur with three possibilities. One, the emission occurs before absorption, second, emission occurs at the same time as absorption, & third, emission occurs after absorption. The last possibility looks puzzling since light is required to go backwardsin time. This is possiblein mathematical calculations, & photons are said to be exchanged & the locations are usedin spacetimein the formula. Additional possibilities to consider are; two & more photon exchange could occur. If we consider the effect polarization, the coupling factor j for backward moving electron is positive, hence the charge is positive & the electron is referred to as positron.
The formula calculates two numbers known as n (mass for a fake electron) & j (coupling parameter; charge of a fake electron). For a real electron, n = mass experimentally determined, & j = charge experimentally determined. The author explains the complexitiesin the calculation of these two numbers which are usedin the formula that calculates the amplitude of electron - photon interactions.
For an atom which contains a nucleus at the center & electronin the orbit; nucleus is heavy & hence considered stationary & the electron movesin spacetime with respect to nucleusin the QED analysis. The dynamics include; electrons & nucleus exchange photons, & the photons from outside is scattered by the electron of the atom. The total amplitude of all electron scattering depends on the arrangement of electronsin the atom & they are variously called s, p, d & f orbitals that accounts for the entire chemistry & chemical reactions of elements.
1. Quantum Electrodynamics (Advanced Book Program)
2. Molecular Quantum Electrodynamics
3. Introductory quantum electrodynamics (Mathematical physics series;no.4)
Awesome, concise, brilliant............... - By: Raja Hussain, 26 Feb 2007 One of the best physics reads i have come across, well written, well put together, & best of all, it makes sense, assisted by well annotated diagrams on nearly every conceptin the book, you can really get a sense of these being a collection of lectures, its as if Feynman is talking to you himself.
Must get for any physics buff.
