دانلود کتاب رویکرد مفهومی به الکترودینامیک کوانتومی

Since I was a student, I always wished for a single, comprehensive book to revisit previously learned subjects that tend to fade over time. Motivated by this desire, I aimed to write a book that consolidates essential physical concepts and fundamental laws of physics, enriched by deeper conceptual explanations than typically found in undergraduate textbooks. The primary purpose of this book is to provide an accessible introduction for incoming graduate students, guiding them through the evolution of quantum field theory, in particular, quantum electrodynamics (QED). It emphasizes the conceptual growth of the theory within the broader human quest to unravel the mysteries of the universe. To fulfill this long-standing ambition, I have reviewed crucial topics comprehensively, presenting fundamental equations alongside their conceptual significance in the context of QED. This text serves as a practical resource, helping beginners refresh their existing knowledge and bridge any gaps in their understanding. Essential mathematical relationships are revisited to establish a solid technical foundation, complemented by reviews of electromagnetism, quantum mechanics, relativity, and high-energy physics, all crucial for grasping quantum field theory. Following the exploration of quantum field theory’s development and a brief introduction to QED, this book further highlights the significance of QED in applied physics, illustrating its importance in technological advancement and innovation. Vector quantities are defined by their magnitudes and directions. A complete set of orthogonal unit vectors or basis vectors generate a vector space. Each vector in a vector space is expressed as a linear combination of all the components represented by the orthogonal basis vectors. Vector spaces are generated by a complete set of mutually independent basis vectors and the components of vectors along the basis vectors are called coordinates. Each component of a vector corresponds to a basis vector of the corresponding vector space, whereas the same vector in another vector space (coordinate system) is described with a different set of components in terms of the corresponding basis vectors without changing the magnitude of the original vector. Therefore, vectors can be transformed from one coordinate system to another coordinate system by transformation of each and every component without changing their magnitudes. The magnitude of a vector can always be calculated from the square root of the sum of squares of each component in a particular vector space. These vectors can be transformed to other vectors when operated or multiplied with an appropriate transformation square matrix. Multiplication with a square matrix transforms one vector into another vector (e.g., rotation) or transforms from one to another vector space (e.g., Cartesian to spherical polar coordinates). Properties of the transformation matrices determine the properties of the vector space as well. A set of all the transformation matrices of a vector space can make a group if it makes a closed set including an identity matrix and if every matrix has an inverse. A group of unitary matrices corresponds to a fundamental interaction as it satisfies the requirements of conservative forces as well.