Quantum Fields and Particles, Gauge Theories and Strings

Extension of QT to the relativistic regime led to the celebrated Dirac equation predicting the existence of anti-matter and called for a theoretical description of a multi-particle theory which accounts for the exchange that takes between energy and matter and the creation of an unlimited number of particles, giving birth to modern QFT. The necessity of eliminating parameters in QFT pertaining to inaccessible measurements at extreme high energies, corresponding to absolute zero distances, in favor of physically accessible measurable quantities, led to the birth of renormalization theory and modern QED. High energy electron-nucleon scattering confirmed and shaped the development of QCD. The non-damping high energy behavior of massive vector bosons propagators led to the necessity of developing the Higgs mechanism giving birth to the electro-weak and the SM of particle physics. SUSY, as a symmetry between fermions and bosons, led to a better grand unification of the SM at high energies, and contributed in solving the Higgs mass problem. String theory with string of order of Planck length, corresponding to Planck energy, as a QFT in 2 dimensional, string generated, surface with remarkable consequences in spacetime, produces the graviton and other particles and re-invents GR and Yang-Mills field theory.