We report on some conceptual changes in our present understanding of Quantum Field Theory and muse about possible consequences for the understanding of v > c signals.
Abstract Introduced as a quantum extension of Maxwell's classical theory, quantum electrodynamic (QED) has been the first example of a quantum field theory (QFT). Eventually, QFT has become the framework for the discussion of all fundamental interactions at the microscopic scale except, possibly, gravity. More surprisingly, it has also provided a framework for the understanding of second order phase transitions in statistical mechanics. In fact, as hopefully this work illustrates, QFT is the natural framework for the discussion of most systems involving an infinite number of degrees of freedom with local couplings. These systems range from cold Bose gases at the condensation temperature (about ten nanokelvin) to conventional phase transitions (from a few degrees to several hundred) and high energy particle physics up to a TeV, altogether more than twenty orders of magnitude in the energy scale. Therefore, although excellent textbooks about QFT had already been published, I thought, many years ago, that it might not be completely worthless to present a work in which the strong formal relations between particle physics and the theory of critical phenomena are systematically emphasized. This option explains some of the choices made in the presentation. A formulation in terms of field integrals has been adopted to study the properties of QFT. The language of partition and correlation functions has been used throughout, even in applications of QFT to particle physics. Renormalization and renormalization group (RG) properties are systematically discussed. The notion of effective field theory (EFT) and the emergence of renormalizable theories are described. The consequences for fine-tuning and triviality issue are emphasized. This fifth edition has been updated and fully revised.
Student research work in high school on the fundamental principles of quantum mechanics.Abstract:Quantum physics represents one of the most profound conceptual revolutions in modern science,redefining the foundations of matter, energy, and spacetime. This paper presents a structuredtheoretical examination of the development and implications of quantum mechanics, beginningwith the resolution of the ultraviolet catastrophe through energy quantization and extending tothe emergence of wave–particle duality, superposition, and intrinsic indeterminacy. By tracingthe contributions of Planck, Einstein, de Broglie, Schrödinger, Heisenberg, and Dirac, the workanalyzes the transition from classical determinism to probabilistic wave mechanics and thesubsequent formulation of quantum electrodynamics (QED) and quantum field theory (QFT).Particular attention is given to the conceptual shift from particles as localized objects toexcitations of underlying fields, providing a framework for understanding particle interactions,conservation laws, and the Standard Model of particle physics. The tension between quantummechanics and general relativity is examined through the unresolved problem of quantumgravity, highlighting the theoretical limitations that persist at singularities and Planck-scaleregimes. Rather than treating classical and quantum theories as irreconcilable domains, this studyconsiders their structural interplay and philosophical implications, emphasizing the need for aunified framework that coherently incorporates spacetime and quantization. The analysisprovides a qualitative synthesis intended to support future quantitative investigations intofundamental physics and the continued development of quantum technologies.