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Quantum Theory: Particles
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Quantum Field Theory (QFT) is the mathematical and conceptual framework for contemporary elementary particle physics. Since the very beginning of western philosophy reflections about the material world which go beyond the directly observable play a central role in philosophy. Starting with the presocratics it has always been a point of debate what the fundamental characteristics of the material world are. Is everything constantly changing or are there certain permanent features? What is basic and what is merely a matter of perspective and appearance? In the course of time various answers have been given and conflicting views have often been alternating in their predominance.
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Quantum field theory (QFT) is a theoretical framework for constructing quantum mechanical models of field-like systems or, equivalently, of many-body systems. It is widely used in particle physics and condensed matter physics. Most theories in modern particle physics, including the Standard Model of elementary particles and their interactions, are formulated as relativistic quantum field theories. In condensed matter physics, quantum field theories are used in many circumstances, especially those where the number of particles is allowed to fluctuate—for example, in the BCS theory of superconductivity.
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Quantum theory describes all of the fundamental forces—except gravitation—that physicists have found in nature. The forces that quantum theory describes are the electrical, the magnetic, the weak, and the strong. Physicists often refer to these forces as interactions, because the forces control the way particles interact with each other. Interactions ... affect spontaneous changes in isolated particles.
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Quantum Field Theory (QFT) is perhaps the single most important concept in physics to be discovered in the twentieth century. This volume reflects the multidimensional impact of QFT on the evolution of physics in the last century. Freeman Dyson, one of the architects of modern QFT, in a foreword to this volume has warmly endorsed this theme. This volume projects the central theme through a selection of invited articles in the areas where the impact of QFT has been especially pronounced, from particle physics to string theory (with several interpolating stages of development), and extending to some facets of astrophysics and the physics of condensed matter.
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Quantum Theory has shown that light is not just an electromagnetic wave behaves in some ways like a particle - the photon. This insight has produced the field of Quantum Optics, which has spawned the laser and optoelectronics. Applications to cryptography and computing are still in an experimental stage.
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Quantum theory ignited a scientific revolution 100 years ago, giving rise to paradoxical notions of lumpy light, wavelike particles and the disconnection of cause and effect. Leading physicists were among those who debated the theory at a 1927 congress in Brussels. The discussion continues in Berlin this week.
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