A. Neumaier said:
A. Neumaier said:
A. Neumaier said:
dtail ##\to## detail[URL='https://www.physicsforums.com/insights/author/urs-schreiber/']Urs Schreiber[/URL] said:
A. Neumaier said:
You can define macros in mathJax as in LaTeX, using the usual \newcommand command within a math environment. The only drawback is that you get some empty lines, where you place this. I couldn't figure out how to give plain html commands yet. Using plain html you can avoid the blank lines by setting the \newcommand definitions within a paragraph cf. <p style="display:none">...</p>.[URL='https://www.physicsforums.com/insights/author/urs-schreiber/']Urs Schreiber[/URL] said:
vanhees71 said:
A propagator in mathematical quantum field theory is a mathematical function that describes the probability amplitude for a particle to travel from one point in spacetime to another. It is a fundamental concept in quantum field theory, used to calculate the probability of interactions between particles.
Propagators are closely related to Feynman diagrams, which are graphical representations of particle interactions in quantum field theory. Each line in a Feynman diagram represents a propagator, showing the path of a particle from one vertex to another.
Yes, propagators are used in quantum field theory calculations to calculate physical observables such as scattering cross sections and decay rates. They provide a mathematical framework for predicting the outcomes of particle interactions.
Propagators have several important properties, including Lorentz invariance, causality, and unitarity. Lorentz invariance means that the propagator is invariant under transformations of spacetime coordinates. Causality means that the propagator only describes the propagation of particles forward in time. Unitarity requires that the sum of all possible intermediate states in a propagator calculation must equal 1.
Propagators have many applications in quantum field theory, including calculating scattering processes, determining the behavior of particles in external fields, and understanding the behavior of particles at high energies. They are also used in the study of quantum field theories in curved spacetime, such as in cosmology and black hole physics.
