propagator


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Propagator (field theory)

The probability amplitude for a particle to move or propagate to some new point of space and time when its amplitude at some point of origination is known. The propagator occurs as an important part of the probability in reactions and interactions in all branches of modern physics. Its properties are best described in the framework of quantum field theory for relativistic particles, where it is written in terms of energy and momentum. Concrete examples for electron-proton and proton-proton scattering are provided in the illustration. The amplitude for these processes contains the propagators for the exchanged proton and meson, which actually specify the dominant part of the probability of each process when the scattering occurs at small angles. In similar fashion, for any electromagnetic process, a propagator for each internal line of the Feynman diagram (each line not connected directly to the outside world) enters the probability amplitude. See Feynman diagram, Quantum electrodynamics, Quantum field theory, Quantum mechanics

Feynman diagrams for scattering processesenlarge picture
Feynman diagrams for scattering processes

propagator

[′präp·ə‚gād·ər]
(quantum mechanics)
The probability amplitude for a particle to move or propagate to some new point of space and time when its amplitude at some point of origination is known.
References in periodicals archive ?
which specifies the propagators of electromagnetic, Z-, [W.
Heller and Tomsovic's version of the Van Vleck propagator, however, is more than simply a faster way of computing a system's quantum properties.
Courgettes, melons and sunflowers, for example, are traditionally sown late and can't be planted out in the garden until the end of May or beginning of June, so they won't benefit from being germinated in a heated propagator early because you'll still have to keep them indoors.
Things such as staging, propagators, watering systems and automatic vent openers, plus blinds, heaters and insulation will also rack up the costs.
It all depends on whether you have somewhere to put your seedlings when they come out of the propagator.
Place the potted cuttings in a propagator if you have one with a gentle base heat and water in.
Only use F1 hybrids as they are more vigorous, and keep your propagator at 20C.
TOP BUYS: A spade, hosepipe spray gun, seed kit, propagator and expert book
Sow tomato seeds in a heated propagator or on a warm windowsill but don''t plant outdoors until all danger of frost has passed.
Remember you can sow greenhouse tomatoes in a heated propagator as early as December
Take cuttings of new shoots of camellias, rooting them in a covered propagator.
CONTINUE to plant summer-flowering bulbs; Prune plum trees once they have started growing; Don't let pots and seed trays in the greenhouse dry out; Prune spring-flowering shrubs more than three-years-old as they finish flowering; Sow sweet peas directly into their flowering position; Sow tomato seeds in a heated propagator or on a warm windowsill to grow outdoors when risk of frost has passed; Plant sprouted tubers of early varieties of potato; Remove the ends of shoots on shrubs damaged by frost; Feed climbers with a slow-acting general fertiliser around all established plants; Check borders for plant losses and plan how you are going to fill the gaps.