Not really. Electrons have non-zero invariant mass, whereas a photon's is 0.exponent137 said:An electron and a photon are too similar in QED.
This is true, it is seen in propagator like [itex]1/(m^2+p^2)[/itex].strangerep said:Not really. Electrons have non-zero invariant mass, whereas a photon's is 0.
exponent137 said:Special relativity gives that time for a (traveler on) photon do not run. It also gives that every moving elementary particle rest in some inertial system, but photon does not rest in any inertial system.
But how this can be visible in Quantum field theory or in QED? An electron and a photon are too similar in QED.
That depends on which textbook you're reading. (You didn't which textbooks you've studied).exponent137 said:But it is not enough explained, how physics with m and without m in propagator is different? It is also not enough explained how calculations are essentially different?
Photons have zero invariant mass. In modern textbooks, both massive and massless fields are constructed as representations of the Poincare group. The older terminology of "particle" is gradually being replaced by "field".Neandethal00 said:If photons have no mass then why do we treat them as particles?
It's misleading to say that a photon "is" a form of energy. A more accurate picture is that a photon field has both energy and momentum.A photon probably is a form of energy, not a particle.
What you describe is called the "relativistic mass", which is a distinct concept from "invariant mass". (Both can be useful in different circumstances.)The best we can do is give it a theoretical mass as
Energy equivalent of photon mass = m(photon) = hf/(c2).
Will it then run into trouble with Relativity?
It does, but not in a Lorentz inertial system. It is at rest in a light-cone inertial system. The coordinate transformation from Lorentz coordinates x, t to light-cone coordinates x', t' isexponent137 said:but photon does not rest in any inertial system.
The concept of time in quantum field theory (QFT) and special relativity is that time is relative and not absolute. In QFT, time is considered as a coordinate in a mathematical framework that describes the behavior of particles and fields. In special relativity, time is also relative and is influenced by the observer's frame of reference.
Time dilation is a phenomenon predicted by special relativity where time appears to pass slower for an observer in a moving frame of reference compared to an observer in a stationary frame of reference. This is due to the fact that the speed of light is constant and the concept of simultaneity changes for observers in different frames of reference.
In QFT and special relativity, time and space are considered as one entity called spacetime. This means that they are interconnected and cannot be separated. The way time and space are perceived by an observer depends on their relative motion and is described by the Lorentz transformation equations.
In QFT and special relativity, time is considered as a dimension in spacetime that is continuous and has no beginning or end. It is a fundamental aspect of the universe and cannot be fully understood or described without considering its relation to space.
In classical physics, time is considered as absolute and universal, meaning that it is the same for all observers. However, in QFT and special relativity, time is relative and depends on the observer's frame of reference. Additionally, QFT takes into account the effects of quantum mechanics, which can cause time to behave in unexpected ways at the subatomic level.