Path integral formulation

[cragar]

does the multi Path integral formulation violate special relativity ! do we get speeds faster than c.

[zetafunction]

the particles with speed greater than 'c' are no physical particles they have no meaning at all, i think they are introduced just as a mathematical trick to make thing converge.

[feynmann]

does the multi Path integral formulation violate special relativity ! do we get speeds faster than c.

What speed are you talking about? Group speed or phase speed?

[Fredrik]

What speed are you talking about? Group speed or phase speed?
Neither. He's talking about path integrals, which add up the probability amplitudes associated with each classical path, and some of those paths correspond to speeds >c.

The answers to the questions in #1 are "no" and "yes". To "violate" SR you'd have to be able to send a message with a speed greater than c. You can't do it just by breaking a mathematical expression into pieces and interpreting some of the pieces as speeds >c.

the particles with speed greater than 'c' are no physical particles they have no meaning at all, i think they are introduced just as a mathematical trick to make thing converge.
They are no less and no more real than the ones with speed less than c, and this doesn't have anything to do with convergence.

[cragar]

i see