On Monday, August 26, 2019 at 10:55:23 PM UTC-6, Brent wrote: > > > > On 8/26/2019 8:48 PM, Alan Grayson wrote: > > > > On Monday, August 26, 2019 at 9:18:50 PM UTC-6, Bruce wrote: >> >> On Tue, Aug 27, 2019 at 12:40 PM Jason Resch <[email protected]> wrote: >> >>> On Mon, Aug 26, 2019 at 9:25 PM Bruce Kellett <[email protected]> >>> wrote: >>> >>>> On Tue, Aug 27, 2019 at 10:35 AM Jason Resch <[email protected]> >>>> wrote: >>>> >>>>> On Mon, Aug 26, 2019 at 7:32 PM Bruce Kellett <[email protected]> >>>>> wrote: >>>>> >>>>>> On Tue, Aug 27, 2019 at 10:27 AM Jason Resch <[email protected]> >>>>>> wrote: >>>>>> >>>>>>> These videos provide a good introduction: >>>>>>> >>>>>>> https://www.youtube.com/watch?v=X5rAGfjPSWE >>>>>>> https://www.youtube.com/watch?v=fG52mXN-uWI >>>>>>> >>>>>>> Virtual particles are the basis of all particle interactions in QED, >>>>>>> called the jewel of physics for having made the most accurate >>>>>>> predictions >>>>>>> of any physical theory. >>>>>>> >>>>>> >>>>>> The trouble is that virtual particles are internal lines in Feynman >>>>>> diagrams, and the Feynman diagrams are formed as a perturbation >>>>>> expansion. >>>>>> They have to be summed to make contact with physical processes. This >>>>>> puts >>>>>> the status of virtual particles, as ontological entities, into >>>>>> considerable >>>>>> doubt. Ultimately, they are nothing but a calculational device, and >>>>>> quantum >>>>>> amplitudes can be evaluated without ever using Feynman diagrams, so >>>>>> virtual >>>>>> particles need never appear anywhere. >>>>>> >>>>>> >>>>> But this "calculational device" (funny how many things are mere >>>>> devices) predicts the lamb shift as well as the Casimir effect, to great >>>>> accuracy. >>>>> >>>> >>>> No, virtual particles do not predict the Lamb shift -- they are just an >>>> aid to calculating terms in the perturbation expansion of the QED vertex >>>> function. >>>> >>>> >>> Is this answer in error? >>> https://physics.stackexchange.com/questions/443186/lamb-shift-and-virtual-particles >>> >>> >> >> No, that seems to give the standard Feynman diagrams for radiative >> corrections to the photon propagator. (I misremembered previously. >> Radiative corrections to the vertex function are important for the >> calculation of g-2 for the electron, not for the Lamb shift, which is a >> photon propagator correction.) But the standard calculation says nothing >> about reifying the internal lines in the diagrams. In fact, a good >> approximation to the Lamb shift can be obtained from a simple >> non-relativistic calculation that never mentions quantum fields, vacuum >> polarisation, or virtual particles. >> >> Aren't virtual particles necessary for explaining the limited range of >>> the strong force? >>> >> >> No. The uncertainty principle can do that. >> >> >>> And solving the blackhole information paradox? >>> >> >> No. There is no BH information paradox, and virtual particles are not >> necessary in order to understand Hawking radiation (despite what Hawking >> says in his popular accounts. His original paper on the matter does not use >> virtual loops. Not that these exist in the way described, anyway.) >> >> Bruce >> > > Your objections to reifying virtual particles seems very well founded. > Despite that, in your opinion is there a consensus in the physics community > that they exist? Remember, the existence of the quantum foam is the > necessary condition for the conjecture that the Cosmos arose as a quantum > perturbation or eruption from that foam. AG > > Quantum foam is just an idea J. A. Wheeler had, that down at the Planck > scale, the topology of spacetime was foam-like, a maze of connecting > wormholes. It was never worked out as a theory, although string-theory > might be thought of as foam in more dimensions. It's not an assumed basis > for cosmogony in any theory I know of. > > Brent >
Doesn't the theory or conjecture that the Cosmos emerged from a quantum fluctuation assumes the existence of a quantum foam? AG -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/272533cd-4de1-477c-b85c-b76779036611%40googlegroups.com.
