I somewhat can wrap my head around virtual particles in terms of quantum field theory, (as much as possible), and I'm just curious how string theorists would describe them.
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Have you read this? – Nemo Oct 30 '17 at 14:44
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@Arthur you mean this one? https://physics.stackexchange.com/q/147096/ – mcchucklezz Oct 30 '17 at 14:46
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Related: https://physics.stackexchange.com/q/3262/ The answer to the present question is actually contained in the answers of the question I have just quoted. Perhaps a pedestrian summary is in order though… – Oct 30 '17 at 15:37
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@LucJ.Bourhis that would be greatly appreciated, I'm still learning – mcchucklezz Oct 30 '17 at 15:38
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May I ask how much Quantum Field Theory you know? – Oct 30 '17 at 15:40
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@LucJ.Bourhis I can visualize delocalization of particles and interactions, but mathematically I'm lacking – mcchucklezz Oct 30 '17 at 15:41
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1Virtual particles (as much as they are a thing, which they are not!) are replaced with virtual strings. – Prahar Oct 30 '17 at 16:58
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@Prahar thanks, but that doesn't help – mcchucklezz Oct 30 '17 at 17:10
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@script8man - What is your understanding of virtual particles in ordinary quantum field theory (you do say... I somewhat can wrap my head around virtual particles in terms of quantum field theory...) – Prahar Oct 30 '17 at 17:13
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In Quantum Field Theory virtual particles are not particles, they are just disturbances in the field that is not a particle itself. So you have an effect that looks like its coming from particle but there is no particle. We measure the effect and use that for calculations.
Now in string theory, we just have strings that are vibrating at different frequencies. We treat them as "real" strings. Then there are virtual strings, we can only measure(for lack of better word) the effects but they are not the "real" strings that we defined but are "virtual" strings but we use the effect in our calculations.

LostCause
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I'm a layman who's read about but struggled with the concept of virtual particles. I've never seen it explained quite this way before and I think that's a nice way of explaining them to someone who, like me, doesn't get them. I've heard them called a "Mathematical notation", but I never understood the concept of a mathematical notation. Your definition is easier to get a handle on. – userLTK Oct 30 '17 at 20:44
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The only reason I am on this forum is that I hate reading long complicated answers that only scare away people who are just curious. Please upvote if you find that I answered your question so that I can use more features of this website and help more people. Right now, with my reputation, I can only do so little. Thanks. – LostCause Oct 30 '17 at 20:59
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I plan to upvote. I just though I'd wait and see if any of the big brains around here had anything to say first, like "that's now how it is at all" or something like that so I wanted to give it some time. I like your explanation a lot, but thought I'd wait for more feedback. I also agree with you on straight forward explanations. That's a big plus on this site a lot of the time. – userLTK Oct 30 '17 at 21:20
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1Virtual particles are nothing but a visual aid to conceptualise and convey a particular type of computation but, hey, that's pretty much what you wrote! Except for "disturbance in the field" which I really cannot relate to:
A virtual particle is one-to-one a propagator in a Feynman diagram in QFT, and a propagator is a quantum amplitude of transition</long complicated stuff that will scare away people> – Oct 30 '17 at 23:32