4 ms·

I'd call them purely mathematical constructs that arise from the need of modern QM theories to mediate all interactions with particles.

Twisol 6y ago
The article seems to be saying that there really is some physical phenomenon occurring here -- effectively, "cross-feed" between coupled fields -- but that this phenomenon doesn't obey the relations that define a "particle". Or, more metaphorically, a particle is more of a squishy, wobbly blob (with a rather ill-defined boundary) than a rigid packet, and as it wobbles "in and out" of the individual fields it's coupled to, its effect on those fields will vary.
ISL 6y ago
They are mathematical constructs, but they can sometimes lead to viable intuition. Classic (and necessarily simplifying) "how it works" explanations for Hawking radiation, the Casimir effect, deep inelastic scattering results, and more rely upon invoking virtual particles. Matt Strassler was among several theorists who helped me, as a graduate student, to develop a deeper intuition for quantum fields -- it is important to develop an understanding of the strengths and weaknesses of both the simplistic and nuanced ways of thinking about and discussing these interactions. It is tempting to regard Feynman diagrams as if they are actually what is happening. One should only use them as guides to intuition. They are actually compact expressions of successive terms in a perturbative expansion, terms that can interfere with one another sometimes. Theorists (like Matt), who work with these things every day come to develop a more-nuanced understanding, generally one that places greater weight on fields (not just the bosonic force-mediating fields, but the fields for the fermions, too) than understood by even many practicing physicists in other specialties. Another helpful insight that may aid understanding of virtual particles as you start to understand things more-deeply: the photons we observe with our eyes from distant stars need not be exactly on-shell, just very (very!) close.
- pixel_fcker 6y ago
  How do virtual particles play into the Casimir effect?
  - ISL 6y ago
    Search within the article for 'Casimir effect': https://en.m.wikipedia.org/wiki/Virtual_particle https://en.m.wikipedia.org/wiki/Virtual_particle It is not the most-useful/calculable way to think about it, but it is an evocative way to motivate the idea of fluctuations of quantum fields.

Twisol 6y ago

The article seems to be saying that there really is some physical phenomenon occurring here -- effectively, "cross-feed" between coupled fields -- but that this phenomenon doesn't obey the relations that define a "particle". Or, more metaphorically, a particle is more of a squishy, wobbly blob (with a rather ill-defined boundary) than a rigid packet, and as it wobbles "in and out" of the individual fields it's coupled to, its effect on those fields will vary.

ISL 6y ago

They are mathematical constructs, but they can sometimes lead to viable intuition. Classic (and necessarily simplifying) "how it works" explanations for Hawking radiation, the Casimir effect, deep inelastic scattering results, and more rely upon invoking virtual particles. Matt Strassler was among several theorists who helped me, as a graduate student, to develop a deeper intuition for quantum fields -- it is important to develop an understanding of the strengths and weaknesses of both the simplistic and nuanced ways of thinking about and discussing these interactions. It is tempting to regard Feynman diagrams as if they are actually what is happening. One should only use them as guides to intuition. They are actually compact expressions of successive terms in a perturbative expansion, terms that can interfere with one another sometimes. Theorists (like Matt), who work with these things every day come to develop a more-nuanced understanding, generally one that places greater weight on fields (not just the bosonic force-mediating fields, but the fields for the fermions, too) than understood by even many practicing physicists in other specialties. Another helpful insight that may aid understanding of virtual particles as you start to understand things more-deeply: the photons we observe with our eyes from distant stars need not be exactly on-shell, just very (very!) close.

pixel_fcker 6y ago
How do virtual particles play into the Casimir effect?
- ISL 6y ago
  Search within the article for 'Casimir effect': https://en.m.wikipedia.org/wiki/Virtual_particle https://en.m.wikipedia.org/wiki/Virtual_particle It is not the most-useful/calculable way to think about it, but it is an evocative way to motivate the idea of fluctuations of quantum fields.