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We have many fields in higher dimensional string theory for charges (B field, C field, RK, RR). Are these fields made up of individual particles like how the EM field is made up of photons? Or do they just have no exchange particles and just carry a strength when produces by strings/ branes?

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Those fields, fluxes, etc come from particular closed string modes. (The graviton is just one mode of the closed string.) For example see slides 48, 49 here.

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  • $\begingroup$ Minor comment to the post (v1): Please consider to mention explicitly author, title, etc. of link, so it is possible to reconstruct link in case of link rot. $\endgroup$
    – Qmechanic
    Mar 14, 2021 at 11:35
  • $\begingroup$ @Mitchell Porter. Just a comment, closed string modes does not produce RR-fields because perturbative string states cannot be charged under them (equivalently, there are no vertex operators for RR p-form fields). $\endgroup$ Mar 15, 2021 at 1:57
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    $\begingroup$ @Ramiro Hum-Sah Thanks for your comment. I guess I assumed that RR fields come from the RR sector of the string. Am I missing something? $\endgroup$ Mar 15, 2021 at 5:54
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This is a comment. I hope you get an answer by an expert in strings.

Roughly: string theory is an extension of quantum mechanics and should be consistent with quantum field theory. In QFT the fields are inactive, the photon field etc. over all space time. They are not composed by individual particles, they are a system where creation and annihilation operators generate and annihilate the named particles. I expect that this will be true in a more convoluted way with the fields defined in string theory.

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The Ramond-Ramond field is a higher gauge field and they are sourced by D-branes which are charged under them. In this sense, they are just like the electromagnetic field which is an ordinary gauge field. To get exchange particles, that is quanta, one would quantise the superstring in a background supporting such a field.

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  • $\begingroup$ I'm not sure that the statement "To get exchange particles, that is quanta, one would quantise the superstring in a background supporting such a field." is true. Fundamental strings are not charged under RR-form fields; then, even if you achieve a successful quantization (which is certainly impossible in the RNS formalism) I cannot understand how do you plan to obtain the particles whose "exchange" mediates a "RR-flux" interaction. $\endgroup$ Mar 15, 2021 at 0:09
  • $\begingroup$ @Ramiro Hum-Sah: the point I was making in the first sentence, is that I was emphasing that a RR field being sourced by a D-brane was akin to a classical field. The missing word in the second sentence is "expect", in that I expected that quantising the superstring, we would find quanta for such fields. $\endgroup$ Mar 17, 2021 at 12:43
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    $\begingroup$ @NiharKarve Yeah, I'm part I'm talking about this. But let's be clear, my point is simply that there are no perturbative string states charged under RR-fields, therefore is not correct to say that RR-fields are are analogous to gauge fields in the sense that both can be described by Feynman diagrams because RR-fields can't be treated in that way, in the general case. This is what the question was asking for. $\endgroup$ Mar 18, 2021 at 15:48
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    $\begingroup$ @NiharKarve Concerning strings on RR-backgrounds. I'm just saying that strings in RR-backgrounds are difficult to quantize in the RSN formalism, maybe that could be circumvented with the pure spinor formalism, sure; but my point is that this is not obvious and, again, I 'm not aware of anyone that can treat a RR-field states using a perturbative scheme (even a non-polynomial one) in analogy with gauge fields, that's what the author of the question was trying to know. $\endgroup$ Mar 18, 2021 at 15:48
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    $\begingroup$ @MoziburUllah Well, that idea is demonstrably wrong. After quantization gauge fields are still gauge fields. Gauge invariance should be preserved by the process of quantization, that's a basic phenomenological requirement. $\endgroup$ Mar 20, 2021 at 14:55

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