Question about plabic graphs in the amplituhedron approach

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Discussion Overview

The discussion revolves around plabic graphs within the context of the amplituhedron approach, focusing on their physical relevance, construction using BCFW bridges, and the determination of the parameter "k" from associated permutations. Participants express varying levels of familiarity with the topic and seek clarification on specific aspects.

Discussion Character

  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant questions how to determine if a complicated plabic graph is "physical" and describes an actual process.
  • The same participant inquires about the method for building graphs using BCFW bridges and the process for determining the value of "k" from permutations.
  • Another participant requests clarification on what specific graphs are being discussed, indicating a lack of understanding of the terms used.
  • A further response emphasizes the need for references to understand the context of the discussion, particularly regarding the amplituhedron program and plabic graphs.
  • One participant suggests that the lack of understanding from others may indicate they cannot assist with the question posed.
  • A reference to "Grassmannian Geometry of Scattering Amplitudes" by Akani-Hamed et al. is provided as a potential resource for clarification.

Areas of Agreement / Disagreement

Participants do not appear to agree on the understanding of plabic graphs and the amplituhedron program, with some expressing confusion and others attempting to clarify their inquiries. The discussion remains unresolved regarding the specific questions posed about the graphs.

Contextual Notes

There are limitations in the discussion due to the lack of shared understanding of key terms and concepts, as well as the absence of specific references that could aid in clarifying the topic.

nrqed
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I have a few questions on these graphs. For example if there is a way to tell directly from a complicated graph if it is "physical" in the sense that it describes an actual process. I have also questions on the building of graphs using BCFW bridges, on determining the value of the parameter "k" directly from the permutation associated to a graph, etc.

I won't type all my questions yet, I will wait to see if someone is familiar with these questions first.

But one question is this: I think that the value of "k" (=number of negative helicities) can be obtained directly from the permutation by counting how many of the values are mapped by the permutation to a value above n. Is that correct? I have not seen this stated explicitly like this or proved anywhere.

Thanks!
 
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nrqed said:
I have a few questions on these graphs.

What graphs? What are you talking about?

A reference would help.
 
PeterDonis said:
What graphs? What are you talking about?

A reference would help.
I meant the graphs mentioned in the title of my post: the plabic graphs in the amplituhedron program.
 
nrqed said:
I meant the graphs mentioned in the title of my post: the plabic graphs in the amplituhedron program.

Which doesn't help, since I have no idea what "the amplituhedron program" is, much less what "the plabic graph" in it are. Even if I did, I would have no idea what version of those things you are talking about. That's why you need to give a reference.
 
PeterDonis said:
Which doesn't help, since I have no idea what "the amplituhedron program" is, much less what "the plabic graph" in it are. Even if I did, I would have no idea what version of those things you are talking about. That's why you need to give a reference.

If someone asks a question about Feynman diagrams and someone replies "what diagrams? What are you talking about?", it is probably a sign that the person cannot help with the question.

I wonder how you know that if you knew about plabic graphs as used for the amplituhedron, you would still not know what I am talking about. That's quite amazing to me :-)

If you need a specific reference, you can of course look for example at the "bible" on the topic, "Grassmannian Geometry of Scattering Amplitudes" by Akani-Hamed et al.
 
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