1. The electrical charge is quantized strictly for elementary particles. What kind constraints does this fact applied to string-net theory? For the this question, I want to understand why electrical charges are quantized instead of a continuous value. What part of the string-net theory quantize the charge?

  2. Another question is how the end of a broken string generate a field is almost uniform to different directions? The electron are claimed as the end of a broken string. I imagine that at the end of a broken string, there should be has one special direction, which is where the string is located. Why we didn't see it in electrons? or the string is in another dimension so the charge looks the same from all directions in 3D space?

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    $\begingroup$ I don't think there is anything unclear about this question. Regarding the first question - As explained here by Xiao-Gang Wen, it has to do with the boundary of the string being discrete. $\endgroup$ – Abhimanyu Pallavi Sudhir Aug 9 '15 at 14:43