A short exposition of S. Parsa's theorem on intrinsic linking and non-realizability
We present a short statement and proof of the following result by S. Parsa. Let L be a graph such that the join L*{1,2,3} (i.e. the union of three cones over L along their common bases) piecewise linearly (PL) embeds into R^4. Then L admits a PL embedding into R^3 such that any two disjoint cycles have zero linking number. We also clarify its relation to earlier publications.
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