# Mathematics Colloquia and Seminars

We introduce invariants of graphs embedded in $$S^3$$ which are related to the Wu invariant and the Simon invariant. Then we use our invariants to prove that $$K_7$$, all Möbius ladders with an odd number of rungs, and the Heawood graph are intrinsically chiral in $$S^3$$. We also use our invariants to obtain lower bounds for the minimal crossing number of particular embeddings of graphs in $$S^3$$.