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We prove a splicing formula for the LMO invariant, which is the universal finite-type invariant of rational homology $3$-spheres. Specifically, if a rational homology $3$-sphere $M$ is obtained by gluing the exteriors of two framed knots $K_1 subset M_1$ and $K_2subset M_2$ in rational homology $3$-spheres, our formula expresses the LMO invariant of $M$ in terms of the Kontsevich-LMO invariants of $(M_1,K_1)$ and $(M_2,K_2)$. The proof uses the techniques that Bar-Natan and Lawrence developed to obtain a rational surgery formula for the LMO invariant. In low degrees, we recover Fujitas formula for the Casson-Walker invariant and we observe that the second term of the Ohtsuki series is not additive under standard splicing. The splicing formula also works when each $M_i$ comes with a link $L_i$ in addition to the knot $K_i$, hence we get a satellite formula for the Kontsevich-LMO invariant.
We prove a cabling formula for the concordance invariant $ u^+$, defined by the author and Hom. This gives rise to a simple and effective 4-ball genus bound for many cable knots.
A new topological operad is introduced, called the splicing operad. This operad acts on a broad class of spaces of self-embeddings N --> N where N is a manifold. The action of this operad on EC(j,M) (self embeddings R^j x M --> R^j x M with support i
We define and study a bigraded knot invariant whose Euler characteristic is the Alexander polynomial, closely connected to knot Floer homology. The invariant is the homology of a chain complex whose generators correspond to Kauffman states for a knot
By 2-twist-spinning the knotted graph that represents the knotted handlebody $5_2$, we obtain a knotted foam in 4-dimensional space with a non-trivial quandle cocycle invariant.
We extend the definition of Khovanov-Lee homology to links in connected sums of $S^1 times S^2$s, and construct a Rasmussen-type invariant for null-homologous links in these manifolds. For certain links in $S^1 times S^2$, we compute the invariant by