• 대한수학회지
• /
• 제50권4호
• /
• pp.865-877
• /
• 2013

The disjoint union of mapping class groups of surfaces forms a braided monoidal category $\mathcal{M}$, as the disjoint union of the braid groups $\mathcal{B}$ does. We give a concrete and geometric meaning of the braidings ${\beta}_{r,s}$ in $\mathcal{M}$. Moreover, we find a set of elements in the mapping class groups which correspond to the standard generators of the braid groups. Using this, we can define an obvious map ${\phi}\;:\;B_g{\rightarrow}{\Gamma}_{g,1}$. We show that this map ${\phi}$ is injective and nongeometric in the sense of Wajnryb. Since this map extends to a braided monoidal functor ${\Phi}\;:\;\mathcal{B}{\rightarrow}\mathcal{M}$, the integral homology homomorphism induced by ${\phi}$ is trivial in the stable range.

• 대한수학회지
• /
• 제49권3호
• /
• pp.493-502
• /
• 2012

In this article, we give a characterization theorem for a class of corank-1 Butler groups of the form $\mathcal{G}$($A_1$, ${\ldots}$, $A_n$). In particular, two groups $G$ and $H$ are quasi-isomorphic if and only if there is a label-preserving bijection ${\phi}$ from the edges of $T$ to the edges of $U$ such that $S$ is a circuit in T if and only if ${\phi}(S)$ is a circuit in $U$, where $T$, $U$ are quasi-representing graphs for $G$, $H$ respectively.

• Korean Journal of Mathematics
• /
• 제27권2호
• /
• pp.535-545
• /
• 2019

The main idea of this paper is to introduce the notion of $cat^1$-monoids and to prove that the category of crossed semimodules ${\mathcal{C}}=(A,B,{\partial})$ where A is a group is equivalent to the category of $cat^1$-monoids. This is a generalization of the well known equivalence between category of $cat^1$-groups and that of crossed modules over groups.

• 대한수학회논문집
• /
• 제28권2호
• /
• pp.231-241
• /
• 2013

On the framework of the 2-adic group $\mathcal{Z}_2$, we study a Sobolev-like inequality where we estimate the $L^2$ norm by a geometric mean of the BV norm and the $\dot{B}_{\infty}^{-1,{\infty}}$ norm. We first show, using the special topological properties of the $p$-adic groups, that the set of functions of bounded variations BV can be identified to the Besov space ˙$\dot{B}_1^{1,{\infty}}$. This identification lead us to the construction of a counterexample to the improved Sobolev inequality.