## Group presentations corresponding to spines of $3$-manifolds. III

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- by R. P. Osborne and R. S. Stevens PDF
- Trans. Amer. Math. Soc.
**234**(1977), 245-251 Request permission

## Abstract:

Continuing after the previous papers of this series, attention is devoted to RR-systems having two towns (i.e., to compact 3-manifolds with spines corresponding to group presentations having two generators). An interesting kind of symmetry is noted and then used to derive some useful results. Specifically, the following theorems are proved: Theorem 1.*Let*$\phi$

*be a group presentation corresponding to a spine of a compact orientable*3-

*manifold, and let w be a relator of*$\phi$

*involving just two generators a and b. If w is cyclically reduced, then either*(a)

*w can be “written backwards"*(

*i.e., if*$w = {a^{{m_1}}}{b^{{m_1}}}{a^{{m_2}}}{b^{{n_2}}} \ldots {a^{{m_k}}}{b^{{n_k}}}$,

*then w is a cyclic conjugate of*${b^{{n_k}}}{a^{{m_k}}} \ldots {b^{{n_2}}}{a^{{m_2}}}{b^{{n_1}}}{a^{{m_1}}}$),

*or*(b)

*w lies in the commutator subgroup of the free group on a and b*. Theorem 2. (

*Loose translation*).

*If*$\phi$

*is a group presentation with two generators and if the corresponding*2-

*complex*${K_\phi }$

*is a spine of a closed orientable*3-

*manifold then*, ${K_\phi }$

*is a spine of a closed orientable*3-

*manifold if and*(

*except for two minor cases*)

*only if*$\phi$

*has two relators and among the six allowable types of syllables*(3

*in each generator*),

*exactly four occur an odd number of times. Further, each of the two relators can be “written backwards."*

## References

- Richard S. Stevens,
*Classification of $3$-manifolds with certain spines*, Trans. Amer. Math. Soc.**205**(1975), 151–166. MR**358786**, DOI 10.1090/S0002-9947-1975-0358786-0 - R. P. Osborne and R. S. Stevens,
*Group presentations corresponding to spines of $3$-manifolds. I*, Amer. J. Math.**96**(1974), 454–471. MR**356058**, DOI 10.2307/2373554 - R. P. Osborne and R. S. Stevens,
*Group presentations corresponding to spines of $3$-manifolds. II*, Trans. Amer. Math. Soc.**234**(1977), no. 1, 213–243. MR**488062**, DOI 10.1090/S0002-9947-1977-0488062-9 - L. Neuwirth,
*An algorithm for the construction of $3$-manifolds from $2$-complexes*, Proc. Cambridge Philos. Soc.**64**(1968), 603–613. MR**226642**, DOI 10.1017/s0305004100043279 - Joan S. Birman and Hugh M. Hilden,
*Heegaard splittings of branched coverings of $S^{3}$*, Trans. Amer. Math. Soc.**213**(1975), 315–352. MR**380765**, DOI 10.1090/S0002-9947-1975-0380765-8

## Additional Information

- © Copyright 1977 American Mathematical Society
- Journal: Trans. Amer. Math. Soc.
**234**(1977), 245-251 - MSC: Primary 57A10; Secondary 55A05
- DOI: https://doi.org/10.1090/S0002-9947-1977-0488063-0
- MathSciNet review: 0488063