The non-orientable 4-genus of a knot [Formula: see text] in [Formula: see text] is defined to be the minimum first Betti number of a non-orientable surface [Formula: see text] smoothly embedded in [Formula: see text] so that [Formula: see text] bounds [Formula: see text]. We will survey the tools used to compute the non-orientable 4-genus, and use various techniques to calculate this invariant for non-alternating 11 crossing knots. We will also view obstructions to a knot bounding a Möbius band given by the double branched cover of [Formula: see text] branched over [Formula: see text].
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Twist number and the alternating volume of knots
It was previously shown by the first author that every knot in [Formula: see text] is ambient isotopic to one component of a two-component, alternating, hyperbolic link. In this paper, we define the alternating volume of a knot [Formula: see text] to be the minimum volume of any link [Formula: see text] in a natural class of alternating, hyperbolic links such that [Formula: see text] is ambient isotopic to a component of [Formula: see text]. Our main result shows that the alternating volume of a knot is coarsely equivalent to the twist number of a knot.
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- Award ID(s):
- 1821254
- PAR ID:
- 10161375
- Date Published:
- Journal Name:
- Journal of Knot Theory and Its Ramifications
- Volume:
- 28
- Issue:
- 01
- ISSN:
- 0218-2165
- Page Range / eLocation ID:
- 1950016
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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