• Gill, Amrendra (Department of Mathematics Indian Institute of Technology Ropar) ;
  • Kaur, Kirandeep (Department of Mathematics Indian Institute of Technology Ropar) ;
  • Madeti, Prabhakar (Department of Mathematics Indian Institute of Technology Ropar)
  • Received : 2018.09.09
  • Accepted : 2019.02.07
  • Published : 2019.07.01


In this paper, we formulate a new local move on virtual knot diagram, called arc shift move. Further, we extend it to another local move called region arc shift defined on a region of a virtual knot diagram. We establish that these arc shift and region arc shift moves are unknotting operations by showing that any virtual knot diagram can be turned into trivial knot using arc shift (region arc shift) moves. Based upon the arc shift move and region arc shift move, we define two virtual knot invariants, arc shift number and region arc shift number respectively.

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FIGURE 1. Classical and Virtual crossings

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FIGURE 2. Generalized Reidemeister moves

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FIGURE 3. Detour move

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FIGURE 4. Local writhe or sign of a crossing

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FIGURE 5. Gauss diagram corresponding to virtual figure eight knot

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FIGURE 6. Reidemeister moves on Gauss diagram

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FIGURE 7. Forbidden moves Fu and Fo

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FIGURE 8. Arc (a,b) and (e,f)

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FIGURE 9. Equivalent Arcs (a,b) and (c,d)

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FIGURE 10. Arc shift on arc (a,b)

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FIGURE 11. Equivalent diagrams corresponding to arc shift on arc (a,b)

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FIGURE 12. Arc shift reverses orientation of arc (a,b) in D(a,b)

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FIGURE 13. Arc shift move on arc (a,b)

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FIGURE 14. Gauss diagram analogues to the arc shift moves shown in Fig. 13.

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FIGURE 16. Arc shift move twice on same arc results in equivalent diagram

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FIGURE 17. sign(c') = - sign(c)

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FIGURE 18. R3 move realized via arc shift moves

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FIGURE 20. ∆-move realized using arc shift moves

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FIGURE 21. Turning a Gauss diagram into parallel chord diagram

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FIGURE 22. Unknotting virtual trefoil using arc shift move

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FIGURE 24. Region arc shift on region R1 and R2

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FIGURE 25. Realizing forbidden move Fu using region arc shift

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FIGURE 26. Region arc shift number is 1 for both knots

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FIGURE 28. Forbidden detour move

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FIGURE 29. FD move via region arc shift at region R


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