The belt trick or string trick: rotations by 4π of a tethered object are equivalent to no rotation. This allows a tethered object, such as a belt buckle or a tangle core, to rotate forever.

Contexts in source publication

Context 1

... the derivation by Battey-Pratt and Racey, Dirac's equation is in fact seen as the infinitesimal description of Dirac's string trick, also called the belt trick. This trick, illustrated in Figure 9, demonstrates that rear- rangement of tethers implies that a (core) rotation by 4π is equivalent to no rotation at all. In other words, the belt trick, with its tether rearrangement, allows continuous (tethered) core rotation -independently of the number of belts, strands or tethers. ...

Context 2

... way that the transfer of twists, i.e., photon absorption or emission, leads to the observed phase change and to the Feynman diagram for quantum electrodynamics, or QED, is illustrated in Figure 19. ...

Context 3

... the strand definition of the electromagnetic interaction illustrated in Figure 19, together with the tangles of the leptons, yields all Feynman diagrams of QED. For example, pair creation is illustrated in Figure 27; the figure also illustrates lepton-antilepton annihilation. ...

Context 4

... the strand conjecture, the electromagnetic interaction is the rotation of crossings by photon absorption or emission, as illustrated above in Figure 19. The detailed geometry is illustrated in Figure 38. ...

Context 5

... is worth noting that even though the strand configuration of Figure 19 is not chiral, the configurations of Figure 38 are. And by exploring Figure 38 in detail, the fine structure constant α can be estimated. ...