Formation of knots in mathematical self-avoiding random
walks has been extensively studied (10–16). In the 1960s, Frisch
and Wasserman (10) and Delbruck (11) conjectured that the
probability of finding a knot would approach 100% with an
increasing walk length. In 1988, Sumners and Whittington (15)
proved this conjecture rigorously by showing that exponentially
few arcs would remain unknotted as the length tends to infinity.
Numerical studies of finite-length random walks find that the
probability of knotting and the average complexity of knots
increase sharply with the number of steps (16).
Here, we describe a simple physical experiment on knot
formation. A string was placed in a cubic box and the box was
rotated at constant angular velocity about a principle axis
perpendicular to gravity, causing the string to tumble. We
investigated the probability of knotting, the type of knots
formed, and the dependence on string length. Before tumbling,
the string was held vertically above the center of the box and
dropped in, creating a quasirandom initial conformation. After
tumbling, the box was opened and the ends of the string were
Formation of knots in mathematical self-avoiding randomwalks has been extensively studied (10–16). In the 1960s, Frischand Wasserman (10) and Delbruck (11) conjectured that theprobability of finding a knot would approach 100% with anincreasing walk length. In 1988, Sumners and Whittington (15)proved this conjecture rigorously by showing that exponentiallyfew arcs would remain unknotted as the length tends to infinity.Numerical studies of finite-length random walks find that theprobability of knotting and the average complexity of knotsincrease sharply with the number of steps (16).Here, we describe a simple physical experiment on knotformation. A string was placed in a cubic box and the box wasrotated at constant angular velocity about a principle axisperpendicular to gravity, causing the string to tumble. Weinvestigated the probability of knotting, the type of knotsformed, and the dependence on string length. Before tumbling,the string was held vertically above the center of the box anddropped in, creating a quasirandom initial conformation. Aftertumbling, the box was opened and the ends of the string were
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