The signed permutation {-2,1,3,-4} plotted above contains the global pattern 1324 below.
On this project, we explored the behavior of the new notion of global pattern containment introduced here.
We consider a signed permutation w as a bijection on the set
{-n,-n+1...-2,-1,1,2...n} such that w(-i)=-w(i). Since signed permutations are odd, the are uniquely defined by their positively indexed values. For example, the signed permutation w={-2,1,3,-4} is plotted to the left. By isolating a size k subsequence in a signed permutation and relabing the values with {1,2...,k} while preserving order, we obtain a global pattern contained in w. For example, since {-2,1,3,-4} contains a subsequence, (-3,2,1,3), order isomprphic to (1,3,2,4), we say {-2,1,3,-4} globally contains (1,3,2,4).
Our research studied the sets of signed permutations which don't contain particular global patterns. We considered subtle set bijections, containments, redundancies, and enumerations. Not only does a rich, vibrant, and nuanced theory exist for global pattern containment, the notion well classifies a wide variety of important combinatorial objects. For example, the signed permutations which contain no 2143 global pattern are the type B vexillary permutations, and the signed permutations containing no 321 or 3412 global patterns are the Type B Boolean permutations.
Distinct Steiner Chains with 14 winding circles sharing SM and SB circles (above).
Archive Link Here When Ready
With Dr. Enrico Au-Yeung
A Steiner Chain is a set of n winding circles all internally tangent to an outer cirlce SM and externally tangent to an inner cirlce SB such that each winding circle is tangent to two other winding cirlces--see the first and second images.
It had seemed that any set of n winding cirles on a given SM SB Pair had the same sum of kth powers of curvatures for certain k. We proved this and successfully made precise when and by how much the sum of kth powers of curvatures depends on which particular winding circles are chosen.
Our work used lots of Inversive Geometry, the study of shapes reflected over circles. To play with this, I've attached desmos graphs of point and cline inversions.
Click the double left arrow above to hide the menus. Circular Inversion of point (above) and of a "cline" (below). What happens below when the three blue points defining the circle are colinear? What circles are invarient under circle inversion? What lines are invarient under circle inversion? What happens close to the inverting circle's center?