# Degeneracy Graphs and Simplex Cycling by Peter Zörnig By Peter Zörnig

Many difficulties in economics might be formulated as linearly restricted mathematical optimization difficulties, the place the possible resolution set X represents a convex polyhedral set. In perform, the set X usually includes degenerate verti- ces, yielding various difficulties within the choice of an optimum resolution in addition to in postoptimal analysis.The so- referred to as degeneracy graphs symbolize a useful gizmo for des- cribing and fixing degeneracy difficulties. The learn of dege- neracy graphs opens a brand new box of analysis with many theo- retical features and sensible functions. the current pu- blication pursues goals. at the one hand the speculation of degeneracy graphs is built mostly, in an effort to function a foundation for extra functions. nevertheless dege- neracy graphs might be used to provide an explanation for simplex biking, i.e. beneficial and enough stipulations for biking might be de- rived.

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Extra info for Degeneracy Graphs and Simplex Cycling

Example text

2). 54 Cf. Appendix, Def. 3. 55 Kruse (1986:13) presents a more complicated positive degeneracy graph (note the area with hatching). 56 Cf. Appendix, Def. 3. ---... 4 Legend: u - node (basis) B~ (u=1, ... ,4). Fig. 2). Tab. 1 Pivot tableau of a basis of the O"-degenerate vertex xo. ps 1 ... 0" 1 0 . 1 0 0"+1 ... m 0 ... 0 0 1 0 ... 0 ... 0 1 m+1 Yl,m+l ... m+n Yl,m+n 0 . 3: Let a pivot tableau of a O"-degenerate vertex xo be given in the form of Tab. 2. a) The subtableau in bold type is called a degeneracy tableau of xo .

Fig. 2 shows that the column vectors of M are points of a straight line passing the origin. e. {4, 5, 7} is an index set of a 2 x 3-submatrix of (YII2 ) with rank < 2 (namely of M). Analogous considerations for all possible choices of column vectors result in the following collection of 2 x k-submatrices of (YII2 ) with rank < 2 (k :s; 7): {2,3,6},{2,3},{2,6},{3,6},{4,5,7},{4,5},{4,7},{5,7}. Hence the system on {I, ... ,7} induced by Y is ~= {{2,3,6},{4,5,7}}. Definition 3 .. 13: A set system ~ on {I, ...

2 we assume that the matrix y of a degen- eracy graph Gy has to be feasibly laid ( cf. Kruse (1986:40)). 69 Cf. Def. 5. 40 126 134 (8) 246 236 Legend: i, j, k - node {i,j,k} of 8 Fig. 2. e. T = Ty. e The interrelations in the above theorem are illustrated in Fig. 4 which has to be interpreted as follows: By the mapping (8) 1--+ T = 1)(8) the u x n-index graph (8) is biuniquely assigned to a u-normal set system T. Moreover, the class of u x n-degeneracy graphs is contained in the class of u x n-index graphs, while the class of u-induced set systems on {I, ...