Sills–Wang balanced-ordering conjecture for extremal caterpillars

Let q(x)=xTAkxq(x)=x^TA_kx be the quadratic form associated with the Wiener index of a caterpillar, and let b=(b1,,bk)b=(b_1,\dots,b_k) have multiset of entries

{b1,b2,,bk}={as,,asms,as1,,as1ms1,,a1,,a1m1},\{b_1,b_2,\dots,b_k\}=\{\underbrace{a_s,\dots,a_s}_{m_s},\underbrace{a_{s-1},\dots,a_{s-1}}_{m_{s-1}},\dots,\underbrace{a_1,\dots,a_1}_{m_1}\},

where as>as1>>a1a_s>a_{s-1}>\dots>a_1. When kk is much larger than ss, consider vectors whose entries are arranged as

x={as,,asls,as1,,as1ls1,,a1,,a1m1,,as1,,as1rs1,as,,asrs}.x=\{\underbrace{a_s,\dots,a_s}_{l_s},\underbrace{a_{s-1},\dots,a_{s-1}}_{l_{s-1}},\dots,\underbrace{a_1,\dots,a_1}_{m_1},\dots,\underbrace{a_{s-1},\dots,a_{s-1}}_{r_{s-1}},\underbrace{a_s,\dots,a_s}_{r_s}\}.

Sills–Wang's balanced-ordering conjecture. The quadratic form q(x)q(x) is maximized by this arrangement, where liri1|l_i-r_i|\le 1 and li+ri=mil_i+r_i=m_i for i=2,,si=2,\dots,s.

The conjecture concerns the ordering of repeated decremented degrees that maximizes the Wiener index among the associated caterpillars. The paper states that it disproves this conjecture, so its database status is refuted.

Sources & referencesView supporting material

Primary source

Ya-Lei Jin and Xiao-Dong Zhang, “On the Two Conjectures of the Wiener Index”, arXiv:1304.0873 (2013).

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