Counterexamples to Tischler's strong form of smale's mean value conjecture

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Smale's mean value conjecture asserts that minθ |P(θ)/θ| ≤ K|P′(0)| for every polynomial P of degree d satisfying P(0) = 0, where K = (d-1)/d and the minimum is taken over all critical points 6 of P. A stronger conjecture due to Tischler asserts that minθ|1/2 - P(θ)/θ·P′(0)| ≤ K 1 with K1 = 1/2 - 1/d. Tischler's conjecture is known to be true: (i) for local perturbations of the extremum P0(z) = z d - dz, and (ii) for all polynomials of degree d ≤ 4. In this paper, Tischler's conjecture is verified for all local perturbations of the extremum P1(z) = (z - 1)d -(-1)d, but counterexamples to the conjecture are given in each degree d ≥ 5. In addition, estimates for certain weighted L1- and L 2-averages of the quantities 1/2 - P(θ)/θ · P′(0) are established, which lead to the best currently known value for K1 in the case d = 5.

Original languageEnglish (US)
Pages (from-to)95-106
Number of pages12
JournalBulletin of the London Mathematical Society
Issue number1
StatePublished - 2005

ASJC Scopus subject areas

  • Mathematics(all)


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