Abstract
Letf andg be two quadratic forms in ℝn. Iff(ξ) is positive whereg(ξ) = 0, ξ ≠ 0, then we show that there exists a realλ such thatf — λ g is positive definite. As a consequence we obtain a new description of the old characterization by Terpstra [19] of quasiconvex quadratic forms in two dimensions.
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Communicated by R. Temam
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Marcellini, P. Quasiconvex quadratic forms in two dimensions. Appl Math Optim 11, 183–189 (1984). https://doi.org/10.1007/BF01442177
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DOI: https://doi.org/10.1007/BF01442177