Description of posets critical with respect to the nonnegativity of the quadratic Tits form
We present the complete description of finite posets whose Tits form is not nonnegative but all proper subsets of which have nonnegative Tits forms. A similar result for positive forms was obtained by the authors earlier.
English version (Springer): Ukrainian Mathematical Journal 61 (2009), no. 5, pp 734-746.
Citation Example: Bondarenko V. M., Stepochkina M. V. Description of posets critical with respect to the nonnegativity of the quadratic Tits form // Ukr. Mat. Zh. - 2009. - 61, № 5. - pp. 611-624.