IMI/Publicaţii/CSJM/Ediţii/CSJM v.9, n.2 (26), 2001/

Lower and upper chromatic numbers for BSTSs(2h - 1)

Authors: Marco Buratti, Mario Gionfriddo, Lorenzo Milazzo, Vitaly Voloshin


In [Discrete Math. 174, (1997) 247-259] an infinite class of STSs(2h - 1) was found with the upper chromatic number not(χ)=h.

We prove that in this class, for all STSs(2h - 1) with h<10, the lower chromatic number coincides with the upper chromatic number, i.e. χ=not(χ)=h and moreover, there exists a infinite sub-class of STSs with χ=not(χ)=h for any value of h.

M.Buratti, M.Gionfriddo, L.Milazzo, V.Voloshin,
Marco Buratti,
Dipartimento di Matematica e Informatica,
Universita di Perugia,
Via Vanvitelli, 1, 06123 Perugia, Italia.
Mario Gionfriddo, Lorenzo Milazzo,
Dipartimento di Matematica e Informatica,
Universita di Catania,
Viale A.Doria, 6 95125 - Catania, Italia.
Vitaly Voloshin,
Institute of Mathematics and Computer Science
of Moldovan Academy of Sciences,
str. Academiei 5, Chisinau,
MD-2028, Moldova.


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