TY - JOUR AU - Miklós Ujvári PY - 2012/01/01 Y2 - 2024/03/29 TI - New descriptions of the Lovász number, and the weak sandwich theorem JF - Acta Cybernetica JA - Acta Cybern VL - 20 IS - 4 SE - Regular articles DO - 10.14232/actacyb.20.4.2012.3 UR - https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3824 AB - In 1979, L. Lovász introduced the concept of an orthonormal representation of a graph, and also a related value, now popularly known as the Lovász number of the graph. One of the remarkable properties of the Lovász number is that it lies sandwiched between the stability number of the graph and the chromatic number of the complementary graph. This fact is called the sandwich theorem. In this paper, using new descriptions of the Lovász number and linear algebraic lemmas we give three proofs for a weaker version of the sandwich theorem. ER -