We motivate a study of grand unified theories (GUTs) with gauge ?groups beyond SU(5), and we dub them the non-minimal GUTs. ?Historically, this was first proposed by H. Georgi with the aim to ?embed the SM flavors non-trivially in the GUT. We will describe his ?rule of counting the SM generations and point out the possible ?relaxation of his third law of GUT. The non-minimal GUTs usually enjoy ?the global symmetries, as were pointed out by ?Dimopoulos-Raby-Susskind. Thus, they are likely to provide axion ?candidate that satisfies the high-quality criterion. We mainly focus ?on the SU(6) gauge group as a toy model, and will explain the natural ?mass splitting between the (b, tau) and the top quark in the third ?generation through its viable symmetry breaking pattern.

Bio: 2002-2006, 中国科学技术大学，本科。2006-2011，Stony Brook University ?博士。2011-2014 清华大学，博士后。2014-2017，中国科学技术大学，特聘副研究员。2017-2018，北京科技大学，讲师。2018至今，南开大学，副教授。