Semigroups are among the most numerous objects in mathematics and also among the most complex.The structure theory of semigroups aims, mainly, at constructing or describing semigroups in terms of other structures such as groups or partially ordered sets. Describing semigroups is a challenging and very hard task and powerful tools and ideas of today's mathematics provide very little help in understanding their structure. Descriptions must, therefore, be assembled "by hand", using only very elementary means.
In this seminar two methods of describing semigroups will be presented: ideal extensions and subdirect products.
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