MyWikiBiz, Author Your Legacy — Tuesday October 28, 2025
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| | This section develops the aspects of group theory that are needed in this work, bringing together a fundamental selection of abstract ideas and concrete examples that are used repeatedly throughout the rest of the project. To start, I present an abstract formulation of the basic concepts of group theory, beginning from a very general setting in the theory of relations and proceeding in quick order to the definitions of groups and their representations. After that, I describe a couple of concrete examples that are designed mainly to illustrate the abstract features of groups, but that also appear in different guises at later stages of this discussion. | | This section develops the aspects of group theory that are needed in this work, bringing together a fundamental selection of abstract ideas and concrete examples that are used repeatedly throughout the rest of the project. To start, I present an abstract formulation of the basic concepts of group theory, beginning from a very general setting in the theory of relations and proceeding in quick order to the definitions of groups and their representations. After that, I describe a couple of concrete examples that are designed mainly to illustrate the abstract features of groups, but that also appear in different guises at later stages of this discussion. |
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| | + | A '''series of domains''' (SOD) is a nonempty sequence of nonempty sets. A declarative indication of a sequence of sets, typically offered in staking out the grounds of a discussion, is taken for granted as a SOD. Thus, the notation <math>{}^{\backprime\backprime}(X_i)_i{}^{\prime\prime}</math> is assumed by default to refer to a SOD <math>(X_i)_i,\!</math> where each <math>X_i\!</math> is assumed to be a nonempty set. |
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| | <pre> | | <pre> |
| − | A "series of domains" (SOD) is a nonempty sequence of nonempty sets. A declarative indication of a sequence of sets, typically offered in staking out the grounds of a discussion, is taken for granted as a SOD. Thus, the notation "<Xi>" is assumed by default to refer to a SOD <Xi>, where each Xi is assumed to be a nonempty set.
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| | Given a SOD <Xi>, its cartesian product, notated as "Xi <Xi>" or "Xi Xi", is defined as follows: | | Given a SOD <Xi>, its cartesian product, notated as "Xi <Xi>" or "Xi Xi", is defined as follows: |
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