What Is a Lie Group Without an Identity Matrix Called?

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Discussion Overview

The discussion revolves around the concept of a Lie "group" that does not include the identity matrix as a member. Participants explore the implications of this absence and seek terminology related to the broader mathematical ideas that arise from this situation.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions whether there is a specific name for studying a Lie "group" without the identity matrix and seeks related terminology for further research.
  • Another participant suggests that without an identity, the structure would lack inverses, implying it could be classified as a semigroup at best.
  • A third participant expresses gratitude for the term "semigroup," which leads them to discover the concept of "magma," indicating a more generalized structure they were considering.
  • A later reply references an article by John Baez, introducing the term "torsor" as a concept akin to a group that has lost its identity, suggesting a potentially interesting avenue for exploration.

Areas of Agreement / Disagreement

Participants do not reach a consensus on a specific term for the structure in question, and multiple competing views regarding the classification and terminology remain present.

Contextual Notes

The discussion highlights the ambiguity in defining structures without an identity element and the potential for various interpretations based on different mathematical frameworks.

Who May Find This Useful

Mathematicians and students interested in abstract algebra, group theory, and the study of algebraic structures may find this discussion relevant.

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Is there a name for studying a Lie "group" that doesn't use the identity matrix as a member of the group?

I know it's not technically a group anymore, but is there any mathematical work pertaining to the general idea... and what is the terminology so that I can research it better?
 
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If there is no identity then there are no inverses, so at best you'll be left with a semigroup.
 
thanks! "Semigroup" led me to "magma", which is more the generalized concept I was thinking of. <3 Wiki.
 

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