Sorry if this comes off as a random or soft question. I keep seeing this symbol in my abstract algebra course where it is a plus sign inside of a circle. I am not sure what it means.
Can someone please help me? Sorry if this bothers anyone.
Thanks.
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I think it is a direct sum. – Rungo Mar 06 '14 at 18:33
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http://en.wikipedia.org/wiki/Direct_sum – Derek Allums Mar 06 '14 at 18:43
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5What a pity you didn't give an example or the name of your textbook. – MJD Mar 06 '14 at 18:50
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It's most likely the direct sum symbol.
The direct sum $A\oplus B$ of two abelian groups/rings/modules $A$ and $B$ is the cartesian product $A\times B$ as sets with the obvious relation $(a,b)\ast_{A\oplus B}(c,d)=(a\ast_A c,b\ast_B d)$ where $\ast$ is the addition in the respective object (multiplication is similarly defined if you're working in a ring/module).
Dan Rust
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