How abusive of notation is it to drop isomorphisms?

In summary, the conversation discusses the use of isomorphisms in mathematics papers and the potential issues with omitting certain isomorphisms in calculations. The example of an isomorphism in a category with a terminal object is given, and the potential problems with making such associations are discussed. It is noted that while this practice makes mathematics easier to read, it is important to remember the identifications made to avoid confusion.
  • #1
icantadd
114
0
I have a general sort of structural question. I have been reading a lot of maths papers lately, and it seems there are some isomorphisms that people omit from their calculations. For example, in a category with a terminal object, 1,
[tex]A \cong A \times 1[/tex]
where the isomorphism is given from left to right by [tex] \langle 1_A , !_A \rangle [/tex] where ! is the unique map into the terminal object, and the isomorphism from right to left is (left) projection. Now, let [tex] a : 1 \to A [/tex]; an example of the abuse of notation I have seen quite often is to regard
[tex] \langle a , 1_1 \rangle : 1 \to A \times 1 [/tex] as just [tex] a [/tex]

Are there any obvious problems with making such an association? Are there any non-obvious problems with making such an association? Am I missing something?
 
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  • #2
Mathematics would be much more difficult to read if we didn't make such identifications. Usually, there are no problems with it, but you should always keep in mind that you made the identification. Sometimes you can find yourself very confused about something, and it turns out you forgot you identified some things previously. But normally, there are no problems...
 
  • #3
Thank you for the reply!
 

What does it mean to "drop isomorphisms" in notation?

Dropping isomorphisms in notation means to omit or ignore the use of isomorphisms, which are mathematical structures that preserve the structure of objects between different categories or sets.

Why is dropping isomorphisms considered abusive of notation?

Dropping isomorphisms can be considered abusive of notation because it can lead to confusion and inaccuracies in mathematical expressions. Isomorphisms play an important role in maintaining the integrity and coherence of mathematical reasoning and dropping them can result in incorrect or invalid conclusions.

What are some common examples of dropping isomorphisms in notation?

One common example is dropping the use of parentheses in algebraic expressions, which can lead to ambiguity and incorrect solutions. Another example is dropping the use of arrows in category theory, which can obscure the relationships between objects and categories.

Are there any instances where it is acceptable to drop isomorphisms in notation?

In some cases, dropping isomorphisms can be acceptable if it does not affect the overall meaning or validity of a mathematical expression. However, this should only be done after careful consideration and with a clear understanding of the potential consequences.

How can one avoid being abusive of notation when using isomorphisms?

To avoid being abusive of notation when using isomorphisms, it is important to clearly define and label all isomorphic structures and to use them consistently throughout a mathematical argument or proof. It is also important to understand the limitations and implications of dropping isomorphisms and to use them judiciously.

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