Identity in Subcategory C': Does it Coincide with Identity in Category C?

  • Thread starter SVD
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In summary, It is being discussed whether the identity for an object in one category will also be the identity for the same object in another category if certain conditions are met. These conditions include both categories sharing the same objects, the hom-sets in one category being contained in the corresponding hom-sets in the other, and the compositions being restricted in one category compared to the other. An example is given in which the identity for an object A in one category is different from the identity for A in another category, despite meeting these conditions.
  • #1
SVD
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Using the definition given below, I wonder whether we can deduce that for each object A in C',
the identity for A in C' coincides with the identity for A in C.

Let C' and C be two categories which satisfies that
(i)each objects in C' belongs to C
(ii)each hom-set in C' is contained in the corresponding hom-set in C.
(iii)each composition in C' is the restriction of that in C .
 
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  • #2
No. Let C and C' consist out of exactly one object A. Let

[tex]Hom_{C^\prime}(A,A)=\{a\}~\text{and}~Hom_C(A,A)=\{a,b\}[/tex]

with

[tex]a\circ a = a\circ b=b\circ a=a~\text{and}~b\circ b=b[/tex]
 

1. What is the difference between a category and a subcategory?

A category is a broad group or classification, while a subcategory is a more specific subdivision within a category. Subcategories are typically nested within categories to help organize and group related items.

2. How are category and subcategory used in scientific research?

Category and subcategory are commonly used in scientific research to classify and organize data, observations, and variables. They help researchers to better understand and categorize complex systems and phenomena.

3. Can a subcategory belong to more than one category?

Yes, a subcategory can belong to multiple categories. This can occur when a subcategory is related to multiple broad groups or classifications, or when there is overlap between categories.

4. Are categories and subcategories always mutually exclusive?

No, categories and subcategories can sometimes overlap. For example, if a category is "animals" and a subcategory is "mammals", there may be some animals that are both mammals and fall into other subcategories such as "birds" or "reptiles".

5. How do you determine the appropriate categories and subcategories for a research study?

The appropriate categories and subcategories for a research study will depend on the specific topic and research question. Researchers can use existing classifications and taxonomies, consult with experts in the field, or develop their own categories and subcategories based on their study design and objectives.

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