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Daaavde
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Is an injective endomorphism necessarily surjective? And it is also true the opposite?
jgens said:Based on the OPs questions from yesterday this is probably about vector spaces. The claim is false for most other algebraic structures anyway, so if the vector space assumption is correct, then this just follows from the rank-nullity theorem. In detail, the endomorphism has trivial kernel, so its image has maximal dimension. This is enough to give you surjectivity. The statement that a surjective endomorphism is necessarily injective also follows with a similar proof.
R136a1 said:You seem to assume the vector space is finite-dimensional
An injective endomorphism is a mathematical function that maps each element of a set to a unique element in the same set. This means that no two elements in the domain map to the same element in the codomain.
A surjective endomorphism is a mathematical function that maps every element in the codomain to at least one element in the domain. This means that every element in the codomain has a corresponding element in the domain.
The main difference between an injective and surjective endomorphism is the direction of the mapping. An injective endomorphism maps elements from the domain to the codomain without any repetitions, while a surjective endomorphism maps elements from the codomain back to the domain.
Yes, an endomorphism can be both injective and surjective. This type of endomorphism is called a bijective endomorphism.
The statement "Injective endomorphism = Surjective endomorphism" is significant because it means that the function is both one-to-one and onto, which is known as a bijective function. This type of function has a unique inverse and can be used to solve many mathematical problems.