Jaehyeon Lee
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  • On Quasi-finite Morphisms (Part 2)

    In this post, we continue our discussion of the application of Zariski's Main Theorem, following 'On Quasi-finite Morphisms (Part 1)'.

    10 min read   ·   July 25, 2025

    2025   ·   Algebraic_Geometry  

  • On Quasi-finite Morphisms (Part 1)

    In this post, we will discuss the definition and properties of quasi-finite morphisms, and its application to Zariski's Main Theorem.

    18 min read   ·   July 23, 2025

    2025   ·   Algebraic_Geometry  

  • On the Characteristic of a Ring

    In this post, we will see that the usual definition of the characteristic of a ring obscures its true nature, and explain why another equivalent characterization is conceptually more useful.

    6 min read   ·   July 11, 2025

    2025   ·   Algebra  

  • Algebraically closed complete field may not have a complete image in $\mathbb{R}$ under its absolute value

    In this post, we will see that the image of $\mathbb{C}_p$, the complete algebraic closure of $\mathbb{Q}_p$, has a non-complete image in $\mathbb{R}$.

    6 min read   ·   July 4, 2025

    2025   ·   Number_Theory,   p-adic_Geometry     ·   Number_Theory  

  • Natural Isomorphisms with Non-Natural-Looking Inverses

    In this post, we will talk about canonical isomorprhisms with non-canonical-looking inverses related to tensor products in linear algebra.

    5 min read   ·   July 19, 2023

    2023   ·   Linear_Algebra,   Tensor_Products     ·   Linear_Algebra  

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