Selected Notes

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    1_original_notes

  • scheme (last compiled 05 Feb 2026)
    (Scheme Theory this is my note for scheme theory. this is mainly based on (1) Görtz - Wedhorn AG 1 ...)
  • module (last compiled 08 Nov 2025)
    (Some words on commutative algebra from the perspective of smooth manifold and vector bundle Nguyen Ngoc Khanh November 8, 2025 ...)
  • pca (last compiled 04 Oct 2025)
    (PCA A tutorial on Principle Component Analysis Khanh Nguyen August 2022, March 2023 Revisited 1 Problem Setup In this section, ...)
  • sheaf_iso (last compiled 01 Sep 2025)
    (sheaf isomorphism ismorphisms of sheaves on open cover implies isomorphism on the whole sheaves Khanh Nguyen November 2024 Lemma 1. ...)
  • spectral (last compiled 28 Aug 2025)
    (From Mass-Spring Systems to Spectral Graph Neural Networks Nguyen Ngoc Khanh August 28, 2025 1 Mass-Spring System 1.1 The two ...)
  • filter (last compiled 28 Aug 2025)
    (filter originally from my facebook post https: // www. facebook. com/ share/ p/ xWTeaskbL57ndGgn Khanh Nguyen June 2024 0.1 TLDR ...)
  • finite_union_compactness (last compiled 28 Aug 2025)
    (compactness Khanh Nguyen September 2023 this text presents the idea of local-to-global principle as a definition of compactness In mathematics, ...)
  • 2_study_notes

  • ma5204_notes (last compiled 26 Jan 2026)
    (MA5204 Commutative and Homological Algbera this is my notes for MA5204 Commutative and Homological Algbera. this course is taught by ...)
  • adjunction (last compiled 21 Jan 2026)
    (adjunction this is notes for adjunction, this is basically a chapter in Topology: A Categorical Approach which was very well-written ...)
  • ma5210_notes (last compiled 12 Jan 2026)
    (differentiable manifolds this is my notes for ma5210 differential manifolds taught by National University of Singapore Professor Loke Hung Yean ...)
  • vakil_foag (last compiled 22 Dec 2025)
    (My notes for "Ravi Vakil - The Rising Sea: Foundations of Algebraic Geometry" Nguyen Ngoc Khanh December 22, 2025 Contents ...)
  • ma5209_notes_at (last compiled 08 Nov 2025)
    (ma5209 - algebraic topology Khanh Nguyen January 2024 Chapter 1 CATEGORY AND HOMOLOGICAL ALGEBRA 1.1 BASIC HOMOLOGICAL ALGEBRA Definition 1 ...)
  • dummit_foote_algebra (last compiled 08 Nov 2025)
    (Algebra this is my notes for Dummit Foote - Abstract Algebra. Despiting hating math and algebra in my secondary school, ...)
  • kunneth_theorem (last compiled 08 Nov 2025)
    (K¨unneth Theorem subtitle Khanh Nguyen April 2024 1 UNIVERSAL COEFFICIENT THEOREM Theorem 1 (universal coefficient theorem). Let R be a ...)
  • hartshorne_algebraic_geometry (last compiled 04 Oct 2025)
    (Algebraic Geometry My notes on Hartshorne Algebraic Geometry Dec 2024 2 Chapter 1 Varieties 1.1 Affine Varieties 1.2 Projective Varieties ...)
  • ma4271_tut_wk3 (last compiled 28 Aug 2025)
    (MA4271 Tutorial Week 3 Nguyen Ngoc Khanh - A0275047B August 2023 Problem 1 Let u, v, w ∈R3 be three ...)
  • ma4271_hw3 (last compiled 28 Aug 2025)
    (MA4271 Homework 3 Nguyen Ngoc Khanh - A0275047B October 2023 1 Problem Problem 1 Prove that the absolute value of ...)
  • ma5259_hw1 (last compiled 28 Aug 2025)
    (ma5259 hw1 Nguyen Ngoc Khanh - A0275047B September 2024 1 Lecture Exercises 1.1 Lecture 1 Exercise 1 If E, F ...)
  • ma4271_tut_wk4 (last compiled 28 Aug 2025)
    (MA4271 Tutorial Week 4 Nguyen Ngoc Khanh - A0275047B September 2023 Problem 1 Find the curvature of α(t) = (t ...)
  • ma4271_hw2 (last compiled 28 Aug 2025)
    (MA4271 Homework 2 Nguyen Ngoc Khanh - A0275047B September 2023 1 Problem Problem 1 Is the set A = {(x, ...)
  • set (last compiled 28 Aug 2025)
    (set Khanh Nguyen June 2023 some identities related to set 1 Zermelo–Fraenkel set theory 9 axioms in ZFC serve as ...)
  • real_analysis (last compiled 28 Aug 2025)
    (Some theorems we might missed in Real Analysis Khanh Nguyen August 2023 Definition 1 (left limit and right limit) Let ...)
  • calculus (last compiled 28 Aug 2025)
    (Calculus Khanh Nguyen May 2023 As a physics student in high school, CS undergraduate in NTU, I never have a ...)
  • ma5210_a1 (last compiled 28 Aug 2025)
    (ma5210 assignment 1 Nguyen Ngoc Khanh - A0275047B August 2024 Let (M, T ) be a topological space. We assume ...)
  • ma4261_hw3 (last compiled 28 Aug 2025)
    (ma4261 hw3 Nguyen Ngoc Khanh - A0275047B August 2024 1 Question 1 Let pY |X be a ternary channel with ...)
  • CZ4071 Network Science Assignment 2 (last compiled 28 Aug 2025)
    (CZ4071 Network Science Assignment 2 - Final Report Survey and Implementation of Paper: [7] Difan Zou, Ziniu Hu, Yewen Wang, ...)
  • ma4261_hw2 (last compiled 28 Aug 2025)
    (ma4261 hw1 Nguyen Ngoc Khanh - A0275047B August 2024 1 Problem 1 Consider random variables X and Y such that ...)
  • ma5259_notes (last compiled 28 Aug 2025)
    (Probability Theory a rigorous treatment to probability theory and its applications to stochastic processes Khanh Nguyen August 2024 Chapter 0 ...)
  • ma5205_notes (last compiled 28 Aug 2025)
    (ma5205 - measure and integral Nguyen Ngoc Khanh September 2023 Chapter 1 Measurable Space 1.1 Measurable Space In R, we ...)
  • ma5211_hw1 (last compiled 28 Aug 2025)
    (ma5211 hw1 Nguyen Ngoc Khanh - A0275047B January 2024 1 Problem Set I (1) Let Mn be the space of ...)
  • topbook_harder (last compiled 28 Aug 2025)
    (topbook harder Khanh Nguyen June 2023 some harder or interesting problems in topbook2023.pdf Common I will put here some common ...)
  • triangle-inequality (last compiled 28 Aug 2025)
    (triangle inequality khanh Sep 2021 Given an inner product space V over field F (R or C). The inner product ...)
  • topology_categorical_approach (last compiled 28 Aug 2025)
    (topology - a categorical approach Khanh Nguyen June 2024 Chapter 1 FOUR CONSTRUCTIONS OF TOPOLOGY Categorical definitions of some common ...)
  • differential_forms_and_stoke_theorem (last compiled 28 Aug 2025)
    (Differential Forms and Stoke’s Theorem Khanh Nguyen August 2023 this is my notes on Differential Forms and Stoke’s Theorem from ...)
  • ma5209_a2 (last compiled 28 Aug 2025)
    (ma5209 assignment 1 Nguyen Ngoc Khanh - A0275047B March 2024 1 Problem 1 Define a category Ho(Top) in the following ...)
  • ma5209_a3 (last compiled 28 Aug 2025)
    (ma5209 assignment 3 Nguyen Ngoc Khanh - A0275047B March 2024 1 Problem 1 (a) Let p be a prime number ...)
  • ma5259_hw3 (last compiled 28 Aug 2025)
    (ma5259 hw3 Nguyen Ngoc Khanh - A0275047B November 2024 1 Q1 We roll a fair die repeatedly until the sum ...)
  • ma4271_hw1 (last compiled 28 Aug 2025)
    (MA4271 Homework 1 Khanh Nguyen August 2023 Problem 1 Let α : I →R3 be a parameterized smooth curve with ...)
  • ma5259_hw2 (last compiled 28 Aug 2025)
    (ma5259 hw2 Khanh Nguyen October 2024 1 Q1 Let ξ1, ξ2, ... be a sequence of i.i.d coin tosses with ...)
  • complex (last compiled 28 Aug 2025)
    (complex Khanh Nguyen May 2023 this is the note for my learning on complex analysis 1 Definition of complex numbers ...)
  • ma4261_hw1 (last compiled 28 Aug 2025)
    (ma4261 hw1 Nguyen Ngoc Khanh - A0275047B August 2024 1 Problem 1 Let [m] = {1, 2, ..., m}. A ...)
  • complex_analysis_ahlfors (last compiled 28 Aug 2025)
    (complex analysis ahlfors Khanh Nguyen December 2023 Chapter 1 COMPLEX NUMBERS 1 Chapter 2 COMPLEX FUNCTIONS 2 Chapter 3 ANALYTIC ...)
  • ma5210_a2 (last compiled 28 Aug 2025)
    (ma5210 assignment 2 Nguyen Ngoc Khanh - A0275047B August 2024 1 Questions 1-4 1.1 Question 1 Let A be an ...)
  • ma5205_chapter2_hw (last compiled 28 Aug 2025)
    (Chapter 2 HW Khanh Nguyen August 2023 3 If [a′, b′] is a subinterval of [a, b], show that P[a′, ...)
  • ma5209_a1 (last compiled 28 Aug 2025)
    (ma5209 assignment 1 Nguyen Ngoc Khanh - A0275047B February 2024 Problem 1. Let Ωbe an open subset of R2. Write ...)
  • ma5209_notes_ha (last compiled 28 Aug 2025)
    (homological algebra Khanh Nguyen April 2024 1 CATEGORICAL CONSTRUCTION OF HOMOLOGICAL ALGEBRA Definition 1 (initial object, terminal object, pointed category, ...)
  • zorn_lemma (last compiled 28 Aug 2025)
    (Zorn’s Lemma Nguyen Ngoc Khanh October 2023 Definition 1 (Partially Order Set) A partial order on a set X is ...)
  • conflict-based-search (last compiled 28 Aug 2025)
    (conflict-based-search nguyenngockhanh.pbc March 2021 Given a set of resources R and a set of k agents A. Each agent associates ...)
  • fyp (last compiled 28 Aug 2025)
    (Project No: SCSE19-0810 Cluster Analysis on Dynamic Graphs Submitted by: Nguyen Ngoc Khanh Matriculation Number: U1720451D Supervisor: Asst Prof Ke ...)
  • set_function (last compiled 28 Aug 2025)
    (On the set function in Rn the ideas of these proofs below are from MA5205 Graduate Analysis I instructed by ...)
  • 3_less_interesting

  • single_solution (last compiled 28 Aug 2025)
    (Given the problem: Minimize: f(x) subject to: c0(x) = n X i=1 xi = 1 and ci(x) = −xi ≤0 ...)
  • cycle (last compiled 28 Aug 2025)
    (cycle nguyenngockhanh.pbc April 2021 Is there an natural number function that always has a cycle and the cycle length is ...)
  • approximation-pattern (last compiled 28 Aug 2025)
    (approximation-pattern nguyenngockhanh.pbc March 2021 Consider the problem of minimizing a function f : D →R In many scenarios, it is ...)
  • two_sum (last compiled 28 Aug 2025)
    (Two-Sum Khanh Nguyen August 28, 2025 1 Preliminaries Let first define some data structures Denote [a, b] = {a, a ...)
  • test (last compiled 28 Aug 2025)
    (Find all functions f : [0, +∞) →[0, +∞) such that f(f(x)) + 3f(x) −270x = 133 For each real ...)
  • mapf-gp (last compiled 28 Aug 2025)
    (mapf-gp nguyenngockhanh.pbc January 2021 Contents 1 Chapter 1 Introduction Our central problem is defined as follow: Problem 1 (Problem 1). ...)
  • mapf-gp-summary (last compiled 28 Aug 2025)
    (mapf-gp-summary nguyenngockhanh.pbc March 2021 Contents 1 Chapter 1 Problem Decomposition 1.1 Problem Statement In the map of a specific location ...)
  • diffusion-convection (last compiled 28 Aug 2025)
    (Your Paper You August 28, 2025 Abstract Your abstract. 1 Introduction Your introduction goes here! Simply start writing your document ...)

My old documents

  • Aug 2024: My notes on differential manifolds: here
  • Aug 2024: My notes on probability theory and information theory: here
  • Jul 2024: My notes on adjunction in the book Tai-Danae Bradley, Tyler Bryson, John Terilla - Topology A categorical approach: here
  • Jun 2024: Some intuitions on filter in order and set: here
  • Jun 2024: Some notes on Topology - A categorical approach: here
  • Apr 2024: On homological algebra and algebraic topology: here
  • Oct 2023: On the set function: here
  • Sep 2023: Graduate Analysis notes: here
  • Aug 2023: Differential Forms and Stoke Theorem Notes: here
  • Aug 2023: Notion of compactness here
  • Aug 2023: (Terence Tao) Compactness and Compactification here
  • Jul 2023: Sidney A. Morris - Topology Without Tears here
  • Jun 2023: Harder problems in Topology Without Tears here
  • Jun 2023: Dan Saracino - Abstract Algebra: A First Course here
  • Jun 2023: Michael Penn - Complex Analysis here
  • Jun 2023: (Andrew Lin) Casey Rodriguez - MIT18.102: Introduction to Functional Analysis here
  • Apr 2023: Sum of measurable functions being measurable here
  • Apr 2023: Lyapunov function as a certificate for stability here
  • Mar 2023: A tutorial on Principle Component Analysis here
  • Jan 2022: The proof of Paxos algorithm here
  • Sep 2021: A proof for triangle inequality here
  • May 2021: From Mass-Spring Systems to Spectral Graph Neural Networks here
  • Mar 2021: Conflict based search here
  • Mar 2021: An approximation pattern here