Free Course Image Algebraic Topology Course

Free online courseAlgebraic Topology Course

Duration of the online course: 24 hours and 16 minutes

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Build a deeper intuition for shapes using singular homology. Join this free online course and learn key tools for proofs, computations, and math study.

In this free course, learn about

  • Main goals of algebraic topology: using algebraic invariants to classify spaces
  • Definition of singular homology via chain complexes of singular simplices and boundaries
  • What an n-simplex is and how simplices define singular chains and maps between spaces
  • Relative singular homology H_*(X,A), its new idea of studying a pair via quotient chains
  • Eilenberg–Steenrod axioms and how they characterize homology theories and computations
  • Compute homology of spheres (incl. H_*(S^1)) from axioms, and consequences like dimension
  • Induced maps on homology; example: reflection on spheres induces degree/sign on top homology
  • Snake Lemma and constructing long exact sequences; key consequences for pairs and maps
  • Long exact sequence of a pair and the connecting homomorphism in singular homology
  • Homotopy invariance: homotopic maps induce the same map on homology groups
  • Five Lemma: deducing isomorphisms in long exact sequence diagrams of abelian groups
  • Excision axiom and the small simplices lemma (barycentric subdivision) enabling excision
  • Degree-0 homology and what H_0 measures: path-connected components of a space
  • Mayer–Vietoris sequence (including pushouts): computing homology from decompositions

Course Description

Algebraic topology is where geometry meets algebra: you translate the features of spaces into algebraic objects that can be computed and compared. This free online course guides you through that translation with singular homology as the central tool, helping you move from pictures and intuition to rigorous, reusable methods. If you want a clearer way to distinguish spaces, detect holes, and understand when two shapes are essentially the same, this course gives you the framework to do it with confidence.

You start by building the language of singular homology from the ground up, including the role of simplices and the chain-level viewpoint that turns continuous problems into algebra. From there, the course develops relative homology so you can analyze a space together with a subspace, a perspective that becomes indispensable in real computations and in proofs that compare constructions. Along the way, you learn why axioms matter: the Eilenberg-Steenrod approach shows which properties characterize a homology theory and how these properties unlock results such as the homology of spheres and functorial behavior under maps.

A major theme is learning to navigate the machinery that makes homology powerful rather than mysterious. You work with induced maps, exactness, and core homological tools such as the snake lemma and the 5-lemma, gaining the ability to pass information through diagrams and conclude isomorphisms when direct computation would be difficult. Key structural principles like homotopy invariance clarify which features of a space are truly topological, while excision and the small simplices perspective explain why local modifications often do not change homology, paving the way for practical decompositions.

As your understanding matures, the course emphasizes computational strategy and conceptual connections. Degree zero homology provides a crisp algebraic lens on connectedness, while the Hurewicz viewpoint links homology with more geometric invariants and offers intuition for what homology is measuring. You also meet the triple sequence and see how relative homology can be reframed as absolute homology in suitable settings, improving flexibility when you tackle examples.

To tie everything together, Mayer-Vietoris becomes a central method: it shows how to compute the homology of a complicated space from simpler overlapping pieces, including versions suited to pushouts. By the end, you will be better equipped to read and write proofs in algebraic topology, understand standard theorems in a principled way, and approach new spaces with a reliable toolbox for breaking them apart and extracting invariant information.

Course content

  • Video class: 01 Introduction

    20m

  • Exercise: What is the main task of algebraic topology?

  • Video class: 02 Definition of singular homology

    1h03m

  • Exercise: What is an n-simplex?

  • Video class: 03 Definition of relative singular homology

    17m

  • Exercise: What New Concept Was Introduced in Relative Singular Homology?

  • Video class: 04 Eilenberg-Steenrod Axioms

    30m

  • Exercise: What is the primary use of the Eilenberg-Steenrod axioms in homology theory?

  • Video class: 05 Homology of spheres from the axioms

    44m

  • Exercise: What is the homology of a circle (S1)?

  • Video class: 06 Exemplary computation of an induced map

    25m

  • Exercise: What does the reflection map on spheres induce?

  • Video class: 07 The snake lemma

    39m

  • Exercise: What is the Snake Lemma in singular homology?

  • Video class: 08 The long exact sequence axiom in homology

    37m

  • Exercise: What is the main consequence of the Snake Lemma in singular homology?

  • Video class: 09 The homotopy invariance of singular homology

    1h00m

  • Exercise: What is the concept of homotopic invariance in singular homology?

  • Video class: 10 The 5-lemma

    08m

  • Exercise: What conclusion does the Five Lemma in homological algebra lead to?

  • Video class: 11 The excision axiom

    47m

  • Exercise: What is an essential aspect of the excision axiom in singular homology?

  • Video class: 12 The lemma of small simplices

    1h10m

  • Exercise: What is the primary purpose of barycentric subdivision in the proof of the small simplices lemma?

  • Video class: 13 The dimension axiom

    07m

  • Exercise: What is the result of the nth singular homology of a single point according to the dimension axiom?

  • Video class: 14 Further remarks on the Eilenberg-Steenrod axioms

    20m

  • Exercise: Which axiom does singular homology satisfy in relation to topological space decomposition?

  • Video class: 15 Singular homology in degree 0

    18m

  • Exercise: What does the zeroth singular homology reveal about a topological space?

  • Video class: 16 The Hurewicz isomorphism

    48m

  • Exercise: What does the Hurriwich Theorem in Degree One relate in topology?

  • Video class: 17 The triple sequence

    14m

  • Exercise: What is the concept behind the triple sequence in topology?

  • Video class: 18 Relative homology as absolute homology

    47m

  • Exercise: What is the relationship between reduced and unreduced homology for a point?

  • Video class: 19 Mayer-Vietoris sequence

    16m

  • Exercise: What is the purpose of the Mayer-Vietoris sequence in algebraic topology?

  • Video class: 20 Mayer-Vietoris sequence for pushouts

    08m

  • Exercise: Understanding the Excision Axiom in Homology

This free course includes:

24 hours and 16 minutes of online video course

Digital certificate of course completion (Free)

Exercises to train your knowledge

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Course comments: Algebraic Topology Course

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Venkata sree Rama murty maddula

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if u add the applications of it in classical and quantum computing very helpful

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