[Math] How much algebra one needs to study algebraic topology and homotopy theory

algebraic-topologyhomotopy-theory

I wonder how much algebra(group theory, abstract algebra, linear algebra, ring theory, field theory) is assumed as a prerequisite in most of the modern algebraic topology text.
For example, these

J.Strom "Modern Classical Homotopy Theory"

Tammo tom Dieck "Algebraic Topology"

P.May "A Concise Course in Algebraic Topology.

Best Answer

The question highly depends on how deep you would like to go into algebraic topology.

If you are interested in learning algebraic topology as a general knowledge i.e. in the level of Hatcher's beafutiful book Algebraic Topology, then you probably need to know group, ring, and field theory, especially the structure of graded rings, and some basics of homological algebra such as $Ext$, and $Tor$. Note that there is actually no need to worry about homological algebra since all the required knowledge is introduced in that book when needed. Therefore, it is fair to say a good knowledge of abstract algebra should suffices to take a first course in algebraic topology.

If you would like to go further, such as studying stable homotopy theory, you probably want to have a good knowledge of category theory without which you could not even define the stable homotopy category which is central in algebraic topology. You also want to know more about homological algebra which enables you to study important topics like spectral sequences. You also need to learn about the theory of formal group laws to understand Quillen's celebrated theorem which establishes the relation between the universal complex oriented cohomology theory and the Lazard ring.

It is really hard to answer your question in the full completeness. What I mentioned in the above should only serve as a "necessary condition". Hope this answer helps.