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    • CommentAuthorYemon Choi
    • CommentTimeFeb 22nd 2011
     

    I have a question which is, to a large extent, a more focused version of the existing question Homological Algebra texts

    To be more precise: a student, at the precocious undergraduate/starting graduate level, has asked me to recommend some material for learning homological algebra. He seems at the moment to be interested in algebraic topology and diff. geometry, which is not how I came to learn hom alg, and I am therefore slightly uncertain which of the many options would be best. So what I would like to ask is something like the following:

    I am looking for a recommendation of one or two books on homological algebra, which would be accessible to an advanced undergraduate/beginning graduate student (North American level) and which would complement the student's existing interest & self-taught progress in algebraic topology & diff geometry . Ideally, I would like people answering this question to have used their recommended text for teaching, or else used it themselves in graduate studies; and I am after a text which will connect to applications in topology/geometry. The two I am currently looking at (from which I gained most of my own small understanding of Hom Alg) are Hilton-Stammbach and Weibel: my worry is that the first, while accessible, is a bit old, while the second is more up-to-date but is quite diffuse, and assumes familiarity with some examples from algebra that the student might not have covered.

    Do people think that this question will elicit any new information not hitherto stated in the answers to Homological Algebra texts?

    • CommentAuthorMariano
    • CommentTimeFeb 22nd 2011
     

    It would help if you explained what s/he wants to get out of a textbook on homological algebra. Bott-Tu is a great book for someone with those interests, which does quite a bit of homological algebra without saying so and makes for an extraordinary introduction to spectral sequences, for example. I have recommended that book to people who thought they wanted to learn homological algebra, after finding out that they didn't...

    • CommentAuthorYemon Choi
    • CommentTimeFeb 22nd 2011
     

    Well, I don't know the student all that well, and (especially since he is still an undergraduate) what he thinks he ought to learn may turn out not to really be what he wants or needs. He's already worked through most of the stuff in Munkres' book on Alg Top (not something I ever did) and we will be meeting to discuss what he wants to get out of any such reading. But since he specifically asked about homological algebra (rather than, say, spectral sequences) I wanted to have some suggestions to hand.

    • CommentAuthorHarry Gindi
    • CommentTimeFeb 22nd 2011 edited
     

    @Yemon: From the alg. top. perspective, homological algebra is naturally interpreted as a special case of homotopical algebra, and for that, I know of practically no better references than Quillen's original paper and Hovey's book (for an introduction. It is then worthwhile to look over, say, Hirschhorn's book, which has fewer examples but develops the theory with a substantial amount more depth (I would say that it is now the standard reference on model categories).).

  1.  
    I took a course this past fall that was done out of Rotman, the springer behemoth. I really like that book. He includes a lot of basic material for people who have not thought a lot about modules, but it can be skimmed quickly. I really think it is an excellent book that does what you might be looking for. It is more modern, but not too advanced. I also found what he has to say about sheaves very helpful. It looks huge, but it does not need to be read linearly.
    • CommentAuthorShevek
    • CommentTimeFeb 23rd 2011
     
    Harry's idea that the student should get a book on model categories is terrible! (for hopefully obvious reasons...)
    • CommentAuthorHarry Gindi
    • CommentTimeFeb 23rd 2011 edited
     

    @Shevek: In your infinite wisdom, perhaps you could explain why it's a terrible idea =p. Have you actually read Quillen's Homotopical Algebra?

    • CommentAuthorajtolland
    • CommentTimeFeb 23rd 2011
     
    @ Yemon: Mirkovic has some lecture notes on homological algebra that might be suitable. http://www.math.umass.edu/~mirkovic/A.COURSE.notes/3.HomologicalAlgebra/HA/HA.html . They're not detailed, but might be helpful for seeing the forest for the trees.

    Frankly, that homological algebra textbook should have been [closed]. It's so broad that it's basically pointless.
    • CommentAuthorShevek
    • CommentTimeFeb 23rd 2011
     
    It should be obvious, but looking through the lens of the modern homotopical framework is not the best way to get a first handle on homological algebra, especially for a young student interested in algebraic topology/differential geometry. Seriously. Personally, I _love_ the modern point of view on homotopy but (no offense intended) your suggestion struck me as particularly detached from reality :) Also, model categories are most important for people _outside_ algebraic topology rather than for algebraic topologists themselves (there are exceptions of course), and I don't know of any examples of them being important in differential geometry.

    And yes I've read both Hovey's book and Quillen's. Personally, I've found all of Quillen's works (not only Homotopical Algebra, but his work in Higher K-theory too) to be very nice and still worth reading.
  2.  

    Personally, I love the modern point of view on homotopy but (no offense intended) your suggestion struck me as particularly detached from reality

    Yeah, but that's not an argument. I also disagree with your premise that:

    Also, model categories are most important for people outside algebraic topology rather than for algebraic topologists themselves (there are exceptions of course), and I don't know of any examples of them being important in differential geometry.

    I don't know what to make of it. Your contention is certainly false for homotopy theorists.

    • CommentAuthorShevek
    • CommentTimeFeb 23rd 2011
     
    Actually, no Harry. My sentence is true (to the extent that a remark of a subjective nature can be). I think you may be endowing yourself with an authority on algebraic topology (and homotopy theory) that you do not possess. The primary thing that model categories have given algebraic topology proper is a clarification of the relationship (well, equivalence) between classical algebraic topology of topological spaces and the homotopy theory of simplicial sets. Of course, these days, with the expansion of homotopical ideas into many diverse branches of mathematics, not all homotopy theorists are algebraic topologists.

    Also, I have no interest in "proving to you" that starting with model categories is not a good way for someone to start learning homological algebra, which is why my original remark was a single, unclarified sentence. I'm confident that my position is sufficiently obvious to others (if not to you personally).
    • CommentAuthorYemon Choi
    • CommentTimeFeb 23rd 2011
     

    Sigh. Rather than debate the question I was hoping to post on MO, could people please confine themselves to addressing my question here: is my intended MO question appropriate?

    Also, please do not take my silence as to some people's suggestions as agreement or disagreement.

    • CommentAuthorHarry Gindi
    • CommentTimeFeb 23rd 2011 edited
     

    I think you may be endowing yourself with an authority on algebraic topology (and homotopy theory) that you do not possess.

    Likewise.

    The primary thing that model categories have given algebraic topology proper is a clarification of the relationship (well, equivalence) between classical algebraic topology of topological spaces and the homotopy theory of simplicial sets.

    Are you not familiar with the whole area of stable homotopy theory as well as the many model structures on the many different categories of spectra? Are you suggesting that so-called categorical homotopy theory is not at all a branch of topology? It's easy to dismiss me because I'm arguing here on meta with my real name. If you'd like to call my suggestion into question and assert your own expertise in the matter, please use your real name. If not, then be quiet. I'd rather not be engaged by nameless critics.

    Also, I have no interest in "proving to you" that starting with model categories is not a good way for someone to start learning homological algebra, which is why my original remark was a single, unclarified sentence. I'm confident that my position is sufficiently obvious to others (if not to you personally).

    That's awfully conceited of you.

  3.  
    Sorry Yemen, I got distracted by other people posting actual suggestions. I think that if you can distinguish your question enough from the above linked question it would be fine to post. Unfortunately, I don't think the people that would argue to close as duplicate have yet posted here. For example, I don't have the requisite rep to vote to close anything. If I did, I would not vote to close, but I suppose that is little help...
    • CommentAuthorYemon Choi
    • CommentTimeFeb 23rd 2011
     

    Harry, please do not use this thread to argue with someone who disagrees with you about something off topic. Shevek, please don't poke with sticks.

  4.  

    @Yemon: I think your question is appropriate because the other question is garbage.

    • CommentAuthorMariano
    • CommentTimeFeb 23rd 2011
     

    (My post above was implicitly saying that I think the question is a nice one. But making explicit what the student wants to get out of the book would be good)

    • CommentAuthorajtolland
    • CommentTimeFeb 23rd 2011
     
    @ Yemon: What Mariano said. Actually helping a particular person makes these sorts of recommendation requests a lot more palatable.

    @ Harry: You aren't helping anyone.
    • CommentAuthorYemon Choi
    • CommentTimeFeb 23rd 2011
     

    @Mariano, @ajtolland: I will talk to the student tomorrow - but based on previous interaction, it may be hard for me to coax him into articulating specific goals. Most probably I will lend him a copy of Weibel to start with and see if that meshes with other courses or reading that he is currently engaged in. Thanks for the suggestions.

    • CommentAuthorEmerton
    • CommentTimeFeb 23rd 2011
     

    Dear Yemon,

    I think it would be good to post your question, because a list of intros. to homological algebra, somewhat focused, and with justifications in terms of the particular focus, would be a useful resource for many (not just your student).

    (Of course, I never vote to close, so I am not the one that you need to convince!)

    Best wishes,

    Matt

    • CommentAuthorHarry Gindi
    • CommentTimeFeb 23rd 2011 edited
     

    @ajtolland:

    I don't think I claimed that I was helping anyone. I was merely suggesting that Anonymous User Shevek "put up or shut up", because he has a history of anonymous nastiness on meta. I consider his dismissal of my suggestion with a snide remark to be a continuation of his behavior in other threads.

    If you're implying that my suggestion is unhelpful, then I respectfully disagree. Even though model categories don't cover every case of derived/triangulated categories (minor adjustments to the axioms allow us to cover them, however), that doesn't mean that it's not a worthwhile way to think about things. Homotopical algebra is no more abstract than homological algebra, and it provides an immense amount of motivation for it. Most of the constructions in homological algebra have their analogues in pointed and stable model categories (and Quillen's Homotopical Algebra discusses the pointed case and its relationship with homological algebra in depth).

    @Yemon: The only complaint I've heard about Weibel's book is that it doesn't discuss model categories (they are discussed in Gelfand and Manin, so what I'm saying isn't so outlandish). From the bits of it that I've read, it is pretty comprehensive, although the classical perspective on, for example, Ext, in Hilton-Stammbach is also extremely useful.

  5.  
    @Harry : I'm reluctant to get involved here, but I can't help myself. Though you're acting innocent, I think that even you know that it would be foolish to try to understand homotopical algebra before acquiring a serious understanding of homological algebra, algebraic topology, etc. Suggesting it just adds noise to the conversation.

    And this is not just an isolated incident. You frequently make wildly inappropriate suggestions when people ask for suggestions about books/subjects to study. You then proceed to give condescending lectures to people who disagree with you (eg "Are you not familiar with the whole area of stable homotopy theory..."). These people almost certainly are far more experienced and knowledgeable than you (I know this is true for Yemon, and from his comments I surmise that it is also true for Skevek). I have no idea why you continue to do this. Is this a lame attempt to impress us with how "hardcore" you are or how much math you know? Rest assured that it has the opposite effect.
    • CommentAuthorHarry Gindi
    • CommentTimeFeb 23rd 2011 edited
     

    You then proceed to give condescending lectures to people who disagree with you (eg "Are you not familiar with the whole area of stable homotopy theory..."). These people almost certainly are far more experienced and knowledgeable than you (I know this is true for Yemon, and from his comments I surmise that it is also true for Skevek). I have no idea why you continue to do this. Is this a lame attempt to impress us with how "hardcore" you are or how much math you know? Rest assured that it has the opposite effect.

    I did not lecture Yemon, because, as you say, he is far more experienced than I am in these matters and mathematics in general. My objections were made towards Shevek, who has made an argument that is as fatuous as it is condescending. I am pretty sure that I know who Shevek is, and if I'm right, then I refuse to defer to his "expertise".

    Edit: Actually, my mistake, here is who Shevek is: link to meta discussion where he revealed himself to be [[name removed by request - Anton]]. No offense to the gentleman, but I trust my judgement on this particular subject more than I trust his.

    @Harry : I'm reluctant to get involved here, but I can't help myself. Though you're acting innocent, I think that even you know that it would be foolish to try to understand homotopical algebra before acquiring a serious understanding of homological algebra, algebraic topology, etc. Suggesting it just adds noise to the conversation.

    Then I guess I'm a fool, because my introduction to homological algebra and algebraic topology was from the point of view of homotopical algebra. I find that these discussions are often dominated by people with extremely conservative views of the order in which one should approach particular mathematical subjects. If I had suggested that the person in question try to learn from Lurie's DAG I and learn about stable ∞-categories, then I would absolutely have deserved to be reprimanded. My suggestion is not nearly so outlandish.

    I would argue that trying to understand topics like the Dold-Kan correspondence, Eilenberg-Zilber, simplicial resolutions, André-Quillen cohomology, derived functors, derived categories, etc. are all more natural from a homotopical rather than a homological perspective. That is why I suggested what I did. I stand to gain nothing from "adding noise".

    • CommentAuthorajtolland
    • CommentTimeFeb 23rd 2011
     
    Harry,

    If you aren't trying to help, then why are you here?
  6.  
    @Harry : OK, let me be even more blunt. Mathematics is a very democratic subject in the sense that a proof is a proof, no matter who comes up with it. However, one has to earn the right to lecture experienced mathematicians about the proper foundations for their subject. Until you have done so, I'd recommend listening instead of shouting. Otherwise, you'll just make a fool of yourself (like you're doing right now).

    Developing good mathematical taste is, in many ways, much harder than learning mathematics. Given how many people with impeccable taste and broad views of the subject have criticized you throughout your time here on MO, wouldn't it be wise to reevaluate your position?

    With that, I've said all I want to say and will bow out of this conversation.
    • CommentAuthorHarry Gindi
    • CommentTimeFeb 23rd 2011 edited
     

    @Harry : OK, let me be even more blunt. Mathematics is a very democratic subject in the sense that a proof is a proof, no matter who comes up with it. However, one has to earn the right to lecture experienced mathematicians about the proper foundations for their subject. Until you have done so, I'd recommend listening instead of shouting. Otherwise, you'll just make a fool of yourself (like you're doing right now).

    I agree, and that's why I don't shout at people who know better. If you feel that I was shouting at you in my previous response, then I apologize, because that was not my intention. I was merely objecting to the idea that I was injecting noise into this conversation. I was trying to get across that my suggestions were absolutely sincere and based, at least, on my (however limited) experience.

    Developing good mathematical taste is, in many ways, much harder than learning mathematics. Given how many people with impeccable taste and broad views of the subject have criticized you throughout your time here on MO, wouldn't it be wise to reevaluate your position?

    I have many positions, many of which have been, and forgive me for understating this, controversial, but suggesting that I reconsider even those positions which haven't yet faced objections by experienced mathematicians is, dare I say, expecting a bit much.

    And not for nothing, I know of at least several serious mathematicians who only ever learned homological algebra from the homotopical point of view, although I don't know that I would say that their taste is completely beyond question.