User dan isaksen - MathOverflow most recent 30 from http://mathoverflow.net 2013-05-26T09:02:33Z http://mathoverflow.net/feeds/user/13856 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/120197/adams-novikov-spectral-sequence-at-p-2 Adams-Novikov spectral sequence at p = 2 Dan Isaksen 2013-01-29T11:09:46Z 2013-01-29T12:50:34Z <p>Does anyone know of any computer calculations of the E2-term of the Adams-Novikov spectral sequence at p=2?</p> <p>I'd love to get my hands on this data.</p> http://mathoverflow.net/questions/60575/explicitly-construct-generators-of-homotopy-groups-of-spheres/60582#60582 Answer by Dan Isaksen for Explicitly construct generators of homotopy groups of spheres Dan Isaksen 2011-04-04T18:05:44Z 2011-04-04T18:05:44Z <p>The answer partly depends on your definition of "explicit generator". The Hopf maps $\eta$, $\nu$, and $\sigma$ have explicit constructions. After that, things get messier. One way to describe the generators is with Toda brackets (see Toda, Composition methods in homotopy groups of spheres). </p> <p>For example, the element often called $\epsilon$ in $\pi_8$ can be described with the bracket $\langle \eta, 2, \nu^2 \rangle$. </p> <p>One word of caution regarding Toda brackets: beware of the indeterminacies.</p> http://mathoverflow.net/questions/59319/computing-squaring-operations-in-the-adams-spectral-sequence Computing squaring operations in the Adams spectral sequence Dan Isaksen 2011-03-23T16:45:55Z 2011-03-29T16:21:34Z <p>This question is about the classical Adams spectral sequence. Squaring operations are defined on its $E_2$ term. I'd like to know how to compute some of the non-trivial operations, such as $Sq^2 ( c_0 ) = h_0 e_0$. I feel like this ought to be doable in the May spectral sequence, but I don't know the details.</p> <p>I'm aware of some work of Milgram on the subject, but there are some problems with his approach because of indeterminacies of Massey products.</p> <p>Thanks!</p> http://mathoverflow.net/questions/120197/adams-novikov-spectral-sequence-at-p-2/120204#120204 Comment by Dan Isaksen Dan Isaksen 2013-01-31T17:46:16Z 2013-01-31T17:46:16Z Unfortunate for my purposes, but good to know! http://mathoverflow.net/questions/61413/topological-space-associated-to-a-real-or-complex-scheme Comment by Dan Isaksen Dan Isaksen 2011-04-13T11:04:40Z 2011-04-13T11:04:40Z The space $R_{\mathbb{R}}(X)$ has points consisting of maps Spec $\mathbb{C} \rightarrow X$ over $\Spec \mathbb{R}$. So complex conjugation induces an involution. The natural target for $R_{\mathbb{R}}$ is $\mathbb{Z}/2$-spaces, i.e., spaces equipped with an action of $\mathbb{Z}/2$. http://mathoverflow.net/questions/60575/explicitly-construct-generators-of-homotopy-groups-of-spheres Comment by Dan Isaksen Dan Isaksen 2011-04-04T18:01:37Z 2011-04-04T18:01:37Z Another reference for the Postnikov tower / Serre spectral sequence approach is Mosher and Tangora, Cohomology operations and applications in homotopy theory. http://mathoverflow.net/questions/59319/computing-squaring-operations-in-the-adams-spectral-sequence Comment by Dan Isaksen Dan Isaksen 2011-03-25T13:51:55Z 2011-03-25T13:51:55Z Because of Bob Bruner's computer calculations, I know what the answers ought to be. But I'm looking for a conceptual way of obtaining the answers.