181,336 research outputs found

    Motivic Landweber exact theories and their effective covers

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    Let kk be a field of characteristic zero and let (F,R)(F,R) be a Landweber exact formal group law. We consider a Landweber exact TT-spectrum E:=RLMGL\mathcal{E}:=R\otimes_{\mathbb{L}}\text{MGL} and its effective cover f0EEf_0\mathcal{E}\to \mathcal{E} with respect to Voevodsky's slice tower. The coefficient ring R0R_0 of f0Ef_0\mathcal{E} is the subring of RR consisting of elements of RR of non-positive degree; the power series FR[[u,v]]F\in R[[u,v]] has coefficients in R0R_0 although (F,R0)(F,R_0) is not necessarily Landweber exact. We show that the geometric part Xf0E(X):=(f0E)2,(X)X\mapsto f_0\mathcal{E}^*(X):=(f_0\mathcal{E})^{2*,*}(X) of f0Ef_0\mathcal{E} is canonically isomorphic to the oriented cohomology theory XR0LΩ(X)X\mapsto R_0 \otimes_{\mathbb{L}} \Omega^*(X), where Ω\Omega^* is the theory of algebraic cobordism, as defined by Levine-Morel. This recovers results of Dai-Levine as the special case of algebraic KK-theory and its effective cover, connective algebraic KK-theory.Comment: 23 pages. Corrections to the proof of lemma 3.5 (formerly lemma 3.6). Proof of the main theorem 6.2 (formerly theorem 6.3) reorganised. Minor changes to the introduction and the proofs of proposition 3.8 and theorem 3.9. Some unnecessary material removed from sections 4 and 5. Title is changed: "connective" replaced by "effective". arXiv admin note: text overlap with arXiv:1212.022

    A Public Voice for Youth: The Audience Problem in Digital Media and Civic Education

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    Part of the Volume on Civic Life Online: Learning How Digital Media Can Engage Youth.Students should have opportunities to create digital media in schools. This is a promising way to enhance their "civic engagement," which comprises political activism, deliberation, problem-solving, and participation in shaping a culture. All these forms of civic engagement require the effective use of a "public voice," which should be taught as part of digital media education. To provide digital media courses that teach civic engagement will mean overcoming several challenges, including a lack of time, funding, and training. An additional problem is especially relevant to the question of public voice. Students must find appropriate audiences for their work in a crowded media environment dominated by commercial products. The chapter concludes with strategies for building audiences, the most difficult but promising of which is to turn adolescents' offline communities -- especially high schools -- into more genuine communities

    Unemployment Through Layoffs: What Are the Underlying Reasons?

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    CRS_April_2005_Unemployment_Through_Layoffs.pdf: 6598 downloads, before Oct. 1, 2020
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