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“Processing is an open source programming language and environment for people who want to program images, animation, and interactions.”\x0a
I am a Ph.D. candidate since 16:30 today! Hurray!
\x0aby Kwan Choi.
\x0aby Aarti Singh, Robert Nowak, and Xiaojin Zhu.
\x0aWhy Achievement is not normal?
\x0aFirst we need the definition of Hölder and Sobolev spaces (Wikipedia).
\x0aThe idea of Hölder spaces is that the k-th derivative of the functions are alpha-Lipschitz. The idea of Sobolev spaces is that the k-th derivate of the functions are in Lp space.
\x0aThen we have different Sobolev inequalities. These inequalities basically say which Sobolev space can be embedded in another one. Of course, if two spaces are measured with the same Lp norm, the one with higher degree of smoothness can be embedded in the less smooth one. But if we measure one with Lp and measure the other with Lq (p!=q), then the relation is more complicated and depends on p, q, smoothness degrees and the dimension n of the space R^n.
\x0aThen we have interesting Gagliardo-Nirenberg-Sobolev inequality which says for diff. function u: R^n —>R, ||u||_Lp* <= C || D u ||_Lp where p* is the Sobolev conjugate of p, and D is the differentiation operator.
\x0aNow, we have Besov spaces. As far as I understand, there are different ways to define it: Fourier (or Wavelets)-based approach and moduli of smoothness approach.
\x0aFor example, see DeVore, Sharpley, “Besov Spaces on Domains in R^d” (Section 2).
\x0aJan Schneider, Function Spaces with Varying Smoothness, Ph.D. Dissertation.
\x0aIt starts by Fourier-analytical approach to define Besov spaces in R^n (Definition 2.1), reviews some embedding theorem (Theorem 2.2), and equivalent of some norms (Theorem 2.3) in Besov spaces. Then it defines the same thing for domains \\Sigma \\subset R^n, and proves similar results. Afterwards, it generalizes the same result to the case where the smoothness measurement changes. The motivation is that this way is better to capture pointwise singularities. Again, similar properties hold.
\x0aAnd finally a few other references:
\x0aFrayssee and Jaffard, “The Sobolev Embeddings are Usually Sharp”.
\x0aI am not sure if understand the paper correctly, but this is my take from its Introduction: For a Sobolev space W^s(Lp)(R^n), there exists a function belong to that space which has a Holder exponent of s - d/n (the Holder exponent more or less show the maximum pointwise smoothness of the function). Now, the question is whether this function belonging to the aforementioned Sobolev space is an exception or actually most functions in that Sobolev space has this Holder exponent of s - d/n.
\x0aScholkopf, Herbrich, Smola, “Generalized Representer Theorem”.
\x0a\x0aThe theorem is quite general: for an arbitrary loss function L(.) that depends on data x_1,…,x_m, and regularizer in the form of g(||f||) with g(.) as strictly monotonic increasing, we have the usual expansion in the form of f(.) = \\sum_{i=1}^m a_i k(.,x_i) .
\x0aAlso the Remark 6, biased regularization, is quite interesting. I thought people had not considered it before!
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