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I'll start with some motivating remarks (edit: as pointed out in the comments, these motivational remarks do not hold for surfaces: there is an example of a conic bundle surface over a real quadratic field with no rational points but non-empty etale-Brauer set). When it comes to obstructions to the Hasse principle or WA, it seems to me that we need to come up with a new obstruction every time we go up one dimension: it is likely that for curves (dimension 1) the Brauer-Manin obstruction (BMO) to HP or WA is, at worst, the only one; similarly, for surfaces (dimension 2), the BMO is not enough, but the descent obstruction (DO) to HP or WA might be the only one (edit: No, the DO is also not enough, as pointed out by Felipe Voloch and Martin Bright in the comments); we know that the descent obstruction to the HP for 3-folds is not enough (there is a counter-example due to Poonen), but there is probably some finer (yet) unknown obstruction which explains violations for 3-folds; and so on.

My question is on the state-of-the-art for the dimension 2 case:

Up to date, for which classes of nice surfaces do we know that the "Descent principle" (i.e. DO is, at worst, the only obstruction for HP and WA) holds?

Of course, the more general the class (e.g. rational, K3, Enriques, ...) and the number field, the better! I am already aware of some classes of surfaces for which the Descent principle holds (e.g. Chatelet surfaces over $\mathbb{Q}$, del Pezzo surfaces of degree $\geq 5$, ...), but the literature is too huge to keep track of everything. It goes without saying that references are greatly welcomed!

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    $\begingroup$ This paper has a two-dimensional counterexample in the vein of Poonen's. arxiv.org/abs/1310.5055 $\endgroup$ Sep 12, 2014 at 13:07
  • $\begingroup$ Thanks, I wasn't aware of that counter-example. I guess my main question still remains, even though the motivational remarks are rubbish now! $\endgroup$ Sep 12, 2014 at 13:14
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    $\begingroup$ Also here: arxiv.org/abs/1212.6019 $\endgroup$ Sep 12, 2014 at 13:21
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    $\begingroup$ See for example this paper. This is the culmination of many other works. Also, I would like to rephrase my previous comment. I think this question is slightly too broad for mathoverflow. This is an active area of research with many results, handing various special cases. It is not clear to me what answer you would like, and I don't think mathoverflow is the place to give a complete literature review. For example would "it is not known that the BM obstruction is the only one to the Hasse principle for K3 surfaces" suffice as an answer for you? $\endgroup$ Sep 12, 2014 at 16:23
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    $\begingroup$ I would recommend reading the FAQ and browsing through various MO questions to get an idea of the kind of questions which people ask here. Questions of the shape "What is known about X?" are generally frowned upon here. I won't deny that asking a "good" mathoverflow question is a bit of a skill that you have to learn. $\endgroup$ Sep 12, 2014 at 16:46

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