I've been busy elsewhere with standard-model numerology. But it's time to think again about more traditional reasons for going beyond the standard model, too: observed phenomena that it doesn't accommodate. In a sense that has been the theme of this blog. However, one has to be wary; many, even most, such claims are eventually abandoned. Not many people are talking today about Weniger's 130 GeV gamma ray line, for example.
So let's remind ourselves what are the core examples of observations outside the standard model. They are neutrino masses, dark matter, and dark energy. For a physicist whose aim is an exact theory making precise predictions, the data on neutrino masses and mixings is okay, one knows more or less what to aim at.
But the nature of the evidence for dark matter is a lot more complicated. It involves heterogeneous observations which then have to be interpreted in a rather "theory-laden" manner. An outsider might not even know where to begin.
So it's convenient that particle-physics blogger "Jester" lists the following reasons to believe in dark matter: "galactic rotation curves, dynamics of galaxy clusters, large scale
structure, CMB peaks, bullet cluster, baryon acoustic oscillations". There we have a checklist of the data that a dark-matter theorist (or even a theorist who is going to explain it all without dark matter) needs to take into account.
The list could then be further rounded out or complemented by a look at the talking points in recent papers by Pavel Kroupa, a prominent dark-matter skeptic.
