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Paper Explainer: Hiding Thermal Dark Matter with Leptons

14 May 2017, 00:26 UTC
Paper Explainer: Hiding Thermal Dark Matter with Leptons
(200 words excerpt, click title or image to see full post)

This is a description of my recent paper with my student David Feld. Dark matter is a problem. We know that there is a gravitational anomaly in galaxies: the stuff we can see is moving far too fast to be held together by its own gravity. Add to this the precision measurements of the echoes of the Big Bang (the Cosmic Microwave Background), which tells us that the way the Universe was expanding and matter was clumping cannot be explained without some new stuff that didn’t interact with light, and you have very solid evidence for the existence of dark matter. Then of course, there is the Bullet Cluster, where we can see the gravitational imprint of dark matter directly.So we know it exists. We just don’t know what it is.There are, of course, many ideas. Ideas are, after all, theoretical physicists’ stock in trade. One very good idea is that dark matter is a thermal relic. When the Universe was very young, it was very dense and very hot, so every particle zipping around had enough energy that, when they banged into other particles, they could create other very massive particles. The heavy particles themselves would smash into each ...

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