# Thermalization in non-disordered systems

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The eigenstate thermalization hypothesis explains the mechanism of the thermalization of generic many-body quantum systems. The presence of disorder, on the other hand, provides an elegant example of many-body quantum properties that fail to thermalize and thus violates the ETH. I am wondering if there are quantum systems that violate ETH without disorder?

asked Jan 18, 2020

Many-electron atoms will do?

## 1 Answer

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Yes, there are many-body quantum systems that are not disordered, but which also violate ETH. Perhaps the most prominent examples are Bethe-Ansatz integrable systems (mentioned prominently in this review).

However, all such examples of many-body systems without disorder which do not obey ETH are, to my knowledge, finely tuned. That is to say, if H is clean and fails to satisfy ETH, then I expect (and I don't think I'm alone) that ETH will start to hold if you add small perturbations to H which are local, translation invariant, and sufficiently generic. I don't know of any rigorous results backing up this expectation...so it might not be correct! But that would be surprising.

answered Feb 16, 2020 by (40 points)
edited Feb 16, 2020 by Curt vK

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