Understanding Time Crystals: A Beginner's Guide

[Hsopitalist]

TL;DR Summary

Trying to wrap my head around time crystals

Just read an article about time crystals. I understand regular crystals vary in a routine fashion through space but are unchanged over time. Time crystals apparently change periodically over time. I tried the usual googling but my brain has nowhere to put this. Can someone dumb this down for me?

 

[Drakkith]

I've never heard of this before. Do you have a reference to the article you read?

 

[Hsopitalist]

It was in the popular press referring to a paper in nature earlier this year about the first witnessed interaction between two time crystals. I will dig and see if I can find it.

 

[Hsopitalist]

https://www.independent.co.uk/life-...um-information-gps-atomic-clock-a9674401.html

 

[Drakkith]

Hmm. I don't think I can help you. This is the first time I've read about them. Perhaps someone else here can chime in.

 

[f95toli]

Try this article:

https://physicsworld.com/a/in-search-of-time-crystals/

 

[Demystifier]

Time crystal is a ground state periodically repeating in time. There is nothing strange about a state periodically repeating in time - think e.g. pendulum. What is strange about the time crystal is that it is a ground state. This means that it is stable, so, unlike a pendulum, it cannot decay to a lower energy state so it never stops.

 

[Filip Larsen]

Not sure if this is relevant, but some dissipative systems (for instance reaction-diffusion systems [1] like the BZ reaction [2]) can exhibit both regular spatial structure (e.g. Turing stripes and hexagons) as well temporal structure (e.g. Hopf oscillations [3]) for other system parameters.

Since such structures are limit cycles of the given system, I assume they could in some sense be said to exhibit a temporal "ground state" structure. Of course, just like a simple (dissipative) resonator these system needs energy to maintain their structure, so the interesting phenomenon in those examples is perhaps mostly that a fairly fixed "resonant" spatial or temporal structure form for a wide range of system parameters and not so much that the structures represent an energy ground state of a non-closed system.

[1] https://en.wikipedia.org/wiki/Reaction–diffusion_system
[2] https://en.wikipedia.org/wiki/Belousov–Zhabotinsky_reaction
[3] https://en.wikipedia.org/wiki/Hopf_bifurcation