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Language of science: The Berry Phase begets the Belly Phase

“The Berry Phase” is not the only Berry phrase.


Quantum physics turns (in more than one sense) on a concept called “the Berry phase“. The phrase, and in a way the concept, has recently given rise to a name for a phenomenon that occurs in your stomach: “the belly phase“.

(Note for quibblers: Yes, quantum physics does apply everywhere, including your stomach. So yes, “the Berry phase” does indeed pertain to your stomach in particular, as well as quantum physics in general.)

One and the same person — Professor Sir Michael Berry, FRS — bears full responsibility for identifying the Berry phase, and substantial responsibility for, three decades later, naming the belly phase. This is the paper in which Berry birthed the Berry phase:


What is the Berry phase? The concept takes a bit of explaining, if you are not intimately familiar with modern physics. Here are explanations from several different people: “Berry’s Geometric Phase — Introductory Lecture“; “The Berry phase“; “What is an intuitive explanation of the Berry phase?

What is the belly phase? A newly published paper, “Geometric Mixing, Peristalsis, and the Geometric Phase of the Stomach“, explains:

Mixing fluid in a container at low Reynolds number—in an inertialess environment—is not a trivial task. Reciprocating motions merely lead to cycles of mixing and unmixing, so continuous rotation, as used in many technological applications, would appear to be necessary. However, there is another solution: movement of the walls in a cyclical fashion to introduce a geometric phase.We show using journal-bearing flow as a model that such geometric mixing is a general tool for using deformable boundaries that return to the same position to mix fluid at low Reynolds number. We then simulate a biological example: we show that mixing in the stomach functions because of the “belly phase,” peristaltic movement of the walls in a cyclical fashion introduces a geometric phase that avoids unmixing….

We have shown that such a geometric phase—the “belly phase” [35]—may be found in the stomachs of animals where Re < 1.

[Footnote] 35. We are indebted to Michael Berry for this coinage.

Here is that paper:


Michael Berry is active in many fields of science. In the year 2000. he and fellow physicist Andre Geim were awarded an Ig Nobel Prize for physics, for using magnets to levitate a frog.

Michael Berry bears substantial responsibility, also for writing one of the shortest abstracts ever for a scientific paper:

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Improbable Research