Curved Geometry Forces Matter to the Edge

What is it about?

In textbook quantum physics, we expect particles and waves to spread out evenly in space for the "total amount" of matter to remain constant over time. However, a modern extension of quantum physics, known as non-Hermitian quantum physics, predicts the possibility of counterintuitive behaviors. One is the skin effect, where matter behaves as if it’s on a one-way street, piling up particles at a single boundary or edge of a system. Another is non-unitary evolution, where particles seem to appear or disappear, seemingly violating energy conservation. These non-Hermitian phenomena arise when considering "open systems", that is, materials constantly leaking or absorbing energy or matter from an external environment. This research reveals that we don't actually need an external environment to see these effects. Instead, the curvature of spacetime itself can do the work. By changing the geometric "metric" of the environment, the laws of physics naturally shift, forcing matter to aggregate at the edges or to appear or disappear out of the blue. It is like a marble rolling to a corner, not because someone pushed it, but because the floor itself is warped. Or measuring the length of an object with a rubber ruler that stretches over time, such as the "total amount" of matter appears to grow or shrink simply because the ruler itself is changing its scale. This provides a new bridge between Einstein’s general relativity and modern quantum materials.

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Photo by Steve A Johnson on Unsplash

Photo by Steve A Johnson on Unsplash

Why is it important?

One cannot easily observe how a particle behaves in the intense curvature gradients near a singularity or a black hole, or warp the spacetime in a laboratory. However, one can create an effective or artificial curvature by carefully designing the connections in a circuit, or the arrangements of atoms in a lattice, making particles "feel" as if they are moving through a warped spacetime. This allows us to use laboratory-scale "skin effects" to make predictions about the most extreme environments in the universe.

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