High-energy heavy-nuclei collisions, conducted at particle colliders such as CERN’s Large Hadron Collider (LHC) and BNL’s Relativistic Heavy Ion Collider (RHIC) are able to produce a state of matter called a quark-gluon plasma (QGP).

A QGP is believed to have existed just after the Big Bang. The building blocks of protons and neutrons – quarks and gluons – were not confined inside particles as usual but instead formed a hot, dense, strongly interacting soup.

Studying this state of matter helps us understand the strong nuclear force, the early universe, and how matter evolved into the forms we see today.

In order to understand QGP created in a particle collider you need to know the initial conditions. In this case that is the shape and structure of the heavy nuclei that collided.

A major complicating factor here is that most atomic nuclei are deformed. They are not spherical but rather squashed and ellipsoidal or even pear-shaped.

Collisions of deformed nuclei with different orientations brings in a large amount of randomness and therefore hinders our ability to describe the initial conditions of the QGP.

A new method called imaging-by-smashing was developed by the STAR experiment at RHIC, where atomic nuclei are smashed together at extremely high speeds. By studying the patterns in the debris from these collisions, researchers can infer the original shape of the nuclei.

In this latest study, they compared collisions between two types of nuclei: uranium-238, which has a strongly deformed shape, and gold-197, which is nearly spherical.

The differences between uranium and gold helped isolate the effects of uranium’s deformation. Their results matched predictions from advanced hydrodynamic simulations and earlier low-energy experiments.

Most interestingly, they found hints that uranium might possess a pear-like (octupole) shape, in addition to its dominant football-like (quadrupole) shape. This feature had not previously been observed in high-energy collisions

This method is still new, but in the future, it could give us key insights nuclear structure throughout the periodic table. These measurements probe nuclei at energy scales orders of magnitudes higher than traditional methods, potentially revealing how nuclear structure evolves across very different energy regimes.

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In quantum mechanics, a quantum state is a complete description of a system’s physical properties.

If the system changes slowly and returns to its original physical configuration, then its quantum state also returns to its original form except for a phase factor.

In a pioneering work in 1984, physicist Michael Berry discovered that this factor can be separated into two parts: the dynamic and the geometric phase.

The usual dynamic phase depends on energy and time and was already well understood. The new part, the geometric phase (or Berry phase after its discoverer) arises purely from the geometry of the path that the state takes through parameter space.

The Berry phase has profound implications across physics, appearing in phenomena like the quantum Hall effect, molecular dynamics, and polarised light. It reveals deep connections between geometry, topology, and physical observables.

In a recent paper, this concept was extended from wave evolution to certain wave scattering events, where waves bounce off or pass through materials and their properties shift.

In order to do this, the authors used a mathematical tool called a scattering matrix. The matrix encodes all the possible outcomes of a scattering process – reflection, transmission, or deflection -based on the system’s properties.

They showed that these wave shifts can also be split into dynamic and geometric parts. Importantly this splitting can be done in such a way that doesn’t depend on arbitrary choices (i.e., it’s gauge-invariant).

The team demonstrated their idea with known examples like light passing through a changing waveplate, beams reflecting off surfaces, and time delays in 1D systems.

Their approach is not only able to describe known phenomena, but also reveals new physical features, provides new insights, and uncovers previously unnoticed connections.

Going forward, identifying the geometric and dynamic origins of various scattering-induced shifts offers new ways to control wave-scattering phenomena.

This could have applications in photonics, imaging, quantum computing, and micromanipulation.

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