Title: University of Konstanz Physicists Solve Decades-Long Mystery of Glass’s Sound Behavior
Subtitle: Rediscovered Discarded Model Sheds Light on Glass’s Unique Vibratory Properties
Date: June 10, 2023
For the past 50 years, scientists have been puzzled by how glass conducts sound waves and vibrations differently than other solids at low temperatures. Now, two physicists from the University of Konstanz, Matthias Fuchs and Florian Vogel, have finally solved this longstanding mystery by revisiting and reworking an old, discarded model.
The behavior of glass at low temperatures has long perplexed physicists. Unlike other solids, glass exhibits unique vibratory behavior and carries sound waves differently. This distinct characteristic has been referred to as “glass vibrates differently.”
Fuchs and Vogel sought to uncover the reasons behind this behavior and find a way to accurately calculate the propagation of sound waves in glass. They decided to revisit an old model that was created approximately 20 years ago but was ultimately rejected by experts and forgotten. Their findings have been published in the journal Physical Review Letters.
One of the key observations made by the researchers was the damping of vibrations when sound waves are passed through glass. This damping effect has significant implications for the thermal properties of glass, such as heat transfer and heat capacities. Although well-known in physics, there was no accurate theoretical model to describe it until now, hindering more complex calculations related to sound propagation in glass.
The key difference between glass and crystalline solids lies in their particle arrangements. While crystalline solids have particles arranged in a precise lattice, the particles in glass are randomly positioned without a strict order. As a result, vibrations in glass do not propagate uniformly like a la-ola wave in a stadium but instead disperse into several smaller waves due to the random positions of the particles. This dispersion effect is what causes the damping in glass and is known as “Rayleigh damping,” named after physicist Lord Rayleigh who explained light scattering using a similar mechanism.
The breakthrough came when Fuchs and Vogel rediscovered a discarded model known as the “Euclidean random matrix approach” (ERM). This model, proposed by physicists Marc Mezard, Giorgio Parisi, Anthony Zee, and their colleagues, described the anomalies observed in glass oscillations due to random positions. Although the ERM model had inconsistencies and was overlooked in the past, Fuchs and Vogel resolved the open questions and examined the revised model using Feynman diagrams, which helped reveal regularities in the scattered wave patterns.
Fuchs emphasized the significance of this rediscovery, stating, “Mezard, Parisi, and Zee were correct in their insightful model – harmonic oscillations in a disordered arrangement explain the anomalies of glass at low temperatures.”
However, this rediscovered model is just the beginning of further research. Fuchs explains that the team now has a solid foundation to conduct more calculations, especially involving quantum mechanical effects, using the newly revisited model.
The study was funded by the German Research Foundation (DFG) through the Collaborative Research Centre SFB 1432 “Fluctuations and Nonlinearities in Classical and Quantum Matter beyond Equilibrium.”
With the glass conundrum finally solved, Fuchs and Vogel’s work will undoubtedly bring new insights into the behavior of glass and its applications in various fields, furthering scientific understanding and advancements.
Reference: “Vibrational Phenomena in Glasses at Low Temperatures Captured by Field Theory of Disordered Harmonic Oscillators” by Florian Vogel and Matthias Fuchs, published in Physical Review Letters on June 7, 2023. DOI: 10.1103/PhysRevLett.130.236101