Student Interpretations of Eigenequations in Linear Algebra and Quantum Mechanics

This work investigates how students interpret various eigenequations in different contexts for \(2 \times 2\) $2\times 2$ matrices: \(A\vec {x}=\lambda \vec {x}\) $A\overrightarrow{x}=\lambda \overrightarrow{x}$ in mathematics and either \(\hat{S}_x| + \rangle _x=\frac{\hbar }{2}| + \rangle _x\) ${\widehat{S}}_x{|+⟩}_x=\frac{ħ}{2}{|+⟩}_x$ or \(\hat{S}_z| + \rangle =\frac{\hbar }{2}| + \rangle\) ${\widehat{S}}_z|+⟩=\frac{ħ}{2}|+⟩$ in quantum mechanics. Data were collected from two sources in a senior-level quantum mechanics course; one is video, transcript and written work of individual, semi-structured interviews; the second is written work from the same course three years later. We found two principal ways in which students reasoned about the equal sign within the mathematics eigenequation and at times within the quantum mechanical eigenequations: with a functional interpretation and/or a relational interpretation. Second, we found three distinct ways in which students explained how they made sense of the physical meaning conveyed by the quantum mechanical eigenequations: via a measurement interpretation, potential measurement interpretation, or correspondence interpretation of the equation. Finally, we present two themes that emerged in the ways that students compared the different eigenequations: attention to form and attention to conceptual (in)compatibility. These findings are discussed in relation to relevant literature, and their instructional implications are also explored.