arXiv subjects

Wenqing Xie

Publications and source records attributed to Wenqing Xie.

2 recordsLinked to original sources

arXiv2025

Revisiting Koehler's experiment of measuring the ratio of the specific heats of air by self-sustained oscillations

We revisit Koehler's experiment, a clever modification of Ruchardt's experiment designed to measure the ratio of specific heats of gas. However, the lengthy and dense analysis shared by Koehler in his 1950 paper may pose challenges to readers due to the complexity of the calculations. Following Koehler's approximation for pressure changes, we explicitly present the model equations as piecewise linear differential systems and qualitatively analyze the periodic solutions from a geometric perspective. This concise and transparent approach addresses a fundamental question about Koehler's experiment: why is the oscillation frequency nearly equal to the Ruchardt frequency? Our analysis avoids intricate calculations and should help educators introduce Koehler's experiment in general physics laboratory classes

physics.class-ph↗

arXiv2025

Unitary network: Tensor network unitaries with local unitarity

We introduce unitary network, an oriented architecture for tensor network unitaries. Compared to existing architectures, in a unitary network each local tensor is required to be a unitary matrix upon suitable reshaping. Global unitarity is ensured when the network obeys a suitable ordering property. Unitary operators represented by unitary networks need not preserve locality. In particular, we show that the class of unitary networks encompasses global unitaries which preserve locality up to exponentially suppressed tails, as in those that naturally arise from the finite-time evolution of local Hamiltonians. Non-invertible symmetries, as exemplified by the non-local Kramers-Wannier duality in one dimension, can also be represented using unitary networks. We also show that information flow in a unitary network can be characterized by a flow index, which matches the known index for quantum cellular automata as a special case.

quant-ph↗