The paper introduces SpecGap, an approach for out-of-distribution (OOD) detection on graphs by analyzing Laplacian eigenvalue gaps.
It observes that OOD graph samples often show anomalous spectral gaps, prompting the development of SpecGap that adjusts features based on the differences in eigenvalues.
SpecGap is a parameter-free post-hoc method that can be seamlessly integrated into existing graph neural network models for improved OOD detection.
The approach achieves state-of-the-art performance on various benchmark datasets, supported by ablation studies and theoretical analyses.