Directional Tangency and Anomalous Far-Field Decay for Schr{ö}dinger Equations
Abstract
We identify a directional tangency mechanism responsible for anomalous far-field decay in Schrödinger equations. For constant-coefficient operators, we introduce a directional decomposition of the limiting resolvent based on the geometry of the Fermi surface and the observation direction. In two dimensions, we show that an analytic source produces a super-algebraically small tangency contribution, whereas a transverse non-analyticity located on the directional tangency set generates an algebraic contribution of order R−(2α+1). Shifting the singularity away from the tangency set restores super-algebraic decay, showing that geometric alignment is essential to the anomalous behavior. We further construct a bounded, decaying real-valued potential for which the same mechanism occurs in the first Born correction through the effective source Vu0. In a suitable long-range regime, the resulting tangency contribution decays more slowly than the conventional two-dimensional far-field term.
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BibTeX
@misc{zhang2026directional,
title = {{Directional Tangency and Anomalous Far-Field Decay for Schrödinger Equations}},
author = {Ruming Zhang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.23472},
eprint = {2609.23472},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.23472},
note = {CC0},
}
RIS
TY - UNPB
TI - Directional Tangency and Anomalous Far-Field Decay for Schr{ö}dinger Equations
AU - Ruming Zhang
PY - 2026
DA - 2026/09/20
PB - arXiv
DO - 10.48550/arxiv.2609.23472
UR - https://arxiv.org/abs/2609.23472
AB - We identify a directional tangency mechanism responsible for anomalous far-field decay in Schrödinger equations. For constant-coefficient operators, we introduce a directional decomposition of the limiting resolvent based on the geometry of the Fermi surface and the observation direction. In two dimensions, we show that an analytic source produces a super-algebraically small tangency contribution, whereas a transverse non-analyticity located on the directional tangency set generates an algebraic contribution of order R^−(2α+1). Shifting the singularity away from the tangency set restores super-algebraic decay, showing that geometric alignment is essential to the anomalous behavior. We further construct a bounded, decaying real-valued potential for which the same mechanism occurs in the first Born correction through the effective source Vu_0. In a suitable long-range regime, the resulting tangency contribution decays more slowly than the conventional two-dimensional far-field term.
ER -