https://doi.org/10.1140/epjs/s11734-025-02022-y
Review
Review on recent progress in the study of the 
subthreshold singularity and the 
meson
Institute for Particle and Nuclear Physics, College of Physics, Sichuan University, 610065, Chengdu, Sichuan, People’s Republic of China
Received:
30
May
2025
Accepted:
11
October
2025
Published online:
31
October
2025
We summarize recent results on studies of 
and 
scatterings. They include the finding of a negative-parity nucleon pole with a mass lower than the nucleon mass, and the pole trajectory of 
as the pion mass varies. The results are obtained from model-independent dispersion analyses. We also study the thermal properties of based on the O(N) 
model and N/D method.
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© The Author(s), under exclusive licence to EDP Sciences, Springer-Verlag GmbH Germany, part of Springer Nature 2025
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
