Spectral Evolution Responsible for the Transition from Positive Lags to Negative Lags in Gamma-Ray Bursts

It was well known that most of gamma-ray bursts (GRBs) are dominated by positive spectral lags, while a small fraction GRBs show negative lags. However, Wei et al. firstly identified well-defined transition from lags to in GRB 160625B, and then got robust limits on possible violation Lorentz Invariance (LIV) based the observation. Recently, such has been found three different emission episodes \thisgrb Gunapati al., which provides us great opportunity investigate whether results LIV-induced observed Our analysis shows LIV model can not be compatible with current observations, whereas, only evolution induced could responsible for transition. So, also explain lag 190530A.