The vignette "Translating lme4 models to sommer" of the sommer package explains
fm1 <- lmer(Reaction ~ Days + (0 + Days | Subject), data=DT)
as
"This is the a model where you assume that the random effect has different intercepts based on the levels of another variable but there’s not a main effect. The 0 in the intercept in lme4 assumes that random slopes interact with an intercept but without a main effect."
As I understand, the above model specification suggests a random slope effect of Days nested in Subject, but the random intercept variance is forced to 0, meaning that all Subjects have identical intercept. I do not quite understand why the sommer vignette states "the random effect has different intercepts".
Please let me know if my understanding is somewhere problematic.
