Let $F$ be a field of characteristic $p>0$. We prove that if a symbol $A=\omega \otimes \beta_1 \otimes \dots \otimes \beta_n$ in $H_{ p^m}^{ n+1}(F)$ is of exponent dividing $p^{ m-1}$, then its symbol length in $H_{ p^{ m-1}}^{ n+1}(F)$ is at most $p^n$. In the case $n=2$ we also prove that if $A= \omega_1\otimes \beta_1+\cdots+\omega_r\otimes \beta_r$ in $H_{ p^{ m}}^2(F)$ satisfies $\exp(A)|p^{ m-1}$, then the symbol length of $A$ in $H_{ p^{ m-1}}^2(F)$ is at most $p^r+r-1$. We conclude by looking at the case $p=2$ and proving that if $A$ is a sum of two symbols in $H_{ 2^m}^{ n+1}(F)$ and $\exp A |2^{ m-1}$, then the symbol length of $A$ in $H_{ 2^{ m-1}}^{ n+1}(F)$ is at most $(2n+1)2^n$. Our results use norm conditions in characteristic $p$ in the same manner as Matrzi in his paper ``On the symbol length of symbols''.
Categories: math.RA