Kaluza-Klein tower
= Kaluza-Klein tower
{c}
{title2=$m_n^2=M^2+n^2/R^2$}
For a field periodic on a circle of radius $R$, a <Fourier series> gives modes with quantized internal momentum $n/R$. Each mode is a lower-dimensional field with the displayed squared mass. The entire sequence is the tower; retaining only modes below a chosen energy gives an <effective field theory>. The tower is distinct from any individual <Kaluza-Klein mode>.