Self-dual circle compactification
= Self-dual circle compactification
{title2=$R=\sqrt{\alpha'}$}
= Self-dual circle
{synonym}
A circle compactification is self-dual when the radius is unchanged by the <T-duality> map $R\mapsto\alpha'/R$. Momentum and winding then enter the <bosonic string mass spectrum> with equal weights. Special charge sectors can become massless at this radius.