Bosonic string mass spectrum
= Bosonic string mass spectrum
For a closed bosonic string,
$$
M^2=\frac4{\alpha'}(N-a)=\frac4{\alpha'}(\widetilde N-a),
\qquad N=\widetilde N.
$$
= Bosonic string mass spectrum
For a closed bosonic string,
$$
M^2=\frac4{\alpha'}(N-a)=\frac4{\alpha'}(\widetilde N-a),
\qquad N=\widetilde N.
$$