I´ve just started to study superstrings and I´m working on Polchinski´s book problems. I come from other area and so I´m not used to work with group theory what makes a little difficult to me to understand the solution of exercise 1.5. The solution says that the states with [tex]m^2 =1/ \alpha ´[/tex] form complete representations of SO(D-1), D=26. It is because the states are [tex]\alpha^{i}_{-2} \vert 0,k>[/tex], that are vectors of SO(D-2) and [tex]\alpha^{i}_{-1} \alpha^{j}_{-1} \vert 0,k>[/tex], that are tensors of SO(D-2) and they add up to a representation of SO(D-1). I´ve been trying to understand this, but I couldn´t yet. Why [tex]\alpha^{i}_{-2} \vert 0,k>[/tex] are vectors of SO(D-2) and why [tex]\alpha^{i}_{-1} \alpha^{j}_{-1} \vert 0,k>[/tex] are tensors of SO(D-2)? I know just the basics of representation theory for Lie Groups. Can anyone help me and explain it? I´m sorry for such a basic question, but I´m just a begginer in these matters...(adsbygoogle = window.adsbygoogle || []).push({});

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# Beginner´s Question on Bosonic Open Strings

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