= Bosonic string theory
{wiki}
<Bosonic> string theory quantizes a relativistic <string> with <bosonic> <worldsheet> matter fields. In the ordinary flat critical theory, the <worldsheet Weyl anomaly> cancels in 26-dimensional target <spacetime>: the embedding fields contribute <central charge> $26$ and the reparameterization ghosts contribute $-26$.
Its <string oscillators> generate a tower of <particle> states. The closed-string massless sector includes a <graviton>, a <Kalb–Ramond field> and a <dilaton>, making the theory a useful model of how <gravity> emerges from a string spectrum. Its <ground state> is a <tachyon>, indicating an instability of the chosen vacuum rather than ordinary faster-than-light signalling. The absence of <spacetime> <fermions> and this instability limit its direct phenomenological use, but its quantization exposes many mechanisms shared by more elaborate <string theories>.<String Theory by David Tong>[Sections 1.3 and 2.3: critical dimension, anomaly cancellation and the bosonic spectrum]{ref}
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