Is Diffeomorphism on Target Space a Symmetry of Polyakov's Action?

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SUMMARY

The discussion centers on the symmetries of the Polyakov action, specifically questioning whether diffeomorphism on the target space is a symmetry. The Polyakov action is defined as S=\frac{1}{4\pi\alpha^\prime}\int d^2\sigma\sqrt{-h}h^{\alpha\beta}G_{ij}(X)\partial_\alpha X^i\partial_\beta X^j, which exhibits local symmetries including diffeomorphism on the world sheet and Weyl invariance. The transformation of the target space metric is given by G_{ij}(X)\to G_{ij}^\prime(X^\prime)=\frac{\partial X^k}{\partial X^i}\frac{\partial X^l}{\partial X^j}G_{kl}(X). The challenge lies in handling the term \partial_\alpha X^i\partial_\beta X^j, where the application of the chain rule is suggested as a potential solution.

PREREQUISITES
  • Understanding of the Polyakov action in string theory
  • Familiarity with local symmetries in theoretical physics
  • Knowledge of diffeomorphism and Weyl invariance
  • Proficiency in calculus, particularly the chain rule
NEXT STEPS
  • Research the implications of diffeomorphism invariance in string theory
  • Study the application of the chain rule in the context of field transformations
  • Explore the role of Weyl invariance in quantum field theory
  • Examine examples of target space metrics and their transformations
USEFUL FOR

The discussion is beneficial for theoretical physicists, particularly those specializing in string theory, as well as graduate students seeking to deepen their understanding of symmetries in physical actions.

synoe
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The Polyakov action,

<br /> S=\frac{1}{4\pi\alpha^\prime}\int d^2\sigma\sqrt{-h}h^{\alpha\beta}G_{ij}(X)\partial_\alpha X^i\partial_\beta X^j<br />

has the local symmetries, diffeomorphism on world sheet and the Weyl invariance.
But is diffeomorphism on the target space also a symmetry?
The target space metric transforms

<br /> G_{ij}(X)\to G_{ij}^\prime(X^\prime)=\frac{\partial X^k}{\partial X^i}\frac{\partial X^l}{\partial X^j}G_{kl}(X).<br />

But I don't know how to deal with the part, \partial_\alpha X^i\partial_\beta X^j.
 
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Apply the chain rule as usual, it should work.
 

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