Orientability of Null Submanifold w/ Boundary - Stokes' Theorem

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SUMMARY

The discussion centers on the orientability of null submanifolds with boundaries and the applicability of Stokes' theorem in this context. It is established that while orientability is a topological property, volume forms depend solely on the affine structure, allowing Stokes' theorem to hold even when the metric is degenerate. However, complications arise when dealing with curvature and nonscalar integrands, as these can hinder the ability to define vector addition across different tangent spaces. The reference to Carroll's work provides additional insights into these concepts.

PREREQUISITES
  • Understanding of null submanifolds in differential geometry
  • Familiarity with Stokes' theorem and its applications
  • Knowledge of volume forms and affine structures
  • Basic concepts of curvature in Riemannian geometry
NEXT STEPS
  • Study the implications of Stokes' theorem in the context of null submanifolds
  • Explore the properties of volume forms on affine manifolds
  • Investigate the role of curvature in the integration of differential forms
  • Read Chapter 2 of Carroll's "Spacetime and Geometry" for a deeper understanding of these concepts
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Mathematicians, physicists, and students of differential geometry interested in the properties of null submanifolds and the application of Stokes' theorem in complex geometrical contexts.

ifidamas
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I have this question: Is it possible to define an orientation for a null submanifold with boundary?
In that case, is possible to use Stokes' theorem?
In particular, there is a way to define a volume form on that submanifold?
 
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Orientability is topological. Volume forms only depend on affine structure. None of these notions are metrical, so it doesn't matter if the metric is degenerate on your submanifold. Stokes' theorem still holds. There is a good discussion of this sort of thing at the end of ch. 2 of the free online version of Carroll, http://arxiv.org/abs/gr-qc/?9712019 .

The only thing to worry about is that if there's curvature and the integrand is nonscalar (e.g., the flux of stress-energy), then this sort of thing fails, because we can't even define unambiguously what it means to add vectors that lie in different tangent spaces.
 
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So I can't integrate a 2-form over a 2-submanifold which is a boundary of a nulla 3-submanifold?
 

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