Approximation by smooth forms

Definition

Approximation by smooth forms refers to the process of representing a given current or geometric object using smooth differential forms, which are infinitely differentiable functions. This concept is crucial in geometric measure theory as it allows for the analysis of more complex geometric objects through simpler, well-understood smooth forms. The ability to approximate currents using smooth forms facilitates operations like slicing and projection, and aids in the characterization of rectifiable currents, ultimately contributing to results like the closure theorem.

5 Must Know Facts For Your Next Test

1. The approximation by smooth forms is fundamental for establishing regularity results for currents and rectifiable sets.
2. Smooth forms can be used to approximate singularities in currents, making complex geometries more manageable.
3. The density of smooth forms within the space of distributions enables powerful tools in analysis and topology.
4. In the context of rectifiable currents, approximation by smooth forms helps demonstrate that every rectifiable current can be approached by smooth currents.
5. The closure theorem asserts that the closure of a space of currents contains all limits of sequences of currents approximated by smooth forms.

Review Questions

• How does approximation by smooth forms enhance our understanding of currents and their properties?
  • Approximation by smooth forms allows us to represent complex currents through simpler, infinitely differentiable functions. This simplification makes it easier to study properties such as regularity, integration, and behavior under operations like slicing. By approximating singularities and utilizing smooth forms, we gain valuable insights into the structure and characteristics of the original currents.
• Discuss the significance of approximation by smooth forms in proving the closure theorem related to rectifiable currents.
  • The closure theorem states that any limit point of a sequence of rectifiable currents is also a rectifiable current. Approximation by smooth forms plays a critical role in this proof by demonstrating that rectifiable currents can be approached closely using sequences of smooth currents. This connection ensures that any convergence behavior respects the structure imposed by rectifiable conditions, affirming the integrity of the space of currents.
• Evaluate how the concept of approximation by smooth forms interacts with both slicing and projection operations in geometric measure theory.
  • Approximation by smooth forms directly influences both slicing and projection operations, providing a pathway for analyzing how these operations affect the structure of currents. By approximating a current with smooth forms before performing these operations, we can maintain control over the geometric properties involved. This interplay allows us to dissect and understand more complex geometric relationships while ensuring that our results remain valid in the context of both local and global behaviors within the space of currents.

Related terms

Currents:

Generalized surfaces or objects in geometric measure theory that can be thought of as linear functionals acting on differential forms.

Rectifiable Currents:

Currents that can be represented as a finite sum of smooth forms, allowing for the effective analysis of their properties.

Slicing:

The operation of intersecting a current with a hyperplane to obtain a lower-dimensional current, which is essential for understanding the structure of the original current.