Mathematics Atlas

How Proof Is Made
Sign In
Text size
100%
Theme
Theorem

Kramers-Kronig Relations

Mathematical Physics

The Kramers-Kronig Relations connect the real and imaginary parts of any complex-valued function that is analytic in the upper half of the complex plane, expressing each part as a specific integral transform, a Hilbert transform, of the other. Named for Hendrik Kramers and Ralph Kronig, they apply to any physical response function that respects causality, such as a material's frequency-dependent optical or electrical response, and let one part of the response be recovered entirely from a full knowledge of the other.

Facts
Statement
The real and imaginary parts of a complex function analytic in the upper half-plane are related by Hilbert transforms of each other. 1
Classification
Statement Form
Identity or Equation 1
Connections

Has Statement Form

Equation, Concepts

Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.

Identity, Concepts

Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.

Sources
1. Kramers-Kronig relations (Wikipedia)
Formulation
Quote, Formulation
the real and imaginary parts of any complex function that is analytic in the upper half-plane
View the Source
Comments (0)
No comments yet. Be the first to share a thought.
Reader Challenges (0)
No disputes yet. Spotted an error or a better source? Open the first one.