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Reference.org
Fermat's and energy variation principles in field theory
open-in-new
<p>In <a href="/facts/General_relativity/jVsoIg8X">general relativity</a>, light is assumed to propagate in a <a href="/facts/Vacuum/BTk3goyV">vacuum</a> along a <a href="/facts/Null_geodesic/PEBX8FSm">null geodesic</a> in a <a href="/facts/Pseudo-Riemannian_manifold/VFXsVjqb">pseudo-Riemannian manifold</a>. Besides the geodesics principle in a <a href="/facts/Classical_field_theory/7HuKY1qu">classical field theory</a> there exists <a href="/facts/Fermat%2527s_principle/UL9XumdW">Fermat's principle</a> for <a href="/facts/Stationary_spacetime/CXLvlTQ4">stationary gravity fields</a>. </p>