de Sitter Waves
Tahsin Çağrı Şişman
Abstract: In this talk, we discuss the de Sitter (dS) waves. The dS-wave metrics of a D-dimensional spacetime can be constructed from the curves constrained to live in a (D-1)-dimensional Euclidean space. By construction, these dS-wave metrics are the members of the Kerr-Schild-Kundt (KSK) class of metrics. The KSK metrics are universal in the sense that they solve all the metric based higher-derivative gravity theories once the field equations for the Einsteinian massless spin-2 operator or the massive spin-2 operator are solved for the metric profile function. For the dS wave, we provide the solutions of these equations for the three and four spacetime dimensions. The four-dimensional dS-wave solutions have a potential relevance with the Big Bang era when the higher-derivative modifications of Einstein's gravity may act as an effective theory of gravity at Big Bang energy scales. The Einsteinian dS-wave solution remains as an intact solution for any modification while the massive dS-wave solution requires a theory dependent update of the mass parameter. Lastly, we discuss the geodesic equations which are important to characterize the dS-wave spacetime.