Interpretations of Cosmological Spectral Shifts

TL;DR

This paper examines how cosmological spectral shifts can be interpreted in different Robertson-Walker models, highlighting the role of space-time curvature and clarifying misconceptions in existing literature.

Contribution

It demonstrates that spectral shifts in flat or closed models are due to space-time curvature, and clarifies the conditions under which shifts can be split into kinematic and gravitational parts.

Findings

Spectral shifts in flat or closed models are linked to space-time curvature.

In hyperbolic models, shifts can be uniquely split into kinematic and gravitational parts for small distances.

The paper corrects common misconceptions about the interpretation of spectral shifts.

Abstract

It is shown that for Robertson-Walker models with flat or closed space sections, all of the cosmological spectral shift can be attributed to the non-flat connection (and thus indirectly to space-time curvature). For Robertson-Walker models with hyperbolic space sections, it is shown that cosmological spectral shifts uniquely split up into "kinematic" and "gravitational" parts provided that distances are small. For large distances no such unique split-up exists in general. A number of common, but incorrect assertions in the literature regarding interpretations of cosmological spectral shifts, is pointed out.