[Paper Review] Einstein's cosmological considerations

Daryl Janzen|arXiv (Cornell University)|Feb 13, 2014

Cosmology and Gravitation Theories86 references3 citations

TL;DR

This paper re-examines Einstein's cosmological considerations and their foundational role in shaping relativistic cosmology, arguing that the standard model's reliance on fine-tuned parameters—particularly zero spatial curvature and a positive cosmological constant—rests on unexplained assumptions. It proposes that a non-synchronous, globally defined cosmic time with a positive cosmological constant can naturally reproduce the observed scale-factor evolution without exotic matter or inflation, challenging the standard model's theoretical foundations.

ABSTRACT

The objective of this paper is not simply to present an historical overview of Einstein's cosmological considerations, but to discuss the central role they played in shaping the paradigm of relativistic cosmology. This, we'll show, was a result of both his actions and, perhaps more importantly, his inactions. Accordingly, discussion won't simply be restricted to Einstein's considerations, as we'll analyse relevant contributions to the relativistic expansion paradigm during the approximately twenty years following Slipher's first redshift measurements in 1912. Our aim is to shed some light on why we think some of the things we do, with the idea that a better understanding of the reasoning that fundamentally influenced the common idea of our expanding universe might help to resolve some of the significant problems that modern cosmology now faces; and we eventually use this knowledge to probe the foundations of the standard model. Much of the information we present, including many of the historical details, we expect will be news to modern practitioners.

Motivation & Objective

• To investigate how Einstein's actions and inactions shaped the paradigm of relativistic cosmology, particularly in the context of the expanding universe.
• To analyze the historical development of relativistic cosmology from 1912 onward, focusing on the period following Slipher’s redshift measurements.
• To question why the standard model of cosmology, despite its empirical success, lacks theoretical justification for its fine-tuned parameters like zero spatial curvature and a positive cosmological constant.
• To challenge the assumption that cosmic time must be defined by the average motion of matter, arguing instead for a more fundamental, non-local definition.
• To propose an alternative cosmological framework in which space-time curvature is a kinematical effect rather than a dynamical one, reconciling better with empirical observations.

Proposed method

• Analyzes historical correspondence and publications by Einstein, de Sitter, and contemporaries to trace the evolution of cosmological assumptions.
• Examines the role of the cosmological constant and spatial curvature in Einstein’s 1932 and 1945 works, highlighting his rejection of non-zero lambda and flatness.
• Proposes a solution in which cosmic expansion is driven solely by a positive cosmological constant, with the scale factor evolving identically to the ΛCDM model but without requiring inflation or exotic matter.
• Uses a non-synchronous cosmic time framework in which cosmic hypersurfaces are not orthogonal to fundamental world lines, challenging the standard assumption of global simultaneity.
• Argues that the horizon problem vanishes when world-structure is not derived from local matter densities, but from a global, kinematical curvature effect.
• Contrasts the standard model’s reliance on fine-tuning with a model that naturally reproduces observed expansion without additional assumptions.

Experimental results

Research questions

• RQ1 Why did Einstein reject the cosmological constant and zero spatial curvature as physically unjustified, despite their empirical success?
• RQ2 How did the historical development of relativistic cosmology lead to the current standard model’s reliance on fine-tuned parameters?
• RQ3 Can a cosmological model with a positive cosmological constant and non-synchronous cosmic time reproduce the observed scale-factor evolution without inflation or exotic matter?
• RQ4 Is the assumption that cosmic time is defined by the average motion of matter in the universe logically coherent, or does it beg the question of simultaneity?
• RQ5 Does the observed flatness of the universe represent a fundamental physical principle or an accidental fine-tuning that undermines the theoretical foundation of modern cosmology?

Key findings

• The paper argues that Einstein’s rejection of the cosmological constant and zero spatial curvature as physically unjustified was well-founded, given the expectation of natural dynamical curvature.
• Despite Einstein’s initial skepticism, modern data now indicate that spatial curvature is precisely zero and the cosmological constant is positive—conditions that are theoretically highly improbable and thus require explanation.
• The proposed model with a positive cosmological constant and non-synchronous cosmic time reproduces the same scale-factor evolution as the ΛCDM model, but without requiring inflation or exotic matter.
• The horizon problem disappears in this framework because the world-structure is not derived from local matter densities, but from a global kinematical effect of curvature.
• The argument that cosmic time is caused by the average motion of matter is shown to be circular, as it presupposes a definition of simultaneity that depends on the very time it seeks to define.
• The paper concludes that the standard model’s success is empirical but lacks theoretical justification, and that a re-evaluation of the foundations of relativistic cosmology is necessary to resolve deep conceptual problems.