Spontaneous Collapse Scenario Empirically Viable, Resolves Eternal Inflation and CMB Power Anomaly

The persistent challenge of eternal inflation, a prediction of many inflationary models describing the very early universe, receives fresh scrutiny in new work led by María Pía Piccirilli and Gabriel León of the Grupo de Cosmología, Universidad Nacional de La Plata, alongside Rosa-Laura Lechuga-Solis from the Università di Padova and Daniel Sudarsky of the Universidad de Barcelona. These researchers investigate an alternative inflationary scenario where primordial structures originate from a universe collapse, offering a potential resolution to the issues arising from eternally inflating models. Their approach predicts a unique pattern in the spectrum of primordial fluctuations, characterised by a suppression of power at large scales, and importantly, provides a mechanism to simultaneously explain the origin of cosmic structure and avoid the problematic implications of eternal inflation. By applying the latest observational data from the Planck collaboration, the team establishes constraints on their model’s parameters and demonstrates that the data supports this collapse-driven scenario, offering a compelling alternative to conventional inflationary cosmology.

Cosmic Structure From Quantum Wavefunction Collapse

Scientists are exploring the connection between cosmology and quantum mechanics, specifically a theory called Continuous Spontaneous Localization (CSL). This work investigates how CSL, which proposes a mechanism for wave function collapse, might explain the formation of cosmic structure and address anomalies observed in the cosmic microwave background (CMB) data. The CSL model suggests that wave function collapse isn’t random, but triggered by interactions with the environment, providing a potential pathway for quantum fluctuations during the universe’s rapid expansion to become the seeds of galaxies and large-scale structures. Researchers are focusing on anomalies within the CMB, the afterglow of the Big Bang, including a lack of large-angle correlations, the Cold Spot, and an unexpected alignment of the largest fluctuations.

Scientists hypothesize that the CSL model might explain these anomalies by modifying the primordial power spectrum, the distribution of density fluctuations in the early universe. This work also connects to the quantum measurement problem, the difficulty of reconciling quantum mechanics with our everyday classical experience. The team proposes that CSL provides a physically motivated mechanism for generating primordial density fluctuations during inflation, potentially resolving theoretical issues with standard inflation models. By analyzing CMB data, scientists can search for evidence of modifications to the primordial power spectrum predicted by CSL, offering a potential observational test of the theory.

Semi-Classical Gravity Resolves Early Universe Fluctuations

Scientists revisited an inflationary model where initial fluctuations arise from a collapse mechanism, building upon theories describing semiclassical gravity. This work addresses a challenge in early-universe cosmology: accurately treating metric perturbations, often relying on quantum field theory and interpreting quantum uncertainties as classical fluctuations. Researchers challenged this approach, noting that standard quantum theory requires a clear causal structure when separating the metric, a structure difficult to define for quantum states. To overcome these challenges, the study pioneered a semiclassical gravity framework, treating matter fields quantum mechanically while describing gravity classically, but with crucial modifications to incorporate spontaneous collapses of quantum states.

This modification addresses conflicts with empirical evidence and avoids violating a key requirement for a consistent theory. The team conceptualized these semiclassical gravity versions as effective theories, providing accurate macroscopic descriptions even without a more fundamental underlying theory. The research employed a method combining collapse models with the study of quantum variables related to gravitational and matter degrees of freedom. Scientists investigated how this method could account for the emergence of cosmic structure and suppress long-wavelength modes, thereby avoiding the issue of eternal inflation. The study established observational constraints on model parameters using data from the Planck collaboration, revealing a characteristic suppression in the cosmic microwave background spectrum and supporting the proposed solution for both cosmic structure formation and the avoidance of eternal inflation.

Collapse Model Suppresses Low-Frequency Cosmic Modes

Scientists revisited an inflationary model where primordial density fluctuations arise from a spontaneous collapse mechanism. This work addresses a key challenge in cosmology: explaining the origin of cosmic structure while simultaneously avoiding the problematic scenario of eternal inflation. The model predicts a unique scalar spectrum, governed by parameters related to the collapse rate, designed to account for observed cosmic structure and suppress the amplitude of long-wavelength modes. The team employed data from the Planck 2018 collaboration to constrain the model’s parameters. Results demonstrate a characteristic suppression of low-frequency modes in the cosmic microwave background spectrum, aligning with observations and providing support for the proposed solution.

Data analysis successfully constrained one parameter, while not favoring a specific value for another. The research confirms that the model simultaneously addresses the emergence of cosmic structure and avoids the theoretical difficulties associated with eternal inflation. Scientists demonstrate that the model’s predictions are consistent with the latest Planck data, establishing observational constraints on the collapse parameters. The model successfully reproduces the observed suppression of power at large scales in the cosmic microwave background, a feature difficult to explain with standard inflationary models.

Collapse Model Resolves Cosmic Structure, Inflation

This research presents a novel approach to understanding the origin of cosmic structure and resolving the issue of eternal inflation, building upon the framework of spontaneous collapse theories. Scientists developed a model where primordial inhomogeneities arise from a specific collapse mechanism, predicting a unique scalar spectrum governed by parameters related to the collapse rate. Crucially, this model simultaneously addresses the emergence of cosmic structure and avoids the problematic scenario of eternal inflation, offering an alternative to standard inflationary cosmology. The team’s analysis, utilising the latest data from the Planck collaboration, demonstrates a characteristic suppression of low-wavelength modes in the cosmic microwave background spectrum, consistent with the model’s predictions.

This suppression also accounts for the observed lack of power in the low angular power spectra of the cosmic microwave background, providing a potential explanation for a long-standing observational anomaly. The findings support previous work suggesting that certain types of potentials are not ruled out by current observations within this specific theoretical framework, and predict a significant suppression of the amplitude of primordial gravitational waves. Future research directions include a more detailed investigation of the model’s predictions for gravitational waves and a comparison with other cosmological datasets. Nevertheless, this work represents a significant step towards a more complete understanding of the very early universe and the origin of cosmic structure.