Could quantum information theory explain universe evolution?

The gravity from entropy (GfE) theory has been utilized by Ginestra Bianconi, a researcher at Queen Mary University of London, to elucidate how low-entropy structures such as galaxies form and persist within a universe characterized by increasing entropy over time. According to Bianconi's findings, entropy density can locally decrease while the overall entropy of the universe still increases.

The second law of thermodynamics, a fundamental principle in physics, dictates that entropy must increase with time, serving as the sole law to dictate the direction of time we perceive. Entropy itself quantifies disorder, with lower entropy signifying greater structure and higher entropy indicating a more disordered system. The observed increase in entropy underlies phenomena such as diffusion, gas expansion, and cooling of coffee.

Cosmologists believe that the universe's evolution also adheres to the second law, starting from a low-entropy state and progressing to high-entropy states. The emergence of intricate structures, like galaxies, seemingly contravenes this law, posing a longstanding conundrum in cosmology. Bianconi's GfE theory addresses this paradox by treating space-time metrics as quantum operators, encoding spatial curvature.

By quantizing space-time geometry, the theory yields two distinct metrics: a 'true' metric and an induced metric from mass and energy. The contrast between these metrics, quantified by quantum relative entropy (QRE), governs the dynamics of space-time.

In scenarios of low curvature, classical general relativity is accurately reproduced by Bianconi's equations. However, when deviations from low curvature occur, the equations need modification via a mathematical entity known as the 'G-field', which introduces a dynamic dark-energy term. This term, unlike the static cosmological constant in standard general relativity, could potentially be experimentally verified.

Bianconi demonstrates that the GfE theory can be effectively applied to a Friedmann–Robertson–Walker (FRW) metric universe, which serves as a simplified model of the universe's behavior, characterized by isotropy, homogeneity, and expansion—properties driven by the universe's dominant components such as dark matter, matter, or radiation.

As the universe expands, its volume and total entropy increase, leading to a decrease in local entropy density. This decrease in local entropy offers a pathway for creating low-entropy structures like galaxies and even life forms in an expanding universe. To address whether this mechanism contravenes the second law of thermodynamics, Bianconi concludes that, within a non-empty FRW metric universe, the local decrease in entropy density is offset by an increase in total entropy due to the universe's expansion.

The GfE theory, while still in its early stages, underscores its intrinsic thermodynamic nature and presents new possibilities for both classical and quantum gravity research. By integrating quantum information and entropy into gravity's framework, the theory may pave a novel path towards quantizing gravity, an enduring challenge in fundamental physics. Bianconi's work was published in Physical Review D.