Dark matter and dark energy from Bose-Einstein condensate (1411.0753v3)

Abstract: We show that Dark Matter consisting of bosons of mass of about 1eV or less has critical temperature exceeding the temperature of the universe at all times, and hence would have formed a Bose-Einstein condensate at very early epochs. We also show that the wavefunction of this condensate, via the quantum potential it produces, gives rise to a cosmological constant which may account for the correct dark energy content of our universe. We argue that massive gravitons or axions are viable candidates for these constituents. In the far future this condensate is all that remains of our universe.

Dark Matter and Dark Energy from Bose-Einstein Condensate

The paper "Dark matter and dark energy from Bose-Einstein condensate" explores a novel approach to understanding the nature of dark matter (DM) and dark energy (DE) in the universe. The authors propose that a Bose-Einstein condensate (BEC) formed by bosons with masses approximately less than $1 \, \text{eV}$ could account for both DM and DE. This hypothesis provides a unifying perspective on these enigmatic components of our universe, suggesting that the quantum properties of a BEC can give rise to observed cosmological phenomena.

Key Insights and Results

The authors start by setting the theoretical stage, where DM is modeled as a gas of bosons. For bosons with mass $m \leq 1 \, \text{eV}$, the critical temperature for BEC formation exceeds the temperature of the universe at any epoch. This implies that such bosons would have formed a BEC early in the universe's history. A notable calculation is the determination of the critical temperature $T_c = 6 \times 10^{-12} m^{1/3} a \, \text{K}$, reflecting the conditions under which this condensate forms.

Further, the macroscopic wavefunction of the BEC introduces a quantum potential, detectable as a cosmological constant in the Friedmann equation. The authors derive a significant result where, for bosons with mass $m \simeq 10^{-32} \, \text{eV}$, the quantum potential aligns with the observed dark energy content of the universe. This result suggests that bosons of such tiny mass can simultaneously account for both DM and DE.

Viable Candidates and Theoretical Implications

The discussion identifies massive gravitons or axions as potential constituents of these low-mass bosons. While massive gravitons suggest modifications to general relativity, they are supported by theoretical frameworks allowing consistent covariant theories. Axions, initially proposed to resolve the strong CP problem, arise in string theory scenarios as well and are considered viable DM candidates.

The authors use the Gross-Pitaevskii equation to describe the dynamics of the BEC, confirming its consistency with known dynamics of DM, particularly at galaxy scales where it matches observed rotation curves. The paper's findings contribute significantly to ongoing discussions regarding the characteristics and distribution of DM and DE in cosmological models.

Future Directions

The proposed model opens several avenues for further research. Investigating observational predictions of this BEC, such as its heat capacity and effects on cosmic structure formation, could reveal further insights and validate the theoretical claims. Additionally, potential experimental detection of these bosons through gravitational waves or axionic searches could shift our understanding and provide critical empirical support for the BEC paradigm.

In conclusion, this paper offers a compelling quantum-based framework to encapsulate DM and DE as manifestations of a Bose-Einstein condensate. It challenges traditional views, encourages exploration of quantum cosmological models, and invites experimental investigations into the properties and interactions of sub-eV mass bosons in the universe.