CSU completes the first deterministic experimental test of dark energy theory
A joint research group formed by Academician Du Jiangfeng from the Key Laboratory of Microscopic Magnetic Resonance, Chinese Academy of Sciences, University of Science and Technology of China and Nanjing University has made significant progress in the field of dark energy detection. The fifth force predicted by the theory was not found, thus ruling it out as a possible dark energy source. This is the first definitive experimental test of any dark energy theory. The research results were published online on August 25 in the international academic journal "Nature" under the title "Experiments with levitated force sensor challenge theories of dark energy. Physics.
Among the 125 most challenging scientific questions published in Science, "What is the universe made of" is the first one. Observations in cosmology and astronomy suggest that our universe is expanding at an accelerated rate and that dark energy is thought to be driving the expansion. However, it is still unknown what the nature of dark energy is and in what way it interacts with our world. To explore the mysterious dark energy field, various experimental research programs have been laid out internationally. The traditional means are mainly with the help of astronomical observations or large physical devices, such as space telescopes, underground laboratories, and large high-energy particle gas pedals. In recent years, CAS Key Laboratory of Microscopic Magnetic Resonance has developed innovative experimental systems and techniques based on solid-state spins, gaseous atoms, and micromechanical systems that can be explored at the Lab scale, providing a new way to expand human understanding of the universe, and has completed a series of important experimental studies [Nat. Commun. 9, 739 (2018); PRL 121, 080402 (2018); PRL 127, 010501 (2021); Nat. Phys. 17, 1402 (2021); Sci. Adv. 7, eabi9535 (2021); PRL 129, 051801 (2022)].
This study is an experimental test of an important dark energy theory, the chameleon theory. One of the most important features of the chameleon theory, a theoretical model used to explain the accelerated expansion of the universe, is the prediction of a "fifth force" in addition to the four known fundamental interactions, which can be written in the form of a small deviation from the action of gravity, which offers the possibility of experimental studies.
In this work, the researchers used an antimagnetic levitation mechanics system as a force detector, and constructed a sub-millimeter-scale "desktop" force detection platform with ultra-high sensitivity to detect the fifth force predicted by the chameleon theory. In the study, the chameleon field was simulated numerically and geometrically designed based on first principles, and a thin-film structure was adopted for the mass source and force detector, which effectively solved the difficulty of double shielding of the chameleon field at the mass source and force detector ends (Figure 1, left); moreover, the fifth force drive with ultra-long coherence time was generated to improve the force detection accuracy. The above techniques greatly enhance the detection efficiency of the fifth force and achieve the highest international detection accuracy for chameleon theory to date (Figure 1, right), limiting the upper limit of the theoretically predicted chameleon force to 6 x 10-17 Nm. Combined with other previous experiments, this study has finally completed a full-parameter spatial test of the fundamental chameleon theory, and no "fifth force" predicted by the theory has been found, thus definitively ruling out this dark energy theory (see Figure 2).
Figure 1:Experimental system of anti-magnetic levitation mechanics system (left); upper limit of the fifth force of chameleon given by experimental probing (right)
Figure 2:Dark energy detection results of this study: coupling limits of the fundamental chameleon field to ordinary matter (left), coupling limits of different orders of chameleon field to ordinary matter (center), and coupling limits of the fundamental chameleon field to photons (right). The colored regions are those that were experimentally examined and excluded, and the region examined in the current work is red, which, together with the previously reported experiments, completely excludes the chameleon model.
The antimagnetic levitation mechanics system used in the study is an ultra-sensitive mechanical sensor developed in recent years, and the CAS Key Laboratory of Microscopic Magnetic Resonance at CSU was one of the first laboratories internationally to conduct research on this cutting-edge technology. The laboratory laid out the experimental research direction of precision measurement of weak force signals ten years ago, and academician Jiangfeng Du led his graduate students Pu Huang and Peiran Yin (now professor and postdoctoral fellow at Nanjing University, co-corresponding author and co-first author of this paper, respectively) to build an experimental platform from scratch and successfully developed a series of experimental techniques for precision measurement of force signals with high precision [PRL 110, 227202 (2013) ); PRL 117, 017701 (2016); Nat. Commun. 7, 11517 (2016)], including the pioneering development of precision measurement techniques based on antimagnetic levitation mechanical systems [Physical Review Applied 12, 044017 (2019)]. The aforementioned work laid the core experimental foundation for the research work in this paper.
The reviewer highly praised the work: "In my opinion this is a very important result ......this represents a significant step forward in this In my opinion this is a very important result ......this represents a significant step forward in this field". This work fully demonstrates the cross-fertilization of precision force detection and cosmological research, which is expected to stimulate a wide range of interests in several basic science fields such as cosmic astronomy, particle physics and atomic-molecular physics.
Rui Li, a PhD student at the Key Laboratory of Microscopic Magnetic Resonance, CAS, together with Peiran Yin, a postdoctoral student at Nanjing University, and Chengjiang Yin, a master's student, are the co-first authors of the paper, and Jiangfeng Du, an academician, together with Prof. Pu Huang and Associate Prof. Jianhua He at Nanjing University are the co-corresponding authors. This research was supported by grants from CAS, MOST, NSFC, Anhui Province and Hefei City.
Link to the paper：
https://www.nature.com/articles/s41567-022-01706-9
