The cosmological constant is a number that describes the energy causing the universe to expand faster. According to quantum field theory, empty space should have huge energy from quantum fluctuationsfluctuations/ˌflʌktʃuˈeɪʃənz/L2波动；起伏变化small and frequent changes in something, such as level, amount, or value. This would make the constant extremely large. However, observations show the constant is very small. This mismatchmismatch/ˈmɪsmætʃ/L2不匹配；不一致a situation where two things are not suitable for each other or do not correspond is a major problem in physics.
Now, researchers at Brown University have found a possible answer. They discovered a link between quantum gravity and the quantum Hall effect. This effect is a special state of matter, and its electrical values stay stable due to topologytopology/təˈpɒlədʒi/L2拓扑学；拓扑结构the study of how shapes and spaces are connected or arranged, especially in mathematics and physics. The researchers argue that space-timespace-time/ˈspeɪs ˈtaɪm/L2时空the four-dimensional continuum that combines the three dimensions of space with the dimension of time itself may have a similar topology, and this topology protects the cosmological constant from large quantum effects. "All the quantum perturbations that should blow up the value of the cosmological constant are rendered inert by this topology," said physicist Stephon Alexander.
The study was published in Physical Review Letters. It offers a new direction for solving the cosmological constant problem. However, more work is needed to fully confirmconfirm/kənˈfɜːm/L2确认；证实to prove that something is true or correct this idea.
