近日，日本早稻田大学Yamada, Yusuke团队报道了超自然产生超重卡鲁扎-克莱因粒子。这一研究成果于2025年11月17日发表在《高能物理杂志》上。

额外紧致维度中的规范场可以驱动四维非紧致时空的暴胀，这一理论框架被称为超自然暴胀。随时间变化的规范场构型会沿紧致维度方向产生电场，从而通过施温格效应催生在该场作用下带电荷的卡鲁扎-克莱因粒子。

研究组在五维量子电动力学框架下构建了超自然暴胀模型，该框架与引力场及产生暴胀单圈有效势的物质场相耦合。一般而言，可能存在多个带电荷场，他们证明了在此条件下卡鲁扎-克莱因粒子的产生机制。由于卡鲁扎-克莱因动量守恒，所产生的粒子可能根据模型参数的不同，演化为超重暗物质或成为宇宙的主导成分。

此外，研究组发现即使规范场不作为暴胀子而作为旁观场存在，当哈勃摩擦效应减弱时引发的暴胀后场振荡同样能产生超重卡鲁扎-克莱因模态。这表明沿紧致维度的规范势处于低能态时，卡鲁扎-克莱因粒子的产生是一种普适性现象。

附：英文原文

Title: Extra-natural production of superheavy Kaluza-Klein particles

Author: Yamada, Yusuke

Issue&Volume: 2025-11-17

Abstract: Gauge fields in extra compact dimensions can drive inflation in the four-dimensional (4D) non-compact spacetime, a scenario known as extra-natural inflation. A time-dependent gauge field configuration generates the electric field along the compact dimension, enabling the production of Kaluza-Klein (KK) particles charged under the field via the Schwinger effect. We construct the extra-natural inflation model within a five-dimensional (5D) quantum electrodynamics (QED) framework coupled to gravity including matter fields that generate the inflationary one-loop effective potential. In general, multiple charged fields can exist, and we show that KK particle production occurs under these conditions. Since KK momentum is conserved, the produced KK particles may become superheavy dark matter or dominate the universe, depending on the model parameters. Furthermore, we show that even when the gauge field acts not as the inflaton but as a spectator field, its post-inflationary oscillations, initiated when the Hubble friction becomes negligible, can also generate superheavy KK modes. This suggests that KK particle production is a generic outcome when gauge potentials along compact dimensions are light.

DOI: 10.1007/JHEP11(2025)096

Source: https://link.springer.com/article/10.1007/JHEP11(2025)096