Kaluza-Klein Burst: a New Mechanism for Generating Ultrahigh-Energy Cosmic Rays

By invoking small extra dimensions as a good energy bearer, a new scenario for understanding the origin of ultrahigh-energy cosmic rays (UHECRs), from both the bottom-up and the top-down viewpoints, is proposed. We explore the possibility of generating UHECRs via Kaluza-Klein (KK) bursts, a violent energy transfer from extra dimensions to ordinary dimensions through collisions between KK modes, in particular, within clumps of KK modes. The possible scales of these clumps range from the astronomical, e.g. KK stellar compact objects, to the microscopic, e.g. "KKonium". Advantages of this KK burst model of UHECRs and possible signatures of clumped KK modes are discussed.