A new simple and general explanation of the effect of acceleration of particles by black holes to infinite energies in the centre of mass frame is suggested. It is based on kinematics of particles moving near the horizon. This effect arises when particles of two kinds collide near the horizon. For massive particles, the first kind represents a particle with the generic energy and angular momentum (I call them "usual"). Near the horizon, such a particle has a velocity almost equal to that of light in the frame that corotates with a black hole (the frame is static if a black hole is static). The second kind (called "critical") consists of particles with the velocity v<c near the horizon due to special relationship between the energy and angular momentum (or charge). As a result, the relative velocity approaches the speed of light c, the Lorentz factor grows unbound. This explanation applies both to generic rotating black holes and charged ones (even for radial motion of particles). If one of colliding particles is massless (photon), the critical particle is distinguished by the fact that its frequency is finite near the horizon. The existence (or absence) of the effect is determined depending on competition of two factors - gravitational blue shift for a photon propagating towards a black hole and the Doppler effect due to transformation from the locally nonrotating frame to a comoving one. Classification of all possible types of collisions is suggested depending on whether massive or massless particle is critical or usual.
Invariant length scale in relativistic kinematics - Lessons from Dirichlet branes
我们证明了Dirac Born Infeld理论具有一个隐藏的不变性，它将Dirichlet p-膜上的局部O（1，p）Lorentz对称性增强为O（1，p）x O（1，p）规范群，编码了不变的速度和加速度（或长度）标度。这个扩大的规范群预言了狄利克雷膜上观测者的运动学结果，允许的加速度从上面有界。弦论之外的一个重要教训是，一个基本的长度尺度可以应用到广义相对论的运动学中，同时保持时空作为光滑流形和局部洛仑兹对称性，这与通常的看法相反。我们指出弦现象学，经典引力和原子物理学的后果。
On the compatibility of a proposed explanation of the Pioneer anomaly with the cartography of the solar system
我们在这里分析的原因，为什么由作者提出的先驱异常的解释是完全兼容的太阳系的制图。首先，这个提议假定，这种现象是一种明显的加速，而不是一种真正的加速，是由天文时间和原子钟时间在前一瞬间同步后逐渐去同步化引起的。这种去量子化可能是由背景引力和量子真空之间的耦合引起的。因此，先锋加速度和行星轨道半径值不相容的标准论点不能应用。第二，这个建议给出了与标准物理学完全相同的雷达测距观测结果。因此，它不会与美国宇航局维京号任务所确定的太阳系非常精确的地图相冲突。换句话说，虽然这个建议预测了宇宙飞船速度和多普勒观测频率的明显变化，但正如实际观察到的那样，它不会以任何方式影响距离的值。注意，天文钟和原子钟之间的加速度时间（{ \it i. e.}一个渐进的去量子化）不能被先验地抛弃，只要我们将缺乏量子引力的理论。
Flows and particles with centrifugal (centripetal) and Coriolis' velocities and accelerations. Hubble's law in spaces with affine connections and metrics
