Introduction The study of tree rings is one of the most widely used methods of climate reconstruction for centuries and millennia, but the occurrence of climatic anomalies such as global warming in recent decades has caused divergence problem in the series of tree rings in some areas. Which challenges the ability of this proxy to regenerate the climate. The “divergence problem” is the differen...

Many solutions of General Relativity appear to allow the possibility of time travel. This was initially a fascinating discovery, but geometries of this type violate causality, a basic physical law that is believed to be fundamental. Although string theory is a proposed fundamental theory of quantum gravity, geometries with closed timelike curves have resurfaced as solutions to its low energy eq...

Several recent possible counterexamples to the Chronology Protection Conjecture are critically examined. The “adapted” Rindler vacuum state constructed by Li and Gott for a conformal scalar field in Misner space is extended to nonconformally coupled and self-interacting scalar fields. For these fields, the vacuum stress-energy always diverges on the chronology horizons. The divergence of the va...