In this brief report I introduce a yet another class of geometries for which semi-classical chronology protection theorems are of dubious physical reliability. I consider a “Roman ring” of traversable wormholes, wherein a number of wormholes are arranged in a ring in such a manner that no subset of wormholes is near to chronology violation, though the combined system can be arbitrarily close to...

Many cities in the Global South are structurally different from Northern, particularly American, on which much of urban sociology’s conceptual apparatus has been based. Thus, depicting them terms a standard vocabulary risks imposing an inappropriate way seeing. We need that is able to accommodate their experience. This special issue contributes work building vocabulary. select five keywords soc...

Vesta has a complex cratering history, with ancient terrains as well as recent large impacts that have led to regional resurfacing. Crater counts can help constrain the relative ages of different units on Vesta's surface, but converting those crater counts to absolute ages requires a chronology function. We present a cratering chronology based on the best current models for the dynamical evolut...

This is a brief survey of the current status of Stephen Hawking’s “chronology protection conjecture”. That is: “Why does nature abhor a time machine?” I’ll discuss a few examples of spacetimes containing “time machines” (closed causal curves), the sorts of peculiarities that arise, and the reactions of the physics community. While pointing out other possibilities, this article concentrates on t...

We test the chronology protection conjecture in classical general relativity by investigating finitely vicious space-times. First we present singularity theorems in finitely vicious space-times by imposing some restrictions on the chronology violating sets. In the theorems we can refer to the location of an occurring singularity and do not assume any asymptotic conditions such as the existence ...

We test the chronology protection conjecture in classical general relativity by investigating nitely vicious space-times. First we present singularity theorems in nitely vicious space-times by imposing some restrictions on the chronology violating sets. In the theorems we can refer to the location of an occurring singularity and do not assume any asymptotic conditions such as the existence of n...

We investigate the phenomenon of particle creation of the massless scalar field in the model of spacetime in which, depending on the model’s parameter ao, the chronology horizon could be formed. The model represents a two-dimensional curved spacetime with the topology R × S which is asymptotically flat in the past and in the future. The spacetime is globally hyperbolic and has no causal patholo...

with the publication of one complete edition of the journal expedition in 1989 on hasanlu project by american archaeologists, engaged there during pre-revolutionary period, the present study highlights some of the accepted mistakes in the explanation and interpretation of the facts in the articles of that journal on one hand, and the beginning of the activities by iranian archaeologists in 2000...