Comment on ``Can Black Holes be Torn Up by a Phantom in Cyclic Cosmology?" by X. Zhang. arXiv:0708.1408 [gr-qc]

TL;DR

This paper critiques Zhang's claims that black holes expand and causal patches reconnect before the cyclic universe's turnaround, clarifying that these conclusions are based on incorrect variable choices.

Contribution

The paper corrects Zhang's analysis by demonstrating that his conclusions about black hole behavior and causal patch reconnection are erroneous due to variable selection issues.

Findings

Zhang's claims are based on incorrect variable choices.

Black holes do not begin to expand before the turnaround.

Causal patches do not reconnect as Zhang suggested.

Abstract

In a recently archived paper by Zhang\cite{Zhang}, it is claimed that before turnaround in a cyclic model two unexpected events happen: (1) black holes cease to contract and begin to expand; (2) separated causal patches start to reconnect. We show that both conclusions are erroneous and result from the author's choice of variables.