2009/06/20 by Cheng-Yi Sun, Sun, Cheng-Yi
Physics and Astronomy · #Astrophysical Phenomena and Observations #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #gr-qc
paper · pdf · doi:10.48550/arxiv.0906.3783
7 pages, 1 figures; typographical errors are corrected; details is added; conclusin is unchanged
openalex publication_date 2009/06/20 · arxiv created 2010/03/17 · arxiv updated 2010/03/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
How to describe a black hole embedded in an expanding universe is an important topic. Some models about this issue are suggested by assuming that the metric is a conformal transformation of the Schwarzschild metric or of the isotropic black hole metric. However, there exists naked singularities in the two metrics. Recently, it is argued that the singularity in the Sultana-Dyer space-time is covered by an apparent horizon surface. But we find that such an apparent horizon does not exist if the null energy condition holds.