2011/03/10 by Valerio Faraoni, Alex B. Nielsen
Physics and Astronomy · #Apparent horizon #Black Holes and Theoretical Physics #Classical mechanics #Conformal map #Conformal symmetry #Cosmology #Cosmology and Gravitation Theories #Entropy (arrow of time) #Event horizon #Friedmann–Lemaître–Robertson–Walker metric #Galaxies: Formation, Evolution, Phenomena #General relativity #Geometry #Horizon #Killing vector field #Mathematical physics #Minkowski space #Physics #Quantum mechanics #Scalar field #Spacetime #Theoretical physics #gr-qc
paper · pdf · doi:10.1088/0264-9381/28/17/175008
23 pages
arxiv created 2011/03/10 · openalex publication_date 2011/07/29 · arxiv updated 2015/05/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We explicitly prove the horizon-entropy increase law for both causal and quasi-locally defined horizons in scalar–tensor and f ( R ) gravity theories. Contrary to causal event horizons, future outer trapping horizons are not conformally invariant and we provide a modification of trapping horizons to complete the proof, using the idea of generalized entropy. This modification means that they are no longer foliated by marginally outer trapped surfaces but fixes the location of the horizon under a conformal transformation. We also discuss the behaviour of horizons in 'veiled' general relativity and show, using this new definition, how to locate cosmological horizons in flat Minkowski space with varying units, which is physically identified with a spatially flat FLRW spacetime.