Bonn 2020 – scientific programme

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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 4: Space, Time and Symmetry III

AGPhil 4.2: Talk

Wednesday, April 1, 2020, 11:30–12:00, H-HS III

Information in black hole complementarity — •Saakshi Dulani — University of Geneva

Lured by Wheeler's adage 'it from bit,' theoretical physicists are increasingly tempted to interpret the foundations of physics as consisting in information (bit), rather than substances such as particles or fields (it). The consequences of this informational turn are many and profound, including at the frontier of contemporary physics where the question arises whether bits of information get lost in black holes. However, there is widespread disagreement about what the relevant notion of information is. Scholars such as Maudlin [2017] and Wallace [2018] have recently argued that the Black Hole Information Paradox was never about information. 'Information loss' is just a catchy phrase to mean non-unitary evolution. I will argue that the Black Hole Information Paradox is indeed about information, a concept which urgently requires clarification. Bekenstein-Hawking entropy was cast in terms of Shannon entropy from its inception. Furthermore, to claim that black hole evaporation either violates or respects unitarity, one must invoke the behavior of von Neumann entropy, another concept which is foundationally ambiguous. As a case study, I will analyze the meaning of information in Susskind's [2008] controversial solution called Black Hole Complementarity (BHC). I will argue that BHC is incoherent because it represents a hodgepodge of contradictory philosophical positions: operationalism, realism, relationalism, and absolutism. Nonetheless, BHC offers insights into what an observer-dependent definition of information looks like.