OGRePy and Time Travel Paradoxes

          @misc{ scivideos_PIRSA:25020024,
            doi = {10.48660/25020024},
            url = {https://pirsa.org/25020024},
            author = {Shoshany, Barak},
            keywords = {Cosmology},
            language = {en},
            title = {OGRePy and Time Travel Paradoxes},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2025},
            month = {feb},
            note = {PIRSA:25020024 see, \url{https://scivideos.org/index.php/pirsa/25020024}}
          }
          

Abstract

Part I: OGRePy: Object-Oriented General Relativity in Python   I will present a detailed introduction to my new Python package, OGRePy: (O)bject-Oriented (G)eneral (Re)lativity for (Py)thon, a port of my popular Mathematica package OGRe, which is used by many researchers in general relativity and related areas. I will demonstrate the package's usage and features, including its ability to manipulate tensors of arbitrary rank using an intuitive interface, and calculate arbitrary tensor formulas involving any combination of addition, multiplication, trace, contraction, and partial and covariant derivatives - while automatically figuring out the proper index configuration and coordinate system to use for each tensor, eliminating user error.   Part II: Time Travel Paradoxes and Entangled Timelines   If time travel is possible, it seems that it would inevitably lead to paradoxes, indicating an internal inconsistency in our current theories of nature. Can these paradoxes be resolved by new laws of physics, or perhaps even existing ones? I will first review the different types of time travel paradoxes and their proposed resolutions. Then I will present the results of my 3 recent papers (1911.11590, 2110.02448, 2303.07635) discussing different aspects of time travel paradoxes from the perspectives of both general relativity and quantum mechanics. I will argue that generic time travel paradoxes can only be resolved using the concept of parallel timelines, and suggest possibilities for how such timelines may manifest themselves.