Robustness of the Page-Wootters construction across different pictures, states of the universe, and system-clock interactions
In quantum theory, the concept of time rests on shaky ground. One way to address this problem is to remove the usual background time parameter as a primitive entity and explain its emergence via correlations between physical systems. This approach was adopted by Page and Wootters [Phys. Rev. D 27, 2...
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| Format: | Journal article |
| Language: | English |
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American Physical Society
2023
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| _version_ | 1797111322071007232 |
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| author | Rijavec, S |
| author_facet | Rijavec, S |
| author_sort | Rijavec, S |
| collection | OXFORD |
| description | In quantum theory, the concept of time rests on shaky ground. One way to address this problem is to remove the usual background time parameter as a primitive entity and explain its emergence via correlations between physical systems. This approach was adopted by Page and Wootters [Phys. Rev. D 27, 2885 (1983)], who showed how time can emerge in a stationary quantum universe from the correlations between two of its subsystems, one of them acting as a clock for the other. In this work, I study the robustness of the Page-Wootters construction across different pictures, states of the universe, and clock interactions, clarifying the role and the nature of the correlations between the subsystems of the universe. I start by showing how to formulate the Page-Wootters construction in the Heisenberg picture via a unitary change of basis. I consider both pure and mixed states of the universe and extend the analysis to include interactions between the clock and the other subsystem of the universe. The study reveals what kind of correlations are necessary for the construction to work. Interestingly, entanglement is not required as long as there are no interactions with the clock. The study also shows that these interactions can lead to a nonunitary evolution for some mixed states of the universe. In a simple two-level system, this aspect becomes relevant at scales where one would expect strong relativistic effects. At these scales, I also observe an inversion in the system’s direction of time. |
| first_indexed | 2024-03-07T08:07:07Z |
| format | Journal article |
| id | oxford-uuid:c41f6ae3-eb24-4710-9a90-7a910333ecd7 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T08:07:07Z |
| publishDate | 2023 |
| publisher | American Physical Society |
| record_format | dspace |
| spelling | oxford-uuid:c41f6ae3-eb24-4710-9a90-7a910333ecd72023-11-06T09:36:10ZRobustness of the Page-Wootters construction across different pictures, states of the universe, and system-clock interactionsJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:c41f6ae3-eb24-4710-9a90-7a910333ecd7EnglishSymplectic ElementsAmerican Physical Society2023Rijavec, SIn quantum theory, the concept of time rests on shaky ground. One way to address this problem is to remove the usual background time parameter as a primitive entity and explain its emergence via correlations between physical systems. This approach was adopted by Page and Wootters [Phys. Rev. D 27, 2885 (1983)], who showed how time can emerge in a stationary quantum universe from the correlations between two of its subsystems, one of them acting as a clock for the other. In this work, I study the robustness of the Page-Wootters construction across different pictures, states of the universe, and clock interactions, clarifying the role and the nature of the correlations between the subsystems of the universe. I start by showing how to formulate the Page-Wootters construction in the Heisenberg picture via a unitary change of basis. I consider both pure and mixed states of the universe and extend the analysis to include interactions between the clock and the other subsystem of the universe. The study reveals what kind of correlations are necessary for the construction to work. Interestingly, entanglement is not required as long as there are no interactions with the clock. The study also shows that these interactions can lead to a nonunitary evolution for some mixed states of the universe. In a simple two-level system, this aspect becomes relevant at scales where one would expect strong relativistic effects. At these scales, I also observe an inversion in the system’s direction of time. |
| spellingShingle | Rijavec, S Robustness of the Page-Wootters construction across different pictures, states of the universe, and system-clock interactions |
| title | Robustness of the Page-Wootters construction across different pictures, states of the universe, and system-clock interactions |
| title_full | Robustness of the Page-Wootters construction across different pictures, states of the universe, and system-clock interactions |
| title_fullStr | Robustness of the Page-Wootters construction across different pictures, states of the universe, and system-clock interactions |
| title_full_unstemmed | Robustness of the Page-Wootters construction across different pictures, states of the universe, and system-clock interactions |
| title_short | Robustness of the Page-Wootters construction across different pictures, states of the universe, and system-clock interactions |
| title_sort | robustness of the page wootters construction across different pictures states of the universe and system clock interactions |
| work_keys_str_mv | AT rijavecs robustnessofthepagewoottersconstructionacrossdifferentpicturesstatesoftheuniverseandsystemclockinteractions |