Hi all,
This week we will have talks by two visitors, Tamara Kohler from UCL and
Esteban Castro Ruiz from Vienna. Also, due to a scheduling conflict, we
will have to start late, at 16:45, and in a different room, H42. I hope
this is not an inconvenience.
So far I have an abstract from Esteban Castro Ruiz, which you can find
below. I will send more information on Tamara Kohler's talk when it becomes
available.
Best,
-joe
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Title: Time reference frames and gravitating quantum clocks
Abstract: The standard formulation of quantum theory relies on the
assumption of a fixed background notion of time, according to which events
are localised and the order between them is well defined. In general
relativity, physics is independent of any such background notion
--spacetime points have no direct physical meaning. For this reason, the
localisation of events in time is defined operationally, via the
measurement of physical clocks. When the clocks are classical, the order
between events is still well-defined. Here, we explore the problem of
defining the localisation of events with respect to gravitating quantum
clocks. I will present a quantum framework for “time reference frames,”
describing quantum states, dynamics and measurements with respect to
different quantum
clocks, which might interact, gravitationally or otherwise, with
other quantum systems. We will see that, with respect to interacting
quantum clocks, the time localisability of events, as well as their
order, becomes a relative concept, depending on the time reference frame.
We discuss the consequences of this finding for the physical realisation
of indefinite causal structures at the interplay between quantum
physics and gravity.