- #1
Frank Castle
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I've read that if a given spacetime possesses a timelike Killing vector, then it is possible to define a unique vacuum state by constructing positive and negative frequency modes with respect to this timelike Killing vector.
My question is, what does this mean? Explicitly, how does one use a timelike Killing vector to construct positive and negative frequency modes?
Is it something to do with the fact that if the spacetime possesses a timelike Killing vector, then one can find a coordinate frame in which the metric is time-independent, with the time coordinate defined with respect to the Killing vector ##\frac{\partial}{\partial t}##. The equation of motion of a given quantum field (say a scalar for simplicity) is then separable (in this coordinate system) into a temporal and a spatial differential equation. One can then define positive and negative frequency modes as solutions to the temporal differential equation? If there is no timelike Killing vector then the equation of motion will not be separable and hence the solutions cannot be separated into a temporal and a spatial component, thus preventing one from classifying modes as positive 0r negative frequency?
My question is, what does this mean? Explicitly, how does one use a timelike Killing vector to construct positive and negative frequency modes?
Is it something to do with the fact that if the spacetime possesses a timelike Killing vector, then one can find a coordinate frame in which the metric is time-independent, with the time coordinate defined with respect to the Killing vector ##\frac{\partial}{\partial t}##. The equation of motion of a given quantum field (say a scalar for simplicity) is then separable (in this coordinate system) into a temporal and a spatial differential equation. One can then define positive and negative frequency modes as solutions to the temporal differential equation? If there is no timelike Killing vector then the equation of motion will not be separable and hence the solutions cannot be separated into a temporal and a spatial component, thus preventing one from classifying modes as positive 0r negative frequency?
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