Profile
Christopher J. Fewster
Professor of mathematics, University of York
Fewster studies quantum field theory in curved spacetime and quantum energy inequalities. His worldline result bounds sampled scalar-field energy under specified spacetime and state assumptions. With Thomas Roman, he showed that analogous null-geodesic averages need not have lower bounds in four-dimensional flat spacetime, distinguishing them from timelike averages.
Affiliations
- University of York, Department of Mathematics
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Bibliography
A bibliography listing does not establish authorship. Credits appear under attribution.
Published bibliography entries: 2. Showing 1–2 of 2.
Listed work
Paper · 2000
A general worldline quantum inequality
- Christopher J Fewster(Author)
Christopher Fewster works on worldline quantum inequalities, lower bounds on the averaged energy density of a quantum field along an observer's worldline. They matter because a quantum field's energy density at a single point has no lower bound. For a linear scalar field in any globally hyperbolic spacetime, he proves an inequality on the normal ordered energy density for any smooth timelike trajectory, any smooth compactly supported weight and any Hadamard state. This generalises an earlier result for static trajectories in static spacetimes. The argument is made rigorous with microlocal analysis and the microlocal spectral condition for Hadamard states, with a compact form given for stationary trajectories.
Listed work
Paper · 2003
Null energy conditions in quantum field theory
- Christopher J. Fewster(Author)
- Thomas A. Roman(Author)
Christopher Fewster and Thomas Roman show, by explicit construction for the massless scalar field in four-dimensional flat spacetime, that weighted null averages of the stress-energy tensor have no lower bound over Hadamard states. So no quantum inequality holds along null geodesics in four dimensions, unlike two-dimensional flat spacetime where one does. The difference arises because in two dimensions any two field modes move either parallel or antiparallel, while the four-dimensional proof uses modes almost parallel to the geodesic. These states still satisfy the averaged null energy condition. In any globally hyperbolic spacetime, null-contracted stress-energy averaged along a timelike worldline does obey a quantum inequality, for massive and massless fields alike.