Dear all,
Iain Brown - Wednesday 29th February - 4.30pm Maths Room 103
This week the Relativity and Cosmology seminar will be given by Iain
Brown from the University of Oslo on the topic of "Gauge Issues and
Flexible Codes in Modified Gravity". The abstract of the talk is below
this email. The seminar will begin at the usual time of 4.30pm in the
Maths Seminar Room 103.
For further information on the seminar series and the location of the
Maths building please see our wiki at http://cosrel.maths.qmul.ac.uk .
Best wishes,
Ian
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Dr Ian Huston
Postdoctoral Researcher
Cosmology and Relativity Group
Astronomy Unit, School of Physics and Astronomy
Queen Mary, University of London
[log in to unmask]
http://www.maths.qmul.ac.uk/~ith
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Gauge Issues and Flexible Codes in Modified Gravity
Iain Brown
Differentiating between theories of modified gravity and exotic matter
is impossible at the background level since models can be tuned to any
expansion history, and we must consider the nature of perturbations on
the background. Doing so is easier in the so-called "Einstein frame"
where the modified gravity is written as standard general relativity
non-minimally coupled to a scalar field. Illustrating our arguments
with f(R) gravity, we show that transforming into the Einstein frame
tangles the choice of gauge and that, if this is not properly
considered, the results of calculations in the Einstein frame could be
seriously compromised. We then outline the modifications to Boltzmann
codes necessary to calculate CMB anisotropies and the matter power
spectrum for arbitrary modified gravity models possessing an Einstein
frame.
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