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dc.contributor.authorLewis, Aen
dc.contributor.authorHall, Aen
dc.contributor.authorChallinor, Anthonyen
dc.date.accessioned2017-09-22T12:09:26Z
dc.date.available2017-09-22T12:09:26Z
dc.identifier.issn1475-7516
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/267339
dc.description.abstractLensing of the CMB is an important effect, and is usually modelled by remapping the unlensed CMB fields by a lensing deflection. However the lensing deflections also change the photon path so that the emission angle is no longer orthogonal to the background last-scattering surface. We give the first calculation of the emission-angle corrections to the standard lensing approximation from dipole (Doppler) sources for temperature and quadrupole sources for temperature and polarization. We show that while the corrections are negligible for the temperature and E-mode polarization, additional large-scale B-modes are produced with a white spectrum that dominates those from post-Born field rotation (curl lensing). On large scales about one percent of the total lensing-induced B-mode amplitude is expected to be due to this effect. However, the photon emission angle does remain orthogonal to the perturbed last-scattering surface due to time delay, and half of the large-scale emission-angle B modes cancel with B modes from time delay to give a total contribution of about half a percent. While not important for planned observations, the signal could ultimately limit the ability of delensing to reveal low amplitudes of primordial gravitational waves. We also derive the rotation of polarization due to multiple deflections between emission and observation. The rotation angle is of quadratic order in the deflection angle, and hence negligibly small: polarization typically rotates by less than an arcsecond, orders of magnitude less than a small-scale image rotates due to post-Born field rotation (which is quadratic in the shear). The field-rotation B modes dominate the other effects on small scales.
dc.description.sponsorshipAL acknowledges support from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement No. [616170], and AL and AC from the Science and Technology Facilities Council [grant numbers ST/L000652/1 and ST/N000927/1, respectively]. AH is supported by a United Kingdom Space Agency Euclid grant, and an STFC Consolidated Grant.
dc.publisherIOP Publishing
dc.subjectCMBR theoryen
dc.subjectgravitational lensingen
dc.subjectCMBR polarisationen
dc.subjectgravitational wavesen
dc.subjectCMBR polarizationen
dc.titleEmission-angle and polarization-rotation effects in the lensed CMBen
dc.typeArticle
prism.publicationNameJournal of Cosmology and Astroparticle Physicsen
dc.identifier.doi10.17863/CAM.13329
dcterms.dateAccepted2017-07-24en
rioxxterms.versionofrecord10.1088/1475-7516/2017/08/023en
rioxxterms.versionAM*
rioxxterms.licenseref.urihttp://www.rioxx.net/licenses/all-rights-reserveden
rioxxterms.licenseref.startdate2017-07-24en
dc.contributor.orcidChallinor, Anthony [0000-0003-3479-7823]
dc.identifier.eissn1475-7516
dc.publisher.urlhttp://dx.doi.org/10.1088/1475-7516/2017/08/023en
rioxxterms.typeJournal Article/Reviewen
pubs.funder-project-idSCIENCE & TECHNOLOGY FACILITIES COUNCIL (ST/N000927/1)
cam.issuedOnline2017-08-18en
rioxxterms.freetoread.startdate2018-08-18


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