Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.arcetri.astro.it/cpr/PdfPresentations/diSeregoAlighieri.pdf Дата изменения: Wed Sep 9 11:33:10 2015 Дата индексирования: Sun Apr 10 04:23:50 2016 Кодировка: Поисковые слова: п п п п п п п п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п р п

CPR workshop, Arcetri, 8 September 2015

Problems in searching for Cosmic Polarization Rotation
Sperello di Serego Alighieri Osservatorio Astrofisico di Arcetri
Internat. J. Mod. Phys. D 24, 1530016 (2015)


Why are searches for CPR important?
Photons carry almost all the information which we have about the Universe outside the Solar System (a few cosmic rays and several elusive neutrinos are the only exceptions). The information carried by a photon consists of: 1. The direction (RA and Dec) 2. The energy or wavelength 3. The position angle (PA) of the polarization ellipse. To make a proper use of this information, it is important to know whether it is changed while the photon travels in vacuum across the Universe towards us. The direction can be changed by a strong gravitational field. The wavelength is changed by the expansion of the Universe. CPR deals with eventual changes in PA, and none has been measured yet. So the polarization PA appears to be the most constant characteristic of photons. Clearly changes in PA would violate symmetry, since they should be either positive (counter clockwise, IAU convention) or negative (clockwise). This suggests that CPR is connected with the violation of fundamental physical principles. Indeed CPR is connected with Lorentz invariance violation, CPT violation, neutrino number asymmetry, and violation of the Einstein Equivalence Principle (EEP). For a review about the physical principles connected with CPR see Ni (2010) Rep. Prog. Phys. 73, 056901. Use the term CPR, not birefringence (rotation, no splitting).


A summary of CPR tests with different methods

di Serego Alighieri: Internat. J. Mod. Phys. D 24, 1530016 (2015)

All results are consistent with a null CPR. All CPR test methods have reached so far an accuracy of the order of 1° and 3 upper limits to any rotation of a few degrees.


A summary of CPR tests with different methods
di Serego Alighieri 2015 (IJMPD 24, 1530016)
CMB ACTPol, Mei et al. 2015 CMB BICEP1, Kaufman et al. 2014 CMB WMAP9, Hinshaw et al. 2013 RG UV, di Serego Alighieri et al. 2010

CMB QUAD, Brown et al. 2009 CMB BOOMERanG, Pagano et al. 2009 RG radio, Carroll 1998

RG UV, Wardle et al. 1997 RG UV, Cimatti et al. 1994

RG radio, Carroll et al. 1990


Problems in testing the CPR with the CMB
1. CMB Polarization PA calibration problem
One problem is the calibration of the polarization PA for the lack of sources with precisely known PA at CMB frequencies. This introduces a systematic error, which is similar (if not bigger) than the statistical measurement error, of the order of 1°. Recently the polarization PA of the Crab Nebula ( Tau) has been measured with an accuracy of 0.2° at 89.2 GHz (Aumont et al. 2010). However most CMB polarization measurements are made at higher frequencies (100 ­ 150 GHz) and the Crab is not visible from the South Pole. In order to overcome this problem, some CMB polarization experiments have used a TB and EB nulling procedure (Keating et al. 2013). However this procedure would also eliminate any CPR angle , so it cannot be used for CPR tests.


A rotation of linear polarization produces a coupling between T, E-mode and B-mode polarization of CMB


Problems in testing the CPR with the CMB
2. CMB Polarization PA convention problem

A second problem is that unfortunately the CMB polarimetrists have adopted the convention that the polarization PA increases clockwise (looking at the source), which is opposite to the standard convention adopted by all other polarimetrists for centuries and enforced by the IAU (PA increses counter-clockwise). This is obvioulsy producing problems when comparing measurements with different methods, like for CPR tests, also because the "CMB convention" has not been well documented in the CMB polarization papers.


Two opposite conventions for the polarization PA
1. IAU convention: looking at the source, the polarization PA increases counter-clockwise. 2. "CMB" convention: looking at the source, the polarization PA increases clockwise.

IAU coordinates North

"CMB" coordinates

East

East

South


A summary of CPR tests with different methods
arXiv:1409.xxxxv1)


A summary of CPR tests with different methods
arXiv:1409.xxxxv2


The IAU convention for the polarization PA
defined by Commission 40 at the IAU General Assembly in Sidney in 1973 and coded in the IAU Transactions, Vol. XVB, p. 166


The origin of the "CMB" convention for the polarization PA

The Astrophysical Journal, 622:759 ­ 771, 2005 April 1
# 2005. The American Astronomical Society. All rights reserved. Printed in U.S.A.

HEALPix: A FRAMEWORK FOR HIGH-RESOLUTION DISCRETIZATION AND FAST ANALYSIS OF DATA DISTRIBUTED ON THE SPHERE
ґ K. M. Gorski,
1, 2

E. Hivon,3 A. J. Banday,4 B. D. Wandelt,5, 6 F. K. Hansen, M. Reinecke,4 and M. Bartelmann8

7

Received 2004 September 21; accepted 2004 December 10

ABSTRACT HEALPix--the Hierarchical Equal Area isoLatitude Pixelization--is a versatile structure for the pixelization of data on the sphere. An associated library of computational algorithms and visualization software supports fast scientific applications executable directly on discretized spherical maps generated from very large volumes of astronomical data. Originally developed to address the data processing and analysis needs of the present generation of cosmic microwave background experiments (e.g., BOOMERANG, WMAP), HEALPix can be expanded to meet many of the profound challenges that will arise in confrontation with the observational output of future missions and experiments, including, e.g., Planck, Herschel, SAFIR, and the Beyond Einstein inflation probe. In this paper we consider the requirements and implementation constraints on a framework that simultaneously enables an efficient discretization with associated hierarchical indexation and fast analysis/synthesis of functions defined on the sphere. We demonstrate how these are explicitly satisfied by HEALPix. Subject headings: cosmic microwave background -- cosmology: observations -- methods: statistical g

1. INTRODUCTION Advanced detectors in modern astronomy generate data at huge rates over many wavelengths. Of particular interest to us

1. global analysis problems: harmonic decomposition, estimation of the power spectrum, and higher order measures of spatial correlations;


But a map making software in the IAU convention exists...

MNRAS 453, 2058­2069 (2015)

doi:10.1093/mnras/stv1689

A new map-making algorithm for CMB polarization experiments
Christopher G. R. Wallis,< A. Bonaldi, Michael L. Brown and Richard A. Battye
Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK Accepted 2015 July 23. Received 2015 July 21; in original form 2015 March 16

Downloaded from http://mnras.oxfordjournals.org/ at INAF Arce

ABSTRACT

With the temperature power spectrum of the cosmic microwave background (CMB) at least four orders of magnitude larger than the B-mode polarization power spectrum, any instrumental imperfections that couple temperature to polarization must be carefully controlled and/or removed. Here we present two new map-making algorithms that can create polarization maps that are clean of temperature-to-polarization leakage systematics due to differential gain and pointing between a detector pair. Where a half-wave plate is used, we show that the spin2 systematic due to differential ellipticity can also be removed using our algorithms. The algorithms require no prior knowledge of the imperfections or temperature sky to remove the temperature leakage. Instead, they calculate the systematic and polarization maps in one step directly from the time-ordered data (TOD). The first algorithm is designed to work with scan strategies that have a good range of crossing angles for each map pixel and the second for scan strategies that have a limited range of crossing angles. The first algorithm can also be used to identify if systematic errors that have a particular spin are present in a TOD. We demonstrate


Summary and outlook
1. All results are consistent with a null CPR. All CPR test methods have reached so far an accuracy of the order of 1° and 3 upper limits to any rotation of a few degrees. 2. They are complementary in many ways. They cover different wavelength ranges and the methods at shorter wavelength have an advantage, if CPR effects grow with photon energy. They also reach different distances, and the CMB method is unbeatable in this respect. However the relative difference in light travel time between z = 3 and z = 1100 is only 16%. 3. Improvements can be expected by better targeted high resolution radio polarization measurements of RGs and quasars, by more accurate UV polarization measurements of RGs with the coming generation of giant optical telescopes, and by future CMB polarimeters such as PLANCK1 and BICEP3. Indeed the Planck satellite is expected to have a very low statistical error ( 0.06) for CPR measurements. Unfortunately, although Planck has completed its observations more than a year ago, its results on CPR have not yet been released. Planck will have to reduce accordingly also the systematic error in the calibration of the polarization angle, which at the moment is of the order of 1 for CMB polarization experiments. The best prospects to achieve this improvement are likely to be more precise measurements of the polarization angle of celestial sources at CMB frequencies with the ATCA and ALMA and a calibration source on a satellite.