Multiple lensing of the cosmic microwave background anisotropies
Abstract
We study the gravitational lensing effect on the Cosmic Microwave Background (CMB) anisotropies performing a raytracing of the primordial CMB photons through intervening largescale structures (LSS) distribution predicted by NBody numerical simulations with a particular focus on the precise recovery of the lensinduced polarized counterpart of the source plane. We apply both a multiple plane raytracing and an effective deflection approach based on the Born approximation to deflect the CMB photons trajectories through the simulated lightcone. We discuss the results obtained with both these methods together with the impact of LSS nonlinear evolution on the CMB temperature and polarization power spectra. We compare our results with semianalytical approximations implemented in Boltzmann codes like, e.g., CAMB. We show that, with our current Nbody setup, the predicted lensing power is recovered with good accuracy in a wide range of multipoles while excess power with respect to semianalytic prescriptions is observed in the lensing potential on scales ℓ ∼> 3000. We quantify the impact of the numerical effects connected to the resolution in the NBody simulation together with the resolution and bandlimit chosen to synthesise the CMB source plane. We found these quantities to be particularly important for the simulation of Bmode polarization power spectrum.
 Authors:
 SISSA, Via Bonomea 256, 34136, Trieste (Italy)
 I.N.A.F, Osservatorio Astronomico di Brera, Via Bianchi 46, 23807, Merate (Italy)
 Dipartimento di Fisica e Astronomia, Alma Mater Studiorum Universita' di Bologna, viale Berti Pichat 6/2, I40127, Bologna (Italy)
 Publication Date:
 OSTI Identifier:
 22525920
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2015; Journal Issue: 03; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; BORN APPROXIMATION; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; COSMIC PHOTONS; GRAVITATIONAL LENSES; LIGHT CONE; MULTIPOLES; POLARIZATION; RELICT RADIATION; RESOLUTION
Citation Formats
Calabrese, M., Fabbian, G., Baccigalupi, C., Carbone, C., and Baldi, M., Email: mcalabre@sissa.it, Email: carmelita.carbone@brera.inaf.it, Email: gfabbian@sissa.it, Email: marco.baldi5@unibo.it, Email: bacci@sissa.it. Multiple lensing of the cosmic microwave background anisotropies. United States: N. p., 2015.
Web. doi:10.1088/14757516/2015/03/049.
Calabrese, M., Fabbian, G., Baccigalupi, C., Carbone, C., & Baldi, M., Email: mcalabre@sissa.it, Email: carmelita.carbone@brera.inaf.it, Email: gfabbian@sissa.it, Email: marco.baldi5@unibo.it, Email: bacci@sissa.it. Multiple lensing of the cosmic microwave background anisotropies. United States. doi:10.1088/14757516/2015/03/049.
Calabrese, M., Fabbian, G., Baccigalupi, C., Carbone, C., and Baldi, M., Email: mcalabre@sissa.it, Email: carmelita.carbone@brera.inaf.it, Email: gfabbian@sissa.it, Email: marco.baldi5@unibo.it, Email: bacci@sissa.it. 2015.
"Multiple lensing of the cosmic microwave background anisotropies". United States.
doi:10.1088/14757516/2015/03/049.
@article{osti_22525920,
title = {Multiple lensing of the cosmic microwave background anisotropies},
author = {Calabrese, M. and Fabbian, G. and Baccigalupi, C. and Carbone, C. and Baldi, M., Email: mcalabre@sissa.it, Email: carmelita.carbone@brera.inaf.it, Email: gfabbian@sissa.it, Email: marco.baldi5@unibo.it, Email: bacci@sissa.it},
abstractNote = {We study the gravitational lensing effect on the Cosmic Microwave Background (CMB) anisotropies performing a raytracing of the primordial CMB photons through intervening largescale structures (LSS) distribution predicted by NBody numerical simulations with a particular focus on the precise recovery of the lensinduced polarized counterpart of the source plane. We apply both a multiple plane raytracing and an effective deflection approach based on the Born approximation to deflect the CMB photons trajectories through the simulated lightcone. We discuss the results obtained with both these methods together with the impact of LSS nonlinear evolution on the CMB temperature and polarization power spectra. We compare our results with semianalytical approximations implemented in Boltzmann codes like, e.g., CAMB. We show that, with our current Nbody setup, the predicted lensing power is recovered with good accuracy in a wide range of multipoles while excess power with respect to semianalytic prescriptions is observed in the lensing potential on scales ℓ ∼> 3000. We quantify the impact of the numerical effects connected to the resolution in the NBody simulation together with the resolution and bandlimit chosen to synthesise the CMB source plane. We found these quantities to be particularly important for the simulation of Bmode polarization power spectrum.},
doi = {10.1088/14757516/2015/03/049},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 03,
volume = 2015,
place = {United States},
year = 2015,
month = 3
}

We use a temperature map of the cosmic microwave background (CMB) obtained using the South Pole Telescope at 150 GHz to construct a map of the gravitational convergence to z {approx} 1100, revealing the fluctuations in the projected mass density. This map shows individual features that are significant at the {approx}4{sigma} level, providing the first image of CMB lensing convergence. We crosscorrelate this map with Herschel/SPIRE maps covering 90 deg{sup 2} at wavelengths of 500, 350, and 250 {mu}m. We show that these submillimeter (submm) wavelength maps are strongly correlated with the lensing convergence map, with detection significances in eachmore »

Cosmic microwave background anisotropies: Has a gravitational wave background been observed
We show that in the scalefree chaotic inflationary scenario with the inflaton potential [lambda][phi][sup 4]/4, largescale angular fluctuations in the cosmic microwave background radiation temperature generated by adiabatic density perturbations and gravitational waves are [ital generically] of the same order of magnitude and their ratio is parameter independent. In the inflationary models based on grand unified theories, these quantities can depend on different parameters and thus may differ by a large amount. The recent Cosmic Background Explorer observations have the potential to discover a cosmological background of gravitational waves and provide support for chaotic inflation or some other inflationary scenariomore » 
Nonlinear evolution of cosmic magnetic fields and cosmic microwave background anisotropies
In this work we investigate the effects of primordial magnetic fields on cosmic microwave background anisotropies (CMB). Based on cosmological magnetohydro dynamic (MHD) simulations [R. Banerjee and K. Jedamzik, Phys. Rev. D 70, 123003 (2004).] we calculate the CMB anisotropy spectra and polarization induced by fluid fluctuations (Alfven modes) generated by primordial magnetic fields. The strongest effect on the CMB spectra comes from the transition epoch from a turbulent regime to a viscous regime. The balance between magnetic and kinetic energy until the onset of the viscous regime provides a one to one relation between the comoving coherence length Lmore » 
USING COSMIC MICROWAVE BACKGROUND LENSING TO CONSTRAIN THE MULTIPLICATIVE BIAS OF COSMIC SHEAR
Weak gravitational lensing is one of the key probes of cosmology. Cosmic shear surveys aimed at measuring the distribution of matter in the universe are currently being carried out (PanSTARRS) or planned for the coming decade (DES, LSST, EUCLID, WFIRST). Crucial to the success of these surveys is the control of systematics. In this work, a new method to constrain one such family of systematics, known as multiplicative bias, is proposed. This method exploits the crosscorrelation between weaklensing measurements from galaxy surveys and the ones obtained from highresolution cosmic microwave background experiments. This crosscorrelation is shown to have the powermore »