Search Publications
Constraints on primordial magnetic fields from the optical depth of the cosmic microwave background
Komatsu, Eiichiro; Kunze, Kerstin E.
Damping of magnetic fields via ambipolar diffusion and decay of magnetohydrodynamical (MHD) turbulence in the post decoupling era heats the intergalactic medium (IGM). Delayed recombination of hydrogen atoms in the IGM yields an optical depth to scattering of the cosmic microwave background (CMB). The optical depth generated at z ≫ 10 does not aff…
Constraints on the Nambu-Goto cosmic string contribution to the CMB power spectrum in light of new temperature and polarisation data
Lazanu, Andrei; Shellard, Paul
Cosmic strings generate vector and tensor modes in the B-channel of polarisation, as well as the usual temperature power spectrum and E-mode polarisation spectrum. We use the power spectrum obtained from high-resolution Nambu-Goto cosmic string simulations together with the Planck and BICEP2 likelihoods to explore the degeneracies appearing betwee…
Accurate shear measurement with faint sources
Zhang, Jun; Luo, Wentao; Foucaud, Sebastien
For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions …
Constraining the evolution of the CMB temperature with SZ measurements from Planck data
Martins, C. J. A. P.; De Petris, M.; Génova-Santos, R. T. +2 more
The CMB temperature-redshift relation, TCMB(z)=T0(1+z), is a key prediction of the standard cosmology but is violated in many non-standard models. Constraining possible deviations from this law is an effective way to test the ΛCDM paradigm and to search for hints of new physics. We have determined TCMB(z), with a p…
Constraints on µ-distortion fluctuations and primordial non-Gaussianity from Planck data
Khatri, Rishi; Sunyaev, Rashid
We use the Planck HFI channel maps to make an all sky map of µ-distortion fluctuations. Our µ-type distortion map is dominated by the y-type distortion contamination from the hot gas in the low redshift Universe and we can thus only place upper limits on the µ-type distortion fluctuations. For the amplitude of µ-type distor…
Robustness of cosmic neutrino background detection in the cosmic microwave background
Verde, Licia; Tram, Thomas; Cuesta, Antonio J. +9 more
The existence of a cosmic neutrino background can be probed indirectly by CMB experiments, not only by measuring the background density of radiation in the universe, but also by searching for the typical signatures of the fluctuations of free-streaming species in the temperature and polarisation power spectrum. Previous studies have already propos…
Non-local bias in the halo bispectrum with primordial non-Gaussianity
Ross, Ashley J.; Tasinato, Gianmassimo; Wands, David +1 more
Primordial non-Gaussianity can lead to a scale-dependent bias in the density of collapsed halos relative to the underlying matter density. The galaxy power spectrum already provides constraints on local-type primordial non-Gaussianity complementary those from the cosmic microwave background (CMB), while the bispectrum contains additional shape inf…
Disorder in the early universe
Green, Daniel
Little is known about the microscopic physics that gave rise to inflation in our universe. There are many reasons to wonder if the underlying description requires a careful arrangement of ingredients or if inflation was the result of an essentially random process. At a technical level, randomness in the microphysics of inflation is closely related…
Surfing gravitational waves: can bigravity survive growing tensor modes?
Amendola, Luca; Pettorino, Valeria; Könnig, Frank +2 more
The theory of bigravity offers one of the simplest possibilities to describe a massive graviton while having self-accelerating cosmological solutions without a cosmological constant. However, it has been shown recently that bigravity is affected by early-time fast growing modes on the tensor sector. Here we argue that we can only trust the linear …
Observational consistency and future predictions for a 3.5 keV ALP to photon line
Conlon, Joseph P.; Rummel, Markus; Alvarez, Pedro D. +2 more
Motivated by the possibility of explaining the 3.5 keV line through dark matter decaying to axion-like particles that subsequently convert to photons, we study ALP-photon conversion for sightlines passing within 50 pc of the galactic centre. Conversion depends on the galactic centre magnetic field which is highly uncertain. For fields at low or mi…