Cosmological observations on the largest scales exhibit a solid record of unexpected anomalies and alignments, apparently pointing towards a large scale violation of statistical isotropy. These include a variety of CMB measurements, as well as alignments of quasar polarisation vectors. In this paper we explore the possibility that several of the aforementioned large scale correlations are in fact not independent, and can be understood in a coherent way within the framework of a parity odd local Universe, and ultimately related to the nature of Dark Energy and its interactions with light.
We search for a direction in the sky that exhibits parity symmetry under reflections through a plane. We use the natural estimator, which compares the power in even and odd $\ell+m$ multipoles, and apply minimal blind masking of outliers to the ILC map in order to avoid large errors in the reconstruction of multipoles. The multipoles of the cut sky are calculated both naively and by using the covariance inversion method and we estimate the significance of our results using $Λ$CDM simulations. Focusing on low multipoles, $2\leq \ell \leq \ell_{\max}$ with $\ell_{\max}=5,6$ or even 7, we find tw…
We develop a methodology for estimating parity-odd bispectra in the cosmic microwave background (CMB). This is achieved through the extension of the original separable modal methodology to parity-odd bispectrum domains ($\ell_1 + \ell_2 + \ell_3 = {\rm odd}$). Through numerical tests of the parity-odd modal decomposition with some theoretical bispectrum templates, we verify that the parity-odd modal methodology can successfully reproduce the CMB bispectrum, without numerical instabilities. We also present simulated non-Gaussian maps produced by modal-decomposed parity-odd bispectra, and show t…
Parity-odd non-Gaussianities create a variety of temperature bispectra in the cosmic microwave background (CMB), defined in the domain: $\ell_1 + \ell_2 + \ell_3 = {\rm odd}$. These models are yet unconstrained in the literature, that so far focused exclusively on the more common parity-even scenarios. In this work, we provide the first experimental constraints on parity-odd bispectrum signals in WMAP 9-year temperature data, using a separable modal parity-odd estimator. Comparing theoretical bispectrum templates to the observed bispectrum, we place constraints on the so-called nonlineality pa…
We develop the connection between intergalactic helical magnetic fields and parity odd signatures in the diffuse gamma ray sky. We find that the location and the amplitude of a peak in a parity odd correlator, $Q(R)$, can be used to infer the normal and helical power spectra of the intergalactic magnetic field. When applied to Fermi-LAT data, the amplitude of the observed peak in $Q(R)$ gives $\sim 10^{-14}~{\rm G}$ intergalactic magnetic field strength, which is consistent with an earlier independent estimate that only used the peak location (Tashiro et al. 2014). We discuss features in the o…
In scalar-vector-tensor theories with $U(1)$ gauge invariance, it was recently shown that there exists a new type of hairy black hole (BH) solutions induced by a cubic-order scalar-vector interaction. In this paper, we derive conditions for the absence of ghosts and Laplacian instabilities against odd-parity perturbations on a static and spherically symmetric background for most general $U(1)$ gauge-invariant scalar-vector-tensor theories with second-order equations of motion. We apply those conditions to hairy BH solutions arising from the cubic-order coupling and show that the odd-parity sta…
Measurement of the cosmic microwave background (CMB) bispectrum, or three-point correlation function, has now become one of the principle efforts in early-Universe cosmology. Here we show that there is a odd-parity component of the CMB bispectrum that has been hitherto unexplored. We argue that odd-parity temperature-polarization bispectra can arise, in principle, through weak lensing of the CMB by chiral gravitational waves or through cosmological birefringence, although the signals will be small even in the best-case scenarios. Measurement of these bispectra requires only modest modification…
Twisted echoes of an odd quartet: Scalar-induced gravitational waves as a probe of primordial parity-violation
Università degli Studi di Padova（帕多瓦大学）；Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Padova（意大利国家核物理研究所帕多瓦分部）；Istituto Nazionale di Astrofisica (INAF), Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）
Bipolar spherical harmonics (BiPoSHs) provide a general formalism for quantifying departures in the cosmic microwave background (CMB) from statistical isotropy (SI) and from Gaussianity. However, prior work has focused only on BiPoSHs with even parity. Here we show that there is another set of BiPoSHs with odd parity, and we explore their cosmological applications. We describe systematic artifacts in a CMB map that could be sought by measurement of these odd-parity BiPoSH modes. These BiPoSH modes may also be produced cosmologically through lensing by gravitational waves (GWs), among other sou…
We compare the statistics of parity even and odd multipoles of the cosmic microwave background (CMB) sky from PLANCK full mission temperature measurements. An excess power in odd multipoles compared to even multipoles has previously been found on large angular scales. Motivated by this apparent parity asymmetry, we evaluate directional statistics associated with even compared to odd multipoles, along with their significances. Primary tools are the \emph{Power Tensor} and \emph{Alignment Tensor} statistics. We limit our analysis to the first sixty multipoles i.e., $l=[2,61]$. We find no evidenc…
The galaxy bispectrum contains a wealth of information about the early universe, gravity, as well as astrophysics such as galaxy bias. In this paper, we study the parity-odd part of the galaxy bispectrum which is hitherto unexplored. In the standard cosmological model, the odd-parity bispectrum is generated by galaxy velocities through redshift-space distortions. While small in the case of General Relativity coupled with smooth dark energy, the signal could be larger in modified gravity scenarios. Thus, apart from being a very useful consistency test of measurements of galaxy clustering, the o…
The odd parity gravitational Quasi-Normal Mode spectrum of black holes with non-trivial scalar hair in Horndeski gravity is investigated. We study `almost' Schwarzschild black holes such that any modifications to the spacetime geometry (including the scalar field profile) are treated as small quantities. A modified Regge-Wheeler style equation for the odd parity gravitational degree of freedom is presented to quadratic order in the scalar hair and spacetime modifications, and a parameterisation of the modified Quasi-Normal Mode spectrum is calculated. In addition, statistical error estimates f…
We derive a set of no-go theorems and yes-go examples for the parity-odd primordial trispectrum of curvature perturbations. We work at tree-level in the decoupling limit of the Effective Field Theory of Inflation and assume scale invariance and a Bunch-Davies vacuum. We show that the parity-odd scalar trispectrum vanishes in the presence of any number of scalar fields with arbitrary mass and any parity-odd scalar correlator vanishes in the presence of any number of spinning fields with massless de Sitter mode functions, in agreement with the findings of Liu, Tong, Wang and Xianyu [1]. The same…
We have investigated the angular correlation in the recent CMB data. In addition to the known large-angle correlation anomaly, we find the lack of correlation at small angles with high statistical significance. We have investigated various non-cosmological contamination and additionally WMAP team's simulated data. However, we have not found a definite cause. In the angular power spectrum of WMAP data, there exist anomalous odd-parity preference at low multipoles. Noting the equivalence between the power spectrum and the correlation, we have investigated the association between the lack of larg…
Cosmological observations are promising ways to improve our understanding of neutrino mass properties. The upper bound on the sum of masses is given by the cosmic microwave background and large scale structure. These measurements are all parity-even, and potentially contaminated by unmodeled baryonic effects. In this paper we propose a novel parity-odd gravitational effect of neutrinos: A unique contribution to the directions of the angular momentum field of galaxies and halos. This observable is free of contamination in linear perturbation theory, and thus likely more cleanly separated from o…
We have investigated the odd-parity preference of the WMAP 7 year power spectrum. Comparison with simulation shows the odd-parity preference of WMAP data (2<= l <=22) is anomalous at 4-in-1000 level. We have investigated its origins, and ruled out some of non-cosmological origins such as asymmetric beams, noise and cut-sky effect. We also find primordial origin requires |Re[Φ(\mathbf k)]|\ll|Im[Φ(\mathbf k)]| for k\lesssim 22/η_0, where η_0 is the present conformal time. Multipoles associated with the odd-parity preference happen to coincide with some of other CMB anomalies. Therefore, there m…
