Abstract Details
| Name: Rahul Kothari Affiliation: IIT Madras Conference ID: ASI2018_1580 Title : On the Study of CMB Dipole Modulation and Its Relationship with Spatial Inhomogeneity and Spacetime Noncommutativity Authors and Co-Authors : Shamik Ghosh (IIT Kanpur) Pranati Rath (IHEP, China) Pankaj Jain (IIT Kanpur) Gopal Kashyap (Galgotia University Noida) Abstract Type : Thesis Abstract Category : Thesis Abstract : Cosmic Microwave Background Radiation (CMBR) has been an important observational tool for testing cosmological theories since its discovery in 1964. The radiation was predicted as a consequence of the Big Bang Cosmology. CMBR is characterized by angular dependence of its temperature field. Discovery of polarization in 2002 opened new gates to its understanding. Statistical properties of CMBR can be understood by studying correlation of field at two different angular locations. A condition known as cosmological principle states that this correlation should depend only on the angle between the points and be independent of their angular locations. Furthermore, the correlation is measured with a quantity known as power. For a long time the temperature field was assumed to satisfy the cosmological principle. The same principle would imply equal powers in any two given hemispheres. Yet in 2004, different amount of powers was found in different patches of the sky, thereby posing a potential violation of the cosmological principle. This anomaly was termed as Hemispherical Power Asymmetry. Please note that the effect is found only at large angular scales, i.e., the correlation starts to depend upon angular locations only if points are widely separated. The dissertation explores the possibility of studying this isotropy violation by modifying initial cosmological conditions. The basic idea is that universe acquires isotropy during later stages of exponential expansion of universe known as inflation. So it is these anisotropic signatures which are responsible for Power Asymmetry. We studied Power Asymmetry using two models designated as 'anisotropic' and 'inhomogeneous'. The predictions of models were found to be very interesting. The two models suggest complete opposite behaviours. Thus, it will be fascinating to rule out one of the models based on observations. At this stage, the modification of initial conditions and introduction of two models might seem ad hoc. It would be desirable to derive them with the help of fundamental physics. We found an unexpected relation between the anisotropic model and spacetime noncommutativity. Spacetime noncommutativity is the fascinating regime of quantum gravity. Thus our idea relates the Physics happening at quantum gravity scales which are the smallest conceivable scales with Power Asymmetry, observed at largest angular scales. The Power Asymmetry in CMB temperature field can be studied by giving it a preferred direction. This is called as field modulation. Now, it is possible that physics causing power asymmetry in the temperature field can give rise to a similar effect in the polarisation as well. In the dissertation, we studied a specific kind of modulation introduced in the polarization field. Amazingly, we found that correlations are beautifully related to combinatorics and algebra. |