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Investigating the Cosmic Web with the One-point Letter Function Statistics in the Presence of Massive Neutrinos

Khoshtinat, Mohadeseh | 2025

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 58287 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Baghram, Shant
  7. Abstract:
  8. The standard model of cosmology—the ΛCDM model, successfully predicted almost all the observations from the Cosmic Microwave Background and the Large-Scale Structure surveys. However, as the observational data sets become more accurate and finer on small scales, the deviations between the predicted and observed quantities increase. In addition to the tensions arising from observational data, fundamental questions about the nature of the dark sector of the Universe have given rise to a rich literature around the possible extension of the ΛCDM, to mention a few, the decided massive neutrino inclusion, the interacting and/or clustering dark energy, and deviation from Gaussian initial condition. To this point, most of these studies used the two-point correlation function as the primary tool to study the cosmological data and the matter density field. The two-point correlation function is an ideal tool up to the linear scales, beyond which, due to the gravitational effect, the density field is no longer Gaussian, and the information leaks to the higher-order correlations. The leaked information on the higher-order correlations is of the utmost importance since one can differentiate between various extensions of the ΛCDM models based on this information that the two-point correlation function cannot capture. This situation calls for complementary tools for studying the cosmological data set. This situation calls for complementary tools for studying the cosmological data set. Accordingly, in this thesis, we deploy the one-point statistics, the letter functions—G, F, and J functions, to study the spatial pattern of the halo catalogues of a simulation set with the box-size of 2048 h−1Mpc with the total mass of Σmν = 0, 0.06, 0.2, 0.3 eV. Our results show that this method can differentiate between the standard model and the massive neutrino model. Furthermore, we calculate these statistics in various cosmic environments, and upon that, the voluminous environments (voids and sheets) are the best choice to set an upper limit on the total neutrino mass. On top of that, we find a footprint of neutrinos at scales less than a megaparsec
  9. Keywords:
  10. Large Scale Structure ; Universe Large-Scale Structure ; Cosmic Web ; Massive Neutrinos ; One-Point Statistics: The Letter Functions

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