• Login
    View Item 
    •   etd@IISc
    • Division of Physical and Mathematical Sciences
    • Physics (PHY)
    • View Item
    •   etd@IISc
    • Division of Physical and Mathematical Sciences
    • Physics (PHY)
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Exploring Scalar-Tensor Theories of Gravity in Light of Tensions and Anomalies in Standard Cosmology

    View/Open
    Thesis full text (5.323Mb)
    Author
    Tiwari, Yashi
    Metadata
    Show full item record
    Abstract
    The $\Lambda$CDM model, the standard model of cosmology, has been highly successful in describing a wide range of cosmological observations. However, in the era of precision cosmology, it faces increasing challenges in the form of persistent tensions—most notably the Hubble and $S_8$ tensions—as well as anomalies in the Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillation (BAO) data. These discrepancies motivate the exploration of extensions to General Relativity. In this thesis, we investigate subclasses of Horndeski gravity, a broad scalar-tensor framework that introduces an additional scalar degree of freedom while maintaining second-order field equations. At early times, we focus on generalised nonminimal derivative couplings during inflation, which generate large-scale oscillatory features in the primordial power spectrum and provide improved fits to CMB anomalies. At late times, we construct a dynamical dark energy model with nonminimal couplings and self-interactions, allowing for phantom crossing and a potential resolution to the Hubble tension. Using Bayesian analyses with CMB, BAO, and Supernova data, we evaluate these models' phenomenology and observational viability. Although $\Lambda$CDM remains statistically preferred in global fits, our results reveal a mild preference for nonzero modifications, underscoring the promise of scalar-tensor theories in addressing current cosmological tensions.
    URI
    https://etd.iisc.ac.in/handle/2005/7023
    Collections
    • Physics (PHY) [485]

    etd@IISc is a joint service of SERC & J R D Tata Memorial (JRDTML) Library || Powered by DSpace software || DuraSpace
    Contact Us | Send Feedback | Thesis Templates
    Theme by 
    Atmire NV
     

     

    Browse

    All of etd@IIScCommunities & CollectionsTitlesAuthorsAdvisorsSubjectsBy Thesis Submission DateThis CollectionTitlesAuthorsAdvisorsSubjectsBy Thesis Submission Date

    My Account

    LoginRegister

    etd@IISc is a joint service of SERC & J R D Tata Memorial (JRDTML) Library || Powered by DSpace software || DuraSpace
    Contact Us | Send Feedback | Thesis Templates
    Theme by 
    Atmire NV