Laboratory of Information Technologies

Seminar of the Scientific Department of Computational Physics

Date and Time: Tuesday, 24 June 2025, at 3:00 PM

Venue: room 310, Meshcheryakov Laboratory of Information Technologies

Seminar topic: “Spinor field in cosmology with Lyra’s geometry”

Speaker: Saha Bijan

Abstract:

The Standard Model of Cosmology (SMC), known as the ΛCDM model (Lambda-Cold Dark Matter), is based on three fundamental assumptions: the validity of General Relativity on cosmological scales; the correctness of the Standard Model of particle physics at small (quantum) scales; and the cosmological principle, which posits that the Universe is spatially homogeneous, isotropic, and infinite on large scales. According to this model, the Universe originated from a Big Bang, emerging from a state of pure energy. The present-day energy composition of the Universe is estimated to be approximately 5% ordinary (baryonic) matter, 27% dark matter, and 68% dark energy. Despite its simplicity, the ΛCDM model successfully explains a wide range of cosmological observations, including Type Ia supernovae, cosmic microwave background radiation (CMBR) anisotropies, large-scale structure formation, gravitational lensing, and baryon acoustic oscillations. However, it faces theoretical challenges, notably severe fine-tuning problems related to the vacuum energy (cosmological constant) scale. These shortcomings motivate the exploration of alternative cosmological models. In such alternatives, researchers often seek to modify Einstein’s field equations by introducing additional terms in the gravitational Lagrangian (beyond the Ricci scalar) or by considering non-Riemannian geometries. In addition, some approaches involve exotic matter or field sources. This study examines cosmological models formulated within the framework of Lyra’s geometry to analyse the influence of a nonlinear spinor field on the Universe’s evolution. While the core field equations remain largely analogous to those in General Relativity, Lyra’s geometry introduces modifications through the presence of a displacement vector field, which in turn affects the behaviour of the spinor field via its invariants.