MSV-2035 Astronomy Document - Inside Design - FINAL - FINAL

2 LEADING ASTROPHYSICAL QUESTIONS The field ofAstronomy &Astrophysics is entering a new era of exploration with the large sky survey programmes that will discover new phenomenon, the extremely large optical/IR telescopes that will allow studies of stars and galaxies at the dawn of the Universe, and the study of planets similar to the Earth around other stars, and the giant radio telescopes that will reveal how the early Universe was transformed by the early galaxy formation. The detection of gravitational waves has opened a new window to study the most extreme environments in the Universe. Ever improving computing facilities enable one to have simulations as realistic as possible. The far-reaching new observational data generated will confront theoretical models and simulations and enable an unprecedented understanding of the Universe, as well as test the laws of fundamental physics at different scales and epochs. Identified below are key areas and questions that Indian astronomers propose to address and make significant contributions to the global quest for understanding our Universe. 2.1 Fundamental Physics Astronomical observations are interpreted in the framework of basic physics, as we understand on Earth, being time and space independent. For example, while we assume all fundamental interactions are universal, some theories (higher dimensional models or cosmological models with quintessence) allow for their space and time-variations. If dimensionless constants (for example, electromagnetic coupling constant) of interactions have time and space variations, they will have a major impact on our understanding of the Universe. Similarly, it is important to test the validity of fundamental theories like general relativity (GR) at different scales under different astrophysical environments. Therefore, it is extremely important to observationally verify (a) whether the fundamental physical interactions are universal, irrespective of time and space, (b) validity of general relativity across all scales of astrophysical interest, (c) whether gravity is a fundamental interaction or an emergent phenomenon, and (d) the physics that dominates the interactions at supranuclear density expected in the centers of the neutral stars in the early Universe. It is nowwell established from a wide range of astronomical observations that about 84%of the non-relativistic matter in the Universe is dark, i.e., it has very weak and as yet undetected interactions with photons and fermions of the Standard Model. Most of the evidences point to the “dark matter” being composed of new fundamental particles beyond the StandardModel of Particle Physics. On the other hand, the observed accelerated expansion of the Universe today indicates the presence of a new exotic form of matter/energy in the Universe with negative pressure (referred to as “dark energy”). Understanding “dark matter” and “dark energy” and any possible interplay between them is very important to understand our Universe and the formation and evolution of large scale structure probed by different observational probes. Therefore, it is of utmost importance to know the constitution of both dark matter and dark energy, the self-interaction cross-section of dark matter, and the origin of matter-antimatter asymmetry of the Universe. To understand these aspects, it might become important to explore the need for a change in the physical concepts as we understand today [likeMOdifiedNewtonianDynamics (MOND)]. 2.2 EarlyUniverse andCosmology In the “Big Bang” model, the Universe originated in a singularity. It went through an initial exponentially expanding phase (called “inflation”) that explains why the Universe is homogeneous and isotropic and explains presence of Astronomy & Astrophysics 13 MEGA SCIENCE VISION-2035