Oem Trivedi

It has been known for about hundred years that the universe is expanding, but an impressive discovery came at the end of 20th century, when it was found that the universe is expanding with acceleration. Since then, many models have been developed in cosmology to explain this phenomenon. One of the possible elucidations is that the theory of gravity must be modified at the classical level. However, many such models have already been excluded by gravitational wave experiments. Therefore, one must put a more critical question: could accelerated expansion of the universe be a phenomenon of quantum gravity? Here, we review the basic models of how one explains the origin of dark energy or the cosmological constant in metastring theory, discrete approaches to quantum gravity, group field theory, non-commutative geometry, causal dynamical triangulation, asymptotic safety, and models based on holography and entropic gravity. At the end of a newly formed approach to the quantization of gravity, we mention the ring paradigm, which may, after application to cosmology, naturally model the late-time accelerated expansion epoch in the universe. What is most remarkable, though, is that the final formulation of this theory may ultimately solve the old problem of the cosmological constant.

The multi-messenger exploration of dark matter and physics beyond the Standard Model has emerged as a central direction in modern astro-particle physics, particularly following the discovery of gravitational waves. In this work, we present a comprehensive review and forward-looking perspective on machine-learning-enhanced multi-messenger approaches, combining information from gravitational waves, cosmic rays, gamma rays, neutrinos, and collider experiments. We summarize the current state of the field, discuss recent methodological developments, and outline a coherent research program aimed at integrating heterogeneous datasets within a unified inference framework. We collaboratively propose a plan for forthcoming analyses aiming at extracting information on the properties and interactions of dark matter, and finally on its genesis, combining multi-messenger astronomy techniques and inputs from laboratory physics. The main objectives planned in this line of research comprise: (i) the multi-messenger analysis of new physics in cosmology, including mainly, but not only, several different models of dark matter; (ii) the phenomenology of new physics signatures in ground-based cosmic rays experiments, with cross-correlation to the corresponding physical, astrophysical and cosmological observations; (iii) the development of machine learning methods for data analysis in ground-based cosmic rays experiments, in light of the new physics signatures. We note that several groups have explored the use of multi-messenger observations, including gravitational waves, to probe alternative dark matter candidates. The present work builds on these developments by focusing on the role of machine learning in integrating heterogeneous datasets. We foresee that a cross-fertilizing approach combining the information that arises from very different experimental methodologies will represent the right and successful path to extract information about the very elusive dark matter particles and provide answers to the main questions that are left in fundamental physics.

We develop Polymer Network Cosmic Teleodynamics (PNCT), a covariant effective framework in which the cosmic web is modeled as a percolating, memory-bearing, self-gravitating network whose constitutive response is guided by viscoelastic polymer physics. Affine filament stretching, transverse tidal confinement, and nonlocal strain memory generate, respectively, an effective dark energy-like background component, environment-dependent clustering corrections, and a history-dependent teleodynamic bias functional. The central structural event is a sol-gel-like percolation transition at z _* ∼ 1-2, after which a coherent spanning web stores elastic free energy and can drive late-time acceleration. The resulting effective equation of state exhibits a three-stage trajectory, including phantom-like growth near activation, phantom divide crossing as transverse coherence is lost, and relaxation toward w _TD → −1 ⁺ through gravitational saturation and post-gel strand balance. The framework predicts two testable observables: synchronization between cosmic web percolation and dark sector activation, and environment-dependent growth/lensing residuals in nodes, filaments, walls, and voids. These signatures are testable with DESI, Euclid, Roman, and LSST and would distinguish PNCT from smooth dark energy models and generic scale-dependent modified gravity.