Tag: Cosmology and Gravitation Theories
Interacting dark energy and dark matter models fit current data
What the study found The study found that two versions of a cosmological model with interacting dark energy and dark matter can fit current observations well. The models use a Gauss–Bonnet-coupled scalar field as dark energy and a fermionic dark matter field, with either an exponential or a power-law scalar potential. Why the authors say…
Pancakes in 2D cosmic structure are mostly C-shaped
What the study found In 2D cold dark matter cosmologies, the study found that many pancakes evolve into filaments, while pancakes that evolve into halos are more strongly curved. The shapes are mostly C-shaped, and shell crossing is highly anisotropic, meaning it differs by direction. Why the authors say this matters The authors say this…
Particle creation model explains cosmic expansion without dark energy
What the study found A dark-energy-free cosmological model based on gravitationally induced adiabatic particle creation is proposed. The authors report that it can reproduce a Lambda CDM-like expansion for suitable values of its parameters and that it evolves smoothly between two de Sitter phases. Why the authors say this matters The authors conclude that the…
Wavefunction collapse is proposed as a source of time and emergent gravity modes
What the study found The paper develops a proposed theory in which wavefunction collapse in general relativity gives rise to time. In this framework, quantum states that violate the momentum and Hamiltonian constraints represent instances of time, and stochastic fluctuations of the lapse and shift drive evolution toward a diffeomorphism-invariant state. Why the authors say…
Starobinsky model remains viable in parts of parameter space
What the study found The authors report that, despite recent data placing pressure on the pure Starobinsky inflation model, there is still a significant region of parameter space where the model remains highly consistent with the latest observations. They also say that adding a cubic $R^3$ term can shift the model's predictions toward better agreement…
Non-Gaussian redshift-space Minkowski tensors show qualified perturbation-theory success
What the study found The study found that perturbation-theory predictions for Minkowski tensors in redshift space are a qualified success when compared with dark matter simulation measurements. It also found that nonperturbative Finger-of-God effects remain significant at relatively large scales, especially in components parallel to the line of sight. Why the authors say this matters…
Minimal asymmetric dark matter model uses Higgs-portal mediation
What the study found The study presents a minimal asymmetric dark matter model in which the dark sector contains a stable neutral Dirac fermion X and a real scalar mediator ϕ, with the mediator coupled to the Standard Model through a Higgs portal. The authors say that if dark and baryonic asymmetries are of comparable…
Separability of gravitational wave equations in rotating black hole geometries
Analytical study of gravitational wave propagation in Myers-Perry higher-dimensional rotating black holes using separation of variables techniques to derive explicit solutions.
Dark matter halo alters black hole optics and thermodynamics
Exact black hole solution in cored Plummer dark matter halo showing modified photon dynamics, shadows, lensing, quasinormal modes, and novel phase transitions absent in Schwarzschild spacetime.
