By using the regularization freedom of the Hamiltonian constraint for loop quantum gravity, the observational cosmological constant can emerge at large volume limit from the model of loop quantum cosmology, and the effective Newtonian constant satisfies the experimental restrictions in the meantime. Therefore, the so-called dark energy could be an emergent effect of LQG.
We show how cosmological dynamics can be mapped to hydrodynamics (on minisuperspace) via field symmetries. We then connect the same hydrodynamics (on minisuperspace) to several quantum gravity directions, starting from group field theory, and argue that it may represent a general effective framework for the cosmological sector of quantum gravity.
We analyze the evolution of scalar cosmological perturbations in a closed universe on a background described by a loop quantum cosmology model with an inflationary regime consistent with the constraints on inflation set by the observations of the CMB by the Planck mission. Initial conditions for the perturbations are set before the bounce, and the perturbations are numerically evolved until...
We study analytical approximate solutions for second-order homogeneous differential equations with the existence of only two turning points (but without poles) by using the uniform asymptotic approximation (UAA) method. To be more concrete, we consider the Pöschl-Teller (PT) potential, for which analytical solutions are known. Depending on the values of the parameters involved in the PT...
The evolution of the universe in modified loop quantum cosmologies exhibits universal properties for sharply peaked states, similar to that in the standard loop quantum cosmology (LQC). In this talk, I shall present our recent investigations on such universal properties for the modified loop quantum cosmological model I (mLQC-I), by paying particular attention to the evolution before the...
In Loop Quantum Cosmology (LQC), as in any other quantum theory, various regularizations of the Hamiltonian constraint and quantum ambiguities yield distinct physical implications. Specifically, the treatments of the Euclidean and Lorentzian parts of the Hamiltonian constraint for spatially flat, homogeneous, and isotropic spacetime before quantization results in alternative quantizations of...
Understanding the fundamental factors which shape the quantum structure of spacetime in loop quantized Bianchi-IX spacetimes offers valuable insights into the generic resolution of singularities and discerning the significance of anisotropies in the Planck regime. Conversely, it has been argued that ekpyrosis could mitigate the effects of anisotropies. Further, recent investigations into the...
We present the classical-quantum (CQ) hybrid dynamics of homogeneous cosmology from a Hamiltonian perspective where the classical gravitational phase space variables and matter state evolve self-consistently with full backreaction. We compare numerically the classical and CQ dynamics for isotropic and anisotropic models, including quantum scalar-field induced corrections to the Kasner...
I will present an ongoing work about the evolution of a two-field bouncing scenario in Loop Quantum Cosmology. The model features a quasi-dust field with a slightly negative equation of state, dominating in the far past of the contraction phase, which is known as a possible candidate to explain the red tilt observed in the CMB power spectrum. To avoid instabilities, an ekpyrotic field...
We provide a new picture for the emergence of a bouncing cosmology at a pure quantum level, according to the idea that a semiclassical behavior of the Universe towards the singularity is not available in many relevant Minisuperspace models. In particular, we clarify how any Bianchi I localized wave packet unavoidably spreads when the singularity is approached, and therefore the semiclassical...
Next generation CMB experiments may provide stronger constraints for primordial observables that are sensitive to the semi-classical regime of quantum gravity. Here we present some tools to compare the predictions for the primordial power spectrum, tilt, running and running-of-the-running given by generic models of slow-roll inflation. These tools have been used in an effective field theory...
We address the problem of the SU(2) internal symmetry in Loop Quantum Cosmology (LQC) and its relationship with canonical Loop Quantum Gravity (LQG). We introduce new tools to treat non-diagonal Bianchi models in LQC, and we discuss the Gauss constraint and the role of gauge freedom. This allows us to prove that, in the minisuperspace cosmological framework, there exist suitable variables in...
We explain the analysis of the compact binary system dynamics in the Post-Newtonian approach adding the cosmological constant $\Lambda$ at the first Post-Newtonian (PN) order from the Einstein-Hilbert action. Considering small values of $\Lambda$ we find that it plays the role of a PN factor, and we us this feature to compute the Lagrangian of a binary compact system at the center of mass...
The concept of spacetime discreteness is a common feature in quantum gravity theories. Recently, it has been speculated that the presence of discrete fundamental degrees of freedom should ultimately manifest, at least in the low-energy regime, in the form of diffusive effects, just as the presence of molecules generates diffusion in fluids. As for an effective description, such dissipation...
