### Conveners

#### Parallel session 10 (Cosmology Beyond GR)

- Session convener: Mariam Bouhmadi-Lopez

Recently Harada proposed a new gravitational theory which is third order in the derivatives of the metric tensor. This has attracted some attention particularly as it predicts a late-time transition from cosmological deceleration to accelerated expansion without assuming the presence of dark-energy or a non-zero cosmological constant. This theory has become known as conformal Killing gravity...

In this presentation, we will review recent advancements in the symmetric teleparallel equivalent of general relativity (STEGR) as an alternative framework for numerical relativity. Initially, we will introduce the metric 3+1 formalism, the Hamiltonian of STEGR and the equations of motion in the 3+1 decomposition. After assessing the implications of the results in numerical relativity, we...

We study a Symmetric Teleparallel Gravity with a Lagrangian of Logarithmic form. The full model leads to an accelerated Universe and for specific values of the free parameters the Hubble rate reduces to the well known DGP model, though the evolution of the gravitational potentials are different. We consider different branches of the Logarithmic model, among which sDGP and nDGP. The...

In this talk we explore the possibility of describing an interacting dark sector as result of breaking the invariance under diffeomorphism of the matter action. Particularly, we consider two scalar fields with different non-canonical minimal couplings to gravity. We consider the potential and kinetic domination regimes for each field and analyze the resulting models. Then, we focus on cases...

General relativity (GR) is the most successful theory of gravity, with great observational support at local scales. However, to keep GR valid at cosmic scales, some phenomena (such as the flat galaxy rotation curves and the cosmic acceleration) require the assumption of exotic dark matter and dark energy. Similarly to the mass-luminosity relation or baryonic Tully-Fisher relation (BTFR) and...

In a growing number of recent works, it has been claimed that "gravitomagnetism" and/or non-linear general relativistic effects can play a leading role in galactic dynamics, partially or totally replacing dark matter. Using the 1+3 "quasi-Maxwell" formalism (and generalizing it for null geodesics), we show, on general grounds, such hypothesis to be impossible. We demonstrate that (i) the...