Peter Millington, Florian Niedermann, Antonio Padilla

We carefully re-examine the evidence for non-trivial UV properties of galileon theories presented in arXiv:1502.05706. This relies on a particular interacting galileon theory that is said to be dual to a free theory through the action of a simultaneous field and coordinate transformation. By explicitly calculating the one-particle irreducible effective action on a maximally symmetric background, we show that this particular theory has a non-trivial vacuum structure, which is argued to affect its spectral properties at high energy scales. We isolate a semi-classical contribution to the Wightman functions that has not been taken into account in the previous analysis due to a singular point in the duality map. This suggests that the main evidence in support of a non-trivial UV structure is unreliable, leaving the path towards UV completion of galileons as open as it has ever been.

John T. Giblin Jr, James B. Mertens, Glenn D. Starkman, Andrew R. Zentner

We compute the weak lensing convergence power spectrum, $C^{\kappa\kappa}(\theta)$, in a dust-filled universe using fully non-linear general relativistic simulations. The spectrum is then compared to more standard, approximate calculations by computing the Bardeen (Newtonian) potentials in linearized gravity and utilizing the Born approximation. We find corrections to the angular power spectrum amplitude of order ten percent at very large angular scales, $\ell \sim 2-3$, and percent-level corrections at intermediate angular scales of $\ell \sim 20-30$.

A. Herrera-Aguilar, R. Cartas-Fuentevilla, J. A. Olvera-Santamaría

In this work we present solutions to the Ricci flow equations in $3d$ and $4d$. We note that our solutions belongs to the family of maximally symmetric spaces and can be extended to $4d$ following an analogue treatment to the $3d$ case. Our solutions can be divided into two scenarios: maximally symmetric spaces with positive curvature i.e. de Sitter spaces, and maximally symmetric spaces with negative curvature i.e. Anti-de Sitter spaces. We show that between both scenarios there is a "critical point" where the curvature blows up along the flow. Also the solution for $d\geq 4$ satisfies the flow equations with an Euclidean or Lorentzian signature. Additionally we find an interesting effect of the flow consisting in a change of the signature of the metric when passing from a positive curvature space to a negative curvature one, either with Euclidean or Lorentzian signature throughout the flow.