Personal website
Here you can find a bit more about my research interests. This includes both themes I’ve actually worked on or have been working on and some themes that draw my attention.
Was there anything before the Big Bang? Cosmic inflation is a theoretical framework in which certain models can produce primordial perturbations that successfully explain a wide range of cosmological observations, including the nature of anisotropies in the temperature fluctuations of the cosmic microwave background (CMB), and the quantum origin of the large scale structure of the Universe.
In [1] we explored a broad family of effective theories of inflation, and computed the next-to-next-to-next-to-leading (N3LO) order corrections to the primordial power spectrum, for an arbitrary Scalar-Vector-Tensor mode. Moreover, we use this framework to compute N3LO corrections of Starobinsky inflation, where we found a 7% decrease of the tensor-to-scalar ratio, in comparison to the standard expression.
In [2] we study how the initial conditions regarding the vacuum state of the primordial perturbations can induce drastic features on the primordial power spectrum. The new excited vacuum states are denoted as “squeezed vacua” and arise when a pre-inflationary epoch is described by the dynamics of the geometry.
How quantum matter interact with the classical spacetime? In semi-classical gravity, one quantizes the matter fields while keeping the geometry classical. The quantization procedure has a lot subtleties that need to be considered with care, e.g., renormalization ambiguities. A self-consistent framework has been available for quite some time, but a few questions still remain open.
From a phenomenological point of view, understanding semi-classical gravity is crucial for cosmic inflation, as the primordial perturbations are understood to have a quantum origin. In [1] we study in detail Starobinsky inflation, a sub-sector of semi-classical gravity that provides a purely gravitational mechanism for inflation, with great phenomenological success.
Does spacetime have a quantum nature? After all, semi-classical gravity is only a first approximation to a quite bigger problem, a complete and consistent description of the quantum theory of gravity. A non-perturbative and background independent approach to address this issue is Loop Quantum Gravity, a framework that suggests at the smallest scales space is composed of discrete “atoms” of geometry, i.e., discreteness of spacetime at the Planck scale.
In [3], collaborators and I are exploring the covariant formulation of LQG, the spinfoam approach. In particular, we study different aspects of causality in the EPRL model, a proposal that succesfully recovers the classical Regge action of general relativity in the large spin limit.
[1] E. Bianchi and M. Gamonal, “Primordial power spectrum at N3LO in effective theories of inflation,” arXiv:2405.03157 [gr-qc].
[2] E. Bianchi and M. Gamonal, “Squeezed vacua in effective theories of inflation,” To appear.
[3] E. Bianchi, C. Chen, M. Gamonal and Monica Rincon-Ramirez, “Causal EPRL model,” To appear.