The seminar series *De Madrid al
Cosmos* ("From Madrid to
the Cosmos") fosters the dissemination of research in theoretical
cosmology and related topics. The seminars are accesible to a
non-specialist public with some knowledge of fundamental physics.

The seminars are organized jointly by
the *Effective
Theories in
Modern Physics Group* of the Complutense
University of Madrid and the *Gravitation and
Cosmology Group* of the Institute
for the Structure of Matter (IEM-CSIC).

## Next seminar

### Primordial fluctuations in Loop Quantum Cosmology

Speaker: Mercedes Martín-Benito

Affiliation: UCM

Abstract: A lot of attention has been devoted lately to the consideration of quantum corrections to the power spectrum of primordial fluctuations, as a possible window to unveil quantum geometry phenomena in the Early Universe. In this talk I will review the derivation of these corrections in the framework of hybrid Loop Quantum Cosmology (LQC). Homogeneous LQC provides a canonical quantization for FLRW models free of singularities: the classical big bang singularity is replaced by a quantum bounce, the quantum dynamics is everywhere well-defined, and physical observables never diverge. On the other hand, hybrid LQC extends the LQC quantization to systems with inhomogeneities. For the particular case of cosmological perturbations in flat FLRW supplemented with inflation, I will analyze the quantum dynamics of states that verify a Born-Oppenheimer ansatz. They describe a regime where the cosmological perturbations can be regarded as a field propagating over a homogeneous quantum geometry. From those states, we will recover a Mukhanov-Sasaki equation for cosmological perturbations that incorporates the mentioned quantum corrections. Such corrections are encoded in the expectation value of operators of the homogeneous geometry. I will discuss how these corrections might lead to observational imprints in the primordial power spectra.

Abstract: A lot of attention has been devoted lately to the consideration of quantum corrections to the power spectrum of primordial fluctuations, as a possible window to unveil quantum geometry phenomena in the Early Universe. In this talk I will review the derivation of these corrections in the framework of hybrid Loop Quantum Cosmology (LQC). Homogeneous LQC provides a canonical quantization for FLRW models free of singularities: the classical big bang singularity is replaced by a quantum bounce, the quantum dynamics is everywhere well-defined, and physical observables never diverge. On the other hand, hybrid LQC extends the LQC quantization to systems with inhomogeneities. For the particular case of cosmological perturbations in flat FLRW supplemented with inflation, I will analyze the quantum dynamics of states that verify a Born-Oppenheimer ansatz. They describe a regime where the cosmological perturbations can be regarded as a field propagating over a homogeneous quantum geometry. From those states, we will recover a Mukhanov-Sasaki equation for cosmological perturbations that incorporates the mentioned quantum corrections. Such corrections are encoded in the expectation value of operators of the homogeneous geometry. I will discuss how these corrections might lead to observational imprints in the primordial power spectra.

Date
and time: 22 February 2018,
15:00 h.

Venue: UCM, Faculty of Physical Sciences,
Theoretical Physics I Dept., seminar room (3rd floor)