Research Interests

My research interests are broad in the field of Astrophysics and Cosmology and change from time to time depending on developments in the field. I do avoid following fashions and tend to do research on what purely interest my intellect. I will work on whatever I think will be the most effective tool to understand the nature of the Universe. I chose cosmology as my research field as I find it the most exciting, data-rich and promising area of human knowledge to unveil the fundamental laws of nature. Another aspect of my research has been my continuous interest in rigorous statistics and, in particular, Bayesian inference to understand data and how, we humans, infer facts about nature.

SCIENTIFIC ACHIEVEMENTS

The list below sumarizes the main findings about nature I have made during my scientific career. The number in parenthesis corresponds to the article number in the CV publication list:

The Age of the Universe and Cosmological Parameters: The first accurate and precise constraint on the age of the Universe using globular clusters (13.5 Gyr, published in 1995); among the first indications for a cosmological constant using the ages of high-z galaxies and the ages of globular clusters (4, 7, 8, 12, 17). The first reliable and accurate estimate of the ages of high-z galaxies (6, 15, 18). The first accurate constraints on the age of Milky Way disk (20). A new method to directly measure the expansion history of the metric of space time via cosmic chronometers: the cosmic chronometer method (39, 59). I was the first one to introduce the term “tension" and quantify it regarding the mismatch at high and low-redshift of the H0 (137, 140, 148). A demonstration of the accuracy of the cosmic chronometer method to compute cosmology parameters (158, 159, 171, 177). A new precise and accurate measurement of the age of the universe at the % level (173, 183, 187, 205, 206, 207). A method to measure H0 from neutrino oscillations (196). A model to explain how minuscule black holes formed during inflation that produce gravitons can remove the Hubble tension (202).

Stellar Populations: The solution of the long standing inverse problem of deriving physical quantities from the integrated light of stellar populations via the MOPED and VESPA algorithms (34, 76). The determination of the ages, metallicities and star formation histories of galaxies from their integrated spectrum using MOPED and VESPA (53, 56, 57, 74, 86).

Stars and the Interstellar Medium: An accurate measurement of the primordial He abundance (46, 78). The first theoretical prediction that the magnetic field in molecular clouds is low (52). The discovery of the nature of Supernova type-Ia progenitors (87, 103). The role of GRBs in life survival in the universe; a lower bound to the value of the cosmological constant (155). A quantitative demonstration of the effect that giant planets can have in biasing the cosmic ladder (182).

Galaxy Formation and Evolution: Among the first parameter-free models for the formation of GCs in the LCDM paradigm (13, 153). The prediction, and later confirmation, of the existence of dark galaxies (16, 40, 178). The prediction of the existence of high-z (z > 3) massive elliptical galaxies (24). The observational demonstration of the existence of primordial gas at low redshift (z ∼ 3) (64). How to perform tomography of the re-ionization epoch (69, 72, 79). A theoretical model for the formation of the first galaxies (141, 143). The theoretical discovery of how galaxies obtain their spin in the hierarchical model of structure via the cosmic web (152). The finding that there are no missing low-mass galaxies in a cosmological volume of 1 Gpc3 (169).

Large Scale Structure: The first accurate analytical calculation of the non-gaussian mass function of collapsed structures (27). The first hints from the abundance of rare objects of primordial non-gaussian fluctuations (96). The development of analytic methods to compute the large scale structure of the universe (104, 115, 138,144). The development of accurate and exact tools to analyze weak lensing cosmological studies (154, 157, 166). A method to measure in a cosmology-model independent way the standard ruler of the Universe (162).

Neutrino Cosmology: The measurement of neutrino masses and their hierarchy from cosmology (97, 127, 161, 163, 165). A new method to distinguish Dirac from Majorana neutrinos using astronomical observations (197, 204).

Dark Energy Theory: A dynamical origin to explain the nature of dark energy as a source of momentum exchange with neutrinos (168, 184). Some of the strongest constraints on modifications of gravity, putting these theories under pressure (142, 151, 156, 159, 163, 175, 185).

Dark Matter: The first precise computation of annihilation and profile spikeness of dark matter halo profiles (38). A method to detect the existence of axions from astronomical observations (117, 126). A quantitative demonstration that the existence of dwarf galaxies without dark matter implies that dark matter can only be cold CDM (183).

Early Universe and Theoretical Cosmology (The Quantum Nature of the Universe): An inflation model from pure (super-)symmetry considerations (101,110, 125). The best model independent constraint on the amount of different types of energy densities in the early Universe: no room for early dark energy (164). A method to measure deviations from Einstein gravity at the Planck scale using non-gaussian observations of the CMB (170). A new method to test the early Universe via measurements of the graviton exchange during inflation using the non-gaussian halo power–spectrum (172). A new method to measure the Homogeneity of the Universe for any general metric and independently on the cosmological model: a way to see inside the past light-cone (174). A method to constraint the global curvature of the Universe independent of the cosmology model (167). A new approach based entirely on quantum mechanics to describe the early Universe, including a robust prediction that the tensor-to-scalar ratio must be 0.01 (176, 179, 180). A model independent method to describe quasi de Sitter as a pure non-perturbative quantum gravity phenomenon on exact de Sitter as a result of the quantum phases as described by the quantum Fisher (185, 186, 188, 189, 190, 192, 195). A new insight of why the Universe is exactly spacially flat (201).

Statistics and Inference: The invention of the data compression algorithm MOPED(28). The novel use of machine learning (Gaussian process) to quantify the expansiuon history of the Universe (148). The development of rigorous statistical methods to analyse astronomical observations and reduce the effect of systematic errors (120). A new parameterisation of the cosmic microwave background that opened the door to fast cosmological parameter estimation (43). A theoretical method to better design CMB polarization experiments (63).

Holography, Gravitational Waves and the Early Universe: I have developed a new approach to study singularities.

Computational methods: I have developed new algorithms in the field of machine learning to solve partial differential equations (PINNs).

AI, Robotization and Society: I have written two books on the impact of robotization and AI on society and democracy as well as numerous articles (246-278) on the same subject.