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). I have
extended the age-dating technique to local and high-redshift globular clusters (212, 213).
Stellar Populations: The solution of the long standing inverse problem of deriving physical quantities from the in-
tegrated 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 cos-
mological 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 struc-
tures (27). The first hints from the abundance of rare objects of primordial non-gaussian fluctuations (96). The devel-
opment 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, 207) and new
predictions on the shape of neutrino profiles (209). I have also made the first accurate predictions on how the cross-
correlatiosn of the cosmic neutrino background look like (215). I have also developed a novel method to measure the
cosmic neutrino background using celestial objects (217).
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). I have also developed a new picture to observationally test the
quantum nature of the Universe (216,224) and a new theory in which the scalar perturbations of the Universe is generated
from quantum fluctuations of space-time (211,220).
Statistics and Inference: The invention of the data compression algorithm MOPED(28) and VESPA(79) . The de-
velopment of rigorous statistical methods to analyse astronomical observations and reduce the effect of systematic errors
(120). A new parameterization 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
and strongly coupled field theories to understand also phase transitions in the early Universe as well as the state of matter
in neutron stars collisions (208).
Computational methods: I have developed new algorithms in the field of machine learning to solve differential equa-
tions (PINNs). In particular, I have found new schemes to facilitate the search for solutions in NN with ultra-complex
morphology that contains multiple maxima/minima and inflection points. This has wide ranging applications in the field
of ML (213). I have published a textbook on the subject (4, 5).
AI, Robotization and Society: I have written two books on the impact of robotization and AI on society and democ-
racy as well as numerous articles (246-278) on the same subject.
Complexity: I have developed new methods to understand complexity, In particular how to characterized the solution
space of non-linear PDEs. This is done in the context of both astrophysical phenomena, game theory and language
models. In particular: a new method to analyze and classify the solutions of highly complex PDEs like Navier-Stokes
(229) or stochastic partial differential equations (230).