The cosmology group at the Instituto de Física Teórica (IFT UAM–CSIC) explores the fundamental physics governing the origin, structure and evolution of the Universe. By combining theoretical modeling with the interpretation of cosmological observations, the group seeks to understand how the largest scales of the Universe can reveal new insights about gravity, particle physics, and the earliest moments after the Big Bang. The research program spans a broad range of topics, from the physics of the primordial Universe to the large-scale properties of spacetime itself.
The Physics of the Early Universe
One of the central research directions of the group concerns the earliest phases of cosmic history. A leading paradigm for describing this period is cosmic inflation, a short phase of accelerated expansion believed to have occurred a fraction of a second after the Big Bang. Inflation provides a compelling explanation for the remarkable uniformity of the Universe and for the tiny fluctuations that later grew into galaxies and cosmic structure.
Researchers at the IFT develop theoretical models of inflation motivated by high-energy physics and explore their observable consequences. These studies include the statistical properties of primordial fluctuations, the generation of gravitational waves during the inflationary era, and the possible formation of relics such as primordial black holes that constitute a significant fraction of the dark matter in the Universe. Because inflation may have occurred at energy scales far beyond those accessible in laboratory experiments, cosmology provides a unique opportunity to probe fundamental physics under extreme conditions.
Gravitational Waves
While most of the gravitational waves detected so far may have originated from astrophysical sources such as merging black holes and neutron stars, many cosmological models predict a stochastic background of gravitational waves produced in the early Universe, as well as primordial black holes formed in clusters during the radiation era that generate binaries that merge today.
Members of the group investigate theoretical mechanisms that could generate such signals, including inflation, phase transitions in the primordial plasma, and other processes predicted by extensions of the Standard Model of particle physics. Detecting a stochastic gravitational-wave background would provide a powerful probe of physics at very high energies and could reveal information about events that took place in the first moments of cosmic history.
Dark Energy and the Nature of Gravity
Observations over the past two decades have shown that the expansion of the Universe is accelerating. Understanding the origin of this acceleration is one of the most important challenges in modern cosmology. It may be driven by a mysterious component known as dark energy, or it could signal that gravity behaves differently on cosmological scales than predicted by Einstein’s theory of general relativity.
The IFT cosmology group studies theoretical models of dark energy and modified gravity, exploring how different scenarios affect the expansion of the Universe and the growth of cosmic structures. These models can be tested through their observable signatures in the cosmic microwave background, galaxy clustering, and gravitational lensing. By confronting theory with observations, researchers aim to determine whether cosmic acceleration is due to new forms of energy/entropy or to a deeper modification of gravitational physics on the largest scales.
Of particular importance in this area are the synergies with Stage-IV galaxy surveys, such as Euclid, DESI and LSST, in which members of the group actively lead several projects.
The Topology and Global Structure of the Universe
Beyond understanding the contents of the Universe, cosmologists also ask a more fundamental question: what is the global shape of space itself? While cosmological observations show that space is nearly geometrically flat, this does not uniquely determine its topology. Space may extend infinitely, or it may be finite but connected in non-trivial ways, such that traveling far enough in one direction could in principle bring you back to your starting point.
Research in cosmic topology investigates these possibilities by studying how different global geometries would affect cosmological observables. For example, certain topologies could leave distinctive imprints in the cosmic microwave background or lead to repeating patterns in the distribution of matter across the Universe. Detecting such signatures would reveal that the Universe has a finite but non-trivial structure, providing a fundamentally new perspective on cosmic space. Current theoretical work explores the mathematical classification of possible topologies and develops methods to identify their observational consequences. 
Connecting Fundamental Physics and the Cosmos
A defining feature of the cosmology program at the IFT is the strong connection between fundamental theory and observational cosmology. By developing new theoretical frameworks and identifying measurable signatures, researchers aim to use the Universe itself as a laboratory for testing the laws of physics.
Through collaborations with international experiments and cosmological surveys, such as Euclid, the group contributes to the global effort to uncover the origin of cosmic structure, the nature of dark energy and gravity, and the fundamental properties of spacetime.
Machine Learning (ML) and Artificial Intelligence (AI)
Members of the group are leading the use of techniques aiming to speed-up the analyses of LSS and GW data. Specifically, current Stage-IV galaxy surveys, such as Euclid and DESI, are already producing exquisite data, albeit at vast quantities and necessitate the use of high-dimensional likelihoods. These make the use of traditional Monte Carlo analyses inefficient, thus requiring novel techniques using ML-AI approaches (emulators, SBI, NNs etc).
However, of great importance is also to understand what the AI is doing, thus members of the group have developed techniques based on Interpretability, aiming enhance the extraction of meaningful information from cosmological large-scale structure data.