2026
Javier Rubio
Particle Cosmologist · Ramón y Cajal Researcher · Universidad Complutense de Madrid
Exploring how fundamental physics shaped the Universe — from inflation and reheating to phase transitions, dark matter and gravitational waves.
ABOUT
From fundamental physics to the cosmos
I am a theoretical physicist working at the interface of particle physics and cosmology. Since 2022, I have been a Ramón y Cajal Researcher at the Department of Theoretical Physics of the Universidad Complutense de Madrid and a member of the Institute of Particle and Cosmos Physics (IPARCOS).
My research asks how physics at energies far beyond the reach of terrestrial experiments may have shaped the history of the Universe — and what observable traces those processes could have left behind.
Before moving to Madrid, I held research positions at CENTRA–Instituto Superior Técnico, the Helsinki Institute of Physics, Heidelberg University and EPFL. I obtained my Master’s and Ph.D. degrees from the Universidad Autónoma de Madrid.
RESEARCH
What I work on
I am interested in situations where particle physics, gravity and cosmology become inseparable, particularly in the early Universe.
01
Inflation & Reheating
The physics of the inflationary Universe and the nonlinear dynamics that connected it to the hot Big Bang.
02Vacuum Stability
The fate of the electroweak vacuum in the early Universe and its interplay with gravity and high-energy physics.
03Phase Transitions & Gravitational Waves
Violent cosmological phenomena and the gravitational-wave backgrounds they can generate.
04Dark Sector & Symmetries
Dark matter, dark energy and the role of scale invariance in connecting physics across widely separated energy scales.
LATEST RESEARCH
Recent publications
A selection of my most recent work in particle cosmology and fundamental physics.
CURRENT PROJECTS
Research in progress
Cosmic Equilibrium
Probing Higgs Instability with Gravitational Waves
Exploring the cosmological implications of Higgs vacuum instability and its possible gravitational-wave signatures.
Project details ↗
Construyendo el Universo
De la Inflación Cosmológica a la Materia Oscura
Connecting early-Universe dynamics, particle physics and the origin of the cosmological dark sector.
Project details ↗
ACADEMIC LIFE
Teaching & supervision
TEACHING
Teaching physics
Lecture notes and teaching materials in quantum physics, cosmology, gravitation and mathematical methods.
Explore teaching →
SUPERVISION
Working with students
PhD, MSc and undergraduate research projects in particle cosmology and fundamental physics.
Students & opportunities →
BEYOND RESEARCH
Physics beyond academia
I enjoy teaching, working with students and finding clear ways of explaining difficult ideas. I also take part in public engagement activities aimed at bringing modern cosmology and fundamental physics to a broader audience.