Guillermo Franco Abellán

Cosmologist | Postdoctoral researcher at IFIC, University of Valencia

Portrait of Guillermo Franco Abellán

I'm Guillermo, and I work as a theoretical physicist specialized in cosmology. I am a postdoc at the Institute of Corpuscular Physics (IFIC), in the University of Valencia. Before this, I was a postdoc at GRAPPA, the Center of excellence for Gravitation and Astroparticle Physics at the University of Amsterdam. Prior to that, I completed my PhD in Physics at the Laboratoire Univers et Particules de Montpellier (LUPM), under the supervision of Vivian Poulin and Julien Lavalle. I am an active member of the Euclid Consortium.

As a researcher, I work on bridging the gap between theory and observations, with special interest in using cosmological observables to learn about the dark components of the universe. Specifically, I have spent a large part of my time thinking about cosmic tensions and their implications for new physics. In recent years, I've also become interested in the use of machine learning techniques to optimize statistical inference in cosmology. In particular, I'm focusing on modern approaches in simulation-based inference, a framework that allows us to perform inference in problems where traditional methods are computationally prohibitive or simply intractable. These methods will be essential to efficiently explore the vast array of dark sector theories from next-generation surveys.

The following word cloud gives a snapshot of my main research themes.

Simulation-Based Inference Decaying Dark Matter Neutrino Cosmology Euclid Deep Learning Cosmic IC Reconstruction Cosmic Neutrino Background Cosmic Tensions Statistical Methods CMB Early Dark Energy Boltzmann Solvers Modified Gravity Large-Scale Structure Cosmological Perturbations Ultra-Compact Minihalos Gravitational Waves Interacting Dark Radiation Primordial Black Holes Emulators Exotic Energy Injection

Outside of research, I enjoy watching films, trying out new recipes, and spending quality time with friends. On my Letterboxd profile you can find a list of my most recently watched movies.

Publications

Below you can find a list of all my publications, automatically generated from my INSPIRE-HEP profile.

Number of papers: 23 h-index: 14 Citations: 3710
2026
Cosmology in the Einstein Telescope era: comparing traditional and simulation-based methods for population inference
G. Antinozzi, G. Franco Abellán, D. Sciotti, M. Martinelli
arXiv:2608.04005 0 citations
astro-ph.CO astro-ph.IM gr-qc
Neutrino decays as a natural explanation of the neutrino mass tension
G. Franco Abellán
PRD arXiv:2601.04312 7 citations
astro-ph.CO hep-ph hep-th
2025
Impact of neutrino decays on the Cosmic Neutrino Background anisotropies
N. Terzaghi, G. Franco Abellán, F. Zimmer, S. Ando
arXiv:2510.15818 2 citations
astro-ph.CO hep-ph
Euclid preparation. XCVIII. Cosmology Likelihood for Observables in Euclid (CLOE). 5: Extensions beyond the standard modelling of theoretical probes and systematic effects
L. Goh, A. Nouri-Zonoz, S. Pamuk, et al. (303 authors)
arXiv:2510.09147 2 citations
astro-ph.CO
How to embed any likelihood into simulation-based inference: Application to Planck and stage IV galaxy surveys and dynamical dark energy
G. Franco Abellán, N. Anau Montel, O. Savchenko, C. Weniger
PRD arXiv:2507.22990 6 citations
astro-ph.CO astro-ph.IM
The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
E. Di Valentino, J. Levi Said, A. Riess, et al. (543 authors)
astro-ph.CO gr-qc hep-ph
Fast Gaussian marginal neural posterior estimation of cosmological initial conditions
O. Savchenko, G. Franco Abellán, F. List, N. Anau Montel, C. Weniger
MNRAS arXiv:2502.03139 9 citations
astro-ph.CO astro-ph.IM cs.LG
2024
Mean-Field Simulation-Based Inference for Cosmological Initial Conditions
O. Savchenko, F. List, G. Franco Abellán, N. Anau Montel, C. Weniger
astro-ph.CO astro-ph.IM cs.LG
Effects of primordial fluctuations on relic neutrino simulations
F. Zimmer, G. Franco Abellán, S. Ando
JCAP arXiv:2407.14582 9 citations
astro-ph.CO hep-ph
Fast likelihood-free inference in the LSS Stage IV era
G. Franco Abellán, G. C. Herrera, M. Martinelli, O. Savchenko, D. Sciotti, C. Weniger
JCAP arXiv:2403.14750 16 citations
astro-ph.CO astro-ph.IM
2023
Probing early modification of gravity with Planck, ACT and SPT
G. Franco Abellán, M. Braglia, M. Ballardini, F. Finelli, V. Poulin
JCAP arXiv:2308.12345 35 citations
astro-ph.CO gr-qc
Comparative analysis of interacting stepped dark radiation
N. Schöneberg, G. Franco Abellán, T. Simon, A. Bartlett, Y. Patel, T. L. Smith
PRD arXiv:2306.12469 42 citations
astro-ph.CO hep-ph
Minihalos as probes of the inflationary spectrum: accurate boost factor calculation and new CMB constraints
G. Franco Abellán, G. Facchinetti
JCAP arXiv:2304.02996 12 citations
astro-ph.CO gr-qc hep-ph
2022
Searching for new physics with CMB precision cosmology
G. Franco Abellán
PhD thesis 0 citations
A step in the right direction? Analyzing the Wess Zumino Dark Radiation solution to the Hubble tension
N. Schöneberg, G. Franco Abellán
JCAP arXiv:2206.11276 54 citations
astro-ph.CO hep-ph
The QCD phase transition behind a PBH origin of LIGO/Virgo events?
J. I. Juan, P. D. Serpico, G. Franco Abellán
JCAP arXiv:2204.07027 32 citations
astro-ph.CO
Constraining decaying dark matter with BOSS data and the effective field theory of large-scale structures
T. Simon, G. Franco Abellán, P. Du, V. Poulin, Y. Tsai
PRD arXiv:2203.07440 85 citations
astro-ph.CO hep-ph
Cosmology intertwined: A review of the particle physics, astrophysics, and cosmology associated with the cosmological tensions and anomalies
E. Abdalla, G. Franco Abellán, A. Aboubrahim, et al. (203 authors)
JHEAp arXiv:2203.06142 1598 citations
astro-ph.CO hep-ph
Hints of early dark energy in Planck, SPT, and ACT data: New physics or systematics?
T. L. Smith, M. Lucca, V. Poulin, G. Franco Abellán, L. Balkenhol, K. Benabed, S. Galli, R. Murgia
PRD arXiv:2202.09379 125 citations
astro-ph.CO hep-ph
2021
Improved cosmological constraints on the neutrino mass and lifetime
G. Franco Abellán, Z. Chacko, A. Dev, P. Du, V. Poulin, Y. Tsai
JHEP arXiv:2112.13862 73 citations
hep-ph astro-ph.CO
The H0 Olympics: A fair ranking of proposed models
N. Schöneberg, G. Franco Abellán, A. Pérez Sánchez, S. J. Witte, V. Poulin, J. Lesgourgues
astro-ph.CO hep-ph hep-th
Linear cosmological constraints on two-body decaying dark matter scenarios and the S8 tension
G. Franco Abellán, R. Murgia, V. Poulin
PRD arXiv:2102.12498 91 citations
astro-ph.CO hep-ph
2020
Early dark energy resolution to the Hubble tension in light of weak lensing surveys and lensing anomalies
R. Murgia, G. Franco Abellán, V. Poulin
PRD arXiv:2009.10733 157 citations
astro-ph.CO hep-ph
Implications of the S8 tension for decaying dark matter with warm decay products
G. Franco Abellán, R. Murgia, V. Poulin, J. Lavalle
PRD arXiv:2008.09615 94 citations
astro-ph.CO hep-ph

Seminars

I have given over 30 conference talks and seminars at various institutions. Below you can find a selection of my presentations, including slides.

2026
Invited talk
Sheffield, England — Jun 22–26, 2026
Splinter Talk
Barcelona, Spain — May 26–29, 2026
2025
Invited talk
Nijmegen, The Netherlands — Jul 1–2, 2025
Contributed talk
Cagliari, Italy — Jun 16–20, 2025
Seminar
Prague, Czech Republic — May 21, 2025
2024
Contributed talk
Kyoto, Japan — Oct 21–25, 2024
Invited talk
Île de Noirmoutier, France — Jun 2–7, 2024
Webinar
Euclid Theory Working Group (WP17) informal meeting
Apr 26, 2024
Seminar
Centre de Physique Théorique
Marseille, France — Jan 12, 2024
2023
Contributed talk
Paris, France — Oct 10–12, 2023
Seminar
Université Libre de Bruxelles
Brussels, Belgium — Jun 8, 2023
Contributed talk
Geneva @ CERN, Switzerland — May 31–Jun 2, 2023
Contributed talk
Avignon, France — May 2–5, 2023
Webinar
Instituto de Astrofísica de Canarias
Tenerife, Spain — Mar 24, 2023
2022
Webinar
Physics Reports Seminar Series
Nov 14, 2022
Webinar
University of the Western Cape
Cape Town, South Africa — Sep 16, 2022
Invited talk
Sesto, Italy — Jul 25–29, 2022
Seminar
Laboratoire de Physique des 2 Infinis Irène Joliot-Curie, IJCLab
Orsay, France — Jun 20, 2022
Contributed talk
Montpellier, France — Jun 15–17, 2022
Contributed talk
La Thuile, Italy — Jan 23–30, 2022
2021
Webinar
Garching, Germany — Dec 7, 2021
Seminar
Stony Brook University
Long Island, US — Nov 22, 2021
Seminar
University of Maryland
Washington D.C., US — Nov 18, 2021
Seminar
Johns Hopkins University
Baltimore, US — Nov 15, 2021
Seminar
SISSA
Trieste, Italy — Nov 4, 2021
Webinar
Barcelona, Spain — Oct 25, 2021
Seminar
Instituto de Física Teórica
Madrid, Spain — Oct 21, 2021

Codes

I am a strong advocate of open science. All the software and tools I've built are in public GitHub repositories. Below you can find some of them.

SBI tools

In recent years I've focused on building new packages and methods in simulation-based inference (SBI), allowing to efficiently extract cosmological parameters from different observations.

Sireeni

A SBI package to reconstruct cosmological and astrophysical parameters from Einstein Telescope GW catalogs.

SBI-aux-obs

Auxiliary-observable trick to build an effective SBI simulator from any explicit likelihood, illustrated on Planck 2018 data.

Swyft-LSS

A SBI code to perform cosmological forecasts from Stage IV photometric galaxy surveys like Euclid.

CLASS modifications

I've also spent a lot of time building new versions of the public Boltzmann solver CLASS, enabling the computation of cosmological observables for various exotic scenarios.

CLASSpp_nuDecay

A CLASS version to model the effects of late-time neutrino decays into dark radiation and lighter neutrinos.

ExoCLASS

An ExoCLASS extension for testing exotic energy injection from: 1) DM annihilations in ultra-compact mini-halos, and 2) accreting PBHs with extended mass functions.

class_clumpy

A CLASS version for placing constraints on small-scale baryon clumping.

Contact

Feel free to get in touch, I'm always happy to talk about science and explore new collaborations.

Office

510, IATA building

IFIC, CSIC – Universitat de València

Parc Científic UV, c/ Catedrático José Beltrán 2

E-46980 Paterna (València), Spain