LUIS ENRIQUE PADILLA ALBORES / THEORETICAL COSMOLOGIST

Researcher inearly-Universe
physics

I study the physics between the end of inflation and Big Bang nucleosynthesis, focusing on primordial black holes and gravitational waves.

I combine theoretical models, numerical relativity and statistical methods to investigate gravitational collapse, PBH formation and possible observational signatures.

Research areas Download CV
JSPS International Postdoctoral Fellow
Rikkyo University, Tokyo · with Prof. Tomohiro Harada
Luis E. Padilla, wearing glasses and a dark shirt, in a candid photograph.
22Peer-reviewed journal publications
2025–27JSPS International Fellowship
3 countriesPostdoctoral research: MX · UK · JP
Google Scholar
01 / RESEARCH OVERVIEW

RESEARCH FOCUS

From the end of inflation
to nucleosynthesis

The period between the end of inflation and Big Bang nucleosynthesis (BBN) is not well constrained. The Universe may have experienced prolonged reheating, an early matter-dominated era or kination. Different expansion histories and matter components affect the evolution of primordial fluctuations and the conditions for black-hole formation.

My research studies how these physical conditions affect primordial-black-hole (PBH) formation and gravitational-wave (GW) production. I use analytical models and numerical relativity to study individual collapse events, then investigate how their properties enter cosmological predictions for PBH populations and GW backgrounds.

02 / RESEARCH BACKGROUND

Research trajectory

My work has developed from scalar-field dark matter and reheating to numerical simulations of gravitational collapse and PBH mass distributions.

01 ↘

Scalar-field models

During my PhD I studied scalar-field dark matter, compact cores and the relation between field dynamics and effective fluid descriptions.

CINVESTAV · PhD
02 ↘

Reheating and PBHs

At UNAM I studied PBH formation through inflaton structures and constraints from PBH abundances and induced gravitational waves.

UNAM · POSTDOC
03 ↘

Numerical relativity

At Queen Mary I derived and implemented the core of a relativistic scalar-field–fluid evolution solver to examine nonlinear collapse.

QUEEN MARY · POSTDOC
04 ↗

Critical collapse

At Rikkyo I study critical mass scaling, discrete self-similarity and their effects on PBH mass functions.

RIKKYO · JSPS FELLOW

03 / RESEARCH AREAS

Research areas

My research combines early-Universe models, numerical simulations of nonlinear gravity, and predictions for PBHs and gravitational waves.

01 / CRITICAL COLLAPSE

Critical gravitational collapse & discrete self-similarity

How universal are the critical exponents and other features of gravitational collapse, and which of them survive in PBH observables? I use numerical relativity to investigate critical mass scaling, discrete self-similarity (DSS) and their possible imprints on PBH mass distributions.

NUMERICAL RELATIVITYKINATIONDSS
Read the PRD Letter
02 / REHEATING

Reheating, scalar fields & primordial structure

If reheating lasts sufficiently long, primordial fluctuations may grow into inflaton halos and compact scalar-field cores. I investigate how these structures form and evolve, and how interactions, accretion and possible collapse into PBHs could help constrain the duration and physical conditions of reheating.

REHEATINGINFLATON STRUCTURE
Explore the mechanism
03 / PBHS AND GWS

PBH populations & gravitational-wave backgrounds

How can PBH abundances, mass distributions and stochastic gravitational-wave backgrounds help distinguish different scenarios for the early Universe? I study their dependence on primordial fluctuations, expansion history and nonlinear collapse, including how to separate features produced at formation from those inherited from the initial conditions.

PBH STATISTICSINDUCED GWS
Explore the GW connection
04 / PARTICLE PHYSICS

Metastable fields, Higgs-like potentials & spacetime

What happens when a spectator field crosses a metastable barrier? Our nonlinear simulations uncover distinct black-hole-forming branches. The connection to the physical Standard Model Higgs remains an important open question.

VACUUM INSTABILITYSTRONG GRAVITY
Read the preprint

04 / SELECTED RESULTS

Selected research results

A few representative results from published work, with links to the corresponding papers.

01 / 2026
CRITICAL COLLAPSE

Discrete self-similarity in cosmological PBH formation

We demonstrated the characteristic log-periodic fine structure of near-critical scalar-field PBH formation during kination. I am now investigating how those signatures depend on initial conditions and propagate into population statistics.

PRD Letter ↗Mass functions · preprint ↗
02 / 2025–26
NUMERICAL RELATIVITY

Relativistic simulations of scalar-field collapse

I derived and implemented the core evolution solver for coupled Einstein–scalar-field–fluid simulations, helping establish when effective-fluid treatments capture nonlinear collapse and when field dynamics change the outcome.

Numerical framework ↗Critical nature of collapse ↗
03 / 2022–24
REHEATING & GWS

PBH formation and induced gravitational waves during reheating

My work explored PBH formation through the growth and instability of inflaton structures and investigated how PBH abundances and induced gravitational waves can jointly constrain slow-reheating scenarios.

PBH mechanism ↗Induced GWs ↗

05 / CURRENT AND FUTURE WORK

Current and future projects

Research questions I am currently pursuing or plan to investigate.

01

DSS signatures in PBH populations

Test whether DSS modulations survive profile mixing, astrophysical evolution and observational selection in PBH searches.

02

PBHs and GWs during reheating

Combine inflaton structure growth, accretion and collapse with gravitational-wave predictions to probe post-inflationary history.

03

Higgs-like field instability

Extend metastable-field simulations towards physically motivated Higgs potentials and related early-Universe scenarios.

04

Numerical simulations and PBH statistics

Develop reliable, physics-informed surrogates for collapse thresholds and mass relations, grounded in relativistic simulations.

06 / ACADEMIC BACKGROUND

Academic background

I have worked in Mexico, the United Kingdom and Japan, collaborating on theoretical cosmology, numerical relativity and gravitational-wave physics.

My path

I trained in physics at the Universidad de Guadalajara and completed a PhD at CINVESTAV–IPN in Mexico in 2020, advised by Tonatiuh Matos. During my doctorate I spent six months at UT Austin working with Paul Shapiro and Tanja Rindler-Daller.

I then worked at UNAM with Juan Carlos Hidalgo, at Queen Mary University of London with David Mulryne and Karim Malik, and now at Rikkyo University in Tokyo with Tomohiro Harada. Each step broadened the tools and physical questions I could tackle.

I also teach and mentor students, develop numerical tools and collaborate on problems in cosmology, gravitation and high-energy theory.

Explore my full CV
2025—NOW

Rikkyo University
JSPS International Postdoctoral Fellow · Japan

2024—2025

Queen Mary University of London
Postdoctoral Researcher · United Kingdom

2020—2023

Instituto de Ciencias Físicas, UNAM
Postdoctoral Researcher · Mexico

2020

CINVESTAV–IPN
PhD in Physics · Mexico

2014

Universidad de Guadalajara
BSc in Physics · Mexico

Mentoring & teaching

I formally advised five diploma-level research students at MCTP–UNACH and have contributed to the informal research guidance of students from undergraduate to PhD level. I've taught cosmology, quantum mechanics, statistical physics and topics in PBHs.

Numerical tools

I develop and apply an extended Misner–Sharp scalar-field–fluid solver, including strong-gravity diagnostics and HPC workflows. The code is not yet publicly released. I'm also a contributor to PBH-β ↗.

Academic service

Member of the local organizing committee for Dynamics of Primordial Black Hole Formation III (2026), and referee for Physical Review Letters, Physical Review D and JCAP.

07 / FELLOWSHIPS & RECOGNITION

Fellowships & recognition

Competitive fellowships, funded research appointments, and selected postdoctoral offers. Awarded support and declined offers are listed separately; further details are in my CV.

Fellowships & research support

2025–2027

JSPS International Postdoctoral Fellowship

Japan Society for the Promotion of Science · Rikkyo University, Japan. Includes associated KAKENHI research support for JSPS Fellows.

2024–2025

Royal Society–supported research appointment

Queen Mary University of London, UK · Postdoctoral position funded through the host research group’s Royal Society University Research Fellowship.

2021–2023

DGAPA–UNAM Postdoctoral Fellowship

Instituto de Ciencias Físicas, UNAM · Mexico

2020–2021

CONACyT-supported postdoctoral appointment

Instituto de Ciencias Físicas, UNAM · Mexico. Supported by research grant CB-2016-282569.

2018–2019

CONACyT scholarship for overseas research

Research visit to the University of Texas at Austin · USA

2014–2019

CONACyT PhD Scholarship

Doctoral studies at CINVESTAV–IPN · Mexico

Selected postdoctoral offers (declined)

2025

University of Science and Technology of China (USTC)

Postdoctoral offer in theoretical cosmology · China. Declined after accepting the JSPS fellowship at Rikkyo University.

2024

Instituto de Física, UNAM

CONACyT postdoctoral offer · Mexico. Declined after accepting the position at Queen Mary University of London.

2021

University of Aveiro

Postdoctoral offer in numerical relativity and scalar-field dynamics · Portugal. Declined in favour of the DGAPA–UNAM fellowship.

Recognition

2022–2025

Sistema Nacional de Investigadores (SNI)

Candidate level · Mexico

MSCA PF

Seal of Excellence

Marie Skłodowska-Curie Postdoctoral Fellowship proposal · score 89.4/100; funding not awarded

08 / PUBLICATIONS

Selected publications

A selection spanning critical collapse, reheating, gravitational waves and scalar-field cosmology. Full and evolving records are available on INSPIRE and Google Scholar.

2026 PRD LETTERCosmological discrete self-similarity in primordial black hole formationL. E. Padilla, T. Harada, E. Milligan, D. Mulryne 2026 PREPRINTDiscrete self-similarity imprints on primordial-black-hole mass functionsL. E. Padilla, T. Harada, H. Iizuka 2026 JCAPPrimordial Black Hole Formation in a Scalar Field Dominated Universe: Investigation of the Critical Nature of the CollapseL. E. Padilla, E. Milligan, D. Mulryne, J. C. Hidalgo 2026 PREPRINTBlack holes from a Higgs-like field in the radiation eraE. Milligan, L. E. Padilla, D. Mulryne 2024 JCAPDetecting the Stochastic Gravitational Wave Background from Primordial Black Holes in Slow-reheating ScenariosL. E. Padilla, J. C. Hidalgo, K. A. Malik, D. Mulryne 2022 PRDNew mechanism for primordial black hole formation during reheatingL. E. Padilla, J. C. Hidalgo, K. A. Malik 2021 PRDCore-Halo Mass Relation in Scalar Field Dark Matter Models and its Consequences for the Formation of Supermassive Black HolesL. E. Padilla, T. Rindler-Daller, P. R. Shapiro, T. Matos, A. Vázquez
22 peer-reviewed articles listed in CV dated 30 October 2026, plus public preprints.View complete publication list

09 / CONTACT

Contact

I welcome collaborations, seminar invitations and inquiries from students interested in early-Universe cosmology, primordial black holes, numerical relativity and gravitational waves.

lepadilla@rikkyo.ac.jp
FIND ME ELSEWHEREINSPIRE-HEP Google Scholar LinkedIn Academic CV TOKYO, JAPAN