Strong Gravity

The group's research on strong gravity involves finding analytical and numerical solutions of Einstein's theory of general relativity, and many of its extensions, either in vacuum or coupled to various types of matter. For our latest developments/activities in this area, please see the listing at the end of this article.

The prime examples of (relativistic) strong gravitational systems are Black Holes. They are truly unifying objects of all physics. The understanding of their formation and dynamics requires the laws of all four fundamental forces, and their physics is relevant not only for astrophysics and cosmology but for a variety of topics within high energy physics.

See here a movie made by the COST action `Black holes in a violent universe', in which our group participates, for a visual overview of different types of black holes.

Latest Strong Gravity Publications

Phantom scalar field with arbitrary potential: accelerating scaling attractors, S. Halder, S. Pan, P. M. Sá, T. Saha; arXiv:2510.17765 [gr-qc].

Publication type
Regular Articles
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Gravitational waves from two scalar fields unifying the dark sector with inflation, O. Luongo, T. Mengoni, P. M. Sá; arXiv:2509.21200 [gr-qc]

Publication type
Regular Articles
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Splitting the Gravitational Atom: Instabilities of Black Holes with Synchronized/Resonant Hair, J. Nicoules, J. Ferreira, C. A. R. Herdeiro, E. Radu, M. Zilhão; arXiv:2509.20450 [gr-qc].

Publication type
Regular Articles
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Phase transitions of boson stars in scalar-tensor theories, H. Huang, B. Kleihaus, J. Kunz, Meng-Yun Lai, E. Radu, De-Cheng Zou; arXiv:2509.05202 [gr-qc]

Publication type
Regular Articles
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Horizon-scale variability of from 2017--2021 EHT observations, The Event Horizon Telescope Collaboration (w/ H. R. O. Sánchez); Accepted for publication in Astron. Astrophys., arXiv:2509.24593 [astro-ph.HE]

Publication type
Regular Articles
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See Strong Gravity publications

Latest Strong Gravity News & Events

Photon rings and shadows of Kerr black holes immersed in a swirling universe

GGD - Gr@V Seminar
Speaker
Rogério Capobianco
Event date
Venue
Online
Event Website
https://teams.microsoft.com/l/meetup-join/19%3ameeting_Yjc0YTNkNjEtOTVlYi00MTg4…
Event type
Seminars

We discuss the existence and locations of light rings in the spacetime of a Kerr black hole immersed in a swirling universe– in other words, the immersion of a rotating black hole into a rotating background. As the spin-spin interaction between the black hole and the background breaks the upper-lower hemisphere symmetry, it allows for interesting new features.

Strong Gravity

New group members

members

Romain Gervalle (Ph.D. U. Tours, France, 2025) and TianXiang Ma (M.Sc, Lanzhou U., China, 2024) have joined our group in October 2025. Ana Bokulic (Ph.D. U. Zagreb, Croatia, 2024), already a group member, also renewed her group membership into 2026. Great to have you in the group!

Strong Gravity
Cosmology
High Energy Physics

Visit of João Dinis Álvares

seminars

On Oct. 22nd 2025 we had the visit of João Dinis Álvares, who completed his M.Sc. at IST-Lisbon. João gave an interesting talk on the evolution of scalar fields around black holes and also shared with us that he decided to study physics after an outreach talk by Gr@v members, in Braga, back in 2017. Thank you João, for the kind words and all the best for your Ph.D. abroad!

Strong Gravity
High Energy Physics
Astrophysics

Electrically Charged Hyperboloidal Evolution

GGD - Gr@V Seminar
Speaker
João Dinis Álvares (Instituto de Telecomunicações)
Event date
Venue
Hybrid: Sala Sousa Pinto and Teams
Event Website
Watch recording.
Event type
Seminars

We present the Einstein-Maxwell-Klein-Gordon system in hyperboloidal slices, a recent formulation for extracting signals at future null infinity. As far as we know, this is the first time this setup is evolved with a common formulation like BSSN/Z4. Using hyperboloidal slices, contrary to other recent methods like Cauchy-Characteristic Matching, we can continuously reach future null infinity.

Strong Gravity
High Energy Physics
See Strong Gravity News & Events