A proto-neutron star that keeps accreting matter is compressed until its core crosses the phase-transition line. Following this evolution with a constrained, model-agnostic ensemble of equations of state, we compute two coupled signals: a MHz burst of gravitational waves from colliding quark bubbles, and a kHz signal from the star settling onto the hybrid branch. The two are correlated, and a delayed neutrino burst would act as a timestamp for the whole event. See Ecker, Giliberti & Rezzolla, arXiv:2609.29761.
Research
First-order phase transitions in dense QCD matter and their multi-messenger signatures
I am interested in matter at the highest densities, well beyond nuclear saturation, where QCD may undergo a first-order phase transition from hadronic to quark matter. This regime cannot be reproduced on Earth: it exists in neutron-star cores, and it is crossed dynamically in proto-neutron stars and neutron-star mergers, which are therefore the laboratories where the transition can leave observable traces. Such a transition does not happen everywhere at once: it proceeds through the nucleation, expansion and collision of bubbles of the new phase, much like boiling water. I study how this process unfolds and which signals it leaves behind: gravitational waves at MHz frequencies from the bubbles themselves, kHz gravitational waves from the global response of the star, and neutrinos.
I work in the RelAstro group of Luciano Rezzolla at Goethe University Frankfurt, within the CRC-TR 211 collaboration, and I lead Frankfurt-ET, the Frankfurt Research Unit of the Einstein Telescope collaboration.
Multi-band signals from proto-neutron stars
Bubble dynamics from holography
The gravitational-wave signal of a first-order transition depends strongly on how fast the bubble walls move, a quantity that is hard to compute from first principles at strong coupling. Using holography, we performed the first microscopic simulation of bubble dynamics in a theory with a QCD-like phase diagram, measuring wall velocities across its metastable regions. See Bea et al., JHEP 04 (2026) 013.
Nucleation in neutron-star cores
Standard nucleation theory assumes a homogeneous, infinite medium, while a neutron-star core is finite and its overpressure varies with radius. I am developing a description of such inhomogeneous, overcompressed transitions in finite volume, building on the Kolmogorov–Johnson–Mehl–Avrami theory of phase-conversion kinetics.
Numerical methods
Much of my work is numerical: solving holographic and hydrodynamic problems, scanning equation-of-state ensembles, and computing gravitational-wave spectra, mostly in Julia and MATLAB on HPC systems. Some of these tools are available as packages: see the software section of my CV.
For the full and continuously updated list of publications, see the publications page.
Past research — holography and confinement
During my M.Sc. and Ph.D. in Florence I worked on the gauge/gravity duality, with a focus on confinement, screening and the phase structure of strongly-coupled gauge theories.
Model-independent tools
Most of this work relied on probes that can be defined in any holographic background:
- Wilson loops, whose quark–antiquark potential distinguishes conformal, confining and screened behavior — see Giliberti, Fatemiabhari & Nunez, JHEP 11 (2024) 068.
- Entanglement entropy via Ryu–Takayanagi surfaces, computed with numerical spline optimization, as a complementary probe of (partial) deconfinement — see Chatzis, Fatemiabhari, Giliberti & Hammond, JHEP 05 (2026) 062.
- Thermal holography: free energy, phase diagrams and the real-time dynamics of false-vacuum decay at strong coupling, the starting point of my current research on bubbles.
Top-down constructions
These tools were applied to explicit string-theory backgrounds built from wrapped branes: the holographic duals of four-dimensional N = 1 linear quiver theories, deformed by a vacuum expectation value that gaps the system. In my M.Sc. thesis I performed a numerical analysis of the chiral transition in the Witten–Sakai–Sugimoto model, a top-down holographic model of QCD. Such constructions provide a controlled embedding in string theory, in which the general lessons drawn from the model-independent tools can be tested.
For an excellent introduction to gauge theories and confinement, I recommend D. Tong's gauge theory lecture notes.