Gregorio Carullo

I am a third year PhD student at the University of Pisa (under the supervision of Prof. Walter Del Pozzo), member of the Data Analysis Pisa Virgo group, hence of the LIGO-Virgo collaboration. I obtained both my bachelor degree in Physics (thesis on Renormalization techniques in Non-Relativistic Quantum Mechanics, supervisor Dr. Bonati) and my master degree in Theoretical Physics of Fundamental interactions at the University of Pisa, under the supervision of Prof. Walter Del Pozzo, targeting Tests of General Relativity through Binary Black Holes coalescences.

Below a list of my research interests.


Binary Black Hole Ringdown 

I study the observational characterization of the final phase of Binary Black Holes coalescences, named 'Ringdown' and how its detection with the current Advanced network of interformeters helps us in testing Einstein's theory of General Relativity. 

During my master thesis, I developed a branch of LALInference to specifically analyse the Ringdown process. Results from this study have been summarised here, predicting the accuracy with which current ground-based interferometers would measure possible deviations from the no-hair theorem. 
The work was performed in collaboration with the Data Analysis group of NIKHEF (Amsterdam), during a prolonged visit under the supervision of Dr. Archisman Ghosh and Prof. Chris Van Den Broeck.

Additional work on this research line, in collaboration with Dr. John Veitch (University of Glasgow), was presented here, where we casted the problem in a time-domain framework and analysed GW150914 in search of additional ringdown modes.
This work formed the basis of the pyRing pipeline, which I later developed, to analyse post-merger signals observed by the LIGO and Virgo interferometers. This pipeline is now routinely used in tests of General Relativity by the LIGO and Virgo collaborations, and was first featured in the GW190521 discovery and physical implications papers to analyse this unique event.
The pipeline was also used to produce the first catalog of ringdown-only observations, featured in the GWTC-2 LVK Testing GR paper.

Several works stemmed from the above formalism, among which: a test of the area quantisation conjecture, a test of the Bekenstein-Hod universal bound and some of the best constraints on modified gravity available to date.

Recently, I focused on including the effect of black hole U(1) charges within models and analyses of ringdown signals, in the full non-perturbative regime of high charge.


Effective One Body models 

I collaborate with Dr. Alessandro Nagar (Turin Virgo group) and Prof. Sebastiano Bernuzzi (Jena Numerical Relativity group) in developing TEOBResumS, an Effective One Body (EOB) model which can accurately model the dynamics and GW emission corresponding to the interaction and mergers of compact objects. 
The model (in its flavour presented here) has been used by the LVC collaboration to analyse the first (and as of December 2018 only) binary neutron star gravitational wave signal ever detected: GW170817. 

Recently, the model has been extended to model binaries on generic (quasi-circular, eccentric, hyperbolic) orbits. We have applied a non-spinning version of this extension to the elusive GW190521 event, providing strong evidence that this event arose from a dynamical encounter.
The study can be found here.
At the moment, I am working to extend such an analysis, including the effect of spins and higher multipoles on the gravitational emission.

We have also applied strong-field numerical relativity predictions to tests of general relativity; results of this study on the first detected GW can be found here.


Short Gamma Ray Bursts and Gravitational Waves 

I participated in the LIGO-Virgo exchange program and spent a period of three months at GeorgiaTech, under the supervision of Dr. Karelle Siellez and Prof. Laura Cadonati, studying the characterization of short duration Gamma Ray Bursts (one of the most famous of which later came from first binary neutron star merger ever detected), in collaboration with the GBM team of NASA's Fermi telecope.


Publications and contacts

You can find a complete list of my publications here and the list of my short author papers here.
You can reach me at gregorio.carullo[AT]phd.unipi.it or gregorio.carullo[AT]ligo.org .



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