Sunny Vagnozzi


Visa sidan på svenska
Works at Department of Physics
Telephone 08-553 780 84
Visiting address Roslagstullsbacken 21 A, plan 5
Room A5:1078
Postal address Stockholms universitet, Fysikum 106 91 Stockholm

About me

Welcome to my personal page! I am a researcher at the Oskar Klein Centre for Cosmoparticle Physics, working within the group of Prof. Katherine Freese. I am a cosmologist and astroparticle physicist working at the interface of data analysis, theory, phenomenology, and experiments. I obtained my PhD at Stockholm University in June 2019, discussing a thesis concerning the cosmology of neutrinos (my thesis can be downloaded here).

My main aim is to probe fundamental physics using precision cosmological data. I also work on constructing viable data-driven theoretical models. Data-wise my focus is on Cosmic Microwave Background (CMB) and large-scale structure (LSS) data, whereas theory-wise my focus has been on models of dark matter, dark energy, and cosmic inflation. I am a member of the Simons Observatory collaboration, which will measure the CMB sky to exquisite accuracy from the Atacama Desert.

I received my BSc in Physics (2012) from the University of Trento and my MSc in Physics with Distinction (2014) from the University of Melbourne. I have also been an Erasmus Fellow (2012-2013) at Imperial College London and a long-term research visitor (2014-2015) at the University of Copenhagen's Niels Bohr Institute. I also hold a violin diploma (equivalent to BA, 2009) from Conservatorio Santa Cecilia.

Please see the "Teaching", "Research", and other sections below, as well as the links on the right, for more info on myself and my work.


During spring semester 2019 (VT19) I will not be teaching. In the past, I have been teaching assistant for the following courses at Stockholm University:

Previously, I was teaching assistant for the following courses at the University of Melbourne:


I am a cosmologist and astroparticle physicist working at the interface of data analysis, theory, phenomenology, and experiments. My goal is to identify, through cosmological data, those models which best describe our Universe, and to constrain their parameters. I further work on developing new methods and statistical tools to extract more information, and in a more robust way, from data.  Finally I also work on constructing data-informed viable cosmological models.

My main aim is to probe fundamental physics using precision cosmological data. I have hands-on experience in using CMB and LSS data, and CMB-LSS cross-correlations, to constrain fundamental parameters. A significant part of my efforts has been devoted towards neutrino cosmology, in particular for extracting information on neutrino masses and their mass ordering from cosmological data in a statistically robust way, and reducing systematics which might limit our understanding of neutrino properties (such as those related to galaxy bias). Other aspects of fundamental physics I have worked on include inflationary models, dark energy, galaxy bias, extra dimensions, dark matter-dark energy interactions, and axions. I am also part of the Simons Observatory CMB experiment, which will measure the temperature and polarization anisotropies of the CMB to unprecedented accuracy and will deliver exquisite constraints on fundamental physics in the next years.

On the theory side I have expertise in constructing viable dark matter, dark energy, and inflationary models, including models based on modifications to General Relativity. Concerning dark matter in particular, I have been developing self-interacting particle dark matter models which can address some of the shortcomings of collisionless cold dark matter on small scales, and have worked on predicting their signatures on cosmological and astrophysical observables and in direct detection experiments.

Other research topics I have worked on include solar physics. In particular, I have analysed solar wind data in an attempt to solve the solar abundance problem (which, alas, remains unsolved).

Most of my day-to-day work involves understanding cosmological theory, understanding and developing statistical tools, analyzing large and complex datasets, writing up results in research papers, and especially lots of coding! I mostly code in Python (for my front-end work), C, C++, and Fortran (for my back-end work). I am expert in various numerical, data analysis, and statistical techniques, including Bayesian parameter inference (which I mostly perform using CosmoMC and Montepython). I am also versant with various machine learning methods (including deep learning methods), which I use through the Python libraries Scikit-learn, AstroML, and Keras. You can find some of my codes on Github, although most of my codes aren't there yet since they would need some tidying up first (and those who are there aren't necessarily tidy)!

Research highlights and press coverage

Here is a very personal selection of seven (why seven?) highlights from my research (below that a selection of media coverage of my work):

  • for the first time constructed a dissipative dark matter model where the entire dark sector is dissipative and showed that it can solve many small-scale problems of LCDM (arXiv, Phys. Rev. D, Editors' Suggestion)
  • analyzed for the first time solar wind data in light of the solar modeling problem, which remains unsolved (arXiv, ApJ)
  • obtained the tighest yet most robust constraints on the sum of neutrino masses and their mass ordering from cosmology (arXiv, Phys. Rev. D, results selected in the Review of Particle Physics)
  • obtained the first constraints on brane-world extra dimensions from gravitational waves (arXiv, Phys. Rev. D)
  • brought to the light for the first time an unexpected connection between the neutrino mass ordering and dark energy, showing that future lab measurements of the neutrino mass ordering can potentially rule out many dark energy models (arXiv, Phys. Rev. D)
  • conclusively showed (by MCMC forecast) that in cosmologies with massive neutrinos the galaxy bias must be defined with respect to the cold dark matter+baryons density field to avoid incorrect parameter estimation (arXiv, JCAP)
  • for the first time tested the theory of mimetic gravity in a statistically robust way against data (arXiv, Class. Quant. Grav.)

My work has been covered in various popular science (and not) magazines, global news websites, and blogs. Below are links to selected articles covering my work:

I also believe in the value and importance of timely and quality peer review, and am always eager to perform peer reviewing activity. I have reviewed for most of the main journals in the field, please see my Publons profile for more details on my reviewing activity.

Beyond physics

When I'm not doing physics, my interests range from music, to cooking, to sports (partly trying to make up for the previous interest), and finally to mastering new languages. Music-wise, I enjoy playing the violin since I was 5 and the piano since I was 8, and hold a violin diploma since 2009. Sports-wise I have been a scuba-diver since I was 10, and hold various international certifications. I also enjoy running, skiing, I used to rock climb, and am notoriously a huge Juventus fan. I enjoy mastering new languages, and am fluent in Italian, English, Swedish, and Spanish, while I can read Danish, and Norwegian. I also really enjoy travelling, see here for a map of all the countries I've been to. I am originally from Terracina, Italy, a wonderful city on the Italian coast between Rome and Naples.

Last updated: August 27, 2019

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