CV and full scientific publication list (pdf).
Most of my scientific papers are available on ArXiv and/or ADS.
orcid.org/0000-0002-3929-6932Research activity
I am a theoretical astrophysicist and my research is mostly focused on comparing models and simulations with astronomical data, in order to advance our knowledge of the universe.
Currently, my main research interest is in astrobiology, the interdisciplinary study of the origin, evolution, distribution and future of life in the universe. I am working on models of planetary and galactic habitability, and on the search for biosignatures and technosignatures.
In the past I have done work in many areas of physical cosmology, including the analysis of the cosmic microwave background anisotropy, the large-scale structure of the universe, inflation, dark matter and dark energy.
Below is an annotated list of some of my research projects.
Active research projects
- Planetary constraints on the evolution of life, intelligence and technology
- Supermassive black holes and galactic habitability
- Biosignatures
- Technosignatures
- Panspermia
Past projects
- Real-time cosmology
- Violations of isotropy
- Gravitational lensing of the cosmic microwave background
- Non-gaussianity of primordial perturbations
- Dark energy and integrated Sachs-Wolfe effect
- Unified models of dark matter and dark energy
- Dark energy and quintessence
- Planck (a cosmic microwave background satellite experiment)
- BOOMERANG (a cosmic microwave background ballon experiment)
- MAXIMA (a cosmic microwave background balloon experiment)
- Cosmic microwave background data analysis
- Thermal history of the universe
ACTIVE Research projects
Planetary constraints on the evolution of life, intelligence and technology
- The Oxygen Bottleneck for Technospheres – Balbi, A., Frank, A. Nature Astronomy (2023) – (Press coverage: link, link, link, link, link, link, link, link, link, link, link – more press here)
- Planetary Scale Information Transmission in the Biosphere and Technosphere: Limits and Evolution – Lingam, M., Frank, A., Balbi, A. Life 13, 1850 (2023) – (Press coverage: link)
- Beyond mediocrity: how common is life? – Balbi, A., Lingam, M. Monthly Notices of the Royal Astronomical Society, 522, 3117–3123 (2023)
- A Bayesian Analysis of Technological Intelligence in Land and Oceans – Lingam, M., Balbi, A., and Mahajan, S. M. ApJ 945 23 (2023) – (Press coverage: link)
- Excitation Properties of Photopigments and Their Possible Dependence on the Host Star – Lingam, M., Balbi, A., and Mahajan, S. M., ApJL 921 L41 (2021)
Supermassive black holes and galactic habitability
The center of the Milky Way hosts a supermassive black hole (SgrA*). At the beginning of its history, the black hole was accreting matter at a much higher rate and was therefore an active galactic nucleus (AGN), which released large amounts of ionizing radiation in space. This might have had large-scale consequences on the habitability of planets in the innermost regions of the galaxy, affecting their atmospheres and possibly their surface biosphere. In 2017, I co-authored a pioneering study on this subject. (For press coverage see here, here, here and here). This has been followed by a number of additional works that explored further implications of the presence of a supermassive black hole in the Milky Way.
- The habitability of the Milky Way during the active phase of its central supermassive black hole – Balbi, A., Tombesi, F., NatSR, 7, 16626 (2017)
- Comparative analysis of the influence of Sgr A* and nearby active galactic nuclei on the mass loss of known exoplanets – Agata M. Wisłocka, Andjelka B. Kovačević, Amedeo Balbi, Astronomy & Astrophysics (2019)
- The habitability of the Galactic bulge – Balbi, A., Hami, M., & Kovačević, A. B., Life, 10(8), 132 (2020)
- The impact of tidal disruption events on galactic habitability – Pacetti, E., Balbi, A., Lingam, M., Tombesi, F., & Perlman, E., Monthly Notices of the Royal Astronomical Society, 498, 3153 (2020)
- The impact of AGN outflows on the surface habitability of terrestrial planets in the Milky Way – Ambrifi, A., Balbi, A., Lingam, M., Tombesi, F., & Perlman, E., Monthly Notices of the Royal Astronomical Society, 512, 505 (2022)
Impact of biosignatures detection (or non-detection)
The search for life on extrasolar worlds by way of spectroscopic biosignature detection is among the most compelling scientific endeavors of the next decades. We explored the implications of either discovering or ruling out the presence of detectable biosignatures on planets within a few tens of light years from Earth, a distance within reach of future searches. Using a Bayesian methodology, we showed that not detecting biosignatures in such sample volume would bring no added information about the galactic population of life-hosting exoplanets. Conversely, if life arose independently on other planets, even a single detection would imply exobiospheres to be more abundant than pulsars. Putative interstellar transfer of life through the panspermia mechanism may, however, significantly lower this estimate.
- Quantifying the information impact of future searches for exoplanetary biosignatures – Balbi, A. and Grimaldi, C. Proceedings of the National Academy of Sciences, p. 202007560 (2020)
Press coverage of this work:
- Un segno di vita vale per centomila esopianeti, tvsvizzera.it – 28.06.20
- Se l’AI scopre 50 nuovi pianeti scavando nei dati NASA, Repubblica.it – 26.08.20
- Centomila esopianeti della Via Lattea potrebbero ospitare la vita (se ne trovassimo almeno uno), Wired – 20.08.20
- Vita aliena su oltre centomila pianeti della Via Lattea: l’ipotesi degli scienziati italiani, FanPage – 20.08.20
- Vita su altri pianeti? Solo nella Via Lattea candidati 100mila corpi celesti La scoperta dell’Università di Tor Vergata, Il Messaggero – 19.08.20
- “Centomila pianeti abitati nella sola Via Lattea, se c’è vita fuori dalla Terra”, La Repubblica – 19.08.20
- Bayesian statistics and the hunt for ET, Cosmos Magazine – 19.08.20
Technosignatures
The discovery of thousands of extrasolar planets has given new impulse to the search for technological activity from extraterrestrial life, whose signs can be remotely detected by astronomical observations (technosignatures). I am involved in a number of projects that seek to explore and define this goal. I am particularly interested in the interplay between technological activity and the biosphere, and in quantifying how the duration of the technological phase affects the probability of technosignature detection with future observations.
- The Impact of the Temporal Distribution of Communicating Civilizations on their Detectability – Balbi, A., Astrobiology, 18, 54 (2018)
- Copernicanism and the typicality in time – Cirkovic, M. M. and Balbi, A., International Journal of Astrobiology, 1-9 (2019)
- Longevity Is the Key Factor in the Search for Technosignatures – Balbi, A., & Ćirković, M. M., The Astronomical Journal, 161, 222 (2021)
- Technosignatures Longevity and Lindy’s Law – Balbi, A. & Grimaldi, C., The Astronomical Journal, 167, 3 (2024) (press: link)
- Evaluation of investigational paradigms for the discovery of non-canonical astrophysical phenomena – Singam, C. A. K., et al., arXiv e-prints, arXiv:2011.10086 (2020)
- Searching for Technosignatures: Implications of Detection and Non-Detection – Haqq-Misra, J., Berea, A., Balbi, A., & Grimaldi, C., Bulletin of the American Astronomical Society, 51, 79 (2019)
- Statistical issues in the search for technosignatures – A. Balbi & C. Grimaldi, in ‘Technosignatures: Searching for and Communicating with Intelligence in Our Universe’ Berea, A. (ed.) [TECH, Volume in the series Astrobiology Perspectives on Life of the Universe, Eds. Richard Gordon & Joseph Seckbach]. Wiley-Scrivener, Beverly, Massachusetts, USA (2021)
- NASA and the Search for Technosignatures: A Report from the NASA Technosignatures Workshop
– NASA Technosignatures Workshop Participants (2018) - Searches for Technosignatures in Astronomy and Astrophysics – Wright, J., et al. Astro2020: Decadal Survey on Astronomy and Astrophysics, science white papers, no. 389; Bulletin of the American Astronomical Society, Vol. 51, Issue 3, id. 389 (2019)
Panspermia
The proposition that life can spread from one planetary system to another (interstellar panspermia) has a long history, but this hypothesis is difficult to test through observations. We recently developed a mathematical model that takes parameters such as the microbial survival lifetime, the stellar velocity dispersion, and the dispersion of ejecta into account in order to assess the prospects for detecting interstellar panspermia. We also constructed a mathematical model that incorporates three intertwined processes (i.e. the birth, extinction and transfer of life) and accordingly derive the probability distribution function and other statistical properties (e.g. mean) for the number of worlds with biospheres.
- A birth-death-migration model for life in astrophysical environments – Lingam, M., Grimaldi, C., & Balbi, A., Monthly Notices of the Royal Astronomical Society, 509, 4365 (2022)
- Feasibility of Detecting Interstellar Panspermia in Astrophysical Environments – Grimaldi, C., Lingam, M., & Balbi, A., The Astronomical Journal, 162, 23 (2021)
- Why We Should Take Interstellar Panspermia Seriously – A. Balbi in Planet Formation and Panspermia: New Prospects for the Movement of Life through Space, edited by Branislav Vukotic, Richard Gordon and Joseph Seckbach. Wiley-Scrivener, Beverly, Massachusetts, USA (2021)
PAST projects
Real-time cosmology
The idea, originally proposed by Allan Sandage in the 1960s, is that one can observe the evolution of cosmological redshift in time, by means of ultra-high precision spectroscopy. This can give interesting information on cosmological models as well as on the dynamics of bound objects. I explored the implications of the idea in a number of papers and summarized them in a review.
- Real-time cosmology – Quercellini, C., Amendola, L., Balbi, A., Cabella, P., Quartin, M. Physics Reports, Volume 521, Issue 3, p. 95-134 (2012)
- The time evolution of cosmological redshift as a test of dark energy – Balbi, A. and Quercellini, C. MNRAS 382, 1623 (2007)
- Mapping the galactic gravitational potential with peculiar acceleration – Quercellini, C., Amendola, L., and Balbi, A.MNRAS 391, 1308 (2008)
- Peculiar acceleration – Amendola, L., Balbi, A., and Quercellini, C. PhLB 660, 81 (2008)
- Cosmic parallax as a probe of late time anisotropic expansion – Quercellini, C., Cabella, P., Amendola, L., Quartin, M., and Balbi, A. PhRvD 80, 063527 (2009)
Gravitational lensing of the cosmic microwave background
Observing the effect of gravitational lensing of the cosmic microwave background produced by matter distribution in the universe can give important cosmological information. I explored this issue in the following papers.
- Neutrinos and dark energy constraints from future galaxy surveys and CMB lensing information – Santos, L., Cabella, P., Balbi, A., Vittorio, N., PhRvD, 88, 043505 (2013)
- Forecasting isocurvature models with CMB lensing information: Axion and curvaton scenarios – Santos, L., Cabella, P., Balbi, A., Vittorio, N., PhRvD, 86, 023002 (2012)
Violations of isotropy
CMB data from the WMAP satellite showed hints of possibile anomalies in the statistical isotropy of temperature fluctuations, one of the tenets of standard cosmology. This can be due to instrumental effects or to physical mechanisms. I investigated the issue in a number of papers.
- Quadrant asymmetry in the angular distribution of cosmic microwave background in the Planck satellite data – Santos, L., Cabella, P., Villela,
T., Balbi, A., Vittorio, N., Wuensche, C. A., A&A, 569, A75 (2014) - Searching for a dipole modulation in the large-scale structure of the Universe – Fernández-Cobos, R., Vielva, P., Pietrobon, D., Balbi, A.,
Martínez-González, E., Barreiro, R. B., MNRAS, 441, 2392 (2014) - Needlet bispectrum asymmetries in the WMAP 5-year data – Pietrobon, D., Cabella, P., Balbi, A., Crittenden, R., de Gasperis, G., and Vittorio, N. MNRAS 402, L34 (2010)
- Needlet detection of features in the WMAP CMB sky and the impact on anisotropies and hemispherical asymmetries – Pietrobon, D., Amblard, A., Balbi, A., Cabella, P., Cooray, A., and Marinucci, D. PhRvD 78, 103504 (2008)
- Cosmological parameters and the WMAP data revisited – Hansen, F. K., Balbi, A., Banday, A. J., and Górski, K. M.MNRAS 354, 905 (2004)
Non-gaussianity of primordial perturbations
Inflationary models predict that density perturbations in the early universe have a non-gaussian statistics. Measuring the amount of non-gaussianity can constrain theoretical models. I investigated the issue through the analysis of CMB data.
- Foreground influence on primordial non-Gaussianity estimates: needlet analysis of WMAP 5-year data – Cabella, P., Pietrobon, D., Veneziani, M., Balbi, A., Crittenden, R., de Gasperis, G., Quercellini, C., and Vittorio, N. MNRAS 405, 961 (2010)
- Constraints on primordial non-Gaussianity from a needlet analysis of the WMAP-5 data – Pietrobon, D., Cabella, P., Balbi, A., de Gasperis, G., and Vittorio, N. MNRAS 396, 1682 (2009)
- Tests for Gaussianity of the MAXIMA-1 Cosmic Microwave Background Map – Wu, J. H. P., and 11 colleagues PhRvL 87, 251303 (2001)
Dark energy and integrated Sachs-Wolfe effect
One of the ways of studing dark energy is through the imprint that the onset of the accelerating phase of the universe leaves on the CMB. This is called integrated Sachs-Wolfe effect, and can be observed by cross-correlating the CMB with large-scale structure data. I authored (with my then student Davide Pietrobon) one of the first studies finding evidences of this signal in the data, using a new statistical technique (courtesy of Domenico Marinucci).
- Integrated Sachs-Wolfe effect from the cross correlation of WMAP 3year and the NRAO VLA sky survey data: New results and constraints on dark energy – Pietrobon, D., Balbi, A., and Marinucci, D. PhRvD 74, 043524 (2006)
Unified models of dark matter and dark energy
According to some theoretical models, dark matter and dark energy may be the same thing under different form. Our analyses showed that this might be the case, but observations available at the time could not tell the difference from alternative explanations.
- Affine parametrization of the dark sector: Constraints from WMAP5 and SDSS – Pietrobon, D., Balbi, A., Bruni, M., and Quercellini, C. PhRvD 78, 083510 (2008)
- Late universe dynamics with scale-independent linear couplings in the dark sector – Quercellini, C., Bruni, M., Balbi, A., and Pietrobon, D. PhRvD 78, 063527 (2008)
- ΛαDM: Observational constraints on unified dark matter with constant speed of sound – Balbi, A., Bruni, M., and Quercellini, C. PhRvD 76, 103519 (2007)
- Affine equation of state from quintessence and k-essence fields – Quercellini, C., Bruni, M., and Balbi, A. CQGra 24, 5413 (2007)
Dark energy and quintessence
One of the possible explanations of dark energy is that it is caused by the presence of a fundamental field called “quintessence”. The advantage of these models is that they may alleviate the so-called “coincidence problem”, that is the weird fact that the vacuum energy density have begun to dominate with respect to the density of matter roughly at present time.
- Scalar field dark energy and cosmic microwave background– Baccigalupi, C., Balbi, A., Matarrese, S., Perrotta, F., and Vittorio, N. NuPhS 124, 68 (2003)
- Probing Dark Energy with the Cosmic Microwave Background: Projected Constraints from the Wilkinson Microwave Anisotropy Probe and Planck – Balbi, A., Baccigalupi, C., Perrotta, F., Matarrese, S., and Vittorio, N.ApJ 588, L5 (2003)
- Constraints on flat cosmologies with tracking quintessence from cosmic microwave background observations – Baccigalupi, C., Balbi, A., Matarrese, S., Perrotta, F., and Vittorio, N. PhRvD 65, 063520 (2002)
- Implications for Quintessence Models from MAXIMA-1 and BOOMERANG-98 – Balbi, A., Baccigalupi, C., Matarrese, S., Perrotta, F., and Vittorio, N. ApJ 547, L89 (2001)
Planck
Planck was an ESA space mission designed to observe the CMB to unprecedented details. I started collaborating to Planck in 1996 (when it was still in the study phase) and continued until 2012, with the intermediate data release, contributing to many of the procedures that were used to analyze its data, and to extract its scientific consequences.
- Planck early results. I. The Planck mission – Planck Collaboration, and 274
colleagues, A&A, 536, A1 (2011) - Optimising Boltzmann codes for the PLANCK era – Hamann, J., Balbi, A., Lesgourgues, J., and Quercellini, C. JCAP 4, 11 (2009)
- Making maps from Planck LFI 30 GHz data – Ashdown, M. A. J., and 18 colleagues A&A 471, 361 (2007)
- Making sky maps from Planck data – Ashdown, M. A. J., and 18 colleagues A&A 467, 761 (2007)
- Cosmology from Planck – Balbi, A. NewAR 51, 281 (2007)
- CMB power spectrum estimation for the Planck Surveyor – Balbi, A., de Gasperis, G., Natoli, P., and Vittorio, N. A&A395, 417 (2002)
BOOMERANG
I briefly collaborated to the second phase of the BOOMERANG balloon experiment, that studied the polarized component of the cosmic microwave background.
- BOOMERanG results – Polenta, G., and 41 colleagues AdSpR36, 1064 (2005)
- Measuring CMB polarization with Boomerang – Montroy, T., and 40 colleagues NewAR 47, 1057 (2003)
- BOOMERANG returns – Mauskopf, P. D., and 40 colleaguesNewAR 47, 733 (2003)
MAXIMA
MAXIMA was a balloon-borne experiment that produced, in 2000, one of the first high-resolution images of the cosmic microwave background temperature fluctuations. MAXIMA results put precise constraints on cosmological models, showing that we live in a universe with flat geometry. I gave a relevant contribution to all of MAXIMA scientific results and data analysis, and I was the first author of the cosmological parameter paper. Here is MAXIMA official press release with a summary of results. Other non-technical information can be found here and here and in articles that appeared on Physics Today and Scientific American. MAXIMA results also got strong coverage in the press, with articles on The San Francisco Chronicle, The Economist, The New York Times, The Washington Post and again The New York Times. The PBS show NOVA discussed MAXIMA in one of its episodes.
- Constraints on Cosmological Parameters from MAXIMA-1 – Balbi, A., and 18 colleagues ApJ 545, L1 (2000)
- MAXIMA-1: A Measurement of the Cosmic Microwave Background Anisotropy on Angular Scales of 10′-5° – Hanany, S., and 21 colleagues ApJ 545, L5 (2000)
- Cosmology from MAXIMA-1, BOOMERANG, and COBE DMR Cosmic Microwave Background Observations – Jaffe, A. H., and 41 colleagues PhRvL 86, 3475 (2001)
- Cosmological Implications of the MAXIMA-1 High-Resolution Cosmic Microwave Background Anisotropy Measurement – Stompor, R., and 19 colleagues ApJ 561, L7 (2001)
- A High Spatial Resolution Analysis of the MAXIMA-1 Cosmic Microwave Background Anisotropy Data – Lee, A. T., and 19 colleagues ApJ 561, L1 (2001)
- MAXIMA: A balloon-borne cosmic microwave background anisotropy experiment – Rabii, B., and 22 colleagues RScI 77, 071101 (2006)
- Determining Foreground Contamination in Cosmic Microwave Background Observations: Diffuse Galactic Emission in the MAXIMA-I Field – Jaffe, A. H., and 13 colleagues ApJ 615, 55 (2004)
- Multiple methods for estimating the bispectrum of the cosmic microwave background with application to the MAXIMA data – Santos, M. G., and 13 colleagues MNRAS341, 623 (2003)
- Frequentist estimation of cosmological parameters from the MAXIMA-1 cosmic microwave background anisotropy data – Abroe, M. E., and 14 colleagues MNRAS 334, 11 (2002)
- Estimate of the Cosmological Bispectrum from the MAXIMA-1 Cosmic Microwave Background Map – Santos, M. G., and 13 colleagues PhRvL 88, 241302 (2002)
Cosmic microwave background data analysis
Extracting cosmological information from CMB data is challenging and computing-intensive. Some of my research activity was devoted to finding new algorithms, statistical techniques and tools to maximize the scientific output of observations.
- NeedATool: A Needlet Analysis Tool for Cosmological Data Processing – Pietrobon, D., Balbi, A., Cabella, P., & Gorski, K. M., ApJ, 723, 1 (2010)
- Spherical needlets for cosmic microwave background data analysis – Marinucci, D., and 8 colleagues MNRAS 383, 539 (2008)
- Comparison of map-making algorithms for CMB experiments – Poutanen, T., and 14 colleagues A&A 449, 1311 (2006)
- Unbiased estimation of an angular power spectrum – Polenta, G., Marinucci, D., Balbi, A., de Bernardis, P., Hivon, E., Masi, S., Natoli, P., and Vittorio, N. JCAP 11, 1 (2005)
- ROMA: A map-making algorithm for polarised CMB data sets – de Gasperis, G., Balbi, A., Cabella, P., Natoli, P., and Vittorio, N. A&A 436, 1159 (2005)
- Making maps of the cosmic microwave background: The MAXIMA example – Stompor, R., and 12 colleagues PhRvD65, 022003 (2002)
- Asymmetric Beams in Cosmic Microwave Background Anisotropy Experiments – Wu, J. H. P., and 12 colleaguesApJS 132, 1 (2001)
Thermal history of the universe
The universe went through different physical phases, as its temperature changed from the big bang to the present epoch due to the expansion of space. Some of the pivotal moments in the history of the cosmos (such as the synthesis of light nuclei, or the formation of neutral hydrogen atoms, or of the ignition of the first stars) can be explored through cosmological observations. I addressed the study of the thermal history of the universe in some of my earliest scientific papers.
- On the Primordial Helium Content: Cosmic Microwave Background and Stellar Constraints – Bono, G., Balbi, A., Cassisi, S., Vittorio, N., and Buonanno, R. ApJ 568, 463 (2002)
- Secondary CMB anisotropies from the kinetic SZ effect – Valageas, P., Balbi, A., and Silk, J. A&A 367, 1 (2001)
- Cosmic Microwave Background Anisotropy at Degree Angular Scales and the Thermal History of the Universe – de Bernardis, P., Balbi, A., de Gasperis, G., Melchiorri, A., and Vittorio, N. ApJ 480, 1 (1997)