This page collects my work on cosmology, galaxy formation and gravitation, organized by topic, with a link to every paper. For a complete and up-to-date list, you can also search my publication records on arXiv, ADS, inSPIRE or Google Scholar.
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Cosmology
Cosmology
Interacting dark sector models
Interacting dark sector models
A central question in cosmology is whether dark energy (DE) and cold dark matter (CDM) evolve independently, as in ΛCDM, or exchange energy through a non-gravitational interaction. Since no known symmetry forbids such a coupling, interacting models are a natural alternative to the standard picture. Most studies assume an interaction proportional to the DE density, but extensions include nonlinear dependence on both dark components, couplings defined through the CDM/DE density ratio, and unified-fluid models such as the generalized Chaplygin gas.
Two strategies are used to test these ideas: constraining specific models with CMB, matter power spectra and other data, and model-independent approaches such as null tests and direct reconstruction of the interaction.
J.S. Lima, R. von Marttens and L. Casarini, 2025, "Interacting dark sector with quadratic coupling: theoretical and observational viability", Eur. Phys. J. Plus 140, 297; arXiv:2412.16299. [arXiv; ADS]
R. von Marttens, J.E. Gonzalez, J. Alcaniz, V. Marra and L. Casarini, 2021, "Model-independent reconstruction of dark sector interactions", Phys. Rev. D 104, 043515; arXiv:2011.10846. [arXiv; ADS]
R. von Marttens, L. Lombriser, M. Kunz, V. Marra, L. Casarini and J. Alcaniz, 2020, "Dark degeneracy I: Dynamical or interacting dark energy?", Phys. Dark Univ. 28, 100490; arXiv:1911.02618. [arXiv; ADS]
R. von Marttens, V. Marra, L. Casarini, J.E. Gonzalez and J. Alcaniz, 2019, "Null test for interactions in the dark sector", Phys. Rev. D 99, 043521; arXiv:1812.02333. [arXiv; ADS]
R. von Marttens, L. Casarini, D.F. Mota and W. Zimdahl, 2019, "Cosmological constraints on parametrized interacting dark energy", Phys. Dark Univ. 23, 100248; arXiv:1807.11380. [arXiv; ADS]
R.F. vom Marttens, L. Casarini, W. Zimdahl, W.S. Hipólito-Ricaldi and D.F. Mota, 2017, "Does a generalized Chaplygin gas correctly describe the cosmological dark sector?", Phys. Dark Univ. 15, 114; arXiv:1702.00651. [arXiv; ADS]
R.F. vom Marttens, L. Casarini, W.S. Hipólito-Ricaldi and W. Zimdahl, 2017, "CMB and matter power spectra with non-linear dark-sector interactions", JCAP 01 (2017) 050; arXiv:1610.01665. [arXiv; ADS]
Nonlinear matter power spectrum in dynamical dark energy cosmologies
Nonlinear matter power spectrum in dynamical dark energy cosmologies
Surveys of large-scale structure probe dark energy (DE) through the nonlinear matter power spectrum at many redshifts, and extracting reliable constraints requires theoretical predictions of matching accuracy. At the scales and precision involved, simple analytic approximations are not enough: accurate predictions rely on N-body and hydrodynamical simulations that include baryonic physics. The main difficulty is cost, since simulating every DE equation of state w(a) and every allowed set of cosmological parameters is computationally prohibitive.
This line of work exploits regularities to reduce that cost. The spectra of dynamical DE models, such as those described by the w₀-wa parametrization, can be reconstructed at the percent level from a suitable set of constant-w cosmologies, and this mapping allows existing emulators to be extended to time-varying equations of state. Perturbation theory complements this approach by linking the background dynamics of w(z) to the growth of structures.
C. Escamilla-Rivera, L. Casarini, J.C. Fabris and J.S. Alcaniz, 2016, "Linear and non-linear perturbations in dark energy models", JCAP 11 (2016) 010; arXiv:1605.01475. [arXiv; ADS]
L. Casarini, S.A. Bonometto, E. Tessarotto and P.-S. Corasaniti, 2016, "Extending the Coyote emulator to dark energy models with standard w0-wa parametrization of the equation of state", JCAP 08 (2016) 008; arXiv:1601.07230. [arXiv; ADS]
L. Casarini, A.V. Macciò, S.A. Bonometto and G.S. Stinson, 2011, "High accuracy power spectra including baryonic physics in dynamical Dark Energy models", Mon. Not. R. Astron. Soc. 412, 911; arXiv:1005.4683. [arXiv; ADS]
L. Casarini, 2010, "High-precision spectra for dynamical Dark Energy cosmologies from constant-w models", JCAP 08 (2010) 005; arXiv:1006.0981. [arXiv; ADS]
L. Casarini, 2010, "Spectra of dynamical Dark Energy cosmologies from constant-w models", New Astron. 15, 575; arXiv:0911.1315. [arXiv; ADS]
L. Casarini, A.V. Macciò and S.A. Bonometto, 2009, "Dynamical Dark Energy simulations: high accuracy Power Spectra at high redshift", JCAP 03 (2009) 014; arXiv:0810.0190. [arXiv; ADS]
Weak lensing and nonlinear predictions
Weak lensing and nonlinear predictions
Weak gravitational lensing is one of the most powerful probes of dark energy and the growth of structure, and current and forthcoming surveys are measuring tomographic shear spectra with very high precision. Extracting reliable cosmological constraints from them requires theoretical predictions of matching accuracy in the nonlinear regime. Simulations are the reference tool, but they must keep box size and sample variance under control. The choice of nonlinear prescription, and the treatment of baryonic feedback on small scales, can also bias the estimated cosmological parameters if not properly accounted for. Forecasts for future surveys therefore have to quantify these effects.
A complementary problem is inversion. Observations provide the shear, not the density fluctuations, so methods are needed to recover the matter density spectra at different redshifts directly from the measured shear. Accurate predictions, controlled systematics and robust inversion remain essential for reliable constraints.
M. Martinelli, I. Tutusaus, M. Archidiacono et al., 2021, "Euclid: Impact of non-linear and baryonic feedback prescriptions on cosmological parameter estimation from weak lensing cosmic shear", Astron. Astrophys. 649, A100; arXiv:2010.12382. [arXiv; ADS]
L. Casarini, O. Piattella, S. Bonometto and M. Mezzetti, 2015, "Sample variance in N-body simulations and impact on tomographic shear predictions", Astrophys. J. 812, 16; arXiv:1406.5374. [arXiv; ADS]
L. Casarini, S. A. Bonometto, S. Borgani et al., 2012, "Tomographic weak lensing shear spectra from large N-body and hydrodynamical simulations", Astron. Astrophys. 542, A126; arXiv:1203.5251. [arXiv; ADS]
M. Mezzetti, S.A. Bonometto, L. Casarini and G. Murante, 2012, "Direct recovery of fluctuation spectra from tomographic shear spectra", JCAP 06 (2012) 005; arXiv:1203.2777. [arXiv; ADS]
L. Casarini, G. La Vacca, L. Amendola, S.A. Bonometto and A.V. Macciò, 2011, "Non-linear weak lensing forecasts", JCAP 03 (2011) 026; arXiv:1102.3877. [arXiv; ADS]
Beyond cold dark matter
Beyond cold dark matter
The standard model assumes dark matter is cold and collisionless, behaving as an ideal pressureless fluid. This works well on large scales but faces difficulties on small scales. One direction is to give dark matter a small "warmness": a velocity dispersion changes pressure and free-streaming, and effective descriptions such as the reduced relativistic gas capture this. The imprint appears in the CMB and in a small-scale cut-off of the matter power spectrum, mainly for particles of non-thermal origin.
A second direction is dissipative dark matter, for example with viscosity, which changes structure formation and may ease small-scale problems. Understanding sub-horizon perturbation evolution near the DM-DE equivalence epoch completes the picture, connecting dark matter microphysics to observable signatures.
W.S. Hipolito-Ricaldi, R.F. vom Marttens, J.C. Fabris, I.L. Shapiro and L. Casarini, 2018, "On general features of warm dark matter with reduced relativistic gas", Eur. Phys. J. C 78, 365; arXiv:1706.08595. [arXiv; ADS]
O.F. Piattella, L. Casarini, J.C. Fabris and J.A. de Freitas Pacheco, 2016, "Dark matter velocity dispersion effects on CMB and matter power spectra", JCAP 02 (2016) 024; arXiv:1507.00982. [arXiv; ADS]
H. Velten, T.R.P. Caramês, J.C. Fabris, L. Casarini and R.C. Batista, 2014, "Structure formation in a Λ viscous CDM universe", Phys. Rev. D 90, 123526; arXiv:1410.3066. [arXiv; ADS]
O.F. Piattella, D.L.A. Martins and L. Casarini, 2014, "Sub-horizon evolution of cold dark matter perturbations through dark matter-dark energy equivalence epoch", JCAP 10 (2014) 031; arXiv:1407.4773. [arXiv; ADS]
Hubble constant
Hubble constant
ML is also useful beyond classification, in cosmological inference. Local measurements of the Hubble constant, based on Cepheids and Type Ia supernovae, differ by about 5σ from the value inferred from Planck CMB observations under ΛCDM. Comparing different methods of analysis is fundamental to understanding this tension, especially in view of the data from the next generation of surveys. Applying ML to cosmic chronometers provides an independent route to estimate the Hubble constant from observations of the expansion history.
CMB polarization and reionization
CMB polarization and reionization
The polarization of the cosmic microwave background (CMB) carries information on the epoch when the first sources of radiation ionized the intergalactic medium. Its large-angular-scale signal is sensitive to the integrated optical depth to reionization, and so to how and when this transition took place.
Reionization need not have been a single, sudden event. More complex histories leave distinct signatures in the polarization spectrum, and high-precision CMB measurements, combined with observations of high-redshift galaxies and quasars, can be used to test them and to constrain the nature and timing of the first sources of radiation.
Galaxies
Galaxies
ETGs and the fundamental plane
ETGs and the fundamental plane
Early-type galaxies (ETGs) are reference systems for galaxy formation, and their scaling relations, especially the Fundamental Plane, are key benchmarks for models. Hydrodynamical simulations have historically struggled to reproduce the observed tilt of the Fundamental Plane, a discrepancy often attributed to feedback physics or limited resolution. Building virtual ETG catalogues from simulations and validating them against real observations is therefore a necessary step to test whether simulated galaxies are comparable to observed ones.
P. de Araujo Ferreira, N.R. Napolitano, C. Tortora, L. Casarini and F. Villaescusa-Navarro, 2026, "Reconciling the Fundamental Plane of Early-Type Galaxies with hydrodynamical simulations: The case of IllustrisTNG100-1", submitted to Mon. Not. R. Astron. Soc.; arXiv:2605.31548. [arXiv; ADS]
P. de Araujo Ferreira, N.R. Napolitano, L. Casarini, C. Tortora, R. von Marttens and S. Wu, 2025, "The catalogue of virtual early-type galaxies from IllustrisTNG: validation and real observation consistency", Mon. Not. R. Astron. Soc. 539, 2855; arXiv:2501.04932. [arXiv; ADS]
Dark matter in galaxies with machine learning
Dark matter in galaxies with machine learning
The total mass of a galaxy within its effective radius carries important information on its dark matter content and evolution, but it is hard to measure with dynamics or lensing alone. Machine learning trained on simulations offers an alternative: it can predict total and dark mass, as well as halo properties, from simple observables. This approach is particularly valuable for next-generation surveys, which will provide data for millions of galaxies, and it helps to constrain the effect of baryonic feedback on the dark matter distribution.
S. Wu, N.R. Napolitano, C. Tortora et al., 2024, "Total and dark mass from observations of galaxy centers with Machine Learning", Astron. Astrophys. 686, A80; arXiv:2310.02816. [arXiv; ADS]
R. von Marttens, L. Casarini, N.R. Napolitano et al., 2022, "Inferring galaxy dark halo properties from visible matter with Machine Learning", Mon. Not. R. Astron. Soc. 516, 3924; arXiv:2111.01185. [arXiv; ADS]
Dark energy and galaxy formation
Dark energy and galaxy formation
Galaxy formation is usually studied in ΛCDM, where dark energy plays little role on galactic scales. An open question is whether the nature of DE leaves an imprint on individual galaxies. High-resolution hydrodynamical simulations in dynamical DE (including self-interacting scalar fields) and coupled DE scenarios show that changes in expansion history and structure growth alter halo concentration, mass assembly and internal structure.
The effects extend to Milky Way-size halos, lower-mass halos and dwarf galaxies, affecting the host and its satellites. Galactic scales therefore offer a complementary probe of DE, and the cosmological model cannot be ignored in galaxy formation simulations.
C. Penzo, A.V. Macciò, M. Baldi, L. Casarini, J. Oñorbe and A.A. Dutton, 2016, "Effects of Coupled Dark Energy on the Milky Way and its Satellites", Mon. Not. R. Astron. Soc. 461, 2490; arXiv:1504.07243. [arXiv; ADS]
C. Penzo, A.V. Macciò, L. Casarini, G.S. Stinson and J. Wadsley, 2014, "Dark MaGICC: the effect of dark energy on disc galaxy formation. Cosmology does matter", Mon. Not. R. Astron. Soc. 442, 176; arXiv:1401.3338. [arXiv; ADS]
Star-galaxy-quasar classification
Star-galaxy-quasar classification
Large photometric surveys such as J-PAS and J-PLUS produce datasets too large for traditional analysis, so accurate and efficient machine learning (ML) methods are becoming essential. A typical case is source classification, the separation of stars, galaxies and quasars in photometric catalogues. The standard pipelines of the J-PLUS data releases provide only a star-galaxy classification, leaving quasars unidentified among the other sources. ML classifiers trained on multi-band photometry offer a scalable alternative, applicable to catalogues of tens of millions of sources, and the pathfinder miniJPAS survey is used to develop and test these methods before they are applied to the full surveys.
R. von Marttens, V. Marra, M. Quartin et al., 2024, "J-PLUS: galaxy-star-quasar classification for DR3", Mon. Not. R. Astron. Soc. 527, 3347; arXiv:2212.05868. [arXiv; ADS]
P.O. Baqui, V. Marra, L. Casarini et al., 2021, "The miniJPAS survey: star-galaxy classification using machine learning", Astron. Astrophys. 645, A87; arXiv:2007.07622. [arXiv; ADS]
Gravitation
Gravitation
Gravastars
Gravastars
Directly observing black holes is difficult, because ultra-compact horizonless objects can also have unstable circular photon orbits and mimic some of their signatures. The gravastar (gravitational vacuum star), proposed by Mazur and Mottola, is a well-known example: in its thin-shell version, a vacuum interior is matched to an exterior solution across a thin shell of matter, with stability set by its surface energy density and pressure.
Recent work explores how modified geometries change this picture, using lower-dimensional BTZ spacetimes and quantum-gravity-inspired corrections such as noncommutativity or a minimum length. These affect observables such as the shadow, which may differ from that of a black hole and help test for the presence of a horizon.
M.A. Anacleto, A.T.N. Silva and L. Casarini, 2026, "Shadow of a Noncommutative Thin-Shell Gravastar", Ann. Phys. 494, 170697; arXiv:2605.03897. [arXiv; inSPIRE]
M.A. Anacleto, A.T.N. Silva and L. Casarini, 2026, "Thin-shell gravastar model in a BTZ geometry with minimum length", Phys. Lett. B 876, 140387; arXiv:2504.03824. [arXiv; inSPIRE]
A.T.N. Silva, M.A. Anacleto and L. Casarini, 2024, "Thin-shell gravastar in a noncommutative BTZ geometry", Phys. Dark Univ. 44, 101479; arXiv:2310.08852. [arXiv; inSPIRE]
Rastall gravity
Rastall gravity
Rastall's theory modifies general relativity by dropping the conservation of the stress-energy tensor: its covariant divergence no longer vanishes, but is proportional to the gradient of the Ricci scalar. The motivation is to investigate a possible non-minimal coupling between matter fields and geometry, which may represent an effective description of quantum gravity effects.
The theory can be tested in very different regimes. In neutron stars, realistic equations of state place a conservative bound of about 1% on deviations from general relativity. In cosmology, coupling the theory to a barotropic fluid gives a class of bouncing solutions that reproduce some features of loop quantum cosmology.
A.M. Oliveira, H.E.S. Velten, J.C. Fabris and L. Casarini, 2015, "Neutron Stars in Rastall Gravity", Phys. Rev. D 92, 044020; arXiv:1506.00567. [arXiv; inSPIRE]
G.F. Silva, O.F. Piattella, J.C. Fabris, L. Casarini and T.O. Barbosa, 2013, "Bouncing solutions in Rastall's theory with a barotropic fluid", Grav. Cosmol. 19, 156; arXiv:1212.6954. [arXiv; inSPIRE]
Miscellaneous
Miscellaneous
Surveys
Surveys
Understanding the accelerated expansion of the universe and the nature of dark energy and dark matter requires large dedicated projects. Space missions such as Euclid measure the shapes and redshifts of billions of galaxies to reconstruct the expansion history and the growth of structure. Photometric surveys with many narrow-band filters obtain low-resolution spectra for every source, giving precise redshifts and source classification, while pathfinder surveys validate instruments and analysis before the full survey begins.
Instrumentation is just as central to CMB studies. SPOrt and BaR-SPOrt were designed to measure the polarization of the CMB, and the work on them built expertise in controlling systematics, foregrounds and calibration.
S. Bonoli, A. Marín-Franch, J. Varela et al., 2021, "The miniJPAS survey: a preview of the Universe in 56 colours", Astron. Astrophys. 653, A31; arXiv:2007.01910. [arXiv; ADS]
L. Amendola, S. Appleby, A. Avgoustidis et al., 2018, "Cosmology and Fundamental Physics with the Euclid Satellite", Living Rev. Relativ. 21, 2; arXiv:1606.00180. [arXiv; ADS]
L. Amendola, S. Appleby, D. Bacon et al., 2013, "Cosmology and fundamental physics with the Euclid satellite", Living Rev. Relativ. 16, 6; arXiv:1206.1225. [arXiv; ADS]
E. Carretti, S. Cortiglioni, G. Bernardi et al., 2005, "The BaR-SPOrt experiment: measuring the CMBP E-mode power spectrum from Dome C", EAS Publ. Ser. 14, 81. [ADS]
S. Cortiglioni, G. Bernardi, E. Carretti et al., 2004, "The Sky Polarization Observatory", New Astron. 9, 297; arXiv:astro-ph/0401193. [arXiv; ADS]
Reviews and community reports
Reviews and community reports
Understanding the nature of dark matter (DM) is one of the main scientific goals of the coming decade. Community reports take stock of national research efforts and set priorities, arguing for a varied, long-term portfolio of experiments across scales and detection methods, targeting WIMPs, axions and other low-mass candidates. Large facilities are the flagship efforts, but smaller experiments matter too, and sustained support for the groups behind them is essential.
Review-style and conference work consolidates the theoretical and computational foundations of cosmology. Lecture notes on the cosmic microwave background (CMB) explain the physics behind its main features, which underpins the interpretation of constraints on dark matter, dark energy and other cosmological parameters. Complementary notes and proceedings cover numerical simulations of the dark universe, in particular how N-body and hydrodynamical simulations are used to obtain high-accuracy matter power spectra at high redshift in dynamical dark energy models.
I.F.M. Albuquerque, J. Alcaniz, A. Alves et al., 2025, "Brazilian Report on Dark Matter 2024"; arXiv:2504.16228. [arXiv; inSPIRE]
E. Abdalla, I.F.M. Albuquerque, A. Alves et al., 2019, "Brazilian Community Report on Dark Matter"; arXiv:1912.10076. [arXiv; inSPIRE]
D. Wands, O.F. Piattella and L. Casarini, 2016, "Physics of the Cosmic Microwave Background Radiation", Astrophys. Space Sci. Proc. 45, 3; arXiv:1504.06335. [arXiv; ADS]
H. Velten and L. Casarini, 2014, "Numerical Simulations of the dark universe", in Structure formation in an expanding universe, 203, EDUFES. [inSPIRE]
S.A. Bonometto, L. Casarini, A.V. Macciò and G. Stinson, 2010, "High precision spectra at large redshift for dynamical DE cosmologies", J. Phys.: Conf. Ser. 259, 012025; arXiv:1009.2964. [arXiv; ADS]
L. Casarini, A.V. Macciò, S.A. Bonometto, 2010, "High accuracy Spectra at high z in Dynamical Dark Energy simulations", AIP Conf. Proc. 1241, 759. [ADS]
L. Casarini, A.V. Macciò, S.A. Bonometto, 2009, "High accuracy Power Spectra at high redshift in Dynamical Dark Energy simulations", Nucl. Phys. B Proc. Suppl. 194, 185. [ADS]
S.A. Bonometto, L. Casarini, L.P.L. Colombo and R. Mainini, 2007, "Cosmologies with dynamical and coupled Dark Energy vs. CMB data", in Cosmic Polarization, 241, Research Signpost; astro-ph/0612672. [arXiv]
Codes and catalogues
Codes and catalogues
Alongside the papers, this page links to public software and data products that support the research and can be reused by the community.
CAMB (Code for Anisotropies in the Microwave Background) is a widely used code for computing the CMB and matter power spectra for a given cosmological model. Its public releases are archived on Zenodo, so that results can be reproduced with a specific version of the code. A contribution to the code is the implementation of the PKequal recipe for the nonlinear matter power spectrum in dark energy models, based on the mapping between constant-w and time-varying equations of state.
A VizieR catalogue with the results of the miniJPAS star-galaxy classification is also available.
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