arXiv subjects

Nicola Tamanini

Publications and source records attributed to Nicola Tamanini.

At least 19 recordsLinked to original sources

arXiv2026

Spectral sirens cosmology from binary black holes populations with sharper mass features

Spectral-sirens inference enables the extraction of cosmological parameters from gravitational-wave data alone, without electromagnetic counterparts or galaxy catalogs. We introduce new parametric mass functions for the binary black hole population built as linear combination of truncated power-laws that capture significant structure across the mass spectrum. On analysing the latest gravitational-wave transient catalog, GWTC-4.0, we show that power-laws-only population models constrain the Hubble constant to $H_0 = 53.3^{+14.0}_{-10.8} ~\rm km \,s^{-1} \,Mpc^{-1}$ at $68\%$ confidence level. After probing the robustness of the results with respect to several modelling assumptions, we further test alternative cosmological models, establishing competitive constraints on modified gravitational-wave propagation, while bounds on the dark energy equation-of-state parameters remain uninformative. Projecting to the future O5 observing run with larger datasets at higher redshifts, we forecast substantial improvements in $H_0$ and modified propagation parameters. Our results highlight the strong interplay between the black hole mass distribution and inferred cosmology.

gr-qc↗

arXiv2026

GUEST: Gravitational Universe Exploration with Satellite Tracking. A passive satellite laser-ranging mission for the dark gravitational Universe

GUEST is a space mission concept whose central objective is the detection of gravitational waves (GWs) in the microhertz band -- a physics-rich frequency window that no other present or planned detector can reach at a significant level. The concept is simple: two dense, passive spheres, covered with cube-corner retroreflectors, deployed in {highly eccentric} Earth orbits ($e \gtrsim 0.7$, period $P \gtrsim 33$ h), tracked continuously by the global network of satellite laser-ranging stations over a minimum observation time of 10 years, with an expected total duration of 30 years. The orbits themselves act as resonant detectors of the oscillating gravitational perturbations, with the microhertz sensitivity emerging from the selected orbital parameters. From the same data stream, GUEST delivers a programme of fundamental and applied science that cuts across particle physics, gravitational-wave astronomy, cosmology, astrophysics, and geodesy: the first coherent search for GWs from supermassive black-hole binaries in the $μ$Hz band, the exploration of primordial GW backgrounds in the unexplored energy-scale gap between pulsar-timing arrays and LISA, a dedicated probe of ultra-light dark matter in a parameter region untouched by any other experiment, a new way to search for ultra-light bosons, order-of-magnitude-improved tests of new gravitational interactions at astronomical ranges, and a step change in the absolute determination of $GM_\oplus$ that underpins the Global Geodetic Observing System and future navigation and Earth-observation missions. This white paper presents the motivation, scientific reach, and mission concept of GUEST.

astro-ph.CO↗

arXiv2026

Waveform Modelling for the Laser Interferometer Space Antenna

LISA, the Laser Interferometer Space Antenna, will usher in a new era in gravitational-wave astronomy. As the first anticipated space-based gravitational-wave detector, it will expand our view to the millihertz gravitational-wave sky, where a spectacular variety of interesting new sources abound: from millions of ultra-compact binaries in our Galaxy, to mergers of massive black holes at cosmological distances; from the beginnings of inspirals that will venture into the ground-based detectors' view to the death spiral of compact objects into massive black holes, and many sources in between. Central to realising LISA's discovery potential are waveform models, the theoretical and phenomenological predictions of the pattern of gravitational waves that these sources emit. This white paper is presented on behalf of the Waveform Working Group for the LISA Consortium. It provides a review of the current state of waveform models for LISA sources, and describes the significant challenges that must yet be overcome.

gr-qc↗

arXiv2026

Emergent structure in the binary black hole mass distribution and implications for population-based cosmology

Gravitational waves provide a powerful probe of both the astrophysical processes driving black hole mergers and the dynamics of the Universe, but these measurements rely on accurately inferring the unknown underlying population. We perform an agnostic reconstruction of the primary mass distribution using B-splines, characterising the emergence of structure with increasing model complexity. Using the latest gravitational-wave transient catalog, GWTC-4.0, we identify multiple mass features and find evidence suggesting a logarithmic hierarchy in the population. We show that this structure directly impacts measurements of the Hubble constant, primarily through features at the population boundaries. Finally, we introduce an approach that isolates a subpopulation of low-mass events to mitigate modelling systematics, providing a promising path toward robust population-based cosmology with future datasets.

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arXiv2026

Reducing cosmological degeneracies by combining multiple classes of LISA gravitational-wave standard sirens

We present the first joint gravitational-wave cosmological inference with LISA extreme mass-ratio inspirals at $z\lesssim1$ (galaxy redshifts) and massive black hole binaries at $z\gtrsim1$ (electromagnetic counterparts). Combining these standard sirens reduces cosmological degeneracies and yields competitive constraints on the Hubble constant $H_0$ and the dark-energy equation-of-state parameter $w_0$. This highlights LISA's potential for late-time cosmology across a broad redshift range with systematics distinct from electromagnetic distance indicators.

astro-ph.CO↗

arXiv2026

Probing Cosmic Expansion and Early Universe with Einstein Telescope

Over the next two decades, gravitational-wave (GW) observations are expected to evolve from a discovery-driven endeavour into a precision tool for astrophysics, cosmology, and fundamental physics. Current second-generation ground-based detectors have established the existence of compact-binary mergers and enabled GW multi-messenger astronomy, but they remain limited in sensitivity, redshift reach, frequency coverage, and duty cycle. These limitations prevent them from addressing many fundamental open questions in cosmology. By the 2040s, wide-field electromagnetic surveys will have mapped the luminous Universe with unprecedented depth and accuracy. Nevertheless, key problems including the nature of dark matter, the physical origin of cosmic acceleration, the properties of gravity on cosmological scales, and the physical conditions of the earliest moments after the Big Bang will remain only partially constrained by electromagnetic observations alone. Progress on these fronts requires access to physical processes and epochs that do not emit light. Gravitational waves provide a unique and complementary observational channel: they propagate over cosmological distances largely unaffected by intervening matter, probe extreme astrophysical environments, and respond directly to the geometry of spacetime. In this context, next-generation GW observatories such as the Einstein Telescope (ET) will be transformative for European astronomy. Operating at sensitivities and frequencies beyond existing detectors, ET will observe binary black holes and neutron stars out to previously inaccessible redshifts, enable continuous high signal-to-noise monitoring of compact sources, and detect gravitational-wave backgrounds of astrophysical and cosmological origin. Together with space-based detectors, ET will play a central role in advancing our understanding of cosmic evolution and fundamental physics.

astro-ph.CO↗

arXiv2025

A Parametrized Test of General Relativity for LISA Massive Black Hole Binary Inspirals

Laser Interferometer Space Antenna (LISA) observations of massive black hole binaries (MBHBs) will provide long duration inspiral signals with high signal-to-noise ratio (SNR) data, ideal for testing general relativity (GR) in the strong-field and relativistic regime regime. We present an extension of the Flexible Theory-Independent (FTI) framework, adapted to gravitational waves (GWs) from MBHBs observed with LISA, to perform parametrized inspiral tests of GR. This approach introduces generic deviations to the post-Newtonian (PN) coefficients of the frequency-domain GW phase while accounting for the time- and frequency-dependent instrument response, thus effectively identifying potential deviations from GR by constraining modifications to the PN phasing formula. Complementary analyses using Fisher matrix and full Bayesian approaches confirm that LISA observations could improve constraints on agnostic, scale-independent deviations from GR by at least two orders of magnitude compared to the most recent LIGO-Virgo-KAGRA measurements. Since LISA's sensitivity to different GW phases -- inspiral, merger, and ringdown -- varies across the MBHB parameter space with masses between $10^4$ and $10^7M_{\odot}$, the optimal regime for testing agnostic deviations is not known a priori. Our results illustrate how the strength of these constraints depends significantly on both the total mass and the SNR, reflecting the trade-off between inspiral and merger-ringdown contributions to the observed signal. We also investigate the interplay between inspiral-only versus inspiral-merger-ringdown analyses in constraining these inspiral deviation parameters. This work contributes to the development of robust tests of GR with LISA, enhancing our ability to probe the nature of gravity and BHs with GW observations.

gr-qc↗

arXiv2025

Listening Across the Cosmic Time: Standard Sirens from Ground- and Space-Based Missions in the Next Decade

Precise measurement of the Hubble parameter will enable stringent tests of the standard model for cosmology. Standard sirens, using the luminosity distances measured by gravitational-wave observations of compact binary mergers, are expected to provide such measurements independently in the next decade. With the ground- and space-based gravitational wave observatories, the LIGO-Virgo-KAGRA (LVK) network and the Laser Interferometer Space Antenna (LISA), different types of standard sirens altogether will place constraints across a wide redshift range. In this paper, we forecast the precisions of standard siren Hubble parameter measurements and compare various scenarios, accounting for the dominant sources of systematic uncertainty. Specifically, we find a $2\%$ constraint on $H_0$, a $1.5-3\%$ constraint on $H(z)$ at $z=1$, and a $3-5\%$ constraint on $H(z)$ at $z=7$ when combining LVK and LISA standard sirens with precise redshift measurements from electromagnetic counterpart observations. We do not find a significant improvement when including standard sirens with no EM counterpart, but which rely on features in the black hole mass distribution, and the potential systematics introduced by the possible redshift evolution of such features could further degrade the measurement accuracy if not properly accounted for.

astro-ph.CO↗

arXiv2025

Towards a few percent measurement of the Hubble constant with the current network of gravitational wave detectors without using electromagnetic information

Gravitational waves provide a novel and independent measurement of cosmological parameters, offering a promising avenue to address the Hubble tension alongside traditional electromagnetic observations. In the absence of electromagnetic counterparts or complete host galaxy catalogs, current measurements rely on population-based methods that statistically combine black hole merger events. Building on recent models that incorporate additional structure in the primary black hole mass distribution, using public data from the LIGO-Virgo-KAGRA (LVK) collaboration third observing run (O3), we obtain a 30% accuracy improvement on the measurement of the Hubble constant with respect to the result reported by LVK with the third GW transient catalog (GWTC-3). Employing a realistic simulation that includes full Bayesian single-event inference, we present forecasts for the upcoming LVK observational runs, O4 and O5. Using a three power-law mass model, we project a measurement of the Hubble constant with 20% accuracy at O4 sensitivity, improving to 2.7% accuracy at O5 sensitivity. Our findings demonstrate the potential for gravitational waves to provide a substantial contribution to solving the Hubble tension within the next decade of observations.

gr-qc↗

arXiv2025

Science of the LISA mission: A Summary for the European Strategy for Particle Physics

The LISA mission is an international collaboration between ESA, its member states, and NASA, for the detection of gravitational waves from space. It was adopted in January 2024 and is scheduled for launch in the mid-2030's. It will be a constellation of three identical spacecraft forming a near-equilateral triangle in an heliocentric orbit, transferring laser beams over $2.5 \cdot 10^6$ km long arms. Laser interferometry is used to track separations between test masses, thus measuring spacetime strain variations as a function of time. LISA Science Objectives tackle many open questions in astrophysics, fundamental physics and cosmology, including ESA's Cosmic Vision questions "What are the fundamental laws of the universe?" and "How did the universe originate and of what is it made?". In this contribution, based on the LISA Red Book, we present a summary of the LISA Science Objectives relevant for the European Strategy for Particle Physics.

gr-qc↗

arXiv2025

Hierarchical Bayesian inference on an analytical model of the LISA massive black hole binary population

Massive black hole binary (MBHB) mergers will be detectable in large numbers by the Lisa Interferometer Space Antenna (LISA), which will thus provide new insights on how they form via repeated dark matter (DM) halo and galaxy mergers. Here we present a simple analytical model to generate a population of MBHB mergers based on a theoretical prescription that connects them to DM halo mergers. The high flexibility of our approach allows us to explore the broad and uncertain range of MBH seeding and growth mechanisms, as well as the different effects behind the interplay between MBH and galactic astrophysics. Such a flexibility is fundamental for the successful implementation and optimisation of the hierarchical Bayesian parameter estimation approach that here we apply to the MBHB population of LISA for the first time. Our inferred population hyper-parameters are chosen as proxies to characterise the MBH--DM halo mass scaling relation, the occupation fraction of MBHs in DM halos and the delay between halo and MBHB mergers. We find that LISA will provide tight constraints at the lower-end of the MBH-halo scaling relation, well complementing EM observations which are biased towards large masses. Furthermore, our results suggest that LISA will constrain some features of the MBH occupation fraction at high redshift, as well as merger time delays of the order of a few hundreds of Myr, opening the possibility to constrain dynamical evolution time scales such as the dynamical friction. The analysis presented here constitutes a first attempt at developing a hierarchical Bayesian inference approach to the LISA MBHB population, opening the way for several further improvements and investigations.

astro-ph.CO↗

arXiv2025

Blinded Mock Data Challenge for Gravitational-Wave Cosmology-I: Assessing the Robustness of Methods Using Binary Black Holes Mass Spectrum

Gravitational Wave (GW) sources are standard sirens that provide an independent way to map the cosmic expansion history by combining with an independent redshift measurement either from an electromagnetic counterpart for a bright siren or using different statistical techniques for dark sirens. In this analysis, we perform the first Blinded Mock Data Challenge (\texttt{Blinded-MDC}) to test the robustness in inferring the value of Hubble constant $H_0$ for a dark siren technique which depends on astrophysical mass distribution of Binary Black Holes (BBHs). We have considered different analysis setups for the \texttt{Blinded-MDC} to test both statistical and systematic uncertainties and demonstrate the capabilities in inferring $H_0$ with detector sensitivity as per the fourth observation run of LIGO-Virgo-KAGRA. We find that when the astrophysical population of BBHs matches with the underlying assumption of the model, a cosmological pipeline can recover the injected parameters using the observed mass distribution. However, when the mock mass distribution of the astrophysical population depends slightly on redshift and one is ignorant about it in analyzing the data, it can cause a systematic discrepancy in the inferred value of $H_0$ by about $1.5σ$, above the statistical fluctuations due to noise and a limited number of events. In the future, elaborate studies will be required to mitigate systematic uncertainties due to unknown astrophysical complexities. This MDC framework sets the road map for inspecting the precision and accuracy of standard siren cosmology and provides the first insight into the robustness of the population-dependent cosmology inference in a blinded analysis setup.

astro-ph.CO↗

arXiv2025

Searching for additional structure and redshift evolution in the observed binary black hole population with a parametric time-dependent mass distribution

The population of the observed gravitational wave events encodes unique information on the formation and evolution of stellar-mass black holes, from the underlying astrophysical processes to the large-scale dynamics of the Universe. We use the ICAROGW analysis infrastructure to perform hierarchical Bayesian inference on the gravitational wave signals from the LIGO-Virgo-KAGRA third observing run, O3. Searching for additional structure and redshift evolution in the primary mass distribution, we explore the dependence of the mass spectrum reconstruction on different parametrizations and prior choices. For the stationary case, we find strong evidence (Bayes factor $B \simeq 180$) that the results obtained using a power-law model with a peak (Powerlaw-Gaussian)--the model preferred so far in the literature--are sensitive to prior bounds, affecting the resolvability of the $\sim 35 M_{\odot}$ peak. This behaviour is reproduced by simulated data, indicating a bimodal structure in the likelihood. Models with three mass features simultaneously capture a sharp $\sim 10M_{\odot}$ peak, a $\sim 35 M_{\odot}$ overdensity, and support for a $\sim 20 M_{\odot}$ overdensity preceded by a dip. Among these, a model with three power-law peaks (Powerlaw-Powerlaw-Powerlaw) is equally favored, in terms of evidence, over the Powerlaw-Gaussian model with wide priors. We find no statistical support for redshift evolution in the current data and provide constraints on the parameters governing this evolution, showing consistency with stationarity. We highlight possible limitations of the hierarchical Bayesian inference framework in reconstructing evolving features outside the detector horizon. Our work lays the foundations for a robust characterization of time-dependent population distributions, with significant implications for black hole astrophysics and gravitational wave cosmology.

gr-qc↗

arXiv2025

Probing modified gravitational-wave propagation with extreme mass-ratio inspirals

Extreme mass-ratio inspirals (EMRIs), namely binary systems composed of a massive black hole and a compact stellar-mass object, are anticipated to be among the gravitational wave (GW) sources detected by the Laser Interferometer Space Antenna (LISA). Similarly to compact binary mergers detected by current GW detectors, EMRIs can be used as cosmic rulers to probe the expansion of the Universe. Motivated by tensions in current cosmological observations as well as by alternative models of dark energy, modified gravity theories can affect the propagation of GWs across cosmological distances, with modifications commonly parametrised in terms of two phenomenological parameters, $Ξ_0$ and $n$. In this work we adopt a Bayesian approach to constrain for the first time parametrised deviations from General Relativity using the loudest simulated EMRIs detected by LISA as dark sirens with a simulated galaxy catalog. Assuming all the cosmological parameters except $Ξ_0$ are already tightly constrained, our forecasts show that $Ξ_0$ can be constrained to a few percent level (90% C.I.) with 4 years of LISA observations, unless EMRI detection rates turn out to be closer to current pessimistic expectations. These results quickly degrade if additional cosmological parameters are inferred simultaneously, but become more robust with an extended LISA observation period of 10 years. Overall, we find that EMRIs with LISA are better at constraining modified GW propagation than current second-generation ground-based GW detectors, but they will only be comparable to third-generation detectors in the most optimistic scenarios.

astro-ph.CO↗

arXiv2024

Massive black hole binaries in LISA: constraining cosmological parameters at high redshifts

One of the scientific objectives of the Laser Interferometer Space Antenna (LISA) is to probe the expansion of the Universe using gravitational wave observations. Indeed, as gravitational waves from the coalescence of a massive black hole binary (MBHB) carry direct information of its luminosity distance, an accompanying electromagnetic (EM) counterpart can be used to determine its redshift. This method of $bright$ $sirens$, when applied to LISA, enables one to build a gravitational Hubble diagram to high redshift. In this work, we forecast the ability of LISA-detected MBHB bright sirens to constrain cosmological models. The expected EM emission from MBHBs can be detected up to redshift $z\sim 7$ with future astronomical facilities, and the distribution of MBHBs with detectable counterpart peaks at $z\sim 2-3$. Therefore, we propose several methods to leverage the ability of LISA to constrain the expansion of the Universe at $z\sim 2-3$, a poorly charted epoch in cosmography. We find that the most promising method consists in using a model-independent approach based on a spline interpolation of the luminosity distance-redshift relation: in this case, LISA can constrain the Hubble parameter at $z\sim2-3$ with a relative precision of at least $10\%$.

astro-ph.CO↗

arXiv2023

Strongly-Lensed Extreme Mass-ratio Inspirals

In this work, we investigate detection rates and parameter estimation of strongly-lensed extreme mass-ratio inspirals (LEMRIs) in the context of the Laser Interferometer Space Antenna (LISA). Our results indicate that LEMRIs constitute a new gravitational-wave target signal for LISA, with detection rates ranging from zero to $\sim 40$ events over a four year-observation, and that it is possible to reveal and characterize LEMRIs at redshift $z \gtrsim 1$. We finally show that one LEMRI observation with identified host galaxy may yield percent constraints or better on the Hubble constant.

astro-ph.CO↗

arXiv2023

Dark siren cosmology with binary black holes in the era of third-generation gravitational wave detectors

Third-generation (3G) gravitational wave detectors, in particular Einstein Telescope (ET) and Cosmic Explorer (CE), will explore unprecedented cosmic volumes in search for compact binary mergers, providing us with tens of thousands of detections per year. In this study, we simulate and employ binary black holes detected by 3G interferometers as dark sirens, to extract and infer cosmological parameters by cross-matching gravitational wave data with electromagnetic information retrieved from a simulated galaxy catalog. Considering a standard $Λ$CDM model, we apply a suitable Bayesian framework to obtain joint posterior distributions for the Hubble constant $H_0$ and the matter energy density parameter $Ω_m$ in different scenarios. Assuming a galaxy catalog complete up to $z=1$ and dark sirens detected with a network signal-to-noise ratio greater than 300, we show that a network made of ET and two CEs can constrain $H_0$ ($Ω_m$) to a promising $0.8\%$ ($10.0\%$) at $90\%$ confidence interval within one year of continuous observations. Additionally, we find that most of the information on $H_0$ is contained in local, single-host dark sirens, and that dark sirens at $z>1$ do not substantially improve these estimates. Our results imply that a sub-percent measure of $H_0$ can confidently be attained by a network of 3G detectors, highlighting the need for characterising all systematic effects to a higher accuracy.

astro-ph.CO↗

arXiv2023

Lensing of gravitational waves from tidal disruption events

In this work, we investigate the effect of gravitational lensing on the gravitational wave (GW) signals of a population of tidal disruption events (TDEs). We estimate the number of lensed-magnified signals that we expect to detect with future space-based GW observatories, in particular LISA and DECIGO. We model the lens distribution using an hybrid approach that combines semi-analytic methods with numerical results from ray tracing simulations. We divide the TDE population in two classes, nuclear TDEs (main sequence stars tidally disrupted by massive black holes in the cores of galaxies) and globular TDEs (white dwarfs tidally disrupted by intermediate mass black holes in globular clusters). We find that, even considering the effect of lensing, LISA will not be able to observe any TDEs, while DECIGO could detect $\sim$16 strongly lensed ($μ>2$) globular TDEs and $\sim$135 strongly lensed nuclear TDEs, over an observational period of 10 years. Our results reveal the role that lensing will play in future deci-Hertz GW observatories, indicating exciting multi-messenger opportunities with TDEs but at same time signalling the need to develop adequate data analysis techniques to correctly reconstruct the astrophysical properties of the source.

astro-ph.HE↗