arXiv subjects

Diana López Nacir

Publications and source records attributed to Diana López Nacir.

At least 19 recordsLinked to original sources

arXiv2026

Spin-1 Ultralight Dark Matter under Cosmological Scrutiny: Mass Constraints from CMB and Distance Probes

We present cosmological constraints on spin-1 ultralight dark matter, described by a vector field (VFDM) with mass $m_{\rm A}$, using Planck CMB data and geometrical probes from BAO and SNIa. A key theoretical result is the derivation of the full CMB temperature covariance matrix, including both diagonal and off-diagonal anisotropic contributions induced by the preferred direction of the background vector field. We first constrain the model using the diagonal part of the covariance, together with CMB lensing; the off-diagonal terms, which couple multipoles with $Δ\ell\in\{2,4\}$, could bias lensing reconstruction, but only at very low multipoles ($L=\{2,4\}$) not included in the Planck likelihood. We consider both a pure VFDM scenario and a mixed VFDM+CDM scenario, characterized by the fraction $f=Ω_{\rm A}/(Ω_{\rm A}+Ω_{\rm cdm})$, obtaining $\log_{10}(m_{\rm A}/\mathrm{eV})>-24.07$ (95\% C.L.) in the pure case, and a clear correlation between $f$ and $m_{\rm A}$ in the mixed case, with smaller fractions allowing lighter masses; standard cosmological parameters remain fully consistent with $Λ$CDM. For the off-diagonal contributions, we derive the corresponding Bipolar Spherical Harmonic (BipoSH) coefficients and predict their amplitude using our best-fit and bounds. While the anisotropic signal is difficult to detect in the pure VFDM scenario with current Planck data, mixed VFDM+CDM models can produce signals at, or above, Planck sensitivity over a range of multipoles, motivating dedicated searches for this characteristic signature.

astro-ph.CO↗

arXiv2026

Sensitivity of binary pulsar timing to spin-0 and spin-1 ultralight dark matter

If dark matter consists of ultralight bosons, on galactic scales it can be effectively described as a coherent classical field experiencing oscillations. Such a field could perturb the dynamics of celestial bodies via a direct coupling to ordinary matter, introducing signatures detectable through high-precision pulsar timing analysis. In this work, we extend a two-step Bayesian inference framework, originally developed for linearly coupled scalar ultralight dark matter (ULDM), to probe a quadratic scalar coupling and spin-1 vector dark matter. By explicitly marginalising over nuisance orbital parameters, our approach provides robust sensitivity limits that avoid the artificial overestimation often associated with direct fitting techniques. For quadratic scalar ULDM, we establish new constraints on the coupling $β$ for masses between $2 \times 10^{-22}$ eV and $2 \times 10^{-21}$ eV inaccessible to other experiments, while identifying mass regimes where the sensitivity is dominated by the orbital phase $Ψ'$ or the projected semi-major axis $x$. For vector ULDM, we characterize resonant signatures present even in circular orbits and obtain bounds on the coupling $g$ within the $10^{-23}$ eV to $10^{-18}$ eV range, yielding results within the same orders of magnitude as current laboratory and space-based experiments.

astro-ph.CO↗

arXiv2026

Cosmological Gravitational Waves from Ultralight Vector Dark Matter

We compute the abundance of cosmological gravitational waves produced during the evolution of an ultralight vector (spin-1) dark matter field. A homogeneous background vector field breaks spatial isotropy, requiring a Bianchi I geometry and inducing a mixing between the scalar, vector, and tensor perturbation sectors. We derive the perturbation equations in this background and show that, as a consequence of this mixing, scalar perturbations act as a source of tensor modes, generating a stochastic GW background. The production and cosmological evolution of these gravitational waves are implemented in \texttt{class.VFDM}, a modified version of \texttt{CLASS}, from which we obtain the present-day spectrum.

astro-ph.CO↗

arXiv2026

Latin American HECAP Physics Briefing Book 2025

The first process for the Latin American Strategy Forum for Research Infrastructure for High Energy, Cosmology and Astroparticle Physics (LASF4RI-HECAP) came to a conclusion in October 2020, with a Physics Briefing Book (PBB) presented in (2104.06852). Here we present an updated PBB, the result of the first update of LASF4RI-HECAP. The update process began with a call for White Papers from the HECAP community. The submitted contributions were presented at the III LASF4RI for HECAP Symposium: Update of the Strategic Plan, held at ICTP-SAIFR in São Paulo in August 26-29, 2024, with the participation of the Preparatory Group, High Level Strategy Group, Funding Agencies and representatives of similar efforts from around the globe. This updated PBB was written by the Preparatory Group based mainly on 46 White Papers submitted by the community and is organized around seven working groups: Astronomy, Astrophysics and Astroparticle Physics; Cosmology; Dark Matter; Neutrinos; Electroweak and Strong Interactions, Higgs Physics, CP and Flavour Physics and BSM; Instrumentation and Computing; Advanced Training and Capacity Building. It is intended to provide the essential input for the creation of a long-term HECAP strategy in the region.

hep-ex↗

arXiv2025

Gravitational waves of quasi-circular, inspiraling black hole binaries in an ultralight vector dark-matter environment

The gravitational waves emitted by massive black hole binaries can be affected by a variety of environmental effects, which, if detected, could inform astrophysics and cosmology. We here study how gravitational waves emitted by black holes in quasi-circular orbits are affected by the presence of an ultra-light, vector-field, dark-matter environment that is minimally coupled to the binary. This dark-matter environment induces oscillatory gravitational potentials that perturb the orbit of the binary, leaving an imprint in the binary's binding energy, and thus, on the gravitational waves emitted. We here compute the effect of this environment on the gravitational-wave phase using the stationary-phase approximation within the post-Newtonian formalism. We then perform a Fisher analysis to estimate the detectability of this environmental effect with a four-year LISA observation, focusing on vector fields with ultra-light masses in the $(10^{-19}, 10^{-16}) \; \rm{eV}$ range. We conclude that the observation of such gravitational waves with space-borne interferometers, like LISA, could yield a measurement or constraint on local, vector dark-matter environments, provided the dark-matter density is larger than roughly $10^{14} \rm{M}_\odot/{\rm{pc}}^3$.

astro-ph.CO↗

arXiv2025

Deep Neural Networks Hunting Ultra-Light Dark Matter

Ultra-light dark matter (ULDM) is a compelling candidate for cosmological dark matter. If ULDM interacts with ordinary matter, it can induce measurable, characteristic signals in pulsar-timing data because it causes the orbits of pulsars in binary systems to osculate. In this work, we investigate the potential of machine learning (ML) techniques to detect such ULDM signals. To this end, we construct three types of neural networks: an autoencoder, a binary classifier, and a multiclass classifier. We apply these methods to four theoretically well-motivated ULDM models: a linearly coupled scalar field, a quadratically coupled scalar field, a vector field and a tensor field. We show that the sensitivity achieved using ML methods is comparable to that of a semi-analytical Bayesian approach, which to date has only been applied to the linear scalar case. The ML approach is readily applicable to all four ULDM models and, in the case of the multiclass classifier, can distinguish between them. Our results, derived from simulated data, lay the foundation for future applications to real pulsar-timing observations.

astro-ph.HE↗

arXiv2025

Cosmological perturbations with ultralight vector dark matter fields: numerical implementation in CLASS

In this work we consider a dark matter candidate described by an ultralight vector field, whose mass is in principle in the range $H_{\rm{eq}}\sim 10^{-28}\rm{eV}\ll m< \rm{eV}$. The homogeneous background vector field is assumed to point in a given direction. We present a numerical implementation of cosmological perturbations in a Bianchi type I geometry with vector field dark matter in a modified version of the Cosmic Linear Anisotropy Solving System (CLASS). We study the evolution of large-scale cosmological perturbations in the linear regime. We compute the matter power spectrums defined for Fourier modes pointing in a given direction. We obtain interesting features in the power spectrums whose observational significance depends on the field mass. We compare the results with the standard $\rm{ΛCDM}$ and with the corresponding well-studied ultralight scalar field dark matter case. As for the scalar case we obtain a suppression in the power spectrums at small scales characterized by the same scale, namely the Jeans scale. The main characteristic feature of the vector field model we notice here for first time is that the amplitude of the suppression effect depends on the direction of the Fourier modes with respect to the background vector field, leaving eventually a possible anisotropic imprint in structure formation at small scales.

astro-ph.CO↗

arXiv2024

Constraints on conformal ultralight dark matter couplings from the European Pulsar Timing Array

Millisecond pulsars are extremely precise celestial clocks: as they rotate, the beamed radio waves emitted along the axis of their magnetic field can be detected with radio telescopes, which allows for tracking subtle changes in the pulsars' rotation periods. A possible effect on the period of a pulsar is given by a potential coupling to dark matter, in cases where it is modeled with an "ultralight" scalar field. In this paper, we consider a universal conformal coupling of the dark matter scalar to gravity, which in turn mediates an effective coupling between pulsars and dark matter. If the dark matter scalar field is changing in time, as expected in the Milky Way, this effective coupling produces a periodic modulation of the pulsar rotational frequency. By studying the time series of observed radio pulses collected by the European Pulsar Timing Array experiment, we present constraints on the coupling of dark matter, improving on existing bounds. These bounds can also be regarded as constraints on the parameters of scalar-tensor theories of the Fierz-Jordan-Brans-Dicke and Damour-Esposito-Farèse types in the presence of a (light) mass potential term.

astro-ph.HE↗

arXiv2024

Ultralight vector dark matter, anisotropies and cosmological adiabatic modes

In this work we study the early time behavior and the background evolution of ultralight vector dark matter. We present a model for vector dark matter in an anisotropic Bianchi type I universe. Vector fields source anisotropies in the early universe characterized by a shear tensor which rapidly decays once the fields start oscillating, making them viable dark matter candidates. We present the set of equations needed to evolve scalar cosmological perturbations in the linear regime, both in synchronous gauge and Newtonian gauge. We show that the shear tensor has to be taken into account in the calculation of adiabatic initial conditions.

astro-ph.CO↗

arXiv2024

Bayesian sensitivity of binary pulsars to ultra-light dark matter

Ultra-light dark matter perturbs the orbital motion of binary pulsars, in particular by causing peculiar time variations of a binary's orbital parameters, which then induce variations in the pulses' times-of-arrival. Binary pulsars have therefore been shown to be promising detectors of ultra-light dark matter. To date, the sensitivity of binary pulsars to ultra-light dark matter has only been studied for dark matter masses in a narrow resonance band around a multiple of the binary pulsar orbital frequency. In this study we devise a two-step, bayesian method that enables us to compute semi-analytically the sensitivity for all masses, also away from the resonance, and to combine several observed binaries into one global sensitivity curve. We then apply our method to the case of a universal, linearly-coupled, scalar ultra-light dark matter. We find that with next-generation radio observatories the sensitivity to the ultra-light dark matter coupling will surpass that of solar-system constraints for a decade in mass around $m\sim10^{-21}$ $\text{eV}$, even beyond resonance.

astro-ph.HE↗

arXiv2022

Self-Interacting Dark Matter in Cosmology: accurate numerical implementation and observational constraints

This paper presents a systematic and accurate treatment of the evolution of cosmological perturbations in self-interacting dark matter models, for particles which decoupled from the primordial plasma while relativistic. We provide a numerical implementation of the Boltzmann hierarchies developed in a previous paper [JCAP, 09 (2020) 041] in a publicly available Boltzmann code and show how it can be applied to realistic DM candidates such as sterile neutrinos either under resonant or non-resonant production mechanisms, and for different field mediators. At difference with traditional fluid approximations -- also known as a $c_{\rm eff}-c_{\rm vis}$ parametrizations -- our approach follows the evolution of phase-space perturbations under elastic DM interactions for a wide range of interaction models, including the effects of late kinetic decoupling. Finally, we analyze the imprints left by different self interacting models on linear structure formation, which can be constrained using Lyman-$α$ forest and satellite counts. We find new lower bounds on the particle mass that are less restrictive than previous constraints.

astro-ph.CO↗

arXiv2021

The Role of Self Interactions in the Cosmological Evolution of Warm Dark Matter

In this work we present a summary of recent studies on the effects of elastic self interactions in the evolution of Warm Dark Matter models (WDM), focusing on structure formation and the evolution of cosmological perturbations. We pay special attention to a particular class of sterile neutrino WDM known as $ν$MSM and provide examples for the case of vector field self interactions. We calculate the effects of assuming self interacting dark matter in X-Ray astrophysical observations, in the formation of fermionic DM halos in (quasi) equilibrium states and in the evolution of DM perturbations in the early universe, assuming particle masses between $\mathcal{O}(1-100)$ keV. In the latter topic, we perform simulations using a modification to the public Boltzmann solver CLASS and compare our results with observations. We find self interactions to be an interesting addition to WDM models, which can alleviate tensions both present in standard CDM cosmology and regarding WDM itself, as well as provide an interesting avenue for DM halo formation.

astro-ph.CO↗

arXiv2021

Searching for spin-2 ULDM with gravitational waves interferometers

The detection of gravitational waves from merging binaries has ushered in the era of gravitational wave interferometer astronomy. Besides these strong, transient, calamitous events, much weaker signals can be detected if the oscillations are nearly monochromatic and "continuous", that is, coherent over a long time. In this work we show that ultra-light dark matter of spin two, owing to its universal coupling $α$ to Standard Model fields, generates a signal that is akin to but distinct from a continuous gravitational wave. We show that this signal could be detected with current and planned gravitational wave interferometers. In the event of a null detection, current facilities could constrain the coupling to be below $α\sim10^{-7}$ for frequencies of tens of Hz, corresponding to dark matter masses around the $10^{-13}$ eV mark. Future facilities could further lower these upper limits and extend them to smaller masses down to $10^{-18}$ eV. These limits would be the most stringent bounds on the spin-2 Yukawa fifth force strength, parametrised by $α$, in the frequency ranges accessible by gravitational wave interferometers. The implementation of this type of searches for gravitational wave interferometers would therefore further our grasp of both dark matter and gravity.

astro-ph.CO↗

arXiv2020

Boltzmann hierarchies for self-interacting warm dark matter scenarios

We provide a general framework for self-interacting warm dark matter (WDM) in cosmological perturbations, by deriving from first principles a Boltzmann hierarchy which retains certain independence from a particular interaction Lagrangian. We consider elastic interactions among the massive particles, and obtain a hierarchy which is more general than the ones usually obtained for non-relativistic (as for cold DM) or for ultra-relativistic (as for neutrinos) approximations. The more general momentum-dependent kernel integrals in the Boltzmann collision terms, are explicitly calculated for different field-mediator models, including examples of a scalar field (either massive or massless) or a massive vector field. As an application, we study the evolution of the interaction rate per particle under the relaxation time approximation, and assess when a given self-interaction is relevant in comparison with the Hubble expansion rate. Our framework aims to be a useful starting point to evaluate DM self-interaction effects in the linear power spectrum, necessary to then study its evolution all the way to non-linear stages of structure formation, where certain DM interactions were proven to be relevant.

astro-ph.CO↗

arXiv2020

Pulsar timing array constraints on spin-2 ULDM

Ultra-light Dark Matter (ULDM) models are suitable candidates for the cosmological Dark Matter that may leave characteristic imprints in many observables. Among other probes, signatures of ULDM can be searched for in pulsar timing data. In this work we describe the effects of spin-2 ULDM on pulsar timing arrays, extending previous results on lower spins. Spin-2 ULDM is universally coupled to standard matter with dimensionless strength $α$. We estimate that current data could constrain this coupling in the mass range $m\lesssim4\times10^{-22}$ eV at the $10^{-5}$ to $10^{-6}$ level, which is the most competitive constraint in this mass range. A crucial feature of the spin-2 ULDM effect on pulsar timing is its anisotropic, quadrupolar shape. This feature can be instrumental in differentiating the effects sourced by spin-2 ULDM from, for instance, scalar ULDM, and the systematics of a PTA experiment.

astro-ph.CO↗

arXiv2020

Secular effects of Ultralight Dark Matter on Binary Pulsars

Dark matter (DM) can consist of very light bosons behaving as a classical scalar field that experiences coherent oscillations. The presence of this DM field would perturb the dynamics of celestial bodies, either because the (oscillating) DM stress tensor modifies the gravitational potentials of the galaxy, or if DM is directly coupled to the constituents of the body. We study secular variations of the orbital parameters of binary systems induced by such perturbations. Two classes of effects are identified. Effects of the first class appear if the frequency of DM oscillations is in resonance with the orbital motion; these exist for general DM couplings including the case of purely gravitational interaction. Effects of the second class arise if DM is coupled quadratically to the masses of the binary system members and do not require any resonant condition. The exquisite precision of binary pulsar timing can be used to constrain these effects. Current observations are not sensitive to oscillations in the galactic gravitational field, though a discovery of pulsars in regions of high DM density may improve the situation. For DM with direct coupling to ordinary matter, the current timing data are already competitive with other existing constraints in the range of DM masses $\sim 10^{-22}-10^{-18}\,{\rm eV}$. Future observations are expected to increase the sensitivity and probe new regions of parameters.

gr-qc↗

arXiv2020

Binary Pulsars as probes for Spin-2 Ultralight Dark Matter

Binary pulsars can be excellent probes of ultra-light dark matter. We consider the scenario where the latter is represented by a spin-2 field. The coherent oscillations of the dark matter field perturb the dynamics of binary systems, leading to secular effects for masses that resonate with the binary systems. For the range $10^{-23}$eV $\lesssim m \lesssim 10^{-17}$eV we show that current timing data could potentially constrain the universal coupling strength of dark matter to ordinary matter at the level of $α\simeq 10^{-5}$.

astro-ph.HE↗

arXiv2019

To the sphere and back again: de Sitter infrared correlators at NTLO in 1/N

We analyze the infrared behavior of the two and four-point functions for the massless $O(N)$ model in Lorentzian de Sitter spacetime, using the $1/N$ expansion. Our approach is based in the study of the Schwinger-Dyson equations on the sphere (Euclidean de Sitter space), using the fact that the infrared behavior in Lorentzian spacetime is determined by the pole structure of the Euclidean correlation functions. We compute the two-point function up to the NTLO in $1/N$, and show that in the infrared it behaves as the superposition of two massive free propagators with effective masses of the same order, but not equal to, the dynamical mass $m_{dyn}$. We compare our results with those obtained using other approaches, and find that they are equivalent but retrieved in a considerably simpler way. We also discuss the infrared behavior of the equal-times four-point functions.

hep-th↗