We present the canonical analysis of different versions of unimodular gravity defined in the Plebański formalism, based on a (generally complex) $SO(3)$ spin connection and set of (self-dual) two-forms. As in the metric formulation of unimodular gravity, one can study either a theory with fixed volume form or work in a parametrized formalism in which the cosmological constant becomes a dynamical field, constrained to be constant by the field equations. In the first case, the Hamiltonian density contains a part which is not constrained to vanish, but rather constrained to be constant, again as in the metric formulation. We also discuss reality conditions and challenges in extracting Lorentzian solutions.

Building upon the statistical formulation for parameter estimation in the presence of correlated noise proposed by Cireddu et al., we present the initial study to incorporate the effects of correlated noise into the analyses of various detector designs’ performance. We consider a two-L-shaped-detector configuration located in Europe and compare the expectation of parameter estimation of gravitational wave transients between noncollocated and hypothetical collocated configurations. In our study, we posit the existence of low-frequency correlated noise within the 5–10 Hz range for the collocated detector configuration, with a varying degree of correlation. In this specific detector setup, our observations indicate an enhancement in the precision of intrinsic parameter measurements as the degree of correlation increases. This trend suggests that higher degrees of noise correlation may beneficially influence the accuracy of parameter estimation. In particular, when the noise is highly correlated, the uncertainty on chirp mass decreases by up to 30%. The absence of an inter-European baseline does hinder the estimation of the extrinsic parameters. However, given a realistic global network with the additional detector located in the United States, the uncertainty of extrinsic parameters is significantly reduced. This reduction is further amplified as the degree of noise correlation increases. When the degree of noise correlation exceeds a certain level, the collocated configuration outperforms the noncollocated configuration. For instance, when the degree of correlation is high, the collocated configuration decreases the 90% credible area of sky location by up to 10% compared to the noncollocated configuration. We conclude that the impact of noise correlation is not trivial and can potentially alter both the quantitative and qualitative outcomes in detector performance. We therefore recommend the inclusion of noise correlation for a comprehensive assessment of the design of third-generation gravitational wave detectors.

The direct current (DC) memory is a nonoscillatory, hereditary component of the gravitational wave (GW) signal that represents one of the most peculiar manifestations of the nonlinear nature of GW emission and propagation. In this work, by transforming the results provided in harmonic coordinates and quasi-Keplerian parametrization by Ebersold et al. [Phys. Rev. D 100, 084043 (2019)], valid for nonspinning eccentric binaries, we provide the DC memory in terms of the effective-one-body (EOB) phase-space variables, up to the second and a half order in the post-Newtonian expansion and up to the sixth order in the small-eccentricity expansion. Our results are then implemented in TEOBResumS-Dalí, thus providing the first EOB model with DC memory contributions. This model is then used to assess the impact on the waveform and themain features of the DC memory, also addressing its dependence on the eccentricity of the binary system at its formation.

Gravitational wave (GW) astronomy has revolutionized our capacity to explore nature. The next generation of observatories, among which the spaceborne detector Laser Interferometer Space Antenna (LISA) is expected to yield orders of magnitude of signal-to-noise-ratio improvement and reach fainter and novel features of general relativity. Among them, an exciting possibility is the detection of GW memory. Interpreted as a permanent deformation of the background spacetime after a GW perturbation has passed through the detector, GW memory offers a novel avenue to proof-test general relativity, access the nonlinear nature of gravity, and provide complementary information to better characterize the GW source. Previous studies have shown that GW memory detection from individual mergers of massive black hole binaries is expected with LISA. However, these works have not simulated the proper time-domain response of the detector to the GW memory. This work is filling this gap and presents the detection prospects of LISA regarding GW memory and the expected signature of GW memory on the data streams using the most up-to-date LISA consortium simulations of the response. We focus on the GW memory of massive black hole binary mergers and use state-of-the-art population models to assess the likelihood of detecting the GW memory within the LISA lifetime. We conclude that GW memory will be a key feature of several events detected by LISA and will help to exploit the scientific potential of the mission fully.

We examine several dark energy models with a time-varying equation-of-state parameter, $w(z)$, to determine what information can be derived by fitting the distance modulus in such models to a constant equation of state parameter, $w_{*}$. We derive $w_{*}$ as a function of the model parameters for the Chevallier-Polarski-Linder (CPL) parametrization and for the Dutta-Scherrer approximation to hilltop quintessence models. We find that all of the models examined here can be well described by a pivotlike redshift, $z_{\text{pivot}}$, at which the value of $w(z)$ in the model is equal to $w_{*}$. However, the exact value of $z_{\text{pivot}}$ is a model-dependent quantity; it varies from $z_{\text{pivot}}=0.22–0.25$ for the CPL models to $z_{\text{pivot}}=0.17–0.20$ for the hilltop quintessence models. Hence, for all of the models considered here, a constant-$w$ fit gives the value of $w$ for $z$ near 0.2. However, given the fairly wide variation in $z_{\text{pivot}}$ over even this restricted set of models, the information gained by fitting to a constant value of $w$ seems rather limited.

There has been recent interest in the cosmological consequences of energy-momentum-powered gravity models in which the matter side of Einstein’s equations includes a term proportional to some power, $n$, of the energy-momentum tensor, in addition to the canonical linear term. Previous works have suggested that these models can lead to a recent accelerating universe without a cosmological constant, but they can also be seen as phenomenological extensions of the standard $\mathrm{\Lambda }\mathrm{CDM}$, which are observationally constrained to be close to the $\mathrm{\Lambda }\mathrm{CDM}$ limit. Here we show that these models violate the temperature-redshift relation, and are therefore further constrained by astrophysical measurements of the cosmic microwave background temperature. We provide joint constraints on these models from the combination of astrophysical and background cosmological data, showing that this power is constrained to be about $|n|<0.01$ and $|n|<0.1$, respectively, in models without and with a cosmological constant, and improving previous constraints on this parameter by more than a factor of 3. By breaking degeneracies between this parameter and the matter density, constraints on the latter are also improved by a factor of about 2.

We show that by jointly fitting cosmic microwave background (CMB) and astrophysical data—a compilation of UV luminosity data from the Hubble Frontier Field and neutral hydrogen data from distant source—we can infer on the shape of the evolution of the ionized hydrogen fraction with redshift, in addition to constraining the average optical depth $\tau$. For this purpose, we introduce here a novel extended model that includes hydrogen ionization histories which are monotonic with redshift, but allow for an asymmetry, as indicated from our previous works on a free-form reconstruction of reionization. By using our baseline data combination, we obtain $\tau =0.0542_{-0.0028}^{+0.0017}$, consistent with our previous works and tighter than the one inferred by Planck 2018 data because of the combination of CMB with astrophysical data. We find that the symmetric hypothesis within our parametrization is disfavored at $4\sigma$. We test our findings by using alternative likelihoods for CMB polarization at low multipoles, i.e. based on the 2020 reprocessing of Planck high frequency instrument data or on the joint analysis of Wilkinson microwave anisotropy probe and Planck low frequency instrument data, obtaining consistent results that disfavor the symmetric hypothesis of the reionization history at a high statistically significant level. These results will be further tested by more precise astrophysical data such as that from JWST and Euclid deep fields.

The $\mathrm{\Lambda }\mathrm{CDM}$ model has successfully explained a wide range of cosmological observations, but is increasingly challenged by the emergence of cosmological tensions, particularly the Hubble tension $H_0$ and the $S_8$ tension. The Hubble tension, with a significance above $5\sigma$, and the $S_8$ tension, showing a discrepancy of approximately $2–4\sigma$, highlight inconsistencies between measurements of the local and early Universe. The $\mathrm{\Lambda }\mathrm{CDM}$ model has been highly successful in explaining cosmological observations but is increasingly challenged by the $H_0$ tension ($>5\sigma$) and the $S_8$ tension ($2–4\sigma$). These tensions expose significant inconsistencies between measurements of the local Universe and those of the early Universe. This paper expands a well-established interacting dark energy (IDE) phenomenological scenario, where dark matter (DM) can transfer energy to dark energy (DE) or vice versa, depending on the sign of the coupling parameter $\xi$. The novel feature consists in a transition mechanism which reverses the direction of the energy-momentum transfer after the redshift where the densities of the dark species are the same. We evaluate this model using a comprehensive set of recent observational data, including baryon acoustic oscillations (BAO) from the DESI survey, type Ia supernovae from the PantheonPlus, DESY5, and Union3 samples, and cosmic microwave background (CMB) data from Planck. Our analysis shows that this scenario relaxes the $H_0$ and $S_8$ tensions, particularly when Cepheid distance calibration in the SH0ES samples or DESI data are included. Our analysis shows that this scenario can potentially relax both the $H_0$ and $S_8$ tensions simultaneously. We find the new model to be weakly preferred over $\mathrm{\Lambda }\mathrm{CDM}$ by BAO-DESI data. However, we show that the IDE model features positive Bayesian evidence compared to $\mathrm{\Lambda }\mathrm{CDM}$ only when Cepheid distance calibration in the SH0ES sample is used to calibrate SNIa data from PantheonPlus.

Compact binaries on eccentric orbits are another class of gravitational-wave (GW) sources that can provide a wealth of information on binary formation pathways and astrophysical environments. However, historically, eccentricity is often neglected in modeled GW searches for compact binaries. We show that currently used modeled searches that employ quasicircular template banks are highly ineffectual in detecting binary neutron star (BNS) and neutron star-black hole (NSBH) systems with orbital eccentricities in the range of $[{10}^{-5},0.15]$ at a GW frequency of 15 Hz. For populations of moderately eccentric BNS and NSBH binaries with (anti)aligned component spins, we demonstrate that quasicircular template banks fail to detect up to $\sim 40\%$ of such systems. To alleviate these inefficiencies, we develop the first geometric template bank for the search of BNSs and NSBH binaries that includes masses, (anti)aligned spins and moderate eccentricity. Utilizing the post-Newtonian inspiral waveform TaylorF2Ecc and a global coordinate transformation, we construct a globally flat metric to efficiently place eccentric templates. Our geometric template bank is highly effectual, and significantly improves the recovery of eccentric signals with less than 6% of signals missed due to the finite template spacing in the bank.

The small Kerr-anti–de Sitter black hole demonstrates instability due to the superradiance of either a massive or massless scalar field. Previous leading-order approximations of the spectrum are inefficient. In particular, the leading-order real part of the eigenfrequency is insensitive to the spin of the black hole. In this work, we improve the analysis by including the next-to-leading-order contribution. Compared to the numerical calculation, the new spin-dependent real part presents significantly better agreement, and the error in the imaginary part is also reduced to less than 60% for most black hole spins.

We explore the utility of qutrits and qubits for simulating the flavor dynamics of dense neutrino systems. The evolution of such systems impacts some important astrophysical processes, such as core-collapse supernovae and the nucleosynthesis of heavy nuclei. Many-body simulations require classical resources beyond current computing capabilities for physically relevant system sizes. Quantum computers are therefore a promising candidate to efficiently simulate the many-body dynamics of collective neutrino oscillations. Previous quantum simulation efforts have primarily focused on properties of the two-flavor approximation due to their direct mapping to qubits. Here, we present new quantum circuits for simulating three-flavor neutrino systems on qutrit- and qubit-based platforms, and demonstrate their feasibility by simulating systems of two, four, and eight neutrinos on IBM and Quantinuum quantum computers.

In this paper, we explore a novel framework for explaining the mass and radius relationships of observed neutron stars by considering strange stars (SSs) admixed with mirror dark matter (MDM). We develop a theoretical model that incorporates noncommutative algebra to describe the interactions between ordinary strange quark matter (SQM) and MDM, which are predicted to form compact objects that could explain recent astrophysical data, including observations of PSR $\mathrm{J}0740+6620$, PSR $\mathrm{J}0030+0451$, PSR J0437-4715, and the central compact object in HESS J1731-347. Notably, we demonstrate that the exotic mass-radius measurement of XTE J1814-338 can be explained by the presence of a mirror SS with an ordinary SQM core. In contrast to other explanations based on boson stars, our $\mathrm{SS}+\mathrm{MDM}$ model offers a natural explanation for this system. We provide detailed mass-radius comparisons with observational data and discuss future observations that could test the predictions of our model, offering new insights into neutron star structure and the role of dark matter in compact objects.

The nova outburst can produce a large number of neutrinos, whether it is the nuclear reaction process during the explosion or the shock wave acceleration proton process. We study the low-energy nuclear and thermal neutrino luminosity of novae with CO white dwarf (WD) mass ranging from 0.6 to $1.1M_{\odot }$ with different accretion rates $\dot{M}$, core temperatures $(T_{\mathrm{C}})$, and mixing degrees. We find that, during the accretion phase, low-energy neutrinos are mainly produced by pp chains and plasma decay, and photon luminosity is greater than low-energy nuclear and thermal neutrino luminosity. During the thermonuclear runaway (TNR) phase, low-energy neutrinos are mainly produced by the CNO cycle and photon-neutrino interaction, and the low-energy nuclear and thermal neutrino luminosity far exceeds the photon luminosity. We find that the more massive the WD, the shorter the cycle time and the higher the low-energy nuclear neutrino luminosity. The higher the accretion rate, the lower the low-energy nuclear neutrino luminosity. If the accretion mixing effect is not taken into account, the outburst interval becomes longer, and the low-energy nuclear neutrino luminosity will be increased. For the cooler nova model $(T_{\mathrm{C}}=1\times {10}^7\mathrm{K})$, the low-energy nuclear neutrino luminosity will be lower during the accretion phase and higher at the TNR. We also predict the neutrino luminosity and energy spectrum of the upcoming recurrent nova T Coronae Borealis (T CrB). We estimate that the next T CrB outburst has a low-energy nuclear neutrino peak luminosity of $2.7\times {10}^8{\mathrm{L}}_{\nu ,\odot }$ and a low-energy nuclear neutrino outburst duration of 88 days. In addition, we predict that the high-energy hadronic neutrino flux produced by T CrB nova cannot be observed by the current-generation IceCube.

Since the derivation of a well-defined $D\to 4$ limit for four-dimensional Einstein Gauss-Bonnet (4DEGB) gravity coupled to a scalar field, there has been interest in testing it as an alternative to Einstein’s general theory of relativity. Using the Tolman-Oppenheimer-Volkoff equations modified for charge and 4DEGB gravity, we model the stellar structure of charged, noninteracting quark stars. We find that increasing the Gauss-Bonnet coupling constant $\alpha$ or the charge $Q$ both tend to increase the mass-radius profiles of quark stars described by this theory, allowing a given central pressure to support larger quark stars in general. We also derive a generalization of the Buchdahl bound for charged stars in 4DEGB gravity. As in the uncharged case, we find that quark stars can exist below the general relativistic Buchdahl bound and Schwarzschild radius $R=2M$, due to the lack of a mass gap between black holes and compact stars in the 4DEGB theory. Even for $\alpha$ well within current observational constraints, we find that quark star solutions in this theory can describe extreme compact charged objects, objects whose radii are smaller than what is allowed by general relativity.

Ultralight bosons, naturally appearing in well-motivated extensions to the Standard Model, can constitute all the dark matter. Models with particle mass close to the smallest phenomenologically allowed exhibit coherent field configurations at (sub)galactic scales, oscillating at a frequency corresponding to the fundamental mass of the dark matter particle. The gravitational field of these structures inherits the dark matter field’s coherent oscillations, leaving an imprint on gravitational (and electromagnetic) waves sourced close to (or in) such overdensities. This happens via a heterodyning frequency modulation, which can later be decoded in a gravitational-wave detector. An analogous effect occurs in models with universal (conformal) couplings of ultralight bosons with ordinary matter, generated by the direct interaction with the oscillating field. In this work, we explore this phenomenon in detail and assess the capability of near-future interferometers to probe ultralight dark matter and its potential conformal couplings to matter. Using astrophysical population models, together with results from cosmological simulations, we find that the observation of gravitational waves from spinning neutron stars at the Galactic Center with the Einstein Telescope/Cosmic Explorer would be particularly effective in constraining ultralight dark matter.

A precise characterization of the magnetic properties of LISA Pathfinder free falling test-masses is of special interest for future gravitational wave observatory in space. Magnetic forces have an important impact on the instrument sensitivity in the low frequency regime below the millihertz. In this paper we report on the magnetic injection experiments performed throughout LISA Pathfinder operations. We show how these experiments allowed a high precision estimate of the instrument magnetic parameters. The remanent magnetic moment was found to have a modulus of $(0.245\pm 0.081){\mathrm{nAm}}^2$, the x-component of the background magnetic field within the test masses position was measured to be $(414\pm 74)\mathrm{nT}$ and its gradient had a value of $(-7.4\pm 2.1)\mathrm{\mu }\mathrm{T}/\mathrm{m}$. Finally, we also measured the test mass magnetic susceptibility at 5 mHz to be $(-3.3723\pm 0.0069)\times {10}^{-5}$. All results are in agreement with on-ground estimates.

Gas molecules within the gravitational reference sensor (GRS) subjected to temperature fluctuations can give rise to a net disturbance force on the test mass (TM), known as the radiometer effect, which limits the low frequency sensitivity of space-borne gravitational wave (GW) detection. Prior research relied on the infinite-plate model to evaluate this effect, supplemented by a correction factor to account for the GRS geometric configuration, whose specific form remains unknown and is accessible solely through experiments or simulations. In this work, we rigorously derive an analytical expression for the radiometer disturbance force by analyzing the interaction between gas molecules and the TM within the GRS subjected to a linear temperature gradient. Our calculation transcends the conventional infinite-plate model by elucidating not only its dependence on sensor temperature and pressure but also explicitly revealing its correlation with the gap distances between the GRS and TM, effectively yielding a precise expression for the correction factor. To validate the established model, we conduct molecular Monte Carlo simulations, which exhibit favorable concordance with the theoretical predictions, reinforcing its reliability and efficacy. Consequently, this analytical approach offers a robust and efficient means of accurately assessing the radiometer disturbance force in space-borne GW detection. Furthermore, its insight into gap dependence provides theoretical guidance for optimizing sensor structural designs.

Instability of the charged pion vacuum resulting in the pion condensation is studied within the $\lambda |\varphi {|}^4$ model at the rapid rotation of the system in presence of external fields. Case of the static external scalar and electric square potential wells and the uniform magnetic field is studied in detail. The Meissner and Aharonov-Bohm effects and the London moment are taken into account. Analogies and differences with the behavior of metallic superconductors under the action of the rotation and the external magnetic field are analyzed.

We examine the prospect of observing genuine lepton-number-violating (LNV) signals at hadron colliders in the context of the type II seesaw mechanism. The model features smoking gun signals involving same-sign di-leptons and jets that may be the primary observable channel in certain regions of the parameter space. The flavor composition of final-state charged leptons is related to the origin of neutrino masses and is correlated with other rare processes, such as neutrinoless double-beta decay. We review existing collider limits and provide sensitivity estimates from LNV signals at upcoming Large Hadron Collider runs, including nonzero mass splittings between triplet components.

We derive the full next-to-eikonal (NEik) corrections to the gluon propagator from before to after traversing a highly boosted gluon background field, including corrections both beyond the shockwave limit and beyond the static limit in particular. After summarizing the results of the full NEik corrections to the before-to-after quark propagator computed in our earlier works, we also derive the before-to-inside, inside-to-inside, and inside-to-after quark and gluon propagators, which are building blocks to calculate high-energy scattering processes at NEik order. Using these results and also including the NEik corrections that stem from interactions with the target via t-channel quark exchanges, we compute inclusive cross sections for quark and gluon production at forward rapidities in quark-nucleus and gluon-nucleus scatterings at NEik accuracy.