Over the last years, the search of new regular black bounce solutions has drawn a lot of attention by the international community working in gravitation. Indeed, in the era of gravitational wave detections out of binary mergers and of the imaging of the plasma around supermassive black holes, the study of regular solutions has become a common trend given the unique opportunity posed by multimessenger astronomy to test deviations from the Kerr family of solutions. Among them, in this paper, we consider the black bounce paradigm introduced by Simpson and Visser [J. Cosmol. Astropart. Phys. 02 (2019) 042.] and provide a general procedure for reconstructing static spherically symmetric black bounce-type solutions that might interpolate between regular black holes and wormholes. We show that even after imposing some smoothness and flatness conditions on the metric components, additional analysis is required to obtain a well-defined black bounce solution. Then, the corresponding matter Lagrangian is reconstructed by using nonlinear electrodynamics, and the energy conditions are studied.

The longitudinal components of massive vector fields generated during inflation constitute a well-motivated dark matter candidate, with interesting phenomenological implications. During the epoch of radiation domination following inflation, their spectrum exhibits a peak at small scales, whose amplitude and position are governed by the parameters of the dark matter model. We calculate the stochastic gravitational wave spectrum induced at second order in fluctuations by such a longitudinal vector peak. We demonstrate that the amplitude of the gravitational wave spectrum can, in principle, reach significant values at nano-Hertz frequencies or lower. This result suggests a novel gravitational wave probe to test inflationary vector dark matter scenarios, independent from assumptions on the coupling of dark vectors to the Standard Model. Additionally, we derive new analytical formulas for the longitudinal vector transfer functions during radiation domination, offering a valuable tool for characterizing the convolution integrals that govern the properties of the induced gravitational waves.

We present the results from a series of analyses on two parametric tests of gravity that modify the growth of linear, subhorizon matter perturbations in the $\mathrm{\Lambda }\mathrm{CDM}$ model. The first test, known as the $(\mu ,\mathrm{\Sigma })$ framework, modifies the Poisson and lensing equations from general relativity (GR). The second test introduces the growth index $\gamma$, which directly affects the time evolution of matter density perturbations. Our study is motivated by results from the analysis of the Planck-PR3 2018 spectra, which indicate a preference for ${\mathrm{\Sigma }}_0\ne 0$ and ${\gamma }_0>0.55$, both of which deviate from the $\mathrm{\Lambda }\mathrm{CDM}$ predictions at a significance level of $\sim 2.5\sigma$. To clarify the nature of these anomalous results and understand how the lensing anomaly fits into the picture, we analyze the most recent Planck-PR4 spectra extracted from the updated NPIPE maps. Overall, the Planck-PR4 data show better consistency with GR. The updated likelihood Camspec provides constraints on ${\mathrm{\Sigma }}_0$ and ${\gamma }_0$ that are consistent with GR within $1.5\sigma$ and $2\sigma$, respectively. The updated likelihoods HiLLiPoP and LoLLiPoP show even closer agreement, with all parameter values consistent with a $\mathrm{\Lambda }\mathrm{CDM}$ cosmology within $1\sigma$. This enhanced consistency is closely correlated with the lensing anomaly. Across the different likelihoods, the tendency of ${\mathrm{\Sigma }}_0$ and ${\gamma }_0$ to drift toward nonstandard values matches the observed preference for $A_L>1$, both of which are significantly reduced or disappear within the Planck-PR4 data.

A pressureless dark matter component fits well with several cosmological observations. However, there are indications that cold dark matter may encounter challenges in explaining observations at small scales, particularly at galactic scales. Observational data suggest that dark matter models incorporating a pressure component could provide solutions to these small-scale problems. In this work, we investigate the possibility that present-day dark matter may result from a decaying noncold dark matter sector transitioning into the dark energy sector. As the sensitivity of astronomical surveys rapidly increases, we explore an interacting scenario between dark energy and noncold dark matter, where dark energy has a constant equation of state ($w_{\mathrm{de}}$), and dark matter, being noncold, also has a constant (non-zero) equation of state ($w_{\mathrm{dm}}$). Considering the phantom and quintessence nature of dark energy, characterized by its equation of state, we separately analyze interacting phantom and interacting quintessence scenarios. We constrain these scenarios using cosmic microwave background (CMB) measurements and their combination with external probes, such as DESI-BAO and PantheonPlus. From our analyses, we find that a very mild preference for noncold dark matter cannot be excluded based on the employed datasets. Additionally, for some datasets, there is a pronounced preference for the presence of an interaction at more than 95% confidence level (CL). Moreover, when the dark energy equation of state lies in the phantom regime, the $S_8$ tension can be alleviated. This study suggests that cosmological models incorporating a noncold dark matter component should be considered as viable scenarios with novel phenomenological implications, as reflected in the present work.

The possible formation histories of neutron star binaries remain unresolved by current gravitational-wave catalogs. The detection of an eccentric binary system could be vital in constraining compact binary formation models. We present the first search for aligned spin eccentric neutron star-black hole binaries (NSBH) and the most sensitive search for aligned-spin eccentric binary neutron star (BNS) systems using data from the third observing run of the advanced LIGO and advanced Virgo detectors. No new statistically significant candidates are found; we constrain the local merger rate for specific astrophysical models to be less than $150{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$ for binary neutron stars in the field, and, 50, 100, and $70{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$ for neutron star-black hole binaries in globular clusters, hierarchical triples and nuclear clusters, respectively, at the 90% confidence level if we assume that no sources have been observed from these populations. We predict the capabilities of upcoming and next-generation observatory networks; we investigate the ability of three LIGO (${\mathrm{A}}^{\#}$) detectors and Cosmic Explorer $\mathrm{CE}(20\mathrm{km})+\mathrm{CE}(40\mathrm{km})$ to use eccentric binary observations for determining the formation history of neutron star binaries. We find that 2–100 years of observation with three ${\mathrm{A}}^{\#}$ observatories are required before we observe clearly eccentric NSBH binaries; this reduces to only 10 days–1 year with the CE detector network. CE will observe tens to hundreds of measurably eccentric binaries from each of the formation models we consider.

The observed spectral bump around 10 TV in cosmic-ray (CR) proton and helium spectra, along with the phase and amplitude evolution of CR dipole anisotropy, provide plausible yet indirect evidence for the presence of a nearby CR source. This study investigates the potential of giant molecular clouds (GMCs) located near the solar system to act as natural probes of CRs from the nearby source, with their gamma-ray emissions serving as indicators of spatial variations in CR flux within the solar neighborhood resulting from this source. We show that a nearby source, accounting for the CR data, could imprint distinct features on the $\gamma$-ray spectra of different GMCs. We expect that these features are detectable by the Large High Altitude Air Shower Observatory and upcoming high-energy $\gamma$-ray observatories, providing a powerful test for the hypothesized nearby source. Notably, we find that determining the energy dependence of the $\gamma$-ray spectral index offers a promising approach to investigate the nearby source and constrain its distance. Conversely, if the spectral bump is a widespread Galactic phenomenon, the energy dependence would exhibit uniformity across all GMCs, distinguishing the underlying mechanism accounting for the spectral bump from the scenario involving a nearby source.

There is a candidate electromagnetic (EM) counterpart to the binary black hole merger GW190521, identified as ZTF19abanrhr within active galactic nuclei (AGN) $\mathrm{J}124942.3+344929$. Additionally, GW190514 is proposed as a plausible precursor merger to GW190521 within a hierarchical merger scenario. In this study, we investigate the potential association between GW190514 and GW190521 as a hierarchical triple merger associated with ZTF19abanrhr, taking into account the sky position, distance, and mass of the sources using a Bayesian criterion. Our analysis reveals that the association is favored over a random coincidence, with a log Bayes factor of 16.8, corresponding to an odds ratio of $\sim 199:1$, assuming an astrophysical prior odds of ${10}^{-5}$. Notably, when accounting for the primary masses of the two gravitational-wave events as potential products of mergers in the AGN formation channel, the Bayes factor increases significantly, further enhancing the preference for this association by a factor of $\sim {10}^2$, corresponding to a log Bayes factor of 21.5 and an odds ratio of $\sim 2\times {10}^4:1$. Our results suggest strong evidence for the first hierarchical triple merger associated with an EM counterpart in the AGN formation channel. This work is crucial for understanding the formation mechanisms of massive black holes, the role of AGNs in hierarchical mergers, and the implications of multimessenger astronomy.

Lorentz-invariance violation (LV) at energy scales approaching the Planck regime serves as a critical probe for understanding quantum gravity phenomenology. Astrophysical observations of gamma-ray bursts (GRBs) present a promising avenue for testing LV-induced spectral lag phenomena; however, interpretations are complicated by degeneracies between LV effects and intrinsic emission delays. This study systematically investigates three competing time delay models: model A (LV delay combined with a constant intrinsic delay), model B (energy-dependent intrinsic delay without LV), and model C (LV delay combined with energy-dependent intrinsic delay). We utilize mock GRB datasets generated under distinct delay mechanisms and employ Bayesian parameter estimation on simulated observations of 10 GRBs. Our findings demonstrate that model C consistently recovers input parameters across all datasets, including those designed to mimic LV-dominated (model A) and intrinsic delay-dominated (model B) scenarios. In contrast, models A and B struggle to reconcile data generated under alternative mechanisms, particularly when confronted with high-energy TeV photons from GRB 190114C and GRB 221009A. Our analysis confirms that the incorporation of energy-dependent intrinsic delays in model C is essential for establishing robust LV constraints, effectively resolving prior ambiguities in the interpretation of multi-GeV and TeV photon emissions. The results validate model C as a generalized framework for future LV searches, yielding a subluminal LV scale of $E_{\mathrm{LV}}\simeq 3\times {10}^{17}\mathrm{GeV}$ based on realistic datasets, including 14 Fermi-LAT multi-GeV photons from eight GRBs, a 99.3 GeV photon from GRB 221009A observed by Fermi-LAT, a TeV photon from GRB 190114C detected by MAGIC, and a multi-TeV photon from GRB 221009A recorded by LHAASO. These findings are consistent with earlier constraints derived from Fermi-LAT datasets. This work underscores the necessity for joint modeling of LV and astrophysical emission processes in next-generation LV studies utilizing observatories such as LHAASO and CTA.

We anticipate that the data acquired by the Laser Interferometer Space Antenna (LISA) will be dominated by the gravitational wave signals from several astrophysical populations. The analysis of these data is a new challenge and is the main focus of this paper. Numerous gravitational wave signals overlap in the time and/or frequency domain, and the possible correlation between them has to be taken into account during their detection and characterization. In this work, we present a method to address the LISA data analysis challenge; it is flexible and scalable for a number of sources and across several populations. Its performance is demonstrated on the simulated data LDC2a.

Coincident multimessenger observations of cosmic sources can offer numerous benefits, especially when used in the context of synergistic astrophysics. One significant advantage is enhancing the detection significance of separate detectors by correlating their data and assuming joint emission. We have formulated an approach for updating the Bayesian posterior probability of an astrophysical origin, namely $p_{\text{astro}}$, relying on multimessenger coincidences assuming an emission model. The description is applicable to any combination of messengers. We demonstrated the formalism for the gravitational waves and high-energy neutrinos case. Applying our method to the public data of candidate coincident high-energy neutrinos with subthreshold gravitational-wave triggers, we found that in the case of highly energetic neutrino coincidences, $p_{\text{astro}}$ can increase from approximately $\sim 0.1$ to $\sim 0.9$. The amount of improvement depends on the assumed joint emission model. If models are trusted, the marked improvement makes subthreshold detections much more confident. Moreover, the model dependency can also be used to test the consistency of different models. This work is a crucial step toward the goal of uniting all detectors on equal footing into a statistically integrated, Earth-sized observatory for comprehensive multimessenger astrophysics.

We present a full sampling of the hierarchical population posterior distribution of merging black holes using current gravitational-wave data. We directly tackle the most relevant intrinsic parameter space made of the binary parameters (masses, spin magnitudes, spin directions, redshift) of all the events entering the GWTC-3 LIGO/Virgo/KAGRA catalog, as well as the hyperparameters of the underlying population of sources. This results in a parameter space of about 500 dimensions, in contrast with current investigations where the targeted dimensionality is drastically reduced by marginalizing over all single-event parameters. In particular, we have direct access to (i) population parameters, (ii) population-informed single-event parameters, and (iii) correlations between these two sets of parameters. We quantify the fractional contribution of each event to the constraints on the population hyperparameters. Our implementation relies on modern probabilistic programming languages and Hamiltonian Monte Carlo, with a continuous interpolation of single-event posterior probabilities. Sampling the full hierarchical problem is feasible, as demonstrated here, and advantageous as it removes some (but not all) of the Monte Carlo integrations that enter the likelihood together with the related variances.

Magnetic monopoles (MMs) are well-motivated hypothetical particles whose discovery would symmetrize Maxwell equations, explain quantization of electric charge, and probe the gauge structure of the unified theory. Recent models predict MMs with low masses, reinvigorating searches at colliders. However, most theories predict composite MMs, whose production in parton-parton collisions is expected to be suppressed. The Schwinger process, whereby MM pairs tunnel through the vacuum barrier in the presence of a strong magnetic field, is not subject to this limitation. Additionally, the Schwinger cross section can be calculated nonperturbatively. Together, these make it a golden channel for low-mass MM searches. We investigate the Schwinger production of MMs in heavy-ion collisions at future colliders, in collisions of cosmic rays with the atmosphere, and in decay of magnetic fields of cosmic origin. We find that a next-generation collider would provide the best sensitivity, allowing one to discover or exclude MMs with TeV-scale masses. At the same time, exploiting the infrastructure of industrial ore extraction and Antarctic ice drilling could advance the field at a faster timescale and with only a modest investment. In particular, we show with detailed calculations that the proposed experiments will be sensitive to fluxes of low-mass MMs as low as a few units of ${10}^{-22}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}{\mathrm{sr}}^{-1}$ in a wide range of Lorentz factors. We also propose deploying dedicated MM detectors in conjunction with cosmic ray observatories to directly investigate if the unexplained, highest-energy cosmic rays are MMs. Together, the proposed efforts would define the field of MM searches in the next decades.

With significantly improved sensitivity, the Einstein Telescope (ET), along with other upcoming gravitational wave detectors, will mark the beginning of precision gravitational wave astronomy. However, the pursuit of surpassing current detector capabilities requires careful consideration of technical constraints inherent in existing designs. The significant improvement of ET lies in the low-frequency range, where it anticipates a one-million-fold increase in sensitivity compared to current detectors. Angular control noise is a primary limitation for LIGO detectors in this frequency range, originating from the need to maintain optical alignment. Given the expected improvements in ET’s low-frequency range, precise assessment of angular control noise becomes crucial for achieving target sensitivity. To address this, we developed a model of the angular control system of Advanced Virgo, closely matching experimental data and providing a robust foundation for modeling future-generation detectors. Our model, for the first time, enables replication of the measured coupling level between angle and length, as well as the control noise level. Additionally, our findings confirm that Virgo, unlike LIGO, is not constrained by alignment control noise, even if the detector were operating at full power.

Near-future high-intensity lasers offer prospects for the observation of nonlinear Breit-Wheeler pair production in an overcritical field regime, where the quantum nonlinearity parameter substantially exceeds unity. This experimentally yet unexplored scenario is envisaged here to be reached via the collision of a tightly focused laser pulse with high-energy bremsstrahlung photons. We calculate the achievable number of pairs in a range of laser intensities around ${10}^{23}\mathrm{W}/{\mathrm{cm}}^2$ and GeV energies of the incident bremsstrahlung-generating electron beam. We investigate under which conditions the attenuation of the $\gamma$-beam due to the production process must be taken into account and how much the second generation of created pairs contributes to the total yield. In the considered interaction regime, where the local production rate grows rather moderately with higher field intensities, it is shown that the range of mostly contributing bremsstrahlung frequencies is generally very broad. For sufficiently large values of the quantum nonlinearity parameter, an optimum domain of frequencies emerges, which is located far below the spectral end point. Furthermore, we show that it is beneficial for achieving the optimum pair yield to increase the interaction volume by a wider laser focus at the expense of decreased field intensity.

The highly energetic particle medium formed in the ultrarelativistic heavy ion collision displays a notable difference in the temperatures between its central and peripheral regions. This temperature gradient can generate an electric field within the medium, a phenomenon referred to as the Seebeck effect. The magnitude of such an electric field per unit temperature gradient in the limit of zero electric current is known as the Seebeck coefficient. We have estimated the Seebeck coefficient for a dense quark-gluon plasma medium by using the relativistic Boltzmann transport equation in the recently developed novel relaxation time approximation (RTA) model within the kinetic theory framework. This study explores the Seebeck coefficient of individual quark flavors as well as the entire partonic medium, with the emphasis on its dependence on the temperature and the chemical potential. Our observation indicates that, for given current quark masses, the magnitude of the Seebeck coefficient for each quark flavor, as well as for the partonic medium decreases as the temperature rises, and increases as the chemical potential increases. Furthermore, we have investigated the Seebeck effect by considering the partonic interactions described in perturbative thermal QCD within the quasiparticle model. In addition, we have presented a comparison between our findings and the results of the standard RTA model. We have observed that the Seebeck coefficient of the QGP medium gets conspicuously decreased in the novel RTA model, as compared to that in the standard RTA model. A decreased Seebeck coefficient in the novel RTA model describes a smaller magnitude of induced electric field in the medium than that estimated by the standard RTA model. However, the rate of decline gets gradually smaller as the medium gets hotter for both the current quark mass scenario and the quasiparticle mass scenario. It is also found that, in the noninteracting case, the Seebeck coefficient possesses a slightly negative value in the high-temperature region, unlike the quasiparticle description, where the Seebeck coefficient remains positive for the entire temperature range.

We analyze in detail the interactions between the nontopological soliton ($Q$-ball) and its perturbations. We extend the previous literature by carefully identifying the domain of applicability of linear analysis as well as discussing Friedberg, Lee, and Sirlin $Q$-balls. Applications to early Universe physics are briefly commented.

We revisit the path integral description of quantum tunneling and its generalization to excited states. For clarity, we focus on the simple toy model of a point particle in a double-well potential, for which we perform all steps explicitly. Instead of performing the familiar Wick rotation from physical to imaginary time—which is inconsistent with the requisite boundary conditions when treating tunneling from excited states—we regularize the path integral by adding an infinitesimal complex contribution to the Hamiltonian, while keeping time strictly real. We find that this gives rise to a complex stationary-phase solution, in agreement with recent insights from Picard-Lefshetz theory. We then show that there exists a class of analytic solutions for the corresponding equations of motion, which can be made to match the appropriate boundary conditions in the physically relevant limits of a vanishing regulator and an infinite physical time. We provide a detailed discussion of this nontrivial limit. We find that, for systems without an explicit time-dependence, our approach reproduces the picture of an instantonlike solution defined on a finite Euclidean-time interval. Lastly, we discuss the generalization of our approach to broader classes of systems, for which it serves as a reliable framework for high-precision calculations.

Extensions of the standard model featuring excited fermions present an interesting framework that motivates the search for exotic particles at the LHC. Additionally, these extensions offer potential explanations for the muon’s anomalous magnetic moment and other precision observables, shedding light on the energy scale and key parameters of the new theory. Our analysis focuses on the one-loop radiative correction originating from excited lepton doublet and triplet states using the effective Lagrangian approach. The bounds derived from the $(g-2{)}_{\mu }$ anomaly can be complemented with the ones arising from other observables, like the electroweak precision observable $\mathrm{\Delta }\rho$ and the signals from direct LHC searches to constrain the effective theory. Our results suggest that the $(g-2{)}_{\mu }$ anomaly can be addressed within a very narrow region of the effective theory scale. Consequently, this imposes indirect constraints on the parameter space of excited fermions.

In this work, we investigate the impact of the $L_{\mu }-L_{\tau }$ model, which predicts a new massive gauge boson $Z^{\prime }$ on astrophysical neutrino events at the IceCube Observatory. This new gauge boson couples with leptons from the second and third families and would break the power law of the astrophysical neutrino flux due to the interaction of this flux with the cosmic neutrino background. We derive the sensitivity of IceCube to this model considering the high-energy start events data from 12 years of observation by assuming different assumptions for the redshift distributions of astrophysical neutrino sources, mass ordering, and sum of neutrino masses. Our results indicate that the current IceCube data are able to probe small coupling and masses on the order of some few MeV, with the covered parameter space being larger if a distribution of neutrino sources is described by the star formation rate model. In addition, we demonstrate that IceCube-Gen2 will cover a large region of the parameter space and will allow us to improve our understanding of the $L_{\mu }-L_{\tau }$ model.

Probing Higgsinos remains a challenge at the LHC owing to their small production cross sections and the complexity of the decay modes of the nearly mass degenerate Higgsino states. The existing limits on Higgsino mass are much weaker compared to its bino and wino counterparts. This leaves a large chunk of sub-TeV supersymmetric parameter space unexplored so far. In this work, we explore the possibility of probing Higgsino masses in the 400–1000 GeV range. We consider a simplified supersymmetric scenario where $R$-parity is violated through a baryon number violating trilinear coupling. We adopt a machine-learning-based top tagger to tag the boosted top jets originating from Higgsinos, and for our collider analysis, we use a boosted decision tree classifier to discriminate signal over SM backgrounds. We construct two signal regions characterized by at least one top jet and different multiplicities of $b$-jets and light jets. Combining the statistical significance obtained from the two signal regions, we show that Higgsino mass as high as 925 GeV can be probed at the HL-LHC.