In the framework of the nonlinear Euler-Heisenberg electrodynamics coupled to general relativity, we consider static Einstein-Euler-Heisenberg magnetically and dyonically charged black hole spacetimes. These black holes are characterized, as usual, by mass $M$, magnetic charge $Q_m$, electric charge $Q$ and the Euler-Heisenberg nonlinear parameter. We find all possible equatorial trajectories for neutral and charged test particles. We analyze the light rings by using the Plebański pseudometric. The shape of the shadow of these black holes is presented, discussed, and compared with the one of the corresponding Reissner-Nordström linear cases.

A hairy Schwarzschild black hole describes the deformation of a Schwarzschild black hole due to including additional sources. It is found that depending on the hairy parameters, the photons’ configurations around this black hole can be classified into two cases, corresponding to the hairy Schwarzschild black hole with a single photon sphere and double photon spheres, respectively. We focus on the shadows and images of the hairy Schwarzschild black hole under two types of static thin illuminations conditions: disk accretion and spherical accretion, respectively. Under both illuminations, the two hairy parameters ($\alpha$ and $l_o$) have competitive effects on the shadow and optical appearance image of the hairy Schwarzschild black hole with a single photon sphere. This means that even though the parameters have significant influences on the rings and shadows, its images with certain groups of $\alpha$ and $l_o$ could be indistinguishable to that of Schwarzschild black hole, namely, the degeneracies of images raise between the hairy Schwarzschild black hole and Schwarzschild black hole. Moreover, the optical appearance image of the hairy Schwarzschild black hole with double photon spheres will exhibit new additional rings and accretion features, which are not present in the images of a (hairy) Schwarzschild black hole with a single photon sphere. Our theoretical studies on the rings and shadows provide a potential tool to differentiate the hairy Schwarzschild black hole with double photon spheres from the Schwarzschild black hole, but they are not always helpful for the cases with a single photon sphere due to the degeneracies.

We explore the consistent truncation of conserved charges in quadratic curvature gravity (QCG) with anti–de Sitter asymptotics to the linear order in the Weyl tensor. The QCG action is given by the most general curvature-squared corrections to Einstein gravity, and it is suitably rendered finite by the addition of extrinsic counterterms (Kounterterms). The conserved charges derived from this action are, as a consequence, nonlinear in the spacetime Riemann tensor. A detailed analysis of the falloff of generic static solutions leads to a charge proportional to the electric part of the Weyl tensor, without loss of information on the energy of the system. The procedure followed provides firmer ground to the extension of the notion of Conformal Mass to higher-curvature gravity, as it appears as associated to a renormalized action. We observe that criticality condition in QCG poses an obstruction to the charge linearization, in contrast to previous results in Lovelock gravity, where degeneracy condition plays a key role.

We construct and dynamically evolve dipolar self-interacting scalar boson stars in a model with sextic ($+$ quartic) self-interactions. The domain of existence of such dipolar $Q$-stars has a similar structure to that of the fundamental monopolar stars of the same model. For the latter it is structured in a Newtonian plus a relativistic branch, wherein perturbatively stable solutions exist, connected by a middle unstable branch. Our evolutions support similar dynamical properties of the dipolar $Q$-stars that: 1) in the Newtonian and relativistic branches are dynamically robust over time scales longer than those for which dipolar stars without self-interactions are seen to decay; 2) in the middle branch migrate to either the Newtonian or the relativistic branch; 3) beyond the relativistic branch decay to black holes. Overall, these results strengthen the observation, seen in other contexts, that self-interactions can mitigate dynamical instabilities of scalar boson star models.

In contrast to energy and angular momentum, electric charge is conserved in mergers of charged black holes. This opens up the possibility for the remnant to have Kerr-Newman parameter ${\chi }^2+{\lambda }^2$ greater than 1 (with $\chi$ and $\lambda$ being the black hole dimensionless spin and dimensionless charge, respectively), which is forbidden by the cosmic censorship conjecture. In this paper, we investigate whether a naked singularity can form in quasicircular mergers of charged binary black holes. We extend a theoretical model to estimate the final properties of the remnant left by quasicircular mergers of binary black holes to the charged case. We validate the model with numerical-relativity simulations, finding agreement at the percent level. We then use our theoretical model to argue that while naked singularities cannot form following quasicircular mergers of nonspinning charged binary black holes, it is possible to produce remnants that are arbitrarily close to the extremal limit.

In this work, we investigate the tidal deformability of a neutron star admixed with dark matter, modeled as a massive, self-interacting, complex scalar field. We derive the equations to compute the tidal deformability of the full Einstein-Hilbert-Klein-Gordon system self-consistently, and we probe the influence of the scalar field mass and self-interaction strength on the total mass and tidal properties of the combined system. We find that dark matter corelike configurations lead to more compact objects with smaller tidal deformability, and dark matter cloudlike configurations lead to larger tidal deformability. Electromagnetic observations of certain cloudlike configurations would appear to violate the Buchdahl limit. The self-interaction strength is found to have a significant effect on both mass and tidal deformability. We discuss observational constraints and the connection to anomalous detections. We also investigate how this model compares to those with an effective bosonic equation of state and find the interaction strength where they converge sufficiently.

We provide an emergent universe picture in which the fine-tuning on the initial conditions is replaced by cutoff physics, implemented on a semiclassical level when referred to the universe dynamics and on a purely quantum level for the quantum fluctuations of the inflaton field. The adopted cutoff physics is inspired by polymer quantum mechanics but expanded in the limit of a small lattice step. On a quasiclassical level, this results in modified Poisson brackets for the Hamiltonian universe dynamics similar to a generalized uncertainty principle algebra. The resulting universe is indeed asymptotically Einstein-static, emerging from a finite-volume configuration in the distant past and then properly reconnecting with the most relevant universe phases. The calculation of the modifications of the primordial inflaton spectrum is then performed by treating new physics as a small correction on the standard Hamiltonian of each Fourier mode of the field. The merit of this study is to provide a new paradigm for a nonsingular emergent universe, which is associated with a precise fingerprint on the temperature distribution of the microwave background, in principle observable by future experiments.

We present a new independent pipeline for the Cosmic Microwave Background bispectrum estimation of primordial non-Gaussianity and release a public code for constraining bispectrum shapes of interest based on the Planck 2018 temperature and polarization data. The estimator combines the strengths of the conventional Komatsu-Spergel-Wandelt and modal estimators at the cost of increased computational complexity, which has been made manageable through intensive algorithmic and implementation optimization. We also detail some methodological advances in numerical integration over a tetrapyd—domain where the bispectrum is defined on—via new quadrature rules. The pipeline has been validated both internally and against Planck. As a proof-of-concept example, we constrain some highly oscillatory models that were out of reach in conventional analyses using a targeted basis with a fixed oscillation frequency, and no significant evidence for primordial non-Gaussianity of these shapes is found. The methodology and code developed in this work will be directly applicable to future surveys where we expect a notable boost in sensitivity.

Dark matter–baryon interactions can cool the baryonic fluid, which has been shown to modify the cosmological 21-cm global signal. We show that in a two-component dark sector with an interacting millicharged component, dark matter–baryon scattering can produce a 21-cm power spectrum signal with acoustic oscillations. The signal can be up to 3 orders of magnitude larger than expected in $\mathrm{\Lambda }\mathrm{CDM}$ cosmology, given realistic astrophysical models. This model provides a new-physics target for near-future experiments such as HERA or NenuFAR, which can potentially discover or strongly constrain the dark matter explanation of the putative EDGES anomaly.

The electroweak sphaleron process breaks the baryon number conservation within the realms of the Standard Model of particle physics. Recently, it was pointed out that its decoupling may provide the out-of-equilibrium condition required for baryogenesis. In this paper, we study such a scenario taking into account the baryon-number wash-out effect of the sphaleron itself to improve the estimate. We clarify the amount of $CP$ violation required for this scenario to explain the observed asymmetry.

The central compact object within HESS J1731-347 possesses unique mass and radius properties that renders it a compelling candidate for a self-bound star. In this research, we examine the capability of quark stars composed of color superconducting quark matter to explain the latter object by using its marginalized posterior distribution and imposing it as a constraint on the relevant parameter space. Namely, we investigate quark matter for $N_f=2,3$ in the color superconducting phase, incorporating perturbative QCD corrections, and we derive their properties accordingly. The utilized thermodynamic potential of this work possesses an MIT bag model formalism with the parameters being established as flavor-independent. In this instance, we conclude the favor of the 3-flavor over the 2-flavor color superconducting quark matter and we isolate our interest on the former, without neglecting the possible favor of the latter in a different framework. The parameter space is further confined due to the additional requirement for a high maximum mass ($M_{\mathrm{TOV}}\ge 2.6M_{\odot }$), accounting for GW190814’s secondary companion. Our study places significant emphasis on the speed of sound and the trace anomaly which was proposed as a measure of conformality [Y. Fujimoto et al., Phys. Rev. Lett. 129, 252702 (2022).]. We conclude that it is possible for color-flavor locked quark stars to reach high masses without violating the conformal bound or the $⟨\mathrm{\Theta }{⟩}_{{\mu }_B}\ge 0$, provided that the quartic coefficient ${\alpha }_4$ does not exceed an upper limit which depends on the established $M_{\mathrm{TOV}}$. For $M_{\mathrm{TOV}}=2.6M_{\odot }$, we find that the limit reads ${\alpha }_4\le 0.594$. Lastly, a further study takes place on the agreement of color-flavor locked quark stars with additional astrophysical objects including the GW170817 and GW190425 events, followed by a relevant discussion.

I present a new class of nonrelativistic, modified-gravity Modified Newtonian Dynamics (MOND) theories. The three gravitational degrees of freedom of these “TRIMOND” theories are the MOND potential and two auxiliary potentials, one of which emerges as the Newtonian potential. Their Lagrangians involve a function of three acceleration variables: the gradients of the potentials. So, the transition from the Newtonian to the MOND regime is rather richer than in the aquadratic-Lagrangian theory (AQUAL) and the quasilinear MOND theory (QUMOND), which are special cases of TRIMOND, each defined by a Lagrangian function of a single variable. In particular, unlike AQUAL and QUMOND whose deep-MOND limit (DML) is fully dictated by the required scale invariance, here, the scale-invariant DML still requires specifying a function of two variables. For one-dimensional (e.g., spherical) mass distributions, in all TRIMOND theories the MOND acceleration is a (theory specific, but system independent) function of the Newtonian acceleration; their variety appears in nonsymmetric situations. Also, they all make the salient, primary MOND predictions. For example, they predict the same DML virial relation as AQUAL and QUMOND, and thus the same DML $M-\sigma$ relation, and the same DML two-body force. Yet they can differ materially on secondary predictions. Such TRIMOND theories may be the nonrelativistic limits of scalar-bimetric relativistic formulations of MOND, such as BIMOND with an added scalar.

We explore the use of Gibbs sampling in estimating the noise properties of individual pulsars and illustrate its effectiveness using the NANOGrav 11-year dataset. We find that Gibbs sampling noise modeling (GM) is more efficient than the current standard Bayesian techniques (SM) for single pulsar analyses by yielding model parameter posteriors with average effective-sample-size ratio (GM/SM) of 6 across all parameters and pulsars. Furthermore, the output of GM contains posteriors for the Fourier coefficients that can be used to characterize the underlying red noise process of any pulsar’s timing residuals, which are absent in current implementations of SM. Through simulations, we demonstrate the potential for such coefficients to measure the spatial cross-correlations between pulsar pairs produced by a gravitational wave background.

We consider the emission of a photon by a scalar charged particle in a constant and uniform magnetic field. In contrast to the conventional approach with both photon and outgoing charge being assumed to be detected, we study the case where only the charge is detected and investigate the properties of the emitted photon. The background magnetic field is taken into account exactly in the calculations and the charge is described by relativistic Landau states. It is shown that the emitted photon state represents a twisted Bessel beam with a total angular momentum given by $\ell -{\ell }^{\prime }$, where $\ell$ and ${\ell }^{\prime }$ are angular momentum quantum numbers of the initial and final charged particle, respectively. The majority of photons emitted by unpolarized charges, especially in the hard x-ray and $\gamma$-ray range and in critical and subcritical magnetic fields, as compared to the Schwinger value of $H_c=4.4\times {10}^9\mathrm{T}$, turn out to be twisted with $\ell -{\ell }^{\prime }\gtrsim 1$.

Observations of suspected coherent elastic neutrino-nucleus scatterings by dark matter direct detection experiments highlight the need for an investigation into the so-called “neutrino floor.” We focus on the discovery limit, a statistical concept to identify the neutrino floor, and analyze the asymptotic behavior of the profile binned likelihood ratio test statistic where the likelihood is constructed by variate from events in each bin and pull terms from neutrino fluxes. To achieve the asymptotic result, we propose two novel methods: (i) the asymptotic-analytic method, which furnishes the analytic result for large statistics, is applicable for more extra nuisance parameters, and enables the identification of the most relevant parameters in the statistical analysis; (ii) the quasi-Asimov dataset, which is analogous to the Asimov dataset but with improved speed. Applying our methods to the neutrino floor, we significantly accelerate the computation procedure compared to the previous literature, and successfully address cases where the Asimov dataset fails. Our derivation on the asymptotic behavior of the test statistic not only facilitates research into the impact of neutrinos on the search for dark matter, but may also prove relevant in similar application scenarios.

We investigate the Crewther relation at high loop order in a variety of renormalization schemes and gauges. By examining the properties of the relation in schemes other than modified minimal subtraction ($\overline{\mathrm{MS}}$) at the fixed points of quantum chromodynamics we propose a generalization of the Crewther relation that extends the $\overline{\mathrm{MS}}$ construction of Broadhurst and Kataev. A derivation based on the properties of the renormalization group equation is provided for the generalization which is tested in various scenarios.

We study the fermion pair creation phenomenon due to the time dependence of curves, where boundary conditions are imposed on a Dirac field in $2+1$ dimensions. These conditions, which lead to nontrivial relations for the normal component of the fermionic current, depend on the value of a dimensionless parameter. We show that the pair creation effect is maximized for bag boundary conditions, obtained for a particular value of that parameter. The effect is studied in terms of the effective action to extract information on the probability of vacuum decay, using an expansion in powers of the deformation of the curves with respect to straight lines. We demonstrate that the first nontrivial contributions to this process can be obtained from the electromagnetic vacuum polarization tensor for a Dirac field coupled to static boundaries.

We formulate the first-order dissipative anisotropic hydrodynamical theory for a relativistic conformal uncharged fluid, which generalizes the Bemfica-Disconzi-Noronha-Kovtun first-order viscous fluid framework. Our approach maintains causal behavior in the nonlinear regime with or without general relativity coupling, and we derive and analyze the constraints on transport coefficients imposed by causality. We demonstrate the causal and stable behavior of our theory in specific cases, including the discussion of nonlinear causality as well as stability for linearized perturbations. We apply our newly developed first-order anisotropic theory to the Bjorken flow and show how causality and stability impose constraints on the behavior of the early-time attractor.

While the main goal of the J-PARC KOTO experiment is to measure the rare decay $K_L\to {\pi }^0\nu \overline{\nu }$, the unique setup of KOTO raises the possibility to search for physics beyond the Standard Model, in an attempt to probe parts of the parameter space which are not covered by other experiments. In this paper, we test the possibility of using KOTO to search for heavy QCD axions, or axionlike particles, a well-motivated extension of the Standard Model emerging in a variety of models. In particular, we estimate the sensitivity of the current KOTO setup as well as KOTO Step 2 for various benchmark scenarios of axion coupling to the Standard Model. We find that KOTO Step 2 can probe new regions in the parameter space, while KOTO with its current form can only reaffirm the existing bounds. The obtained axion datasets are available as an update of the public code of the alpinist framework, including implementation of KOTO setups in the simulation, allowing for interpretation of various analyses as searches for axions in custom models.

We study the prospect of measuring the electroweak quantum numbers of beyond the Standard Model color sextet particles that decay into same-sign top-quark pairs. Among these particles, the color sextet scalars give rise to top quarks with the same chirality, while the top quarks coming from the color sextet vector would have opposite chirality. This difference gets encoded in the angular distributions of the bottom quarks and leptons originating from the decays of the top quarks. We utilize this feature and the energy distributions of the final-state jets and leptons to distinguish among the three possible color sextet resonances, taking into account various SM background processes at the 13 TeV LHC.