Gravitational-wave signals from coalescing compact binaries carry an enormous amount of information about the source dynamics and are an excellent tool to probe unknown astrophysics and fundamental physics. Though the updated catalog of compact binary signals reports evidence for slowly-spinning systems and unequal mass binaries, the data so far cannot provide convincing proof of strongly precessing binaries. Here, we use the gravitational-wave inference library parallel Bilby to compare the performance of two waveform models for understanding the spin-induced orbital precession effects in simulated binary black hole signals. One of the waveform models incorporates both spin-precession effects and subdominant harmonics. The other model accounts for precession but only includes the leading harmonic at quadrupolar order. By simulating signals with varying mass ratios and spins, we find that the waveform model with subdominant harmonics enables us to infer the presence of precession in most cases accurately. On the other hand, the dominant harmonic model often fails to extract enough information to measure precession. In particular, it cannot distinguish a face-on highly-precessing binary from a slowly-precessing binary system irrespective of the binary’s mass ratio. As expected, we see a significant improvement in characterizing precession for edge-on binaries. Other intrinsic parameters also become better constrained, indicating that precession effects help break the correlations between mass and spin parameters. In contrast, spin-precession measurements are prior dominated for equal-mass binaries with face-on orientation, even if we employ a waveform model including subdominant harmonics. In this case, doubling the signal-to-noise ratio does not help to reduce these prior induced biases. As we expect detections of highly-spinning binary signals with misaligned spin orientations in the future, simulation studies like ours are crucial for understanding the prospects and limitations of gravitational-wave parameter inferences.

We analyze the Bianchi I cosmology in the presence of a massless scalar field and describe its dynamics via a semiclassical and quantum polymer approach by adopting three different sets of configurational variables: the natural Ashtekar connections, a set of anisotropic volumelike coordinates and the Universe volume plus two anisotropy coordinates (the latter two sets of variables would coincide in the case of an isotropic Universe). In the semiclassical analysis we demonstrate that the big bounce clearly emerges in all the sets of variables. Moreover, when adopting the proper volume variables (i.e. when defining the Universe volume itself on the polymer lattice) we also derive the exact polymer-modified Friedmann equation for the Bianchi I model. This way, the expression of the critical energy density that includes the anisotropic energylike contribution is obtained, demonstrating that in this set of variables the big bounce has a universal nature (i.e. its critical energy density has a maximum value fixed by fundamental constants and the Immirzi parameter). Finally, a proposal is made to recover the equivalence between the dynamics in the Ashtekar set and in the anisotropic volumelike one, showing that this request is satisfied when a polymer parameter depending on the configurational coordinates is considered. Then, we apply the Arnowitt-Deser-Misner reduction of the variational principle and we quantize the system. We study the resulting Schrödinger-like dynamics only in the Ashtekar variables and in the proper volume ones, stressing that the behavior of the Universe wave packet over time singles out common features with the semiclassical trajectories. However, we show that the standard deviation for the Universe volume operator grows with time. This is a signal of the spreading of the Bianchi I wave packet and hence of the importance of the quantum fluctuations in order to properly study the big bounce picture.

We derive fourth post-Newtonian (4PN) contributions to the Keplerian type parametric solution associated with the conservative dynamics of eccentric, nonspinning compact binaries. The solution has been computed while ignoring certain zero-average, oscillatory terms arising due to 4PN tail effects. We provide explicit expressions for the parametric solution and various orbital elements in terms of the conserved energy, angular momentum and symmetric mass ratio. Canonical perturbation theory (along with the technique of Padé approximant) is used to incorporate the 4PN nonlocal-in-time tail effects within the action-angles framework. We then employ the resulting solution to obtain an updated inspiral-merger-ringdown (IMR) waveform that models the coalescence of nonspinning, moderately eccentric black hole binaries, influenced by Hinder et al. [Phys. Rev. D 98, 044015 (2018)]. Our updated waveform is expected to be valid over a similar parameter range as the above reference. We also present a related waveform which makes use of only the post-Newtonian equations and thus is valid only for the inspiral stage. This waveform is expected to work for a much larger range of eccentricity ($e_t\lesssim 0.85$) than our full IMR waveform (which assumes circularization of the binaries close to merger). We finally pursue preliminary data analysis studies to probe the importance of including the 4PN contributions to the binary dynamics while constructing gravitational waveform templates for eccentric mergers.

Gravitational waves emitted by inner binaries in hierarchical triple systems are interesting astrophysical candidates for space-based detectors like the Laser Interferometer Space Antenna, LISA. In the presence of a third body, such as a supermassive black hole, an inner binary consisting of intermediate mass black holes can undergo oscillations in eccentricity and inclination angle due to the Kozai-Lidov mechanism. In this work, we construct analytic gravitational waveforms in the Fourier domain, taking into account the Kozai-Lidov effect at Newtonian (leading) order. Using multiple-scale analysis, we make use of the separability of timescales to combine the effects of both Kozai-Lidov oscillations and radiation reaction. We assume small eccentricity and present analytic solutions to the evolution of the other orbital elements. Our analytic calculation can be systematically extended to higher orders in eccentricity, and can be used to construct inspiral-merger-ringdown models. The imprint on the waveform, due to this combined evolution, is computed under the stationary-phase approximation. We find that the oscillations leave a clear signature on the Fourier amplitude of the waveform while leaving a measurable imprint on the gravitational wave phase, and that our analytic results are consistent with numerics. Further, with our study of the astrophysical parameters of the hierarchical triple, we outline potential source candidates, along with potential implications for gravitational wave data analysis.

Given the nongraph-changing Hamiltonian $\widehat{H[N]}$ in loop quantum gravity (LQG), $\widehat{H[N]}$, the coherent state expectation value of $\widehat{H[N]}$, admits a semiclassical expansion in ${\ell }_{\mathrm{p}}^2$. In this paper, we explicitly compute the expansion of $\widehat{H[N]}$ to the linear order in ${\ell }_{\mathrm{p}}^2$ on the cubic graph with respect to the coherent state peaked at the homogeneous and isotropic data of cosmology. In our computation, a powerful algorithm, supported by rigorous proofs and several theorems, is developed to overcome the complexity in the computation of $\widehat{H[N]}$. Particularly, some key innovations in our algorithm substantially reduce the complexity in computing the Lorentzian part of $\widehat{H[N]}$. Moreover, with the algorithm developed in the present work, we can compute the expectation value of arbitrary monomial of holonomies and fluxes on one edge up to arbitrary order of ${\ell }_{\mathrm{p}}^2$. Finally, some quantum correction effects resulted from $\widehat{H[N]}$ in cosmology are discussed at the end of this paper.

Mixed fermion-boson stars are stable, horizonless, everywhere-regular solutions of the coupled Einstein-(complex, massive) Klein-Gordon-Euler system. While isolated neutron stars and boson stars are uniquely determined by their central energy density, mixed configurations conform to an extended parameter space that depends on the combination of the number of fermions and (ultralight) bosons. The wider possibilities offered by fermion-boson stars could help to explain the tension in the measurements of neutron star masses and radii reported in recent multimessenger observations and nuclear physics experiments. In this work, we construct equilibrium configurations of mixed fermion-boson stars with realistic equations of state for the fermionic component and different percentages of bosonic matter. We show that our solutions are in excellent agreement with multimessenger data, including gravitational-wave events GW170817 and GW190814 and x-ray pulsars PSR $\mathrm{J}0030+0451$ and PSR $\mathrm{J}0740+6620$, as well as with nuclear physics constraints from the PREX-2 experiment.

In this work, a possible description for quantum dynamics of the cuscuton within the sigma-model approach is presented. Lower order perturbative corrections and the structure of divergences are found. Motivated by the results generated by the perturbative approach, we investigate the existence of topological structures in the cuscutonlike model. The structures we study are, first, kinklike configurations in two dimensional spacetime, second, vortex solutions in three dimensional one with gauge field ruled by the Maxwell term. In fact, to show the existence of kink solutions one needs to introduce a standard dynamics term in the cuscutonlike model. Then, a numerical approach (interpolation method) is used and the solution of the scalar field is presented. On the other hand, for the study of topological vortices, we reorganized the energy density to obtain, for convenience, equations similar to those canonical vortex structures, namely, the Maxwell-Higgs model. In fact, even for this particular case, we observed the existence of structures with localized energy and quantized magnetic flux in a given topological sector. We also show that when the model does not spontaneously break the symmetry, the $(2+1)D$ model only admits the so-called nontopological field solutions.

Chiral symmetry breaking comes from the mass dynamically generated through interaction of Dirac fermions for both quantum electrodynamics in $(2+1)\mathrm{D}$ (QED3) and $(3+1)\mathrm{D}$ (QED4). In QED3, the presence of a Chern-Simons (CS) parameter affects the critical structure of the theory, favoring the symmetric phase where the electron remains massless. Here, we calculate the main effects of a pseudo-Chern-Simons (PCS) parameter $\theta$ into the dynamical mass generation of pseudo–quantum electrodynamics (PQED). The $\theta$ parameter provides a mass scale for PQED at the classical level and appears as the pole of the gauge-field propagator. After calculating the full electron propagator with the Schwinger-Dyson equation in the quenched-rainbow and large-$N$ approximations, we conclude that $\theta$ changes the critical parameters related to the fine-structure constant ${\alpha }_c(\theta )$ and the number of copies of the matter field $N_c(\theta )$, favoring the symmetric phase. In the continuum limit ($\mathrm{\Lambda }\to \infty$), nevertheless, the $\theta$ parameter does not affect the critical parameters. We also compare our analytical results with numerical findings of the integral equation for the mass function of the electron. In the strong-coupling limit (with a fine-structure constant $\alpha \gg 1$), the PCS mass vanishes and the system presents the same criticality as QED3.

We study a relativistic fluid with longitudinal boost invariance in a quantum-statistical framework as an example of a solvable nonequilibrium problem. For the free quantum field, we calculate the exact form of the expectation values of the stress-energy tensor and the entropy current. For the stress-energy tensor, we find that a finite value can be obtained only by subtracting the vacuum of the density operator at some fixed proper time ${\tau }_0$. As a consequence, the stress-energy tensor acquires nontrivial quantum corrections to the classical free-streaming form.

A generic low-energy prediction of string theory is the existence of a large collection of axions, commonly known as a string axiverse. Axions also have a natural cosmological production mechanism, vacuum misalignment, making them well-motivated dark matter (DM) candidates. Much work on axion production has considered the case of a single free axion, but in a realistic axiverse, string axions are expected to be distributed densely over many orders of magnitude in mass and to interact with one another through their joint potential. In this paper, we show that nonlinearities in this potential lead to a new type of resonant energy transfer between axions with nearby masses. This resonance generically transfers energy from axions with larger decay constants to those with smaller decay constants and leads to a multitude of signatures. These include enhanced direct detection prospects for a resonant pair comprising even a small subcomponent of dark matter, and boosted small-scale structure if the pair is the majority of DM. Near-future iterations of experiments such as ADMX and DM Radio will be sensitive to this scenario, as will astrophysical probes of DM substructure.

Bound-state formation can have a large impact on the dynamics of dark matter freeze-out in the early Universe, in particular for colored coannihilators. We present a general formalism to include an arbitrary number of excited bound states in terms of an effective annihilation cross section, taking bound-state formation, decay, and transitions into account, and derive analytic approximations in the limiting cases of no or efficient transitions. Furthermore, we provide explicit expressions for radiative bound-state formation rates for states with arbitrary principal and angular quantum numbers $n,\ell$ for a mediator in the fundamental representation of $SU(3{)}_c$, as well as electromagnetic transition rates among them in the Coulomb approximation. We then assess the impact of bound states within a model with Majorana dark matter and a colored scalar $t$-channel mediator. We consider the regime of coannihilation as well as conversion-driven freeze-out (or coscattering), where the relic abundance is set by the freeze-out of conversion processes. We find that the region in parameter space where the latter occurs is considerably enhanced into the multi-TeV regime. For conversion-driven freeze-out, dark matter is very weakly coupled, evading direct and indirect detection constraints but leading to prominent signatures of long-lived particles that provide great prospects to be probed by dedicated searches at the upcoming LHC runs.

We compute the ${\mathrm{\Pi }}_u$ and ${\mathrm{\Sigma }}_u^{-}$ hybrid static potentials in SU(3) lattice gauge theory using four different lattice spacings ranging from $a=0.040\mathrm{fm}$ to $a=0.093\mathrm{fm}$. We provide lattice data points for quark-antiquark separations as small as 0.08 fm, where the $a$-dependent self-energy as well as lattice discretization errors at tree level of perturbation theory and at leading order in $a^2$ have been removed. We also investigate and exclude possibly present systematic errors from topological freezing, due to the finite spatial lattice volume and from glueball decays. Moreover, we provide corresponding parametrizations of the potentials, which can e.g. be used for Born-Oppenheimer predictions of heavy hybrid mesons.

We consider the axial-vector form factors of the baryon octet in flavor-SU(3) chiral perturbation theory. The baryon octet and decuplet and the pseudoscalar-meson octet are included as explicit degrees of freedom. We explore the use of on-shell meson and baryon masses in the one-loop contributions to the axial-vector form factors and focus on a consistent treatment in terms of chiral power counting. The convergence properties of such an approach are scrutinized. We discuss the potential for comparison to upcoming QCD lattice data.

We propose a two-stage strategy to search for new long-lived particles that could be produced at the CERN LHC, become trapped in detector material, and decay later. In the first stage, metal rods are exposed to LHC collisions in an experimental cavern. In the second stage, they are immersed in liquid argon at a different location, where out-of-time decays could be detected. Using a benchmark of pair-produced long-lived gluinos, we show that this experiment would have unique sensitivity to gluino-neutralino mass splittings down to 3 GeV, in previously uncovered lifetimes of days to years.

We present a search for the decays of $B^0$ mesons into a final state containing a $\mathrm{\Lambda }$ baryon and missing energy. These results are obtained from a $711{\mathrm{fb}}^{-1}$ data sample that contains $772\times {10}^{6}B\overline{B}$ pairs and was collected near the $\mathrm{\Upsilon }(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We use events in which one $B$ meson is fully reconstructed in a hadronic decay mode and require the remainder of the event to consist of only a single $\mathrm{\Lambda }$. No evidence for these decays is found, and we set 90% confidence level upper limits on the branching fractions in the range $2.1–3.8\times {10}^{-5}$. This measurement provides the world’s most restrictive limits, with implications for baryogenesis and dark matter production.

We consider the class of spinning particle theories, whose quantization corresponds to the continuous helicity representation of the Poincare group. The classical trajectories of the particle are shown to lie on the parabolic cylinder with a lightlike axis irrespectively to any specifics of the model. The space-time position of the cylinder is determined by the values of momentum and total angular momentum. The value of helicity determines the focal distance of parabolic cylinder. Assuming that all the world lines lying on one and the same cylinder are connected by gauge transformations, we derive the geometrical equations of motion for the particle. The timelike world paths are shown to be solutions to a single relation involving the invariants of trajectory up to fourth order in derivatives. Geometrical equation of motion is non-Lagrangian, but it admits equivalent variational principle in the extended set of dynamical variables. The lightlike paths are also admissible on the cylinder, but they do not represent the classical trajectories of this spinning particle. The classical trajectories of massless particle (with zero helicity) are shown to lie on hyperplanes, whose space-time position depends on momentum and total angular momentum.

We study the correspondence that connects the space of solutions of general relativity (GR) with that of Ricci-based gravity theories (RBGs) of the $f(R,Q)$ type in the metric-affine formulation, where $Q=R_{(\mu \nu )}{R}^{(\mu \nu )}$. We focus on the case of scalar matter and show that when one considers a free massless scalar in the GR frame, important simplifications arise that allow one to establish the correspondence for arbitrary $f(R,Q)$ Lagrangian. We particularize the analysis to a quadratic $f(R,Q)$ theory and use the spherically symmetric, static solution of Jannis-Newman-Winicour as seed to generate new compact objects in our target theory. We find that two different types of solutions emerge, one representing naked singularities and another corresponding to asymmetric wormholes with bounded curvature scalars everywhere. The latter solutions, nonetheless, are geodesically incomplete.

We demonstrate that the near horizon symmetries of black holes in Einstein-Yang-Mills (EYM) theory are generated by an infinite-dimensional algebra that contains, in addition to supertranslations and superrotations, a non-Abelian loop algebra. This means that the Virasoro-Kac-Moody structure of EYM in asymptotically flat spacetimes has an exact analog in the near horizon region.

Primordial black holes in the solar mass range are a possibly significant component of dark matter. We show how an argument relating the deflection of light by such black holes in the density spike likely to exist around the M87 supermassive black hole, combined with the high resolution observations of the EHT Collaboration, can lead to strong limits on the primordial black hole mass fraction in an astrophysically relevant mass range. The results depend on the model assumed for the dark matter spike and suggest the interest of further understanding of such spikes as well as further high resolution observations on supermassive black holes.

In this work we generalize the idea of a gravitational phase transition, or GPT, at late times [M. Farhang and N. Khosravi, Phys. Rev. D 103, 083523 (2021)] to allow for a modified gravity scenario in the early Universe as well. The original GPT was shown to simultaneously relax the $H_0$ and ${\sigma }_8$ tensions and Planck internal inconsistencies. However, the primary results from GPT predictions implied disagreement with the data from the baryonic acoustic oscillations (BAO). Here we investigate whether the generalized GPT scenario could address the Hubble tension in the presence of the BAO data as well. We find that, despite the vastly enlarged gravitational parameter space, the BAO data strongly prefer the $\mathrm{\Lambda }\mathrm{CDM}$ paradigm with a low inferred Hubble constant, $68.03\pm 0.76\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$, in tension with the local $H_0$ measurements from Riess et al. [Astrophys. J. 876, 85 (2019)], $H_0=74.03\pm 1.42\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$. This failure of the generalized GPT scenario to host both various early and late datasets is of significance and noticeably shrinks the space of possible gravitational solutions to the Hubble tension.