In a recent paper we showed that for eccentric-orbit extreme-mass-ratio inspirals the analytic forms of the leading-logarithm energy and angular momentum post-Newtonian (PN) flux terms (radiated to infinity) can, to arbitrary PN order, be determined by sums over the Fourier spectrum of the Newtonian quadrupole moment. We further showed that an essential part of the eccentricity dependence of the related subleading-logarithm PN sequences, at lowest order in the symmetric mass ratio $\nu$, stems as well from the Newtonian quadrupole moment. Once that part is factored out, the remaining eccentricity dependence is more easily determined by black hole perturbation theory. In this paper we show how the sequences that are the 1PN corrections to the entire leading-logarithm series, namely terms that appear at PN orders $x^{3k+1}{\log }^k(x)$ and $x^{3k+5/2}{\log }^k(x)$ (for PN compactness parameter $x$ and integers $k\ge 0$), at lowest order in $\nu$, are determined by the Fourier spectra of the Newtonian mass octupole, Newtonian current quadrupole, and 1PN part of the mass quadrupole moments. We also develop a conjectured (but plausible) form for 1PN correction to the leading logs at second order in $\nu$. Further, in analogy to the first paper, we show that these same source multipole moments also yield nontrivial parts of the 1PN correction to the subleading-logarithm series, and that the remaining eccentricity dependence (at lowest order in $\nu$) can then more easily be determined using black hole perturbation theory. We use this method to determine the entire analytic eccentricity dependence of the perturbative (i.e., lowest order in $\nu$) 4PN nonlog terms, ${\mathcal{R}}_4(e_t)$ and ${\mathcal{Z}}_4(e_t)$, for energy and angular momentum respectively.

We examine the inertial modes of vibration of a Maclaurin spheroid and determine how they are driven by an external tidal field, either Newtonian (gravitoelectric) or post-Newtonian (gravitomagnetic). The context and motivation for this work come from the realization that inertial modes of rotating neutron stars can be resonantly excited in binary inspirals, with a measurable effect on the phasing of the emitted gravitational waves. We aim to provide additional insights into this phenomenon. We calculate how the frequencies of the relevant inertial modes, and their overlap integrals with the tidal forces, vary as the star’s rotation rate increases, spanning almost the full range between zero rotation and the mass-shedding limit. We prove that a single inertial mode couples to a Newtonian tidal field; overlap integrals with all other modes vanish. We prove also that four inertial modes couple to a post-Newtonian, gravitomagnetic tidal field; overlap integrals with all other modes vanish. Finally, we determine the rather extreme conditions under which the gravitoelectric driving of inertial modes dominates over the gravitomagnetic driving.

We consider particle collisions in the background of a nonextremal black hole. Two particles fall from infinity, particle 1 is fine-tuned (critical), collision occurs in its turning point. The first example is the Reissner-Nordström (RN) one. If the energy at infinity $E_1$ is big enough, the turning point is close to the horizon. Then, we derive a simple formula according to which $E_{\mathrm{c}.\mathrm{m}.}\sim E_1{\kappa }^{-1/2}$, where $\kappa$ is a surface gravity. Thus significant growth of $E_{\mathrm{c}.\mathrm{m}.}$ is possible if (i) particle 1 is ultrarelativistic (if both particles are ultrarelativistic, this gives no gain as compared to collisions in flat space-time), (ii) a black hole is near-extremal (small $\kappa$). In the scenario of multiple collisions the energy $E_{\mathrm{c}.\mathrm{m}.}$ is finite in each individual collision. However, it can grow in subsequent collisions, provided new near-critical particles are heavy enough. For neutral rotating black holes, in case (i) a turning point remains far from the horizon but large $E_{\mathrm{c}.\mathrm{m}.}$ is still possible. Case (ii) is similar to that for collisions in the RN metric. We develop a general theoretical scheme, direct astrophysical applications can be a next step to be studied.

Precision tests of general relativity (GR) can be conducted by observing binary pulsars. Theories with massive fields exist to explain a variety of phenomena from dark energy to the strong $CP$ problem. Existing pulsar binaries, such as the white dwarf-pulsar binary $\mathrm{J}1738+0333$, have been used to place stringent bounds on the scalar dipole emission, and radio telescopes may detect a pulsar orbiting a black hole in the future. In this paper, we study the ability of pulsar binaries to probe theories involving massive scalar and vector fields through the measurement of the orbital decay rate. With a generic framework, we describe corrections to orbital decay rate due to (i) modification of GR quadrupolar radiation and (ii) dipolar radiation of a massive field. We then consider three concrete examples: (i) massive Brans-Dicke theory, (ii) general relativity with axions, and (iii) general relativity with bound dark matter and a dark force. Finally, we apply direct observations of J1738 and simulations of a black hole–pulsar binary to bound theory parameters such as field’s mass and coupling constant. We find new constraints on bound dark matter interactions with PSR J1738, and a black hole–pulsar discovery would likely improve these further. Such bounds are complementary to future gravitational-wave bounds. Regarding other theories, we find similar constraints to previous pulsar measurements for massive Brans-Dicke theory and axions. These results show that new pulsar binaries will continue to allow for more stringent tests of gravity.

The binary black holes (BBHs) formed near the supermassive black holes (SMBHs) in the galactic nuclei would undergo eccentricity excitation due to the gravitational perturbations from the SMBH and therefore merger more efficiently. In this paper, we study the coupling of the three body 1st post-Newtonian (PN) effects with the spin effects from the SMBH in the hierarchical triple system. We extend previous work by including the coupling between the de Sitter precession and the Lense-Thirring precession from the SMBH spin. This coupling includes both the precessions of the inner orbit angular momentum and the Runge-Lenz vector around the outer orbit angular momentum in a general reference frame. We find the change of the (maximal) eccentricity in the neighboring Kozai-Lidov cycles due to spin effects is detectable by LISA in the future. Our general argument on the coupling of the three body 1PN effects in three body systems could be extended to any other situation as long as the outer orbital plane evolves.

We study the cosmological predictions of the dark D-brane model, in which dark matter resides on a D-brane moving in a higher-dimensional space. By construction, dark matter interacts only gravitationally with the standard model sector in this framework. The dark energy scalar field is associated with the position of the D-brane, and its dynamics is encoded in a Dirac-Born-Infeld action. On the other hand, dark matter is identified with matter on the D-brane, that naturally couples to dark energy via a disformal coupling. We analyze the numerical evolution of the cosmological background, highlighting the fact that there are two regimes of interest: one in which the coupling is positive throughout and another in which the coupling is negative at the present. In the latter, there is the enticing possibility of having scenarios in which the coupling is positive for a significant part of the evolution, before decreasing toward negative values. In both cases, the coupling is very small at early times and starts to grow only during the late matter-dominated era. We also derive the equations for the linear cosmological perturbations and an expression for the effective time-dependent gravitational coupling between dark matter particles and present the numerical results for the cosmic microwave background anisotropy and matter power spectra. This allows for a direct comparison of the predictions for the growth of large-scale structure with other disformal quintessence models.

An axion-like field comprising $\sim 10\%$ of the energy density of the Universe near matter-radiation equality is a candidate to resolve the Hubble tension; this is the “early dark energy” (EDE) model. However, as shown in Hill et al., the model fails to simultaneously resolve the Hubble tension and maintain a good fit to both cosmic microwave background (CMB) and large-scale structure (LSS) data. Here, we use redshift-space galaxy clustering data to sharpen constraints on the EDE model. We perform the first EDE analysis using the full-shape power spectrum likelihood from the Baryon Oscillation Spectroscopic Survey (BOSS), based on the effective field theory (EFT) of LSS. The inclusion of this likelihood in the EDE analysis yields a 25% tighter error bar on $H_0$ compared to primary CMB data alone, yielding $H_0=68.54_{-0.95}^{+0.52}\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ (68% C.L.). In addition, we constrain the maximum fractional energy density contribution of the EDE to $f_{\mathrm{EDE}}<0.072$ (95% C.L.). We explicitly demonstrate that the EFT BOSS likelihood yields much stronger constraints on EDE than the standard BOSS likelihood. Including further information from photometric LSS surveys,the constraints narrow by an additional 20%, yielding $H_0=68.73_{-0.69}^{+0.42}\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ (68% C.L.) and $f_{\mathrm{EDE}}<0.053$ (95% C.L.). These bounds are obtained without including local-Universe $H_0$ data, which is in strong tension with the CMB and LSS, even in the EDE model. We also refute claims that Markov-chain Monte Carlo analyses of EDE that omit SH0ES from the combined dataset yield misleading posteriors. Finally, we show that upcoming Euclid/DESI-like spectroscopic galaxy surveys will greatly improve the EDE constraints. We conclude that current data preclude the EDE model as a resolution of the Hubble tension, and that future LSS surveys can close the remaining parameter space of this model.

We explore a novel process in the early Universe in which thermalized photons are converted into gravitons in the presence of strong primordial magnetic fields. It is found that the frequency of generated gravitational waves (GWs) is typically of the order of GHz, and their amplitude can be up to ${\mathrm{\Omega }}_{\mathrm{GW}}{h}^2\sim {10}^{-10}$. If detected with future developments of the technology to explore this frequency region, the produced stochastic GW background enables us to know when and how strong the primordial magnetic fields are generated. From the peak frequency of the GWs, we can also probe the number of relativistic degrees of freedom at that time.

I study the potential role of young massive star clusters (YMCs) and open star clusters (OCs) in assembling stellar-mass binary black holes (BBHs) which would be detectable as persistent gravitational wave (GW) sources by the forthcoming, space-based Laser Interferometer Space Antenna (LISA). The energetic dynamical interactions inside star clusters make them factories of assembling BBHs and other types of double-compact binaries that undergo general relativistic (GR) inspiraling and merger. The initial phase of such inspirals would, typically, sweep through the LISA GW band. This fabricates a unique opportunity to probe into the early inspiraling phases of merging BBHs, which would provide insights into their formation mechanisms. Here, such LISA sources are studied from a set of evolutionary models of star clusters with masses ranging over ${10}^4{M}_{\odot }–{10}^5{M}_{\odot }$ that represent YMCs and intermediate-aged OCs in metal-rich and metal-poor environments of the local Universe. These models are evolved with long-term, direct, relativistic many-body computations incorporating state-of-the-art stellar evolutionary and remnant formation models. Based on models of the local Universe constructed with such model clusters, it is shown that YMCs and intermediate-aged OCs would yield several tens to hundreds of LISA BBH sources at the current cosmic epoch with GW frequencies within ${10}^{-3}-{10}^{-1}\mathrm{Hz}$ and signal-to-noise ratios (S/N) $>5$, assuming a mission lifetime of 5 or 10 years. Such LISA BBHs would have a bimodal distribution in total mass, be generally eccentric ($\lesssim 0.7$), and typically have similar component masses, although mass-asymmetric systems are possible. Intrinsically, there would be thousands of present-day, LISA-detectable BBHs from YMCs and OCs. That way, YMCs and OCs would provide a significant—in fact, the dominant—contribution to the stellar-mass BBH population detectable by LISA. A small fraction, $<5\%$, of these BBHs would undergo GR inspiral to make it to LIGO-Virgo GW frequency band and merge within the mission timespan; $<15\%$ would do so within twice the timespan. LISA BBH source counts for a range of S/N, normalized with respect to the local cluster density, are provided. Drawbacks in the present approach and future improvements are discussed.

Newborn, strongly magnetized neutron stars (so-called magnetars) surrounded by their stellar or merger ejecta are expected to be sources of ultrahigh-energy neutrinos via decay of mesons produced in hadronic interactions of protons which are accelerated to ultrahigh energies by magnetic dissipation of the spindown energy. We show that not only pions and kaons but also charm hadrons, which are typically neglected due to their small production cross sections, can represent dominant contributions to neutrino fluence at ultrahigh energies, because of their short lifetimes, while the ultrahigh-energy neutrino fluence from pion and kaon production is suppressed at early times due to their significant cooling before their decay. We show that the next-generation detectors such as Probe Of Extreme Multi-Messenger Astrophysics (POEMMA), Giant Radio Array for Neutrino Detection (GRAND) and IceCube-Gen2 have a good chance of observing neutrinos, primarily originating from charm hadrons, from nearby magnetars. We also show that neutrinos from nearby magnetar-driven merger novae could be observed in the time interval between ${10}^2\mathrm{s}$ and ${10}^3\mathrm{s}$, where the charm hadron contribution is dominant for neutrino energies above ${10}^8\mathrm{GeV}$, of relevance to next generation detectors. We also comment on potential impacts of the charm hadron contribution to the diffuse neutrino flux.

Recently, a considerable amount of attention has been given to the search for ultralight dark matter by measuring the oscillating length changes in the arm cavities of gravitational wave detectors. Although gravitational wave detectors are extremely sensitive for measuring the differential arm length changes, the sensitivity to dark matter is largely attenuated, as the effect of dark matter is mostly common to arm cavity test masses. Here, we propose to use auxiliary length channels, which measure the changes in the power and signal recycling cavity lengths and the differential Michelson interferometer length. The sensitivity to dark matter can be enhanced by exploiting the fact that auxiliary interferometers are more asymmetric than two arm cavities. We show that the sensitivity to $\mathrm{U}(1{)}_{B-L}$ gauge boson dark matter with masses below $7\times {10}^{-14}\mathrm{eV}$ can be greatly enhanced when our method is applied to a cryogenic gravitational wave detector KAGRA, which employs sapphire test masses and fused silica auxiliary mirrors. We show that KAGRA can probe more than an order of magnitude of unexplored parameter space at masses around $1.5\times {10}^{-14}\mathrm{eV}$, without any modifications to the existing interferometer.

Using the construction of the Fermi frame, the field of a gravitational wave can be described in terms of gravitoelectromagnetic fields that are transverse to the propagation direction and orthogonal to each other. In particular, the gravitomagnetic field acts on spinning particles and we show that, due to the action of the gravitational-wave field, a new phenomenon—which we call gravitomagnetic resonance—may appear. We give both a classical and a quantum description of this phenomenon and suggest that it can be used as the basis for a new type of gravitational-wave detectors. Our results highlight the effectiveness of collective spin excitations, e.g., spin waves in magnetized materials, in detecting high-frequency gravitational waves. Here we suggest that, when gravitational waves induce a precession of the electron spin, power is released in the ferromagnetic resonant mode endowed with quadrupole symmetry of a magnetized sphere. This offers a possible path to the detection of the gravitomagnetic effects of a gravitational wave.

In this work we investigate the effects of the Gribov prescription to get rid of zero-modes of the Faddeev-Popov operator at a one-loop order in perturbation theory in the Landau-DeWitt gauge. Quantum fluctuations are taken around a transverse background gauge field. The one-loop effective action is explicitly computed, and the behavior of the gauge and ghost fields propagators are carefully investigated. At one-loop and for generic transverse background configurations the effective action is found to be not background invariant, as expected, due to a nonvanishing background contribution. The gauge field propagator has the same form as in the case where the background is a trivial field, i.e., with complex conjugate poles, which are modified by the corresponding gap equation. The ghost-anti-ghost propagator still displays its enhanced $\sim p^{-4}$ behavior.

We perform the first dipole picture fit to HERA inclusive cross section data using the full next-to-leading order (NLO) impact factor combined with an improved Balitsky-Kovchegov evolution including the dominant effects beyond leading logarithmic accuracy at low $x$. We find that three different formulations of the evolution equation that have been proposed in the recent literature result in a very similar description of HERA data and robust predictions for future deep inelastic scattering experiments. We find evidence pointing toward a significant nonperturbative contribution to the structure function for light quarks, which stresses the need to extend the NLO impact factor calculation to massive quarks.

The $B$ meson light-cone distribution amplitude is a central quantity governing nonperturbative hadronic dynamics in exclusive $B$ decays. We show that the information needed to describe such processes at leading power in ${\mathrm{\Lambda }}_{\mathrm{QCD}}/m_b$ is most directly contained in its Laplace transform ${\tilde{\varphi }}_{+}(\eta )$. We derive the renormalization-group (RG) equation satisfied by this function and present its exact solution. We express the RG-improved QCD factorization theorem for the decay $B^{-}\to \gamma {\ell }^{-}\overline{\nu }$ in terms of ${\tilde{\varphi }}_{+}(\eta )$ and show that it is explicitly independent of the factorization scale. We propose an unbiased parametrization of ${\tilde{\varphi }}_{+}(\eta )$ in terms of a small set of uncorrelated hadronic parameters.

We extend the standard second order effective chiral Lagrangian of pions and nucleons by considering the coupling to an external gravitational field. As an application we calculate one-loop corrections to the one-nucleon matrix element of the energy-momentum tensor to fourth order in chiral counting, and next-to-leading order tree-level amplitude of the pion-production in an external gravitational field. We discuss the relation of the obtained results to experimentally measurable observables. Our expressions for the chiral corrections to the nucleon gravitational form factors differ from those in the literature. That might require to revisit the chiral extrapolation of the lattice data on the nucleon gravitational form factors obtained in the past.

We consider strategies for using new data sets to probe scenarios in which light right-handed SM fermions couple to a new gauge group, $U(1{)}_{T3R}$. This scenario provides a natural explanation for the light flavor sector scale and a motivation for sub-GeV dark matter. There is parameter space, which is currently allowed, but we find that much of it can be probed with future experiments. In particular, cosmological and astrophysical observations, neutrino experiments, and experiments that search for displaced visible decay or invisible decay can all play a role. Still, there is a small region of parameter space which even these upcoming experiments will not be able to probe. This model can explain the observed $2.4\text{−}3\sigma$ excess of events at the COHERENT experiment in the parameter space allowed by current laboratory experiments, but the ongoing/upcoming laboratory experiments will decisively probe this possibility.

Liquid xenon time-projection chambers are the world’s most sensitive detectors for a wide range of dark matter candidates. We show that the statistical analysis of their data can be improved by replacing detector response Monte Carlo simulations with an equivalent deterministic calculation. This allows the use of high-dimensional undiscretized models, yielding up to $\sim 2$ times better discrimination of the dominant backgrounds. In turn, this could significantly extend the physics reach of upcoming experiments such as XENONnT and LZ, and bring forward a potential $5\sigma$ dark matter discovery by over a year.

We investigate the prospects for real-time detection of solar neutrinos via the charged-current neutrino-nucleus scattering process in liquid xenon time projection chambers. We use a nuclear shell model, benchmarked with experimental data, to calculate the cross sections for populating specific excited states of the cesium nuclei produced by neutrino capture on ${}^{131}\mathrm{Xe}$ and ${}^{136}\mathrm{Xe}$. The shell model is further used to compute the decay schemes of the low-lying $1^{+}$ excited states of ${}^{136}\mathrm{Cs}$, for which there is sparse experimental data. We explore the possibility of tagging the characteristic deexcitation $\gamma$ rays/conversion electrons using two techniques: spatial separation of their energy deposits using event topology and their time separation using delayed coincidence. The efficiencies in each case are evaluated within a range of realistic detector parameters. We find that the topological signatures are likely to be dominated by radon backgrounds, but that a delayed-coincidence signature from long-lived states predicted in ${}^{136}\mathrm{Cs}$ may enable background-free detection of CNO neutrino interactions in next-generation experiments with smaller uncertainty than current measurements. We also estimate the sensitivity as a function of exposure for detecting the solar-temperature-induced line shift in ${}^7\mathrm{Be}$ neutrino emission, which may provide a new test of solar models.