Black hole (BH) perturbation theory and the scattering models provide a powerful framework for studying gravitational lensing at the wave-optics level. However, conventional calculations encountered two issues: the divergence of the partial-wave series and the divergence of the Poisson spot near the optical axis. These issues hinder the accurate calculation of lensed waveforms and the study of polarization and wave characteristics in the lensing process, especially near the optical axis. This work demonstrates that both divergences stem from the asymptotic expansion of the radial wave function. By computing the scattered wave function at finite radii and avoiding the asymptotic expansion, we naturally obtain convergent results. We compute scalar waves scattered by (1) a weak-gravity body with Newtonian potential and (2) a Schwarzschild BH with Regge-Wheeler potential. In both cases, we analyze the convergence of the partial-wave series and present finite-luminosity diffraction patterns, with a bright Poisson spot. The above calculations are compared with the Kirchhoff diffraction integral in the near-axis regions and give consistent results. Our investigations provide a foundation for studying gravitational wave scattering by BHs and understanding lensing at the wave-optics level.

With the recent announcement by NASA’s Planetary Science and Astrobiology Decadal Survey 2023-2032, a priority flagship mission to the planet Uranus is anticipated. Here, we explore the prospects of using the mission’s radio Doppler tracking equipment to detect gravitational waves (GWs) and other analogous signals related to dark matter (DM) over the duration of its interplanetary cruise. We develop a methodology to stack tracking data and account for time varying detector geometry, thereby constructing the sensitivity of the mission to GWs over the wide frequency range of $3\times {10}^{-9}\mathrm{Hz}$ to ${10}^{-4}\mathrm{Hz}$. We find that the mission has the potential to fill the gap between pulsar timing and space-based-interferometry GW observatories. If improvements in reducing Cassini era noise by a factor of $\mathcal{O}(10)$ are implemented, we forecast the detection of $\mathcal{O}(\mathrm{few})$ individual massive black hole binaries using two independent population models. Additionally, we determine the mission’s sensitivity to both astrophysical and primordial stochastic gravitational wave backgrounds, as well as its capacity to test, or even confirm via detection, ultralight DM models. In all these cases, the tracking of the spacecraft over its interplanetary cruise would enable coverage of unexplored regions of parameter space, where signals from new phenomena in our Universe may be lurking.

The population of black holes observed via gravitational waves currently covers the local Universe up to a redshift $z\lesssim 1$, for the most massive merging binaries, or $z\lesssim 0.25$ for low-mass binary black holes (BBH). Evolution of the BBH mass spectrum over cosmic time will be a significant probe of formation channels and environments. We demonstrate a reconstruction of the BBH merger rate, allowing for general dependence on binary masses and luminosity distance or redshift and accounting for selection effects, via iterative kernel density estimation (KDE) with optimized multidimensional bandwidths. Performing such reconstructions under a range of detailed assumptions, we see no significant evidence for the evolution of BBH masses with redshift, over the range where detected events are available. At most, possible trends towards an increasing merger rate with a redshift for primary masses $m_1\gtrsim 50M_{\odot }$ or towards a decreasing merger rate with a redshift for primary masses $m_1\lesssim 40M_{\odot }$ may be supported. We compare these findings with previous investigations and caution against overinterpreting the current, sparse data. Significantly upgraded detectors and/or facilities, and longer observing times are required to harness any correlations of the BBH mass distribution with redshift.

Gravitational waves (GWs) from coalescing binary black holes (BBHs) can come from different environments. GWs interact gravitationally with astrophysical objects, which makes it possible to use gravitational lensing by objects in the same gravitational system (self-lensing) to learn about their environments. We quantify the probability of self-lensing through the optical depth $\tau$ for the main channels of detectable GWs at frequencies $f_{\mathrm{GW}}\sim (1-{10}^3)\mathrm{Hz}$. We then analyze the detectability of the lensing effect (imprint). In star clusters, the probability of self-lensing by stellar-mass black holes (BHs) is low, $\tau \simeq {10}^{-7}$, even when taking into account nearby BHs in resonant interactions, $\tau \simeq {10}^{-5}$. Additionally, the lensing imprint of a stellar-mass lens (diffraction and interference) is too marginal to be detectable by the LIGO-Virgo-KAGRA detectors and most Einstein Telescope signals. For a massive BH lens in the center of a cluster, the probability can reach $\tau \simeq {10}^{-4}$ either via von Zeipel-Lidov-Kozai induced mergers of BBHs orbiting a central massive BH or BBHs formed as GW captures in single-single interactions in the Bahcall-Wolf cusp of a nuclear cluster. For self-lensing by a supermassive BH for BBHs in the migration trap of an active galactic nucleus (AGN) disk, $\tau \simeq {10}^{-2}$. The imprint of these massive lenses are multiple images that are already detectable. Moreover, self-lensed signals from AGN disks have a distinct linear polarization. The probability depends on the extent of the detectability through the threshold impact parameter $y_{\max }$, which can increase for future detectors. We conclude that constraining the environment of BBHs is possible by combining self-lensing imprints with other waveform signatures such as eccentricity and polarization.

Various theoretical models predict cosmic neutrinos with multi-PeV energies. The recent detection of a $\sim {10}^{17}\mathrm{eV}$ neutrino in the KM3NeT experiment suggests that these energetic particles can be studied with present-day installations. Here, we present upper limits on the flux of astrophysical neutrinos with energies $({10}^{15.5}–{10}^{20})\mathrm{eV}$ obtained with the largest liquid-water neutrino telescope, the Baikal Gigaton Volume Detector (GVD), operation using cascadelike events. We discuss astrophysical implications of these results and constrain several cosmogenic neutrino scenarios using a combination of Baikal-GVD, KM3NeT, IceCube, and Auger data.

The strong gravitational field of a black hole bends light, forming multilevel images, yet extracting precise spacetime information from them remains challenging. In this study, we investigate how gravitational lensing leaves unique and detectable signatures in black hole movies using autocorrelation analysis. By examining the two-dimensional autocorrelation of a movie depicting a hot spot orbiting a Kerr black hole, as viewed by a near-axis observer, we identify a persistent secondary peak structure induced by gravitational lensing. Notably, these secondary peaks converge toward an approximately fixed point in the time-angle lag domain, largely independent of the orbital radius of the hot spot. This key property suggests that combining future flare observations with precise autocorrelation analysis could effectively disentangle lensing effects from orbital dynamics, enabling direct measurement of black hole parameters.

We have studied the viscous properties as well as the Bjorken expansion of a rotating QGP medium. In the noncentral events of heavy-ion collisions, the produced medium can carry a finite angular momentum with a finite range of angular velocity. This rotation can significantly affect various properties, including viscous properties and the expansion of the QGP medium. Using a novel relaxation time approximation for the collision integral in the relativistic Boltzmann transport equation at finite angular velocity, we have calculated the shear and bulk viscosities and compared them with their counterparts in the standard relaxation time approximation within the kinetic theory approach. Our results show that the angular velocity increases both shear and bulk viscosities, suggesting an enhanced momentum transfer within the medium and greater fluctuations in local pressure. This rotational effect on viscosities is more evident at lower temperatures than at higher temperatures. Our analysis also shows that, compared to the standard relaxation time approximation, the shear viscosity is lower while the bulk viscosity is higher in the novel relaxation time approximation for all temperatures. Additionally, some observables related to the flow characteristic, fluid behavior, and conformal symmetry of the medium are markedly impacted due to rotation. We have also studied the hydrodynamic evolution of matter within the Bjorken boost-invariant scenario and have found that the energy density evolves faster in the presence of finite rotation than in the nonrotating case. Consequently, rapid rotation accelerates the cooling process of the QGP medium.

We formulate spin magnetohydrodynamics (MHD) by including the magnetic flux and total angular momentum conservation laws in the hydrodynamic framework. To specify the local angular momentum conservation, we choose the totally antisymmetric spin current. The entropy-current analysis allows for ten dissipative first-order transport coefficients, including anisotropic spin relaxation rates and the conversion rate between a vorticity (shear) to a symmetric stress (antisymmetric torque), as well as anisotropic viscosities and resistivities. By employing the linear-mode analysis, we solve the first-order spin MHD equations to determine the dispersion relations with the complete information of anisotropy retained. Our analytic solutions indicate that the small-momentum expansion is spoiled by blow up of the higher-order terms when the angle between the momentum and the magnetic field approaches the right angle. This also reveals the existence of another expansion parameter, and, in light of it, we provide solutions in an alternative series expression beyond the critical angle. We confirm that these two series expansions work well in the appropriate angle ranges, as compared with numerical results. Building on our findings regarding the breakdown of the small-momentum expansion in first-order theory, we proceed to discussing how these first-order solutions are modified when we include the relaxation dynamics for dissipative modes with the Israel-Stewart framework. We find that, due to the presence of the critical behavior in the first-order solutions, there remains a diffusive window even after the relaxation dynamics is introduced.

We study the longitudinal beam single spin asymmetry $A_{LU}^{\sin {\varphi }_R}$ of dihadron production in the semi-inclusive deep inelastic scattering process with a polarized electron beam scattering off an unpolarized proton target. The asymmetry arises from the convolutions of the twist-3 parton distribution function (PDF) $e(x)$ and the twist-2 dihadron fragmentation function (DiFF) $H_1^{\sphericalangle }$ as well as the twist-2 PDF $f_1(x)$ and the twist-3 DiFF ${\tilde{G}}^{\sphericalangle }$. Using the spectator model calculations for the twist-3 PDF $e(x)$ and the DiFFs $D_1,H_1^{\sphericalangle }$, and ${\tilde{G}}^{\sphericalangle }$, we estimate the beam single spin asymmetry (BSA) $A_{LU}^{\sin {\varphi }_R}$ at the kinematical configuration of CLAS and CLAS12. We find good agreement with $z$- and $M_h$-dependencies data, though $x$- and $Q^2$-dependencies show discrepancies. We include the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution of $e(x)$ and provide predictions for COMPASS, EIC, and EicC. The negligible contribution from $f_1(x)\otimes {\tilde{G}}^{\sphericalangle }$ supports the Wandzura-Wilczek approximation, while our results highlight the importance of QCD evolution in twist-3 PDF analyses.

Motivated by the recent discovery of situations where cosmological fluctuations recohere during inflation, we investigate the relationship between quantum recoherence (late-time purification after a transient phase of decoherence), adiabaticity, and Markovianity. To that end, we study a simple setup of two linearly coupled harmonic oscillators, and compute the purity of one oscillator when the interaction is switched off. We find that there exists a critical value for the coupling strength below which the purity oscillates and above which it decays exponentially. This decay cannot be captured by perturbation theory; hence, decoherence is always a nonperturbative phenomenon. When the interaction is turned off, the purity either freezes to its value prior to the turn-off, or it smoothly goes back to a value very close to one (recoherence). This depends on the rate at which the turn-off occurs. We thus develop a new adiabatic-expansion scheme and find complete recoherence at any finite order in the inverse turn-off time. Therefore, decoherence is always a nonadiabatic effect. The critical value of the turn-off time above which recoherence takes place is then expressed in terms of the other time scales of the problem. Finally, we show that the dynamics of the system is never Markovian, even when decoherence takes place. We introduce a new measure of Markovianity dubbed the Bures velocity and use it to optimize Markovian approximations.

The topological charge density two-point function is computed in a three-flavor effective linear meson model, including contributions from topological sectors with arbitrary charge. A corresponding composite field is introduced via a Hubbard-Stratonovich transformation. In the $\eta –{\eta }^{\prime }$ sector, the model yields very accurate spectroscopy with negligible mixing with the composite field. The resulting topological susceptibility allows for the extraction of a surprisingly large absolute scale for the range of topological fluctuations. When compared with various QCD-based estimates, this indirectly suggests the dominance of higher topologically charged configurations in the ground state.

We study multiloop conformal integrals for four-point correlators of planar $\mathcal{N}=4$ super-Yang-Mills theory, and in particular those contributing to Coulomb branch amplitudes in the ten-dimensional lightlike limit, where linear combinations of such integrals are determined by the large R-charge octagons exactly known from integrability. Exploiting known results for integrands, we review those combinations of dual conformal invariant (DCI) integrals that must evaluate to determinants of ladders, generalizing the simplest cases of Basso-Dixon fishnet integrals; in this way, we summarize all-loop predictions for the integrands (which are extracted from $f$-graphs) contributing to components of Coulomb branch amplitudes, such as next-to-fishnet integrals. Moreover, this exercise produces new “magic identities,” i.e., certain combinations of DCI integrals equal zero, and we enumerate and simplify such identities up to six loops explicitly. On the other hand, most of these individual integrals have not been computed beyond three loops, and as a first step we consider a bootstrap program for DCI integrals based on their leading singularities and the space of pure functions. We bootstrap the 3 nontrivial DCI integrals for four-loop Coulomb branch amplitudes (providing an independent verification of the four-loop magic identity), which all take remarkably simple form as weight-8 single-valued harmonic polylogarithms. We also compute all leading singularities and a large portion of the pure functions for the 34 DCI integrals contributing to five-loop amplitudes, where not only some integrals evaluate to functions beyond harmonic polylogarithms, but they also contain lower-weight pieces individually.

Dark matter with mass in the crossover range between wave dark matter and particle dark matter, around $({10}^{-3},{10}^3)\mathrm{eV}$, remains relatively unexplored by terrestrial experiments. In this mass regime, dark matter scatters coherently with macroscopic objects. The effect of the coherent scattering greatly enhances the accelerations of the targets caused from dark matter collisions by a factor of $\sim {10}^{23}$. We propose a novel torsion balance experiment with test bodies of different geometric sizes to detect such dark-matter-induced acceleration. This method could provide the strongest sensitivity on the scattering cross section between the dark matter and a nucleon in the mass range of $({10}^{-3},1)\mathrm{eV}$.

The $CP$ properties of effective operators are closely related to the spacetime and internal symmetries, such as the flavor symmetry, in the standard model effective field theory (SMEFT). In this work, we utilize the flavor symmetry to organize and reduce numbers of independent Wilson coefficients of the SMEFT operators. We classify the dimension-6 and dimension-8 baryon/lepton-number-conserving operators based on their $CP$ properties. The $U(1{)}^4$ rephasing symmetry is applied to distinguish $CP$-violating and $CP$-odd operators, which leads to reduction of the independent $CP$-violating phases. The $U(3{)}^5$ and $U(2{)}^5$ flavor symmetries let us classify the $CP$-violating phases as the flavor invariants, which can be enumerated by the Hilbert series and obtained explicitly by the Young tensor method. Then after introducing the minimal flavor violation (MFV) hypothesis, we present the flavor structures of the dimension-6 and dimension-8 SMEFT operators under the MFV hypothesis utilizing the spurion method.

With the development of muon magnetic dipole moment (MDM) experiments, particularly the high-precision measurements at Fermilab National Accelerator Laboratory (FNAL), experimental data have become increasingly precise. Up to now, the deviation of muon MDM between the experimental data and the standard model prediction still exists, which may be caused by the new physics contribution. The two loop supersymmetric diagrams can produce important corrections to muon MDM. For many two loop diagrams, we analyze the order of the contribution to select the important two loop diagrams and neglect the tiny one, which is in favor of distinguishing the important two loop diagrams from all the two loop diagrams. In our analysis, we use the mass insertion approximation. There is no rotation matrix during the study and the resulting factors become more intuitive, so the mass insertion method is more suitable for this study of ours.

We present a high-statistics lattice-QCD determination of the kaon gluon parton distribution function and gluon momentum fraction. We use clover valence fermion action to take 1,296,640 kaon-correlator measurements on a highly improved staggered quark ensemble with $a\approx 0.12\mathrm{fm}$ and 310-MeV pion mass generated by the MILC Collaboration. A detailed investigation into the impact of gauge-link smearing on the gluonic matrix elements indicates that five steps of hypercubic smearing offer an effective balance between signal quality and preservation of long-distance physics. We report a nonperturbatively renormalized kaon gluon momentum fraction of $⟨x{⟩}_g^{\overline{\mathrm{MS}},K}=0.557(18{)}_{\mathrm{stat}}(24{)}_{\mathrm{NPR}}(56{)}_{\mathrm{mixing}}$ at $\mu =2\mathrm{GeV}$ in the $\overline{\mathrm{MS}}$ scheme. Using reduced pseudo-Ioffe-time-distribution matrix elements and pseudo-parton-distribution-function (PDF) matching, we extract the kaon gluon PDF and compare with the prediction from the Dyson-Schwinger equation and with the pion PDF obtained from the same ensemble.

We recently reported new results on the ${\gamma }^{(*)}+N(940){\frac{1}{2}}^{+}\to \mathrm{\Delta }(1700){\frac{3}{2}}^{-}$ transition form factors using a symmetry-preserving treatment of a vector $\otimes$vector contact interaction (SCI) within a coupled formalism based on the Dyson-Schwinger, Bethe-Salpeter, and Faddeev equations. In this work, we extend our investigation to the ${\gamma }^{(*)}+N(940){\frac{1}{2}}^{+}\to N(1520){\frac{3}{2}}^{-}$ transition. Our computed transition form factors show reasonable agreement with experimental data at large photon virtualities. However, deviations emerge at low $Q^2$, where experimental results exhibit a sharper variation than theoretical predictions. This discrepancy is expected, as these continuum QCD analyses account only for the quark-core of baryons, while low photon virtualities are dominated by meson cloud effects. We anticipate that these analytical predictions, based on the simplified SCI framework, will serve as a valuable benchmark for more refined studies and QCD-based truncations that incorporate quark angular momentum and the contributions of scalar and vector diquarks.

We generalize the mechanical interpretation of the forces between quark and gluon subsystems, previously studied for the nucleon, to arbitrary higher-spin particles. For spin-0 and spin-$1/2$ particles, this force is characterized by the nonconserved $\overline{c}(t)$ form factor. However, such an interpretation has not yet been established for higher-spin particles due to the intricate structure of the nonconserved energy-momentum tensor (EMT) form factors. By performing a multipole expansion, we identify the physically meaningful combinations of the nonconserved covariant EMT form factors and provide them with a clear mechanical interpretation.

In this work, the production of baryon resonances in the $\gamma p\to \varphi \pi p$ reaction near threshold is investigated within an effective Lagrangian approach. We incorporate intermediate resonances, including $\mathrm{\Delta }(1232)$, $N(1440)$, $N(1520)$, and $N(1535)$, alongside nonresonant background contributions. The results indicate that the reaction is dominated by the $\mathrm{\Delta }(1232)$ excitation near threshold. A key focus of this study is the exploration of the $a_0(980)$ meson exchange in the $\mathrm{\Delta }(1232)$ production, as this reaction offers a unique opportunity to probe the poorly known $\mathrm{\Delta }(1232)N{a}_0$ coupling. We demonstrate that the parity asymmetry ($P_{\sigma }$), accessible through the $\varphi$ meson’s spin density matrix elements, serves as a suitable experimental observable to identify the contribution from the $a_0(980)$ exchange.

We investigate the semileptonic decays of baryons containing double charm or double bottom quarks, focusing on their transitions to single heavy baryons through three-point QCD sum rule framework. In our calculations, we take into account nonperturbative operators with mass dimensions up to five. We calculate the form factors associated with these decays, emphasizing the vector and axial-vector transition currents in the corresponding amplitude. By applying fitting functions for the form factors based on the squared momentum transfer, we derive predictions for decay widths and branching ratios in their possible lepton channels. These findings offer valuable insights for experimentalists exploring semileptonic decays of doubly charmed or bottom baryons. Perhaps they can be validated in upcoming experiments like LHCb. These investigations contribute to a deeper understanding of the decay mechanisms in these baryonic channels.