In light of recent high-precision data taken by the BESIII Collaboration, we reconsider the dipion transition $\psi (3686)\to J/\psi {\pi }^{+}{\pi }^{-}$. The strong pion-pion final-state interactions are taken into account model independently by using dispersion theory. We find that we can reproduce the substructure near the ${\pi }^{+}{\pi }^{-}$ threshold observed experimentally without introducing an extra resonance state. While a helicity-flip amplitude plays an important role for the formation of the dip in the invariant-mass distribution, the virtual exchange of the charmoniumlike exotic $Z_c(3900)$ state improves the fit quality only slightly.

We construct a simple holographic model incorporating higher-order coupling terms for electron self-interactions. It can exhibit typical behavior of a Mott insulator, including a metal-insulator transition and a decrease in dc conductivity with the increase of charge density. In the analysis of ac conductivity, a soft gap is generally observed. Notably, when the dc conductivity approaches zero, the ac conductivity reveals a multipeak structure, which can be attributed to the Mott and charge-transfer gaps observed experimentally in transition metals. With the increase of dc conductivity, the multipeak structure gradually reverts to soft-gap behavior or even metallic conductivity. The accuracy of the numerical result is guaranteed by $\sigma (\omega \to 0)={\sigma }_{dc}$ and sum rules.

We continue to explore the previously suggested dual regime of Yang-Baxter (YB) deformed $\mathrm{O}(2N)$ sigma models, which is a new one-parametric deformation of the $\mathrm{O}(2N)$ model. It can be obtained from the conventional YB deformed $\mathrm{O}(2N+2)$ sigma model by freezing two isometries. The scattering matrix in the nondeformed $\mathrm{O}(n)$ model is known to coincide with the rational ${\mathfrak{so}}_n$-invariant $R$-matrix. For $n=2N$ this rational solution allows for two trigonometric deformations: the usual $D_N^{(1)}$ and the twisted $D_N^{(2)}$. The usual one is known to coincide with the scattering matrix of the conventional YB-$\mathrm{O}(2N)$ model. A natural question to ask is what sigma model corresponds to the twisted solution. In this work we claim that it is precisely our dual regime of YB-$\mathrm{O}(2N)$. We find the corresponding unitarizing function $F_N(\theta )$ explicitly, and, as a bonus, extract some physical properties of this system using the thermodynamic Bethe ansatz technique.

Stellar-mass binaries evolving in the vicinity of supermassive black holes (SMBHs) may be common in the universe, either in active galactic nuclei or in other astrophysical environments. Here, we study in detail the resonant excitation of SMBH modes driven by a nearby stellar-mass binary. The resulting resonant energy fluxes vary with the orbital location and frequency of the binary, exhibiting a rich and complex structure. In particular, we find that the total energy flux radiated to infinity is maximized at a gravitational-wave frequency that is close, but not exactly equal to, the real part of the corresponding quasi-normal-mode frequency. Moreover, as the binary is moved farther away from the SMBH, this offset from the mode frequency becomes increasingly pronounced. In addition, for suitable orientations, the binary can effectively “feed” the light ring of the SMBH, selectively exciting particular oscillation modes. For rotating (Kerr) black holes, the mode spectrum is significantly more intricate; however, individual modes are also less strongly damped, leading to an enhanced—but more difficult to interpret—resonant response.

We present a family of analytic solutions for the nearly equatorial motion of a test particle with precessing spin in Kerr spacetime. We solve the equations of motion up to linear order in the small body’s spin for periodic and homoclinic orbits. At zero order, the particle moves along equatorial geodesics. The spin-curvature force introduces post-geodesic corrections which, for generic spin orientations, cause the precession of the orbital plane. We derive the solutions for eccentric orbits in terms of Legendre elliptic integrals and Jacobi elliptic functions for generic referential geodesics (known as “spin gauges”). Our analytical solutions perfectly match the numerical trajectories obtained by Drummond and Hughes in Phys. Rev. D 105, 124041 (2022), and Piovano et al. in Phys. Rev. D 111, 044009 (2025). Furthermore, we present, for the first time, the solutions for homoclinic orbits for a spinning particle in Kerr spacetime, and the spin-corrections to the location of the separatrix. The homoclinic trajectories are described in closed form using elementary functions. Finally, we introduce a novel parametrization for the motion of a spinning particle, called “fixed eccentricity spin gauge.” This is the only spin gauge in which the corrections to periodic orbits are finite at the geodesic separatrix, and continuously reduce to the last stable orbits under appropriate limits. Our results will be useful for modeling the inspiral and transition-to-plunge phases of asymmetric mass binaries within the two-time-scale framework.

This work establishes a new universal linear correlation between the neutron skin thickness ($\mathrm{\Delta }{R}_{np}$) of heavy isotopic chains and that of the lead isotopic chain, characterized by extraordinary precision ($R^2>0.99$). Through self-consistent Skyrme Hartree-Fock-Bogoliubov calculations, we compute comprehensive ground-state observables, validating our approach against established theoretical models and experimental data. Our central discovery is the robust correlation $\mathrm{\Delta }{R}_{np}(Z,N)=m(Z)\mathrm{\Delta }{R}_{np}(\mathrm{Pb},N)+b(Z)$, which maintains remarkable fidelity across all neutron numbers. This universal correlation, rigorously confirmed across independent theoretical frameworks, establishes the Pb chain as a fundamental baseline for nuclear isovector properties. Calibrated using the PREX-II measurement, this relation tightly constrains the symmetry energy slope parameter $L$. This constraint, in turn, predicts neutron star global properties and tidal deformabilities that show striking consistency with multimessenger astrophysical constraints from the Neutron Star Interior Composition Explorer and LIGO/Virgo. Furthermore, the predicted enhancement of $\mathrm{\Delta }{R}_{np}$ in neutron-rich actinides increases their fission barriers, directly impacting $r$-process nucleosynthesis by suppressing fission recycling and offering a resolution to the long-standing underprediction of the heaviest abundance peak. Collectively, these results provide the essential nuclear physics inputs required to interpret gravitational-wave signals, neutron star observations, and the origin of the heaviest elements, establishing a unified quantitative paradigm from finite nuclei to neutron stars.

The putative dusty torus is a key ingredient of the unification scheme of active galactic nuclei (AGN), but its origin remains a mystery. Here we put forward a new physical model to explain how a large number of small dusty gas clumps form and they collectively appear as a geometrically thick dynamic dusty torus. The circumnuclear hot gas flows toward the central black hole (BH) and forms a rotating disk on subparsec scales. A fraction of inflowing hot gas condenses to form small cold clumps due to thermal instabilities, when the accretion rate is sufficiently high. These cold dusty gas clumps are irradiated by the central accretion disk and reradiate as dust emission mostly in the infrared. We propose that the dusty torus in AGN consists of such cold clumps vertically supported by the radiation force against gravity. For clumps with suitable column density, the vertical component of the BH gravity is in quasistatic equilibrium with the infrared radiation force together with the vertical component of the disk radiation force. Our model is robust in the sense that for any reasonable range of parameters concerning clump vertical dynamical equilibrium a torus exists. We further show that the hot gas in the rotating flow condenses to cold clumps only if its accretion rate is higher than about 1% of the Eddington rate. The radiation force is unable to lift the cold gas clumps up away from the midplane when the luminosity of the disk surrounding the BH is lower than 0.1% of the Eddington luminosity. These two features of our model may provide a physical explanation for the lack of evidence of dusty tori in low-luminosity AGN.

Extended Higgs sectors are often introduced to explain phenomena beyond the standard model (BSM). The existence of multiple scalar fields may cause the Landau pole below the Planck scale. In this case, the low-energy theory may be replaced by an asymptotic-free gauge theory. In this paper, we consider an SU(2) gauge theory with confinement as such an ultraviolet theory of the extended Higgs sectors. We investigate the relation between scalar particle contents at the low energy and group theoretical properties of fundamental fermions of the gauge theory. We find that particle contents of various extended Higgs sectors previously proposed to explain the BSM problems are deduced by each charge assignment of flavor symmetry of the fundamental fermions of the SU(2) gauge symmetry. Our findings may provide a new picture for the ultraviolet completion of the extended Higgs sectors.

The study of the fully heavy tetraquark state helps to better understand the characteristics of compact exotic hadrons formed by quarks and gluons. In this work, we systematically investigate the mass spectra and decay channels of fully heavy tetraquark states using a diquark-antidiquark model based on the one-gluon exchange process. The tetraquark states are treated as compact diquark-antidiquark configurations, denoted as $[QQ][\overline{Q}\overline{Q}]$, where $Q=c$ or $b$. By properly accounting for the Pauli principle, basis wave functions incorporating flavor, color, and spin are constructed. The required model parameters are derived from fitting conventional hadron experimental values and lattice QCD calculations. We calculate the mass spectra and decays of the fully heavy tetraquarks in the lower $S$ and $P$ waves. Our results do not support interpreting $X(6600)$, $X(6900)$, and $X(7200)$ as the $1S$-wave fully charmed tetraquark states. Nevertheless, our analysis suggests that $X(6200)$ can be a good candidate for the $1S$-wave fully charmed tetraquark state with quantum numbers $2^{++}$. Furthermore, we also identify several narrow fully heavy tetraquark states that may be observable in future experiments.

The energy-momentum tensor form factor $D(t)$ is finite and negative in hadronic models and lattice QCD when only strong forces are included. However, when electromagnetic forces are considered, the $D(t)$ of charged hadrons undergoes a dramatic change: at small $t$, it changes sign and diverges like $1/\sqrt{-t}$ as shown for the proton in the classical model by Białynicki-Birula based on residual nuclear forces which can be understood as a mean field approach. We construct an analogous neutron model and show that this framework accurately explains the electromagnetic proton-neutron mass difference. We demonstrate that, after appropriately rescaling the residual nuclear forces, the model can reproduce lattice data on the nucleon $D(t)$ up to $(-t)\lesssim 1{\mathrm{GeV}}^2$ as well as QED effects. Based on this realistic model description, we show that the proton and neutron $D(t)$ form factors are practically indistinguishable down to $(-t)\approx {10}^{-4}{\mathrm{GeV}}^2$, far below what can currently be accessed experimentally. We conclude that in the foreseeable future the $D(t)$ form factors of the proton and neutron will practically look the same in experiments and phenomenology.

We identify two distinct repulsive mechanisms in the Cho-Maison monopole-antimonopole pair (MAP) configuration. Our results show that the Higgs-mediated repulsion exhibits a nonmonotonic dependence on both topological charge and Higgs self-coupling, confirming its topological origin while revealing a mass-controlled range transition that deviates from the exponential form of a Yukawa potential. Simultaneously, the $Z$-boson field generates localized repulsive cores of radius $R_c\approx 0.8m_W^{-1}$, consistent with the weak interaction scale. The collaborative effect of these mechanisms—operating in different physics regimes—counteracts the magnetic attraction, establishing a stabilization paradigm for the Cho-Maison MAP that extends naturally to other topological solitons in the Standard Model.

Flavor hierarchies are organized by a single parameter $B\simeq 5.357$ in a single-flavon Froggatt-Nielsen (FN) framework, in which each effective Yukawa entry arises from the sum of three unit-magnitude messenger chains. We present benchmark complex $\mathcal{O}(1)$ Yukawa matrices that reproduce quark and charged-lepton masses at $M_Z$ as powers of $\epsilon \equiv 1/B$. The organizing principle is a two-over-two ($2/2$) lattice of quadrilateral mass ratios, which maps directly to a rational lattice of FN exponents. Sequential dominance preserves the leading-power exponent matrices, while subleading messenger chains generate entry-dependent complex $\mathcal{O}(1)$ coefficients and provide a UV-friendly origin for $CP$ violation. Neutrino masses are discussed at the level of eigenvalues within the same $B^n$ counting.

Charged and/or rotating black holes in general relativity feature Cauchy horizons, which indicate a breakdown of predictability in the theory. Focusing on spherically symmetric charged black holes, we remark that the inevitability of Reissner-Nordström Cauchy horizon is due to the divergent electromagnetic self-energy of point charges. We demonstrate that any causal theory of nonlinear electrodynamics that regularizes the point charge self-energy also eliminates Cauchy horizons for weakly charged black holes. These black holes feature one (event) horizon and a spacelike singularity, analogous to the Schwarzschild metric. An example with Born-Infeld electrodynamics illustrates how this gives rise to an upper bound on the charge, which we compare to known limits.

Forward muon detection at high-energy muon colliders is crucial for resolving the underlying electroweak process. Detecting these muons is challenging in current detector designs, limited by the shielding required to suppress the beam-induced background. This work proposes using asymmetric beam energies to boost one of the forward muons into the detector acceptance, enhancing the ability to distinguish between $W$- and $Z$-initiated vector boson fusion processes. We demonstrate the capabilities of such an asymmetric collider using vector boson fusion Higgs production at 3 and 10 TeV muon colliders with modest boost asymmetries. Asymmetric beam configurations can partially recover the physics potential lost in forward regions when detector coverage is limited.

The decay $A\to ZH$ is a characteristic signal of two-Higgs-doublet models (2HDMs), where $A$ and $H$ lie primarily within the same $SU(2{)}_L$ multiplet, leading to a coupling of order $g_2$ to the $Z$ boson. The subsequent decay $H\to t{t}^{(*)}$ is particularly promising, as it gives rise to distinct final states involving multiple leptons and $b$-jets. The required splitting between $m_A$ and $m_H$ can naturally occur near the electroweak scale while being consistent with perturbative unitarity. Whereas dedicated ATLAS and CMS searches focused on the region with both top-quarks on-shell, we cover lower masses where one top quark is off-shell by recasting Standard Model $t\overline{t}Z$ measurements of ATLAS and CMS. The obtained limits on $\sigma (A\to ZH)\times \mathrm{Br}(H\to t\overline{t})$ are between 0.12 pb and 0.62 pb. Interestingly, we observe these stringent limits despite a preference (up to $2.5\sigma$) for a nonzero new physics signal, most pronounced around for $m_A\approx 450–460\mathrm{GeV}$ and $m_H\approx 290\mathrm{GeV}$, with a best-fit value of $\sigma (A\to ZH)\times \mathrm{Br}(H\to t\overline{t})\approx 0.3\mathrm{pb}$. This cross section can be accommodated within a top-philic 2HDM for a top-Yukawa coupling of the second Higgs doublet of $0.16\lesssim {\mu }_t\lesssim 0.33$.

We propose a new approach to the quasitopological theory of gravity based on a modified classical double-copy construction. Focusing on static, spherically symmetric configurations, we show that all vacuum solutions of $D$-dimensional quasitopological gravity can be obtained from an auxiliary nonlinear electrodynamics defined in a flat ($D+1$)-dimensional spacetime. The gravitational field equations reduce to an algebraic relation between a primary curvature invariant and the electric field strength, while the remaining dynamics is governed by a Gauss-law constraint for a pointlike charge in the auxiliary space. This correspondence provides a transparent interpretation of higher-curvature gravitational interactions in terms of nonlinear gauge dynamics and explains the absence of higher-derivative terms in the reduced equations. As illustrative examples, we apply the formalism to Born-Infeld- and Hayward-type models, obtaining higher-dimensional regular black-hole solutions with a de Sitter-like core. Our results extend the scope of the double-copy paradigm beyond Einstein gravity and suggest a unifying framework for a broad class of higher-curvature theories.

We reexamine the well-known Israel-Wilson-Perjés (IWP) solution by treating it as a special case of the Bretón-Manko metric for two counterrotating Kerr-Newman masses, and we show in particular that this solution is well behaved and free of naked ring singularities. We also obtain a concise form of the corresponding metric function $\omega$ and of the $\phi$ component of the electromagnetic four-potential. The IWP solution is then compared with two binary configurations of corotating Kerr-Newman sources in the charge equal to mass case to highlight the role of angular momenta, magnetic monopole and dipole moments in achieving equilibrium of charged rotating constituents.

Power-law inflation has stood as a classical model in inflationary cosmology since the early 1980s, prized for its exact analytical solutions and ability to naturally resolve the big bang theory’s horizon and flatness problems through exponential expansion. However, its simplest form appears incompatible with modern precision observations, motivating increasingly complex alternatives. In this work, we demonstrate how previous predictions with power-law inflation considered only a particular solution of the field equations, and derive the complete set of general analytical solutions that satisfy current theoretical and observational constraints. This finding revitalizes power-law inflation as a viable framework, offering new possibilities for cosmological model-building while preserving its original mathematical elegance.

Rare events of large-scale spatially correlated exponential random fields are studied. The influence of spatial correlations on clustering and nonsphericity is investigated. The size of the performed simulations permits to study beyond-7.5-sigma events (one in ${10}^{13}$). As an application, this allows to resolve individual Hubble patches which fulfil the condition for primordial black hole formation. It is argued that their mass spectrum is drastically altered due to cocollapse of clustered overdensities as well as the mutual threshold-lowering through the latter. Furthermore, the corresponding nonsphericities may imply possibly large changes in the initial black hole spin distribution.

The recent measurements from the Atacama Cosmology Telescope (ACT) favor a higher value of the scalar spectral index $n_s$ compared to the Planck data, challenging many well-established inflationary models. In this work, we investigate the viability of polynomial potential inflation in light of the latest ACT data, systematically analyzing cases from $n=2$ to $n=5$. By exploring the parameter space and deriving constraints on the model coefficients, we find that the cubic to quintic models can provide a good fit to the data, while the quadratic model struggles to simultaneously accommodate the ACT data and the requirement of sufficient inflation. Notably, the quintic case ($n=5$) not only matches cosmic microwave background (CMB) observations but also produces an inflection point that simultaneously triggers primordial black hole formation and generates a scalar-induced gravitational wave. These findings establish higher-order polynomial potentials as compelling frameworks and reconcile precision CMB measurements with multimessenger probes of early-universe physics.