We investigate whether the discrepancy between observed galactic rotation curves and those predicted from baryonic matter can be interpreted as the manifestation of an emergent entropic force. Starting from a minimal statistical framework, we derive an effective radial force from a stationary solution of the Fokker-Planck equation under simple and physically motivated assumptions. We confront this Fokker-Planck entropic (FPE) model with high-quality rotation curves from the SPARC database, performing a systematic comparison with standard halo profiles, including Navarro-Frenk-White (NFW), Burkert, and pseudoisothermal models. The FPE model provides fits of equivalent or improved statistical quality compared to traditional profiles, while yielding stellar mass-to-light ratios within physically consistent ranges, in contrast to NFW and Burkert fits that often approach prior limits. Beyond reproducing rotation curves, the model naturally gives rise to strong correlations between its characteristic parameter and global galaxy properties, including the flat rotation velocity and infrared luminosity. These relations are consistent with well-known empirical scaling laws such as the Tully-Fisher relation, suggesting that the proposed framework captures key aspects of the underlying dynamics. Our results indicate that a minimal entropic-force description, grounded in statistical mechanics, can account for galactic rotation curves while simultaneously encoding their scaling relations, offering a complementary and physically motivated perspective to standard dark matter halo interpretations of galaxy rotation curves.

Pulsars possess strong dipole magnetic fields that can source axion fields through the axion-photon interaction. Pulsars may therefore be surrounded by axion field configurations oscillating with the pulsar’s rotational period. These axions could be detected by observing their effect on the polarization of the pular’s emission. In this paper, we use time resolved observations of the optical polarization of the Crab pulsar to place bounds on the axion-photon coupling, demonstrating the potential of time resolved pulsar birefringence in the search for axions.

The exterior of magnetized black hole mimickers can be modeled as the Schwarzschild vacuum spacetime combined with a dipole magnetic field. We show that surprisingly, such magnetized mimickers can demonstrate strong signatures as a result of charged particle motion. For arbitrary values of magnetic repulsion, bound and curled near-equatorial trajectories are allowed inside the photon sphere at $r/M=3$. Furthermore, high-energy particles can be magnetically repulsed in the region $2.32<r/M<2.45$. On the other hand, a very fine tuning of the magnetic repulsion and particle motion constants is necessary for motion in off-equatorial belts or tori at $r/M<3$. The particle motion is demonstrated for the case of the sole Lorentz force and with the inclusion of the radiative backreaction force.

The trace anomaly $\mathrm{\Delta }$ is an important quantity that measures the broken conformal symmetry in neutron star matter. In this work, we present quasiuniversal relations that connect the stellar profile of $\mathrm{\Delta }$ to the compactness, moment of inertia, and tidal deformability of neutron stars. We apply the quasiuniversal relations to determine the trace anomaly profiles for PSR $\mathrm{J}0030+0451$ and PSR $\mathrm{J}0740+6620$ based on their mass-radius measurements. We also analyze PSR J0737-3039A according to its moment of inertia inferred from Bayesian modeling of nuclear equation of state. A recent multimessenger constraint on the tidal deformability is also studied, resulting in an estimate value of the trace anomaly ${\mathrm{\Delta }}_c=0.1770_{-0.0432}^{+0.0365}$ at the center of a $1.4M_{\odot }$ canonical neutron star. It is expected that more precise observations from both electromagnetic and gravitational-wave channels in the future will provide tighter constraints on the behavior of $\mathrm{\Delta }$ inside neutron stars.

The standard parity-doublet model with its mass-mixing mechanism fails to describe the axial charge $g_A$ of the nucleon. While $g_A=1$ in the original Gell-Mann–Levy model, which reproduces the Adler-Bell-Jackiw anomaly of QCD, in the presence of a chirally invariant baryon mass the mass mixing leads to $g_A<1$, whereas phenomenologically it is about 1.28. We propose to remedy this problem by introducing kinetic-mixing terms corresponding to meson-baryon derivative couplings, similar in spirit to the two-mixing-angle scenario of the $\eta -{\eta }^{\prime }$ mixing. This extended parity-doublet model contains five parameters in the effective baryonic Lagrangian. Three of them can be determined by using the empirical results for the axial charge of the nucleon together with the masses of the nucleon and its parity partner, the $N^{*}(1535)$ resonance. We discuss various options of how to determine the remaining parameters, touching upon the mass of both parity partners if the chiral condensate is put to zero, the mass of the nucleon in the chiral limit, and the values of meson-baryon coupling constants related to the decays of the resonance to pion-nucleon and sigma-nucleon.

A general spin-resolved momentum distribution of electron-positron pairs produced in strong external fields is derived by combining the covariant spin projection operator and the Dirac-Heisenberg-Wigner formalism. The result shows that the spin-resolved and helicity-resolved momentum distributions given in previous literature are actually two special cases of it. By numerically studying pair production in a spatially homogeneous circularly polarized electric field with its rotation axis along the $z$ axis, it is found that for any spin-direction unit vector, when the $z$ component of the unit vector vanishes, the number densities of produced spin-up and spin-down particles are equal, while their momentum distributions have some asymmetry. When the $z$ component of the unit vector is nonzero, there is a difference of 1–3 orders of magnitude in the number densities of spin-up and spin-down particles induced by angular momentum transfer in multiphoton absorption. Moreover, as the electric field strength increases or the field frequency decreases, the asymmetry between the spin-up and spin-down particle number densities decreases rapidly. These results offer an approach to study general spin states in vacuum pair production and enhance our understanding of angular momentum transfer from fields to matter in extreme environments.

We show that the leading nonanalytic terms in the small-$t$ expansion of the energy-momentum tensor form factors of an electrically charged particle in QED can be correctly derived in a classical model of the electron by Białynicki-Birula. Based on the lucidity of the employed exactly solvable model, we comment also on the recently proposed concept of a regularized proton $D$-term.

We investigate the collider signatures of the minimal framework for quark-lepton unification at a scale not far from the electroweak symmetry breaking scale. This theory predicts a rich spectrum of new fields, including one vector leptoquark, two scalar leptoquarks, a color-octet scalar, and an additional Higgs doublet. Neutrino masses are generated via the inverse seesaw mechanism, facilitating viable matter unification at the low scale. We find that this theory predicts that in many cases the dominant leptoquark decays are to the third generation Standard Model quarks and leptons. We identify key experimental signatures at the Large Hadron Collider, evaluate and discuss the limits from current measurements, and outline potential strategies for probing this theory in the near future.

In this work, the production mechanisms of the hyperon resonances $\mathrm{\Lambda }(1405)$ and $\mathrm{\Lambda }(1520)$ in ${\pi }^{-}p$ scattering are investigated within an effective Lagrangian approach incorporating Regge trajectories. By including contributions from $t$-channel $K^{*}$ and $u$-channel $\mathrm{\Sigma }$ exchanges, we perform global fits to the total and differential cross sections for ${\pi }^{-}p\to K\mathrm{\Lambda }(1405)$ and ${\pi }^{-}p\to K\mathrm{\Lambda }(1520)$. The results show good agreement with available experimental data. For the total cross section of $\mathrm{\Lambda }(1405)$ production, the $u$-channel contribution is dominant, whereas the $t$-channel contribution plays the primary role in $\mathrm{\Lambda }(1520)$ production. Furthermore, the differential cross sections of the two processes exhibit distinctly different shapes, reflecting their distinct underlying reaction mechanisms. An analysis based on the constituent counting rule indicates that $\mathrm{\Lambda }(1520)$ is consistent with a conventional three-quark configuration, while $\mathrm{\Lambda }(1405)$ shows a clear deviation, suggesting a more exotic structure. Owing to the large branching ratio of ${\mathrm{\Lambda }}^{*}\to \pi \mathrm{\Sigma }$, the Dalitz process ${\pi }^{-}p\to K{\mathrm{\Lambda }}^{*}\to K\pi \mathrm{\Sigma }$ is also calculated. Our results demonstrate that reconstructing ${\mathrm{\Lambda }}^{*}$ via the $K\pi \mathrm{\Sigma }$ final state is experimentally feasible. This study provides important theoretical insights into the production dynamics of these hyperon resonances, and it suggests future high-precision measurements of the $t$-distribution at large momentum transfer at facilities such as AMBER, J-PARC, HIKE, and HIAF, which can further clarify their reaction mechanisms and structural properties.

The femtoscopic $D_s^{+}{D}_s^{-}$ correlations are investigated to predict the signature of the not-yet-established $X(3960)$ state reported by the LHCb Collaboration in three scenarios: resonant, virtual, or bound. In the last two scenarios, it might also be identified as the state $X(3930)$. The formalism employed to generate this structure dynamically is based on the Bethe-Salpeter equation with a general $S$-wave potential. We investigate how the relevant properties and observables characterizing this state—such as the pole position, scattering length, and effective range—might be affected by variations in the model parameters. The amplitudes encoding the distinct interpretations of the $X(3960)$ state are then used as input to calculate the femtoscopic correlation function of the $D_s^{+}{D}_s^{-}$ pair, which is analyzed and discussed.

We study the evolution of neutrinos electroweakly interacting with a rotating matter. The description of neutrinos is based on the Dirac equation in the corotating noninertial frame where matter is at rest. We find the solution of this Dirac equation, where the matter angular velocity is accounted for exactly, for massless neutrinos. In case of massive particles, this solution is obtained for a slowly rotating matter. Our findings are compared with previous research. We consider two applications of our results. First, we compute the electroweak contribution to the vector current of neutrinos along the rotation axis, which is analogous to the chiral vortical effect. This current is shown to be nonzero for both massless and massive particles. Then, we take into account the nonzero mixing between different mass eigenstates. It allows us to study neutrino flavor oscillations in rotating matter and account for noninertial effects. We derive the transition probability which reveals the resonance. These findings generalize the description of neutrino oscillations in a nonmoving matter. Some astrophysical applications are briefly discussed.

It has recently been shown that the Nambu-Goto equation for a string emerges from the junction conditions in three-dimensional gravity. Holographically, gravitational junctions are dual to interfaces in conformal field theory. We demonstrate at the level of linearized gravitational perturbations that each stringy mode of the junction corresponds to a ${\mathcal{H}}_{\mathrm{in}}\to {\mathcal{H}}_{\mathrm{out}}$ quantum map which can be factorized into a scattering matrix involving reflection/transmission and a relative automorphism of the Virasoro algebra, and also a ${\mathcal{H}}_L\to {\mathcal{H}}_R$ map of similar nature. These maps preserve the conformal boundary condition, are independent of the background conformal frame, as in the case of conformal interfaces studied in the literature, and realize a tunable energy transmitter.

We investigate the influence of axion dark matter as a background on the spin-independent axion forces between nucleons. Notably, we find that the potential for axion forces scales from $1/r^3$ in a vacuum-only context to $1/r$ when the background effect is considered. Also, the magnitude of the axion force is substantially amplified in proportion to the number density of axion DM particles. These enhancements significantly improve the constraints on the axion decay constant by several orders of magnitude, across a broad range of axion masses, based on the fifth-force experiments such as the Casimirless and torsion balance tests. This suggests that such experiments are more effective than previously understood in detecting axions.

We present the first rainbow-ladder Dyson-Schwinger equations study of the pion’s chiral-odd, twist-3 parton distribution $e_{\mathrm{q}}(x)$. By deriving a novel Dyson–Schwinger equation for the pion’s quark–quark correlation matrix, we simultaneously extract from it both the unpolarized twist-2 parton distribution function $f_{\mathrm{q}}(x)$ and the twist-3 distribution $e_{\mathrm{q}}(x)$. Our results show that chiral symmetry strongly suppresses the twist-2 component of $e_{\mathrm{q}}(x)$, leaving the genuine twist-3 quark-gluon component dominant and featuring a node. We therefore argue that the genuine twist-3 term can make a substantial contribution to hadronic $e(x)$, producing a nonmonotonic structure that is a clear imprint of intrinsic quark-gluon correlations. We point out that the existence of a humplike feature is compatible with, although not uniquely indicated by, recent proton extractions and awaits more precise determination.

We investigate how nonlocal gravitational couplings from double trace deformation between two asymptotic boundaries of an ${\mathrm{AdS}}_5$ black-brane can lead to the violation of the averaged null energy condition (ANEC). The first-order gravitational perturbations backreact with the background metric at second order, creating a wormhole opening in the context of the Gao-Jafferis-Wall traversable wormhole protocol. The wormhole becomes traversable in both the gravitational shear and sound channels within the hydrodynamic approximation. This shows that dynamical metric perturbations can facilitate information transfer in a purely gravitational setting, with the emergence of $G_{\mathrm{N}}$ indicating the gravitational origin. For the shear channel, we consider three different coupling configurations, whereas for the sound channel, we vary both the speed of sound and the attenuation constant, as these parameters control the wormhole traversability. Furthermore, we obtain a late-time power-law factor in the ANEC using the fitting function and present a generalization that applies to both shear and sound channels. Due to its propagating nature, the sound channel exhibits late-time power-law remnants at low sound speed similar to the vector diffusive probes, but it prefers an exponential decay at higher sound speed similar to the scalar nondiffusive probes, as the power-law exponent weakened with increasing sound speed. For superluminal sound channels, the wormhole opens for an extremely brief duration at late insertion times, rendering it nontraversable.

The quantum expectation value and the stationary noise spectral density for a Fabry-Pérot gravitational-wave detector with a DC (Direct Current) readout scheme are discussed in detail only through the quantum electrodynamics of lasers and the Heisenberg equations of mirrors’ motion. We demonstrate that the initial conditions of the mirrors’ motion concentrate around the fundamental frequency of the pendulum and are not related to the frequency range of our interest. Although, in the ideal case, there is consensus that the shot-noise contribution from the laser to the high-frequency range of the signal-referred noise spectral density decreases as the injected laser power increases, our derived noise spectral density shows that the shot-noise contribution does not decrease. This is due to leakage of the classical carrier field from the classical radiation pressure forces in the Fabri-P’erot cavity, and the carrier field is used as the reference in the DC readout scheme. Since classical radiation pressure acts as a constant force, it shifts the pendulum’s equilibrium point of the mirrors’ motion. To recover the ideal case, we must consider adjusting the interferometer’s tuning point to place the mirrors at their equilibrium positions. We investigate the case where the equilibrium tuning is incomplete and show that the behavior of the above shot noise is due to this incompleteness. We also discuss the maximum deviation of the mirror displacements from the equilibrium point during incomplete tuning to recover a near-ideal case.

In the framework of $F(\mathcal{R},\tilde{\mathcal{R}})$ Einstein-Cartan gravity with an action depending both of the Ricci scalar and the so-called Holst-invariant curvature we consider models that include cubic terms of the latter in the action and study their inflationary behavior. These terms can have a considerable effect either positive or negative in relation to the agreement with present observational data, depending on parameters. In parameter regions where the quadratic models fail to produce results consistent with observational data, the presence of these additional cubic terms can lead to compatible predictions.

The stochastic gravitational-wave background (SGWB) from eccentric stellar-mass binary black holes (SBBHs) holds crucial clues to their origins. For the first time, we employ a Bayesian framework to assess the detectability and distinguishing features of such an SGWB with spaceborne detectors, while accounting for contamination from the Galactic foreground. Our analysis covers eccentric SBBHs from three formation channels: isolated binary evolution, dynamical assembly in globular clusters (GCs), and in active galactic nuclei (AGNs). We find that TianQin, Laser Interferometry Space Antenna (LISA), and Taiji can detect the SGWBs from both isolated and GC-formed SBBHs after four years of operation, with the corresponding SNRs of around 10, 60, and 170. However, these backgrounds are spectrally degenerate with a strictly power-law SGWB. Furthermore, highly eccentric SBBHs formed in AGNs yield an SGWB marked by a spectral turnover and sharp decline. While this feature lowers the SNR by approximately an order of magnitude, it can enable a clear distinction from the strictly power-law background using LISA and Taiji.

The spin-induced quadrupole moment-based test of black hole nature is routinely used to probe the true nature of detected binary signals, assuming a circular orbit. We extend the applicability of the method to binaries in eccentric orbits. Considering simulated signals of varying masses, spins, and signal strengths, we demonstrate how the systematic errors resulting from neglecting orbital eccentricity compare with the statistical errors, using a semianalytic Fisher matrix-based formalism that accounts for both current and future detectors. Further, we quantify the systematic errors by developing a Bayesian inference framework for the current detector network. The inspiral-only aligned-spin gravitational wave waveform model for eccentric binaries, TaylorF2Ecc, is employed. For the current detector network, neglecting an initial eccentricity of $e_0^{\mathrm{inj}}=0.1$ defined at 20 Hz can lead to a serious bias in binary parameter inference. Notably, a nearly equal mass, moderately spinning binary black hole in an eccentric orbit can be identified as a nonblack hole binary with extreme spins and asymmetric masses. We demonstrate the criticality of biased estimates that may arise when neglecting the orbital eccentricity while performing tests of black hole nature and discuss prospects.

Under certain conditions, the oscillating inflaton condensate filling the Universe after inflation can fragment and form so-called oscillons. These long-lived solitonlike field configurations can dominate the Universe for several $e$-folds of expansion, leading to an early matter-dominated phase preceding the standard radiation era. In this paper we show how the rapid final decay of the oscillons leads to an enhanced production of induced gravitational waves, whose energy density can saturate the observational bound on the effective number of relativistic species. We leverage this bound to constrain the inflaton mass, cubic, and quartic self-coupling in generic models that admit oscillon formation, providing novel and complementary constraints in regions of parameter space that are inaccessible with cosmic microwave background observations alone.