We investigate the potential of precision Higgs factory measurements to discover signatures of a representative model of electroweak symmetry breaking in which the Higgs boson arises as a composite Nambu-Goldstone boson. In this model, as in other models of the “Little Higgs” or Natural Composite Higgs type, the primary perturbations of the Standard Model come from effects of vectorlike top quark partners. We carry out an explicit calculation of the Higgs potential in this model. Applying phenomenological constraints, we are left with a three-dimensional parameter space. We then present results from a complete scan of this parameter space. The region in which there are significant departures from the Standard Model predictions extends to models in which the lightest top quark partner has a mass above 3 TeV. Little Higgs models with such heavy top partners also predict significant deviations from the Standard Model in the top quark electroweak couplings, in particular, in the model studied here, in the $t_L$ coupling to the $Z$ boson.

Quarkyonic matter is expected to play a key role for the transition from hadronic matter to quark matter in compact stars. Within the framework of the relativistic mean-field model and equivparticle model with density-dependent quark masses, we construct the “quark Fermi sea” with a “baryon Fermi surface” to characterize the properties of the quarkyonic matter. In particular, we develop a comprehensive framework to account for the strangeness degrees of freedom, incorporating $\mathrm{\Lambda }$, $\mathrm{\Xi }$, and $\mathrm{\Sigma }$ hyperons as well as strange quarks in a unified quarkyonic framework. Our calculations indicate that the inevitable emergence of hyperons softens the equations of state, leading to a reduction in the equilibrium sound velocity around $n_{\mathrm{b}}\approx 2n_0$, and consequently reducing the masses and radii of neutron stars. When the quark-hadron phase transition is taken into account, the equation of state at high densities exhibits additional softening consistent with current astronomical observational constraints. This softening leads to a maximum equilibrium sound velocity of $v_{eq}^{\max }\approx 0.6c$, which is close to the ultrarelativistic limit of $0.58c$.

Extracting accurate results from neutrino oscillation and cross section experiments requires accurate simulation of the neutrino-nucleus interaction. The rescattering of outgoing hadrons (final state interactions) by the rest of the nucleus is an important component of these interactions. We present a new measurement of proton transparency (defined as the fraction of outgoing protons that emerge without significant rescattering) using electron-nucleus scattering data recorded by the CLAS detector at Jefferson Laboratory on helium, carbon, and iron targets. This analysis uses a new data-driven method to extract the transparency. It defines transparency as the ratio of electron-scattering events with a detected proton to quasi-elastic electron-scattering events where a proton should have been knocked out. Our results are consistent with previous measurements that determined the transparency from the ratio of measured events to theoretically predicted events. We find that the GENIE event generator, which is widely used by oscillation experiments to simulate neutrino-nucleus interactions, needs to better describe both the nuclear ground state and proton rescattering in order to reproduce our measured transparency ratios, especially at lower proton momenta.

A search is performed for lepton-number-violating $B^{-}\to D^{(*)+}{\mu }^{-}{\mu }^{-}$ decays, using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$. No significant signal is observed, and upper limits are set on the branching fractions, $\mathcal{B}(B^{-}\to D^{+}{\mu }^{-}{\mu }^{-})<4.6\times {10}^{-8}$ and $\mathcal{B}(B^{-}\to D^{*+}{\mu }^{-}{\mu }^{-})<5.9\times {10}^{-8}$, at the 95% confidence level.

We present a novel search for dark photon dark matter (DM) using terrestrial magnetic field measurements at frequencies below 100 Hz. Coherently oscillating dark photon DM can induce a monochromatic magnetic field via kinetic mixing with ordinary photons. Notably, for dark photon masses $m_{A^{\prime }}$ around $3\times {10}^{-14}\mathrm{eV}$, the signal can be resonantly amplified within a cavity formed by the Earth’s surface and the ionosphere. We compute the expected signal incorporating the effect of atmospheric conductivity, and derive new upper limits on the kinetic mixing parameter $ϵ$ from long-term geomagnetic data. These limits improve upon previous ground-based constraints in the mass range of $1\times {10}^{-15}\mathrm{eV}\lesssim m_{A^{\prime }}\lesssim 2\times {10}^{-13}\mathrm{eV}$.

The magnetic monopole of a dark sector has been advocated as an appealing dark matter candidate. We revisit the computation of the monopole abundance ${\mathrm{\Omega }}_M$, generated by a thermal phase transition in the minimal ’t Hooft-Polyakov model. We explore the three regimes where the phase transition is second order, weakly first order, or supercooled, identifying the parameter space regions where ${\mathrm{\Omega }}_M$ can match the observed dark matter abundance. However, the dark sector necessarily contains a stable electrically charged particle, namely a massive vector boson, with a calculable abundance ${\mathrm{\Omega }}_{W^{\prime }}$. We show that, under minimal assumptions, ${\mathrm{\Omega }}_{W^{\prime }}$ is always far larger than ${\mathrm{\Omega }}_M$: dark monopoles cannot constitute a sizeable fraction of dark matter.

Quantum gravity (QG) has a natural cutoff given by the Planck scale $M_{\mathrm{pl}}$. However, it is known that the effective field theory (EFT) of gravity can break down at a lower scale, the species scale ${\mathrm{\Lambda }}_s\lesssim M_{\mathrm{pl}}$, if there are light species of particles. Here we point out that there is a third scale ${\mathrm{\Lambda }}_{\mathrm{BH}}\lesssim {\mathrm{\Lambda }}_s\lesssim M_{\mathrm{pl}}$, which marks the inverse length (or the temperature) of the smallest black hole where the EFT gives a correct description of its entropy and free energy. This latter scale is hard to detect from the viewpoint of EFT as it represents a phase transition to a state with lower free energy. We illustrate this using examples drawn from consistent QG landscape. In particular ${\mathrm{\Lambda }}_{\mathrm{BH}}$ gets related to Gregory-Laflamme transition in the decompactification limits of quantum gravity and to the Horowitz-Polchinski solution in the light perturbative string limits. We propose the existence of ${\mathrm{\Lambda }}_{\mathrm{BH}}$ marking the temperature at which neutral black holes undergo a phase transition, as a new Swampland condition for all consistent quantum theories of gravity. In the asymptotic regimes of field space ${\mathrm{\Lambda }}_{\mathrm{BH}}$ is close to the mass scale of the lightest tower but deviates from it as we move inwards in the moduli space.

In this paper, we study the baryons and solitons of chiral and vectorlike $SU(N)$ gauge theories with matter in mixed one- and two-index representations. Focusing on the color-flavor locked (CFL) phase, we compute the topology of the coset of their low-energy effective field theory (EFT). We find that in the chiral models under consideration, skyrmions are always absent. We also show, however, that some of these models admit heavy baryons that are expected to be stable, because their decay into the lighter degrees of freedom of the EFT is forbidden by the unbroken symmetry group. This mismatch suggests that some deeper dynamical mechanism must be responsible with either the instability of the seemingly stable heavy baryons or the unreliability of the Skyrme model in the low-energy EFT. In the vectorlike models all the expected baryons are mirrored by skyrmions. Then we turn to the study of domain walls. We determine some aspects of their dynamics by matching the $\theta$-periodicity anomaly. We find that, for complete CFL, the $\theta$-periodicity anomaly is always matched without introducing new dynamical degrees of freedom in the low-energy EFT. If part of the color group is unbroken, new dynamical degrees of freedom must be added to the low-energy EFT in the domain-wall background with few exceptions.

In a recent paper [J. Podolsky and H. Ovcharenko, Kerr black hole in a uniform magnetic field: An exact solution, Phys. Rev. Lett. 135, 181401 (2025)], a new class of exact spacetimes in Einstein’s gravity describing Kerr black holes immersed in an external uniform magnetic field was proposed. In this work, we study the kinematic effects of spinning test particles orbiting this type of black hole, offering a valid test for particle motion under an external uniform magnetic field. By employing the Mathisson-Papapetrou-Dixon equations, we explore the dynamics of precessing orbits and characteristic orbital types, including circular orbits and innermost stable circular orbits. Our analysis reveals that the external magnetic field can significantly alter the topological structure of the effective potential, modifying orbital stability and potentially eliminating stable circular configurations. Furthermore, we demonstrate that an augmented magnetic field necessitates an increased orbital angular momentum to uphold spinning particles within these prograde characteristic orbits at equivalent radii. Notably, in the near-extremal black hole regime, sufficiently strong magnetic fields completely suppress retrograde circular orbits. These findings uncover the profound impact of magnetic fields on the trajectories of spinning particles, providing valuable theoretical insights into celestial motion in magnetized spacetimes.

When gravitational waves (GWs) propagate near massive objects, they undergo gravitational lensing that imprints lens model dependent modulations on the waveform. This effect provides a powerful tool for cosmological and astrophysical studies. Due to the added parameters of lenses and the uncertainty of lens models, parameter inference for lensed GW events using traditional methods is extremely time-consuming, thus requiring more efficient parameter inference methods. In this work, we explore the use of neural spline flows (NSFs) for posterior inference of blue millilensed GWs, and successfully apply NSFs to the inference of 11-dimensional lens parameters. Our results demonstrate that compared with traditional methods like bilby dynesty that rely on Bayesian inference, the NSF network we built not only achieves inference accuracy comparable to traditional methods for most parameters, but also can reduce the inference time from approximately 3 days to 0.8 s on average. Additionally, the network exhibits strong generalization for the spin parameters of GW sources. It is anticipated to become a powerful tool for future low-latency searches for lensed GW signals.

Extremely large mass-ratio inspirals (XMRIs), formed by brown dwarfs inspiraling into a massive black hole, emit gravitational waves (GWs) that fall within the detection band of future space-borne detectors such as LISA, TianQin, and Taiji. Their detection will measure the astrophysical properties of the massive black hole in the center of our Galaxy (${\text{SgrA}}^{*}$) with unprecedented accuracy and provide a unique probe of gravity in the strong field regime. Here, we estimate the benefit of using the GWs from XMRIs to constrain the Chern-Simons theory. Our results show that XMRI signals radiated from the late stages of the evolution are particularly sensitive to differences between Chern-Simons theory and general relativity. For low-eccentricity sources, XMRIs can put bounds on the Chern-Simons parameter $\zeta$ at the level of ${10}^{-1}$ to an accuracy of ${10}^{-3}$. For high-eccentricity sources, XMRIs can put bounds on the parameter $\zeta$ at the level of ${10}^{-1}$ to an accuracy of ${10}^{-6}$. Furthermore, using the time-frequency Markov Chain Monte Carlo method, we obtain the posterior distribution of XMRIs in the Chern-Simons theory. Our results show that almost all the parameters can be recovered within $1\sigma$ confidence interval. For most of the intrinsic parameters, the estimation accuracy reaches ${10}^{-3}$. For the brown dwarf mass, the estimation accuracy reaches ${10}^{-1}$, while for $\zeta$, the estimation accuracy reaches $\mathrm{\Delta }{\log }_{10}\zeta =0.08$ for high eccentricity sources and 1.27 for low eccentricity sources.

We study the propagation of massive scalar fields in the background of asymptotically flat regular black holes supported by a phantom scalar field with a scalar charge $A$. This parameter regularizes the geometry by removing the central singularity. Focusing on wave dynamics, we analyze scalar perturbations, quasinormal modes, and greybody factors, emphasizing the role of the regularization parameter on the effective potential and the decay properties of the modes. Using WKB methods beyond the eikonal limit, we show that the presence of scalar hair modifies both the oscillation frequencies and damping rates of quasinormal modes. In particular, we demonstrate the occurrence of an anomalous decay rate for massive scalar perturbations, and, above a critical field mass, the longest-lived modes correspond to lower angular momentum, in contrast with the massless case. We derive analytical expressions for the critical mass and study its dependence on the scalar charge and overtone number. Furthermore, we apply the Horowitz-Hubeny method to compute the quasinormal frequencies and show that the results obtained from the WKB and Horowitz-Hubeny approaches exhibit excellent agreement in the regime where both methods are valid. In addition, we compute reflection and transmission coefficients and analyze the corresponding greybody factors, clarifying how regularity effects imprint themselves on black-hole scattering properties. Our results show that regular black holes with scalar hair exhibit distinctive dynamical signatures that can be probed through quasinormal ringing and wave propagation.

We solve analytically the low-frequency s-wave dynamics of a massless scalar field propagating on a Schwarzschild-de Sitter black hole background. A rigorous application of the method of matched asymptotic expansions allows us to connect the scalar’s evolution in the proximity of the black hole horizon with that on cosmological scales. The scattering coefficients, greybody factors, and Wigner time delay are computed explicitly. We consider both small and large black holes, with black hole to cosmological horizon radii parametrically small and of order unity, respectively. This extends previous studies confined to the small black hole regime only. In addition, for small black holes, we perform a calculation that remains agnostic about the relative size between the ratio of the geometry’s horizons and the scalar’s frequency in units of the black hole radius. In this case, we find that they are interchangeable in the greybody factor, which is symmetric under $\omega \leftrightarrow 1/r_c$ (where $\omega$ is the scalar’s frequency and $r_c$ the cosmological horizon radius).

In this paper, we study the gravitational lensing around the static and spherically symmetric D’Agostino-De Falco (DD) black holes, which we recently derived as perturbations of the Schwarzschild geometry within the revised Deser-Woodard theory of nonlocal gravity. We first present general analytical expressions for the deflection angle in both weak- and strong-deflection limits, explicitly relating them to the nonlocal corrections to Schwarzschild spacetime. Subsequently, we analyze lensing observables, such as the post-Newtonian effects and the black hole shadow, to constrain the DD black hole parameter space using current observational bounds. Finally, we perform a joint statistical analysis based on the Fisher information matrix, combining these findings with our previously obtained constraints from quasinormal modes. Our results indicate consistency with general relativity at the $1.13\sigma$ level. This work provides a first assessment of the DD parameter space and offers new insights to probe deviations from Einstein’s gravity in view of future larger datasets.

Following Philcox et al. [Phys. Rev. D 111, 103523 (2025)], we investigate a scenario with a massive partner to the inflaton ($\mathcal{O}(100)$ times the inflationary Hubble scale), in which particles are produced during a narrow time period, leaving characteristic hot or cold spots in the cosmic microwave background (CMB). Using tools developed for thermal Sunyaev-Zel’dovich cluster-finding, we search component-separated Planck PR4 $E$-mode maps for these hot spots, and compare to analogous results in $T$. Our analysis pipeline is validated on simulated observations and gives unbiased constraints for sufficiently large and bright hot spots. At Planck sensitivities, the temperature data are more sensitive to small hot spots, but for sufficiently large hot spots the polarization data are more sensitive. We improve upon earlier work by building a full Poissonian likelihood for the hot spot abundance. We find no strong evidence for primordial hot spots and thereby place novel bounds on the marginal and relevant couplings between the inflaton and massive scalars during inflation, probing physics at energies many orders of magnitude above any feasible terrestrial collider. The bounds derived from our new likelihood improve upon those of the above-mentioned paper by more than an order of magnitude for sufficiently light particles ($M_0\lesssim 100H_I$). We also forecast the inferred bounds on inflationary physics for a search using Atacama Cosmology Telescope (ACT) data, and from an optimistic cosmic-variance-limited experiment (CV), for which $E$-mode data provide stronger constraints than $T$ on nearly all scales. ACT should improve on the Planck constraints by $\gtrsim 10\%$, nearing the CV limit allowed by its sky coverage. Finally, we compare the constraining power of localized searches to that of a power spectrum analysis, and demonstrate that for sufficiently few produced particles the localized search performed herein is dominant.

We demonstrate that the suppression in the lensing power spectrum of the cosmic microwave background (CMB) caused by massive neutrinos can be mimicked by dark matter-baryon interactions at the precision of next-generation CMB experiments. Thus, a determination of neutrino masses from the CMB lensing power spectrum may be compromised. We illustrate the degeneracy for a dark matter-proton cross section $\propto v^{-4}$, which arises in the $t$-channel exchange of an ultralight mediator in the nonrelativistic limit.

A key measure of gravity is the relation between the Weyl potential $\mathrm{\Psi }+\mathrm{\Phi }$ and the matter overdensity ${\delta }_m$, encapsulated as an effective gravitational constant $G_{\mathrm{light}}$ for light motion. Its value, along with possible spatial and temporal variations, is essential for probing physics beyond Einstein gravity. However, the absence of an unbiased proxy for ${\delta }_m$ prevents the direct measurement of $G_{\mathrm{light}}$. In this work, we show that, within a theoretical framework respecting the weak equivalence principle, the dispersion measure (DM) of localized fast radio bursts (FRBs) serve as a good proxy for ${\delta }_m$. We further propose an FRB-based estimator $F_G$ to directly measure $G_{\mathrm{light}}$, combining galaxy-DM of localized FRBs and galaxy-weak lensing cross-correlations. With a conservative cut $k\le 0.1h/\mathrm{Mpc}$, the measurement can achieve a precision of $\lesssim 10\%\sqrt{{10}^5/N_{\mathrm{FRB}}}$ over ten equal-width redshift bins at $z\lesssim 1$. The major systematic error, arising from the clustering bias of electrons traced by the FRB DM, remains subdominant at the 5% level. It can be further mitigated to the $\lesssim 1\%$ level, based on the gastrophysics-agnostic behavior that the clustering bias of total baryons (ionized diffuse gas, stars, neutral hydrogen, etc.) approaches unity at sufficiently large scales. Therefore, FRBs shed light on gravitational physics across spatial and temporal scales spanning 20 orders of magnitude.

Pair-instability supernovae leave behind no compact remnants, resulting in a predicted gap in the distribution of stellar black-hole masses. Gravitational waves from binary black-hole mergers probe the relevant mass range and analyses of the LIGO–Virgo–KAGRA catalog (GWTC-4) indicate a possible mass cutoff at $40-50M_{\odot }$. However, the robustness of this result remains unclear. To this end, using full Bayesian parameter estimation, we simulate gravitational-wave catalogs with and without such a mass cutoff and then test whether its presence or absence is correctly inferred with parametric population models. For catalogs similar to GWTC-4, confident identification of a cutoff is not guaranteed, but the best constraints among our simulations are compatible with results from GWTC-4 when the model includes a cutoff. Conversely, spurious identification of a cutoff is unlikely. For catalogs expected by the end of the O4 observing run, uncertainty in the cutoff mass is reduced by $\gtrsim 20\%$, but a cutoff at $40-50M_{\odot }$ yields only a lower bound on the ${}^{12}\mathrm{C}(\alpha ,\gamma {)}^{16}\mathrm{O}$ reaction rate, our most stringent constraints on the S factor at 300 keV being $S_{300}\gtrsim 125$ keV b at 90% credibility. Relative uncertainties on the Hubble parameter $H_0$ from gravitational-wave data alone can still be up to 100%. We also analyze GWTC-4 with the nonparametric pixelpop population model, finding that some mass features are more prominent than in parametric models but a sharp cutoff is not required. However, the parametric model passes a likelihood-based predictive test in GWTC-4 and the pixelpop results are consistent with those from our simulated catalogs with a cutoff. Such tests are necessary to make astrophysical claims from gravitational-wave catalogs.

The chiral plasma instability (CPI) has been invoked as a possible mechanism for generating primordial magnetic fields in the Universe and ultrastrong fields in neutron stars. We investigate chiral dynamos where the chirality imbalance is pumped by a source on a timescale $t_0$ and show that the CPI rate $\gamma$ is limited to ${\gamma }_0/(1+{\mathcal{Q}}^2)$, where $\mathcal{Q}=({\gamma }_0{t}_0{)}^{1/3}$ and ${\gamma }_0$ corresponds to models with instantaneously created chirality imbalance $(t_0=0)$. We then find that chiral flipping with rate ${\mathrm{\Gamma }}_{\mathrm{f}}$ hinders the chiral dynamo if ${\mathrm{\Gamma }}_{\mathrm{f}}>{\gamma }_0/(1+{\mathcal{Q}}^2)$ and completely suppresses it if ${\mathrm{\Gamma }}_{\mathrm{f}}>{\gamma }_0/(1+{\mathcal{Q}}^{3/2})$. Realistic $t_0$ typically give $\mathcal{Q}\gg 1$, which makes the dynamo greatly vulnerable to suppression by chiral flipping. The suppression is strong in protoneutron stars and may be (barely) avoided near the electroweak transition in the early Universe.

We discuss the impact of the recent EPOS.LHC-R hadronic interaction model on the scenario in which most of the cosmic rays with energies above 5 EeV originate in the nearby Centaurus A radiogalaxy. The heavier composition inferred from this hadronic model has important implications for the interpretation of the spectral features and for the anisotropies. In particular, the amount of H and He present above the ankle is now very suppressed. The elements of the Carbon-Nitrogen-Oxygen group from the source play a predominant role in the instep region just above the ankle, while the elements of the Si and Fe groups contribute significantly in the suppression region of the energy spectrum above 50 EeV. The lack of He from the source above the ankle also leads to a smaller expected anisotropy around the Cen A direction at energies of 10 to 20 EeV. The expected dipolar anisotropy in different energy bins above 4 EeV is well consistent with the measurements for appropriate values of the extragalactic turbulent magnetic field and source lifetime. The overall fit to the different observables improves considerably with the new hadronic model. A new method is introduced to extract the information on the cosmic-ray masses from that of the depth of the maximum development of the air showers, which significantly improves the existing method.