We report an updated constraint on the Solar System quadrupole parameter $Q_2$, which encodes the external field effect predicted by modified gravity versions of the modified Newtonian dynamics (MOND) paradigm. Using the dataset employed to compute the DE440 planetary ephemerides and estimating it simultaneously with other parameters included in the planetary ephemerides, we find $Q_2=(1.6\pm 1.8)\times {10}^{-27}{\mathrm{s}}^{-2}$ ($1\sigma$), representing an improvement of 40% over previous estimates. We also show explicitly that the contribution to the MOND prediction of $Q_2$ from the Solar System’s largest planet, Jupiter, is at the 0.05% level, validating the approximation of retaining only the Sun in theoretical calculations. With this new constraint on $Q_2$, we update previously acknowledged tensions with external galaxy rotation curves, now leading to discrepancies at the $3-15\sigma$ level depending on the detailed mass modeling or the subset of galaxies considered. Within the Milky Way itself, the $Q_2$ constraint imposes an upper bound of only 2% (at 95% confidence) on the MOND boost to the galactic radial acceleration (i.e., the ratio of the observed over baryonic Newtonian acceleration) at the position of the Sun, in strong tension with current observational limits. The updated $Q_2$ posterior finally confirms that Solar System measurements provide stronger constraints than current wide-binary data on classical modified gravity versions of MOND.

Current and forthcoming galaxy redshift surveys, such as DESI and Euclid, are going to bring cosmological analysis to an unprecedentedly exquisite level of precision in the determination of the cosmological parameters. However, these efforts require a high degree of control over theory and systematics, to obtain unbiased results. In this sense, the cosmic variance associated to finite-volume effects represents a major challenge and should adequately accounted for. In this work, we revisit the definition of cosmic variance and develop a novel framework to describe it using a “galaxy biasing” formalism. In particular, we use halo/galaxy Eulerian perturbation theory to relate the density field from an arbitrary cosmic realization to its counterpart having statistical properties reproducing the ensemble average, introducing a new set of bias parameters. We then apply this idea to the description of the nonlinear shift of baryon acoustic oscillations (BAO), disentangling the source of uncertainty from cosmic variance and galaxy biasing associated with the measurement of the BAO scale. We finally check our analytical argument against cosmological variance-suppressed $N$-body simulations, finding an expected reduction in the uncertainty on the BAO peak position. We conclude that extra care should be used when inferring cosmological information from perturbative approaches involving the estimation of bias parameters and propose new practical strategies to optimally leverage the novel formulation of cosmic variance presented herein in cosmological analysis.

We investigate the impact of massive neutrinos on cosmological models in which dark energy, described by a quintessence scalar field $\varphi$ with an exponential potential, interacts with dark matter through both energy and momentum transfers. Previous analyses have shown that the inclusion of low-redshift data tends to favor the detection of a pure momentum transfer between the dark sectors, consistent with the fact that such a transfer generically suppresses the growth of cosmic structures. Since massive neutrinos also reduce matter clustering, a potential degeneracy between the interaction parameters and the neutrino mass may arise. After updating the observational constraints on the model parameters obtained in earlier studies, we investigate the effect of allowing the neutrino mass to vary. We find that the detection of momentum transfer degrades once massive neutrinos are included. This occurs because a new degeneracy emerges between the neutrino mass and the parameter governing the energy exchange between dark energy and dark matter. Our findings differ from previous results in the literature, where the detection of momentum transfer was reported to be robust against varying neutrino masses. This suggests that the robustness of such detections depends on the underlying model and should therefore be carefully reassessed for each specific interacting scenario.

Previous work showed that ultralight-dark-matter solitons can provide dynamical friction for supermassive black-hole binaries, suppressing low-frequency power in the pulsar-timing-array gravitational-wave background and constraining the particle mass and effective ultralight-dark-matter fraction. Here we extend that analysis by comparing the predictive performance of four models: simplified and realistic ultralight-dark-matter implementations, a phenomenological environmental-hardening model, and a gravitational-wave-only model. We use Bayesian leave-one-out cross-validation on the five lowest pulsar-timing-array frequency bins. The phenomenological model gives the largest expected log predictive density, but its advantage over the other models is not large compared with the estimated standard errors. The current data therefore do not decisively prefer one model overall. The clearest pairwise result is within the ultralight-dark-matter framework: The simplified model outperforms the realistic implementation in all five frequency bins. Current pulsar-timing-array data are therefore compatible with ultralight-dark-matter-induced low-frequency suppression, but do not yet distinguish ultralight-dark-matter significantly from more generic environmental descriptions of supermassive-black-hole-binary evolution.

The current network of gravitational wave detectors has already revealed hundreds of compact binary coalescences (CBCs), including binary neutron stars, binary black holes, and black hole–neutron star systems. As detector sensitivity improves, the superposition of these signals is expected to form an astrophysical background that becomes increasingly relevant for future observatories. In third-generation detectors such as the Einstein Telescope (ET), this background will be most prominent at low frequencies, potentially affecting the search for continuous gravitational waves (CWs) from spinning neutron stars. In this work, we evaluate the impact of the CBC background on CW detection using the Frequency-Hough pipeline, with a focus on the low-frequency performance in ET sensitivity conditions. Through realistic simulations of the unresolved CBC background, we find that it acts as an additional noise source, most strongly affecting the detection of CW signals around 7 Hz worsening the FH sensitivity by about 7–10%.

We derive and showcase a novel approach to approximating Fourier transforms in higher dimensions, focusing specifically on the case of 2D radially concentrated (“ringlike”) functions. We first reduce the problem to that of evaluating the Hankel transforms of each angular mode of the image and then use our focal expansion to approximate these remaining Hankel transforms. Our method provides a single approximation that remains accurate from small to large spatial frequencies, bridging regimes where moment-based or large-frequency asymptotic expansions are individually reliable. We explore a series of examples, showing that the leading focal term provides an accurate global approximation for a broad range of functions. We demonstrate the utility of this approximation by examining the interferometric response for toy models of a black hole’s “photon ring,” highlighting the application to experiments designed to measure this feature such as the Black Hole Explorer.

The Jeans model is a semianalytical approach to modeling self-interacting dark matter (SIDM) that works remarkably well to reproduce the spherically averaged halo profiles from observations and simulations of relaxed galaxies and galaxy clusters. However, SIDM halos are not spherically symmetric in general since they respond to nonspherical baryon distributions and retain nonsphericity from their initial collapse. In this work, we generalize the Jeans model to describe SIDM density profiles and halo shapes beyond spherical symmetry. Observational tests via halo shapes are especially important for testing SIDM in massive galaxies, $M_{200}\sim {10}^{12}–{10}^{13}{M}_{\odot }$, where SIDM and collisionless dark matter halos can have indistinguishable spherically averaged profiles but distinct halo shapes. We validate our model by comparing to cosmological simulations with baryons for both SIDM with $\sigma /m=1{\mathrm{cm}}^2/\mathrm{g}$ and collisionless cold dark matter. Our approach differs from previous work in this direction, taking into account the fact that multiple scatterings are required to impact the shape of the halo, as well as being computationally inexpensive to implement. The nonspherical Jeans model can be used in conjunction with halo shape observations (e.g., from gravitational lensing or x-ray data) to directly constrain dark matter self-interactions.

We present the first directed searches for long-transient and continuous gravitational waves from ultralight vector boson clouds around known black holes (BHs). We use LIGO data from the first part of the fourth LIGO-Virgo-KAGRA observing run. The searches target two distinct types of BHs and use two new semicoherent methods: hidden Markov model (HMM) tracking for the remnant BHs of the mergers GW230814_230901 and GW231123_135430 (referred to as GW230814 and GW231123 in this study) and a dedicated method using the Band Sampled Data (BSD) framework for the galactic BH in the Cygnus X-1 binary system. Without finding evidence of a signal from vector bosons in the data, we estimate the mass range that can be constrained. For the HMM searches targeting the remnants from GW231123 and GW230814, we disfavor vector boson masses in the ranges [0.94, 1.08] and $[2.75,3.28]\times {10}^{-13}\mathrm{eV}$, respectively, at 30% confidence, assuming a 1% false alarm probability. Although these searches are only marginally sensitive to signals from merger remnants at relatively large distances, future observations are expected to yield more stringent constraints with high confidence. For the BSD search targeting the BH in Cygnus X-1, we exclude vector boson masses in the range $[0.85,1.59]\times {10}^{-13}\mathrm{eV}$ at 95% confidence, assuming an initial BH spin larger than 0.5.

The photon hologram of a one-particle density matrix of a photon gas is derived including the case where the energy of a probe photon is above the electron-positron pair creation threshold. The explicit expressions for the holograms of a photon gas with one-particle density matrix in the form of a single Gaussian and of coherent and incoherent lattices of Gaussians are obtained. The conditions for resonant cones of coherent scattering by coherent and incoherent lattices are found. These conditions turn out to be different. The explicit expressions for the dielectric susceptibility tensor of a photon gas and of a single photon prepared in arbitrary quantum states are derived on the probe-photon mass shell. It is established that a photon gas and a single photon behave in coherent photon scattering as a medium with linear and circular birefringence. This medium is transparent below the electron-positron pair creation threshold and is absorbing otherwise. In the high-energy limit, $\sqrt{s}\gg 2m$, it has the dielectric susceptibility tensor of a birefringent plasma except for a slow logarithmic scaling. It is shown that, for the probe photon energies of order 1 GeV and higher, the energies of target photons of order 1 eV and higher, and the photon gas density such that the classical intensity parameter is of order unity, the hologram of the photon gas can be measured with existing experimental facilities.

In the present work, we have studied the spacelike baryon Sachs form factors in the isospin asymmetric nuclear medium using the vector-meson dominance (VMD) model. The in-medium effects are incorporated through the medium-modified masses of vector mesons which are calculated using the QCD sum rule approach, taking density-dependent scalar quark and gluon condensates as inputs from chiral SU(3) quark mean-field (CQMF) model. The effective magnetic moments of the baryons are also calculated in the CQMF model. In the framework of the VMD model, the photon couples to the nucleons through intermediary vector mesons with the same quantum number as that of a photon. This coupling leads to the relation of isoscalar and isovector Dirac and Pauli form factors which are then used to calculate the Sachs electric and magnetic form factors, which provide physically measurable quantities that represent the electric and magnetic distributions of the baryons. The present work aims to study the effects of asymmetric nuclear matter at finite temperature on the Sachs form factors of baryons in the spacelike region. The electric and magnetic charge radii have also been calculated for the baryons in free space and dense asymmetric nuclear matter. The results obtained have been compared with other available phenomenological models, lattice simulations, and experimental data.

The observation of resonant di-Higgs production, which would strongly suggest the existence of a new heavy neutral scalar $H$, has been searched for extensively at the LHC. In the two-Higgs doublet model (2HDM) with $m_H\gg m_h$, where $h$ is the Higgs boson of mass 125 GeV observed at the LHC, we show that a direct correlation emerges between $\mathrm{Br}(H\to hh)$ and $\mathrm{Br}(H\to VV)$, with $V=Z$, $W$, which depends only on $m_H$ (and $m_V$). In particular, for heavy scalar masses between 500 GeV and 1 TeV, we find that $\mathrm{Br}(H\to hh)/\mathrm{Br}(H\to ZZ)\approx 9.4\pm 0.25$. Moreover, $H\to hh$ is a dominant decay mode over a significant region of the parameter space and serves as the primary probe for a heavy scalar resonance at current and future hadron colliders. The origin of these predictions is most transparent in the Higgs basis, where the term in the scalar potential proportional to ${\mathcal{H}}_1^{†}{\mathcal{H}}_1{\mathcal{H}}_1^{†}{\mathcal{H}}_2$ (and its Hermitian conjugate) generates the leading contributions to the $Hhh$ and $Hhhh$ couplings in the decoupling limit of the 2HDM. Additionally, the latter coupling governs the resonant prompt tri-Higgs production via $H\to hhh$, which is also directly correlated to $H\to hh$ (and $H\to VV$), and can yield rates large enough to be measured at the High-Luminosity LHC.

We examine decoherence in neutrino oscillations induced by an ultralight scalar field coupled to neutrinos. The scalar induces time- and position-dependent shifts in the neutrino mass matrix. Neutrinos sample different field configurations throughout an experimental data-taking period, which leads to damping effects in the oscillation pattern in the form of decoherence. By recasting the neutrino-scalar dynamics within the open quantum systems framework, we establish a mapping between a complete model and phenomenological decoherence approaches. We find that the parameter driving decoherence scales as $L^2/E^2$, where $L$ is the baseline and $E$ is the neutrino energy, as opposed to $L/E$ typically assumed in phenomenological studies of open system approaches to neutrino oscillations.

We present results from the first lattice QCD calculation of the two-pion contributions to the light-quark connected vector-current correlation function obtained from staggered-quark operators. We employ the MILC Collaboration’s gauge-field ensemble with $2+1+1$ flavors of highly improved staggered sea quarks at a lattice spacing of $a\approx 0.15\mathrm{fm}$ with a light sea-quark mass at its physical value. The two-pion contributions allow for a refined determination of the noisy long-distance tail of the vector-current correlation function, which we use to compute the light-quark connected contribution to hadronic vacuum polarization (HVP) with improved statistical precision. We compare our results with traditional noise-reduction techniques used in lattice QCD calculations of the light-quark connected HVP, namely, the so-called fit and bounding methods. We observe a factor of roughly 3 improvement in the statistical precision in the determination of the HVP contribution to the muon’s anomalous magnetic moment over these approaches. We also lay the group theoretical groundwork for extending this calculation to finer lattice spacings with increased numbers of staggered two-pion taste states.

We introduce a learning method for recovering action parameters in lattice field theories. Our method is based on the minimization of a convex loss function constructed using the Schwinger-Dyson relations. We show that score matching, a popular learning method, is a special case of our construction of an infinite family of valid loss functions. Importantly, our general Schwinger-Dyson-based construction applies to gauge theories and models with Grassmann-valued fields used to represent dynamical fermions. In particular, we extend our method to realistic lattice field theories including quantum chromodynamics.

Understanding near-threshold strong interactions is essential for disentangling hadronic molecules and compact multiquark states in heavy-flavor spectroscopy. In this context, the doubly charmed tetraquark candidate $T_{cc}(3875{)}^{+}$ serves as a critical benchmark because it lies very close to the $D^{*}-D$ thresholds. Motivated by the interaction ambiguity reported recently [Phys. Rev. D 113, L031505 (2026)], we evaluate the $D^{*}-D$ scattering lengths and femtoscopic correlation functions for the molecular and molecule-compact admixture assignments of the $T_{cc}(3875{)}^{+}$. We show that, although these scenarios yield similar invariant-mass line shapes, their corresponding femtoscopic correlation functions differ markedly and remain clearly distinguishable for typical particle-emitting sources created at the LHC. Our results indicate that femtoscopy can serve as a sensitive and complementary probe of the near-threshold dynamics of $T_{cc}(3875{)}^{+}$, providing vital theoretical references for future LHC femtoscopy measurements.

The NUCLEUS experiment aims to measure coherent elastic neutrino–nucleus scattering ($\mathrm{CE}\nu \mathrm{NS}$) at unprecedentedly low nuclear recoil energies using gram-scale cryogenic calorimeters operated at the Chooz nuclear power plant in France. Access to recoil energies at the $\mathcal{O}(10\mathrm{eV})$ scale enables $\mathrm{CE}\nu \mathrm{NS}$ studies at extremely low momentum transfer and provides enhanced sensitivity to new physics. In this work, we present sensitivity projections for the upcoming NUCLEUS technical and physics runs, incorporating a data-driven treatment of the low-energy excess (LEE) observed during commissioning. We develop a likelihood framework that exploits reactor-power variation to disentangle signal and background in a low signal-to-background regime and to assess the impact of the dominant systematic uncertainties. For the Technical Run with a 7 g ${\mathrm{CaWO}}_4$ target, we find competitive sensitivity to several scenarios beyond the Standard Model, which do not require a $\mathrm{CE}\nu \mathrm{NS}$ observation. For the Physics Run, assuming complete suppression of the LEE, we project a $4.7\sigma$ observation of $\mathrm{CE}\nu \mathrm{NS}$ with a statistical precision of about 20% in 1 year, enabling a determination of the weak mixing angle at the lowest momentum transfer probed to date with $\mathrm{CE}\nu \mathrm{NS}$ and leading $\mathrm{CE}\nu \mathrm{NS}$-based constraints on the neutrino charge radius and new mediator models.

We show that the LIGO-Virgo-KAGRA verification of Hawking area law carries profound consequences for quantum gravity if such a law is postulated to hold exactly. The observed mergers can be produced in local Stelle gravity and in nonlocal quantum-gravity theories with entire or fractional form factors either by (i) singular Ricci-flat black holes or (ii) possibly regular classical black holes under very restrictive conditions: absence of $R^2$ and $(\text{Riemann}{)}^2$ terms in the action, absence of extra real poles in the graviton propagator, and positivity of its spectral representation. To date, this is the strongest simplification of the ambiguities of this class of theories. We also prove that the classical standard entropy-area law holds as a consequence of Hawking area law and provide a rigorous realization of Barrow’s fractal black holes otherwise.

We propose a method for demonstrating equivalences beyond the saddle point approximation between quantities in quantum gravity that are defined by the Euclidean path integral, without assumptions about holographic duality. The method involves three ingredients: (1) a way of resolving the identity with an overcomplete basis of microstates that is under semiclassical control, (2) a drastic simplification of the sum over topologies in the limit where the basis is infinitely overcomplete, and (3) a way of cutting and splicing geometries to demonstrate equality between two different gravitational path integrals even if neither can be explicitly computed. We illustrate our methods by giving a general argument that the thermal partition function of quantum gravity with two boundaries factorizes. One implication of our results is that universes containing a horizon can sometimes be understood as superpositions of horizonless geometries entangled with a closed universe.

In this paper, we evaluate the graviton character partition function in the Nariai geometry using the quasinormal mode spectrum. The character partition function obtained from the quasinormal modes via the Denef-Hartnoll-Sachdev prescription defines the bulk contribution to the one-loop determinant. The edge-partition function is then computed by subtracting this bulk contribution from the full one-loop partition function on the Euclidean continuation of the Nariai geometry, namely, $S^2\times S^2$. We find that the resulting edge-partition function can be interpreted as a path integral over lower-spin fields localized on the codimension-two surface.

Motivated by the pseudoentropy program, we study timelike subregion complexity within the holographic $\mathrm{complexity}=\mathrm{volume}$ framework, extending previous spatial constructions to Lorentzian boundary intervals. For hyperbolic timelike regions in pure anti–de Sitter (AdS), we compute the enclosed bulk volume and show that, despite the Lorentzian embedding, the resulting complexity is purely real. We generalize the analysis to AdS black brane geometries, where extremal surfaces may either remain entirely outside the horizon or penetrate it, placing their timelike branch inside the black brane interior. In both configurations, the complexity exhibits the same universal UV divergences as the spacelike case, yet it receives no imaginary contribution—highlighting its causal and geometric origin. This reality stands in sharp contrast to the complex-valued pseudoentropy and indicates that holographic complexity retains a genuinely geometric, real character even under Lorentzian continuation.