The latest cosmological constraints on the sum of the neutrino masses depend on prior physical assumptions about the mass spectrum. To test the accordance of cosmological and laboratory constraints in the absence of such priors, we introduce an effective neutrino mass parameter that extends consistently to negative values. For the $\mathrm{\Lambda }\mathrm{CDM}$ model, we analyze data from Planck, the Atacama Cosmology Telescope, and the Dark Energy Spectroscopic Instrument and find a $2.8–3.3\sigma$ tension with the constraints from oscillation experiments. Motivated by recent hints of evolving dark energy, we analyze the $w_0{w}_a$ and mirage dark energy models, finding that they favor larger masses consistent with laboratory data, respectively, $\sum m_{\nu ,\mathrm{eff}}=0.06_{-0.10}^{+0.15}\mathrm{eV}$ and $\sum m_{\nu ,\mathrm{eff}}=0.04_{-0.11}^{+0.15}\mathrm{eV}$ (both at 68%).

Black holes threaded by massive vector fields can be subject to a superradiant instability, growing a cloud of massive vector particles around it. In this work, we consider what happens if such a dark matter candidate field mimicking a dark photon interacts with an accretion flow onto the black hole. By including a kinetic mixing term with the standard model photon, we extend the commonly used equations of general-relativistic magnetohydrodynamics to a dark photon constituent. The coupling to the dark photon then appears as an effective dynamo term together with a dark Lorentz force acting on the accreting matter. We numerically study the interactions between the superradiant dark photon cloud and the inner accretion flow by solving the coupled system in full numerical relativity. By parameterically varying the mixing parameter between the dark and standard model sector, we provide a first investigation of how the accretion flow could be modified. Depending on the coupling strength, our solutions exhibit increased wind launching, as well as oscillation modes in the disk.

The cosmic neutrino background ($\mathrm{C}\nu \mathrm{B}$) constitutes the last observable prediction of the standard cosmological model, which has yet to be detected directly. In this work, we show how the coherent scattering of neutrinos off dense neutron matter can lead to an additional cooling channel in neutron stars (NSs). We also include the effects of gravitational capture and boosting, but find that the cooling is efficient only in the presence of large overdensities. We further discuss the prediction of a boosted $\mathrm{C}\nu \mathrm{B}$ flux on Earth from nearby NSs and the potential detection prospects in the case of a future nearby galactic supernova. Although currently these ideas do not offer any detection prospects, they can be used to constrain overdensities $\eta \lesssim {10}^{11}–{10}^{14}$ on short length scales $\mathcal{O}(10\mathrm{km})$. We also discuss the impact of new physics scenarios, such as long-range forces, on NS cooling through the $\mathrm{C}\nu \mathrm{B}$.

We study gravitational-wave emission by turbulent flows in accretion disks around spinning black holes or neutron stars. We aim to understand how turbulence can stochastically excite black hole quasinormal ringing and contribute to a stochastic gravitational-wave background from accretion disks around compact objects. We employ general relativistic magnetohydrodynamic simulations and feed them as the source of the Teukolsky master equation to evaluate the gravitational wave energy spectrum of a single source. The stochastic gravitational wave background from accretion disks generated by the population of stellar-mass compact objects is far below the sensitivity of third-generation ground-based detectors. In contrast, the supermassive black hole population, in particular those actively accreting, could lead to ${\mathrm{\Omega }}_{\mathrm{GW}}\sim {10}^{-15}$ in the microhertz. This signal remains well below the sensitivities of pulsar-timing arrays and LISA, making direct observation infeasible.

A computationally efficient method for calculating the transport of neutrino flavor in simulations is to use angular moments of the neutrino one-body reduced density matrix, i.e., “quantum moments.” As with any moment-based radiation transport method, a closure is needed if the infinite tower of moment evolution equations is truncated. We derive a general parametrization of a quantum closure and the limits the parameters must satisfy in order for the closure to be physical. We then derive from multiangle calculations the evolution of the closure parameters in two test cases which we then progressively insert into a moment evolution code and show how the parameters affect the moment results until the full multiangle results are reproduced. This parametrization paves the way to setting prescriptions for genuine quantum closures adapted to neutrino transport in a range of situations.

Using tellurium dioxide as a target, we calculate uncertainties on 90% upper confidence limits of Galilean effective field theory (Galilean EFT) couplings to a weakly interacting massive particle (WIMP) dark matter candidate due to uncertainties in nuclear shell models. We find that these uncertainties in naturally occurring tellurium isotopes are comparable across the different Galilean EFT couplings to uncertainties in xenon, with some reaching over 100%. We also consider the effect these nuclear uncertainties have on estimates of the annual modulation of dark matter from these searches, finding that the uncertainties in the modulation amplitude are proportional to the nonmodulating upper confidence limit uncertainties. We also show that the determination of the modulation phase is insensitive to changes in the nuclear model for a given isotope.

Quantum chromodynamics (QCD)-like theories in which the dark matter (DM) of the Universe is hypothesized to be a thermal relic in the form of a dark pion has been extensively investigated, with most studies neglecting the $CP$-violating $\theta$-angle associated with the topological vacuum. We point out that a nonvanishing $\theta$ could potentially trigger resonant number-changing processes giving rise to the observed relic density in agreement with perturbative unitarity as well as observations of clusters of galaxies. This constitutes a novel production mechanism of MeV DM and an alternative to those relying on the Wess-Zumino-Witten term. Moreover, for specific meson mass spectra, similar resonant scatterings serve as a realization of velocity-dependent self-interacting DM without a light mediator. Explicit benchmark models are presented together with a discussion of possible signals, including gravitational waves from the chiral phase transition associated with the dark pions.

The origins of merging compact binaries observed by gravitational-wave detectors remains highly uncertain. Several astrophysical channels may contribute to the overall merger rate, with distinct formation processes imprinted on the structure and correlations in the underlying distributions of binary source parameters. In the absence of confident theoretical models, the current understanding of this population mostly relies on simple parametric models that make strong assumptions and are prone to misspecification. Recent work has made progress using more flexible nonparametric models, but detailed measurement of the multidimensional population remains challenging. In pursuit of this, we present PixelPop—a high resolution Bayesian nonparametric model to infer joint distributions and parameter correlations with minimal assumptions. PixelPop densely bins the joint parameter space and directly infers the merger rate in each bin, assuming only that bins are coupled to their nearest neighbors. We demonstrate this method on mock populations with and without bivariate source correlations, employing several statistical metrics for information gain and correlation significance to quantify our nonparametric results. We show that PixelPop correctly recovers the true populations within posterior uncertainties and offers a conservative assessment of population-level features and parameter correlations. Its flexibility and tractability make it a useful data-driven tool to probe gravitational-wave populations in multiple dimensions.

We perform five 3D magnetohydrodynamic core-collapse supernova simulations for nonrotating progenitors between $9.5M_{\odot }$ and $24M_{\odot }$. Four of the five models produce explosions while one fails. The exploding models are extended to between 0.9 s and 1.6 s postbounce to study a possible impact of magnetic fields on explosion and remnant properties. Diagnostic explosion energies grow at a similar pace as in previous nonmagnetic models. They reach between 0.11 foe and 0.61 foe, but are still growing by the end of the simulations. Neutron star kicks reach no more than $300\mathrm{km}{\mathrm{s}}^{-1}$, and although these are also still growing, they are unlikely to be in conflict with observed pulsar velocities. Extrapolated neutron star spin periods are between 45 ms and 1.8 s, consistent with observed birth spin rates. Magnetic torques only contribute about 10% to the spin-up of the neutron star. The inclusion of magnetic fields does not provide a mechanism for spin-kick alignment in our simulations. Surface dipole fields are in the range of ${10}^{12}–{10}^{13}\mathrm{G}$, much smaller than the root-mean-square field strength. Different from previous simulations, magnetic fields in the gain region only reach at most $\mathcal{O}(1\%)$ of kinetic equipartition, likely because relatively early shock revival cuts off accretion as a power source for field amplification, which appears to be driven primarily by shear flows at the bottom of the gain region.

The construction of high-resolution shock-capturing schemes is vital in producing highly accurate gravitational waveforms from neutron star binaries. The entropy based flux limiting (EFL) scheme is able to perform fast converging binary neutron star merger simulations reaching up to fourth-order convergence in the gravitational waveform phase. In these results the EFL method was used only in the dynamical evolution of initial data constructed with the Lorene library. Here, we extend the use of the EFL method to the construction of eccentricity reduced initial data for neutron star binaries and present several new binary neutron star simulations resulting from such initial data and show for the first time up to optimal fifth-order convergence in the gravitational waveform phase.

Ultralight axionlike particles (ALPs) can be a viable solution to the dark matter problem. The scalar field associated with ALPs, coupled to the electromagnetic field acts as an active birefringent medium, altering the polarization properties of light through which it propagates. In particular, oscillations of the axionic field induce monochromatic variations of the plane of linearly polarized radiation of astrophysical signals. The radio emission of millisecond pulsars provides an excellent tool to search for such manifestations, given their high fractional linear polarization and negligible fluctuations of their polarization properties. We have searched for evidence of ALPs in polarimetry measurements of pulsars collected and preprocessed for the European Pulsar Timing Array (EPTA) campaign. Focusing on the twelve brightest sources in linear polarization, we searched for an astrophysical signal from axions using both frequentist and Bayesian statistical frameworks. For the frequentist analysis, which uses Lomb-Scargle periodograms at its core, no statistically significant signal has been found. The model used for the Bayesian analysis has been adjusted to accommodate multiple deterministic systematics that may be present in the data. A statistically significant signal has been found in the dataset of multiple pulsars with common frequencies between ${10}^{-8}$ and $2\times {10}^{-8}\mathrm{Hz}$, which can most likely be explained by the residual Faraday rotation in the terrestrial ionosphere. Strong bounds on the coupling constant $g_{a\gamma }$, in the same ballpark as other searches, have been obtained in the mass range between $6\times {10}^{-24}$ and $5\times {10}^{-21}\mathrm{eV}$. We conclude by discussing the problems that can limit the sensitivity of our search for ultralight axions in the polarimetry data of pulsars, and possible ways to resolve them.

We consider SU(2) gauge theory with a scalar field in the fundamental representation. The model is known to contain electric field solutions sourced by the scalar field that are distinct from embedded Maxwell electric fields. We examine the perturbative stability of the solution and identify a region of parameter space where the solution is stable. In the regime where the scalar field has a negative mass squared, the solution has two branches, and we identify an instability in one of the branches.

The Cabibbo-Kobayashi-Maskawa (CKM) matrix, which controls flavor mixing between the three generations of quark fermions, is a key input to the standard model of particle physics. In this paper, we identify a surprising connection between quantum entanglement and the degree of quark mixing. Focusing on a specific limit of $2\to 2$ quark scattering mediated by electroweak bosons, we find that the quantum entanglement generated by scattering is minimized when the CKM matrix is almost (but not exactly) diagonal, in qualitative agreement with observation. With the discovery of neutrino masses and mixings, additional angles are needed to parametrize the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix in the lepton sector. Applying the same logic, we find that quantum entanglement is minimized when the PMNS matrix features two large angles and a smaller one, again in qualitative agreement with observation, plus a hint for suppressed $CP$ violation. We speculate on the (unlikely but tantalizing) possibility that minimization of quantum entanglement might be a fundamental principle that determines particle physics input parameters.

We have formulated a generalized two level model for studying the vacuum electron-positron pair production in strong classical background fields via slowly varying envelope approximation. It can provide momentum spectra with fully spin resolved components for all possible combined spin states of the particle and antiparticle simultaneously in multidimensional time-dependent electric fields. Moreover, we have also investigated the validity of the two level model for fermions (scalar particles) by comparing the results with those by equal-time Dirac-Heisenberg-Wigner (Feshbach-Villars-Heisenberg-Wigner) formalism in different regimes of pair creation, i.e., multiphoton and tunneling dominated mechanisms. It is found that the results are consistent with each other, indicating the good approximation of the two level model. In particular, in terms of the two level model, we found that the contribution of the particle momentum spectra is the greatest when the spin states of the particle and antiparticle are parallel with $S=1$. It is believed that by this two level model one can extend researches on pair production for more different background fields, such as a slowly varying spatial-temporal one. Significantly, we demonstrate that the generalized two level model is equivalent to the spin resolved quantum kinetic theory. In comparison to the equal-time Dirac-Heisenberg-Wigner and Feshbach-Villars-Heisenberg-Wigner methods, the two-level model is simpler and has the potential to deliver faster computational performance.

Special relativity allows massless particles to have states of different integer (or half-integer) helicities that mix under boosts, much like the spin states of a massive particle. Such massless particles are known as “continuous spin” particles (CSPs), a term coined by Wigner, and they are notable for their infinite tower of spin polarizations. The mixing under boosts is controlled by a spin scale $\rho$ with units of momentum. Normally, we assume $\rho =0$. The interactions of CSPs are known to satisfy certain simple properties, one of which is that the $\rho \to 0$ limit generically recovers familiar interactions of massless scalars, photons, or gravitons, with all other polarizations decoupling in this limit. Thus, one can ask if the photon of the Standard Model is a CSP at small but nonzero $\rho$. One concern about this possibility—originally raised by Wigner—is that the infinite tower of polarizations could pose problems for thermodynamics. To address this question, we study the thermal evolution of a CSP photon gas coupled to isothermal matter, across CSP helicity modes and phase space. We find that the structure of the interactions dictated by Lorentz symmetry implies well-behaved thermodynamics. When the CSP photon’s interactions with charged matter are turned on, the primary $h=\pm 1$ helicity modes thermalize quickly, while the other modes require increasingly long time scales to thermalize, set by powers of $T/\rho$. In familiar thermal systems, the CSP photon behaves like the QED photon with small $\rho$- and time-dependent corrections to its effective relativistic degrees of freedom. Sizable departures from familiar thermal behavior arise at energy scales comparable to $\rho$ and could have testable experimental consequences.

We investigate a beyond Standard Model (SM) featuring five new fields. Four fields encompassing three distinct spin states—scalar ($S$), spinor (${\psi }^{1,2}$), and vector ($V_{\mu }$)—together form the multicomponent dark matter (DM), while the fifth (scalar) field ($\varphi$) carries a unit charge under a dark $U_D(1)$ gauge symmetry, enabling SM-DM interactions via the Higgs portal. Although the model maintains classical scale invariance, loop effects break electroweak symmetry. The parameter space is constrained by scale invariance, DM relic density, and direct detection results. Our study aims to identify feasible model regions and evaluate detectability in future experiments. We analyze processes like DM annihilations, semiannihilations, and conversions, integrating them into Boltzmann equations to calculate DM abundances. Random parameter scans reveal regions compatible with current data, including constraints from direct detection experiments like XENONnT and PandaX-4T. Our results show the model’s viability across a broad range of DM masses.

We present a quantum algorithm to compute the logarithm of the determinant of the fermion matrix, assuming access to a classical lattice gauge field configuration. The algorithm uses the quantum eigenvalue transform, and quantum mean estimation, giving a query complexity that scales like $O(V\log (V))$ in the matrix dimension $V$.

We consider evolution of observables which depend on a small but fixed value of longitudinal momentum fraction $x$, to high rapidity, such that $\eta >\ln 1/x$. We show that this evolution is not given by the Jalilian-Marian–Iancu–McLerran–Weigert–Leonidov–Kovner (JIMWLK) (or Balitsky-Kovchegov) equation. We derive the evolution Hamiltonian—$H_{\mathrm{CSS}-\mathrm{JIMWLK}}$ which generates this evolution in the cases of dilute and dense projectile wave function. The two limits yield identical results for $H_{\mathrm{CSS}-\mathrm{JIMWLK}}$. We show that the resulting evolution for the gluon Transverse-Momentum-Dependent is identical to the (double logarithmic) perturbative Collins-Soper-Sterman evolution equation in the longitudinal resolution parameter at a fixed and very large transverse resolution.

In this work, we investigate the production of charmonium $2P$ states via the $e^{+}{e}^{-}\to \gamma D\overline{D}$ process at $\sqrt{s}=4.23\mathrm{GeV}$. Using the measured cross section data for $e^{+}{e}^{-}\to \gamma X(3872)$ as a reference, we calculate the cross sections for $e^{+}{e}^{-}\to \gamma {\chi }_{c0}(2P)$ and $e^{+}{e}^{-}\to \gamma {\chi }_{c2}(2P)$. Since the ${\chi }_{c0}(2P)$ and ${\chi }_{c2}(2P)$ states predominantly decay into $D\overline{D}$ final states, we also predict the corresponding $D\overline{D}$ invariant mass spectrum for the $e^{+}{e}^{-}\to \gamma D\overline{D}$ process. Our results indicate that $e^{+}{e}^{-}\to \gamma D\overline{D}$ is an ideal process for identifying the ${\chi }_{c0}(2P)$ and ${\chi }_{c2}(2P)$ states, analogous to the $\gamma \gamma \to D\overline{D}$ and $B^{+}\to D^{+}{D}^{-}{K}^{+}$ processes. This study highlights the discovery potential of charmonium $2P$ states at BESIII and Belle II.