Neutron-rich outflows in neutron-star mergers (NSMs) or other explosive events can be subject to substantial heating through the release of rest-mass energy in the course of the rapid neutron-capture ($r$-) process. This $r$-process heating can potentially have a significant impact on the dynamics determining the velocity distribution of the ejecta, but due to the complexity of detailed nuclear networks required to describe the $r$-process self-consistently, hydrodynamic models of NSMs often neglect $r$-process heating or include it using crude parametrizations. In this work, we present a conceptually new method, RHINE, for emulating the $r$-process and concomitant energy release in hydrodynamic simulations via machine learning algorithms. The method requires the evolution of only a few additional quantities characterizing the composition, of which the nuclear rates of change are obtained at each location and time step from neural networks trained by a large set of trajectories from full nuclear network calculations. The scheme is tested by comparing spherically symmetric wind simulations and long-term simulations of NSMs using RHINE with postprocessing results from nucleosynthesis calculations, showing agreement in the released heating energy to within $\lesssim 10\%$. In our NSM models on average about 2.3 MeV, 0.7 MeV, and 2.1 MeV are released per baryon in dynamical ejecta, NS-torus ejecta, and black hole (BH) torus ejecta, respectively. The strongest velocity boost is observed for BH-torus ejecta, which also become 40% more massive with $r$-process heating. The nucleosynthesis yields are only mildly affected by $r$-process heating, but the kilonova gets significantly brighter once the BH-torus ejecta become visible. RHINE can be readily implemented in existing hydrodynamics codes using pretrained machine learning data and routines for source-term prediction that we provide online.

Collapsars—massive stars whose cores promptly collapse into black holes (BHs)—can power long-duration $\gamma$-ray bursts (LGRBs) via relativistic, collimated, electromagnetically driven outflows, or jets. Their power depends on the BH magnetic field strength and spin. To survive the infalling stellar material, jets need the central BH to attain dynamically important magnetic fields that can suppress the mass inflow and lead to a magnetically arrested disk (MAD). Previous work found that nonradiative MADs can spin down their BHs to an equilibrium spin, $a_{\mathrm{eq}}^{\mathrm{nr}}=0.035–0.07$. Such low spins result in extremely low power jets that may struggle to escape out of the star. However, the dense and hot collapsar disks emit neutrinos that cool the disk, reduce its thickness, and increase the angular momentum supply to the BH. Using 3D two-moment neutrino-transport general relativistic magnetohydrodynamic simulations, we show for the first time that successful collapsar jets powered by neutrino-cooled disks still rapidly spin down their BHs, although to a higher $a_{\mathrm{eq}}\approx 0.13$. This value is consistent with Laser Interferometer Gravitational Wave Observatory/Virgo/Kamioka Gravitational Wave Detector inferred spins, is 2–4 times higher than for nonradiative MADs, and results in 4–16 times more powerful LGRB jets, which are more capable of drilling out of the progenitor star. This value of $a_{\mathrm{eq}}$ holds across a wide range of progenitor structures and mass accretion rates, $\dot{m}\sim (0.1–10)M_{\odot }/\mathrm{s}$. We find that for typical LGRB durations, $t\gtrsim 30\mathrm{s}$, such BHs consume sufficient mass to reach $a_{\mathrm{eq}}\approx 0.13$ by LGRB’s end. However, shorter or lower-$\dot{m}$ LGRBs can leave behind more rapidly spinning BHs.

The large underdense regions in the cosmological matter density field, known as cosmic voids, are powerful probes of cosmology but their potential is currently underexploited. Observationally, voids are identified within the large-scale distribution of galaxies and are, therefore, sensitive to certain features of the galaxy-halo connection. This sensitivity makes the combination of void and galaxy summary statistics particularly powerful probes of both cosmology and the galaxy-halo connection through self-calibration of the void-galaxy relation. In particular the combination of void and galaxy summary statistics breaks degeneracies in the galaxy-halo connection and cosmology relative to the case of galaxy clustering alone. To demonstrate this we forecast cosmological constraints attainable from the combination of the void size function $n_v$, projected void-galaxy cross-correlation function $w_{p,vg}$, and projected galaxy autocorrelation function $w_{p,gg}$ measured in Dark Energy Spectroscopic Instrument (DESI) Year 5 data. We use a grid of cosmological N-body simulations to model this data vector as a function of ${\sigma }_8$ and ${\mathrm{\Omega }}_m$, and a flexible halo occupation distribution model that includes central and satellite galaxy assembly bias. For our fiducial scenario combining $n_v$, $w_{p,vg}$, and $w_{p,gg}$ we forecast 1.5% and 0.8% constraints on ${\mathrm{\Omega }}_m$ and ${\sigma }_8$ from DESI-Y5 data. We also forecast constraints from the combination of the void size function and stacked weak lensing signal of voids.

A key question about the QCD phase diagram is whether there is a critical point somewhere on the boundary between the hadronic and quark-gluon plasma phases, and if so where. Heavy-ion collisions offer a unique opportunity to search for signatures of such a critical point by analyzing event-by-event fluctuations in particle multiplicities. To draw meaningful conclusions from experimental data, a theoretical framework is needed to link QCD thermodynamics with the particle spectra and correlations observed in detectors. The equation of state (EoS) of QCD near a critical point can be related to the universal Gibbs free energy of the 3D Ising model using four currently unknown nonuniversal mapping parameters whose values are determined by the microscopic details of QCD. We utilize the maximum entropy approach to freeze-out the fluctuations in order to make estimates for factorial cumulants of proton multiplicities, assuming thermal equilibrium, for a family of EoS with a 3D Ising-like critical point, varying the microscopic inputs that determine the strength and structure of the critical features. We quantify the effect of the nonuniversal mapping parameters, and the distance between the critical point and the freeze-out curve, on the factorial cumulants of proton multiplicities.

We study the ability of tidal signatures within the inspiral of compact binaries observed through gravitational waves (GWs) to distinguish between neutron stars (NSs) and black holes (BHs). After quantifying how hard this measurement is on a single-event basis, we investigate the ability of a large catalog of GW detections to constrain the fraction of NS in the population as a function of mass: $f_{\mathrm{NS}}(m)$. Using simulated catalogs with realistic measurement uncertainty, we find that $>O(200)$ events will be needed before we can precisely measure $f_{\mathrm{NS}}$, and catalogs of $>O(100)$ events will be needed before we can even rule out the possibility that all low-mass objects are BHs with GW data alone (i.e., without electromagnetic counterparts). Therefore, this is unlikely to occur with advanced detectors, even at design sensitivity. Nevertheless, it could be feasible with next-generation facilities like Cosmic Explorer and Einstein Telescope.

The IceCube South Pole Neutrino Observatory has discovered the presence of a diffuse astrophysical neutrino flux at energies of TeV and beyond using neutrino induced muon tracks and cascade events from neutrino interactions. We present two analyses sensitive to neutrino events in the energy range 1 TeV to 10 PeV, using more than 10 years of IceCube data. Both analyses consistently reject a neutrino spectrum following a single power-law with a significance of $>4\sigma$ in favor of a broken power law. We describe the methods implemented in the two analyses, the spectral constraints obtained, and the validation of the robustness of the results. Additionally, we report the detection of a muon neutrino in the medium energy starting events sample, or MESE, with an energy of ${11.4}_{-2.53}^{+2.46}\mathrm{PeV}$, the highest energy neutrino observed by IceCube to date. The results presented here show insights into the spectral shape of astrophysical neutrinos, which has important implications for inferring their production processes in a multimessenger picture.

We achieve for the first time NNLO $\mathrm{QCD}+\mathrm{NLO}$ EW accuracy for doubly polarized $WZ$ inclusive production at the LHC, in the case of fully leptonic decays. Additionally, we provide estimates for missing higher-order uncertainties in QCD associated with doubly polarized differential cross sections and joint polarization fractions, obtained both with standard scale variations and with a theory-nuisance-parameter approach. The study is carried out in the fiducial setup of a recent ATLAS analysis of Run-2 data.

NICER has enabled mass-radius inferences for pulsars using pulse profile modeling (PPM), providing constraints on the equation of state (EOS) of cold, dense matter. To date, PPM and EOS inference have been carried out as two separate steps, with the former using EOS-agnostic priors. This approach has several drawbacks. Ideally, one would perform a fully hierarchical Bayesian inference where the pulse profile and EOS model parameters are jointly fit, but implementing such a framework is complex and computationally demanding. Here, we present an intermediate solution introducing an EOS-informed prior on mass radius into the existing PPM pipeline using normalizing flows. By focusing on the parameter space consistent with certain EOSs, this approach both tightens constraints on neutron star parameters while reducing computational costs and requiring minimal additional implementation effort. We test this approach on two pulsars, PSR $\mathrm{J}0740+6620$ and PSR J0437-4715, and with two EOS model families: a model based on the speed of sound inside the neutron star interior (CS) and a piecewise-polytropic (PP) model. Both EOS models implement constraints from chiral effective field theory calculations of dense matter. For both pulsar datasets, the inferred radius credible intervals are narrower than in the EOS-agnostic case, with CS favoring smaller radii and PP favoring larger radii. For PSR J0437-4715, the EOS-informed priors reveal a new, more extreme geometric mode that is statistically favored but physically questionable. Including the PPM posteriors in the subsequent EOS inference further tightens the mass-radius posteriors through the chiral effective field theory constraints. However, there is also a sensitivity to the high-density extensions, where the PP (CS) model produces a shift toward larger (smaller) radii and corresponding stiffening (softening) of the pressure-energy density relation.

We introduce a new, nonparametric method for estimating the mass enclosed within a sphere of arbitrary radius centered on the Sun. The method is based on the divergence theorem as applied to measurements of the line-of-sight accelerations of millisecond pulsars. We describe a procedure for inferring the mean mass density within a sphere of a given radius centered on the Sun and find results that are consistent with previous analyses. When combined with a model for the distribution of baryons, this provides the mean mass density of dark matter as a function of distance from the Sun, rather than a single value as is typically reported by kinematic studies. However, with the present pulsar data, the method cannot unambiguously measure a signal from the local distribution of dark matter at this time; such a measurement is expected to soon become possible as the amount of pulsar acceleration data grows and its precision improves. We derive an extension of the well-known shell theorem to a spherical-harmonics expansion of the density and potential and use the result to obtain estimates for density asymmetries with respect to the Galactic midplane from the observed acceleration data. The predicted asymmetries do not follow the observed distribution of Milky Way disk stars or gas; this can potentially be explained by a nonuniform distribution of dark matter in the solar neighborhood.

We present a search for polarization oscillation of the Crab Nebula, also known as Tau A, at millimeter wavelengths using observations with the Simons Array, the successor experiment to POLARBEAR. We follow up on previous work by POLARBEAR using 90 GHz band data of the 2023 observing season of the Simons Array to evaluate the variability of Tau A’s polarization angle. Tau A is widely used as a polarization angle calibration source in millimeter-wave astronomy, and thus it is necessary to validate the stability. Additionally, an interesting application of the time-resolved polarimetry of Tau A is to search for axionlike particles (ALPs). We do not detect a global signal across the frequencies considered in this analysis and place a median 95% upper bound of polarization oscillation amplitude $A<0.12°$ over oscillation frequencies from $3.39{\mathrm{yr}}^{-1}$ to $1.50{\mathrm{day}}^{-1}$. This constrains the ALP-photon coupling at a median 95% upper bound of $g_{a\gamma \gamma }<3.84\times {10}^{-12}\times (m_a/{10}^{-21}\mathrm{eV})$ in the mass range from $4.4\times {10}^{-22}$ to $7.2\times {10}^{-20}\mathrm{eV}$, assuming the ALP constitutes all of dark matter, its field is a stochastic Gaussian field, and it is the sole source of Tau A’s polarization angle oscillation. Additionally, we do not detect signal at the frequencies where $2.5\sigma$ hints were previously reported by POLARBEAR, but we do not exclude these signals at the 95% confidence level.

The scalar spectral index $n_s$ is a powerful test of inflationary models. The tightest constraint on $n_s$ to date derives from the combination of cosmic microwave background (CMB) data with baryon acoustic oscillation (BAO) data. The resulting $n_s$ constraint is shifted significantly upward relative to the constraint from CMB alone, with the consequence that previously preferred inflationary models are seemingly disfavored by $\gtrsim 2\sigma$. Here we show that this shift in $n_s$ is the combined effect of a degeneracy between $n_s$ and BAO parameters exhibited by CMB data and the tension between CMB datasets and the Dark Energy Spectroscopic Instrument BAO data under the assumption of the standard cosmological model. Given the crucial role of $n_s$ in discriminating between inflationary models, we urge caution in interpreting $\mathrm{CMB}+\mathrm{BAO}$ constraints on $n_s$ until the BAO-CMB tension is resolved.

The high electron temperature in galaxy clusters ($>1\mathrm{keV}$ or $>{10}^7\mathrm{K}$) leads to corrections at the level of a few percent in their thermal Sunyaev-Zeldovich effect signatures. Both the size and frequency dependence of these corrections, which are known as relativistic temperature corrections, depend upon the temperature of the objects. In this work we exploit this effect to measure the average temperature of a stack of Compton-$y$ selected clusters. Specifically, we apply the “spectroscopic method” and search for the temperature that best fits the clusters’ signal measured at frequencies from 30 to 545 GHz by the Atacama Cosmology Telescope and Planck satellite. We measure the average temperature of clusters detected in the Atacama Cosmology Telescope maps to be $8.5\pm 2.4\mathrm{keV}$, with an additional systematic error of comparable amplitude dominated by passband uncertainty. Upcoming surveys, such as the Simons Observatory and CMB-S4, have the potential to dramatically improve upon these measurements and thereby enable precision studies of cluster temperatures with millimeter observations. The key challenge for future observations will be mitigating instrumental systematic effects, which already limit this analysis.

We demonstrate a precise relation between the rate of complexity of quantum states excited by local operators in two-dimensional conformal field theories and the radial momentum of particles in three-dimensional anti–de Sitter spacetimes. Similar relations have been anticipated based on qualitative models for operator growth. Here, we make this correspondence sharp with two key ingredients: the precise definition of quantum complexity given by the spread complexity of states, and the match of its growth rate to the bulk momentum measured in the proper radial distance coordinate.

We revisit a double-scaled limit of the superconformal index of $\mathcal{N}=2$ superconformal field theories (SCFTs) which generalizes the Schur index. The resulting partition function, $\widehat{\mathcal{Z}}(q,\alpha )$, has a standard $q$-expansion with coefficients depending on a continuous parameter $\alpha$. The Schur index is a special case with $\alpha =1$. Through explicit computations we argue that this partition function is an invariant of certain mass deformations and vacuum expectation value (vev) deformations of the SCFT. In particular, two SCFTs residing in different corners of the same Coulomb branch, satisfying certain restrictive conditions, have the same partition function with a nontrivial map of the parameters, ${\widehat{\mathcal{Z}}}_1(q,{\alpha }_1)={\widehat{\mathcal{Z}}}_2(q,{\alpha }_2({\alpha }_1))$. For example, we show that the Schur index of all the SCFTs in the Deligne-Cvitanović series is given by special values of $\alpha$ of the partition function of the $\mathrm{SU}(2)N_f=4$ $\mathcal{N}=2$ SQCD.

Baryon acoustic oscillation (BAO) measurements play a key role in ruling out postrecombination solutions to the Hubble tension. However, because the data compression leading to these measurements assumes a fiducial $\mathrm{\Lambda }\mathrm{CDM}$ cosmology, their reliability in testing late-time modifications to $\mathrm{\Lambda }\mathrm{CDM}$ has at times been called into question. We play devil’s advocate and posit that fiducial cosmology assumptions do indeed affect BAO measurements in such a way that low-redshift acoustic angular scales (proportional to the Hubble constant $H_0$) are biased low and test whether such a rescaling can rescue postrecombination solutions. The answer is no. First, strong constraints on the shape of the $z\lesssim 2$ expansion history from unanchored Type Ia Supernovae (SNeIa) prevent large deviations from $\mathrm{\Lambda }\mathrm{CDM}$. In addition, unless ${\mathrm{\Omega }}_m$ is significantly lower than 0.3, the rescaled BAO measurements would be in strong tension with geometrical information from the cosmic microwave background. We demonstrate this explicitly on several dark energy (DE) models ($w\mathrm{CDM}$, CPL DE, phenomenologically emergent DE, holographic DE, ${\mathrm{\Lambda }}_s\mathrm{CDM}$, and the negative cosmological constant model), finding that none can address the Hubble tension once unanchored SNeIa are included. We argue that the ${\mathrm{\Lambda }}_s\mathrm{CDM}$ sign-switching cosmological constant model possesses interesting features which make it the least unpromising one among those tested. Our results demonstrate that possible fiducial cosmology-induced BAO biases cannot be invoked as loopholes to the Hubble tension “no-go theorem”, and highlight the extremely important but so far underappreciated role of unanchored SNeIa in ruling out postrecombination solutions.

We investigate the impact of residual annihilation from sub-GeV mass thermal relic dark matter candidates during big bang nucleosynthesis (BBN). Focusing on candidates with $p$-wave annihilation channels, we show that the hadronic injection of pions and kaons beyond freeze-out, and their subsequent interaction with protons and neutrons prior to the deuterium bottleneck, provides a sensitivity to annihilation that surpasses that of the cosmic microwave background (CMB) and indirect detection in the galaxy.

We compute the classical one-loop gravitational Compton amplitude describing the scattering of a graviton off a massive spinning compact object at the second post-Minkowskian order, including terms through the quartic order in spin. Our analysis includes spin-induced finite-size effects up to the hexadecapolar order and extends recent results obtained for minimal couplings at the quadratic order in spin. From the amplitude, we determine the scattering phase in momentum space, applicable in both the eikonal and wave regimes. In the eikonal limit, we then isolate the spin-independent contribution of the graviton field, explicitly linking it to the dynamics of a massless scalar probe in a Kerr background. This constitutes the first complete description of classical one-loop Compton scattering for generic spinning compact objects at the second post-Minkowskian and hexadecapolar orders.

We construct an exact analytic solution of the revised small-$x$ helicity evolution equations from Borden, Kovchegov, and Li [Helicity evolution at small x: Quark to gluon and gluon to quark transition operators, J. High Energy Phys. 09 (2024) 037], where the contributions of the quark-to-gluon and gluon-to-quark transition operators were newly included. These evolution equations are written in the large-$N_c$ and -$N_f$ limit and are double-logarithmic, resumming powers of ${\alpha }_s{\ln }^2(1/x)$. Here $N_c$ and $N_f$ are the numbers of quark colors and flavors, respectively, while ${\alpha }_s$ is the strong coupling constant and $x$ is the Bjorken-$x$ variable. Using our solution, we obtain analytic, small-$x$, large-$N_c$ and -$N_f$ expressions for the flavor singlet quark and gluon helicity parton distribution functions (PDFs) and for the $g_1$ structure function as double-inverse Laplace transforms. We also extract analytic expressions for the eigenvalues of the matrix of polarized Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) anomalous dimensions and, subsequently, analytic expressions for each of the four individual polarized anomalous dimensions themselves ($\mathrm{\Delta }{\gamma }_{qq},\mathrm{\Delta }{\gamma }_{qG},\mathrm{\Delta }{\gamma }_{Gq}$, and $\mathrm{\Delta }{\gamma }_{GG}$): these expressions resum powers of ${\alpha }_s/{\omega }^2$ to all orders at large $N_c$ and $N_f$ (with $\omega$ the Mellin moment variable). We extract the leading small-$x$ asymptotic power-law growth of the helicity distributions, given by $\mathrm{\Delta }\mathrm{\Sigma }(x,Q^2)\sim \mathrm{\Delta }G(x,Q^2)\sim g_1(x,Q^2)\sim {(\frac{1}{x})}^{{\alpha }_h}$, where the intercept ${\alpha }_h$ satisfies an algebraic equation. Although the algebraic complexity of the equation prevented us from obtaining a general analytic expression for ${\alpha }_h$, we determine ${\alpha }_h$ numerically for various values of $N_c$ and $N_f$ (and, for the special case of $N_f=2N_c$, we determine ${\alpha }_h$ analytically). We further obtain the explicit asymptotic expressions for the helicity distributions, which yield numerical values for the ratio of the gluon helicity PDF to the flavor singlet quark helicity PDF in the small-$x$ asymptotic limit (for different $N_f/N_c$). Just as for the analytic solution to small-$x$ helicity evolution equations in the large-$N_c$ limit constructed in Borden and Kovchegov [Analytic solution for the revised helicity evolution at small x and large ${\mathrm{N}}_c$: New resummed gluon-gluon polarized anomalous dimension and intercept, Phys. Rev. D 108, 014001 (2023)] and for the iterative solution to the large-$N_c$ and -$N_f$ helicity evolution equations constructed in Borden, Kovchegov, and Li [Helicity evolution at small x: Quark to gluon and gluon to quark transition operators, J. High Energy Phys. 09 (2024) 037], we again find that all our predictions for polarized DGLAP anomalous dimensions are fully consistent with the existing finite-order calculations. Similar to the large-$N_c$ case [Borden and Kovchegov, Analytic solution for the revised helicity evolution at small x and large ${\mathrm{N}}_c$: New resummed gluon-gluon polarized anomalous dimension and intercept, Phys. Rev. D 108, 014001 (2023)], our intercept ${\alpha }_h$ (evaluated at various $N_c$ and $N_f$ values) exhibits a very slight disagreement with the predictions made within the infrared evolution equations framework in Bartels et al. [Flavor singlet contribution to the structure function G(1) at small x, Z. Phys. C 72, 627 (1996)], Blümlein and Vogt [The singlet contribution to the structure function $g_1(x,Q^2)$ at small $x$, Phys. Lett. B 386, 350 (1996)], Boussarie et al. [Proton spin structure at small-$x$, Phys. Lett. B 797, 134817 (2019)].

We review lattice results related to pion, kaon, $D$-meson, $B$-meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More specifically, we report on the determination of the light-quark masses, the form factor $f_{+}(0)$ arising in the semileptonic $K\to \pi$ transition at zero momentum transfer, as well as the decay-constant ratio $f_K/f_{\pi }$ and its consequences for the Cabibbo–Kobayashi–Maskawa (CKM) matrix elements $V_{us}$ and $V_{ud}$. We review the determination of the $B_K$ parameter of neutral kaon mixing as well as the additional four $B$ parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for $m_c$ and $m_b$ as well as those for the decay constants, form factors, and mixing parameters of charmed and bottom mesons and baryons. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant ${\alpha }_s$. We review the determinations of nucleon charges from the matrix elements of both isovector and flavor-diagonal axial, scalar and tensor local quark bilinears, and momentum fraction, helicity moment and the transversity moment from one-link quark bilinears. We also review determinations of scale-setting quantities. Finally, in this review we have added a new section on the general definition of the low-energy limit of the Standard Model.

This paper reports world averages of measurements of $b$-hadron, $c$-hadron, and $\tau$-lepton properties obtained by the Heavy Flavor Averaging Group using results available before October 2023. In rare cases, significant results obtained several months later are also used. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, $CP$ violation parameters, parameters of semileptonic decays, and Cabibbo-Kobayashi-Maskawa matrix elements.