A statistically significant detection of the diffuse supernova neutrino background (DSNB) is around the corner. To this purpose, we assess the contribution to the DSNB of magnetorotational collapses of massive stars, relying on a suite of state-of-the-art three-dimensional neutrino-magnetohydrodynamic simulations. We find that neutrinos from magnetorotational core collapses boost the high-energy tail of the DSNB spectrum, similar to what is expected from neutrino-driven black hole-forming collapses. The latest data from the Super-Kamiokande Collaboration can already exclude that more than 13% of all collapsing massive stars undergo magnetorotational collapses under optimistic assumptions. A DSNB detection at $3\sigma$ could take place up to 4 yr earlier at Super-Kamiokande-Gadolinium or JUNO if the fraction of magnetorotational collapses should be larger than 10%. Fascinatingly, if the fraction of magnetorotational stellar collapses should be larger than 19% (13%), Hyper-Kamiokande could measure such a fraction at $3\sigma$ after (10 yr) 20 yr of DSNB data taking. The combination of DSNB and electromagnetic data has the potential to resolve the degenerate contributions from magnetorotational and neutrino-driven black hole-forming collapses, providing crucial insight on the properties of the population of collapsing massive stars.

We obtain the gravitational emission from particles scattering via the Yukawa interaction, presenting both classical and approximate quantum results. We also estimate the contribution from the tensor part of the internucleon interaction. This emission is the main source of a very high frequency component to the stochastic background in the Solar System and in neutron stars. The emission from the Sun (allowing for Debye screening) and from a typical neutron star are obtained. The gravitational wave luminosity of the Sun is $41\pm 10\mathrm{MW}$.

The phase-space approach (PSA), which was originally introduced in Lacroix et al. [Phys. Rev. D 106, 123006 (2022)] to describe neutrino flavor oscillations for interacting neutrinos emitted from stellar objects is extended to describe arbitrary numbers of neutrino beams. The PSA is based on mapping the quantum fluctuations into a statistical treatment by sampling initial conditions followed by independent mean-field evolution. A new method is proposed to perform this sampling that allows treating an arbitrary number of neutrinos in each neutrino beams. We validate the technique successfully and confirm its predictive power on several examples where a reference exact calculation is possible. We show that it can describe many-body effects, such as entanglement and dissipation induced by the interaction between neutrinos. Due to the complexity of the problem, exact solutions can only be calculated for rather limited cases, with a limited number of beams and/or neutrinos in each beam. The PSA approach considerably reduces the numerical cost and provides an efficient technique to accurately simulate arbitrary numbers of beams. Examples of PSA results are given here, including up to 200 beams with time-independent or time-dependent Hamiltonians. We anticipate that this approach will be useful to bridge exact microscopic techniques with more traditional transport theories used in neutrino oscillations. It will also provide important reference calculations for future quantum computer applications where other techniques are not applicable to classical computers.

Searching for gravitational waves from stellar-mass binary black holes with LISA remains a challenging open problem. Conventional template-bank approaches to the search are impossible due to the prohibitive number of templates that would be required. This paper continues the development of a hierarchical semicoherent stochastic search, extending it to a full end-to-end pipeline that is then applied to multiple mock LISA data streams which include simulated noise. Particle swarm optimization is used as a stochastic search algorithm, tracking multiple maxima of a semicoherent search statistic defined over source parameter space. The pipeline is accelerated by the use of graphical processing units (GPUs). No prior information from observations by ground-based detectors is used; this is necessary in order to provide advance warning of the merger. We find that the pipeline is able to detect sources with signal-to-noise ratios as low as $\rho \sim 17$, we demonstrate that these searches can directly seed coarse parameter estimation in cases where the search trigger is loud. An example of how the false-alarm probability can be estimated for this type of GW search is also included.

We investigate contributions of excited states to nucleon matrix elements computed in lattice QCD by employing, in addition to the standard nucleon interpolating operator, pion-nucleon ($\pi \text{−}N$) operators. We solve a generalized eigenvalue problem (GEVP) to obtain an optimal interpolating operator that minimizes overlap with the $\pi \text{−}N$ states. We derive a variant of the standard application of the GEVP method, which allows for constructing 3-point correlation functions using the optimized interpolating operator without requiring the computationally demanding combination that includes $\pi \text{−}N$ operators in both sink and source. We extract nucleon matrix elements using two twisted mass fermion ensembles, one ensemble generated using pion mass of 346 MeV and one ensemble tuned to reproduce the physical value of the pion mass. Especially, we determine the isoscalar and isovector scalar, pseudoscalar, vector, axial, and tensor matrix elements. We include results obtained using a range of kinematic setups, including momentum in the sink. Our results using this variational approach are compared with previous results obtained using the same ensembles and multistate fits without GEVP improvement. We find that for the physical mass point ensemble, the improvement, in terms of suppression of excited states using this method, is most significant for the case of the matrix elements of the isovector axial and pseudoscalar currents.

We calculate the energy spectrum of the S-wave doubly heavy tetraquark systems, including the $Q{Q}^{(\prime )}\overline{q}\overline{q}$, $Q{Q}^{(\prime )}\overline{s}\overline{q}$, and $Q{Q}^{(\prime )}\overline{s}\overline{s}$ ($Q^{(\prime )}=b$, $c$ and $q=u$, $d$) systems within the constituent quark model. We use the complex scaling method to obtain bound states and resonant states simultaneously, and the Gaussian expansion method to solve the complex-scaled four-body Schrödinger equation. With a novel definition of the root-mean-square radii, we are able to distinguish between meson molecules and compact tetraquark states. The compact tetraquarks are further classified into three different types with distinct spatial configurations: compact even tetraquarks, compact diquark-antidiquark tetraquarks, and compact diquark-centered tetraquarks. In the $I(J^P)=0(1^{+})$ $QQ\overline{q}\overline{q}$ system, there exists the $D^{*}D$ molecular bound state with a binding energy of $-14\mathrm{MeV}$, which is the candidate for $T_{cc}(3875{)}^{+}$. The shallow ${\overline{B}}^{*}\overline{B}$ molecular bound state is the bottom analog of $T_{cc}(3875{)}^{+}$. Moreover, we identify two resonant states near the $D^{*}{D}^{*}$ and ${\overline{B}}^{*}{\overline{B}}^{*}$ thresholds. In the $J^P=1^{+}$ $bb\overline{q}\overline{q}(I=0)$ and $bb\overline{s}\overline{q}$ systems, we obtain deeply bound states with a compact diquark-centered tetraquark configuration and a dominant ${\chi }_{{\overline{3}}_c\otimes 3_c}$ component, along with resonant states with similar configurations as their radial excitations. These states are the QCD analog of the helium atom. We also obtain some other bound states and resonant states with “QCD hydrogen molecule” configurations. Moreover, we investigate the heavy quark mass dependence of the $I(J^P)=0(1^{+})$ $QQ\overline{q}\overline{q}$ bound states. We strongly urge the experimental search for the predicted states.

We compute the differential cross section for direct quarkonium production in high-energy electron-nucleus collisions at small $x$. Our computation is performed within the nonrelativistic QCD factorization formalism that separates the calculation into short distance coefficients and long distance matrix elements that depend on the color and spin of the state. We obtain the short distance coefficients of the production of the heavy quark pair within the framework of the color glass condensate effective field theory, which resums coherent multiple interactions of the heavy quark pair with the nucleus to all orders. Our results are expressed as the convolution of perturbatively calculable functions with multipoint lightlike Wilson line correlators. In the correlation limit, we establish the correspondence between our color glass condensate formulation with calculations employing the transverse momentum dependent (TMD) framework. We extend this correspondence by resumming kinematic power corrections within the improved TMD framework, which interpolates between the TMD formalism and $k_{\perp }$-factorization formalism. We present a detailed numerical analysis, focusing on $J/\psi$ production in the kinematics accessible at the future Electron-Ion Collider, highlighting the importance of genuine higher-order saturation contributions when the electron collides with a large nucleus. Our results are also valid in the photoproduction limit where we expect the largest contribution from genuine higher-order saturation contributions which could be accessed in ultraperipheral collisions of relativistic heavy ions.

Single-field models of accelerated expansion with nearly flat potentials, despite being able to provide observationally viable explanations for the early-time cosmic inflation and the late-time cosmic acceleration, are in strong tension with string theory evidence and the associated de Sitter swampland constraints. It has recently been argued that in an open universe, where the spatial curvature is negative (i.e., with ${\mathrm{\Omega }}_k>0$), a new stable fixed point arises, which may lead to viable single-field-based accelerated expansion with an arbitrarily steep potential. Here, we show, through a dynamical systems analysis and a Bayesian statistical inference of cosmological parameters, that the additional cosmological solutions based on the new fixed point do not render steep-potential, single-field, accelerated expansion observationally viable. We mainly focus on quintessence models of dark energy, but we also argue that a similar conclusion can be drawn for cosmic inflation.

We investigate the independent chiral zero modes on the orbifolds from the Atiyah-Segal-Singer fixed point theorem. The required information for this calculation includes the fixed points of the orbifold and the manner in which the spatial symmetries act on these points, unlike previous studies that necessitated the calculation of zero modes. Since the fixed point theorem can be applied to any fermionic theory on any orbifold, it allows us to determine the index even on orbifolds where the calculation of zero modes is challenging or in the presence of nontrivial gauge configurations. We compute the indices on the $T^2/{\mathbb{Z}}_N(N=2,3,4,6)$ and $T^4/{\mathbb{Z}}_N(N=2,3,5)$ as examples. Furthermore, we also attempt to compute the indices on a Coxeter orbifold related to the $D_4$ lattice.

The worldlines (in harmonic coordinates) of two gravitationally interacting massive bodies at the second post-Minkowskian order are described in explicit form. Both the conservative case and the radiation-reacted case are considered. We use our results to check the changes, during scattering, of the individual momenta as well as of the total angular momentum. High post-Newtonian order values of the $O(G^2)$ radiation-reaction acceleration components are provided for checks of future post-Newtonian computations.

We explore the impact of corrections to the propagation on the waveforms of gravitationally lensed gravitational waves under the geometrical optics approximation, focusing on both uniform cosmological modifications and local modifications localized around lensing objects. By adopting a model-independent phenomenological approach, we systematically investigate the effects of these modifications in strong lensing scenarios, where detection of multiple images is expected. Our analysis reveals that cosmological modifications can yield corrections to the time delay that remain minor compared with the effects that accumulate over the whole propagation process, which are present also in the unlensed waveform. By contrast, local modifications around lensing objects can alter the image position and also the magnification factor, which is potentially polarization selective and frequency dependent. In some cases we can have image disappearance as well as signal amplification. Furthermore, we demonstrate that such modifications can cause degradation of waveform match with the templates based on general relativity. This study highlights the importance of considering waveform modifications to search for the signature of modified propagation or the existence of extra polarization modes and proposes potential observational targets.

In this work we investigate the presence of integrable hidden structures in the dynamics of perturbed nonrotating black holes (BHs). This can also be considered as a first step in a wider program of an effective identification of “slow” and “fast” degrees of freedom (DoFs) in the (binary) BH dynamics, following a wave-mean flow perspective. The slow DoFs would be associated with a nonlinear integrable dynamics, on which the fast ones propagate following an effective linear dynamics. BH perturbation theory offers a natural ground to test these properties. Indeed, the decoupling of Einstein equations into wave master equations with a potential provides an instance of such splitting into (frozen) slow DoFs (background potential) over which the linear dynamics of the fast ones (perturbation master functions) evolve. It has been recently shown that these wave equations possess an infinite number of symmetries that correspond to the flow of the infinite hierarchy of Korteweg-de Vries (KdV) equations. Starting from these results, we systematically investigate the presence of integrable structures in BH perturbation theory. We first study them in Cauchy slices and then extend the analysis to hyperboloidal foliations. This second step introduces a splitting of the master equation into bulk and boundary contributions, unveiling an underlying structural relation with the slow and fast DoFs. This insight represents a first step to establish the integrable structures associated to the slow DoFs as bulk symmetries of the dynamics of perturbed BHs.

The evolution equation of two-point correlation function $\xi$ of galaxies can analytically describe the large scale structure of the galaxy distribution, and the solution depends also upon the initial condition. The primeval spectrum of the baryon acoustic oscillations contains multipeaks that survived the Silk damping, and, as a relevant portion, two peaks of the primeval baryon acoustic oscillation spectrum fall into the range of current galaxy surveys. Incorporating this portion, we use a twin-peak initial power spectrum of the galaxies, and obtain the evolution solution from a redshift $z=8$ to $z=0$ in the Gaussian approximation. The outcome $\xi (r)$ at $z=0.6$ still exhibits the 100 Mpc periodic bumps as observed by the WiggleZ survey, a feature largely determined by the Jeans length ${\lambda }_J$ in the equation. In particular, due to the superposition of the twin peaks in the initial condition, $\xi (r)$ shows a shallow trough at $\sim 70h^{-1}\mathrm{Mpc}$ and a deep trough at $\sim 140h^{-1}\mathrm{Mpc}$, agreeing with the observational data, much better than our previous work that used a simple one-peak initial spectrum.

The inflationary and preinflationary evolution of scalar modes of cosmological perturbations in a closed universe is analyzed for a loop quantum cosmology model with an inflationary regime consistent with the constraints on inflation derived from observations of the cosmic microwave background. The effective background dynamics includes a bounce induced by quantum gravity effects. Initial conditions for the perturbations are set before the bounce, and the perturbations are numerically evolved until the end of inflation, allowing the determination of the primordial power spectrum for comoving curvature perturbations. The power spectrum includes corrections due to the presence of spatial curvature and excitations produced before the onset of slow-roll inflation. The deviations from the usual power-law spectrum can be significant for observable modes even for spatial curvatures much smaller than the observational limit obtained without considering the preinflationary evolution of the perturbations.

We define an $S$ matrix for massive scalar fields on a fixed de Sitter spacetime, in the expanding patch coordinates relevant for early Universe cosmology. It enjoys many of the same properties as its Minkowski counterpart, for instance: it is insensitive to total derivatives and field redefinitions in the action; it can be extracted as a particular “on shell” limit of time-ordered correlation functions; and for low-point scattering, kinematics strongly constrains its possible structures. We present explicit formulas relating inflationary observables—namely in-in equal-time correlators and wavefunction coefficients at the conformal boundary—to these $S$ matrix elements. This new formalism will allow modern amplitude methods to be applied directly in cosmology and hence provide a wider range of more accurate theoretical predictions for upcoming sky surveys.

High-frequency primordial gravitational waves (PGWs) with wave numbers larger than the Hubble parameter at the end of inflation are originated from the ultraviolet (UV) modes, which are never stretched out of the horizon. Such a UV tail of the PGW energy spectrum has a spurious logarithmic divergence. We study the origin of such a divergence, and find that it comes from the instantaneous inflation-to-postinflation transition, which can be removed by considering a finite duration. For the first time, we obtain a semianalytical expression for the PGW energy spectrum. We find that the UV tail decays exponentially, while the decay rate depends solely on the transition rate. When there is a stiff postinflationary stage, the enhanced PGW displays a characteristic spectral shape of power-law increasing and exponential decaying. We propose a fitting formula which can be used for signal searching.

The IceCube neutrino telescope has detected a diffuse flux of high-energy astrophysical neutrinos, but the sources of this flux have largely remained elusive. Using the 10-year IceCube public dataset, we search for correlations between neutrino events and tracers of large-scale structure (LSS). We conduct a combined cross-correlation analysis using several wide-area galaxy catalogs spanning a redshift range of $z=0.1$ to $z\sim 2.5$ as well as maps of the cosmic infrared background. We do not detect a definitive signal, but find tantalizing hints of a potential positive correlation between neutrinos and the tracers of LSS. We additionally construct a simple model to interpret galaxy-neutrino cross-correlations in terms of the redshift distribution of neutrino sources. We put upper limits on the clustering amplitude of neutrinos based on the measured cross-correlations with galaxies and forecast the improvements on these constraints that can be obtained using future detectors. We show that, in the future, neutrino-galaxy cross-correlations should be a powerful probe to constrain properties of neutrino source populations.