Static spherically symmetric spacetimes with a vanishing second Ricci invariant constitute an important class of solutions to Einstein’s equations and more generally as archetypes of regular black holes. When studying completeness, one is most often presented with the Kruskal-Szekeres procedure. However, this procedure only works if the spacetime admits a single nondegenerate Killing horizon (a single bifurcation 2-sphere). Here, we generalize the Israel procedure to examine a constructive approach to completeness based entirely on the static spherically symmetric nature of spacetimes with a vanishing second Ricci invariant. It is shown by “block gluing” that the Israel procedure can cover two bifurcation 2-spheres but can fail with three. No coordinate transformations are used in this work.

Compact binaries can have non-negligible orbital eccentricities in the frequency band of ground-based gravitational-wave detectors, depending on their astrophysical formation channels. To accurately determine the parameters of such systems, waveform models need to incorporate eccentricity effects. In this paper, we consider an eccentric binary of spinning nonprecessing compact objects and derive the energy and angular momentum fluxes at infinity, as well as the gravitational waveform modes to the third post-Newtonian order. The novel results of this paper include the next-to-leading order instantaneous spin-orbit and spin-spin contributions to the waveform modes, in addition to the hereditary (tail and memory) contributions to the modes and fluxes for eccentric orbits. The instantaneous contributions are derived for generic motion, while the hereditary contributions are computed in a small-eccentricity expansion, but we consider a resummation that makes them valid for large eccentricities. We employ a quasi-Keplerian parametrization of the motion using harmonic coordinates and the covariant spin-supplementary condition, which complements some results in the literature in other coordinates. Our results can be useful in improving the accuracy of waveform models for spinning binaries on eccentric orbits.

The non-Gaussian part of the covariance matrix of the galaxy power spectrum involves the connected four-point correlation in Fourier space, i.e., trispectrum. This paper introduces a fast method to compute the non-Gaussian part of the covariance matrix of the galaxy power spectrum multipoles in redshift space at tree-level standard perturbation theory. For the tree-level galaxy trispectrum, the angular integral between two wave vectors can be evaluated analytically by employing an FFTLog. The new implementation computes the non-Gaussian covariance of the power spectrum monopole, quadrupole, hexadecapole and their cross-covariance in $\mathcal{O}(10)\mathrm{seconds}$, for an effectively arbitrary number of instances of cosmological and galaxy bias parameters and redshift, without any parallelization or acceleration. It is a large advantage over conventional numerical integration. We demonstrate that the computation of the covariance at $k=0.005–0.4h{\mathrm{Mpc}}^{-1}$ gives results with 0.1–1% accuracy. The efficient computation of the analytic covariance can be useful for future galaxy surveys, especially utilizing multitracer analysis.

We analyze cosmic superstring models in light of NANOGrav 15-year pulsar timing data. A good fit is found for a string tension $G\mu \sim {10}^{-12}–{10}^{-11}$ and a string intercommutation probability $p\sim {10}^{-3}–{10}^{-1}$. Extrapolation to higher frequencies assuming standard big bang cosmology is compatible at the 68% CL with the current LIGO/Virgo/KAGRA upper limit on a stochastic gravitational wave background in the 10 to 100 Hz range. The superstring interpretation of the NANOGrav data would be robustly testable by future experiments even in modified cosmological scenarios.

Detecting the end of the cosmic-ray (CR) electron spectrum would provide important new insights. While we know that Milky Way sources can accelerate electrons up to at least $\sim 1\mathrm{PeV}$, the observed CR electron spectrum at Earth extends only up to 5 TeV (possibly 20 TeV), a large discrepancy. The question of the end of the CR electron spectrum has received relatively little attention, despite its importance. We take a comprehensive approach, showing that there are multiple steps at which the observed CR electron spectrum could be cut off. At the highest energies, the accelerators may not have sufficient luminosity, or the sources may not allow sufficient escape, or propagation to Earth may not be sufficiently effective, or present detectors may not have sufficient sensitivity. For each step, we calculate a rough range of possibilities. Although all of the inputs are uncertain, a clear vista of exciting opportunities emerges. We outline strategies for progress based on CR electron observations and auxiliary multimessenger observations. In addition to advancing our understanding of CRs in the Milky Way, progress will also sharpen sensitivity to dark matter annihilation or decay.

Binary neutron star merger (BNSM) offers an environment where fast neutrino-flavor conversion (FFC) can vividly occur, which potentially leads to a considerable change of the neutrino radiation field. In this paper, we investigate global features of FFC by general relativistic quantum kinetic neutrino transport simulations in spatial axisymmetry. Our result suggests that global advection of neutrinos plays a crucial role in FFC dynamics. Although flavor conversions occur ubiquitously in the early phase, they remain active only in a narrow region in the late phase. This region includes an ELN-XLN zero surface (EXZS), corresponding to a surface where electron-neutrinos lepton number (ELN) equals the heavy-leptonic one (XLN). The EXZS is not stationary but dynamically evolves in a timescale of global advection. We also find that neutrinos can undergo a flavor swap when they pass through the EXZS, resulting in qualitatively different neutrino radiation fields between both sides of EXZS. Our result suggests that EXZS is one of the key ingredients to characterize FFC in BNSM.

In this work, we investigate the electromagnetic energy released by astrophysical black holes within the Kerr-Taub-NUT solution, which describes rotating black holes with a nonvanishing gravitomagnetic charge. In our study, we consider the black holes in the x-ray binary systems GRS $1915+105$, GRO J1655-40, XTE J1550-564, A0620-00, H1743-322, and GRS 1124-683. We show that the Kerr-Taub-NUT spacetime can explain the radiative efficiency of these sources inferred from the continuum fitting method. We also show that, in the framework of the Blandford-Znajek mechanism, it is possible to reproduce the observed jet power. We unify the results of the two analyses for the selected objects to get more stringent constraints on the spacetime parameters. We show that, as in the case of the Kerr spacetime, the Kerr-Taub-NUT solution cannot simultaneously explain the observed jet power and radiative efficiency of GRS $1915+105$.

We investigate the differential emission rate of neutral scalar bosons from a highly magnetized relativistic plasma. We show that three processes contribute at the leading order: particle splitting ($\psi \to \psi +\varphi$), antiparticle splitting ($\overline{\psi }\to \overline{\psi }+\varphi$), and particle-antiparticle annihilation ($\psi +\overline{\psi }\to \varphi$). This is in contrast to the scenario with zero magnetic field, where only the annihilation processes contribute to boson production. We examine the impact of Landau-level quantization on the energy dependence of the rate and investigate the angular distribution of emitted scalar bosons. The differential rate resulting from both (anti)particle splitting and annihilation processes are typically suppressed in the direction of the magnetic field and enhanced in perpendicular directions. Overall, the background magnetic field significantly amplifies the total emission rate. We speculate that our model calculations provide valuable theoretical insights with potentially important applications.

We present the complete results up to twist-3 for hadron production in the target fragmentation region of semi-inclusive deep inelastic scattering with a polarized lepton beam and polarized nucleon target. The nonperturbative effects are factorized into fracture functions. The calculation up to twist-3 is nontrivial since one has to keep gauge invariance. By applying collinear expansion, we show that the hadronic tensor can be expressed by gauge-invariant fracture functions. We also present the results for the structure functions and azimuthal asymmetries.

With the aim of exploring the evidence for or against phase transitions in cold and dense baryonic matter, the inference of the sound speed and equation of state for dense matter in neutron stars is extended in view of recent new observational data. The impact of the heavy ($2.35M_{\odot }$) black-widow pulsar PSR J0952-0607 and the unusually light supernova remnant HESS J1731-347 is inspected. In addition, a detailed reanalysis is performed of the low-density constraint based on chiral effective field theory and of the perturbative QCD constraint at asymptotically high densities, in order to clarify the influence of these constraints on the inference procedure. The trace anomaly measure, $\mathrm{\Delta }=1/3-P/ϵ$, is also computed and discussed. A systematic Bayes factor assessment quantifies the evidence (or nonevidence) of low averaged sound speeds $(c_s^2\le 0.1)$, a prerequisite for a phase transition, within the range of densities realized in the core of neutron stars. One of the consequences of including PSR J0952-0607 in the database is a further stiffening of the equation of state, resulting for a 2.1 solar-mass neutron star in a reduced central density of less than 5 times the equilibrium density of normal nuclear matter at the 68% level. The evidence against small sound speeds in neutron star cores is further strengthened. Within the inferred 68% posterior credible bands, only a weak first-order phase transition with a coexistence density interval $\mathrm{\Delta }n/n\lesssim 0.2$ would be compatible with the observed data.

The experimental data on the electromagnetic (em) form factor of charged pions available at spacelike momenta are analyzed using the dispersive matrix (DM) approach [M. Di Carlo , Unitarity bounds for semileptonic decays in lattice QCD, Phys. Rev. D 104, 054502 (2021)] which describes the momentum dependence of hadronic form factors without introducing any explicit parametrization and includes properly the constraints coming from unitarity and analyticity. The unitary bound is evaluated nonperturbatively making use of the results of lattice QCD simulations of suitable two-point correlation functions contributing to the hadronic vacuum polarization term of the muon. Thanks to the DM method we determine the pion charge radius from existing spacelike data in a completely model-independent way and consistently with the unitary bound, obtaining $⟨r_{\pi }{⟩}_{\mathrm{DM}}=0.703\pm 0.027\mathrm{fm}$. This finding differs by $\simeq 1.6$ standard deviations from the latest PDG [R. L. Workman et al., Review of particle physics, Prog. Theor. Exp. Phys. 2022, 083C01 (2022).] value $⟨r_{\pi }{⟩}_{\mathrm{PDG}}=0.659\pm 0.004\mathrm{fm}$, which is dominated by the very precise results of dispersive analyses of timelike data coming from measurements of the cross section of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ process. We have analyzed the spacelike data using also traditional $z$-expansions, like the Boyd-Grinstein-Lebed (BGL) or Bourrely-Caprini-Lellouch (BCL) fitting functions and adopting a simple procedure that incorporates ab initio the nonperturbative unitary bound in the fitting process. We get $⟨r_{\pi }{⟩}_{\mathrm{BGL}}=0.711\pm 0.039\mathrm{fm}$ and $⟨r_{\pi }{⟩}_{\mathrm{BCL}}=0.709\pm 0.028\mathrm{fm}$ in nice agreement with the DM result. A detailed comparison in a wide range of spacelike momenta between the results of the BGL/BCL fitting procedures and those of the DM method indicates that unitarity must be imposed not only on the fitting function but also on the input data. We have addressed also the issue of the onset of perturbative QCD (pQCD) by performing a sensitivity study of the pion form factor at large spacelike momenta, based only on experimental spacelike data and unitarity. Hence, although the leading pQCD behavior is found to set in only at very large momenta, our DM bands may provide information about the preasymptotic effects related to the scale dependence of the pion distribution amplitude.

The quarkonic contributions to the three-loop heavy-quark form factors for vector, axial-vector, scalar, and pseudoscalar currents are described by closed form difference equations for the expansion coefficients in the limit of small virtualities $q^2/m^2$. A part of the contributions can be solved analytically and expressed in terms of harmonic and cyclotomic harmonic polylogarithms and square-root valued iterated integrals. Other contributions obey equations which are not first-order factorizable. For them still infinite series expansions around the singularities of the form factors can be obtained by matching the expansions at intermediate points and using differential equations which are obeyed directly by the form factors and are derived by guessing algorithms. One may determine all expansion coefficients for $q^2/m^2\to \infty$ analytically in terms of multiple zeta values. By expanding around the threshold and pseudothreshold, the corresponding constants are multiple zeta values supplemented by a finite amount of new constants, which can be computed at high precision. For a part of these coefficients, the infinite series in front of these constants may be even resummed into harmonic polylogarithms. In this way, one obtains a deeper analytic description of the massive form factors, beyond their pure numerical evaluation. The calculations of these analytic results are based on sophisticated computer algebra techniques. We also compare our results with numerical results in the literature.

We consider $d=2$, $\mathcal{N}=(0,2)$ SCFTs that can arise from M5-branes wrapping four-dimensional, complex, toric manifolds and orbifolds. We use equivariant localization to compute the off-shell central charge of the dual supergravity solutions, obtaining a result that can be written as a sum of gravitational blocks and precisely agrees with a field theory computation using anomaly polynomials and $c$-extremization.

We study the freeze-in scenario of leptogenesis via oscillations within the type-I seesaw model with two quasidegenerate heavy Majorana neutrinos $N_{1,2}$ having masses $M_2>M_1\sim (0.1–100)\mathrm{GeV}$, $(M_2-M_1)/M_1\ll 1$, focusing on the role of the $CP$-violation provided by the Dirac phase $\delta$ of the Pontecorvo-Maki-Nakagawa-Sakata lepton mixing matrix. We find that viable leptogenesis can be due solely to $CP$-violating values of $\delta$ and that the $N_{1,2}$ total mixing squared ${\mathrm{\Theta }}^2={\sum }_{\alpha }{\mathrm{\Theta }}_{\alpha }^2$ needed is within the reach of future experiments, ${\mathrm{\Theta }}_{\alpha }$ parametrizing the coupling to the charged lepton $\alpha =e$, $\mu$, $\tau$. Furthermore, the required parameter space differs from that associated with additional Casas-Ibarra sources of $CP$-violation. Future determination of $\delta$, ${\mathrm{\Theta }}^2$ and/or the ratios ${\mathrm{\Theta }}_{\tau }^2:{\mathrm{\Theta }}_{\mu }^2:{\mathrm{\Theta }}_e^2$ would provide a critical test of the considered scenario.

In the curvaton scenario, the curvature perturbation is generated after inflation at the curvaton decay, which may have a prominent non-Gaussian effect. For a model with a nontrivial kinetic term, an enhanced curvature perturbation on a small scale can be realized, which can lead to copious production of primordial black holes (PBHs) and induce secondary gravitational waves (GWs). Using the probability distribution function (PDF) which takes full nonlinear effects into account, we calculate the PBH formation. We find that under the assumption that thus formed PBHs would not overclose the Universe, the non-Gaussianity of the curvature perturbation can be well-approximated by the local quadratic form, which can be used to calculate the induced GWs. In this model the limit of large non-Gaussianity can be reached when the curvaton energy fraction $r$ is small at the moment of curvaton decay. We also show that in the $r\to 1$ limit the PDF is similar to that of ultraslow-roll inflation.

We introduce unsupervised machine learning techniques in order to identify toric phases of $4d$ $\mathcal{N}=1$ supersymmetric gauge theories corresponding to the same toric Calabi-Yau 3-fold. These $4d$ $\mathcal{N}=1$ supersymmetric gauge theories are world volume theories of a D3-brane probing a toric Calabi-Yau 3-fold and are realized in terms of a type IIB brane configuration known as a brane tiling. It corresponds to the skeleton graph of the coamoeba projection of the mirror curve associated to the toric Calabi-Yau 3-fold. When we vary the complex structure moduli of the mirror Calabi-Yau 3-fold, the coamoeba and the corresponding brane tilings change their shape, giving rise to different toric phases related by Seiberg duality. We illustrate that by employing techniques such as principal component analysis and $t$-distributed stochastic neighbor embedding, we can project the space of coamoeba labeled by complex structure moduli down to a lower-dimensional phase space with phase boundaries corresponding to Seiberg duality. In this work, we illustrate this technique by obtaining a 2-dimensional phase diagram for brane tilings corresponding to the cone over the zeroth Hirzebruch surface $F_0$.

We compare the holographic dressed soft wall and the exponentially deformed AdS models for spin $1/2$ fermions. We present the dressed soft wall model and its analytical solutions for the left and right modes, and the corresponding spectra, also including modifications considering hyperfine spin-spin and meson cloud interactions, as well as anomalous dimensions. Then, we discuss the deformed AdS model for spin $1/2$ fermions and present their effective Schrödinger equations for the left and right modes, for which only numerical solutions are available. Then, we consider a polynomial expansion of the effective potential of the deformed AdS model and show that in the quadratic approximation it leads to exact analytical solutions comparable with the dressed soft wall model and obtain the corresponding spectra for left and right modes. We show a numerical comparison of the mass spectra of spin $1/2$ baryons for the dressed soft wall and the deformed AdS models. We present a detailed relation between the quadratic approximation of the deformed AdS and the dressed soft wall models for their spectra, wave functions, and comments on the deep inelastic scattering on both models. We find that these two models are not equivalent even in the quadratic approximation, but it is possible to relate their left and right modes for particular choices of their parameters.

Consistent reductions of higher-dimensional (matter-coupled) gravity theories on spheres have been constructed and classified in an important paper by Cvetič, Lü, and Pope. We close a gap in the classification and study the case when the resulting lower-dimensional theory is two dimensional. We construct the consistent reduction of Einstein-Maxwell-dilaton gravity on a $d$-sphere $S^d$ to two-dimensional dilaton-gravity coupled to a gauged sigma model with target space $\mathrm{SL}(d+1)/\mathrm{SO}(d+1)$. The truncation contains solutions of type ${\mathrm{AdS}}_2\times {\mathrm{\Sigma }}_d$ where the internal space ${\mathrm{\Sigma }}_d$ is a deformed sphere. In particular, the construction includes the consistent truncation around the near-horizon geometry of the boosted Kerr string. In turn, we find that an ${\mathrm{AdS}}_2\times S^d$ background with the round $S^d$ within a consistent truncation requires $d>3$ and an additional cosmological term in the higher-dimensional theory.

We discuss various differences in the instanton-based calculations of the $\beta$ functions in theories such as Yang-Mills and $\mathbb{CP}(N-1)$ on one hand, and $\lambda {\varphi }^4$ theory with Symanzik’s sign-reversed prescription for the coupling constant $\lambda$ on the other hand. Although the aforementioned theories are asymptotically free, in the first two theories, instantons are topological, whereas the Fubini-Lipatov instanton in the third theory is topologically trivial. The spectral structure in the background of the Fubini-Lipatov instanton can be continuously deformed into that in the flat background, establishing a one-to-one correspondence between the two spectra. However, when considering topologically nontrivial backgrounds for Yang-Mills and $\mathbb{CP}(N-1)$ theories, the spectrum undergoes restructuring. In these cases, a mismatch between the spectra around the instanton and the trivial vacuum occurs.

The asymptotic behavior of expanding, generic, $T^2$-symmetric, vacuum spacetimes is examined via numerical simulations. After validation of the numerical methods, the properties of these generic spacetimes are explored and compared to nongeneric subfamilies where proven results exist. The nongeneric subfamilies within this class, including the Kasner, the Gowdy, the pseudohomogeneous, and the $B=0$ spacetimes, all have known asymptotic behaviors in the expanding direction which have been determined either from the explicit solutions or using analytic methods. For the $B\ne 0$ spacetimes, the generic case within the $T^2$-symmetric vacuum solutions, the asymptotic behavior has not been determined analytically. In this work, we use numerical simulations to explore the asymptotic behavior of the $B\ne 0$ spacetimes. Our results indicate that, for these generic spacetimes, the asymptotic behavior in the expanding direction differs from that seen in the nongeneric subfamilies. In addition to differences in asymptotic power laws, an apparent quasi-periodic exchange of energy from one gravitational mode to the other for the generic nonpolarized solutions is observed.