We study the $B^{-}\to K^{-}\eta {\eta }_c$ decay by taking into account the $S$-wave contributions from the pseudoscalar meson-pseudoscalar meson interactions within the unitary coupled-channel approach, where the $D\overline{D}$ bound state is dynamically generated. In addition, the contribution from the intermediate resonance $K_0^{*}(1430{)}^{-}$, with $K_0^{*}(1430{)}^{-}\to K^{-}\eta$, is also considered. Our results show that there is a clear peak around 3720 MeV in the $\eta {\eta }_c$ invariant mass distribution, which could be associated with the $D\overline{D}$ bound state. The future precise measurements of the $B^{-}\to K^{-}\eta {\eta }_c$ process at the Belle II and LHCb experiments could be, therefore, used to check the existence of the $D\overline{D}$ bound state, and to deepen our understanding of the hadron-hadron interactions.

In various high-energy physics contexts, such as neutrino-oscillation experiments, several assumptions underlying the typical asymptotic confidence interval construction are violated, such that one has to resort to computationally expensive methods like the Feldman-Cousins method for obtaining confidence intervals with proper statistical coverage. By construction, the computation of intervals at high confidence levels requires fitting millions or billions of pseudoexperiments, while wasting most of the computational cost on overly precise intervals at low confidence levels. In this work, a simple importance sampling method is introduced that reuses pseudoexperiments produced for all tested parameter values in a single mixture distribution. This results in a significant error reduction on the estimated critical values, especially at high confidence levels, and simultaneously yields a correct interpolation of these critical values between the parameter values at which the pseudoexperiments were produced. The theoretically calculated performance is demonstrated numerically using a simple example from the analysis of neutrino oscillations. The relationship to similar techniques applied in statistical mechanics and $p$-value computations is discussed.

Multiparametric families of nonsupersymmetric ${\mathrm{EAdS}}_4$ flows as well as asymptotically ${\mathrm{EAdS}}_4$ solitons and wormholes are constructed within the four-dimensional SO(8) gauged supergravity that describes the compactification of M-theory on $S^7$. More concretely, the solutions are found within the so-called STU model that describes the $\mathrm{U}(1{)}^4$ invariant sector of the theory. The on-shell action and gravitational free energy are computed for the regular solutions, the latter being zero for the wormholes irrespective of supersymmetry. There are special loci in parameter space yielding solutions with enhanced (super)symmetry. Examples include a supersymmetric ${\mathrm{EAdS}}_4$ flow with $\mathrm{SO}(4)\times \mathrm{SO}(4)$ symmetry dual to a specific real mass deformation of ABJM on ${\mathrm{S}}^3$ as well as a nonsupersymmetric wormhole with $\mathrm{SU}(3)\times \mathrm{U}(1{)}^2$ symmetry. Uplift formulas for these and other examples to Euclidean solutions of 11-dimensional supergravity are presented and their complex nature discussed.

We develop a diagrammatic approach to effective field theories (EFTs) corresponding to deep neural networks at initialization, which dramatically simplifies computations of finite-width corrections to neuron statistics. The structures of EFT calculations make it transparent that a single condition governs criticality of all connected correlators of neuron preactivations. Understanding of such EFTs may facilitate progress in both deep learning and field theory simulations.

Violation of Lorentz symmetry can result in two distinct effects in the propagation of the gravitational waves (GWs). One is a modified dispersion relation and another is a frequency-dependent damping of GWs. While the former has been extensively studied in the literature, in this paper we concentrate on the frequency-dependent damping effect that arises from several specific Lorentz-violating theories, such as spatial covariant gravities, Hořava-Lifshitz gravities, etc. This Lorentz-violating damping effect changes the damping rate of GWs at different frequencies and leads to an amplitude correction to the GW waveform of compact binary inspiral systems. With this modified waveform, we then use the Fisher information matrix to investigate the prospects of constraining the Lorentz-violating damping effect with GW observations. We consider both ground-based and space-based GW detectors, including the advanced LIGO, Einstein Telescope, Cosmic Explorer (CE), Taiji, TianQin, and LISA. Our results indicate that the ground-based detectors in general give tighter constraints than those from the space-based detectors. Among the considered three ground-based detectors, CE can give the tightest constraints on the Lorentz-violating damping effect, which improves the current constraint from LIGO-Virgo-KAGRA events by about 8 times.

In the Randall-Sundrum (RS) II braneworld scenario, general relativity (GR) is modified by adding an extra dimension such that it is indistinguishable from GR in the weak gravity limit. However, such modifications may leave a mark in the strong field regime. We therefore analyze massive scalar perturbations around rotating black holes in the RS II model. Unlike black holes in GR, these braneworld black holes carry a tidal charge that contains information about the extra spatial dimension, and the rotation parameter for such black holes can exceed unity. Through the method of continued fractions, we investigate the quasinormal mode spectra, and the superradiant instabilities associated with the existence of quasibound states, that is, gravitational atoms. In comparison to the four-dimensional Kerr black hole, we report distinctive signatures of the tidal charge and the rotation parameter, which manifest as signals of the extra dimension, on both the fundamental quasinormal mode and the formation of gravitational atoms. These findings offer insights into testing modifications to GR and detecting ultralight bosonic particles around black holes.

Using the Ernst formalism, a novel solution of vacuum general relativity was recently obtained [Phys. Rev. D 106, 064014 (2022)], describing a Schwarzschild black hole (BH) immersed in a nonasymptotically flat rotating background, dubbed swirling universe, with the peculiar property that north and south hemispheres spin in opposite directions. We investigate the null geodesic flow and, in particular, the existence of light rings in this vacuum geometry. By evaluating the total topological charge $w$, we show that there exists one unstable light ring ($w=-1$) for each rotation sense of the background. We observe that the swirling background drives the Schwarzschild BH light rings outside the equatorial plane, displaying counterrotating motion with respect to each other, while (both) corotating with respect to the swirling universe. Using backward ray-tracing, we obtain the shadow and gravitational lensing effects, revealing a novel feature for observers on the equatorial plane: the BH shadow displays an odd ${\mathbb{Z}}_2$ (north-south) symmetry, inherited from the same type of symmetry of the spacetime itself: a twisted shadow.

Space-based gravitational wave (GW) detectors are expected to detect the stellar-mass binary black holes (SBBHs) inspiralling in the low-frequency band, which exist several years before the merger. Accurate GW waveforms in the inspiral phase are crucial for the detection and analysis of those SBBHs. In our study, based on post-Newtonian (PN) models, we investigate the differences in the detection, accuracy requirement, and parameter estimation of SBBHs in the cases of LISA, Taiji, and their joint detection. We find that low-order PN models are sufficient for simulating low-mass ($\le 50M_{\odot }$) SBBHs population. Moreover, for detectable SBBHs in space-based GW detectors, over 90% of the GW signals from low-order PN models meet accuracy requirement. Additionally, different PN models do not exhibit significant differences in Bayesian inference. Our research provides a comprehensive reference for balancing computational resources and the desired accuracy of GW waveform generation. It highlights the suitability of low-order PN models for simulating SBBHs and emphasizes their potential in the detection and parameter estimation of SBBHs.

Among the binary sources of interest for LISA some are quasimonochromatic, in the sense that the change in the gravitational wave frequency $\mathrm{\Delta }f\lesssim 1{\mathrm{yr}}^{-1}$ during the observation time. A significant fraction of all Galactic double white dwarfs, as well as other kinds of compact binaries, are quasimonochromatic. We revisit the stationary phase approximation (SPA) commonly used in Fisher matrix calculations in the frequency domain (FD) for these sources, and we show how it is modified by the Doppler shift induced by LISA’s motion and by the LISA pattern functions. We compare our results with previous work in the time domain and discuss the transition from the quasimonochromatic case to the SPA, which applies when $\mathrm{\Delta }f\gtrsim 1{\mathrm{yr}}^{-1}$. The SPA appears to work well when the gravitational wave (GW) frequency $\mathrm{\Delta }f$ is large enough to result in a periodic modulation of the FD waveform associated with the LISA detector response, although the shape of the modulation may differ from the one predicted by the conventional SPA.

We propose the possibility that compact extra dimensions can obtain large size by higher-dimensional inflation, relating the weakness of the actual gravitational force to the size of the observable Universe. Solution to the horizon problem implies that the fundamental scale of gravity is smaller than ${10}^{13}\mathrm{GeV}$, which can be realized in a braneworld framework for any number of extra dimensions. However, requirement of an (approximate) flat power spectrum of primordial density fluctuations consistent with present observations makes this simple proposal possible only for one extra dimension at around the micron scale. After the end of five-dimensional inflation, the radion modulus can be stabilized at a vacuum with positive energy of the order of the present dark energy scale. An attractive possibility is based on the contribution to the Casimir energy of right-handed neutrinos with a mass at a similar scale.

Neutrinos play pivotal roles in determining fluid dynamics, nucleosynthesis, and their observables in core-collapse supernova (CCSN) and binary neutron star merger (BNSM). In this paper, we present a novel phenomenon, collisional flavor swap, in which neutrino-matter interactions trigger the complete interchange of neutrino spectra between two different flavors, aided by neutrino self-interactions. We find that a necessary condition to trigger the collisional swap is occurrences of resonancelike collisional flavor instability. In cases where neutrino self-interactions substantially dominate over the collision rate, the collisional swap occurs in the entire neutrino energy spectrum, while intriguing energy-dependent features can emerge after the completion of flavor swap. Since flavor swaps correspond to the most extreme case in flavor conversions, they have a great potential to affect CCSN and BNSM phenomena.

We obtain bounds on dark matter annihilation using 14 years of publicly available Fermi-LAT data from a set of 54 dwarf spheroidal galaxies, using spectral information from 16 energy bins. We perform this analysis using our updated and publicly available code madhatv2, which can be used to test a variety of models for dark matter particle physics and astrophysics in an accessible manner. In particular, we note that including Carina III in the analysis strengthens constraints on $s$-wave annihilation into two-body Standard Model final states by a factor of $\sim 3$ but broadens the error on the constraint due to the large uncertainty of its $J$-factor. Our findings illustrate the importance of verifying if Carina III is in fact a dwarf spheroidal galaxy and measuring more precisely its $J$-factor. More generally, they highlight the significance of forthcoming discoveries of nearby ultrafaint dwarfs for dark matter indirect detection.

The astrophysical formation channels of binary black hole systems predict correlations between their mass, spin, and redshift distributions, which can be probed with gravitational-wave observations. Population-level analysis of the latest LIGO-Virgo-KAGRA catalog of binary black hole mergers has identified evidence for such correlations assuming linear evolution of the mean and width of the effective spin distribution as a function of the binary mass ratio and merger redshift. However, the complex astrophysical processes at play in compact binary formation do not necessarily predict linear relationships between the distributions of these parameters. In this work, we relax the assumption of linearity and instead search for correlations using a more flexible cubic spline model. Our results suggest a nonlinear correlation between the width of the effective spin distribution and redshift. We also show that the LIGO-Virgo-Kagra collaborations may find convincing Bayesian evidence for nonlinear correlations by the end of the fourth observing run, O4. This highlights the valuable role of flexible models in population analyses of compact-object binaries in the era of growing catalogs.

A yet undetected class of gravitational wave signals is represented by the close encounters between compact objects in highly-eccentric ($e\sim 1$) orbits, that can occur in binary compact systems formed in dense environments such as globular clusters. The expected gravitational signals from these close encounters are short-duration pulses that would repeat over a much longer timescale in case of multiple passages at periastron. These sources represent a unique opportunity of exploring astrophysical formation channels as well as a different way of testing general relativity. Furthermore, in the case of binary systems containing neutron stars, the observation of these sources could help to constrain the neutron star equation of state, thanks to the signature left in the gravitational wave signal by the f-modes excitation that can occur during the encounter. The detection and parameter estimation of these signals is however challenging given the short duration of expected signals and the sensitivities of current ground-based gravitational wave interferometers. We present a novel approach to perform fast detection and parameter estimation of gravitational wave signals from binary close encounters that exploits probabilistic machine learning. We have used conditional normalizing flows to model complex probability distributions and therefore infer posterior distributions for the source parameters. This architecture is able to perform inference in a very short time and its output can be directly compared with classical methods. Fast detection and parameter estimation is very important as it could trigger electromagnetic follow-up campaigns and offer the possibility to study these events in a multimessenger context. To develop and test the algorithm, we have focused on the simulations of single bursts emission obtained using the Effective Fly-by formalism and embedded in the noise of Advanced LIGO and Virgo during their third observing run (O3). Our proposed model outperforms standard Bayesian methods in accuracy and is $\sim 5$ orders of magnitude faster, being able to produce $5\times {10}^4$ posterior samples in just 0.5 s. The results are extremely promising and constitute the first successful attempt for a fast and complete parameter estimation of binary close encounters using deep learning, offering a new approach to study the evolution of orbital parameters of compact binary systems.

Because of the small strain amplitudes of gravitational-wave (GW) signals, unveiling them in the presence of detector/environmental noise is challenging. For visualizing the signals and extracting their waveform for a comparison with theoretical prediction, a frequency-domain whitening process is commonly adopted for filtering the data. In this work, we propose an alternative template-free framework based on autoregressive modeling for denoising the GW data and extracting the waveform. We have tested our framework on extracting the injected signals from the simulated data as well as a series of known compact binary coalescence (CBC) events from the LIGO data. Comparing with the conventional whitening procedure, our methodology generally yields improved cross-correlation and reduced root mean square errors with respect to the signal model.

We calculate the relativistic corrections to prompt $J/\psi$ pair and $J/\psi +\psi (2S)$ hadroproduction through the color singlet channel within the framework of nonrelativistic-QCD (NRQCD) factorization. The short-distance coefficients are obtained by matching full-QCD and NRQCD calculations at the partonic level, in which both squared amplitude and phase space are expanded in $v^2$. We find that such an expansion of the phase space spoils the convergence of NRQCD factorization near the production threshold. To fix this problem, we propose to modify the matching between full QCD and NRQCD by adopting the physical phase space. In this modified approach, the theoretical uncertainties due to the choice of charm quark mass $m_c$ are largely reduced and the overall agreement of our predictions with LHC data is significantly improved, both for total and differential cross sections.

The entanglement of purification $E_P(A:B)$ is a powerful correlation measure, but it is notoriously difficult to compute because it involves an optimization over all possible purifications. In this paper, we prove a new inequality: $E_P(A:B)\ge \frac{1}{2}{S}_R^{(2)}(A:B)$, where $S_R^{(n)}(A:B)$ is the Renyi reflected entropy. Using this, we compute $E_P(A:B)$ for a large class of random tensor networks at large bond dimension and show that it is equal to the entanglement wedge cross section $EW(A:B)$, proving a previous conjecture motivated from AdS/CFT.

We compute the four-gluon vertex from the Curci-Ferrari model at one-loop order for a collinear configuration. Our results display a good agreement with the first lattice data for this vertex, released very recently [Phys. Rev. D 109, 074502 (2024)]. A noteworthy novelty of our work is that we can provide analytical expressions for the four-gluon vertex in collinear configurations, together with a renormalization scheme that allows us to perform reliable perturbative computations even in the infrared regime. We observe an infrared suppression in the form factor associated with the tree-level four-gluon tensor with a possible zero crossing in the deep infrared which demands new lattice investigations to be confirmed. Moreover, we report an infrared divergence in the completely symmetric tensor form factor due to the ghost-loop contributions. These results come as predictions, since previous two-point correlations fix all the available parameters of the model, up to an overall constant factor.

By generalizing the density matrix to a transition matrix between two states, represented as $|\varphi ⟩$ and $|\psi ⟩$, one can define the pseudoentropy analogous to the entanglement entropy. In this paper, we establish an operator sum rule that pertains to the reduced transition matrix and reduced density matrices corresponding to the superposition states of $|\varphi ⟩$ and $|\psi ⟩$. It is demonstrated that the off-diagonal elements of operators can be correlated with the expectation value in the superposition state. Furthermore, we illustrate the connection between the pseudo-Rényi entropy and the Rényi entropy of the superposition states. We provide proof of the operator sum rule and verify its validity in both finite-dimensional systems and quantum field theory. We additionally demonstrate the significance of these sum rules in gaining insights into the physical implications of transition matrices, pseudoentropy, and their gravity dual.

We explore the canonical description of a scalar field in $1+1$ dimensional Minkowski space as a parametrized field theory on an extended phase space that includes additional embedding fields that characterize spacetime hypersurfaces $\mathsf{X}$ relative to which the scalar field is described. This theory is quantized via the Dirac prescription and physical states of the theory are used to define conditional wave functionals $|{\psi }_{\varphi }[\mathsf{X}]⟩$ interpreted as the state of the field relative to the hypersurface $\mathsf{X}$, thereby extending the Page-Wootters formalism to quantum field theory. It is shown that this conditional wave functional satisfies the Tomonaga-Schwinger equation, thus demonstrating the formal equivalence between this extended Page-Wootters formalism and standard quantum field theory. We also construct relational Dirac observables and define a quantum deparametrization of the physical Hilbert space leading to a relational Heisenberg picture, which are both shown to be unitarily equivalent to the Page-Wootters formalism. Moreover, by treating hypersurfaces as quantum reference frames, we extend recently developed quantum frame transformations to changes between classical and nonclassical hypersurfaces. This allows us to exhibit the transformation properties of a quantum field under a larger class of transformations, which leads to a frame-dependent particle creation effect.