Energy-energy correlators (EECs) within high energy jets serve as a key experimentally accessible quantity to probe the scale and structure of the quark-gluon plasma (QGP) in relativistic heavy-ion collisions. The CMS Collaboration’s first measurement of the modification to the EEC within single inclusive jets in $\mathrm{Pb}+\mathrm{Pb}$ collisions relative to $\mathrm{p}+\mathrm{p}$ collisions reveals a significant enhancement at small angles, which may arise from jet transverse momentum $p_T$ selection biases due to jet energy loss. We investigate the dependence of jet EECs on the flavor of the initiating parton. The EEC distribution of a gluon jet is broader and the peak of transition from the perturbative to the nonperturbative regime occurs at a larger angle than that of a quark jet. Such flavor dependence leads to the different EECs for $\gamma$-jets and single inclusive jets due to their different flavor composition. It is also responsible for a colliding energy dependence of EECs of single inclusive jets at fixed jet energy. We also investigate the impact of flavor composition variation on the $p_T$ dependence of the jet EEC. We further propose that a change in the gluon jet fraction in $\mathrm{A}+\mathrm{A}$ collisions compared to $\mathrm{p}+\mathrm{p}$ can also contribute to a non-negligible enhancement of the medium modified EEC at small angles. Using the jewel model, we predict the reduction of the gluon jet fraction in $\mathrm{A}+\mathrm{A}$ collisions and estimate its impact on the EEC.

The treatment of charmed hadron production in the framework of the QGSJET-III Monte Carlo generator is developed, including both perturbative and nonperturbative contributions. For the former, a leading order (LO) perturbative formalism is employed. The so-called $K$ factor designed to take effectively into account higher-order corrections, which controls the magnitude of the LO perturbative contribution, is fixed based on a comparison with experimental data on $D$ meson production at the Large Hadron Collider. For the nonperturbative intrinsic charm, a phenomenological Regge-based treatment is developed, with the corresponding normalization being chosen based on measurements of the spectra of ${\mathrm{\Lambda }}_c$ baryons at large values of Feynman $x$. The model is applied for a calculation of the prompt atmospheric muon neutrino flux in the 10–100 TeV and 1–10 PeV energy intervals.

It has been known for almost a decade that delayed photon noise with a power law time profile follows scintillation pulses in liquid xenon particle detectors. The origin of the noise has remained unknown, and in the past two years, has become an overwhelming background for low-threshold dark matter searches aimed at $\mathcal{O}(10)\mathrm{GeV}$ dark matter particle masses, as well as measurements of coherent neutrino-nucleus scattering of ${}^8\mathrm{B}$ solar neutrinos. We have performed a comprehensive series of tests in a small liquid xenon cell at LBL, from which we conclude that the dominant component of this delayed photon noise is due to UV-induced fluorescence of quartz photosensor windows.

An $s$-jet tagging approach to determine the Cabibbo-Kobayashi-Maskawa matrix component $|V_{ts}|$ directly in the dileptonic final state events of the top pair production in proton-proton collisions has been previously studied by measuring the branching fraction of the decay of one of the top quarks by $t\to sW$. The main challenge is improving the discrimination performance between strange jets from top decays and other jets. This study proposes novel jet discriminators, called disaja, using a Transformer-based deep learning method. The first model, disaja-h, utilizes multidomain inputs (jets, leptons, and missing transverse momentum). An additional model, disaja-l, further improves the setup by using lower-level jet constituent information, rather than the high-level clustered information. disaja-l is a novel model that combines low-level jet constituent analysis with event classification using multidomain inputs. The model performance is evaluated via a CMS-like LHC Run 2 fast simulation by comparing various statistical test results to those from a Transformer-based jet classifier which considers only the individual jets. This study shows that the disaja models have significant performance gains over the individual jet classifier, and we show the potential of the measurement during Run 3 of the LHC and the High-Luminosity LHC.

In the context of anti-de Sitter/conformal field theory , gravitational shockwaves serve as a geometric manifestation of boundary quantum chaos. We study this connection in general diffeomorphism-invariant theories involving an arbitrary number of bosonic fields. Specifically, we demonstrate that theories containing spin-2 or higher-spin fields generally admit classical localized shockwave solutions on black hole backgrounds, whereas spin-0 and spin-1 theories do not. As in the gravitational case, these higher-spin shockwaves provide a means to compute the out-of-time-order correlator. Both the Lyapunov exponent and the butterfly velocity are found to universally agree with predictions from pole skipping. In particular, higher-spin fields lead to a Lyapunov exponent that violates the chaos bound and a butterfly velocity that may exceed the speed of light.

We demonstrate that the necessary condition for $SO(N)\times SO(N)$ duality invariance manifests as a partial differential equation in two-dimensional scalar theories. This condition, expressed as a partial differential equation, corresponds precisely to the integrability condition. We derive a general perturbation solution to this partial differential equation, which includes both a root $T\overline{T}$ flow equation and an irrelevant $T\overline{T}$-like flow equation. Additionally, we identify a general form for these flow equations that commute with each other. Our results establish a general integrable theory characterized by theory-dependent coefficients at each order in the $\lambda$ expansion. This unified framework systematically classifies all integrable theories possessing two Lorentz-invariant variables ($P_1$, $P_2$) while accommodating arbitrary orders of the coupling constants ($\lambda$, $\gamma$). The theory provides a comprehensive classification scheme that encompasses both known and novel integrable systems within this class.

We present a novel framework for deriving integral constraints for correlators on conformal line defects. These constraints emerge from the nonlinearly realized ambient-space conformal symmetry. To validate our approach, we examine several examples and compare them against existing data for the four-point function of the displacement operator. Additionally, we provide a few new predictions that extend the current understanding of these correlators.

In four-dimensional scalar-tensor theories derived via dimensional regularization with a conformal rescaling of the metric, we study the stability of planar black holes (BHs) whose horizons are described by two-dimensional compact Einstein spaces with vanishing curvature. By taking an infinite sum of Lovelock curvature invariants, it is possible to construct BH solutions whose metric components remain nonsingular at $r=0$, with a scalar-field derivative given by ${\varphi }^{\prime }(r)=1/r$, where $r$ is the radial coordinate. We show that such BH solutions suffer from a strong coupling problem, where the kinetic term of the even-parity scalar-field perturbation associated with the timelike coordinate vanishes everywhere. Moreover, we find that these BHs are subject to both ghost and Laplacian instabilities for odd-parity perturbations near $r=0$. Consequently, the presence of these pathological features rules out regular planar BHs with the scalar-field profile ${\varphi }^{\prime }(r)=1/r$ as physically viable and stable configurations.

We analyze the near-horizon symmetries of static, axisymmetric, four-dimensional black holes with spherical and toroidal horizon topologies in vacuum general relativity. These black hole solutions, collectively referred to as local/distorted black holes, are known in closed form and are not asymptotically flat. Building on earlier works in the literature that primarily focused on black holes with spherical topology, we compute the algebra of the Killing vector fields that preserve the asymptotic structure near the horizons and the algebra of the associated Noether-Wald charges under the boundary conditions that produce the spin-$s$ ${\mathrm{BMS}}_d$ and the Heisenberg-like algebras. We show that a similar analysis extends to all local axisymmetric black holes. The toroidal topology of the holes changes the algebras considerably. For example, one obtains two copies of spin-$s$ ${\mathrm{BMS}}_3$ instead of spin-$s$ ${\mathrm{BMS}}_4$. We also revisit the thermodynamics of black holes under these boundary conditions. While previous studies suggested that spin-$s$ ${\mathrm{BMS}}_d$ preserves the first law of thermodynamics for isolated horizons ($\kappa =\text{const}$), our analysis indicates that this is not generally the case when the spin parameter $s$ is nonzero. A nonzero $s$ can be seen as introducing a conical singularity (in the Euclidean quantum gravity sense) or a Hamiltonian that causes soft hairs to contribute to the energy. This leads us to interpret the spin-$s$ ${\mathrm{BMS}}_d$ boundary condition as arising in the context of dynamical black holes.

Because of the short gravitational timescale of Sgr A*, variable emissions near the galactic center are expected in the very-long-baseline interferometry observations. Phenomenologically, the high-flux variable emissions could be interpreted as occasional events from hotspots within accretion disks. It provides a probe of black hole (BH) geometry and accretion matter in the strong-field regime of gravity. In this study, we find that light curve profile alone is not proper for distinguishing BH geometries, as our results show that the profiles, even including those from higher-order images, are dependent on hotspot shapes, which are known in practice as amorphous. To alleviate this situation, we examine the spatial-temporal correlations between multiple images of the corotating hotspots. Our results find that the correlations, particularly those from higher-order images, could serve as a robust observable to reflect the inclination angles and BH geometries, because (i) the correlated band structure is independent of the hotspot shapes and (ii) the correlations from higher-order images could encode BH geometries and exhibit no overlap with observational signatures from the lower-order ones. We present a comprehensive study on correlations from primary the eighth-order images with various orbital configurations and inclination angles and show its observational signatures. It is expected that BH geometries can be inferred via the spatial-temporal correlation analysis.

The spins of binary black holes measured with gravitational waves provide insights about the formation, evolution, and dynamics of these systems. However, interpreting these measurements—especially for heavy black holes—remains an open problem. While the imprint of spin during the inspiral phase, where the black holes are well separated, is understood through analytic descriptions of the dynamics, no such expressions exist for the merger. Though numerical relativity simulations provide an exact solution (to within numerical error), the imprint of the full six spin degrees of freedom on the signal is not transparent. In the absence of analytic expressions for the merger and to advance our ability to interpret massive binary black hole spin measurements, here we propose a waveform-based approach. Leveraging a neural network to efficiently calculate mismatches between waveforms, we identify regions in the parameter space of spins and mass ratio that result in low mismatches and, thus, similar waveforms. We map these regions with a Gaussian fit, thus identifying correlations and quantifying their strength. For low-mass, inspiral-dominated systems, we recover the known physical imprint: Larger aligned spins are correlated with more equal masses as they have opposite effects on the inspiral length. For high-mass, merger-dominated signals, a qualitatively similar correlation is present, though its shape is altered and strength decreases with larger total mass. Correlations between in-plane spins and mass ratio follow a similar trend, with their shape and strength altered as the mass increases. Our new methodology of waveform-based correlation mapping provides a first step toward systematically modeling spin effects in merger-dominated signals across the full intrinsic parameter space and motivates future effective spin parameters beyond the reach of analytic methods.

The cosmic curvature ${\mathrm{\Omega }}_K$ is an important parameter related to the inflationary cosmology and the ultimate fate of the universe. In this work, we adopt the noncosmic microwave background (CMB) observations to constrain ${\mathrm{\Omega }}_K$ in the $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model and its extensions. The DESI baryon acoustic oscillation, DES type Ia supernova, cosmic chronometer, and strong gravitational lensing time delay data are considered. We find that the data combination favors an open universe in $\mathrm{\Lambda }\mathrm{CDM}$, specifically ${\mathrm{\Omega }}_K=0.106\pm 0.056$ at the $1\sigma$ level, which is in $2.6\sigma$ tension with the Planck CMB result supporting our Universe being closed. In the $\mathrm{\Lambda }\mathrm{CDM}$ extensions, the data combination is consistent with a flat universe. It is noteworthy that when the cosmic chronometer data is excluded, the derived constraints demonstrate increased statistical preference for an open universe. Specifically, ${\mathrm{\Omega }}_K=0.146\pm 0.060$ in $\mathrm{\Lambda }\mathrm{CDM}$, which is in $3.1\sigma$ tension with the CMB result, and the flat universe scenario can be ruled out at $>1\sigma$ level in the $\mathrm{\Lambda }\mathrm{CDM}$ extensions. The constraining power mainly stems from DESI’s distance measurements. Given the advantages of the full-shape power spectrum in ${\mathrm{\Omega }}_K$ measurements and the support for a closed universe from previous full-shape analyses, it is necessary to validate our findings with DESI’s full-shape data. We adopt the Akaike information criterion to compare different cosmological models. The result shows that nonflat models fit the observational data better than the flat $\mathrm{\Lambda }\mathrm{CDM}$ model, which indicates that flat $\mathrm{\Lambda }\mathrm{CDM}$ may not be the ultimate model of cosmology.

The 21-cm forest, composed of spectral absorption features from high-redshift background radio sources, provides a unique probe for studying small-scale structures during the epoch of reionization. It is particularly sensitive to detecting small-scale structures and early heating processes. Despite the rich information contained in the 21-cm forest signal, the complexity of directly modeling the signal has led to a lack of effective analytical models. However, the one-dimensional (1D) power spectrum of the 21-cm forest contains valuable information about the matter power spectrum, making analytical modeling feasible. This work employs an analytical modeling approach based on the halo model, which links the distribution of matter to dark matter halos, allowing for effective predictions of cosmic structure formation and its impact on the 21-cm signal. By considering various parameter scenarios within the halo model framework, particularly different dark matter particle masses and varying levels of cosmic heating, we can capture the complexities of small-scale structures and make the 1D power spectrum modeling applicable across a wide range of parameters. This method not only enhances our understanding of the 21-cm forest signal but also provides theoretical support for future observational data. Observing the 21-cm forest with large radio telescopes, such as the Square Kilometre Array, is anticipated to enable simultaneous exploration of dark matter properties and the heating history of the early Universe.

We investigate the possibility that primordial black holes (PBHs) can be formed from large curvature perturbations generated during the waterfall phase transition in a hybrid inflation model driven by an axionlike particle (ALP) $\varphi$. The model predicts a spectral index $n_s\simeq 0.964$ and a tensor-to-scalar ratio $r\simeq 0.003$, in agreement with Planck data and potentially testable by next-generation cosmic microwave background (CMB) experiments such as CMB-S4 and LiteBIRD. We find that the PBH mass and the peak of the associated scalar-induced gravitational wave spectrum are correlated with the ALP mass. In particular, PBHs in the mass range ${10}^{-13}-{10}^{-12}{M}_{\odot }$ can constitute either the entire dark matter content of the Universe or a significant fraction of it. The predicted second-order gravitational waves from this mechanism are within the sensitivity reach of future observatories like Laser Interferometer Space Antenna and Einstein Telescope. The typical reheating temperature in the model is around ${10}^6–{10}^7\mathrm{GeV}$ is consistent with big bang nucleosynthesis constraints.

In contrast to the large-scale primordial power spectrum ${\mathcal{P}}_{\zeta }(k)$ and primordial non-Gaussianity $f_{\mathrm{NL}}$, which are strictly constrained, the small-scale ${\mathcal{P}}_{\zeta }(k)$ and $f_{\mathrm{NL}}$ are not as limited. Considering local-type primordial non-Gaussianity, we study the primordial black holes (PBHs) and scalar induced gravitational waves (SIGWs) caused by large-amplitude small-scale primordial power spectrum. By analyzing current observational data from pulsar timing array (PTA), cosmic microwave background (CMB), baryon acoustic oscillations (BAO), and abundance of PBHs, and combining it with the signal-to-noise ratio (SNR) analysis of Laser Interferometer Space Antenna (LISA), we rigorously constrain the parameter space of ${\mathcal{P}}_{\zeta }(k)$ and $f_{\mathrm{NL}}$. Furthermore, we examine the effects of different shapes of the primordial power spectrum on these constraints and comprehensively calculate the Bayesian factors for various models. Our results indicate that SIGWs generated by a monochromatic primordial power spectrum are more likely to dominate current PTA observations, with the corresponding constraint on the primordial non-Gaussian parameter being $-10.0<f_{\mathrm{NL}}<1.2$.

According to the Schrödinger-Poisson equations, fuzzy dark matter (FDM) can form a stable equilibrium configuration, the so-called FDM soliton. In principle, given the FDM particle mass, the profile of the FDM soliton is fixed. In practice, however, there is a great diversity of structures in the Universe. Possible causes of such diversity can lie in such sources as the gravitoelectric field due to a central supermassive black hole, the gravitomagnetic field due to the system angular momentum, and an ellipsoidal baryon background. We find that the effects of the gravitomagnetic field due to the soliton’s self-angular momentum are very weak while those of the other sources are considerable.

Gravitational waves from merging binary neutron stars carry characteristic information about their astrophysical properties, including component masses and tidal deformabilities, that are needed to infer their radii. In this study, we use Bayesian inference to quantify the precision with which radius can inferred with upgrades in the current gravitational wave detectors and next-generation observatories such as the Einstein Telescope and Cosmic Explorer. We assign evidences for a set of plausible equations of state, which are then used as weights to obtain radius posteriors. We find that prior choices and the loudness of observed signals limit the precision and accuracy of inferred radii by current detectors. In contrast, next-generation observatories can resolve the radius precisely and accurately, across most of the mass range to within $\lesssim 5\%$ for both soft and stiff equations of state. We also explore how the choice of neutron star mass prior can influence the inferred masses and, in turn, potentially affect radius measurements. However, we find that using an astrophysically motivated prior does not significantly impact the radius measurement of an individual neutron star.

The majority of gravitational wave events detected by the LIGO/Virgo/Kagra Collaboration originate from binary black hole (BBH) mergers, for which no confirmed electromagnetic counterparts have been identified to date. However, if such mergers occur within the disk of an active galactic nucleus (AGN), they may generate observable optical flares induced by relativistic jet activity and shock-heated gas. We present results from a long-term optical follow-up of the GW event S231206cc, conducted with the T80-South telescope as part of the S-PLUS Transient Extension Program (STEP). Our search prioritized AGN-hosted environments by crossmatching the GW localization with known AGN catalogs. No candidate met the criteria for a viable optical counterpart. We explored three BBH merger scenarios predicting optical emission in AGN disks: (i) ram pressure–stripping, (ii) long term emission of an emerging jet-cocoon, and (iii) jet breakout and shock cooling. Using our observational cadence and depth, we constrained the BBH parameter space, including the remnant’s location within the AGN disk, kick velocity, and supermassive black hole (SMBH) mass. Detectable flares are most likely when mergers occur at 0.01–0.1 parsecs from SMBHs of ${10}^7–{10}^8$ solar masses, where short delay times and long durations best aligns with our follow-up strategy. These results provide a framework for identifying AGN-hosted BBH counterparts and guiding future multimessenger efforts.

We investigate analog gravity phenomena arising as a result of the linear perturbation of the spherically symmetric accretion flows onto nonrotating black holes, where the gravitational field is determined by a set of post-Newtonian pseudo-Schwarzschild black hole potentials and the infalling matter is described by a relativistic multispecies equation of state. The stationary transonic integral accretion solutions corresponding to the steady state of the aforementioned type of accreting systems are constructed and the stability analysis of such solutions is performed through the time-dependent linear perturbation of the accretion flow. Such linear stability analysis leads to the formation of a black hole–like sonic metric embedded within the infalling matter. The acoustic horizons are then identified by constructing the causal structure, i.e., the Carter-Penrose diagrams. The variation of the analog surface gravity corresponding to the aforementioned sonic metric has been studied as a function of various parameters governing the accretion flow.