Primordial black holes (PBH), supposedly formed in the very early Universe, have been proposed as a possible viable dark matter candidate. In this work we characterize the expected gravitational wave (GW) losses from a population of PBHs orbiting Sgr ${\mathrm{A}}^{*}$, the supermassive black hole at the Galactic center (GC), and assess the signal detectability by the planned space-borne interferometer LISA and by the proposed next generation space-borne interferometer $\mu \mathrm{Ares}$. Assuming that PBHs indeed form the entire diffuse mass allowed to reside within the orbit of the S2 star, we compute an upper limit to the expected GW signal both from resolved and nonresolved sources, under the further assumptions of monochromatic mass function and thermally distributed eccentricities. By comparing with our previous work where PBHs on circular orbits were assumed, we show for $1M_{\odot }$ PBHs how the GW signal from high harmonics over a 10 year data stream increases by a factor of six the chances of LISA detectability, from the $\approx 10\%$ of the circular case, to $\approx 60\%$, whereas multiple sources can be identified in 20% of our mock populations. The background signal, made by summing up all non resolved sources, should be certainly detectable thanks to the PBHs with higher eccentricity evolving under two body relaxation. In the case of $\mu \mathrm{Ares}$, because of its improved sensitivity in the $\mathrm{\mu }\mathrm{Hz}$ band, one third of the entire population of PBHs orbiting Sgr ${\mathrm{A}}^{*}$ would be resolved. The background noise from the remaining non resolved sources should be detectable as well. Finally, we present the results for different PBH masses.

In this work, we use general relativistic magnetohydrodynamics simulations to explore the effect of spin orientation on the dynamics of gas in the vicinity of merging black holes. We present a suite of eight simulations of unequal-mass, spinning black hole binaries embedded in magnetized clouds of matter. Each binary evolution covers approximately 15 orbits before the coalescence. The geometry of the accretion flows in the vicinity of the black holes is significantly altered by the orientation of the individual spins with respect to the orbital angular momentum, with the primary black hole dominating the mass accretion rate $\dot{M}$. We observe quasiperiodic modulations of $\dot{M}$ in most of the configurations, whose amplitude is dependent on the orientation of the black hole spins. We find the presence of a relation between the average amplitude of $\dot{M}$ and the spin precession parameter ${\chi }_{\mathrm{p}}$ showing that spin misalignment systematically leads to stronger modulation, whereas configurations with spins aligned to the orbital angular momentum damp out the quasiperiodicity. This finding suggests a possible signature imprinted in the accretion luminosity of precessing binaries approaching merger and has possible consequences on future multimessenger observations of massive binary black hole systems.

We investigate the production of spin-$3/2$ hyperon pairs, ${\mathrm{\Omega }}^{-}{\overline{\mathrm{\Omega }}}^{+}$, in electron-positron annihilation within the helicity formalism. A refined selection of helicity basis matrices is proposed to relate polarization expansion coefficients and spin density matrix elements and to illuminate their inherent physical interpretations and symmetrical properties. With a novel parametrization scheme of helicity amplitudes, we perform an analysis of polarization correlation coefficients for double-tag ${\mathrm{\Omega }}^{-}{\overline{\mathrm{\Omega }}}^{+}$ pairs. We present three sets of expressions to describe the decay of ${\mathrm{\Omega }}^{-}$ hyperons, and further address the existing tension in the measurements of its decay parameters, particularly ${\varphi }_{\mathrm{\Omega }}$. The method and the framework developed in this paper can also be applied to studies of the production and decay mechanisms of other spin-$3/2$ particles.

In this work, we have explored the sensitivity of multilepton final states in probing the gaugino sector of a R-parity violating supersymmetric scenario with specific lepton number violating trilinear couplings (${\lambda }_{ijk}$) being nonzero. The gaugino spectrum is such that the charged leptons in the final state can arise from the R-parity violating decays of the lightest supersymmetric particle (LSP) as well as R-parity conserving decays of the next-to-LSP (NLSP). Apart from a detailed cut-based analysis, we have also performed a machine learning-based analysis using a boosted decision tree algorithm, which provides much better sensitivity. In the scenarios with nonzero ${\lambda }_{121}$ and/or ${\lambda }_{122}$ couplings, the LSP pair in the final states decays to $4l$ $(l=e,\mu )+{\cancel{\mathrm{E}}}_{\mathrm{T}}$ final states with a 100% branching ratio. We have shown that under this circumstance, a final state with $\ge 4l$ has the highest sensitivity while probing for gaugino masses. We also discuss how the sensitivity can change in the presence of $\tau$ lepton(s) in the final state due to other choices of trilinear couplings. We present our results through the estimation of the discovery and exclusion contours in the gaugino mass plane for both the high luminosity LHC (HL-LHC with $\sqrt{s}=14\mathrm{TeV}$ and $\mathcal{L}=3000{\mathrm{fb}}^{-1}$) and high energy LHC (HE-LHC with $\sqrt{s}=27\mathrm{TeV}$ and $\mathcal{L}=3000{\mathrm{fb}}^{-1}$). For the ${\lambda }_{121}$ and/or ${\lambda }_{122}$ nonzero scenario, the projected $2\sigma$ exclusion limit on NLSP masses reaches upto 2.37 TeV and 4 TeV for the HL-LHC and the HE-LHC, respectively, by using a machine learning based algorithm. We observe an enhancement of $\sim 380(190)\mathrm{GeV}$ in the projected $2\sigma$ exclusion limit on the NLSP masses at the 27 (14) TeV LHC. Considering the same final state ($N_l\ge 4$) for the ${\lambda }_{133}$ and/or ${\lambda }_{233}$ nonzero scenario, we find that the corresponding $2\sigma$ projected limits are $\sim 1.97\mathrm{TeV}$ and $\sim 3.25\mathrm{TeV}$ for the HL-LHC and HE-LHC, respectively.

In this work, we propose that the odderon is a Regge spin-3 odd-glueball tensor. To demonstrate the proposal, we study the $pp$ and $p\overline{p}$ elastic scattering by including the contributions of the spin-3 odderon and spin-2 pomeron exchange in the processes. The phenomenological effective Lagrangian approach is used to calculate the $pp$ and $p\overline{p}$ elastic scattering amplitudes at the tree level. Additionally, the Donnachie-Landschoff ansatz of the odderon and pomeron propagators was used in further analysis. We fit the theoretical results with the various experimental data of the $pp$ and $p\overline{p}$ scattering at the TeV scale to determine the model parameters in the present work. By using the model parameters, the Chew-Frautschi plot of the tensor odderon Regge trajectory is evaluated. As a result, the odderon spin-3 mass is predicted to be 3.2 GeV. In addition, a phase rotation is applied to the amplitude of our model in order to satisfy the geometric scaling at a very low $t$ region. Moreover, the total cross section of our model is compatible with the results from TOTEM and its extrapolation from D0 collaboration. It was found that the total cross section also satisfies the Friossart bound at the Regge limit.

We improve the complex scaling method (CSM) to obtain virtual states, which is challenging in the conventional CSM. Our approach solves the Schrödinger equation in momentum space as an eigenvalue problem by choosing flexible contours. It proves to be highly effective in identifying the poles across different Riemann sheets in multichannel scatterings. This approach is more straightforward and efficient than employing the Lippmann-Schwinger equation and using a root-finding algorithm to search for the zeros of the Fredholm determinant. This advancement significantly extends the capabilities of the CSM in accurately characterizing the virtual states in quantum systems.

The knowledge of what entered a black hole (BH) is completely lost as it evaporates. This contradicts the unitarity principle of quantum mechanics and is referred to as the information loss paradox. Understanding the end stages of BH evaporation is key to resolving this paradox. As a first step, we need to have exact models that can mimic 4D BHs in general relativity in classical limit and have a systematic way to include high-energy corrections. While there are various models in the literature, there is no systematic procedure by which one can study high-energy corrections. In this work, for the first time, we obtain Callan, Giddings, Harvey, and Strominger (CGHS)—a ($1+1$)-D—model from 4D Horndeski action—the most general scalar-tensor theory that does not lead to Ostrogradsky ghosts. We then show that 4D Horndeski action can systematically provide a route to include higher-derivative terms relevant at the end stages of black hole evaporation. We derive the leading order Hawking flux while discussing some intriguing characteristics of the corrected CGHS models. We compare our results with other works and discuss the implications for primordial BHs.

Neutron stars (NSs) serve as laboratories for probing strongly interacting matter at the most extreme densities and nearly vanishing temperature. Their inner cores are expected to be dense enough to host deconfined quark matter. Utilizing state-of-the-art theoretical and multimessenger constraints, we statistically determine the bulk properties of dense NS matter. We show that the speed of sound can be expressed in terms of the slope and curvature of the energy per particle. We demonstrate that the restoration of conformal symmetry requires changing the sign of the curvature of the bulk energy per particle as a function of energy density. Furthermore, we find that such a sign change is closely related to the peak in the speed of sound. We argue that the curvature of the energy per particle may serve as an approximate order parameter that signifies the onset of strongly coupled conformal matter in the NS core.

QCD interactions for equal-mass fermion flavors are flavor blind. This fact is often used to state that disconnected sea-quark loop contributions are equal for $u$ and $d$ quarks in the mass symmetric case and therefore these disconnected sea-quark loop contributions cannot contribute to the well-known $\overline{d}-\overline{u}$ asymmetry in the proton. Instead, it is argued that one must look to the connected sector of lattice QCD correlation functions to find this difference. In this presentation, we note that these statements are true provided unphysical contributions in the sea-quark loop sector are included, contributions from baryons that do not appear in the physical spectrum. To respect the Pauli principle, these unphysical contributions from the disconnected sea-quark loop sector must cancel equally unphysical contributions in the connected sector. The remaining disconnected sea-quark loop contributions no longer have a balance between $\overline{d}$ and $\overline{u}$. Upon considering only physically observed baryons in the loop contributions, we illustrate an important contribution from the sea-quark loop sector to $\overline{d}-\overline{u}$ that enhances the leading connected contribution by 12%.

We present a simulation strategy for the real-time dynamics of quantum fields, inspired by reinforcement learning. It builds on the complex Langevin approach, which it amends with system-specific prior information, a necessary prerequisite to overcome this exceptionally severe sign problem. The optimization process underlying our machine-learning approach is made possible by deploying inherently stable solvers of the complex Langevin stochastic process and a novel optimality criterion derived from insight into so-called boundary terms. This conceptual and technical progress allows us to both significantly extend the range of real-time simulations in $1+1\mathrm{d}$ scalar field theory beyond the state of the art and to avoid discretization artifacts that plagued previous real-time field theory simulations. Limitations of and promising future directions are discussed.

We examine the couplings of quarkonium hybrids to heavy-light meson pairs in the Born-Oppenheimer approximation for QCD. The lowest hybrid multiplets consist of bound states of the ${\mathrm{\Pi }}_u$ and ${\mathrm{\Sigma }}_u^{-}$ potentials. We find that the ${\mathrm{\Sigma }}_u^{-}$ potential can couple to pairs of $S$-wave mesons through string breaking, while the ${\mathrm{\Pi }}_u$ potential cannot. From this observation, we derive model-independent selection rules that contradict previous expectations that quarkonium hybrids are forbidden to decay into pairs of $S$-wave mesons. These Born-Oppenheimer selection rules are consistent with the partial decay widths of the lowest charmonium hybrid with exotic quantum numbers $J^{PC}=1^{-+}$ recently calculated using lattice QCD.

We search for the baryon and lepton number violating charm decays, $D\to p\ell$, where $D$ is either a $D^0$ or a ${\overline{D}}^0$ and $\ell$ is a muon or an electron, using a data sample of $921{\mathrm{fb}}^{-1}$ collected by the Belle detector at the KEKB asymmetric energy $e^{+}{e}^{-}$ collider. In the absence of significant signals, we set upper limits on the branching fractions in the range $(5–8)\times {10}^{-7}$ at a 90% confidence level, depending on the decay mode.

In this paper we establish a connection between segmented strings propagating in ${\mathrm{AdS}}_{d+1}$ and ${\mathrm{CFT}}_d$ subsystems in Minkowski spacetime characterized by quantum information theoretic quantities calculated for the vacuum state. We show that the area of the world sheet of a string segment on the AdS side can be connected to fidelity susceptibility (the real part of the quantum geometric tensor) on the CFT side. This quantity has another interpretation as the computational complexity for infinitesimally separated states corresponding to causal diamonds that are displaced in a spacelike manner according to the metric of kinematic space. These displaced causal diamonds encode information for a unique reconstruction of the string world sheet segments in a holographic manner. Dually the bulk segments are representing causally ordered sets of consecutive boundary events in boosted inertial frames or in noninertial ones proceeding with constant acceleration. For the special case of ${\mathrm{AdS}}_3$ one can also see the segmented stringy area in units of $4GL$ ($G$ is Newton’s constant and $L$ is the AdS length) as the conditional mutual information $I(A,C|B)$ calculated for a trapezoid configuration arising from boosted spacelike intervals $A$, $B$ and $C$. In this special case the variation of the discretized Nambu-Goto action leads to an equation for entanglement entropies in the boundary theory of the form of a Toda equation. For arbitrary $d$ the string world sheet patches are living in the modular slices of the entanglement wedge. They seem to provide some sort of tomography of the entanglement wedge where the patches are linked together by the interpolation ansatz, i.e., the discretized version of the equations of motion for the Nambu-Goto action.

We examine one of the standard loci for studying electromagnetic wave emission—the radiation from an oscillating electric dipole—in a model in which the electromagnetic sector is modified to include novel $CPT$- and Lorentz-violating propagation effects involving a preferred axial vector background. We evaluate the vacuum-birefringent radiation fields, including nonperturbative terms where appropriate. In general, the energy momentum carried by the fields in this model is known to have a complicated nonperturbative structure, which cannot be captured by naive power-series expansions in the components of the preferred background vector. However, we nevertheless find that at the lowest nontrivial orders, there are actually no modifications to the Larmor expressions for the energy-momentum emission.

We illustrate how the conformal Ward identities (CWI) and the gravitational chiral anomaly completely determine the structure of the $⟨TT{J}_5⟩$ (graviton-graviton-chiral gauge current) correlator in momentum space. This analysis extends our previous results on the anomaly vertices $⟨AVV⟩$ and $⟨AAA⟩$, as well as the $⟨TJJ⟩$ parity-odd conformal anomaly vertex in general CFTs. The $⟨TT{J}_5⟩$ plays a fundamental role in the analysis of the conformal backreaction in early Universe cosmology, affecting the particle content and the evolution of the primordial plasma. Our approach is nonperturbative and not Lagrangian based, requiring the inclusion of a single anomaly pole in the solution of the anomaly constraint. The pole and its residue, along with the CWIs, determine the entire correlator in all of its sectors (longitudinal/transverse), all of which are proportional to the same anomaly coefficient. The method does not rely on a specific expression of the $CP$-odd anomalous current, which in free field theory can be represented either by a bilinear fermion current or by a gauge-dependent Chern-Simons current; it relies solely on the symmetry constraints. We compute the correlator perturbatively at one loop in free field theory and verify its exact agreement with the nonperturbative result. A comparison with the perturbative analysis confirms the presence of a sum rule satisfied by the correlator, similar to the parity-even $⟨TJJ⟩$ and the chiral $⟨AVV⟩$.

Parametrized Kerr spacetimes allow us to test the nature of black holes in model-independent ways. Such spacetimes contain several arbitrary functions and, as a matter of practicality, one Taylor expands them about infinity and keeps only to finite orders in the expansion. In this paper, we focus on the parametrized spacetime preserving Killing symmetries of a Kerr spacetime and show that an unphysical divergence may appear in the metric if such a truncation is performed in the series expansion. To remedy this, we redefine the arbitrary functions so that the divergence disappears, at least for several known black hole solutions that can be mapped to the parametrized Kerr spacetime. We propose two restricted classes of the refined parametrized Kerr spacetime that only contain one or two arbitrary functions and yet can reproduce exactly all the example black hole spacetimes considered in this paper. The Petrov class of the parametrized Kerr spacetime is of type I while that for the restricted class with one arbitrary function remains type D. We also compute the ringdown frequencies and the shapes of black hole shadows for the parametrized spacetime and show how they deviate from Kerr. The refined black hole metrics with Kerr symmetries presented here are practically more useful than those proposed in previous literature.

Early dark energy (EDE), introduced at the epoch of matter-radiation equality to alleviate the Hubble tension, has posed a new coincidence problem: why does EDE appear at matter-radiation equality when their physics are completely unrelated? To solve this coincidence problem, we propose a new EDE model based on scalar-tensor gravity with the idea that EDE is triggered by spacetime dynamics that encodes the cosmic radiation-matter transition. Our model can induce EDE naturally at matter-radiation equality without unnatural parameter tuning. Compared with other EDE models, a distinguishing feature of ours is that it can also induce a new energy component during cosmic matter-dark energy transition. This is testable with low-redshift observations.

This work concerns the dynamics of the conformal cubic scalar field on a Schwarzschild–anti–de Sitter background. The main focus is on understanding how it depends on the size of the black hole and the Robin boundary condition. We identify a critical curve in the parameter space that separates regions with distinct asymptotic behaviors. For defocusing nonlinearity, the global attractor undergoes a pitchfork bifurcation, whereas for the focusing case, we identify a region of the phase space where all solutions blow up in finite time. In the course of this study we observe an interplay between black hole geometry, boundary conditions, and the nonlinear dynamics of scalar fields in asymptotically anti–de Sitter spacetime.

Canonical gravity is a formulation of general relativity where an evolving space reproduces the usual spacetime theory, and, unlike other formulations, it requires fewer assumptions—in particular, in the relationship between the gravitational field and the metric field. This freedom in the assumptions is the key to emergent modified gravity, a canonical theory in which the spacetime metric is not fundamental, but rather it is an emergent object composed of the truly fundamental fields. This peculiar feature of emergent modified gravity compared to other approaches can be used to model new effects, such as those provided by quantum gravity in an effective description. We discuss how matter fields can be coupled to emergent modified gravity, we realize the coupling of the (isentropic) perfect fluid, and we explicitly obtain the Hamiltonian of spherically symmetric systems and identify the symmetries of the coupled system. We formulate the Oppenheimer-Snyder collapse model in canonical terms as an adaptation of the fluid frame to the canonical foliation, permitting us to easily extend the conditions of the model to emergent modified gravity and obtain an exact solution to the dust collapsing from spatial infinity, including some effects suggested by quantum gravity in spherical symmetry. In this solution, the collapsing dust forms a black hole, and then reaches a minimum radius inside the black hole. While the geometry on this minimum-radius surface is regular in the vacuum, it turns out to be singular in the presence of dust. However, the fact that the geometry is merely emergent in this picture, and all the fundamental fields that compose the phase space are regular on such a surface, allows us to continue the canonical solution past it in a meaningful way, obtaining the global structure for the interior of the star. Thus, the matter reaches the minimum-radius surface with vanishing velocity and finite positive acceleration, and it proceeds to emerge outward, now behaving as a white hole. This star-interior solution can then be complemented by the vacuum solution describing the star-exterior region by a continuous junction at the star’s radius. This gluing process can be viewed as the imposition of boundary conditions, which is nonunique and does not follow from solving the equations of motion alone. This ambiguity in the gluing of the two regions can give rise to different physical outcomes of the collapse compatible with the canonical dynamics. We discuss two such phenomena: the formation of a wormhole characterized by two distinct asymptotic regions, and the transition from a black hole to a white hole characterized by a single asymptotic region.