Based on a dataset of $(27.12\pm 0.10)\times {10}^8$ $\psi (3686)$ events collected at the BESIII experiment, the absolute branching fractions of the three dominant ${\mathrm{\Omega }}^{-}$ decays are measured to be ${\mathcal{B}}_{{\mathrm{\Omega }}^{-}\to {\mathrm{\Xi }}^0{\pi }^{-}}=(25.03\pm 0.44\pm 0.53)\%$, ${\mathcal{B}}_{{\mathrm{\Omega }}^{-}\to {\mathrm{\Xi }}^{-}{\pi }^0}=(8.43\pm 0.52\pm 0.28)\%$, and ${\mathcal{B}}_{{\mathrm{\Omega }}^{-}\to \mathrm{\Lambda }{K}^{-}}=(66.3\pm 0.8\pm 2.0)\%$, where the first and second uncertainties are statistical and systematic, respectively. The ratio between ${\mathcal{B}}_{{\mathrm{\Omega }}^{-}\to {\mathrm{\Xi }}^0{\pi }^{-}}$ and ${\mathcal{B}}_{{\mathrm{\Omega }}^{-}\to {\mathrm{\Xi }}^{-}{\pi }^0}$ is determined to be $2.97\pm 0.19\pm 0.11$, which is in good agreement with the PDG value of $2.74\pm 0.15$, but greater by more than four standard deviations than the theoretical prediction of 2 obtained from the $\mathrm{\Delta }I=1/2$ rule.

We investigate higher spin ${\mathrm{AdS}}_3$ gravity with real split forms of complex ${\mathrm{A}}_N{\mathrm{B}}_N$, ${\mathrm{C}}_N$ and ${\mathrm{D}}_N$ Lie algebras. This is done by linking $SO(1,2)$ spin multiplets with splitted root systems using Tits-Satake diagrams of real forms. Unlike $SL(N,R)$, we show that the orthogonal families have two different higher spin (HS) spectrums; vectorial and spinorial. We find amongst others that the spinorial spectrum has an isolated spin ${\mathfrak{j}}_{\mathcal{N}}$ given by $\mathcal{N}(\mathcal{N}+1)/2$ for $SO(\mathcal{N},1+\mathcal{N})$ and $\mathcal{N}(\mathcal{N}-1)/2$ for $SO(\mathcal{N},\mathcal{N})$. We implement these results into the computation of the HS partition functions in these gravity theories and identify the individual contributions of the higher spin fields; valuable to manoeuver the HS–Bañados-Teitelboim-Zanelli black hole partition function.

We provide a systematic derivation of cluster alphabets of finite types. The construction is based on a geometric realization of the generalized worldsheets by gluing and folding a pair of polygons. The cross ratios of the worldsheet $z$ variables are evolved using the $Y$-system equations. By a new gauge choice, we obtain a simpler set of cluster alphabets than the known ones.

We expand our earlier results [D. Astefanesei et al., Hairy black hole chemistry, J. High Energy Phys. 11 (2019) 043.] to investigate a general class of exact hairy black hole solutions in Einstein-Maxwell-dilaton gravity. The dilaton is endowed with a potential that originates from an electromagnetic Fayet-Iliopoulos term in $\mathcal{N}=2$ extended supergravity in four spacetime dimensions. We present the usual thermodynamics by using the counterterm method supplemented with boundary terms for a scalar field with mixed boundary conditions. We then extend our analysis by considering a dynamical cosmological constant and verify the isoperimetric inequality. We obtain a very rich phase diagram and criticality in both the canonical and grand canonical ensembles. Within string theory, the cosmological constant is related to the radius of the external sphere (of the compactification) and can be interpreted as a modulus. In this context, the existence of a critical value hints to the fact that the thermodynamic properties of black holes in lower dimensions depend on the size of the compactification.

We study the model of spherically symmetric and spatially homogeneous gravitational collapse of a minimally coupled scalar field. Our study focuses on obtaining the scalar field potential that leads to a final equilibrium state in the gravitational collapse. We demonstrate the existence of a class of scalar field solutions that can indeed result in such an end equilibrium state.

The Goroff-Sagnotti operator, corresponding to the contraction of three Weyl tensors, is the first counterterm of general relativity (GR) nonvanishing on shell. We study the classical effects of including this operator in the effective gravitational Lagrangian. The results obtained for the Goroff-Sagnotti operator are proved to hold for some higher-curvature operators that generalize it. We find solutions to those operators’ equations of motion (EM); in particular, we find the general condition for the spherically symmetric case and provide several example solutions. Concerning the EM for GR supplemented with the Goroff-Sagnotti operator, we study spherically symmetric perturbative corrections to the GR solution. In less symmetric instances, we only study the subset of solutions that solve the EM separately for GR and the Goroff-Sagnotti operator.

We explore an interesting connection between black hole shadow parameters and the acceleration bounds for radial linear uniformly accelerated (LUA) trajectories in static spherically symmetric black hole spacetime geometries of the Schwarzschild type. For an incoming radial LUA trajectory to escape back to infinity, there exists a bound on its magnitude of acceleration and the distance of closest approach from the event horizon of the black hole. We calculate these bounds and the shadow parameters, namely, the photon sphere radius and the shadow radius, explicitly for specific black hole solutions in $d$-dimensional Einstein’s theory of gravity, in pure Lovelock theory of gravity and in the $\mathcal{F}(R)$ theory of gravity. We find that for a particular boundary data, the photon sphere radius $r_{\mathrm{ph}}$ is equal to the bound on radius of closest approach $r_b$ of the incoming radial LUA trajectory while the shadow radius $r_{\mathrm{sh}}$ is equal to the inverse magnitude of the acceleration bound $|a{|}_b$ for the LUA trajectory to turn back to infinity. Using the effective potential technique, we further show that the same relations are valid in any theory of gravity for static spherically symmetric black hole geometries of the Schwarzschild type. Investigating the trajectories in a more general class of static spherically symmetric black hole spacetimes, we find that the two relations are valid separately for two different choices of boundary data.

We study the properties of the stochastic gravitational wave background (SGWB) resulting from the mergers of primordial black holes (PBH) that formed from the collapse of subhorizon regions in the early Universe. We adopt a model-independent approach, where we parametrize the fraction $f_H$ of the wavelength of the perturbation mode in units of the horizon radius when the patch starts to gravitationally collapse. Assuming a monochromatic spectrum of curvature perturbations and spherically-symmetric density perturbations, we investigate the isotropic SGWB energy density and angular power spectrum at various frequencies, PBH masses, and horizon size fractions. The key effect of subhorizon formation is a change in the PBH mass function and formation redshift, which, in turn, affects gravitational wave (GW) observables. We find that subhorizon PBH formation in general enhances the isotropic SGWB energy density and the absolute angular power spectrum. However, the quasimonotonic increases in both quantities as $f_H$ decreases cease when the chirp mass of the binary PBHs reaches a mass threshold determined by the frequency of observation; the isotropic SGWB energy density spectrum significantly drops above the corresponding cutoff frequency. We find that despite the significant enhancement from subhorizon collapse, the resulting signal in the anisotropy power spectrum will not be detectable by planned future gravitational wave detectors such as LISA.

We implement and explore high-dimensional generalized dark matter (HDGDM) with an arbitrary equation of state as a function of redshift as an extension to $\mathrm{\Lambda }$ cold dark matter. Exposing this model to cosmic microwave background, baryon acoustic oscillations, and supernova data, we demonstrate that the use of marginalized posterior distributions can easily lead to misleading conclusions on the viability of a high-dimensional model such as this one. We discuss such pitfalls and corresponding mitigation strategies, which can be used to search for an observationally favored region of the parameter space. We further show that the HDGDM model in particular does show promise in terms of its ability to ease the Hubble tension once such techniques are employed, and we find interesting features in the best-fitting equation of state that can serve as an inspiration for future model building.

We study the late-time cosmological tensions using the low-redshift background and redshift-space distortion data by employing a machine learning (ML) technique. By comparing the generated observables with the standard cosmological scenario, our findings indicate support for the phantom nature of dark energy, which ultimately leads to a reduction in the existing tensions. The model-independent approach also enables us to examine the combined background and perturbative history, where tensions are reduced. Moreover, from a statistical perspective, we have shown that our results exhibit a better fit to the data when compared to the $\mathrm{\Lambda }\mathrm{CDM}$ model.

The Hubble tension can be addressed by modifying the sound horizon ($r_s$) before recombination, triggering interest in early universe estimates of the Hubble constant, $H_0$, independent of $r_s$. Constraints on $H_0$ from an $r_s$-free analysis of the full shape BOSS galaxy power spectra within $\mathrm{\Lambda }\mathrm{CDM}$ were recently reported and used to comment on the viability of physics beyond $\mathrm{\Lambda }\mathrm{CDM}$. Here we demonstrate that $r_s$-free analyses with current data depend on both the model and the priors placed on the cosmological parameters, such that $\mathrm{\Lambda }\mathrm{CDM}$ analyses cannot be used as evidence for or against new physics. We find that beyond-$\mathrm{\Lambda }\mathrm{CDM}$ models which introduce additional energy density with significant pressure support, such as early dark energy (EDE) or additional neutrino energy density ($\mathrm{\Delta }{N}_{\mathrm{eff}}$), lead to $r_s$-free values of $H_0$ which are larger by $3–4\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$. On the other hand, models which only affect the time of recombination, such as a varying electron mass ($\mathrm{\Delta }{m}_e$), produce $H_0$ constraints similar to $\mathrm{\Lambda }\mathrm{CDM}$. Using BOSS data, constraints from light element abundances, cosmic microwave background (CMB) lensing, a CMB-based prior on the primordial scalar amplitude ($A_s$), spectral index ($n_s$), and ${\mathrm{\Omega }}_m$ from the $\mathrm{Pantheon}+\text{Type}$ Ia supernovae dataset, we find that in $\mathrm{\Lambda }\mathrm{CDM}$, $H_0=64.9\pm 2.2\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$; in EDE, $H_0={68.7}_{-3.9}^{+3}$; in $\mathrm{\Delta }{N}_{\mathrm{eff}}$, $H_0={68.1}_{-3.8}^{+2.7}$; and in $\mathrm{\Delta }{m}_e$, $H_0={64.7}_{-2.3}^{+1.9}$. Using a prior on the angular size of the sound horizon at baryon drag from BAO and CMB measurements, these values become in $\mathrm{\Lambda }\mathrm{CDM}$, $H_0=67.9\pm 1.7$; in EDE, $H_0={72.2}_{-3.8}^{+2.9}$; in $\mathrm{\Delta }{N}_{\mathrm{eff}}$, $H_0={71.5}_{-3.3}^{+2.5}$; and in $\mathrm{\Delta }{m}_e$, $H_0=68.0\pm 1.7$. With current data, none of the models are in significant tension with $\mathrm{S}{H}_0\mathrm{ES}$, and consistency tests based on comparing $H_0$ posteriors with and without $r_s$ marginalization are inconclusive with respect to the viability of beyond $\mathrm{\Lambda }\mathrm{CDM}$ models.

The stability of hybrid stars with first-order phase transitions as determined by calculating fundamental radial oscillation modes is known to differ from the predictions of the widely used Bardeen-Thorne-Meltzer criterion. We consider the effects of out-of-chemical-equilibrium physics on the radial modes and hence stability of these objects. For a barotropic equation of state, this is done by allowing the adiabatic sound speed to differ from the equilibrium sound speed. We show that doing so extends the stable branches of stellar models, allowing stars with rapid phase transitions to support stable higher-order stellar multiplets similarly to stars with multiple slow phase transitions. We also derive a new junction condition to impose on the oscillation modes at the phase transition. Termed the reactive condition, it is physically motivated, consistent with the generalized junction conditions between two phases, and has the common rapid and slow conditions as limiting cases. Unlike the two common cases, it can only be applied to nonbarotropic stars. We apply this junction condition to hybrid stellar models generated using a two-phase equation of state consisting of nuclear matter with unpaired quark matter at high densities joined by a first-order phase transition and show that, like in the slow limiting case, stars that are classically unstable are stabilized by a finite chemical reaction speed.

The recent evidence of a stochastic background of gravitational waves in the nHz band by pulsar timing array (PTA) experiments has shed new light on the formation and evolution of massive black hole binaries with masses $\sim {10}^8–{10}^9{M}_{\odot }$. The PTA data are consistent with a population of such binaries merging efficiently after the coalescence of their galactic hosts, and presenting masses slightly larger than previously expected. This momentous discovery calls for investigating the prospects of detecting the smaller ($\sim {10}^5–{10}^7{M}_{\odot }$) massive black hole binaries targeted by the Laser Interferometer Space Antenna (LISA). By using semianalytic models for the formation and evolution of massive black hole binaries calibrated against the PTA results, we find that LISA will observe at least a dozen and up to thousands of black hole binaries during its mission duration. The minimum number of detections rises to $\sim 70$ if one excludes models that only marginally reproduce the quasar luminosity function at $z=6$. We also assess LISA’s parameter estimation capabilities with state-of-the-art waveforms including higher modes and realistic instrumental response, and find that the masses, sky position, and distance will typically be estimated to within, respectively, 1%, 10 sq deg, and 10% for the detected systems (assuming a four-year mission).

Many theories that attempt to formulate a quantum description of gravity suggest the existence of a fundamental minimum length scale. A popular method for incorporating this minimum length is through a modification of the Heisenberg uncertainty principle known as the generalized uncertainty principle (GUP). Experimental tests of the GUP applied to composite systems can be performed by searching for the induced frequency perturbations of the modes of mechanical resonators, thus constraining the degree of minimum length in certain scenarios. In this work previous constraints made with mechanical resonators are improved upon by three orders of magnitude, via the utilization of a cryogenic quartz bulk acoustic wave resonator. As well as purely mechanical resonant modes, hybrid electromechanical antiresonant modes are investigated and shown to be sensitive to the same GUP induced effects.

The variational method employing the amplitude and width as collective coordinates of the Klein-Gordon oscillon leads to a dynamical system with unstable periodic orbits that blow up when perturbed. We propose a multiscale variational approach free from the blowup singularities. An essential feature of the proposed trial function is the inclusion of the third collective variable: a correction for the nonuniform phase growth. In addition to determining the parameters of the oscillon, our approach detects the onset of its instability.

Quantum field theories with purely virtual particles, or fakeons, require suitable modifications in one-loop integrals. We provide the expressions for the modified scalar integrals in the case of the bubble, triangle and box diagrams. The new functions are defined by means of their difference with the ‘t Hooft-Veltman scalar integrals. The modifications do not affect the derivation of the Passarino-Veltman reduction and one-loop integrals with nontrivial numerators can be decomposed in the same fashion. Therefore, the new functions can be directly used to study the phenomenology of any models with standard particles and fakeons. We compare our results with standard amplitudes and show that the largest differences are often localized in relatively small energy ranges and are characterized by additional nonanalyticities. Finally, we give explicit examples in the context of a toy model, where cross sections and decay widths of standard particles are modified by the presence of fakeons.

We derive a linearly causal and stable third-order relativistic fluid-dynamical theory from the Boltzmann equation using the method of moments. For this purpose, we demonstrate that such a theory must include novel degrees of freedom, corresponding to irreducible tensors of ranks 3 and 4. The equations of motion derived in this work are compared with numerical solutions of the Boltzmann equation, considering an ultrarelativistic, classical gas in the highly symmetric Bjorken flow scenario. These solutions are shown to be in good agreement for a wide range of values of shear viscosity and initial temperatures.

The properties of the pion quasiparticle in hot and dense isospin medium, including the screening mass, pole mass, and thermal width, as well as their relationships with the pion superfluid phase transition, are investigated in the framework of two-flavor ($N_f=2$) soft-wall $\mathrm{AdS}/\mathrm{QCD}$ models. We extract the screening mass of the pion from the pole of the spatial two-point retarded correlation function. The screening masses of both neutral and charged pions increase monotonously with the increasing of temperature. However, the isospin chemical potential ${\mu }_I$ would depress the screening masses of the charged pions, $m_{{\pi }^{\pm },\mathrm{scr}}$. With the increasing of ${\mu }_I$, $m_{{\pi }^{\pm },\mathrm{scr}}$ monotonically decrease to zero on the boundary between the normal phase and the pion superfluid phase, while the screening mass of the neutral pion, $m_{{\pi }^0,\mathrm{scr}}$, remains almost unchanged. We also extracted the pole mass $m_{\mathrm{pole}}$ and thermal width $\mathrm{\Gamma }$ of the pion from the pole of temporal two-point retarded correlation function, i.e., the corresponding quasinormal frequencies, $\omega =m_{\mathrm{pole}}-i\mathrm{\Gamma }/2$. The pole masses of the three modes (${\pi }^0,{\pi }^{+},{\pi }^{-}$) are splitting at finite ${\mu }_I$. The thermal widths of the three modes increase with temperature. Furthermore, the pole mass and thermal width of ${\pi }^{+}$ decrease almost monotonically with the increasing of ${\mu }_I$, reaching zero at ${\mu }_I={\mu }_I^c$, simultaneously. It indicates that ${\pi }^{+}$ becomes a massless Goldstone boson as a result of the pion superfluid phase transition.

Many components of data analysis in high-energy physics and beyond require morphing one dataset into another. This is commonly solved via reweighting, but there are advantages of preserving weights and shifting the data points instead. Normalizing flows are machine learning models that have shown impressive precision on a variety of particle physics tasks. Naively, normalizing flows cannot be used for morphing because they require knowledge of the probability density of the starting dataset; in most cases in particle physics, we can generate more examples, but we do not know densities explicitly. We propose a protocol called flows for flows for training normalizing flows to morph one dataset into another even if the underlying probability density of neither dataset is known explicitly. This enables a morphing strategy trained with maximum likelihood estimation, a setup that has been shown to be highly effective in related tasks. We study variations on this protocol to explore how far the data points are moved to statistically match the two datasets. Furthermore, we show how to condition the learned flows on particular features in order to create a morphing function for every value of the conditioning feature. For illustration, we demonstrate flows for flows on toy examples as well as a collider physics example involving dijet events.

Evidence for a stochastic gravitational wave background in the nHz frequency band is recently reported by four pulsar timing array collaborations NANOGrav, EPTA, CPTA, and PPTA. It can be interpreted by gravitational waves from collapsing domain walls in the early universe. We assume such domain walls arising from the spontaneous breaking of a $Z_2$ symmetry in a scalar field theory, where a tiny $Z_2$-violating potential is required to make domain walls unstable. We propose that this $Z_2$-violating potential is radiatively induced by a feeble Yukawa coupling between the scalar field and a fermion field, which is also responsible for dark matter production via the freeze-in mechanism. Combining the pulsar timing array data and the observed dark matter relic density, we find that the model parameters can be narrowed down to small ranges.