The equation of state of the quark gluon plasma is a key ingredient of heavy-ion phenomenology. In addition to the traditional Taylor method, several novel approximation schemes have been proposed with the aim of calculating it at finite baryon density. In order to gain a pragmatic understanding of the limits of these schemes, we compare them to direct results at ${\mu }_B>0$, using reweighting techniques free from an overlap problem. We use 2stout improved staggered fermions with eight time slices and cover the entire Relativistic Heavy Ion Collider Beam Energy Scan range in the baryochemical potential, up to ${\mu }_B/T=3$.

We measure the $B^0$ lifetime and flavor-oscillation frequency using $B^0\to D^{(*)-}{\pi }^{+}$ decays collected by the Belle II experiment in asymmetric-energy $e^{+}{e}^{-}$ collisions produced by the SuperKEKB collider operating at the $\mathrm{\Upsilon }(4\mathrm{S})$ resonance. We fit the decay-time distribution of signal decays, where the initial flavor is determined by identifying the flavor of the other $B$ meson in the event. The results, based on 33000 signal decays reconstructed in a data sample corresponding to $190{\mathrm{fb}}^{-1}$, are ${\tau }_{B^0}=(1.499\pm 0.013\pm 0.008)\mathrm{ps}$, $\mathrm{\Delta }{m}_d=(0.516\pm 0.008\pm 0.005){\mathrm{ps}}^{-1}$, where the first uncertainties are statistical and the second are systematic. These results are consistent with the world-average values.

Using a data sample collected with the BESIII detector operating at the BEPCII storage ring, the Born cross section of the process $e^{+}{e}^{-}\to \eta J/\psi$ at a center-of-mass energy $\sqrt{s}=3.773\mathrm{GeV}$ is measured to be $(8.88\pm 0.87\pm 0.42)\mathrm{pb}$. We fit the cross section line shape before correcting for the initial state radiation from $\sqrt{s}=3.773$ to 4.600 GeV to obtain the branching fraction $\mathcal{B}(\psi (3770)\to \eta J/\psi )$. We obtain $\mathcal{B}(\psi (3770)\to \eta J/\psi )=(11.3\pm 5.9\pm 1.1)\times {10}^{-4}$ when the $\psi (3770)$ decay amplitude is added coherently to the other contributions, and $(8.7\pm 1.0\pm 0.8)\times {10}^{-4}$ when it is added incoherently. Here the quoted uncertainties are statistical and systematic, respectively. In both cases, the statistical significance of $\psi (3770)$ resonance is above $7\sigma$. This is the first time the decay $\psi (3770)\to \eta J/\psi$ is observed with a statistical significance greater than $5\sigma$.

The problem of ordering operators has afflicted quantum mechanics since its foundation. Several orderings have been devised, but a systematic procedure to move from one ordering to another is still missing. The importance of establishing relations among different orderings is demonstrated by Wick’s theorem (which relates time ordering to normal ordering), which played a crucial role in the development of quantum field theory. We prove the general ordering theorem (GOT), which establishes a relation among any pair of orderings, that act on operators satisfying generic (i.e., operatorial) commutation relations. We expose the working principles of the GOT by simple examples, and we demonstrate its potential by recovering two famous algebraic theorems as special instances: the Magnus expansion and the Baker-Campbell-Hausdorff formula. Remarkably, the GOT establishes a formal relation between these two theorems, and it provides compact expressions for them, unlike the notoriously complicated ones currently known.

Analog models of black holes have unequivocally proven to be extremely beneficial in providing critical information regarding black hole spectroscopy, superradiance, quantum phenomena and most importantly Hawking radiation and black hole evaporation; topics that have either recently begun to bloom through gravitational wave observations or have not yet been investigated in astrophysical setups. Black hole analog experiments have made astonishing steps toward the aforementioned directions and are paramount in understanding the quantum nature of the gravitational field. Recently, a tabletop analog Schwarzschild black hole has been proposed by placing Bose-Einstein condensates of photons inside a mirror’s cavity, leading to a sink with a radial vortex that represents a velocity singularity. Here, we provide an extensive spectral analysis of both the tabletop acoustic black hole and its higher-dimensional gravitational analog. We find that quasinormal modes and quasibound states share qualitative similarities in both systems and show that the eikonal quasinormal modes of the analog acoustic black hole have a photon-spherelike interpretation, which points to the existence of a phonon sphere in the analog black hole. Our results, complemented with the recently calculated graybody factors and Hawking radiation of the acoustic analog, can provide a theoretical test bed for future tabletop experiments with condensates of light in a mirror’s cavity and provide significant insights regarding classical and quantum phenomena in higher-dimensional black holes.

Various groups recently argued that self-interacting vector field theories lack a well-defined time evolution when the field grows to large amplitudes, which has drastic consequences for models in gravity and high energy theory. Such field amplitudes can be a result of an external driving mechanism, or occur intrinsically, due to large values of the field and its derivatives in the initial data. This brings a natural question: Is small amplitude initial data guaranteed to evolve indefinitely in these theories in the absence of an outside driving term? We answer this question in the negative, demonstrating that arbitrarily low amplitude initial data can still lead to the breakdown of the theory. Namely, ingoing spherically symmetric wave packets in more than one spatial dimensions grow as an inverse power of the radius, and their amplitudes can generically reach high enough values where time evolution ceases to exist. This simple example further establishes the pervasiveness of the pathology of self-interacting vector field theories.

We present a simple formula for the effective ringdown frequencies of the gravitational-wave signal of a precessing black-hole binary in the coprecessing frame. This formula requires only knowledge of the quasi-normal mode frequencies of the system and the value of the precession angle $\beta$ during ringdown. Such a formula will be useful in modeling precessing systems. We also provide a comprehensive description of the oscillations in the ringdown frequency in an inertial frame where the spin of the final black hole is in the $z$-direction. These oscillations arise due to the superposition of the prograde and retrograde frequencies. Our understanding of these oscillations can be used to extract the ratio of the amplitudes of the prograde and retrograde frequencies from numerical data. Alternatively, knowledge of this ratio of the amplitudes can be used to produce a simple model of the time-domain oscillations in the ringdown frequency.

We provide a uniform treatment of electromagnetic and gravitational memory effects, based on the gravitoelectromagnetic formulation of general relativity (GR) and a generalization of the geodesic deviation equation. This allows us to find novel results: in gauge theory, we derive relativistic corrections to the well-known kick memory observable, and a general expression for the displacement memory observable, typically overlooked in the literature. In GR, we find relativistic corrections to displacement and kick memory observables. In both theories, we find novel radial memory effects. Next, we show that electromagnetic and gravitational memory observables can be formulated in terms of certain holonomies on a holographic screen in asymptotically flat spacetimes. In gauge theory, the displacement and kick memory effects form a Hamiltonian vector field, which is canonically generated by a Wilson loop. In the first order formulation of GR, we show that the holonomy naturally splits into translational and Lorentz parts. While the former encodes the leading and subleading displacement and kick memory observables, the latter reproduces the gyroscopic memory effect.

We develop a numerical approach to find asymptotically flat black hole solutions coupled to anisotropic fluids, described by generic density profiles. Our model allows for a variety of applications in realistic astrophysical scenarios, and is potentially able to describe the geometry of galaxies hosting supermassive black holes, dark matter environments, and accretion phenomena. We apply our framework to a black hole surrounded by different families of dark matter profiles, namely the Hernquist, the Navarro-Frenk White, and the Einasto models. We study the geodesic motion of light and of massive particles in such spacetimes. Moreover we compute gravitational axial perturbations induced by a small secondary on the numerical background and determine the changes in the emitted gravitational wave fluxes compared to the vacuum case. Our analysis confirms and extends previous studies showing that modifications of orbital frequencies and axial fluxes can be described in terms of gravitational redshift, regardless of the halo model.

The well-known shear viscosity to entropy density ratio ($\eta /s$) cannot be computed when the black hole space-time has zero thermodynamic entropy. This is the case, for example, when general relativity in four dimensions is complemented with critical gravity, or in particular scenarios within the four-dimensional scalar Gauss-Bonnet theories. Recently, it has been shown that the zero-entropy situation can be overcome in these examples by introducing suitable matter fields. With this at hand, in this paper we analyze each case and the impact of these extra sources in the ratio, in terms of their new parameters. We find that while the $\eta /s$ ratio remains constant and insensitive in the former, this is not the case for the latter. To perform the calculations, we construct a Noether charge using a spacelike Killing vector. The accuracy of the aforementioned findings is supported by the Kubo formalism.

Reionization of helium is expected to occur at redshifts $z\sim 3$ and have important consequences for quasar populations, galaxy formation, and the morphology of the intergalactic medium, but there is little known empirically about the process. Here we show that kinetic Sunyaev-Zel’dovich tomography, based on the combination of cosmic microwave background (CMB) measurements and galaxy surveys, can be used to infer the primordial helium abundance as well as the time and duration of helium reionization. We find a high-significance detection at $\sim 10\sigma$ can be expected from Vera Rubin Observatory and CMB-S4 in the near future. A more robust characterization of helium reionization will require next-generation experiments like MegaMapper (a proposed successor to the Dark Energy Spectroscopic Instrument) and CMB-HD.

Axions are considered as a potential candidate of dark matter. The axions form coherent clouds, which can delay and amplify gravitational waves (GWs) at a resonant frequency and produce secondary GWs following a primary wave. All GWs detected so far from compact binary mergers propagate in the Milky Way halo, which is composed of axion dark matter clouds, resulting in the production of the secondary GWs. The properties of these secondary GWs depend on the axion mass and its coupling with the parity-violating sector of gravity. In our previous study, we have developed a search method optimized for the axion signals and obtained a constraint on the coupling that was approximately ten times stronger than the previous best constraint for the axion mass range, $[1.7\times {10}^{-13},8.5\times {10}^{-12}]\mathrm{eV}$. However, the previous search assumed that dark matter was homogeneously distributed in the Milky Way halo, which is not realistic. In this paper, we extend the dark matter profile to a more realistic one called the core Navarro-Frenk-White (NFW) profile. The results show that the previous study’s constraint on the axion coupling is robust to the dark matter profile.

Thermal friction offers a promising solution to the Hubble and the large-scale structure (LSS) tensions. This additional friction acts on a scalar field in the early universe and extracts its energy density into dark radiation, the cumulative effect being similar to that of an early dark energy (EDE) scenario. The dark radiation automatically redshifts at the minimal necessary rate to improve the Hubble tension. On the other hand, the addition of extra radiation to the Universe can mitigate the LSS tension. We explore this model in light of cosmic microwave background (CMB), baryon acoustic oscillation, and type Ia supernova data, including the SH0ES $H_0$ measurement and the Dark Energy Survey Y1 data release in our analysis. Our results indicate a preference for the regime where the scalar field converts to dark radiation at very high redshifts ($z\gtrsim {10}^5$), asymptoting effectively to an extra self-interacting radiation species rather than an EDE-like injection. In this limit, thermal friction can ease both the Hubble and the LSS tensions, but not resolve them. We find the source of this preference to be the incompatibility of the CMB data with the linear density perturbations of the dark radiation when injected at redshifts close to matter-radiation equality.

Ultrahigh-energy (UHE) cosmic rays (CRs) from distant sources interact with intergalactic radiation fields, leading to their spallation and attenuation. They are also deflected in intergalactic magnetic fields (IGMFs), particularly those associated with megaparsec-scale structures. These deflections extend the propagation times of CR particles, forming a magnetic horizon for each CR species. The cumulative cooling and interactions of a CR ensemble also modifies their spectral shape and composition observed on Earth. We construct a transport formulation to calculate the observed UHE CR spectral composition for four classes of source population. The effects on CR propagation brought about by IGMFs are modeled as scattering processes during transport, by centers associated with cosmic filaments. Our calculations demonstrate that IGMFs can have a marked effect on observed UHE CRs and that source population models are degenerate with IGMF properties. Interpretation of observations, including the endorsement or rejection of any particular source classes, thus needs careful consideration of the structural properties and evolution of IGMFs. Future observations providing tighter constraints on IGMF properties will significantly improve confidence in assessing UHE CR sources and their intrinsic CR production properties.

A likely source of a gravitational-wave background (GWB) in the frequency band of the Advanced LIGO, Virgo, and KAGRA detectors is the superposition of signals from the population of unresolvable stellar-mass binary-black-hole (BBH) mergers throughout the Universe. Since the duration of a BBH merger in band ($\sim 1\mathrm{s}$) is much shorter than the expected separation between neighboring mergers ($\sim {10}^3\mathrm{s}$), the observed signal will be “popcornlike” or intermittent with duty cycles of order ${10}^{-3}$. However, the standard cross-correlation search for stochastic GWBs currently performed by the LIGO-Virgo-KAGRA Collaboration is based on a continuous-Gaussian signal model, which does not take into account the intermittent nature of the background. The latter is better described by a Gaussian mixture model, which includes a duty cycle parameter that quantifies the degree of intermittence. Building on an earlier paper by Drasco and Flanagan [Detection methods for non-gaussian gravitational wave stochastic backgrounds, Phys. Rev. D 67, 082003 (2003).], we propose a stochastic-signal-based search for intermittent GWBs. For such signals, this search performs better than the standard continuous cross-correlation search. We present results of our stochastic-signal-based approach for intermittent GWBs applied to simulated data for some simple models, and we compare its performance to the other search methods, in terms of both detection and signal characterization. Additional testing on more realistic simulated datasets, e.g., consisting of astrophysically motivated BBH merger signals injected into colored detector noise containing noise transients, will be needed before this method can be applied with confidence on real gravitational-wave data.

We perform multidimensional core-collapse supernova (CCSN) simulations in a massive scalar-tensor theory for the first time with a realistic equation of state and multienergy neutrino radiation. Among the set of our models varying the scalar mass and the coupling strength between the scalar and gravitational fields, a particular model allows for recurrent spontaneous scalarizations (SSs) in the protoneutron star (PNS). Each SS induces the PNS collapse and subsequent bounce, from which devastating shock waves emanate and eject the PNS envelope. The explosion energy can easily exceed $\mathcal{O}({10}^{51})\mathrm{erg}$. This study reveals new aspects of SS as the explosion mechanism of CCSNe. We also discuss its characteristic multimessenger signals: neutrinos and gravitational waves.

The dense environment of neutron stars makes them an excellent target for probing dark matter interactions with the Standard Model. We study neutron star heating from capture of inelastic dark matter, which can evade direct detection constraints. We investigate kinematics of the inelastic scattering process between quasirelativistic dark matter particles and ultrarelativistic targets in neutron stars, and derive analytical expressions for the maximal mass gap allowed for the scattering to occur. We implement them into a fully relativistic formalism for calculating the capture rate and apply it to various scenarios of inelastic dark matter. The projected constraints from neutron stars can systematically surpass those from terrestrial searches, including direct detection and collider experiments. Neutron stars can also be sensitive to the parameter space of inelastic self-interacting dark matter. Our results indicate that extreme astrophysical environments, such as neutron stars, are an important target for searching dark matter.

We present a radically new proposal for the solution of the naturalness/hierarchy problem, where the fine-tuning of the Higgs mass finds its physical explanation and the well-known multiplicative renormalization of the usual perturbative approach emerges as an IR property of the nonperturbative running of the mass.

We study the online detection of gallium capture of monoenergetic neutrinos produced by a ${}^{51}\mathrm{Cr}$ radioactive source in a scintillation experiment. We find that cerium-doped gadolinium aluminum gallium garnet (Ce:GAGG) is a suitable scintillator which contains about 21% of gallium per weight and has a high mass density and light yield. Combined with a highly efficient light detection system this allows tagging of the subsequent germanium decay and thus a clean distinction of gallium capture and elastic neutrino electron scattering events. With 1.5 tons of scintillator and 10 source runs of 3.4 MCi, each, we obtain about 1700 gallium capture events with a purity of 90% and 680,000 neutrino electron scattering events, where the latter provide a precise normalization independent of any nuclear physics. We include a detailed discussion of backgrounds and find that this configuration would allow us to test the gallium anomaly at more than $5\sigma$ in an independent way.

We have derived the solutions of the relativistic anomalous magnetohydrodynamics with longitudinal Bjorken boost invariance and transverse electromagnetic fields in the presence of temperature or energy density dependent electric conductivity. We consider the equations of states in a high temperature limit or in a high chiral chemical potential limit. We obtain both perturbative analytic solutions up to the order of $\hslash$ and numerical solutions in our configurations of initial electromagnetic fields and Bjorken flow velocity. Our results show that the temperature or energy density dependent electric conductivity play an important role to the decaying of the energy density and electromagnetic fields. We also implement our results to the splitting of global polarization for $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ hyperons induced by the magnetic fields. Our results for the splitting of global polarization disagree with the experimental data in low energy collisions, which implies that the contribution from electromagnetic fields may be insufficient to explain the global polarization of $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ hyperons in the low energy collisions.