We report the first measurement of the $Q^2$ distribution of $X(3915)$ produced by single-tag two-photon interactions. The decay mode used is $X(3915)\to J/\psi \omega$. The covered $Q^2$ region is from $1.5(\mathrm{GeV}/c{)}^2$ to $10.0(\mathrm{GeV}/c{)}^2$. We observe $7.9\pm 3.1(\mathrm{stat})\pm 1.5(\mathrm{syst})$ events, where we expect $4.1\pm 0.7$ events based on the $Q^2=0$ result from the no-tag two-photon process, extrapolated to higher $Q^2$ region using the $c\overline{c}$ model of Schuler, Berends, and van Gulik. The shape of the distribution is also consistent with this model; we note that statistical uncertainties are large.

We present the first measurement of the Michel parameter ${\xi }^{\prime }$ in the ${\tau }^{-}\to {\mu }^{-}{\overline{\nu }}_{\mu }{\nu }_{\tau }$ decay using the full data sample of $988{\mathrm{fb}}^{-1}$ collected by the Belle detector operating at the KEKB asymmetric energy $e^{+}{e}^{-}$ collider. The method is based on the reconstruction of the ${\mu }^{-}\to e^{-}{\overline{\nu }}_e{\nu }_{\mu }$ decay-in-flight in the Belle central drift chamber and relies on the correlation between muon spin and its daughter electron momentum. We study the main sources of the background that can imitate the signal decay, such as kaon and pion decays-in-flight and charged particle scattering on the detector material. Highly efficient methods of their suppression are developed and applied to select 165 signal-candidate events. We obtain ${\xi }^{\prime }=0.22\pm 0.94\pm 0.42$ where the first uncertainty is statistical, and the second one is systematic. The result is in agreement with the Standard Model prediction of ${\xi }^{\prime }=1$.

It has been recently pointed out that nonlinear effects are necessary to model the ringdown stage of the gravitational waveform produced by the merger of two black holes giving rise to a remnant Kerr black hole. We show that this nonlinear behavior is explained, both on the qualitative and quantitative level, by near-horizon symmetries of the Kerr black hole within the Kerr/CFT correspondence.

In the framework of the static patch approach to de Sitter holography introduced in [L. Susskind, J. Hologr. Appl. Phys. 1, 1 (2021)], the growth of holographic complexity has a hyperfast behavior, which leads to a divergence in a finite time. This is very different from the anti–de Sitter (AdS) spacetime, where instead the complexity rate asymptotically reaches a constant value. We study holographic volume complexity in a class of asymptotically AdS geometries which include de Sitter bubbles in their interior. With the exception of the static bubble case, the complexity obtained from the volume of the smooth extremal surfaces which are anchored just to the AdS boundary has a similar behavior to the AdS case, because it asymptotically grows linearly with time. The static bubble configuration has a zero complexity rate and corresponds to a discontinuous behavior, which resembles a first order phase transition. If instead we consider extremal surfaces which are anchored at both the AdS boundary and the de Sitter stretched horizon, we find that complexity growth is hyperfast, as in the de Sitter case.

We investigate two types of excited oscillons. We first focus on spherical symmetry and find that there are a tower of spherical oscillons with higher energies. Despite having multiple approximate “nodes” in their energy density profiles, these oscillons are long-lived. We find that during the lifetime of an excited oscillon it will cascade down all of the lower energy levels before its disintegration, with each level-dropping period accompanied by a short burst of energy. We also point out the existence of excited oscillons with higher approximate multipoles, which generally have shorter lifespans than the spherical ones. Apart from performing nonlinear simulations with absorbing boundary conditions, we also apply a perturbative method to analyze some features of these excited oscillons.

We calculate the 2 post-Newtonian correction to the radiation reaction acceleration for nonspinning binary systems, which amounts to the 4.5 post-Newtonian correction to Newtonian acceleration. The calculation is carried out completely using the effective field theory approach. The center-of-mass corrections to the results are complicated and are discussed in detail. Nontrivial consistency checks are performed and we compare with corresponding results in the literature. Analytic results are supplied in the Supplemental Material.

Cooling processes of brown dwarf stars and giant planets are studied in the framework of degenerate higher-order scalar-tensor theories. We confirm the previous results in the field that the effect of modified gravity on substellar objects’ age is pronounced the most.

We construct scalarized planar charged black holes in Einstein-Maxwell-scalar (EMS) theory with the presence of a negative cosmological constant. Domains of existence of black hole solutions are given in term of nonminimally coupling constant $\alpha$. Perturbative stability of a scalarized black hole is investigated by calculating its quasinormal modes. Thermodynamic properties of the scalarized planar solution are also discussed. We observe no evidence of instability of the scalarized black holes. Moreover, we find that scalarized planar charged AdS black holes are thermodynamically preferred over scalar-free solutions in grand canonical and canonical ensembles. The transition between scalar-free solutions and scalarized solutions is found to be the thermal second order phase transition. The transition of these solutions shares some similar features with conductor-superconductor phase transition.

In the framework of scalar-Einstein-Gauss-Bonnet gravity, we construct the Hayward black hole model and discuss the absence of ghosts in this model. Because a Hayward black hole has two horizons but no curvature singularity, it may solve the problem of the information loss that might be generated by black holes. The Gauss-Bonnet term appears as a stringy correction, and therefore, our results might indicate that the stringy correction would solve the information loss problem.

Close hyperbolic encounters of black holes (BHs) generate certain burst with memory (BWM) events in the frequency windows of the operational, planned, and proposed gravitational wave (GW) observatories. We present detailed explorations of the detectable parameter space of such events that are relevant for the LIGO-Virgo-KAGRA and the International Pulsar Timing Array (IPTA) consortia. The underlying temporally evolving GW polarization states are adapted from Cho et al. [Phys. Rev. D 98, 024039 (2018)] and therefore incorporate general relativistic effects up to the third post-Newtonian order. Further, we provide a prescription to ensure the validity of our waveform family while describing close encounters. Preliminary investigations reveal that optimally placed BWM events should be visible to megaparsec distances for the existing ground-based observatories. In contrast, maturing IPTA datasets should be able to provide constraints on the occurrences of such hyperbolic encounters of supermassive BHs to gigaparsec distances.

Probabilities in eternal inflation are traditionally defined as limiting frequency distributions, but a unique and unambiguous probability measure remains elusive. In this paper, we present a different approach, based on Bayesian reasoning. Our starting point is the master equation governing vacuum dynamics, which describes a random walk on the network of vacua. Our probabilities require two pieces of prior information, both pertaining to initial conditions; a prior density $\rho (t)$ for the time of nucleation, and a prior probability $p_{\alpha }$ for the ancestral vacuum. For ancestral vacua, we advocate the uniform prior as a conservative choice, though our conclusions are fairly insensitive to this choice. For the time of nucleation, we argue that a uniform prior is consistent with the time-translational invariance of the master equation and represents the minimally informative choice. The resulting predictive probabilities coincide with Bousso’s “holographic” prior probabilities and are closely related to Garriga and Vilenkin’s “comoving” probabilities. Despite making the least informative priors, these probabilities are surprisingly predictive. They favor vacua whose surrounding landscape topography is that of a deep funnel, akin to the folding funnels of naturally occurring proteins. They predict that we exist during the approach to near-equilibrium, much earlier than the mixing time for the landscape. We also consider a volume-weighted $\rho (t)$, which amounts to weighing vacua by physical volume. The predictive probabilities in this case coincide with the GSVW measure. The Bayesian framework allows us to compare the plausibility of the uniform-time and volume-weighted hypotheses to explain our data by computing the Bayesian evidence for each. We argue, under general and plausible assumptions, that posterior odds overwhelmingly favor the uniform-time hypothesis.

We show that literature results claimed for the magnetic field dependence of the longitudinal conductivity in anomalous first-order hydrodynamics are frame dependent at this derivative order. In particular, we focus on ($3+1$)-dimensional hydrodynamics in the presence of a constant $\mathcal{O}(\partial )$ magnetic field with a $U(1)$ chiral anomaly and demonstrate that, for constitutive relations up to and including order one in derivatives, the anomaly drops out of the longitudinal conductivity. In particular, magnetic field dependent terms that were previously found in the literature only enter the nonzero frequency thermoelectric conductivities through explicitly frame dependent pieces indicating that they are not physical. This issue can be avoided entirely by incorporating the magnetic field into the fluid’s equilibrium state.

We discuss a simple model, based on the gauge group $\mathrm{SU}(3{)}_C\otimes \mathrm{SU}(2{)}_L\otimes \mathrm{U}(1{)}_Y\otimes \mathrm{U}(1{)}_R$, where the Nelson-Barr solution to the strong $CP$ problem is implemented. This model automatically provides a high quality solution to the strong $CP$ puzzle. Weak $CP$ violation in the lepton sector arises in the same fashion as in the quark sector. We derive explicit expressions for the flavor changing couplings of the electroweak and Higgs bosons. These expressions are more general than the particular model considered. Constraints from finite naturalness are briefly discussed. We also briefly discuss related models based on the gauge group B-L.

We describe the formal analogies in the description of the inclusive production in hard processes of hadron pairs (based on dihadron fragmentation functions) and of a single hadron inside a jet (based on hadron-in-jet fragmentation functions). Since several observables involving dihadron fragmentation functions have been proposed in the past, we are able to suggest new interesting observables involving hadron-in-jet fragmentation functions, in lepton-hadron deep-inelastic scattering and hadronic collisions.

The ${\mathrm{\Xi }}^0$ asymmetry parameters are measured using entangled quantum ${\mathrm{\Xi }}^0-{\overline{\mathrm{\Xi }}}^0$ pairs from a sample of $(448.1\pm 2.9)\times {10}^6\psi (3686)$ events collected with the BESIII detector at BEPCII. The relative phase between the transition amplitudes of the ${\mathrm{\Xi }}^0{\overline{\mathrm{\Xi }}}^0$ helicity states is measured to be $\mathrm{\Delta }\mathrm{\Phi }=-0.050\pm 0.150\pm 0.020\mathrm{rad}$, which implies that there is no obvious polarization at the current level of statistics. The decay parameters of the ${\mathrm{\Xi }}^0$ hyperon $({\alpha }_{{\mathrm{\Xi }}^0},{\alpha }_{{\overline{\mathrm{\Xi }}}^0},{\varphi }_{{\mathrm{\Xi }}^0},{\varphi }_{{\overline{\mathrm{\Xi }}}^0})$ and the angular distribution parameter $[{\alpha }_{\psi (3686)}]$ and $\mathrm{\Delta }\mathrm{\Phi }$ are measured simultaneously for the first time. In addition, the $CP$ asymmetry observables are determined to be $A_{CP}^{{\mathrm{\Xi }}^0}=({\alpha }_{{\mathrm{\Xi }}^0}+{\alpha }_{{\overline{\mathrm{\Xi }}}^0})/({\alpha }_{{\mathrm{\Xi }}^0}-{\alpha }_{{\overline{\mathrm{\Xi }}}^0})=-0.007\pm 0.082\pm 0.025$ and $\mathrm{\Delta }{\varphi }_{CP}^{{\mathrm{\Xi }}^0}=({\varphi }_{{\mathrm{\Xi }}^0}+{\varphi }_{{\overline{\mathrm{\Xi }}}^0})/2=-0.079\pm 0.082\pm 0.010\mathrm{rad}$, which are consistent with $CP$ conservation.

We study quantum effects in higher curvature extensions of general relativity using the functional renormalization group. New flow equations are derived for general classes of models involving Ricci scalar, Ricci tensor, and Riemann tensor interactions. Our method is applied to test the asymptotic safety conjecture for quantum gravity with polynomial Riemann tensor interactions of the form $\sim \int \sqrt{g}(R_{\mu \nu \sigma \tau }{R}^{\mu \nu \sigma \tau }{)}^n$ and $\sim \int \sqrt{g}R·(R_{\mu \nu \sigma \tau }{R}^{\mu \nu \sigma \tau }{)}^n$, and functions thereof. Interacting fixed points, universal scaling dimensions, gaps in eigenvalue spectra, quantum equations of motion, and de Sitter solutions are identified by combining high order polynomial approximations, Padé resummations, and full numerical integration. Most notably, we discover that quantum-induced shifts of scaling dimensions can lead to a four-dimensional ultraviolet critical surface. Increasingly higher-dimensional interactions remain irrelevant and show near-Gaussian scaling and signatures of weak coupling. Moreover, a new equal weight condition is put forward to identify stable eigenvectors to all orders in the expansion. Similarities and differences with results from the Einstein-Hilbert approximation, $f(R)$ approximations, and $f(R,{\text{Ric}}^2)$ models are highlighted and the relevance of findings for quantum gravity and the asymptotic safety conjecture is discussed.

General covariant unimodular gravity frameworks, based on the Henneaux-Teitelboim formulation, are, in disguise, precisely 4-form field theories corrected with higher dimension operators. In the presence of charged tensional membranes, any de Sitter space in all such theories is unstable and decays. If the fluxes sourced by membranes are mutually incommensurate, de Sitter geometries comprise a very refined discretuum of states. Whenever the 4-form sector is dominated by terms linear in flux the almost-Minkowski space is the unique long-time attractor. As a result, a tiny cosmological constant is natural in all such frameworks, without appealing to anthropic reasoning.

We show that, for the purpose of quantum communication via a quantum field, it is essential to view the field not only as a medium for transmission but also as a source of entanglement that can aid in the communication task. To this end, we consider the quantum communication scenario where Alice is initially entangled with an ancilla and intends to communicate with Bob through a quantum field, so as to make Bob entangled with the ancilla. We find that if Alice and Bob communicate by directly coupling to the quantum field, then they can generate negativity between Bob and the ancilla only at orders that are higher than second perturbative order. We then present a protocol based on quantum teleportation in which Alice and Bob consume entanglement that they obtained from the field via interaction or harvesting. We show that this protocol can transfer negativity already to second perturbative order.

We investigate the cosmological applications of new gravitational scalar-tensor theories, and we analyze them in the light of $H_0$ tension. In these theories, the Lagrangian contains the Ricci scalar and its first and second derivatives in a specific combination that makes them free of ghosts, thus corresponding to healthy biscalar extensions of general relativity. We examine two specific models, and for particular choices of the model parameters, we find that the effect of the additional terms is negligible at high redshifts, obtaining a coincidence with $\mathrm{\Lambda }\mathrm{CDM}$ cosmology; however, as time passes, the deviation increases, and thus, at low redshifts the Hubble parameter acquires increased values ($H_0\approx 74\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$) in a controlled way. The mechanism behind this behavior is the fact that the effective dark-energy equation-of-state parameter exhibits phantom behavior, which implies faster expansion, which is one of the sufficient conditions that are capable of alleviating the $H_0$ tension. Lastly, we confront the models with cosmic chronometer (CC) data, showing full agreement within $1\sigma$ confidence level.

We theoretically investigate the feasibility of applying spin squeezing to a light pulse atom interferometer in the presence of large momentum transfer using off resonant Raman transitions, in order to enhance the sensitivity of accelerometry close to the Heisenberg limit. We also show how to implement this scheme in a dual-species atom interferometer for a precision test of the equivalence principle by measuring the Eötvös parameter, and to identify the spin squeezing protocol that is best suited for such an experiment. For a space borne platform in low Earth orbit, such a scheme may eventually enable the measurement of the Eötvös parameter with a sensitivity of the order of ${10}^{-20}$ within 150 days when ${10}^5$ atoms are employed in each cycle of the experiment.