Inspired by the first observation of a vector charmoniumlike state $Y(4626)$ decaying to a meson pair $D_s^{+}{D}_{s1}(2536{)}^{-}$, which could be viewed as a $P$-wave scalar-scalar $[cs][\overline{c}\overline{s}]$ tetraquark state, we predict a potential vector charmoniumlike state $Y$ with a $P$-wave scalar-scalar $[cq][\overline{c}\overline{q}]$ configuration. The corresponding mass spectrum of the $Y$ state is calculated to be ${4.33}_{-0.23}^{+0.16}\mathrm{GeV}$ in the framework of QCD sum rules. We suggest that the predicted $Y$ state could be looked for in an open-charm $e^{+}{e}^{-}\to \overline{D}{D}_1(2420)+c.c.$ process.

Semiclassical physics in the gravitational scenario, in its first approximation (first order), cares only for the expectation value of the stress energy tensor and ignores the inherent quantum fluctuations thereof. In the approach of stochastic gravity, on the other hand, these matter fluctuations are supposed to work as the source of geometry fluctuations and have the potential to render the results from first-order semiclassical physics irrelevant. We study the object of central significance in stochastic gravity, i.e., the noise kernel, for a wide class of Friedmann spacetimes. Through an equivalence of quantum fields on de Sitter spacetime and those on generic Friedmann universes, we obtain the noise kernel through the correlators of stress energy tensor for fixed comoving but large physical distances. We show that in many Friedmann universes including the expanding universes, the initial quantum fluctuations the universe is born with may remain invariant and important even at late times. Furthermore, we explore the cosmological spacetimes where even after long times the quantum fluctuations remain strong and become dominant over large physical distances, which the matter-driven universe is an example of. The study is carried out in minimal as well as nonminimal interaction settings. Implications of such quantum fluctuations are discussed.

Within the low-energy effective field theories of quantum electrodynamics and gravity, the low-energy speed of light or that of gravitational waves can typically be mildly superluminal in curved spacetimes. Related to this, small scattering time advances relative to the curved background can emerge from known effective field theory coefficients for photons or gravitons. We clarify why these results are not in contradiction with causality, analyticity or Lorentz invariance, and highlight various subtleties that arise when dealing with superluminalities and time advances in the gravitational context. Consistent low-energy effective theories are shown to self-protect by ensuring that any time advance and superluminality calculated within the regime of validity of the effective theory is necessarily unresolvable, and cannot be argued to lead to a macroscopically larger light cone. Such considerations are particularly relevant for putting constraints on cosmological and gravitational effective field theories and we provide explicit criteria to be satisfied so as to ensure causality.

We discuss construction and observational properties of wormholes obtained by connecting two Reissner-Nordström spacetimes with distinct mass and charge parameters. These objects are spherically symmetric, but not reflection symmetric, as the connected spacetimes differ. The reflection-asymmetric wormholes may reflect a significant fraction of the infalling radiation back to the spacetime of its origin. We interpret this effect in a simple framework of the effective photon potential. Depending on the model parameters, image of such a wormhole seen by a distant observer (its “shadow”) may contain a photon ring formed on the observer’s side, photon ring formed on the other side of the wormhole, or both photon rings. These unique topological features would allow us to firmly distinguish this class of objects from Kerr black holes using radioastronomical observations.

We present the proton and neutron vector form factors in a convenient parametric form that is optimized for momentum transfers $\lesssim \mathrm{few}{\mathrm{GeV}}^2$. The form factors are determined from a global fit to electron scattering data and precise charge radius measurements. A new treatment of radiative corrections is applied. This parametric representation of the form factors, uncertainties, and correlations provides an efficient means to evaluate many derived observables. We consider two classes of illustrative examples: neutrino-nucleon scattering cross sections at GeV energies for neutrino oscillation experiments and nucleon structure corrections for atomic spectroscopy. The neutrino-nucleon charged current quasielastic cross section differs by 3%–5% compared to commonly used form factor models when the vector form factors are constrained by recent high-statistics electron-proton scattering data from the A1 Collaboration. Nucleon structure parameter determinations include: the magnetic and Zemach radii of the proton and neutron, $[r_M^p,r_M^n]=[0.739(41)(23),0.776(53)(28)]$ fm and $[r_Z^p,r_Z^n]=[1.0227(94)(51),-0.0445(14)(3)]$ fm; the Friar radius of nucleons, $[(r_F^p{)}^3,(r_F^n{)}^3]=[2.246(58)(2),0.0093(6)(1)]{\text{fm}}^3$; the electric curvatures, $[⟨r^4{⟩}_E^p,⟨r^4{⟩}_E^n]=[1.08(28)(5),-0.33(24)(3)]{\text{fm}}^4$; and bounds on the magnetic curvatures, $[⟨r^4{⟩}_M^p,⟨r^4{⟩}_M^n]=[-2.0(1.7)(0.8),-2.3(2.1)(1.1)]{\text{fm}}^4$. The first and dominant uncertainty is propagated from the experimental data and radiative corrections, and the second error is due to the fitting procedure.

We investigate a plausible route to resolving the black hole information paradox by examining the effects of decoherence on Hawking radiation. In particular, we show that a finite but nonzero rate of decoherence can lead to efficient extraction of information from the evaporating black hole. This effectively pushes the paradox from becoming manifest at the Page time when the black hole has evaporated to half its size, to a timescale solely determined by the rate of decoherence. If this rate is due to a putative interaction with gravitons, the black hole at this timescale can be expected to be Planck sized, but notably without an extensive amount of information packed inside. We justify our findings by numerically studying a toy model of stabilizer circuits that can efficiently model black hole evaporation in the presence of decoherence. The latter is found to be well described by an effective rate equation for the entanglement and which corroborates our findings.

We describe a technique to study the asymptotics of $\mathrm{SL}(2,\mathbb{C})$ invariant tensors associated to graphs, with unitary irreps and lowest SU(2) spins, and apply it to the Lorentzian Engle-Pereira-Rovelli-Livine-Kaminski-Kieselowski-Lewandowski model of quantum gravity. We reproduce the known asymptotics of the 4-simplex graph with a different perspective on the geometric variables and introduce an algorithm valid for any graph. On general grounds, we find that critical configurations are not just Regge geometries, but a larger set corresponding to conformal twisted geometries. These can be either Euclidean or Lorentzian and include curved and flat 4D polytopes as subsets. For modular graphs, we show that multiple pairs of critical points exist, and there exist critical configurations of mixed signature, Euclidean and Lorentzian in different subgraphs, with no 4D embedding possible.

A present challenge in testing general relativity (GR) with binary black hole gravitational wave detections is the inability to perform model-dependent tests due to the lack of merger waveforms in beyond-GR theories. In this study, we produce the first numerical relativity binary black hole gravitational waveform in Einstein-dilaton-Gauss-Bonnet (EDGB) gravity, a higher-curvature theory of gravity with motivations in string theory. We evolve a binary black hole system in order-reduced EDGB gravity, with parameters consistent with GW150914. We focus on the merger portion of the waveform, due to the presence of secular growth in the inspiral phase. We compute mismatches with the corresponding general relativity merger waveform, finding that from a post-inspiral-only analysis, we can constrain the EDGB lengthscale to be $\sqrt{{\alpha }_{\mathrm{GB}}}\lesssim 11\mathrm{km}$.

We address the problem of deriving the post-Minkowskian approximation, widely used in current gravitational wave literature by investigating a possible deduction out of the recursive Nöther coupling approach, from the Pauli-Fierz spin-2 theory in flat spacetime. We find that this approach yields the post-Minkowskian approximation correctly to the first three orders, without invoking any weak-field limit of general relativity. This connection thus establishes that the post-Minkowskian approximation has a connotation independent of a weak-field expansion of general relativity, which is the manner usually presented in the literature. As a consequence, a link manifests between the recursive Nöther coupling approach to deriving general relativity from a linear spin-2 theory in flat spacetime and theoretical analyses of recent detection of gravitational wave events.

Here we have developed the general parametrization for spherically symmetric and asymptotically flat black-hole spacetimes in an arbitrary metric theory of gravity. The parametrization is similar in spirit to the parametrized post-Newtonian approximation, but valid in the whole space outside the event horizon, including the near horizon region. This generalizes the continued-fraction expansion method in terms of a compact radial coordinate suggested by Rezzolla and Zhidenko [Phys. Rev. D 90, 084009 (2014)] for the four-dimensional case. As the first application of our higher-dimensional parametrization we have approximated black-hole solutions of the Einstein-Lovelock theory in various dimensions. This allows one to write down the black-hole solution which depends on many parameters (coupling constants in front of higher curvature terms) in a very compact analytic form, which depends only upon a few parameters of the parametrization. The approximate metric deviates from the exact (but extremely cumbersome) expressions by fractions of one percent even at the first order of the continued-fraction expansion, which is confirmed here by computation of observable quantities, such as quasinormal modes of the black hole.

Observations of transient gravitational wave (GW) events with non-negligible orbital eccentricity can be highly rewarding from astrophysical considerations. Ready-to-use fully analytic frequency domain inspiral GW templates are crucial ingredients to construct eccentric inspiral-merger-ringdown waveform families, required for the detection of such GW events. It turns out that a fully analytic, post-Newtonian (PN) accurate frequency domain inspiral template family, which uses certain post-circular approximation, may only be suitable to model events with initial eccentricities $e_0\le 0.2$. We here explore the possibility of combining post-circular and Padé approximations to obtain fully analytic frequency domain eccentric inspiral templates. The resulting 1PN-accurate approximant is capable of faithfully capturing eccentric inspirals having $e_0\le 0.6$ while employing our 1PN extension of a frequency domain template family that does not use post-circular approximation, detailed in [B. Moore et al., Classical Quantum Gravity 35, 235006 (2018)]. We also discuss subtleties that arise while combining post-circular and Padé approximations to obtain higher PN order templates for eccentric inspirals.

Wave equations containing spatial derivatives which are higher than second order arise naturally in the context of condensed matter systems. The solutions of such equations contain more than two modes and consequently, the range of possible interactions between the different modes is significantly enhanced compared to the two mode case. We develop a framework for analyzing the different mode interactions based on the classical turning points of the dispersion relation. We then apply this framework to the scattering of deep water gravity waves with a draining bathtub vortex, a system which constitutes the analogue of a rotating black hole in the nondispersive limit. In particular, we show that the different scattering outcomes are controlled by the light-ring frequencies, a concept routinely applied in black hole physics, and two new frequencies which are related to the strength of dispersion. We find that the frequency range in which the reflected wave is superradiantly amplified appears as a simple modification to the nondispersive case. However, the condition to observe this amplification is complicated by the fact that a superradiant mode can be reflected back into the system by scattering with one of the additional modes. We provide estimates for the reflection coefficients in the full dispersive regime.

We consider Weyl gauge theories of gravity (WGTs), which are invariant both under local Poincaré transformations and local changes of scale. Such theories may be interpreted as gauge theories in Minkowski spacetime, but their gravitational interactions are most often reinterpreted geometrically in terms of a Weyl-Cartan spacetime, in which any matter fields then reside. Such a spacetime is a straightforward generalization of Weyl spacetime to include torsion. As first suggested by Einstein, Weyl spacetime is believed to exhibit a so-called second clock effect, which prevents the existence of experimentally observed sharp spectral lines, since the rates of (atomic) clocks depend on their past history. The prevailing view in the literature is that this rules out WGTs as unphysical. Contrary to this viewpoint, we show that if one adopts the natural covariant derivative identified in the geometric interpretation of WGTs, properly takes into account the scaling dimension of physical quantities, and recognizes that Einstein’s original objection requires the presence of massive matter fields to represent atoms, observers and clocks, then WGTs do not predict a second clock effect.

In this work, we provide a link between a nearly vanishing cosmological constant and chiral symmetry. This is accomplished with a modification of general relativity coupled to a topological field theory, namely BF theory, by introducing fermions charged under the BF theory gauge group. We find that the cosmological constant sources a chiral anomaly for the fermions, providing a “technical naturalness” explanation for the smallness of the observed cosmological constant. Applied to the early Universe, we show that production of fermions during inflation can provide all the dark matter in the Universe today, in the form of superheavy dark baryons.

We study the cosmic microwave background (CMB) in the framework of the degenerate higher-order scalar-tensor (DHOST) theory to test gravity theories. This theoretical framework includes the wide class of dark energy models such as the Horndeski theory and its extensions as certain limits, and the general relativity can be also recovered. In this study, to test gravity theories with CMB, we formulate the linear perturbations of gravity and matter in the theory and their effective description parametrized by time-dependent effective field theory (EFT) parameters, ${\alpha }_i$ ($i=B$, $K$, $T$, $M$, $H$, $L$) and ${\beta }_i$ ($i=1$, 2, 3). Based on the resultant DHOST framework, we develop a numerical code to solve Boltzmann equations consistently. We then show that the angular power spectra of the CMB temperature anisotropies, E-mode, and lensing potential as a demonstration and find that the parameter characterizing the DHOST theory, ${\beta }_1$, provides the larger modifications of the spectra, compared with other EFT parameters. We also show the results in the case of a specific model in which the cosmic expansion and the EFT parameters are consistently determined.

In this work, we extend the formalism of hybrid loop quantum cosmology for primordial perturbations around a flat, homogeneous, and isotropic universe to the new treatment of Friedmann-Lemaître-Robertson-Walker geometries proposed recently by Dapor and Liegener, based on an alternative regularization of the Hamiltonian constraint. In fact, our discussion is applicable also to other possible regularization schemes for loop quantum cosmology, although we specialize our analysis to the Dapor-Liegener proposal and construct explicitly all involved quantum operators for that case.

Present-day temperature $T_0$ of cosmic microwave background has been precisely measured by the FIRAS experiment. We identify that the early dark energy (EDE) (non-negligible around matter-radiation equality) scenario can remain compatible with the FIRAS result, while lifting the Hubble constant $H_0$. We perform Monte Carlo Markov chain analysis to confirm our observations. We also present an $\alpha$-attractor anti–de Sitter (AdS) model of EDE, in which the AdS depth is consistently varied in the Monte Carlo Markov chain analysis. We found that our datasets weakly hinted the existence of an AdS phase near recombination with $H_0\sim 73\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ at $1\sigma$ region in the best-fit model.

We study the generation of gravitational waves (GWs) during the single-field preheating in the $\alpha$-attractor inflation in this paper. We find that the oscillation of the inflaton leads to an intermittent tachyonic instability for certain inflaton fluctuations, which results in that the inflaton quanta become a significant source of GWs. At the beginning of the preheating, the low frequency GW modes grow rapidly, and then nonlinear effects set in and lead to the growth of modes with relatively high frequencies. When the model parameter $\alpha$ is chosen to be very small, e.g., ${10}^{-5}$, the GW density spectrum increases very fast and the value of model parameter $n$ has negligible effect. However, when $\alpha$ becomes relatively large, e.g., ${10}^{-4}$ or ${10}^{-3}$, the growth of inflaton quanta is inversely proportional to the value of $n$ since a smaller value of $n$ corresponds to a more negative value of the mass square of the inflaton. This effect leads to that the maximum value of the today’s total energy density of GWs occurs at $n=1$ and $\alpha ={10}^{-4}$ among different values of model parameters considered in our analysis. Furthermore, we find that the GWs produced during the single-field preheating in the $\alpha$-attractor inflation satisfy the constraints from the Planck and those expected from the next-generation CMB experiments.

Future high spectroscopic resolution galaxy surveys will observe galaxies with nearly full-sky footprints. Modeling the galaxy clustering for these surveys, therefore, must include the wide-angle effect with narrow redshift binning. In particular, when the redshift-bin size is comparable to the typical peculiar velocity field, the nonlinear redshift-space distortion (RSD) effect becomes important. A naive projection of the Fourier-space RSD model to spherical harmonic space leads to diverging expressions. In this paper we present a general formalism of projecting the higher-order RSD terms into spherical harmonic space. We show that the nonlinear RSD effect, including the fingers-of-God, can be entirely attributed to a modification of the radial window function. We find that while linear RSD enhances the harmonic-space power spectrum, unlike the three-dimensional case, the enhancement decreases on small angular scales. The fingers-of-God suppress the angular power spectrum on all transverse scales if the bin size is smaller than $\mathrm{\Delta }r\lesssim \pi {\sigma }_u$; for example, the radial bin sizes corresponding to a spectral resolution $R=\lambda /\mathrm{\Delta }\lambda$ of a few hundred satisfy the condition. We also provide the flat-sky approximation which reproduces the full calculation to subpercent accuracy.

The origin and nature of ultrahigh energy cosmic rays remains a mystery. However, great progress has been made in recent years due to the observations performed by the Pierre Auger Observatory and Telescope Array. In particular, it is believed that the composition information of the cosmic rays as a function of the energy can play a fundamental role for the understanding of their origin. The best indicators for primary mass composition are the muon content of extensive air shower and the atmospheric depth of the shower maximum. In this work we consider a maximum likelihood method to perform mass composition analyses based on the number of muons measured by underground muon detectors. The analyses are based on numerical simulations of the showers. The effects introduced by the detectors and the methods used to reconstruct the experimental data are also taken into account through a dedicated simulation that uses as input the information of the simulated showers. In order to illustrate the use of the method, we consider AMIGA (Auger Muons and Infill for the Ground Array), the low energy extension of the Pierre Auger Observatory that directly measures the muonic content of extensive air showers. We also study in detail the impact of the use of different high energy hadronic interaction models in the composition analyses performed. It is found that differences of a few percent between the predicted number of muons have a significant impact on composition determination.