Within the nonrelativistic QCD (NRQCD) factorization framework, we compute the $\mathcal{O}({\alpha }_s{v}^2)$ corrections to the hadronic decay rate of vector quarkonia, exemplified by $J/\psi$ and $\mathrm{\Upsilon }$. Setting both the renormalization and NRQCD factorization scales to be $m_Q$, we obtain $\mathrm{\Gamma }(J/\psi \to \mathrm{LH})=0.0716\frac{{\alpha }_s^3}{m_c^2}⟨{\mathcal{O}}_1({{}^{3}S}_1){⟩}_{J/\psi }[1-1.19{\alpha }_s+(-5.32+3.03{\alpha }_s)⟨v^2{⟩}_{J/\psi }]$ and $\mathrm{\Gamma }(\mathrm{\Upsilon }\to \mathrm{LH})=0.0716\frac{{\alpha }_s^3}{m_b^2}⟨{\mathcal{O}}_1({{}^{3}S}_1){⟩}_{\mathrm{\Upsilon }}[1-1.56{\alpha }_s+(-5.32+4.61{\alpha }_s)⟨v^2{⟩}_{\mathrm{\Upsilon }}]$. We confirm the previous calculation of $\mathcal{O}({\alpha }_s)$ corrections on a diagram-by-diagram basis, with the accuracy significantly improved. For $J/\psi$ hadronic decay, we find that the $\mathcal{O}({\alpha }_s{v}^2)$ corrections are moderate and positive, nevertheless unable to counterbalance the huge negative corrections. On the other hand, the effect of $\mathcal{O}({\alpha }_s{v}^2)$ corrections for $\mathrm{\Upsilon }(nS)$ is sensitive to the $\mathcal{O}(v^2)$ NRQCD matrix elements. With the appropriate choice of the NRQCD matrix elements, our theoretical predictions for the decay rates may be consistent with the experimental data for $\mathrm{\Upsilon }(1S,2S)\to \mathrm{LH}$. As a by-product, we also present the theoretical predictions for the branching ratio of $J/\psi (\mathrm{\Upsilon })\to 3\gamma$ accurate up to $\mathcal{O}({\alpha }_s{v}^2)$.

We measure the liquid argon scintillation response to electronic recoils in the energy range of 2.82 to 1274.6 keV at null electric field. The single-phase detector with a large optical coverage used in this measurement yields $12.8\pm 0.3(11.2\pm 0.3)\text{photoelectron}/\mathrm{keV}$ for 511.0-keV $\gamma$-ray events based on a photomultiplier tube single photoelectron response modeling with a Gaussian plus an additional exponential term (with only a Gaussian term). It is exposed to a variety of calibration sources such as ${}^{22}\mathrm{Na}$ and ${}^{241}\mathrm{Am}$ $\gamma$-ray emitters, and a ${}^{252}\mathrm{Cf}$ fast neutron emitter that induces quasimonoenergetic $\gamma$ rays through a $(n,n^{\prime }\gamma )$ reaction with ${}^{19}\mathrm{F}$ in polytetrafluoroethylene. In addition, the high light detection efficiency of the detector enables identification of the 2.82-keV peak of ${}^{37}\mathrm{Ar}$, a cosmogenic isotope in atmospheric argon. The observed light yield and energy resolution of the detector are obtained by the full-absorption peaks. We find up to approximately 25% shift in the scintillation yield across the energy range and 3% of the energy resolution for the 511.0-keV line. The Thomas-Imel box model with its constant parameter $\varsigma =0.033_{-0.008}^{+0.012}$ is found to explain the result. For liquid argon, this is the first measurement on the energy-dependent scintillation yield down to a few keV at null field and provides essential inputs for tuning the argon response model to be used for physics experiments.

We investigate the phenomenon of gravity-induced entanglement in optomechanical systems. Assuming photon number conservation and the Newtonian potential expanded up to the quadratic order of the oscillator positions, we exactly solve the dynamics of the optomehcanical systems. Then, we find that the phase difference due to the Newtonian gravity leads to the large entanglement of photons in separated cavities. We clarify the generating mechanism of large gravity-induced entanglements in optomechanical systems in an exact manner. We also determine the characteristic time to generate the maximal entanglement of photons. Finally, by comparing the characteristic time with the decoherence time due to photon leakage, we evaluate the range of the dissipation rate required for testing the gravity-induced entanglement.

Starting from a local action for mimetic gravity that includes higher derivatives of a scalar field $\varphi$, we derive a gauge-fixed canonical action of the theory in the Arnowitt-Deser-Misner canonical formalism in the time gauge $\varphi =t$. This reduced action reveals (i) a nonvanishing conserved physical Hamiltonian that is a sum of two terms, the expression for the Hamiltonian constraint of general relativity and a function of the expansion scalar, and (ii) a reduced symplectic structure that geometrically provides the Dirac brackets. As applications of our general analysis, we compute the physical Hamiltonians and canonical equations for perturbations around Minkowski spacetime, homogeneous cosmologies, and spherically symmetric spacetimes.

In this work, we present an extensive dynamical analysis of the null geodesics in the spacetimes proposed by Casadio, Fabbri, and Mazzacurati (CFM), which model black holes and wormholes in a Randall-Sundrum brane. Geodesic stability is evaluated by Lyapunov and Jacobi criteria, with coinciding results. Semistable photon spheres are found in the geometries of interest. Bifurcations associated with the dynamical system are also investigated, characterizing a degenerated Bogdanov-Takens bifurcation. Our results suggest deep connections between the geometric characteristics of the CFM spacetimes and the dynamics of null geodesics in these backgrounds.

The main problems of nonvacuum numerical relativity, compact binary mergers and stellar collapse, involve hydromagnetic instabilities and turbulent flows, so that kinetic energy at small scales leads to mean effects at large scale that drive the secular evolution. Notable among these effects is momentum transport. We investigate two models of this transport effect, a relativistic Navier-Stokes system and a turbulent mean stress model, that are similar to all of the prescriptions that have been attempted to date for treating subgrid effects on binary neutron star mergers and their aftermath. Our investigation involves both stability analysis and numerical experimentation on star and disk systems. We also begin the investigation of the effects of particle and heat transport on postmerger simulations. We find that correct handling of turbulent heating is crucial for avoiding unphysical instabilities. Given such appropriate handling, the evolution of a differentially rotating star and the accretion rate of a disk are reassuringly insensitive to the choice of prescription. However, disk outflows can be sensitive to the choice of method, even for the same effective viscous strength. We also consider the effects of eddy diffusion in the evolution of an accretion disk and show that it can interestingly affect the composition of outflows.

The Wheeler equation, for electromagnetic disturbances in a gravitational field, was found by Fiziev to have exact solutions both above and below the event horizon, in the form of waves propagating both inwardly and outwardly. This observation can be interpreted and verified from the optical point of view, entirely on the basis of the Schwarzschild metric for length contraction and time dilation, in order to derive a differential version of Snell’s law for the Schwarzschild black hole. It reveals interesting physics, including the correct amount of light deflection by the Sun, internal and external Oppenheimer-Snyder cones of the black hole, properties of its phonon sphere and the conclusion that light rays are kept below the horizon by length contraction and time dilation rather than deflection.

We derive the gravitational Lagrangian to all orders of curvature when the canonical constraint algebra is deformed by a phase space function as predicted by some studies into loop quantum cosmology. The deformation function seems to be required to satisfy a nonlinear conservation equation usually found in fluid mechanics and can form discontinuities quite generally. These results arise from attempting to consistently incorporate general spatial inhomogeneities in effective models of loop quantum cosmology rather than directly investigating the nature of signature change in such models. We work within the restriction of not allowing additional degrees of freedom.

When two black holes merge, a tremendous amount of energy is released in the form of gravitational radiation in a short span of time, making such events among the most luminous phenomenon in the Universe. Models that predict the peak luminosity of black hole mergers are of interest to the gravitational wave community, with potential applications in tests of general relativity. We present a surrogate model for the peak luminosity that is directly trained on numerical relativity simulations of precessing binary black holes. Using Gaussian process regression, we interpolate the peak luminosity in the seven-dimensional parameter space of precessing binaries with mass ratios $q\le 4$ and spin magnitudes ${\chi }_1$, ${\chi }_2\le 0.8$. We demonstrate that our errors in estimating the peak luminosity are lower than those of existing fitting formulas by about an order of magnitude. In addition, we construct a model for the peak luminosity of aligned-spin binaries with mass ratios $q\le 8$ and spin magnitudes $|{\chi }_{1z}|,|{\chi }_{2z}|\le 0.8$. We apply our precessing model to infer the peak luminosity of the GW event GW190521 and find the results to be consistent with previous predictions.

We consider the spacetime presented by Bonnor in 1998, whose matter content is a spheroid of electrically counterpoised dust, in the context of the geometrical inequalities between area and charge. We determine numerically the constant mean curvature surfaces that are candidates to be stable isoperimetric surfaces and analyze the relation between area and charge for them, showing that both a previously proved inequality and a conjectured inequality are far from being saturated. We also show that the maximal initial data has a cylindrical limit where the minimum of the area-charge relation is attained.

Systems of enhanced memory capacity are subjected to a universal effect of memory burden, which suppresses their decay. In this paper, we study a prototype model to show that memory burden can be overcome by rewriting stored quantum information from one set of degrees of freedom to another one. However, due to a suppressed rate of rewriting, the evolution becomes extremely slow compared to the initial stage. Applied to black holes, this predicts a metamorphosis, including a drastic deviation from Hawking evaporation, at the latest after losing half of the mass. This raises a tantalizing question about the fate of a black hole. As two likely options, it can either become extremely long lived or decay via a new classical instability into gravitational lumps. The first option would open up a new window for small primordial black holes as viable dark matter candidates.

The runaway potentials, which do not possess any critical points, are viable potentials which befit the recently proposed de Sitter swampland conjecture very well. In this work, we embed such potentials in the warm inflation scenario motivated by quantum field theory models generating a dissipation coefficient with a dependence cubic in the temperature. It is demonstrated that such models are able to remain in tune with the present observations and they can also satisfy all three swampland conjectures, namely, the swampland distance conjecture, the de Sitter conjecture, and the trans-Planckian censorship conjecture, simultaneously. These features make such models viable from the point of view of effective field theory models in quantum gravity and string theory, away from the swampland.

We examine the fundamental ($f$) and the 1st pressure ($p_1$) mode frequencies in gravitational waves from cold neutron stars constructed with various unified realistic equations of state. With the calculated frequencies, we derive the empirical formulas for the $f$- and $p_1$-mode frequencies, $f_f$ and $f_{p_1}$, as a function of the square root of the stellar average density and the parameter ($\eta$), which is a combination of the nuclear saturation parameters. With our empirical formulas, we show that by simultaneously observing the $f$- and $p_1$-mode gravitational waves, when $1.5\lesssim f_{p_1}/f_f\lesssim 2.5$ (which corresponds to neutron star models with the mass of less than or approximately equal to $0.9M_{\odot }$), one could estimate the value of $\eta$ within approximately 10% accuracy, which makes a strong constraint on the equation of state for neutron star matter. In addition, we find that the maximum $f$-mode frequency is strongly associated with the minimum radius of neutron star. That is, if one would observe a larger frequency of the $f$ mode, one might constrain the upper limit of the minimum neutron star radius.

Quantum black hole production at the Large Hadron Collider is investigated using the horizon quantum mechanics model. This model has novel implications for how black holes might be observed in collider experiments. Black hole production is predicted to be possible below the Planck scale, thus leading to the intriguing possibility that black holes could be produced even if the Planck scale is slightly above the collider center of mass energy. In addition, the usual anticipated resonance in the black hole mass distribution is significantly widened in this model. For values of the Planck scale above the current lower limits, the shape of the black hole mass distribution is almost independent of the Planck scale and depends more on the number of extra dimensions. These model features suggest the need for alternative search strategies in collider experiments.

The flavor-changing neutral current decay processes of the $B$ and $B_c$ mesons with the final states involving spin-$1/2$ particles are investigated. By considering the background of the Standard Model, where $\nu \overline{\nu }$ contributes the missing energy and the experimental upper bounds for the branching fractions, we get the constraints of the coupling constants of the quark-antiquark and the assumed invisible particles $\chi \overline{\chi }$. The constraints of the coupling constants are then used to study the similar processes of the $B_c$ meson. At some specific region of $m_{\chi }$, the upper limit of $\mathrm{BR}(B_c\to D_{(s)}\chi \overline{\chi })$ is of the order of ${10}^{-6}$, while for $\mathrm{BR}(B_c\to D_{(s)}^{*}\chi \overline{\chi })$), it is ${10}^{-5}$. The possibility of distinguishing $\chi$ to be a Majorana or Dirac fermion by the differential branching fractions is also discussed.

We study the description of nucleons and diquarks in the presence of a uniform strong magnetic field within the framework of the two-flavor Nambu–Jona-Lasinio model. Diquarks are constructed through the resummation of quark loop chains using the random phase approximation, while nucleons are treated as bound quark-diquark states described by a relativistic Fadeev equation, using the static approximation for quark exchange interactions. For charged particles, analytical calculations are performed using the Ritus eigenfunction method, which properly takes into account the breakdown of translation invariance that arises from the presence of Schwinger phases. Within this scheme, for definite model parametrizations we obtain numerical predictions for diquark and nucleon masses, which are compared with chiral perturbation theory and lattice QCD results. In addition, numerical estimations for nucleon magnetic moments are obtained.

We analyze the problem of neutrino oscillations via a fermionic particle detector model inspired by the physics of the Fermi theory of weak interactions. The model naturally leads to a description of emission and absorption of neutrinos in terms of localized two-level systems. By explicitly including source and detector as part of the dynamics, the formalism is shown to recover the standard results for neutrino oscillations without mention to “flavor states,” which are ill defined in quantum field theory. This illustrates how particle detector models provide a powerful theoretical tool to approach the measurement issue in quantum field theory and emphasizes that the notion of flavor states, although sometimes useful, must not play any crucial role in neutrino phenomenology.