The axial-vector form factors of the $\mathrm{spin}-{\frac{3}{2}}^{+}$ decuplet baryons are investigated in the chiral constituent quark model using their explicit quark spin polarizations. The quark sea arises from the chiral symmetry breaking, which results in the Goldstone bosons mediating the interaction between constituent quarks. The axial-vector form factors, which have some physical significance corresponding to the flavor singlet current, flavor isovector (triplet) current, and the flavor hypercharge axial (octet) current at zero momentum transfer, are, respectively $G_{\mathrm{AV},B^{*\frac{3}{2}}}^0(0)$, $G_{\mathrm{AV},B^{*\frac{3}{2}}}^3(0)$, and $G_{\mathrm{AV},B^{*\frac{3}{2}}}^8(0)$. In order to further understand the $Q^2$ dependence of these form factors, we have used the dipole form of parametrization. The qualitative and quantitative contribution of the quark sea has also been investigated by varying the transition probability of the chiral fluctuation.

We suggest that the decay modes of kaons with a pion and a pionium (${\pi }^{+}{\pi }^{-}$ atom) in the final state can constitute a not yet considered background to the very rare decay $K\to \pi \nu \overline{\nu }$. In fact, a part of pioniums may escape the decay region before decaying into two ${\pi }^0$s (or to ${\pi }^0{\pi }^0\gamma$ in the case of excited pionium). To illustrate the importance of this background, we show that it may even explain, under some assumptions, the unexpected $K_L$ decay events that appeared in the KOTO experiment.

The relative branching fractions of $B^{+}\to h^{+}{h}^{\prime +}{h}^{\prime -}$ decays, where $h^{(\prime )}$ is a pion or kaon, are measured. The analysis is performed with a data sample, collected with the LHCb detector, corresponding to an integrated luminosity of $3.0{\mathrm{fb}}^{-1}$ of $pp$ collisions. The results obtained improve significantly on previous measurements of these quantities, and are important for the interpretation of Dalitz plot analyses of three-body charmless hadronic decays of $B^{+}$ mesons.

According to the covariant open superstring description of D-branes in the ${\mathrm{AdS}}_4\times {\mathbf{CP}}^3$ background, $1/2$-BPS D2-branes are purely instantonic. Based on this and by taking the eleven dimensional viewpoint, we identify the $1/2$-BPS instantonic M2-brane configurations in the ${\mathrm{AdS}}_4\times {\mathrm{S}}^7/{\mathbf{Z}}_k$ background, which reduces to the ${\mathrm{AdS}}_4\times {\mathbf{CP}}^3$ under the large $k$ limit, and evaluate their action values. We also consider the previously known $1/2$-BPS instantonic objects in ten dimensions from the M2-brane viewpoint to compare with our results.

This article presents an effective quantum extension of the seminal Oppenheimer-Snyder (OS) collapse in which the singularity resolution is modeled using the effective dynamics of the spatially closed loop quantum cosmology. Imposing the minimal junction conditions, namely the Israel-Darmois conditions, we glue this bouncing Loop Quantum Cosmology (LQC) geometry to the classical vacuum exterior Schwarzschild geometry across a timelike thin shell. Consistency of the construction leads to several major deviations from the classical OS collapse model. Firstly, no trapped region can form, and the bounce occurs always above or at most, at the Schwarzschild radius. Secondly, the bouncing star discussed here admits an IR cutoff, in addition to the UV cutof,f and therefore corresponds to a pulsating compact object. Thirdly, the scale at which quantum gravity effects become non-negligible is encoded in the ratio between the UV cutoff of the quantum theory and the IR cutoff, which in turn encodes the minimal energy density ${\rho }_{\min }$ of the star prior to collapse. This energy density is no more fixed by the mass and maximal radius as in the classical OS model but is now a free parameter of the model. In the end, while the present model cannot describe a black-to-white hole bounce as initially suggested by the Planck star model, it provides a concrete realization of a pulsating compact object based on LQC techniques. Consistency of the model shows that its regime of applicability is restricted to Planckian relics, while macroscopic stellar objects are excluded. This first minimal construction should serve as a platform for further investigations in order to explore the physics of bouncing compact objects within the framework of loop quantum cosmology.

We study asymptotically flat black holes with massive graviton hair within the ghost-free bigravity theory. There have been contradictory statements in the literature about their existence—such solutions were reported some time ago, but later a different group claimed the Schwarzschild solution to be the only asymptotically flat black hole in the theory. As a result, the controversy emerged. We have analyzed the issue ourselves and have been able to construct such solutions within a carefully designed numerical scheme. We find that for given parameter values there can be one or two asymptotically flat hairy black hole solutions in addition to the Schwarzschild solution. We analyze their perturbative stability and find that they can be stable or unstable, depending on the parameter values. The masses of stable hairy black holes that would be physically relevant range form stellar values up to values typical for supermassive black holes. One of their two metrics is extremely close to Schwarzschild, while all their “hair” is hidden in the second metric that is not coupled to matter and not directly seen. If the massive bigravity theory indeed describes physics, the hair of such black holes should manifest themselves in violent processes like black hole mergers and should be visible in the structure of the signals detected by LIGO/VIRGO.

We give strong numerical evidence for the existence of an instability afflicting six-dimensional Reissner-Nordström de Sitter (RNdS) black holes. This instability is akin of the Konoplya-Zhidenko instability present in RNdS black holes in seven spacetime dimensions and above. Moreover, we perform a detailed analysis of the near-horizon limit of extremal RNdS black holes, and find that, typically, unstable gravitational modes effectively behave as a massive scalar field whose mass violates the ${\mathrm{AdS}}_2$ Breitenlöhner-Freedman bound (if and only if $d\ge 6$), thus providing a physical argument for the existence of the instability. Finally, we show that the frequency spectrum of perturbations of RNdS has a remarkable intricate structure with several bifurcations/mergers that appears unique to RNdS black holes.

We consider the dielectric Skyrme model proposed recently, with and without the addition of the standard pion mass term. Then we write down Bogomol’nyi-type energy bounds for both the massless and massive cases. We further show that, except for when taking the strict Bogomol’nyi-Prasad-Sommerfield (BPS) limit, the skyrmions are made of three orthogonal dipoles that can always be placed in their attractive channel and form bound states. Finally, we study the model numerically and discover that, long before realistic binding energies are reached, the skyrmions become bound states of well-separated point-particle-like skyrmions. By going sufficiently close to the BPS limit, we are able to obtain classical binding energies of realistic values compared with experiments.

The process of electron-positron annihilation into two photons in the presence of an intense classical plane wave of an arbitrary shape is investigated analytically by employing light-cone quantization and by taking into account the effects of the plane wave exactly. We introduce a general description of second-order 2-to-2 scattering processes in a plane-wave background field, indicating the necessity of considering the localization of the colliding particles and achieving that by means of wave packets. We define a local cross section in the background field, which generalizes the vacuum cross section and which, though not being directly an observable, allows for a comparison between the results in the plane wave and in vacuum without relying on the shape of the incoming wave packets. Two possible cascade or two-step channels have been identified in the annihilation process, and an alternative way of representing the two-step and one-step contributions via a “virtuality” integral has been found. Finally, we compute the total local cross section to leading order in the coupling between the electron-positron field and the quantized photon field, excluding the interference between the two leading-order diagrams arising from the exchange of the two final photons, and express it in a relatively compact form. In contrast to processes in a background field initiated by a single particle, the pair annihilation into two photons, in fact, also occurs in vacuum. Our result naturally embeds the vacuum part and reduces to the vacuum expression, known in the literature, in the case of a vanishing laser field.

We put forward the framework of simplified leptoquark models: simple extensions of the Standard Model that serve as benchmarks to test the interactions of leptons with new colored degrees of freedom considered, for instance, in leptoquark or grand unification models. As a first application of the scheme, we analyze the power of precision lepton observables by computing gauge invariant two-loop radiative corrections to the lepton-photon vertex, generated here by Yukawa interactions between the lepton and new colored degrees of freedom. The result, detailed in explicit expressions for the involved form factors, improves on the literature for the higher loop order considered and highlights the existence of regions in the parameter space of the model where two-loop corrections cannot be neglected.

We examine the polarized doubly-virtual Compton scattering (VVCS) off the nucleon using chiral perturbation theory ($\chi \mathrm{PT}$). The polarized VVCS contains a wealth of information on the spin structure of the nucleon which is relevant to the calculation of the two-photon-exchange effects in atomic spectroscopy and electron scattering. We report on a complete next-to-leading-order calculation of the polarized VVCS amplitudes $S_1(\nu ,Q^2)$ and $S_2(\nu ,Q^2)$, and the corresponding polarized spin structure functions $g_1(x,Q^2)$ and $g_2(x,Q^2)$. Our results for the moments of polarized structure functions, partially related to different spin polarizabilities, are compared to other theoretical predictions and “data-driven” evaluations, as well as to the recent Jefferson Lab measurements. By expanding the results in powers of the inverse nucleon mass, we reproduce the known “heavy-baryon” expressions. This serves as a check of our calculation, as well as demonstrates the differences between the manifestly Lorentz-invariant baryon $\chi \mathrm{PT}$ and heavy-baryon frameworks.

A search for heavy resonances decaying into a $W$ or $Z$ boson and a Higgs boson produced in $\mathrm{proton}-\mathrm{proton}$ collisions at the Large Hadron Collider at $\sqrt{s}=13\mathrm{TeV}$ is presented. The analysis utilizes the dominant $W\to q{\overline{q}}^{\prime }$ or $Z\to q\overline{q}$ and $H\to b\overline{b}$ decays with substructure techniques applied to large-radius jets. A sample corresponding to an integrated luminosity of $139{\mathrm{fb}}^{-1}$ collected with the ATLAS detector is analyzed and no significant excess of data is observed over the background prediction. The results are interpreted in the context of the heavy vector triplet model with spin-1 $W^{\prime }$ and $Z^{\prime }$ bosons. Upper limits on the cross section are set for resonances with mass between 1.5 and 5.0 TeV, ranging from 6.8 to 0.53 fb for $W^{\prime }\to WH$ and from 8.7 to 0.53 fb for $Z^{\prime }\to ZH$ at the 95% confidence level.

Recently, for the first time, the BESIII Collaboration reported the strange hidden charm tetraquark states $Z_{cs}(3985{)}^{-}$ in the $K^{+}$ recoil-mass spectrum near the $D_s^{-}{D}^{*0}/D_s^{*-}{D}^0$ mass thresholds in the processes of $e^{+}{e}^{-}\to K^{+}(D_s^{-}{D}^{*0}+D_s^{*-}{D}^0)$ at $\sqrt{s}=4.681\mathrm{GeV}$ (M. Ablikim et al., arXiv:2011.07855). The significance was estimated to be $5.3\sigma$. We show that the newly observed $Z_{cs}(3985{)}^{-}$ state is the $U$-spin partner of $Z_c(3900{)}^{-}$ as a resonance within coupled-channel calculation in the ${\mathrm{SU}(3)}_F$ symmetry and heavy quark spin symmetry (HQSS). In the ${\mathrm{SU}(3)}_F$ symmetry, we introduce the $G_{U/V}$ parity to construct the flavor wave functions of the $Z_{cs}$ states. In a unified framework, we consider the $J/\psi \pi (K)$, ${\overline{D}}_{(s)}{D}^{*}/{\overline{D}}_{(s)}^{*}D$ coupled-channel effect with the contact interaction. With the masses and widths of $Z_c(3900)$ and $Z_c(4020)$, we determine all the unknown coupling constants. We obtain mass and width of $Z_{cs}(3985)$ in good agreement with the experimental results, which strongly support the $Z_{cs}$ states as the $U/V$-spin partner states of the charged $Z_c(3900)$. We also calculate the ratio of the partial decay widths of $Z_{cs}(3985)$, which implies that the ${\overline{D}}_s{D}^{*}/{\overline{D}}_s^{*}D$ decay modes are dominant. We also predict the $Z_{cs}^{\prime }$ states with a mass around 4130 MeV and width around 30 MeV, which are the $U/V$-spin partner states of the charged $Z_c(4020)$ and HQSS partner states of the $Z_{cs}(3985)$. In the hidden bottom sector, we predict the strange tetraquark states $Z_{bs}$ and $Z_{bs}^{\prime }$ with a mass around 10700 and 10750 MeV, which are the $U/V$-spin partner states of $Z_b(10610{)}^{\pm }$ and $Z_b(10650{)}^{\pm }$, respectively.

Scattering amplitudes of massless particles in Minkowski space can be expressed in a conformal basis by Mellin transforming the momentum space amplitudes to correlation functions on the celestial sphere at null infinity. In this paper, we study celestial amplitudes of loop-level gluons and gravitons. We focus on the rational amplitudes that carry all-plus and single-minus external helicities. Because these amplitudes are finite, they provide a concrete example of celestial amplitudes of Yang- Mills and gravity theory beyond tree level. We give explicit examples of four- and five-point functions and comment on higher point amplitudes.

The regularization of quantum electrodynamics in the space of functions ${\psi }_a(x)$, which depend on both the position $x$ and the scale $a$, is presented. The scale-dependent functions are defined in terms of the continuous wavelet transform in ${\mathbb{R}}^4$ Euclidean space, with the derivatives of Gaussian served as mother wavelets. The vacuum polarization and the dependence of the effective coupling constant on the scale parameters are calculated in one-loop approximation in the limit $p^2\gg 4m^2$.

Data from gravitational wave detectors are recorded as time series that include contributions from myriad noise sources in addition to any gravitational wave signals. When regularly sampled data are available, such as for ground based and future space based interferometers, analyses are typically performed in the frequency domain, where stationary (time invariant) noise processes can be modeled very efficiently. In reality, detector noise is not stationary due to a combination of short duration noise transients and longer duration drifts in the power spectrum. This nonstationarity produces correlations across samples at different frequencies, obviating the main advantage of a frequency domain analysis. Here an alternative time-frequency approach to gravitational wave data analysis is proposed that uses discrete, orthogonal wavelet wave packets. The time domain data is mapped onto a uniform grid of time-frequency pixels. For locally stationary noise—that is, noise with an adiabatically varying spectrum—the time-frequency pixels are uncorrelated, which greatly simplifies the calculation of quantities such as the likelihood. Moreover, the gravitational wave signals from binary systems can be compactly represented as a collection of lines in time-frequency space, resulting in a computational cost for computing waveforms and likelihoods that scales as the square root of the number of time samples, as opposed to the linear scaling for time or frequency based analyses. Key to this approach is having fast methods for computing binary signals directly in the wavelet domain. Multiple fast transform methods are developed in detail.

Stellar-mass black hole binaries, like those currently being detected with the ground-based gravitational wave (GW) observatories LIGO and Virgo, are also an anticipated GW source in the Laser Interferometer Space Antenna (LISA) band. LISA will observe them during the early inspiral stage of evolution; some of them will chirp through the LISA band and reappear some time later in the band of third generation ground-based GW detectors. Stellar-mass black hole binaries could serve as laboratories for testing the theory of general relativity and inferring the astrophysical properties of the underlying population. In this study, we assess LISA’s ability to infer the parameters of those systems, a crucial first step in understanding and interpreting the observation of those binaries and their use in fundamental physics and astrophysics. We simulate LISA observations for several fiducial sources, setting the noise realization to zero, and perform a full Bayesian analysis. We demonstrate and explain degeneracies in the parameters of some systems. We show that the redshifted chirp mass and the sky location are always very well determined, with typical errors below ${10}^{-4}$ (fractional) and $0.4{\mathrm{deg}}^2$. The luminosity distance to the source is typically measured within 40–60%, resulting in a measurement of the chirp mass in the source frame of $\mathcal{O}(1\%)$. The error on the time to coalescence improves from $\mathcal{O}(1\mathrm{day})$ to $\mathcal{O}(30\mathrm{s})$ as we observe the systems closer to their merger. We introduce an augmented Fisher-matrix analysis which gives reliable predictions for the intrinsic parameters compared to the full Bayesian analysis. Finally, we show that combining the use of the long-wavelength approximation for the LISA instrumental response together with the introduction of a degradation function at high frequencies yields reliable results for the posterior distribution when used self-consistently, but not in the analysis of real LISA data.

The Ashtekar-Streubel fluxes give a proposed definition of the angular momentum emitted by an isolated gravitationally radiating system. This was based on identifying a “phase space of radiative modes,” independent of any internal degrees of freedom, and using the Hamiltonian functions conjugate to the action of the Bondi-Metzner-Sachs (BMS) group as the energy-momentum, supermomentum, and angular momentum. However, there are some difficulties in formulating this phase space so as to get the proper degrees of freedom. I consider how to address this point, and also to identify circumstances in which the radiative modes are sufficiently decoupled that they can be assigned their own angular momentum. Two different phase spaces are considered. One, which seems to reflect what previous workers have done (it leads to the usual formulas for the Ashtekar-Streubel fluxes), is mathematically simpler, but this has unwanted degrees of freedom and is difficult to interpret physically. The second is a quotient of the first; it is better justified (at least in terms of degrees of freedom), and plausibly decouples the radiative angular momentum from internal modes (at least for systems which ultimately become stationary). The symplectic form for this quotient and the corresponding angular momentum flux involve highly nonlocal correlations. Both phase spaces are shown to have Poisson brackets implementing the BMS algebra. For both phase spaces, for axisymmetric spacetimes vacuum near null infinity, there can be no gravitational radiation of angular momentum about the axis of symmetry, although matter can carry off angular momentum in such cases.

We demonstrate that the early Universe in bimetric theory is screened by the Vainshtein mechanism on a Friedmann-Lemaître-Robertson-Walker background. The spin-2 mass serves as the cosmological Vainshtein scale in this case. This allows us to quantitatively address early Universe cosmology. In particular, in a global analysis, we study data from the cosmic microwave background radiation and local measurements of the Hubble flow. We show that bimetric cosmology resolves the discrepancy in the local and early-time measurements of the Hubble scale via an effective phantom dark energy component.