We compute the $\overline{h}c$ (pseudo)scalar, (axial-)vector and (axial-)tensor susceptibilities as a function of $u=m_c/m_h$ between $u=m_c/m_b$ and $u=0.8$ using fully relativistic lattice QCD, employing nonperturbative current renormalization and using the second generation $2+1+1$ MILC HISQ gluon field configurations. We include ensembles with $a\approx 0.09$, 0.06, 0.045, and 0.033 fm and we are able to reach the physical $b$-quark on the two finest ensembles. At the physical $m_h=m_b$ point we find ${\overline{m}}_b^2{\chi }_{1^{+}}=0.720(34)\times {10}^{-2}$, ${\overline{m}}_b^2{\chi }_{1^{-}}=1.161(54)\times {10}^{-2}$, ${\chi }_{0^{-}}=2.374(33)\times {10}^{-2}$, and ${\chi }_{0^{+}}=0.609(14)\times {10}^{-2}$. Our results for the (pseudo)scalar, vector, and axial vector are compatible with the expected small size of nonperturbative effects at $u=m_c/m_b$. We also give the first nonperturbative determination of the tensor susceptibilities, finding ${\overline{m}}_b^2{\chi }_T=0.891(44)\times {10}^{-2}$ and ${\overline{m}}_b^2{\chi }_{AT}=0.441(33)\times {10}^{-2}$. Our value of ${\overline{m}}_b^2{\chi }_{AT}$ is in good agreement with the $\mathcal{O}({\alpha }_s)$ perturbation theory, while our result for ${\overline{m}}_b^2{\chi }_T$ is in tension with the $\mathcal{O}({\alpha }_s)$ perturbation theory at the level of $2\sigma$. These results will allow for dispersively bounded parametrizations to be employed using lattice inputs for the full set of $h\to c$ semileptonic form factors in future calculations, for heavy-quark masses in the range $1.25\times m_c\le m_h\le m_b$.

In this work, we investigate the inclusive photoproduction of the $C$-odd, $S$-wave fully charmed tetraquark at electron-ion colliders within the nonrelativistic QCD (NRQCD) factorization framework, at the lowest order in velocity and ${\alpha }_s$. The value of the NRQCD long-distance matrix element is estimated from two phenomenological potential models. Our studies reveal that the photoproduction of the $1^{+-}$ fully charmed tetraquark may be difficult to observe at HERA and the EicC; nevertheless, its observation prospects at the EIC appear to be bright.

We calculate helicity amplitudes for $e^{-}{e}^{+}\to W^{-}{W}^{+}$ analytically in the Feynman-diagram (FD) gauge. We show that, unlike in the unitary gauge, there is no energy growth of the individual Feynman amplitudes for the longitudinally polarized W bosons, and the contributions from the associated Goldstone bosons are manifest even without taking the high-energy limit. We also find that the physical distributions can be interpreted by the individual amplitudes in the FD gauge.

We study the purely leptonic decays of heavy-flavored charged pseudoscalar ($P$) and vector ($V$) mesons ($D_{(s)}^{(*)+}$, $B_{(c)}^{(*)+}$) in the relativistic independent quark (RIQ) model based on an average flavor-independent confining potential in an equally mixed scalar-vector harmonic form. We first compute the mass spectra of the ground-state-mesons and fix the model parameters necessary for the present analysis. Using the meson wave functions derivable in the RIQ model, and model parameters so fixed from hadron spectroscopy, we predict the decay constants: $f_{P(V)}$, ratios of decay constants: $f_V/f_P$, $f_{P_1}/f_{P_2}$, $f_{V_1}/f_{V_2}$, and the branching fractions (BFs): $\mathcal{B}(P(V)\to l^{+}{\nu }_l)$, $l=e$, $\mu$, $\tau$, which agree with the available experimental data and other Standard Model (SM) predictions. For the unmeasured decay constants, especially in the purely leptonic decays of the charged vector mesons, our predictions could be tested in the upcoming Belle-II, SCTF, CEPC, FCC-ee, and LHCb experiments in the near future.

Based on $10.64{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data taken at center-of-mass energies between 4.237 and 4.699 GeV with the BESIII detector, we study the leptonic $D_s^{+}$ decays using the $e^{+}{e}^{-}\to D_s^{*+}{D}_s^{*-}$ process. The branching fractions of $D_s^{+}\to {\ell }^{+}{\nu }_{\ell }(\ell =\mu ,\tau )$ are measured to be ${\mathcal{B}}_{D_s^{+}\to {\mu }^{+}{\nu }_{\mu }}=(0.547\pm 0.026_{\mathrm{stat}}\pm 0.016_{\mathrm{syst}})\%$ and ${\mathcal{B}}_{D_s^{+}\to {\tau }^{+}{\nu }_{\tau }}=(5.60\pm 0.16_{\mathrm{stat}}\pm 0.20_{\mathrm{syst}})\%$, respectively. The product of the decay constant and Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ is determined to be $f_{D_s^{+}}|V_{cs}|=(246.5\pm {5.9}_{\mathrm{stat}}\pm {3.6}_{\mathrm{syst}}\pm {0.5}_{\text{input}}{)}_{\mu \nu }$ and $f_{D_s^{+}}|V_{cs}|=(252.7\pm {3.6}_{\mathrm{stat}}\pm {4.5}_{\mathrm{syst}}\pm {0.6}_{\text{input}}{)}_{\tau \nu }\mathrm{MeV}$, respectively. Taking the value of $|V_{cs}|$ from a global fit in the Standard Model, we obtain $f_{D_s^{+}}=(253.2\pm {6.0}_{\mathrm{stat}}\pm {3.7}_{\mathrm{syst}}\pm {0.6}_{\text{input}}{)}_{\mu \nu }$ and $f_{D_s^{+}}=(259.6\pm {3.7}_{\mathrm{stat}}\pm {4.6}_{\mathrm{syst}}\pm {0.6}_{\text{input}}{)}_{\tau \nu }\mathrm{MeV}$, respectively. Conversely, taking the value for $f_{D_s^{+}}$ from the latest lattice quantum chromodynamics calculation, we obtain $|V_{cs}|=(0.986\pm 0.023_{\mathrm{stat}}\pm 0.014_{\mathrm{syst}}\pm 0.003_{\text{input}}{)}_{\mu \nu }$ and $|V_{cs}|=(1.011\pm 0.014_{\mathrm{stat}}\pm 0.018_{\mathrm{syst}}\pm 0.003_{\text{input}}{)}_{\tau \nu }$, respectively.

We demonstrate that “natural inflation,” also known as “axion inflation,” can be compatible with Planck 2018 measurements of the cosmic microwave background while predicting an exponentially small tensor-to-scalar ratio, e.g., $r\sim {10}^{-15}$. The strong suppression of $r$ arises from dynamics of the radial component of the complex scalar field, whose phase is the axion. Such tiny values of $r$ remain well below the threshold for detection by CMB-S4 or Simons Observatory B-mode searches. The model is testable with the running ${\alpha }_s$ of the spectral index, which is within reach of next-generation cosmic microwave background and large-scale structure experiments, motivating the running as a primary science goal for future experiments.

We construct new Carroll strings in flat space by considering the Carroll limit of equivalent relativistic string theories at the classical level. In the limit these Carroll strings are no longer equivalent and have different degrees of freedom. This fact is due to a general phenomenon that the configuration space and canonical Lagrangians are no longer equivalent after a singular redefinition of the variables and of the parameters of the starting Lagrangians.

This paper investigates the coupling of massive fermions to gravity within the context of a non-Abelian gauge theory, utilizing the effective field theory framework for quantum gravity. Specifically, we calculate the two-loop beta function of the gauge coupling constant in a non-Abelian gauge theory, employing the one-graviton exchange approximation. Our findings reveal that gravitational corrections may lead to a nontrivial UV fixed point in the beta function of the gauge coupling constant, contingent upon the specific gauge group and the quantity of fermions involved.

The Bell-CHSH (Clauser-Horne-Shimony-Holt) inequality in the vacuum state of a relativistic scalar quantum field is analyzed. Using Weyl operators built with smeared fields localized in the Rindler wedges, the Bell-CHSH inequality is expressed in terms of the Lorentz invariant inner products of test functions. A numerical framework for these inner products is devised. Causality is also explicitly checked by a numerical evaluation of the Pauli-Jordan function. Violations of the Bell-CHSH inequality are reported for different values of the particle mass parameter.

We start this paper by concisely rederiving ModMax, which is nothing but the unique nonlinear extension of Maxwell’s equations preserving conformal and duality invariance. The merit of this new derivation is its transparency and simplicity since it is based on an approach where the elusive duality invariance is manifest. In the second part, we couple the ModMax electrodynamics to Einstein gravity with a cosmological constant together with a standard conformal scalar field, and new stationary spacetimes with dyonic charges are found. These solutions are later used as seed configurations to generate nonlinearly charged (super-)renormalizably dressed spacetimes by means of a known generating method that we extend to include any nonlinear conformal electrodynamics. We end by addressing the issue of how to generalize some of these results to include the recently studied non-Noetherian conformal scalar fields, whose equation of motion still enjoys conformal symmetry even though its action does not. It turns out that the static non-Noetherian conformally dressed black holes also become amenable to being charged by ModMax.

In this paper we study topology-changing spacetimes occurring from pointlike sources. Following an old idea of Penrose, we will opt for a non-Hausdorff model of topology change in which an initial pointlike source is “doubled” and allowed to propagate along null rays into an eventual cobordism. By appealing to recent developments in non-Hausdorff differential geometry, we will describe and evaluate gravitational actions on these topology-changing spacetimes. Motivated by analogous results for the Trousers space, we describe a sign convention for Lorentzian angles that will ensure the dampening of our non-Hausdorff topology-changing spacetimes within a two-dimensional path integral for gravity.

The response of the Moon to gravitational waves (GWs) is used by some of the proposed lunar GW detectors like the Lunar Gravitational-wave Antenna to turn the Moon into an antenna for GWs. The deep connection between the lunar internal structure, its geophysical environment, and the study of the Universe is intriguing, but given our limited understanding of the Moon today, it also makes it very difficult to predict the science potential of lunar GW detectors accurately. Lunar response models have been developed since the Apollo program, but there is evidence coming from seismic measurements during the Apollo missions that the models are not good enough and possibly underestimating the lunar GW response especially in the decihertz frequency band. In this paper, we will provide an extension of Freeman Dyson’s half-space model to include horizontally layered geologies, which allows us to carry out computationally efficient calculations of the lunar GW response above 0.1 Hz compared to the normal-mode simulations used in the past. We analyze how the results depend on the values of geometric and elastic parameters of the layered geological model, and we find that modifications of the geological model as required to explain some of the important features of the Apollo seismic observations can boost the lunar GW response.

We present the two exact solutions of the Einstein-nonlinear electrodynamics equations that generalize the Kerr-Newman solution. We determined the generalized electromagnetic potentials using the alignment between the tetrad vectors of the metric and the eigenvectors of the electromagnetic field tensor. It turns out that there are only two possible nonlinear electromagnetic generalizations of the Kerr-Newman geometry, corresponding to different electromagnetic potentials. The new solutions possess horizons and satisfy physical energy conditions such that they can represent black holes with nonlinear electromagnetic charges, characterized by the parameters of mass, angular momentum, charge, and one nonlinear parameter; the nonlinear parameter resembles the effect of a cosmological constant, negative or positive, such that the solutions are asymptotically anti–de Sitter or de Sitter. The canonical form of the electromagnetic nonlinear energy-momentum tensor is analyzed in relation with the energy conditions; it is shown that the conformal symmetry is broken by the electromagnetic nonlinear matter; the corresponding nonlinear electromagnetic Lagrangian as a function of the coordinates is presented as well.

In this paper we study propagation of the high frequency electromagnetic waves in a curved spacetime. We discuss a so-called spinoptics approach which generalizes a well-known geometric optics approximation and allows one to take into account spin-dependent corrections. A new element proposed in this work is the use of an effective action which allows one to derive spinoptics equations. This method is simpler and more transparent than the earlier proposed methods. It is explicitly covariant and can be applied to an arbitrary spacetime background. We also demonstrate how the initial value problem for the high frequency electromagnetic wave can be solved in the developed spinoptics approximation.

We show that the nonsupersymmetric anti–de Sitter (AdS) instability conjecture can point to how quantum gravity removes the initial big bang singularity, leading to a potential resolution for the past-incomplete inflationary Universe. From the constraints on the dynamics of the Universe realized as the nucleation of a thin-wall bubble mediating the decay of the nonsupersymmetric AdS vacuum, we find the critical temperature $T_c$ and the critical scale factor $a_c$ for which the Universe exists. These critical quantities are all finite and determined in terms of the parameters specifying the stringy 10D AdS vacuum solutions. Additionally, we derive the prediction of quantum gravity for $T_c$ and $a_c$ relying on the inflationary observations.

Gravitational waves (GWs) induced by primordial fluctuations can be affected by the modification of the sound speed $c_{\mathrm{s}}^2$ and the equation of state parameter $w$ once the curvature fluctuations reenter the cosmological horizon. That softening can also significantly boost the production of primordial black holes (PBHs) at the mass scale where the softening arises. In this work, we consider a hypothetical softening of $w$ and $c_{\mathrm{s}}^2$ caused by a smooth crossover beyond standard model theories, for which we numerically compute the secondary induced GW considering the case of a flat scale-invariant power spectrum. We find that if the amplitude of the power spectrum is sufficiently large, the characteristic feature of the GW signal caused by the smooth crossover can be detected by future space-based gravitational wave interferometers and differentiated from the pure radiation case. At the same time, depending on the mass scale where the crossover occurs, such a scenario can have compatibility with PBHs being all the dark matter when $\mathcal{A}\sim \mathcal{O}({10}^{-3})$, with a mass function very sharply peaked around the horizon mass scale of the minimum of the sound speed. Our results show that the GW signal can be used to resolve the existing degeneracy of sharply peaked mass function caused by peaked power spectra and broad ones in the presence of softenings of $w$ and $c_{\mathrm{s}}^2$.

Numerical simulations of the Cauchy problem for self-interacting massive vector fields often face instabilities and apparent pathologies. We explicitly demonstrate that these issues, previously reported in the literature, are actually due to the breakdown of the well posedness of the initial-value problem. This is akin to shortcomings observed in scalar-tensor theories when derivative self-interactions are included. Building on previous work done for $k$-essence, we characterize the well-posedness breakdowns, differentiating between Tricomi- and Keldysh-like behaviors. We show that these issues can be avoided by “fixing the equations,” enabling stable numerical evolutions in spherical symmetry. Additionally, we show that, for a class of vector self-interactions, no Tricomi-type breakdown takes place. Finally, we investigate initial configurations for the massive vector field which lead to gravitational collapse and the formation of black holes.

Compact objects observed via gravitational waves are classified as black holes or neutron stars primarily based on their inferred mass with respect to stellar evolution expectations. However, astrophysical expectations for the lowest mass range, $\lesssim 1.2M_{\odot }$, are uncertain. If such low-mass compact objects exist, ground-based gravitational wave detectors may observe them in binary mergers. Lacking astrophysical expectations for classifying such observations, we go beyond the mass and explore the role of tidal effects. We evaluate how combined mass and tidal inference can inform whether each binary component is a black hole or a neutron star based on consistency with the supranuclear-density equation of state. Low-mass neutron stars experience a large tidal deformation; its observational identification (or lack thereof) can therefore aid in determining the nature of the binary components. Using simulated data, we find that the presence of a sub-solar mass neutron star (black hole) can be established with odds $\sim 100:1$ when two neutron stars (black holes) merge and emit gravitational waves at signal-to-noise ratio $\sim 20$. For the same systems, the absence of a black hole (neutron star) can be established with odds $\sim 10:1$. For mixed neutron star-black hole binaries, we can establish that the system contains a neutron star with odds $\gtrsim 5:1$. Establishing the presence of a black hole in mixed neutron star-black hole binaries is more challenging, except for the case of a $\lesssim 1M_{\odot }$ black hole with a $\gtrsim 1M_{\odot }$ neutron star companion. On the other hand, classifying each individual binary component suffers from an inherent labeling ambiguity.

The Crab Nebula, also known as Tau A, is a polarized astronomical source at millimeter wavelengths. It has been used as a stable light source for polarization angle calibration in millimeter-wave astronomy. However, it is known that its intensity and polarization vary as a function of time at a variety of wavelengths. Thus, it is of interest to verify the stability of the millimeter-wave polarization. If detected, polarization variability may be used to better understand the dynamics of Tau A, and for understanding the validity of Tau A as a calibrator. One intriguing application of such observation is to use it for the search of axionlike particles (ALPs). Ultralight ALPs couple to photons through a Chern-Simons term, and induce a temporal oscillation in the polarization angle of linearly polarized sources. After assessing a number of systematic errors and testing for internal consistency, we evaluate the variability of the polarization angle of the Crab Nebula using 2015 and 2016 observations with the 150 GHz Polarbear instrument. We place a median 95% upper bound of polarization oscillation amplitude $A<0.065°$ over the oscillation frequencies from $0.75{\mathrm{year}}^{-1}$ to $0.66{\mathrm{hour}}^{-1}$. Assuming that no sources other than ALP are causing Tau A’s polarization angle variation, that the ALP constitutes all the dark matter, and that the ALP field is a stochastic Gaussian field, this bound translates into a median 95% upper bound of ALP-photon coupling $g_{a\gamma \gamma }<2.16\times {10}^{-12}{\mathrm{GeV}}^{-1}\times (m_a/{10}^{-21}\mathrm{eV})$ in the mass range from $9.9\times {10}^{-23}\mathrm{eV}$ to $7.7\times {10}^{-19}\mathrm{eV}$. This demonstrates that this type of analysis using bright polarized sources is as competitive as those using the polarization of cosmic microwave background in constraining ALPs.

Resolving the formation channel(s) of merging binary black holes is a key goal in gravitational-wave astronomy. The orbital eccentricity is believed to be a precious tracer of the underlying formation pathway, but is largely dissipated during the usually long inspiral between black hole formation and merger. Most gravitational-wave sources are thus expected to enter the sensitivity windows of current detectors on configurations that are compatible with quasicircular orbits. In this paper, we investigate the impact of “negligible” residual eccentricity—lower than currently detectable by infer the formation history of binary black holes, focusing in particular on their spin orientations. We trace the evolution of both observed and synthetic gravitational-wave events backward in time, while resampling their residual eccentricities to values that are below the detectability threshold. Eccentricities in-band as low as $\sim {10}^{-4}$ can lead to significant biases when reconstructing the spin directions, especially in the case of loud, highly precessing systems. Residual eccentricity thus act like a systematic uncertainty for our astrophysical inference. As a mitigation strategy, one can marginalize the posterior distribution over the residual eccentricity using astrophysical predictions.