Motivated by the LHCb’s very recent observation of exotic $X_0(2900)$ in the $B^{+}\to D^{+}{D}^{-}{K}^{+}$ process, for which could be a good open-charm $ud\overline{c}\overline{s}$ tetraquark candidate, we endeavor to investigate its possibility by means of QCD sum rules. In technique, four configurations of interpolating currents with $J^P=0^{+}$ are studied for the $ud\overline{c}\overline{s}$ tetraquark state. In the end, mass values are calculated to be ${2.76}_{-0.23}^{+0.16}\mathrm{GeV}$ for the axial vector diquark-axial vector antidiquark configuration and ${2.75}_{-0.24}^{+0.15}\mathrm{GeV}$ for the scalar diquark-scalar antidiquark configuration, both of which are consistent with the experimental data $2.866\pm 0.007\pm 0.002\mathrm{GeV}$ of $X_0(2900)$ in view of the uncertainty. These results support that $X_0(2900)$ could be a $0^{+}$ tetraquark state with open-charm flavor.

We systematically study the semileptonic decays of ${\mathbf{B}}_{\mathbf{c}}\to {\mathbf{B}}_{\mathbf{n}}{\ell }^{+}{\nu }_{\ell }$ in the light-front constituent quark model, where ${\mathbf{B}}_{\mathbf{c}}$ represents the antitriplet charmed baryons of $({\mathrm{\Xi }}_c^0,{\mathrm{\Xi }}_c^{+},{\mathrm{\Lambda }}_c^{+})$ and ${\mathbf{B}}_{\mathbf{n}}$ corresponds to the octet ones. We determine the spin-flavor structures of the constituents in the baryons with the Fermi statistics and calculate the decay branching ratios ($\mathcal{B}$s) and averaged asymmetry parameters ($\alpha$s) with the helicity formalism. In particular, we find that $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{e}^{+}{\nu }_e,n{e}^{+}{\nu }_e)=(3.55\pm 1.04,0.36\pm 0.15)\%$, $\mathcal{B}({\mathrm{\Xi }}_c^{+}\to {\mathrm{\Xi }}^0{e}^{+}{\nu }_e,{\mathrm{\Sigma }}^0{e}^{+}{\nu }_e,\mathrm{\Lambda }{e}^{+}{\nu }_e)=(11.3\pm 3.35)$, $0.33\pm 0.09$, $0.12\pm 0.04\%$, and $\mathcal{B}({\mathrm{\Xi }}_c^0\to {\mathrm{\Xi }}^{-}{e}^{+}{\nu }_e,{\mathrm{\Sigma }}^{-}{e}^{+}{\nu }_e)=(3.49\pm 0.95,0.22\pm 0.06)\%$. Our results agree with the current experimental data. Our prediction for $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to n{e}^{+}{\nu }_e)$ is consistent with those in the literature, which can be measured by the charm facilities, such as BESIII and BELLE. Some of our results for the ${\mathrm{\Xi }}_c^{+(0)}$ semileptonic channels can be tested by the experiments at BELLE as well as the ongoing ones at LHCb and BELLEII.

Based on rare fluctuations in strong interactions, we argue that there is a strong physical resemblance between the high multiplicity events in photo-nuclear collisions and those in $pA$ collisions, in which interesting long range collective phenomena are discovered. This indicates that the collectivity can also be studied in certain kinematic regions of the upcoming electron-ion collider (EIC), where the incoming virtual photon has a sufficiently long lifetime. Using a model in the color glass condensate formalism, we first show that the initial state interactions can explain the recent ATLAS azimuthal correlation results measured in the photo-nuclear collisions, and then we provide quantitative predictions for the long range correlations in $eA$ collisions in the EIC regime. With the unprecedented precision and the ability to change size of the collisional system, the high luminosity EIC will open a new window to explore the physical mechanism responsible for the collective phenomenon.

We classify the constraints on a stationary point of the potential invariant under a finite group into intrinsic and extrinsic based on whether they are independent of the coefficients in the potential or not. We find that the symmetry group of a set of stationary points can be larger than that of the potential and the stabilizer under this group generates intrinsic constraints. By applying these findings in the framework of the auxiliary group, we show that the constraints that can only be obtained extrinsically in an elementary theory can be generated intrinsically in an effective theory.

Although tensor models are serious candidates for a theory of quantum gravity, a connection with classical spacetimes has been elusive thus far. I aim to fill this gap by proposing a neat connection between tensor theory and Euclidean gravity at the classical level. The main departure from the usual approach is the use of Schur invariants (instead of monomial invariants) as manifold partners. Classical spacetime features can be identified naturally on the tensor side in this new setup. A notion of locality is shown to emerge through Ward identities, where proximity between spacetime points translates into vicinity between Young diagram corners.

The epoch of reionization is one of the major phase transitions in the history of the universe, and is a focus of ongoing and upcoming cosmic microwave background (CMB) experiments with improved sensitivity to small-scale fluctuations. Reionization also represents a significant contaminant to CMB-derived cosmological parameter constraints, due to the degeneracy between the Thomson-scattering optical depth, $\tau$, and the amplitude of scalar perturbations, $A_s$. This degeneracy subsequently hinders the ability of large-scale structure data to constrain the sum of the neutrino masses, a major target for cosmology in the 2020s. In this work, we explore the kinematic Sunyaev-Zel’dovich (kSZ) effect as a probe of reionization, and show that it can be used to mitigate the optical depth degeneracy with high-sensitivity, high-resolution data from the upcoming CMB-S4 experiment. We discuss the dependence of the kSZ power spectrum on physical reionization model parameters, as well as on empirical reionization parameters, namely $\tau$ and the duration of reionization, $\mathrm{\Delta }z$. We show that by combining the kSZ two-point function and the reconstructed kSZ four-point function, degeneracies between $\tau$ and $\mathrm{\Delta }z$ can be strongly broken, yielding tight constraints on both parameters. We forecast $\sigma (\tau )=0.003$ and $\sigma (\mathrm{\Delta }z)=0.25$ for a combination of CMB-S4 and Planck data, including detailed treatment of foregrounds and atmospheric noise. The constraint on $\tau$ is nearly identical to the cosmic-variance limit that can be achieved from large-angle CMB polarization data. The kSZ effect thus promises to yield not only detailed information about the reionization epoch, but also to enable high-precision cosmological constraints on the neutrino mass.

Light dark matter (DM), defined here as having a mass between 1 MeV and about 1 GeV, is an interesting possibility both theoretically and phenomenologically, at one of the frontiers of current progress in the field of DM searches. Its indirect detection via gamma rays is challenged by the scarcity of experiments in the MeV–GeV region. We look therefore at lower-energy x-ray data from the INTEGRAL telescope, and compare them with the predicted DM flux. We derive bounds which are competitive with existing ones from other techniques. Crucially, we include the contribution from inverse Compton scattering on galactic radiation fields and the cosmic microwave background, which leads to much stronger constraints than in previous studies for DM masses above 20 MeV.

The principal aim of the space-based gravitational wave detectors is to explore the gravitational waves in the 0.1 mHz-1 Hz frequency band. To maximize the potential capability of the experimental apparatus regarding the instrument performance, one needs to acquire accurate information on its sensitivity limit. The sensitivity curve in question, by definition, depends on the amplitudes of signal and noise involved in the measurement. In this work, we explicitly derive, under rather universal assumptions irrelevant to the detailed form of the time-delay interferometry combination, general results of the sensitivity functions. The key feature of the present approach is that both the all-sky and polarization average can be factorized and henceforth evaluated analytically. The resultant expressions are then applied to a variety of time-delay interferometry combinations, inclusively for the optimal channels. In particular, the asymptotical forms of the sensitivity functions are obtained at the high and low frequency limits, and the subsequential implications are analyzed. When compared with the approaches in terms of numerical integration, the obtained formulism furnishes a more straightforward as well as efficient access to the relevant signal noise ratios for the spaceborne gravitational wave detectors.

Inspired by the observation of the $P_{cs}(4459)$ state by LHCb recently, we reexamine the results of the interaction of the $J/\psi \mathrm{\Lambda }$ channel with its coupled channels, exploiting the coupled channel unitary approach combined with heavy quark spin and local hidden gauge symmetries. By tuning the only free parameter, we find a pole of $(4459.07+i6.89)\mathrm{MeV}$ below the ${\overline{D}}^{*}{\mathrm{\Xi }}_c$ threshold, which was consistent with the mass and width of the $P_{cs}(4459)$ state. Thus, we assume the $P_{cs}(4459)$ state to be a ${\overline{D}}^{*}{\mathrm{\Xi }}_c$ bound state with the possible degeneracy of $J^P={\frac{1}{2}}^{-}$ and $J^P={\frac{3}{2}}^{-}$. According to this degeneracy, it would have a two-pole structure, like $P_c(4450)$ before. There is another pole in the $J^P={\frac{1}{2}}^{-}$ sector, $(4310.53+i8.23)\mathrm{MeV}$, corresponding to a deep bound state of $\overline{D}{\mathrm{\Xi }}_c$. Furthermore, the previously predicted loosely bound states $\overline{D}{\mathrm{\Xi }}_c^{\prime }$, ${\overline{D}}^{*}{\mathrm{\Xi }}_c^{\prime }$, ${\overline{D}}^{*}{\mathrm{\Xi }}_c^{*}$ with $J=1/2,I=0$ and ${\overline{D}}^{*}{\mathrm{\Xi }}_c^{\prime }$, $\overline{D}{\mathrm{\Xi }}_c^{*}$, ${\overline{D}}^{*}{\mathrm{\Xi }}_c^{*}$ with $J=3/2,I=0$ may exist as either bound states or unbound virtual states. We hope that future experiments can search for the ${\overline{D}}^{(*)}{\mathrm{\Xi }}_c$ molecular states not only in their dominant decay channels ${\overline{D}}_s^{(*)}{\mathrm{\Lambda }}_c$, but also in the channels $J/\psi \mathrm{\Lambda }$ and ${\eta }_c\mathrm{\Lambda }$ in order to reveal their different natures.

We present a comparison of existing experimental data for the radiative leptonic decays $P\to \ell {\nu }_{\ell }\gamma$, where $P=K$ or $\pi$ and $\ell =e$ or $\mu$, from the KLOE, PIBETA, E787, $\mathrm{ISTRA}+$ and OKA collaborations with theoretical predictions based on the recent non-perturbative determinations of the structure-dependent vector and axial-vector form factors, $F_V$ and $F_A$ respectively. These were obtained using lattice $\mathrm{QCD}+\mathrm{QED}$ simulations at order $O({\alpha }_{\mathrm{em}})$ in the electromagnetic coupling. We find good agreement with the KLOE data on $K\to e{\nu }_e\gamma$ decays from which the form factor $F^{+}=F_V+F_A$ can be determined. For $K\to \mu {\nu }_{\mu }\gamma$ decays we observe differences of up to –34 standard deviations at large photon energies between the theoretical predictions and the data from the E787, $\mathrm{ISTRA}+$ and OKA experiments and similar discrepancies in some kinematical regions with the PIBETA experiment on radiative pion decays. A global study of all the kaon-decay data within the Standard Model results in a poor fit, largely because at large photon energies the KLOE and E787 data cannot be reproduced simultaneously in terms of the same form factor $F^{+}$. The discrepancy between the theoretical and experimental values of the form factor $F^{-}=F_V-F_A$ is even more pronounced. These observations motivate future improvements of both the theoretical and experimental determinations of the structure-dependent form factors $F^{+}$ and $F^{-}$, as well as further theoretical investigations of models of “new physics” which might for example, include possible flavor changing interactions beyond $V-A$ and/or nonuniversal corrections to the lepton couplings.

We study the multiplicity distributions of events with hard jets in proton-proton collisions at LHC energies using pythia 8 Monte-Carlo simulations. We demonstrate that the charged-hadron multiplicity distributions scale with jet momentum. This suggests that the Koba–Nielsen–Olesen (KNO) scaling holds within a jet. The in-jet scaling is fulfilled without multiple-parton interactions (MPI), but breaks down in case MPI is present without color reconnection. Our findings imply that KNO scaling is violated by parton shower or multiple-parton interactions in higher-energy collisions.

We study the consequences of high-energy collider data on the best fits to total, elastic, and inelastic cross sections for $pp$ and $p\overline{p}$ scattering using two very distinct unitarization schemes: the eikonal and the $U$-matrix. Despite their analytic differences, we find that the two schemes lead to almost identical predictions up to EeV energies, with differences only becoming significant at GUT-scale and higher energies.

We calculate the mass of the vector meson in the chiral symmetry restored vacuum. This is accomplished by separating the four-quark operators appearing in the vector and axial vector meson sum rules into chiral symmetric and symmetry breaking parts depending on the contribution of the fermion zero modes. We then identify each part from the fit to the vector and axial vector meson masses. By taking the chiral symmetry breaking part to be zero while keeping the symmetric operators to the vacuum value, we find that the chiral symmetric part of the vector and axial vector meson mass is between 550 and 600 MeV. This demonstrates that chiral symmetry breaking, while responsible for the mass difference between chiral partners, accounts only for a small fraction of the symmetric part of the mass.

We study the leading ${\alpha }^{\prime }$ corrections to the entropy of certain black holes with ${\mathrm{AdS}}_5\times S^5$ asymptotics. We find that, in the supersymmetric limit, the entropy does not receive ${\alpha }^{\prime }$ corrections. This result strengthens recent calculations that match the index of $\mathcal{N}=4$ super-Yang-Mills with the corresponding partition function in the supersymmetric limit. In the small temperature regime, we find that the entropy corrections are concordant with the weak gravity conjecture.

We study the vacuum fluctuations of a quantum scalar field in the presence of a thin and inhomogeneous flat mirror, modeled with a delta potential. Using heat-kernel techniques, we evaluate the Euclidean effective action perturbatively in the inhomogeneities (nonperturbatively in the constant background). We show that the divergences can be absorbed into a local counterterm and that the remaining finite part is in general a nonlocal functional of the inhomogeneities, which we compute explicitly for massless fields in $D=4$ dimensions. For time-independent inhomogeneities, the effective action gives the Casimir self-energy for a partially transmitting mirror. For time-dependent inhomogeneities, the Wick-rotated effective action gives the probability of particle creation due to the dynamical Casimir effect.

We obtain the shadow cast induced by the rotating black hole with an anisotropic matter. A Killing tensor representing the hidden symmetry is derived explicitly. The existence of a separability structure implies complete integrability of the geodesic motion. We analyze an effective potential around the unstable circular photon orbits to show that one side of the black hole is brighter than the other side. Further, it is shown that the inclusion of the anisotropic matter ($K{r}^{2(1-w)}$) has an effect on the observables of the shadow cast. The shadow observables include approximate shadow radius $R_s$, distortion parameter ${\delta }_s$, area of the shadow $A_s$, and oblateness $D_{os}$.

We numerically investigate the validity of recent modifications of the Penrose inequality that include angular momentum. Formulations expressed in terms of asymptotic mass and asymptotic angular momentum are contradicted. We analyze numerical solutions describing polytropic stationary toroids around spinning black holes.

Even though black hole scalarization has been extensively studied recently, little has been done in the direction of understanding the dynamics of this process, especially in the rapidly rotating regime. In the present paper, we focus exactly on this problem by considering the nonlinear dynamics of the scalar field while neglecting the backreaction on the spacetime metric. This approach has proven to give good results in various scenarios and we have explicitly demonstrated its accuracy for nonrotating black holes especially close to the bifurcation point. We have followed the evolution of a black hole from a small initial perturbation, throughout the exponential growth of the scalar field followed by a subsequent saturation to an equilibrium configuration. As expected, even though the emitted signal and the time required to scalarize the black hole are dependent on the initial perturbation, the final stationary state that is reached is independent on the initial data.

We develop new strategies to build numerical relativity surrogate models for eccentric binary black hole systems, which are expected to play an increasingly important role in current and future gravitational-wave detectors. We introduce a new surrogate waveform model, NRSur2dq1Ecc, using 47 nonspinning, equal-mass waveforms with eccentricities up to 0.2 when measured at a reference time of $5500M$ before merger. This is the first waveform model that is directly trained on eccentric numerical relativity simulations and does not require that the binary circularizes before merger. The model includes the (2,2), (3,2), and (4,4) spin-weighted spherical harmonic modes. We also build a final black hole model, NRSur2dq1EccRemnant, which models the mass, and spin of the remnant black hole. We show that our waveform model can accurately predict numerical relativity waveforms with mismatches $\approx {10}^{-3}$, while the remnant model can recover the final mass and dimensionless spin with absolute errors smaller than $\approx 5\times {10}^{-4}M$ and $\approx 2\times {10}^{-3}$ respectively. We demonstrate that the waveform model can also recover subtle effects like mode mixing in the ringdown signal without any special ad hoc modeling steps. Finally, we show that despite being trained only on equal-mass binaries, NRSur2dq1Ecc can be reasonably extended up to mass ratio $q\approx 3$ with mismatches $\simeq {10}^{-2}$ for eccentricities smaller than $\sim 0.05$ as measured at a reference time of $2000M$ before merger. The methods developed here should prove useful in the building of future eccentric surrogate models over larger regions of the parameter space.

The standard theoretical description $\mathrm{\Theta }(\widehat{n})$ of the observed cosmic microwave background (CMB) temperature anisotropies is gauge dependent. It is, however, well known that the gauge mode is limited to the monopole and that the higher angular multipoles ${\mathrm{\Theta }}_l$ ($l\ge 1$) are gauge invariant. Several attempts have been made in the past to properly define the monopole fluctuation, but the resulting values of the monopole power $C_0$ are infinite due to the infrared divergences. The infrared divergences arise from the contribution of the uniform gravitational potential to the monopole fluctuation, in violation of the equivalence principle. Here we present the gauge-invariant theoretical description of the observed CMB temperature anisotropies and compute the monopole power $C_0=1.66\times {10}^{-9}$ in a $\mathrm{\Lambda }\mathrm{CDM}$ model. While the gauge dependence in the standard calculations originates from the ambiguity in defining the hypersurface for the background CMB temperature $\overline{T}$ today, it is in fact well defined and one of the fundamental cosmological parameters. We argue that once the cosmological parameters are chosen, the monopole fluctuation can be unambiguously inferred from the angle average of the observed CMB temperature, making it a model-dependent “observable.” Adopting simple approximations for the anisotropy formation, we derive a gauge-invariant analytical expression for the observed CMB temperature anisotropies to study the CMB monopole fluctuation and the cancellation of the uniform gravitational potential contributions on large scales.