We study junctions between confining strings. We show that the effective theory of such junctions is very predictive, with only one new parameter, the junction’s mass, controlling the first couple of terms in the expansion in the system size. By open-closed string duality, these considerations about the baryon junction map to interaction vertices of closed strings. Therefore, we calculate the interaction vertices of closed strings in theories such as Yang-Mills theory. We find some surprising selection rules for string interactions in $3+1$ dimensions. Requiring perturbative stability and that the string coupling is weak, we suggest constraints on the junction’s mass.

In the present paper, we study the properties of $\varphi$-meson longitudinal leading-twist light-cone distribution amplitude ${\varphi }_{2;\varphi }^{\parallel }(x,\mu )$ by starting from a light-cone harmonic oscillator model for its wave function. To fix the input parameters, we derive the first ten order $\xi$ moments of ${\varphi }_{2;\varphi }^{\parallel }(x,\mu )$ by using the QCD sum rules approach under the background field theory. The curves of ${\varphi }_{2;\varphi }^{\parallel }(x,\mu =2\mathrm{GeV})$ tend to be a single-peak behavior, which is consistent with the latest lattice QCD result. To show how the twist-3 light-cone distribution amplitudes (LCDAs) affect the results, we consider two scenarios for the $\varphi$-meson chiral twist-3 LCDAs ${\varphi }_{3;\varphi }^{\perp }(x)$ and ${\psi }_{3;\varphi }^{\perp }(x)$, i.e., the ones using the Wandzura-Wilczek approximation with ${\varphi }_{2;\varphi }^{\parallel }(x,\mu )$ (S1) and the ones using self-consistent conformal expansion with second-order Gegenbauer moments $a_{2;\varphi }^2$ in this work (S2). As an application, we derive the $D_s^{+}\to \varphi$ transition form factors (TFFs) by using the QCD light-cone sum rules. The TFFs at large recoil point for those two scenarios are given separately. As for the two TFF ratios ${\gamma }_V$ and ${\gamma }_2$, we obtain ${\gamma }_V^{(\mathrm{S}1)}=1.755_{-0.005}^{+0.008}$, ${\gamma }_2^{(\mathrm{S}1)}=0.852_{-0.133}^{+0.135}$, ${\gamma }_V^{(\mathrm{S}2)}=1.723_{-0.021}^{+0.023}$, and ${\gamma }_2^{(\mathrm{S}2)}=0.785_{-0.104}^{+0.100}$. After extrapolating those TFFs to the physically allowable region, we then obtain the transverse, longitudinal, and total decay widths for semileptonic decay $D_s^{+}\to \varphi {\ell }^{+}{\nu }_{\ell }$. Then the branching fractions are ${\mathcal{B}}^{(\mathrm{S}1)}(D_s^{+}\to \varphi e^{+}{\nu }_e)=(2.347_{-0.191}^{+0.342})\times {10}^{-3}$, ${\mathcal{B}}^{(\mathrm{S}1)}(D_s^{+}\to \varphi {\mu }^{+}{\nu }_{\mu })=(2.330_{-0.190}^{+0.341})\times {10}^{-3}$, ${\mathcal{B}}^{(\mathrm{S}2)}(D_s^{+}\to \varphi e^{+}{\nu }_e)=(2.367_{-0.132}^{+0.256})\times {10}^{-3}$, and ${\mathcal{B}}^{(\mathrm{S}2)}(D_s^{+}\to \varphi {\mu }^{+}{\nu }_{\mu })=(2.349_{-0.132}^{+0.255})\times {10}^{-3}$, which show good agreement with the data issued by the BESIII, CLEO, and BABAR Collaborations. We finally calculate $D_s^{+}\to \varphi {\ell }^{+}{\nu }_{\ell }$ polarization and asymmetry parameters, which can be measured and tested in future experiments.

The production of single and paired lepton bound states in the decay of the Higgs boson has been studied. We explore different decay mechanisms that contribute significantly to the decay width. The decay widths are calculated taking into account relativistic corrections in the decay amplitude and in the wave function of the bound state of leptons.

In this work, we study the effects of random temperature fluctuations on the partition function of a quantum system by means of the replica method. This picture provides a conceptual model for a quantum nonequilibrium system, depicted as an ensemble of subsystems at different temperatures, randomly distributed with respect to a given mean value. We then assume the temperature displays stochastic fluctuations $T=T_0+\delta T$ with respect to its ensemble average value $T_0$, with zero mean $\overline{\delta T}=0$ and standard deviation $\overline{\delta T^2}=\mathrm{\Delta }$. By means of the replica method, we obtain the average grand canonical potential, leading to the equation of state and the corresponding excess pressure caused by these fluctuations with respect to the equilibrium system at a uniform temperature. Our findings reveal an increase in pressure as the system’s ensemble average temperature $T_0$ rises, consistently exceeding the pressure observed in an equilibrium state. We applied our general formalism to three paradigmatic physical systems; the relativistic Fermi gas, the ideal gas of photons, and a gas of non-Abelian gauge fields (gluons) in the noninteracting limit. Finally, we explore the implications for the deconfinement transition in the context of the simple bag model, where we show that the critical temperature decreases.

In a previous paper [H. Raj and R. Venugopalan, Phys. Rev. D 109, 044064 (2024)], we demonstrated a double-copy relation between inclusive gluon radiation in shock wave collisions of ultrarelativistic nuclei and inclusive graviton radiation in trans-Planckian gravitational shock wave collisions. We compute here the corresponding gravitational shock wave propagators in general relativity and demonstrate that they too obey a double-copy relation to gluon shock wave propagators computed previously. These results provide key input in a renormalization group approach toward computing the high frequency radiation spectrum in close black hole encounters.

We study the decay of $B^{+}$ meson into $K^{+}$ plus a light mediator $\varphi$, which subsequently decays into a dark matter pair, $\overline{\chi }\chi$. Integrating constraints from DM relic density, direct detection, collider data and $B$-physics, alongside the recently reported results form Belle II experiment, we analyze the couplings between the mediator, standard model fermions, and the dark matter particles. Our results indicate that if the decay process $\varphi \to \overline{\chi }\chi$ is kinematically allowed, i.e., $m_{\varphi }>2m_{\chi }$, then the mediator mass must be constrained within $0.35\mathrm{GeV}\lesssim m_{\varphi }\lesssim 3\mathrm{GeV}$. Conversely, if $m_{\varphi }<2m_{\chi }$, the mediator $m_{\varphi }$ is long-lived relative to the detector size, and the only allowed decay channel is $\varphi \to e^{+}{e}^{-}$.

To maximize the discovery potential of high-energy colliders, experimental searches should be sensitive to unforeseen new physics scenarios. This goal has motivated the use of machine learning for unsupervised anomaly detection. In this paper, we introduce a new anomaly detection strategy called force: factorized observables for regressing conditional expectations. Our approach is based on the inductive bias of factorization, which is the idea that the physics governing different energy scales can be treated as approximately independent. Assuming factorization holds separately for signal and background processes, the appearance of nontrivial correlations between low- and high-energy observables is a robust indicator of new physics. Under the most restrictive form of factorization, a machine-learned model trained to identify such correlations will in fact converge to the optimal new physics classifier. We test force on a benchmark anomaly detection task for the Large Hadron Collider involving collimated sprays of particles called jets. By teasing out correlations between the kinematics and substructure of jets, our method can reliably extract percent-level signal fractions. This strategy for uncovering new physics adds to the growing toolbox of anomaly detection methods for collider physics with a complementary set of assumptions.

We introduce a block encoding method for mapping discrete subgroups to qubits on a quantum computer. This method is applicable to general discrete groups, including crystal-like subgroups such as $\mathbb{BI}$ of $SU(2)$ and $\mathbb{V}$ of $SU(3)$. We detail the construction of primitive gates—the inversion gate, the group multiplication gate, the trace gate, and the group Fourier gate—utilizing this encoding method for $\mathbb{BT}$ and for the first time $\mathbb{BI}$ group. We also provide resource estimations to extract the gluon viscosity. The inversion gates for $\mathbb{BT}$ and $\mathbb{BI}$ are benchmarked on the Baiwang quantum computer with estimated fidelities of ${40}_{-4}^{+5}\%$ and $4_{-3}^{+5}\%$, respectively.

We use the leading-order contact interactions and one-pion-exchange potentials to investigate the newly observed double-charm state $T_{cc}^{+}$. We employ the complex scaling method to search for the poles on the first Riemann sheet with respect to the $D{D}^{*}$ threshold and the second Riemann sheet with respect to the $DD\pi$ threshold. The $DD\pi$ three-body effect is important in this system since the intermediate states can go on shell. We involve the three-body effect through an energy-dependent one-pion-exchange potential, which results in a unitary cut at the $DD\pi$ three-body threshold. We find a pole corresponding to the $T_{cc}^{+}$ on the physical Riemann sheet. Its width is around 80 keV and nearly independent of the choice of the cutoff. Assuming the $D\overline{D}\pi$ and $D{\overline{D}}^{*}$ channels as the main decay channels, we apply the similar calculations to the ${\chi }_{c1}(3872)$, and find its width is even smaller. The isospin breaking effect is so significant for the ${\chi }_{c1}(3872)$ that it is mainly a molecular state of $D^0{\overline{D}}^{*0}$. Furthermore, we introduce a revised Schrödinger equation for unstable particles to include the contribution of the $D^{*}$ width, which is also revised by the three-body effect.

In this study, we reconsider the states $Z_b(10610)$ and $Z_b(10650)$ by investigating the presence of diquark-anti-diquark components as well as the hadronic molecule components in the framework of effective field theory. The different masses of pseudoscalar mesons such as ${\pi }^0$, ${\eta }_8$, and ${\eta }_0$, as well as vector mesons like ${\rho }^0$ and $\omega$ violate the Okubo-Zweig-Iizuka (OZI) rule that is well depicted under the $[U(3{)}_L\otimes U(3{)}_R{]}_{\text{global}}\otimes [U(3{)}_V{]}_{\text{local}}$ symmetry. To account for the contribution of intermediate bosons of heavy masses within the one-boson-exchange model, we introduce an exponential form factor instead of the commonly used monopole form factor in the past. By solving the coupled-channel Schrödinger equation with the Gaussian expansion method, our numerical results indicate that the $Z_b(10610)$ and $Z_b(10650)$ states can be explained as hadronic molecules slightly mixing with diquark-anti-diquark states.

We study energy-momentum and charge transport in strongly interacting holographic quantum field theories in an anisotropic thermal state by contrasting three different holographic methods to compute transport coefficients: standard holographic calculation of retarded Green’s functions, a method based on the null-focusing equation near horizon and the novel method based on background variations. Employing these methods we compute anisotropic shear and bulk viscosities and conductivities with anisotropy induced externally, for example by an external magnetic field. We show that all three methods yield consistent results. The novel method allows us to read off the transport coefficients from the horizon data and express them in analytic form from which we derive universal relations among them. Furthermore we extend the method based on the null-focusing equation to Gauss-Bonnet theory to compute higher derivative corrections to the aforementioned transport coefficients.

We investigate the dynamics of spin-$\frac{1}{2}$ particles that are freely propagating in superposed states in curved spacetime. We first make use of a Wentzel-Kramers-Brillouin approximation of the Dirac equation in curved spacetime to extract the corresponding Mathisson-Papapetrou-Dixon equations that describe the deviation from geodesic motion as well as the spin precession of such particles. We then discuss, in light of our results, the case of flavor neutrinos which are, by nature, a superposition of mass eigenstates.

We find a spectral wall in collisions of two vortices in the Abelian Higgs model at the critical coupling. It occurs if the out-of-phase mode of initially separated vortices is excited.

All physical observations are made relative to a reference frame, which is a system in its own right. If the system of interest admits a group symmetry, the reference frame observing it must transform commensurately under the group to ensure the covariance of the combined system. We point out that the crossed product is a way to realize quantum reference frames from the bottom-up; adjoining a quantum reference frame and imposing constraints generates a crossed product algebra. We provide a top-down specification of crossed product algebras and show that one cannot obtain inequivalent quantum reference frames using this approach. As a remedy, we define an abstract algebra associated to the system and symmetry group built out of relational crossed product algebras associated with different choices of quantum reference frames. We term this object the $G$-framed algebra, and show how potentially inequivalent frames are realized within this object. We comment on this algebra’s analog of the classical Gribov problem in gauge theory, its importance in gravity where we show that it is relevant for semiclassical de Sitter and potentially beyond the semiclassical limit, and its utility for understanding the frame dependence of physical notions like observables, density states, and entropies.

The gravitational waves emitted in the ringdown phase of binary black hole coalescence are a unique probe of strong gravity. At late times in the ringdown, these waves can be described by quasinormal modes, whose frequencies encode the mass and spin of the remnant, as well as the theory of gravity in play. Understanding precisely how deviations from general relativity affect the quasinormal mode frequencies of ringing black holes, however, is extremely challenging, as it requires solving highly coupled and sometimes higher-order partial differential equations. We here extend a novel approach, metric perturbations with spectral methods (METRICS), to study the gravitational metric perturbations and the quasinormal mode frequencies of ringing black holes in modified gravity. We first derive the asymptotic behavior of gravitational perturbations at the event horizon and spatial infinity for rotating black holes beyond general relativity. We then extend the eigenvalue-perturbation theory approach of METRICS to allow us to compute the leading-order beyond general relativity corrections to the quasinormal-mode frequencies and metric perturbations. As an example, we apply METRICS to black holes with moderate spins in scalar-Gauss-Bonnet gravity. Without decoupling or simplifying the linearized field equations in this theory, we compute the leading-order corrections to the quasinormal frequencies of the axial and polar perturbations of the $nlm=022$, 021, and 033 modes of black holes with dimensionless spin $a\le 0.85$. The numerical accuracy of the METRICS frequencies is $\le {10}^{-5}$ when $a\le 0.6$, $\lesssim {10}^{-4}$ when $0.6<a\le 0.7$, and $\lesssim {10}^{-2}$ when $0.7<a\le 0.85$ for all modes studied. We fit the frequencies with a polynomial in spin, whose coefficients (up to second order in spin) are consistent with those obtained in previous slow-rotating approximations. These results are the first accurate computations of the gravitational quasinormal-mode frequencies of rapidly rotating black holes (of $a\sim 0.85$) in scalar-Gauss-Bonnet gravity.

We investigate the prospect of probing massive fields and testing gravitational theories with multiband observations of gravitational waves emitted from coalescing compact binaries. Focusing on the dipole radiation induced by a massive field, we show that multiband observations can probe the field with mass ranging from ${10}^{-16}$ to ${10}^{-15}\mathrm{eV}$, a parameter space that cannot be probed by the millihertz band observations alone. Multiband observations can also improve the constraints obtained with the LIGO-Virgo-KAGRA binaries by at most 3 orders of magnitude in the mass range. Moreover, we show that multiband observations can discriminate the spin of the field, which cannot be identified with single-band observations.

The Event Horizon Telescope (EHT) has captured a series of images of black holes. These images could provide valuable information about the gravitational environment near the event horizon. However, accurate detection and parameter estimation for candidate black holes are necessary. This paper explores the potential for identifying black holes in the ultraviolet band using space telescopes. We establish a data pipeline for generating simulated observations and present an ensemble neural network model for black hole detection and parameter estimation. For detection tasks, the model achieves mean average precision [0.5] values of 0.9176 even when reaching the imaging full width half maximum (FWHM) (${\theta }_c$) and maintains the detection ability until $0.54{\theta }_c$. For parameter estimation tasks, the model can accurately recover the inclination, position angle, accretion disk temperature and black hole mass. These results indicate that our methodology can go beyond the limits of the traditional Rayleigh diffraction limit and enable superresolution recognition. Moreover, the model successfully detects the shadow of M87* from background noise and other celestial bodies, and estimates its inclination and position angle. Our work demonstrates the feasibility of detecting black holes in the ultraviolet band and provides a new method for black hole detection and further parameter estimation.

We have upgraded the MSNRnet framework to MSNRnet-2 by refining the training strategy, drawing inspiration from generative adversarial networks for data generation. The astrophysical discrimination network enforces constraints on the denoising output, ensuring that the “$\mathrm{signal}+\mathrm{noise}$” case conforms to an astrophysical-origin shape, while limiting the denoised output of the “noise” case to a nonastrophysical origin shape. This improvement has led to enhanced denoising and astrophysical discrimination performance in most scenarios. For the analysis of confident events, we observed a 1.3% increase in the detection rate. Remarkably, no false triggers were generated during the analysis of the data jointly processed by the Hanford and Livingston interferometers in O3b (about five months of data). These findings suggest that the denoising-discrimination-matched filtering framework holds promising potential for gravitational wave searches in the future.

The homogeneous Bethe-Salpeter equation (hBSE), describing a bound system in a genuinely relativistic quantum-field theory framework, was solved for the first time by using a D-Wave quantum annealer. After applying standard techniques of discretization, the hBSE, in ladder approximation, can be formally transformed in a generalized eigenvalue problem (GEVP), with two square matrices: one symmetric and the other nonsymmetric. The latter matrix poses the challenge of obtaining a suitable formal approach for investigating the nonsymmetric GEVP by means of a quantum annealer, i.e., to recast it as a quadratic unconstrained binary optimization problem. A broad numerical analysis of the proposed algorithms, applied to matrices of dimension up to 64, was carried out by using both the proprietary simulated-annealing package and the D-Wave Advantage 4.1 system. The numerical results very nicely compare with those obtained with standard classical algorithms, and also show interesting scalability features.

We compute three-loop corrections of $\mathcal{O}({\alpha }_s^3)$ to form factors with one massive and one massless quark coupling to an external vector, axialvector, scalar, pseudoscalar, or tensor current. We obtain analytic results for the color-planar contributions, for the contributions of light-quark loops, and the contributions with two heavy-quark loops. For the computation of the remaining master integrals we use the “expand and match” approach which leads to semianalytic results for the form factors. We implement our results in a Mathematica and a fortran code which allows for fast and precise numerical evaluations in the physically relevant phase space. The form factors are used to compute the hard matching coefficients in Soft-Collinear Effective Theory for all currents. The tensor coefficients at lightlike momentum transfer are used to extract the hard function in $\overline{B}\to X_s\gamma$ to three loops.