In $D$ dimensional de Sitter space, a scalar field has an infinite tower of special tachyonic mass values at which enhanced shift symmetries appear. After modding out by these shift symmetries, these fields correspond to the unitary irreducible representations of the de Sitter group known as the discrete series. We show that in $D=2$ these theories have global conformal symmetry. In all but the massless case, these theories have no stress tensor and the conformal symmetry does not act in the usual way on the scalar field. We find the conformal symmetry by explicitly computing the correlators of the shift invariant local operators and showing that they take conformally invariant forms. We also demonstrate how these fields are self-dual in $D=2$, and dual to the shift invariant massive vector fields, which are therefore also conformally invariant.

We examine the geometry of a generalized uncertainty-inspired quantum black hole. The diagonal line element is not $t\text{−}r$ symmetric, i.e., $g_{00}\ne -1/g_{11}$, which leads to an interesting approach to resolving the classical curvature singularity. In this paper, we show, in Schwarzschild coordinates, that the $r=0$ coordinate location is a null surface which is not a transition surface or leads to a black bounce. We find the expansion of null geodesic congruences in the interior turn around then vanishes at $r=0$, and the energy conditions are predominately violated, indicating a repulsive gravitational core. In addition, we show that the line element admits a wormhole solution which is not traversable, and the black hole at its vanishing horizon radius could be interpreted as a remnant.

In this paper, we construct an exact solution of the $SU(N)$ Einstein-Skyrme model in $D=4$ space-time dimensions describing a charged and rotating black hole with toroidal horizon. Rotation is added by applying an improper coordinate transformation to the known static toroidal black hole with Skyrme hair, while the electric charge is supplemented by considering a $U(1)$ gauge field interacting with Einstein gravity. We perform the thermal analysis in the grand canonical ensemble, explicitly showing the role that the flavor number plays. Some discussions about stability are also considered.

Halilsoy and Chandrasekhar cylindrical standing gravitational waves correspond to two different classes of solutions to the vacuum Einstein equations. Both families satisfy the definition of standing gravitational waves proposed by Stephani, but only the latter class fulfills the stricter definition introduced by Chandrasekhar. The aim of this research is to compare both classes of solutions within the linear regime. We discover that the linearized Halilsoy and Chandrasekhar standing waves are gravitational analogs of two different types of electromagnetic polarization standing waves.

We present a dynamical analysis of the null and timelike geodesics around an asymptotically de Sitter wormhole in a Randall-Sundrum brane. In this framework, the wormhole throat is interpreted both as a photon sphere and as a fixed point of the associated dynamical system. The stability of this structure is evaluated using Lyapunov and Jacobi criteria with consistent results. A Bogdanov-Takens bifurcation is observed in the null-geodesic dynamics, highlighting critical changes in the behavior of light around the wormhole. Explicit solutions are derived for geodesics near the throat, providing insight into the optical appearance of the wormhole shadow. These results show qualitatively similar behavior for null and timelike orbits, suggesting universal features of geodesic dynamics in brane–de Sitter wormholes.

The detection of a stochastic signal by recent pulsar timing array (PTA) collaborations, including NANOGrav, PPTA, $\mathrm{EPTA}+\mathrm{InPTA}$, CPTA, and MPTA, has opened a new window to explore gravitational waves (GWs) at nanohertz frequencies. Motivated by the possibility that such a signal could arise from primordial gravitational waves (PGWs), we investigate the implications of tensor non-Gaussianity for the PGW power spectrum. Utilizing PTA datasets, we provide constraints on the local-type tensor non-Gaussianity parameter ${\mathcal{F}}_{\mathrm{NL}}$. We find $|{\mathcal{F}}_{\mathrm{NL}}|\lesssim 7.97$ for a log-normal PGW power spectrum. Our analysis reveals that even moderate tensor non-Gaussianity can lead to significant deviations from standard predictions, thereby offering a novel means to test inflationary scenarios and probe the underlying dynamics of the early Universe. Future multiband GW observatories, such as LISA, Taiji, and TianQin, will be instrumental in complementing these efforts and further refining our understanding of tensor non-Gaussianity.

The sound horizon-independent $H_0$ extracted by using galaxy clustering surveys data through, e.g., effective field theory of large-scale structure (EFTofLSS) or ShapeFit analyses, is considered to have the potential to constrain the early new physics responsible for solving the Hubble tension. Recent observations, e.g., dark energy spectroscopic instrument, have shown that the sound horizon-independent measurement of $H_0$ is consistent with $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$). In this work, we clarify some potential misuses and misinterpretations in these analyses. On the one hand, imposing some prior from other cosmological probes is often used to strengthen the constraints on the results, however, these priors are usually derived using the assumption of $\mathrm{\Lambda }\mathrm{CDM}$, it is not suitable to apply these so-called $\mathrm{\Lambda }\mathrm{CDM}$ priors (e.g., the $n_s$ prior from cosmic microwave background (CMB)), which would bias the results, to early new physics because these early new physics are usually accompanied by shifts of the $\mathrm{\Lambda }\mathrm{CDM}$ parameters. On the other hand, the constraints on $H_0$ in the sound horizon-independent EFTofLSS analysis arise from not only the shape of the power spectrum ($k_{\mathrm{eq}}$-based $H_0$), but also the overall amplitude (when combined with CMB lensing observations) and the relative amplitudes of the baryon acoustic oscillations wiggles, thus besides $k_{\mathrm{eq}}$ other information may also play a role in constraining $H_0$. We also make forecasts for a Euclid-like survey, which suggests that ongoing observations will also have difficulty constraining early new physics.

We demonstrate that, in the presence of an external magnetic field, an uncharged classical Schwarzschild black hole moving superluminally in a dielectric with permittivity $\epsilon >1$ produces Cherenkov emission. This is a new physical effect: classical (nonquantum) emission of electromagnetic waves by a completely charge-neutral “particle.” The governing equations (involving general relativity, electromagnetism, and the physics of continuous media) have no external electromagnetic source—it is the distortion of the initial electromagnetic fields by the gravity of the black hole that plays the role of a superluminally moving source. The effect relies on nonzero values of both the magnetic field and the gravitational radius, as well as on the usual Cherenkov condition on the velocity, $v/c>1/\sqrt{\epsilon }$. Unlike Cherenkov emission by a point charge, the effective source in this case is spatially distributed, with emission generated along the single Cherenkov emission cone. The emitted spectrum is red dominated, with power $\propto d{k}_z/|k_z|$ for wave numbers $|k_z|\le 1/R_G$, where $R_G$ is the Schwarzschild radius. We comment on possible observability of this process during black hole–neutron star mergers.

The recent mass ($0.77{\pm }_{0.17}^{0.20}{M}_{\odot }$) and radius ($10.4{\pm }_{0.78}^{0.86}\mathrm{km}$) measurement of HESS J1731-347 made it one of the most fascinating object if it is indeed a neutron star. In this work, we examine the current status of the dense matter equation of states in the context of this compact object being a neutron star. We use three sets of equation of states corresponding to the three classes—neutron stars, strange stars, and hybrid stars and perform Bayesian model selection on them. Our results show that for hadronic models, the equation of state is preferred to be stiff at the intermediate densities. This makes the Brueckner-Hartree-Fock approximation and models based on effective interactions deviate from current astrophysical observations on the inclusion of HESS J1731-347. Furthermore, for the strange star family, the equation of states composed of three flavor quarks prefers relatively smaller bag parameters. Analyzing the hybrid family of equation of states consisting of a first-order phase transition revealed preferences for early first-order phase transition. Comparing all the preferred equations of state among each family, it was found that the current astrophysical constraints prefer the hybrid equation of states the most.

Extreme-mass-ratio inspirals (EMRIs), consisting of a massive black hole (MBH) and a stellar compact object, are one of the most important sources for spaceborne gravitational wave detectors like TianQin. Their population study can be used to constrain astrophysical models that interpret the EMRI formation mechanisms. In this paper, as an initial attempt, we employ a parametrization method to describe the EMRI population model in the loss cone formation channel. This approach, however, can be extended to other models, such as the accretion disc-driven formation channel. We present the phenomenological characteristic of the MBH mass, spin, and redshift distributions. Then, we investigate the posterior distribution of the hyperparameters that describe this population model. The optimistic results show that TianQin could recover almost all the posterior of the hyperparameters within a $1\sigma$ confidence interval. The hyperparameters ${\alpha }_1$, ${\alpha }_2$, and $b$, which describe the MBH mass distribution, could be measured with an accuracy of 46.4%, 12.6%, and 3%, respectively. The hyperparameters ${\mu }_z$ and ${\sigma }_z$, which describe the redshift distribution, could be measured with an accuracy of 15.4% and 21.1%. With this estimation accuracy, the EMRI population characteristics can be effectively demonstrated, potentially serving as evidence for EMRI formation in the future studies. Furthermore, with an increasing number of detectable events, the parameter estimation for the hyperparameters will improve and the confidence intervals will be narrowed.

The far-from-equilibrium dynamics of spatial Polyakov loop correlations, which provide gauge-invariant observables akin to effective particle numbers for gluon plasmas, are investigated within real-time $\mathrm{SU}(N_c)$ lattice gauge theory at weak couplings and large gluon occupations. The momentum zero mode of these correlations reveals the dynamic formation of a condensate, while at nonzero momenta, energy is transported toward the ultraviolet. We demonstrate that the nonzero momentum dynamics is well described by a direct cascade in terms of gauge-invariant Polyakov loop excitations, exhibiting self-similar prescaling indicative of a nonthermal attractor. This behavior can be analytically understood through perturbation theory for the Polyakov loop correlations and the established dynamics of gauge field correlations. We perform simulations for both SU(2) and SU(3) gauge groups, providing further consistency checks on the $N_c$ dependence of perturbative expectations. No evidence of an inverse cascade toward lower momenta is found for momenta above the electric screening scale.

In [J. High Energy Phys. 02 (2024) 158], we derived a direct expression for one-loop tensor reduction using generating functions and Feynman parametrization in projective space, avoiding recursive relations. However, for practical applications, this expression still presents two challenges: 1) while the final reduction coefficients are expressed in terms of the dimension D and Mandelstam variables, the given expression explicitly contains irrational functions; 2) the expression involves an auxiliary vector R, which can be eliminated via differentiation $\frac{\partial }{\partial R}$, but the presence of irrational terms making differentiation cumbersome; and 3) most practical applications require the tensor form with Lorentz indices. In this paper, we provide a rational form of the reduction coefficients with Lorentz indices, free from recursion. Additionally, we provide a pure Wolfram Mathematica implementation of the code. Our practical tests demonstrate that this direct expression achieves significantly higher computational efficiency compared to the traditional Passarino-Veltman reduction or other recursion-based methods.

We study the lattice Schwinger model by combining the variational uniform matrix product state (VUMPS) algorithm with a gauge-invariant matrix product ansatz that locally enforces the Gauss law constraint. Both the continuum and lattice versions of the Schwinger model with $\theta =\pi$ are known to exhibit first-order phase transitions for the values of the fermion mass above a critical value, where a second-order phase transition occurs. Our algorithm enables a precise determination of the critical point in the continuum theory. We further analyze the scaling in the simultaneous critical and continuum limits and confirm that the data collapse aligns with the Ising universality class to remarkable precision.

In our previous studies [Phys. Rev. D 108, 074501 (2023)., Proc. Sci. LATTICE2023 (2024) 219 [arXiv:2311.07209].], we confirmed that a quantum annealer can be used for importance sampling of gauge theories. In this paper, we extend the previous results to larger 2-dimensional and 4-dimensional lattices to generate ensembles for U(3) gauge theory in the strong coupling limit. We make use of the D-Wave quantum annealer to generate histograms for sublattices, and use the Metropolis-Hastings algorithm to determine thermodynamic observables and their dependence on the physical parameters on large volumes. We benchmark our results to those obtained from classical Monte Carlo simulations.

The path optimization method with machine learning is applied to the one-dimensional massive lattice Thirring model, which has the sign problem caused by the fermion determinant. This study aims to investigate how the path optimization method works for the sign problem. We show that the path optimization method successfully reduces statistical errors and reproduces the analytic results. We also examine an approximation of the Jacobian calculation in the learning process and show that it gives consistent results with those without an approximation.

The semi-inclusive deep-inelastic scattering (SIDIS) process requires the presence of an identified hadron ${\mathrm{H}}^{\prime }$ in the final state, which arises from the scattering of a lepton with an initial hadron P. By employing factorization in quantum chromodynamics (QCD), SIDIS provides essential knowledge on the hadron structure, enabling the exploration of parton distribution functions (PDFs) and fragmentation functions (FFs). The coefficient functions for SIDIS can be calculated in perturbative QCD and are currently known to the next-to-next-to-leading order (NNLO) for the cases, where the incoming lepton and the hadron P are either both polarized or unpolarized. We present a detailed description of these NNLO computations, including a thorough discussion of all the partonic channels, the calculation of the amplitudes and master integrals for the phase-space integration as well as the renormalization of ultraviolet divergences and mass factorization of infrared divergences in dimensional regularization through NNLO. We provide an extensive phenomenological analysis of the effects of NNLO corrections on SIDIS cross sections for different PDFs and FFs and various kinematics, including those of the future Electron-Ion Collider (EIC). We find that these corrections are not only significant but also crucial for reducing the dependence on the renormalization and factorization scales ${\mu }_R$ and ${\mu }_F$ to obtain stable predictions.

In a unified perturbative treatment from the high-density side, we compute the speed of sound and the trace anomaly as functions of the chemical potential $\mu$ for the two-color diquark superfluid, the pion-condensed high-isospin matter, and the two-flavor color superconducting (2SC) quark matter. We find that the corrections induced by the gap energy $\mathrm{\Delta }$ involve nontrivial interplay between the dimensionless magnitude $|\mathrm{\Delta }/\mu |$ and the derivative $|\partial \mathrm{\Delta }/\partial \mu |$. Even though the gap equation has a common structure for these phases of our interest, different numerical constants cause drastic changes in the speed of sound corrections. As long as $|\mathrm{\Delta }/\mu |$ is dominant over the derivative, the gap effects increase the speed of sound, which is consistent with the expected behavior of exhibiting a peak at intermediate density. We then discuss the trace anomaly which is pushed down generally by the gap effects and turns out to be negative widely in the high density regime. For demonstration of nonperturbative enhancement, we take account of the instanton-induced interaction. We confirm a further increase in the speed of sound for the two-color diquark superfluid and the pion-condensed high-isospin matter, while the speed of sound for the 2SC quark matter deviates far below the conformal limit due to the derivative contribution.

We present the result of a search for inelastic boosted dark matter using the data corresponding to an exposure of $0.13\mathrm{kton}·\mathrm{year}$, collected by the ICARUS T-600 detector during its 2012–2013 operational period at the INFN Gran Sasso Underground National Laboratory. The benchmark boosted dark matter model features a multiparticle dark sector with a ${\mathrm{U}(1)}^{\prime }$ gauge boson, the dark photon. The kinetic mixing of the dark photon with the Standard Model photon allows for a portal between the dark sector and the visible sector. The inelastic boosted dark matter interaction occurs when a dark matter particle inelastically scatters with an electron in the ICARUS detector, producing an outgoing, heavier dark sector state which subsequently decays back down to the dark matter particle, emitting a dark photon. The dark photon subsequently couples to a Standard Model photon through kinetic mixing. The Standard Model photon then converts to an electron-positron pair in the detector. This interaction process provides a distinct experimental signature that consists of a recoil electron from the primary interaction and an associated electron-positron pair from the secondary vertex. After analyzing 4,134 triggered events, the search results in zero observed events. Exclusion limits are set in the dark photon mass and coupling ($m_X,\epsilon$) parameter space for several selected optimal boosted dark matter mass sets and cover previously unexplored parameter space.

A search for $D^0$ meson decays to the ${\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ and $K^{+}{K}^{-}{e}^{+}{e}^{-}$ final states is reported using a sample of proton-proton collisions collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $6{\mathrm{fb}}^{-1}$. The decay $D^0\to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ is observed for the first time when requiring that the two electrons are consistent with coming from the decay of a $\varphi$ or ${\rho }^0/\omega$ meson. The corresponding branching fractions are measured relative to the $D^0\to K^{-}{\pi }^{-}[e^{+}{e}^{-}{]}_{{\rho }^0/\omega }$ decay, where the two electrons are consistent with coming from the decay of a ${\rho }^0$ or $\omega$ meson. No evidence is found for the $D^0\to K^{+}{K}^{-}{e}^{+}{e}^{-}$ decay and world-best limits are set on its branching fraction. The results are compared to, and found to be consistent with, the branching fractions of the $D^0\to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-}$ and $D^0\to K^{+}{K}^{-}{\mu }^{+}{\mu }^{-}$ decays recently measured by LHCb and confirm lepton universality at the current precision.