Exclusive heavy-vector meson photoproduction is a prominent signal in collider experiments with hadron beams. At the highest photon-hadron collision energies, this process is considered as a candidate to constrain the gluon parton distribution function (PDF) at small longitudinal momentum fractions. However, in the framework of collinear factorization, exclusive particle production is described in terms of generalized parton distributions (GPDs). In this contribution, we investigate the connection between GPDs and PDFs at the leading order in ${\alpha }_s$. Our main result is a proposal to quantify the systematic uncertainty inherent to this connection. We put our approach into context with respect to the Shuvaev transform. Our uncertainty estimate can be straightforwardly adapted to higher fixed orders and small-$x$ resummation. The question of extrapolating GPDs to vanishing skewness is paramount for the program of the Electron Ion Collider, notably for the extraction of the radial distributions of partons.

By analyzing $2.93{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data taken at the center-of-mass energy of 3.773 GeV with the BESIII detector, the branching fractions of the inclusive decays $D^{+}\to K_S^{0}X$ and $D^0\to K_S^{0}X$ are measured to be $(33.11\pm 0.13\pm 0.36)\%$ and $(20.75\pm 0.12\pm 0.20)\%$, respectively, where the first uncertainties are statistical and the second are systematic. These results are consistent with the world averages of previous measurements, but with much improved precision.

The minimal-length paradigm, a possible implication of quantum gravity at low energies, is commonly understood as a phenomenological modification of Heisenberg’s uncertainty relation. We show that this modification is equivalent to a cut-off in the space conjugate to the position representation, i.e. the space of wave numbers, which does not necessarily correspond to momentum space. This result is generalized to several dim ensions and noncommutative geometries once a suitable definition of the wave number is provided. Furthermore, we find a direct relation between the ensuing bound in wave-number space and the minimal-length scale. For scenarios in which the existence of the minimal length cannot be explicitly verified, the proposed framework can be used to clarify the situation. Indeed, applying it to common models, we find that one of them does, against all expectations, allow for arbitrary precision in position measurements. In closing, we comment on general implications of our findings for the field. In particular, we point out that the minimal length is purely kinematical such that, effectively, it is not influenced by the overlying dynamics and the choice of Hamiltonian.

The propagation of perturbations is studied with generalized holonomy corrections in a fully consistent way, ensuring that the deformed algebra of constraints remains closed. The primordial cosmological power spectra are calculated. It is shown that, although the detailed form of the correction does unavoidably impact the observables, the main known results of loop quantum cosmology are robust in this respect.

We study a holographic model of quantum chromodynamics, which can describe a color superconductor and a dilute nucleon gas phase. The two phases are adjoined in the phase diagram at a critical value of the chemical potential. In other words, a first-order transition from the ordinary nucleon gas to the color superconductor is found by increasing the chemical potential. This model is suitable to investigate the possibility of a cold compact star with a color superconducting core. The equation of state of the star is given by the holographic model considered in this article, and we find that it is impossible in the present model to find a hybrid star of nuclear matter and the color superconductor core through the relation of mass and radius of the star by solving the Tolman-Oppenheimer-Volkoff equations. Several other interesting implications are given by using the equation of state.

We first present a consistent canonical formulation of the general (nonmarginal) Oppenheimer-Snyder model. The switching between comoving and stationary observer is achieved by promoting coordinate transformations between dust proper time and Schwarzschild-Killing time to canonical ones. This leads to a multivalued Hamiltonian, which is deparameterizable. We then discuss the quantization of comoving and stationary observers by employing the method of affine coherent state quantization (ACSQ). We thereby demonstrate that under certain conditions the quantum corrected trajectories can replace the classical singularity by a bounce. We then show that both comoving and stationary observers see this bouncing collapse behavior. We finally discuss a switching between these classes of observers at the quantum level.

We discuss the relationship between the Bogoliubov transformations, squeezed states, entanglement, and maximum violation of the Bell-Clauser-Horne-Shimony-Holt (Bell-CHSH) inequality. In particular, we point out that the construction of the four bounded operators entering the Bell-CHSH inequality can be worked out in a simple and general way, covering a large variety of models, ranging from quantum mechanism to relativistic quantum field theories. Various examples are employed to illustrate the above mentioned framework. We start by considering a pair of entangled spin-one particles and a squeezed oscillator in quantum mechanics, moving then to the relativistic complex quantum scalar field and to the analysis of the vacuum state in Minkowski space-time in terms of the left and right Rindler modes. In the latter case, the Bell-CHSH inequality turns out to be parametrized by the Unruh temperature.

The regularized Maxwell theory is a recently discovered theory of nonlinear electrodynamics that admits many important gravitating solutions within the Einstein theory. Namely, it was originally derived as the unique nonlinear electrodynamics (that depends only on the field invariant $F_{\mu \nu }{F}^{\mu \nu }$) whose radiative solutions can be found in the Robinson-Trautman class. At the same time, it is the only electrodynamics of this type (apart from Maxwell) whose slowly rotating solutions are fully characterized by the electrostatic potential. In this paper, after discussing the basic properties of the regularized Maxwell theory, we concentrate on its spherical electric solutions. These not only provide “the simplest” regularization of point electric field and its self-energy, but also feature complex thermodynamic behavior (in both canonical and grand canonical ensembles) and admit an unprecedented phase diagram with multiple first-order, second-order, and zeroth-order phase transitions. Among other notable solutions, we construct a novel C-metric describing accelerated AdS black holes in the regularized Maxwell theory. We also present a generalization of the regularized Maxwell Lagrangian applicable to magnetic solutions, and find the corresponding spherical, slowly rotating, and weakly Newman-Unti-Tamburino charged solutions.

We study the underlying structure of the vanishing of the Love numbers of both Schwarzschild and Kerr black holes in terms of spacetime conformal symmetry in a unified manner for the static spin-$s$ fields. The perturbations can be reduced with the harmonic decomposition to a set of infinite static scalar fields in a two-dimensional anti–de Sitter spacetime $({\text{AdS}}_2)$. In the reduced system, each scalar field is paired with another, implying that all multipole modes of the perturbation can be regarded as symmetric partners, which can be understood from the property of the supersymmetry algebra. The generator of the supersymmetric structure is constructed from a closed conformal Killing vector field of ${\text{AdS}}_2$. The associated conserved quantity allows one to show no static response, i.e., vanishing of the Love and dissipation numbers. We also discuss the vanishing Love numbers of the Kerr black hole with the nonzero dissipation numbers for the nonaxisymmetric perturbations in terms of a radial constant found in a parallel manner as the axisymmetric field case even though the interpretation for the structure is controversial. The symmetric structure corresponds to the “ladder” symmetry in [Hui et al., J. Cosmol. Astropart. Phys. 01 (2022) 032] although the geometrical origin is different. Our ladder operator includes the generators of hidden symmetries in previous works.

Out-of-equilibrium effects may play an important role in the dynamics of neutron star mergers and in heavy-ion collisions. Bemfica, Disconzi, Noronha and Kovtun (BDNK) recently derived a causal, locally well posed, and modally stable relativistic fluid model that incorporates the effects of viscosity and heat diffusion. We study the nonrelativistic limit of this fluid model and show that causality for relativistic motion restricts the transport coefficients in the nonrelativistic limit. This restriction provides an upper bound on the ratio of the shear viscosity to the entropy density for fluids that can be described as relativistic within the BDNK model and can be exactly modeled using the Navier-Stokes equation in the nonrelativistic limit. Furthermore, we show that the Fourier law of heat conduction must be modified by higher gradient corrections for such fluids. We also show that the nonrelativistic limit of the BDNK equations of motion are never hyperbolic, in contrast to the nonrelativistic limit of extended variable models, whose nonrelativistic equations of motion can be hyperbolic or not depending on the scaling of the transport coefficients present in the auxiliary equations for viscous degrees of freedom.

We consider rotating charged black holes with a scalar dilaton field and surrounded by plasma, with the purpose of studying their shadows. The corresponding metric has been previously obtained in the literature from the static solution by using the Newman-Janis algorithm. Assuming a well-known form for the pressureless and nonmagnetized plasma distribution, which is suitable for the separation of the Hamilton-Jacobi equation for light, we derive an expression that determines the shape of the shadow. We present some examples of contours and we analyze their observable properties as functions of the charge and the dilaton coupling. We find that the presence of plasma introduces a dependency on the frequency, with the shadow becoming smaller as the frequency decreases.

We discuss the polarizational study of isotropic gravitational wave backgrounds with the second-generation detector network, paying special attention to the impacts of adding LIGO-India. The backgrounds can be characterized by at most five spectral components (three parity-even ones and two parity-odd ones). They can be algebraically decomposed through the difference of the corresponding overlap reduction functions defined for the individual spectra. We newly identify two interesting relations between the overlap reduction functions, and these relations generally hamper the algebraic decomposition in the low-frequency regime $f\lesssim 30\mathrm{Hz}$. We also find that LIGO-India can significantly improve the network sensitives to the odd spectral components.

We examine the Newman-Janis algorithm’s application to an exact regular static solution sustained by a minimally coupled scalar field with a nonstandard kinetic term. Although coordinate complexification leads to a regular Kerr-like black hole, we are facing discrepancies in Einstein’s equations in a fairly small domain, for which the regularizing parameter is responsible. Outside this most intriguing region, the geometry is nothing but the standard Kerr spacetime.

We derive optimal estimators for the two-, three-, and four-point correlators of statistically isotropic scalar fields defined on the sphere, such as the cosmic microwave background temperature fluctuations, allowing for arbitrary (linear) masking and inpainting schemes. In each case, we give the optimal unwindowed estimator (obtained via a maximum-likelihood prescription, with an associated Fisher deconvolution matrix), and an idealized form, and pay close attention to their efficient computation. For the trispectrum, we include both parity-even and parity-odd contributions, as allowed by symmetry. The estimators can include arbitrary weighting of the data (and remain unbiased), but are shown to be optimal in the limit of inverse-covariance weighting and Gaussian statistics. The normalization of the estimators is computed via Monte Carlo methods, with the rate-limiting steps (involving spherical harmonic transforms) scaling linearly with the number of bins. An accompanying code package, polybin, implements these estimators in python, and we demonstrate the estimators’ efficacy via a suite of validation tests.

The properties of the matter density field in the initial conditions have a decisive impact on the features of the large-scale structure of the Universe as observed today. These need to be studied via $N$-body simulations, which are imperative to analyze high density collapsed regions into dark matter halos. In this paper, we train machine learning algorithms with information from $N$-body simulations to infer two properties: dark matter particle halo classification that leads to halo formation prediction with the characteristics of the matter density field traced back to the initial conditions, and dark matter halo formation by calculating the halo mass function, which offers the number density of dark matter halos with a given threshold. We map the initial conditions of the density field into classification labels of dark matter halo structures. The halo mass function of the simulations is calculated and reconstructed with theoretical methods as well as our trained algorithms. We test several machine learning techniques where we could find that the random forest and neural networks proved to be the better performing tools to classify dark matter particles in cosmological simulations. We also show that, by using only a few data points, we can effectively train the algorithms to reconstruct the halo mass function in a model-independent way, giving us a highly accurate fitting function that aligns well with both simulation and theoretical results.

We study the dynamics of a cosmic string loop captured by a rotating black hole, ignoring string reconnections. A loop is numerically evolved in Kerr spacetime, with the result that it turns into one or more growing or contracting double-lines rotating around the black hole in the equatorial plane. This is in good agreement with the approximate analytical treatment of the problem investigated by Xing et al., who studied the evolution of the auxiliary curve associated with the string loop. We confirm that the auxiliary curve deformation can indeed describe the string motion in realistic physical scenarios to a reasonable accuracy, and can thus be used to further study other phenomena such as superradiance and reconnections of the captured loop.

Employing the functional renormalization group approach at next-to-leading order of the derivative expansion, we refine our earlier findings for the location of the Yang-Lee edge singularity in classic $\mathrm{O}(N)$ universality classes. For the universality classes of interest to QCD, in three dimensions, we found $|z_c|/R_{\chi }^{1/\gamma }=1.612(9),1.597(3)$ for $N=2$, 4 correspondingly. We also established $|z_c|=2.04(8),1.69(3)$ for $N=2$, 4 albeit with greater systematic error.

A massive photon possesses a longitudinal polarization mode absent in its massless counterpart. Transverse and longitudinal modes follow different dispersion relations, the latter being much less attenuated than the former when passing through a conductor, suggesting the possibility of isolating longitudinal modes by shining intense light on a conducting wall. We calculate the transmission rates for normal incidence upon a semi-infinite medium and passage through a slab. For the second case we compare the expected photon fluxes with those measurable in current and future light-shining-through-a-wall experiments. Using a 1-MW microwave source as envisaged by the STAX project, a sensitivity at the level of $m_{\gamma }<9.6\times {10}^{-11}\mathrm{eV}/{\mathrm{c}}^2$ could be reached after a run time of an year, with a potential improvement by a factor of $\sim {10}^4$ if radio waves of similar power are used.

We present the calculation of the next-to-leading-order corrections for Higgs $\mathrm{boson}+\text{jet}$ production at the Large Hadron Collider, that arise from the Higgs trilinear self-coupling (${\lambda }_{HHH}$). We use the method of large top-quark mass expansion to tackle the challenging two-loop virtual amplitude and apply the Padé approximation to extend the region of convergence of this expansion. We find that the ${\lambda }_{HHH}$-related corrections amount to 0.66% for the total cross section. For the invariant mass distribution and Higgs boson transverse momentum distribution, the corrections are mostly in the range 0.5%–0.7%. Our results can be used to set extra constraints on ${\lambda }_{HHH}$ from the experimental data.