We investigate the primordial power spectra for general kinetic inflation models that support a period of kinetic dominance in the case of curved universes. We present derivations of the Mukhanov-Sasaki equations with a nonstandard scalar kinetic Lagrangian that manifests itself through the inflationary sound speed $c_s^2$. We extend the analytical approximations exploited in Contaldi et al. [J. Cosmol. Astropart. Phys. 07 (2003) 002] and Thavanesan et al. [Phys. Rev. D 103, 023519 (2021)] to general kinetic Lagrangians and show the effect of $k$-inflation on the primordial power spectra for models with curvature. In particular, the interplay between sound speed and curvature results in a natural low wave number cutoff for the power spectra in the case of closed universes. Using the analytical approximation, we further show that a change in the inflationary sound speed between different epochs in the early universe results in nondecaying oscillations in the resultant power spectra for the comoving curvature perturbation.

Forecast constraints for a symmetric teleparallel gravity model with a $\mathrm{\Lambda }\mathrm{CDM}$ background are made using forthcoming ground and space based gravitational waves observatories. A Bayesian analysis resorting to generated mock catalogs shows that LIGO-Virgo is not expected to be able to distinguish this model from $\mathrm{\Lambda }\mathrm{CDM}$, while both LISA and the ET will, with the ET outperforming LISA. We also show that low redshift events are favored in order to improve the quality of the constrains.

We use a lattice simulation to study a model of axion inflation where the inflaton is coupled to a U(1) gauge field through Chern-Simons interaction. These kinds of models have already been studied with a lattice simulation in the context of reheating. In this work, we focus on the deep inflationary phase and discuss the new aspects that need to be considered in order to simulate gauge fields in this regime. Our main result is reproducing with precision the growth of the gauge field on the lattice induced by the rolling of the axion on its potential, thus recovering the results of linear perturbation theory for this model. In order to do so, we study in detail how the spatial discretization, through the choice of the spatial derivatives on the lattice, influences the dynamics of the gauge field. We find that the evolution of the gauge field is highly sensitive to the choice of the spatial discretization scheme. Nevertheless, we are able to identify a discretization scheme for which the growth of the gauge field on the lattice reproduces the one of continuous space with good precision.

Discontinuous Galerkin methods are popular because they can achieve high order where the solution is smooth, because they can capture shocks while needing only nearest-neighbor communication, and because they are relatively easy to formulate on complex meshes. We perform a detailed comparison of various limiting strategies presented in the literature applied to the equations of general relativistic magnetohydrodynamics. We compare the standard $\mathrm{minmod}/\mathrm{\Lambda }{\mathrm{\Pi }}^N$ limiter, the hierarchical limiter of Krivodonova, the simple WENO limiter, the HWENO limiter, and a discontinuous Galerkin-finite-difference hybrid method. The ultimate goal is to understand what limiting strategies are able to robustly simulate magnetized Tolman-Oppenheimer-Volkoff stars without any fine-tuning of parameters. Among the limiters explored here, the only limiting strategy we can endorse is a discontinuous Galerkin-finite-difference hybrid method.

Among third-generation ground-based gravitational-wave detectors proposed for the next decade, the Einstein Telescope provides a unique kind of null stream—the signal-free linear combination of data—that enables otherwise inaccessible tests of the noise models. We project and showcase challenges in modeling the noise in the 2030s and how it will affect the performance of third-generation detectors. We find that the null stream of the Einstein Telescope is capable of eliminating transient detector glitches that are known to limit current gravitational-wave searches. The techniques we discuss are computationally efficient and do not require a priori knowledge about glitch models. Furthermore, we show how the null stream can be used to provide an unbiased estimation of the noise power spectrum necessary for online and offline data analyses even with multiple loud signals in the band. We overview other approaches to utilizing the null stream. Finally, we comment on the limitations and future challenges of null-stream analyses for the Einstein Telescope and arbitrary detector networks.

In the pursuit of the measurement of the still-elusive ultrahigh-energy (UHE) neutrino flux at energies of order EeV, detectors using the in-ice Askaryan radio technique have increasingly targeted lower trigger thresholds. This has led to improved trigger-level sensitivity to UHE neutrinos. Working with data collected by the Askaryan Radio Array (ARA), we search for neutrino candidates at the lowest threshold achieved to date, leading to improved analysis-level sensitivities. A neutrino search on a data set with 208.7 days of livetime from the reduced-threshold fifth ARA station is performed, achieving a 68% analysis efficiency over all energies on a simulated mixed-composition neutrino flux with an expected background of ${0.10}_{-0.04}^{+0.06}$ events passing the analysis. We observe one event passing our analysis and proceed to set a neutrino flux limit using a Feldman-Cousins construction. We show that the improved trigger-level sensitivity can be carried through an analysis, motivating the phased array triggering technique for use in future radio-detection experiments. We also include a projection using all available data from this detector. Finally, we find that future analyses will benefit from studies of events near the surface to fully understand the background expected for a large-scale detector.

Nonleptonic two-body weak decays of baryons are an important tool to probe the combined charge conjugation–parity symmetry ($CP$) violation. We explain why the decays of strange baryons provide complementary information to the decays of kaons. A model-independent parametrization of the nonleptonic decays of the $\mathrm{\Lambda }$ and $\mathrm{\Xi }$ baryons is reviewed, and the amplitudes are updated according to the latest experimental input. We demonstrate the potential of performing precision tests in strange baryon decays at the next-generation electron-positron $J/\psi$ factories with luminosity of ${10}^{35}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$. The copious production of spin-entangled hyperon-antihyperon pairs via the $J/\psi$ resonance allows for a direct comparison of the baryon and antibaryon decay properties. Using analytic approximations and numerical calculations, we study the quantitative impact of spin correlations and polarization in such $CP$ tests. We show that by using a longitudinally polarized electron beam the statistical precision of the $CP$ tests can be significantly improved compared to the experiments without polarized beams. Furthermore, we map out further directions for possible improvements, like analysis of incompletely reconstructed events or a combination of the isospin related processes. Altogether, these methods are promising for the observation of a statistically significant $CP$-violation signal with a strength corresponding to the standard model predictions. Our conclusions should encourage more detailed feasibility studies, including optimization of the measurement methods and studies of systematic effects. Finally, our results call for an update of the theory predictions with increased precision.

We make an exhaustive investigation on the pentaquark states $qqqc\overline{c}$ ($q=u$, $d$ and $s$) and discuss the effect of color structures in a multiquark color flux-tube model. We exhibit a novel picture of the structure and properties of the states $P_c$ and $P_{cs}$ observed by the LHCb Collaboration. We can describe the states as the compact pentaquark states in the model. The spin-parity of the group of $P_c(4312{)}^{+}$ and $P_c(4337{)}^{+}$ is ${\frac{1}{2}}^{-}$ while that of the group of $P_c(4380{)}^{+}$, $P_c(4440{)}^{+}$ and $P_c(4457{)}^{+}$ is ${\frac{3}{2}}^{-}$. Their structures are pentagon, diquark, pentagon, diquark, and octet, respectively. The members in each group can be analogically called QCD isomers because of their the same spin-parity and quark content but different color structures. The singlet $P_{cs}(4459{)}^0$ has pentagon structure and spin-parity of ${\frac{1}{2}}^{-}$. In addition, we also predict the $P_{cs}$, $P_{css}$ and $P_{csss}$ families in the model. The five-body confinement potential based on the color flux-tube picture, which is a collective degree of freedom and induces QCD isomer phenomenon, plays an important role in the formation of the compact states.

A light axionlike particle or an axionlike particle (ALP) not just gives rise to interesting and spectacular signals of new physics as final states in meson decays, it necessarily leaves tell-tale signatures in processes that involve standard model (SM) fields only (i.e., SM processes). These effects result in the violation of the Gell-Mann-Okubo mass relation, modified form factors, altered integrated and differential rates for various SM transitions etc. This suggests that in the presence of a low lying state, such as an ALP, extraction of masses, mixing angles, and form factors in an entirely data-driven way from meson-physics observables is a highly nontrivial exercise. However, once done correctly, these same observables may, in turn, provide important (indirect) bounds on ALP physics, which remain robust even in the limits where new physics effects conspire to weaken the bounds from direct searches. Starting with a generalized ALP-quark Lagrangian (where restrictions due to parity are removed) we demonstrate this approach by focusing on $K_{{\ell }_3}^{+}$ decays, where we derive (indirect) bounds on ALP physics using $\mathrm{NA}48/2$ data and lattice results. We also find sum rules that not just show deviations in the presence of an ALP but also give hints towards the specific nature of the ALP physics itself.

In this paper, we develop an action formulation of stochastic dynamics in the Hilbert space. In this formulation, the quantum theory of random unitary evolution is easily reconciled with special relativity. We generalize the Wiener process into $1+3$-dimensional spacetime, and then define a scalar random field which keeps invariant under Lorentz transformations. By adding to the action of quantum field theory a coupling term between random and quantum fields, we obtain a random-number action which has the statistical spacetime translation and Lorentz symmetries. The canonical quantization of the theory results in a Lorentz-invariant equation of motion for the state vector or density matrix. We derive the path integral formula of $S$ matrix, based on which we develop a diagrammatic technique for doing the calculation. We find the diagrammatic rules for both the stochastic free field theory and stochastic ${\varphi }^4$ theory. The Lorentz invariance of the random $S$ matrix is strictly proved by using the diagrammatic technique. We then develop a diagrammatic technique for calculating the density matrix of final quantum states after scattering. In the absence of interaction, we obtain the exact expressions of both $S$ matrix and density matrix. In the presence of interaction, we prove a simple relation between the density matrices of stochastic and conventional ${\varphi }^4$ theory. Our formalism leads to an ultraviolet divergence that has a similar origin as that in quantum field theory. The divergence can be canceled by renormalizing the coupling strength to random field. We prove that the stochastic quantum field theory is renormalizable even in the presence of interaction. In the models with a linear coupling between random and quantum fields, the random field excites particles out of the vacuum, driving the Universe towards an infinite-temperature state. The number of excited particles follows the Poisson distribution. The collision between particles is not affected by the random field. But the signals of colliding particles are gradually covered by the background excitations caused by random field.

In this paper, we look at how to construct in Minkowski spacetime a new type of chiral-spin group transformation of the spinor fields, similar to the one discovered by recent works of Glozman et al. in the context of high-temperature QCD and truncated studies in lattice calculations. Afterwards, we prove the invariance of free massless fermionic action under such group transformations, as well as the invariance of the Hamiltonian of free massless fermions. At the end, the possible presence of a symmetry driven by such new chiral-spin group at high-temperature QCD, also at nonzero chemical potential, is discussed.

The two-dimensional Schwinger model is used to explore how lattice fermion operators perceive the global topological charge $q\in \mathbb{Z}$ of a given background gauge field. We focus on Karsten-Wilczek and Borici-Creutz fermions, which are minimally doubled, and compare them to Wilson, Brillouin, naive, staggered and Adams fermions. For each operator the eigenvalue spectrum in a background with $q\ne 0$ is determined along with the chiralities of the eigenmodes, and the spectral flow of the pertinent Hermitian operator is worked out. We find that Karsten-Wilczek and Borici-Creutz fermions perceive the global topological charge $q$ in the same way as staggered and naive fermions do.

We present a calculation of the heavy quark momentum diffusion coefficients in a quark-gluon plasma under the presence of a strong external magnetic field, within the lowest Landau level (LLL) approximation. In particular, we apply the hard thermal loop (HTL) technique for the resummed effective gluon propagator, generalized for a hot and magnetized medium. Using the derived effective HTL gluon propagator and the LLL quark propagator we analytically derive the full results for the longitudinal and transverse momentum diffusion coefficients for charm and bottom quarks beyond the static limit. We also show numerical results for these coefficients in two special cases where the heavy quark is moving either parallel or perpendicular to the magnetic field.

The nature of the three pentaquark states, $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$, discovered by the LHCb Collaboration in 2019, is still under debate, although the ${\overline{D}}^{(*)}{\mathrm{\Sigma }}_c$ molecular interpretation seems to be the most popular. In this work, by adding a $\overline{D}$ meson into the ${\overline{D}}^{*}{\mathrm{\Sigma }}_c$ pair, we investigate the mass and decay width of the three-body molecules $\overline{D}{\overline{D}}^{*}{\mathrm{\Sigma }}_c$ and explore the correlation between the existence of the $\overline{D}{\overline{D}}^{*}{\mathrm{\Sigma }}_c$ molecules with the existence of ${\overline{D}}^{(*)}{\mathrm{\Sigma }}_c$ and ${\overline{D}}^{*}\overline{D}$ two-body molecules. The latter can be identified with the doubly charmed tetraquark state $T_{cc}$ recently discovered by the LHCb Collaboration. Based on the molecular nature of $P_c(4312)$, $P_c(4440)$, $P_c(4457)$, and $T_{cc}$, our results indicate that there exist two three-body bound states of $\overline{D}{\overline{D}}^{*}{\mathrm{\Sigma }}_c$ with $I(J^P)=1(1/2^{+})$ and $I(J^P)=1(3/2^{+})$, and binding energies 37.24 MeV and 29.63 MeV below the $\overline{D}{\overline{D}}^{*}{\mathrm{\Sigma }}_c$ mass threshold. In addition, we find that the mass splitting of these two three-body molecules are correlated to the mass splitting of $P_c(4440)$ and $P_c(4457)$, which offers a nontrivial way to reveal the molecular nature of these states. The partial widths of two $\overline{D}{\overline{D}}^{*}{\mathrm{\Sigma }}_c$ molecules decaying into $J/\psi p\overline{D}$ and $J/\psi p{\overline{D}}^{*}$ are found to be several MeV. We recommend the experimental searches for the $\overline{D}{\overline{D}}^{*}{\mathrm{\Sigma }}_c$ molecules in the $J/\psi p\overline{D}$ and $J/\psi p{\overline{D}}^{*}$ invariant mass distributions.

A Poincaré-covariant $\mathrm{quark}+\mathrm{diquark}$ Faddeev equation is used to develop insights into the structure of the four lightest $(I,J^P=\frac{3}{2},{\frac{3}{2}}^{\pm })$ baryon multiplets. While these systems can contain isovector-axialvector and isovector-vector diquarks, one may neglect the latter and still arrive at a reliable description. The $(\frac{3}{2},{\frac{3}{2}}^{+})$ states are the simpler systems, with features that bear some resemblance to quark model pictures, e.g., their most prominent rest-frame orbital angular momentum component is $\mathsf{S}$-wave and the $\mathrm{\Delta }(1600){\frac{3}{2}}^{+}$ may reasonably be viewed as a radial excitation of the $\mathrm{\Delta }(1232){\frac{3}{2}}^{+}$. The $(\frac{3}{2},{\frac{3}{2}}^{-})$ states are more complex: the $\mathrm{\Delta }(1940){\frac{3}{2}}^{-}$ expresses little of the character of a radial excitation of the $\mathrm{\Delta }(1700){\frac{3}{2}}^{-}$; and while the rest-frame wave function of the latter is predominantly $\mathsf{P}$-wave, the leading piece in the $\mathrm{\Delta }(1940){\frac{3}{2}}^{-}$ wave function is $\mathsf{S}$-wave, in conflict with quark model expectations. Experiments that can test these predictions, such as large momentum transfer resonance electroexcitation, may shed light on the nature of emergent hadron mass.

We investigate events with very forward neutrons in $ep$ collisions at HERA using impact parameter dependent color dipole models with and without saturation. This is the first study of the leading neutron process deploying these models. The model predictions are compared with the available HERA measurements for $6<Q^2<100{\mathrm{GeV}}^2$, $70<W<245\mathrm{GeV}$. Our analysis shows that the models exhibit Feynman scaling, independent of $Q^2$. Our results demonstrate that the $W$ and $Q^2$ dependence of the cross section is independent of the presence of a forward neutron as predicted by limiting fragmentation hypothesis, which is a consequence of Feynman scaling itself. We infer that the HERA leading neutron production inclusive data is insensitive to saturation physics and these cross sections may not be able to distinguish gluon saturation effects in future $ep$ colliders. We provide a good description of the leading neutron structure function $F_2^{LN}$ at small $x$ using an assumption that the small-$x$ structure of protons and pions is universal up to a normalization. We also show that the observables in the exclusive diffractive measurements with a vector meson in the final state are more sensitive to saturation physics at small $x$ than inclusive measurements. At last we provide a prediction for the $\widehat{t}$ spectrum in exclusive vector meson production in the dipole model using Yukawa theory to model the virtual pion’s spatial wave function.

Heavy vector mesons produced in a heavy ion collision are important sources of information about the quark gluon plasma. For instance, the fraction of bottomonium states observed in a such a collision is altered by the dissociation effect caused by the plasma. So, it is very important to understand how the properties of the plasma, like temperature ($T$), density, and the presence of background magnetic fields $(eB)$, affect the dissociation of bottomonium in the thermal medium. Anti–de Sitter/QCD holographic models provide a tool for investigating the properties of heavy mesons inside a thermal medium. The meson states are represented by quasinormal modes in a black hole geometry. In this work we calculate the quasinormal modes and the associated complex frequencies for the four lowest levels of radial excitation of bottomonium inside a plasma with a magnetic field background. We also calculate the differential configuration entropy (DCE) for all these states and investigate how the dissociation effect produced by the magnetic field is translated into a dependence of the DCE on the field. An interesting result obtained in this study is that the DCE increases with the radial excitation level $n$. Also, a nontrivial finding of this work is that the energy density associated with the bottomonium quasinormal modes presents a singularity near the black hole horizon for some combination of values of $T$, $eB$, and $n$. As we show here, it is possible to separate the singular factor and define a square integrable quantity that provides a DCE that is always finite. In addition, we discovered that, working with the potentially singular energy density, one finds a very interesting way to use the DCE as a tool for determining the dissociation temperature of the meson quasistates.

A clear understanding of nuclear parton distribution functions (nPDFs) plays a crucial role in the interpretation of collider data taken at the Relativistic Heavy Ion Collider, the Large Hadron Collider (LHC), and in the near future at the Electron-Ion Collider. Even with the recent inclusions of vector boson and light meson production data, the uncertainty of the gluon PDF remains substantial and limits the interpretation of heavy ion collision data. To obtain new constraints on the nuclear gluon PDF, we extend our recent $\mathrm{nCTEQ}15\mathrm{WZ}+\mathrm{SIH}$ analysis to inclusive quarkonium and open heavy-flavor meson production data from the LHC. This vast new data set covers a wide kinematic range and puts strong constraints on the nuclear gluon PDF down to $x\lesssim {10}^{-5}$. The theoretical predictions for these data sets are obtained from a data-driven approach, where proton-proton data are used to determine effective scattering matrix elements. This approach is validated with detailed comparisons to existing next-to-leading order calculations in nonrelativistic QCD for quarkonia and in the general-mass variable-flavor-number scheme for the open heavy-flavored mesons. In addition, the uncertainties from the data-driven approach are determined using the Hessian method and accounted for in the PDF fits. This extension of our previous analyses represents an important step toward the next generation of PDFs not only by including new data sets, but also by exploring new methods for future analyses.

We present a novel relativistic density-functional approach to modeling quark matter with a mechanism to mimic confinement. The quasiparticle treatment of quarks provides their suppression due to a large quark self energy already at the mean-field level. We demonstrate that our approach is equivalent to a chiral quark model with medium-dependent couplings. The dynamical restoration of the chiral symmetry is ensured by construction of the density functional. Supplemented with the vector repulsion and diquark pairing, the model is applied to construct a hybrid quark-hadron equation of state of cold compact-star matter. We study the connection of such a hybrid equation of state with the stellar mass-radius relation and tidal deformability. The model results are compared to various observational constraints, including the NICER radius measurement of PSR $\mathrm{J}0740+6620$ and the tidal deformability constraint from GW170817. As a striking result, we present selected parametrizations for which the hybrid star sequence reaches masses in the range $2.5–2.67{\mathrm{M}}_{\odot }$ of the lighter object in the merger GW190814, which therefore might be interpreted as the heaviest neutron star with to date.