We study the unpolarized and the helicity-dependent generalized parton distributions (GPDs) for the valence quarks of the proton in both momentum space and position space within the basis light-front quantization (BLFQ) framework. The GPDs for the valence quarks are computed from the eigenvectors of a light-front effective Hamiltonian in the valence Fock sector consisting of a three-dimensional confinement potential and a one-gluon exchange interaction with fixed coupling. Employing these GPDs, we obtain the spatial distributions of quark angular momentum inside the proton. In our BLFQ approach, we explore various definitions of angular momentum density and illustrate the differences between them arising from terms that integrate to zero. We also discuss the flavor contributions to the quark angular momentum densities.

The most recent data on beam asymmetries $\mathrm{\Sigma }$ and beam-target asymmetries $E$ from the CLAS Collaboration, together with the previous data on differential cross sections and beam asymmetries from the CLAS and LEPS Collaborations, for the $\gamma n\to K^{+}{\mathrm{\Sigma }}^{-}$ reaction are studied based on an effective Lagrangian approach in the tree-level Born approximation. The $t$-channel $K$ and $K^{*}(892)$ exchanges, the $u$-channel $\mathrm{\Sigma }$ exchange, the interaction current, and the exchanges of $N$, $\mathrm{\Delta }$, and their excited states in the $s$ channel are considered in constructing the reaction amplitudes to describe the available experimental data. The reaction mechanisms of $\gamma n\to K^{+}{\mathrm{\Sigma }}^{-}$ are analyzed, and the associated resonances’ parameters are extracted. The numerical results show that the $\mathrm{\Delta }$ exchange and the $N(1710)1/2^{+}$, $N(1880)1/2^{+}$, $N(1900)3/2^{+}$, and $\mathrm{\Delta }(1920)3/2^{+}$ resonance exchanges in the $s$ channel dominate the $\gamma n\to K^{+}{\mathrm{\Sigma }}^{-}$ reaction in the lower energy region, and the $t$-channel $K^{*}(892)$ exchange plays a crucial role at forward angles in the higher energy region.

An analysis of the forward-backward asymmetry (FBA) in the decay $B^{\pm }\to K^{\pm }{K}^{\mp }{K}^{\pm }$ is carried out based on the LHCb data. It is found that the large FBA observed for the invariant mass of the $K^{+}{K}^{-}$ pair around 1.5 GeV can be explained by the interference of the amplitudes between the resonances with even and odd spins, where the former can be the spin-0 $f_0(1500)$ resonance plus a nonresonance $s$ wave, while the latter is a spin-1 resonance which is probably ${\rho }^0(1450)$. This is in contradiction with the conclusion of former experimental analysis [e.g., BABAR, Phys. Rev. D 85, 112010 (2012)], according to which the analysis showed no signal of spin-odd resonances at all when the invariant mass of the $K^{+}{K}^{-}$ pair was around 1.5 GeV. According to the analysis of the current paper the existence of the spin-odd resonances such as ${\rho }^0(1450)$ is inevitable for the explanation of the large FBA in this region. The analysis also shows that the $CP$ asymmetry of the decay channel $B^{\pm }\to {\rho }^0(1450)K^{\pm }$ is about $(-3.4\pm 3.0)\%$. We suggest our experimental colleagues perform a closer analysis of this channel. We also suggest to perform the measurements of the FBAs (as well as the forward-backward $CP$ asymmetry) in other three-body decay channels of beauty and charmed mesons, as this is helpful for resonance analysis.

In this paper we investigate the prospects for measuring the branching fraction of the Standard Model Higgs boson decay into a pair of $Z$ bosons at the future Compact Linear Collider (CLIC) at 350 GeV and 3 TeV center-of-mass energies. Studies are performed using a detailed simulation of the detector for CLIC, taking into consideration all relevant physics and beam-induced background processes. It is shown that the product of the Higgs production cross section and the branching fraction $\mathrm{BR}(H\to Z{Z}^{*})$ can be measured with a relative statistical uncertainty of 20% (3.0%) at a center-of-mass energy of 350 GeV (3 TeV) using semileptonic final states, assuming an integrated luminosity of $1{\mathrm{ab}}^{-1}$ ($5{\mathrm{ab}}^{-1}$).

We present a formulation of the generalized uncertainty principle based on a commutator $[{\widehat{x}}^i,{\widehat{p}}_j]$ between position and momentum operators defined in a covariant manner using normal coordinates. We show how any such commutator can acquire corrections if the momentum space is curved. The correction is completely determined by the extrinsic curvature of the surface $p^2=\text{constant}$ in the momentum space, and results in noncommutativity of normal position coordinates $[{\widehat{x}}^i,{\widehat{x}}^j]\ne 0$. We then provide a construction for the momentum space geometry as a suitable four dimensional extension of a geometry conformal to the three dimensional relativistic velocity space—the Lobachevsky space—whose curvature is determined by the dispersion relation $F(p^2)=-m^2$, with $F(x)=x$ yielding the standard Heisenberg algebra.

We compare different formulations of the generalized uncertainty principle that have an underlying algebraic structure. We show that the formulation by Kempf, Mangano, and Mann [Phys. Rev. D 52 (1995)], quite popular for phenomenological studies, satisfies the Jacobi identities only for spin zero particles. In contrast, the formulation proposed earlier by one of us (Maggiore) [Phys. Lett. B 319 (1993)] has an underlying algebraic structure valid for particles of all spins and in this sense seems more fundamental. The latter is also much more constrained, resulting in only two possible solutions, one expressing the existence of a minimum length and the other expressing a form of quantum-to-classical transition. We also discuss how this more stringent algebraic formulation has an intriguing physical interpretation in terms of a discretized time at the Planck scale.

We construct all ${\mathrm{N}}^k\mathrm{MHV}$ six-particle amplitude integrands in color-dressed, maximally supersymmetric Yang-Mills theory at two loops in a single prescriptive basis of master integrands.

We study spherically symmetric nontopological soliton (NTS) stars numerically in the coupled system of a complex scalar field, a U(1) gauge field, a complex Higgs scalar field, and Einstein gravity, where the symmetry is broken spontaneously. The gravitational mass of NTS stars is limited by a maximum mass for a fixed breaking scale, and the maximum mass increases steeply as the breaking scale decreases. In the case of the breaking scale is much less than the Planck scale, the maximum mass of NTS stars becomes the astrophysical scale, and such a star is relativistically compact so that it has the innermost stable circular orbit. The first author contributed with a part of the numerical calculations. The second contributed with planning and conducting the research, and the third contributed with all numerical calculations and finding new properties of the system.

A photon sphere is known as the geometrical structure that shapes a black hole shadow. The mechanism is well understood for static or stationary black hole spacetimes such as the Schwarzschild and the Kerr spacetimes. In this paper, we investigate and explicitly specify a photon sphere that shapes a black hole shadow in a dynamical spacetime while taking the global structure of the spacetime into account. We consider dynamical and eternal black hole cases of the Vaidya spacetime, which represents a spherically symmetric black hole with accreting null dust. First, we numerically show that there are the dynamical photon sphere and photon orbits corresponding to the shadow edge in a moderate accretion case. Second, the photon spheres are derived analytically in special cases. Finally, we discuss the relation between our photon sphere and the several notions defined as a photon sphere generalization.

We study the stability of topological black holes in the presence of a cosmological constant and a scalar field coupled to the Gauss-Bonnet (GB) term in the extended scalar-tensor theories. We find two competing effects. As the strength of the coupling $\lambda$ of the scalar field to the GB term is increasing, the matter is interacting more strongly with gravity while as the hyperbolicity $\xi$ of spacetime is getting larger the kinetic effects of matter tend to dominate. Calculating both analytically and numerically the quasinormal modes (QNMs) we found for each $\lambda$ a critical value of $\xi$, below which there is an instability. When the coupling constant $\lambda$ is getting very large, all of the QNMs develop a positive imaginary part indicating an instability. This behavior indicates a phase transition to a scalarized topological black hole induced by curvature effects.

Primordial black holes (PBHs) in the mass range ${10}^{17}–{10}^{23}\mathrm{gm}$ are considered as possible dark matter candidates as they are not subject to big-bang nucleosynthesis constraints and behave like cold dark matter. If PBHs are indeed dark matter, they cannot be treated as isolated objects in asymptotic flat space-time. Furthermore, when compared to stellar-mass black holes, the rate at which the Hawking particles radiate out from PBHs is significantly faster. In this work, we obtain an exact time-dependent solution that models evaporating black holes in the cosmological background. As a result, the solution considers all three aspects of PBHs—mass-loss due to Hawking radiation, black hole surrounded by mass distribution, and cosmological background. Furthermore, our model predicts that the decay of PBHs occurs faster for larger masses; however, the decay rate reduces for lower mass. Finally, we discuss the implications of theoretical constraints on PBHs as dark matter.

We introduce nrpyelliptic, an elliptic solver for numerical relativity (NR) built within the nrpy+ framework. As its first application, nrpyelliptic sets up conformally flat, binary black hole (BBH) puncture initial data (ID) on a single numerical domain, similar to the widely used twopunctures code. Unlike twopunctures, nrpyelliptic employs a hyperbolic relaxation scheme, whereby arbitrary elliptic partial differential equations (PDEs) are trivially transformed into a hyperbolic system of PDEs. As consumers of NR ID generally already possess expertise in solving hyperbolic PDEs, they will generally find nrpyelliptic easier to tweak and extend than other NR elliptic solvers. When evolved forward in (pseudo)time, the hyperbolic system exponentially reaches a steady state that solves the elliptic PDEs. Notably nrpyelliptic accelerates the relaxation waves, which makes it many orders of magnitude faster than the usual constant wave speed approach. While it is still $\sim 12\mathrm{x}$ slower than twopunctures at setting up full-3D BBH ID, nrpyelliptic requires only $\approx 0.3\%$ of the runtime for a full BBH simulation in the einstein toolkit. Future work will focus on improving performance and generating other types of ID, such as binary neutron stars.

We establish a new self-consistent model of coupling between the cosmic dark energy and dark matter in the framework of the rheological approach, which is based on the representation of the equations of state in terms of integral operators of the Volterra type. We elaborate on the so-called four-kernel model, in the framework of which both the dark energy and dark matter pressures are presented by two integrals containing the energy densities of the dark energy and dark matter. For the Volterra operators, the kernels of which are associated with the effects of fading memory, the corresponding isotropic homogeneous cosmological model is shown to be exactly integrable. We consider the classification of the model exact solutions, based on the analysis of roots of the characteristic polynomial associated with the key equation of the presented model. The scalars of the pressure and energy density of the dark energy and dark matter, the Hubble function and acceleration parameter are presented explicitly as the functions of the dimensionless scale factor. The scale factor as the function of the cosmological time is found in quadratures and is described analytically, qualitatively, and numerically. Asymptotic analysis allows us to classify the models with respect to behavior typical for the big rip, little rip, and pseudorip (de Sitter type). Two intriguing exact cosmological solutions are discussed, which describe the superexponential expansion and the symmetric bounce. New solutions are presented, which correspond to the quasiperiodic behavior of the state functions of the dark fluid and of the geometric characteristics of the Universe.

The early expansion history of the Universe is constrained by combining the most recent limits on the cosmic gravitons in the audio band and the claimed evidences of the nHz domain. The simplest scenario stipulates that between the end of inflation and the formation of light nuclei the evolution consists of a single phase expanding at a rate that is either faster or slower than the one of radiation. If there are instead multiple postinflationary stages evolving at different rates, then the spectral energy density always undershoots the signals potentially attributed to relic gravitons by the pulsar timing arrays at intermediate frequencies but ultimately develops a local maximum. After examining further complementary possibilities (like the presence of a secondary stage of inflation at low scales), we analyze the early modifications of the effective expansion rate and argue that if the refractive index of the relic gravitons increases during a conventional inflationary epoch, then the spectral energy density is blue above the fHz and then flattens out in the $\mu \mathrm{Hz}$ region. In this instance the signal is compatible with the unconfirmed nHz observations, with the most recent limits of the wide-band interferometers and with the further constraints customarily imposed on the backgrounds of relic gravitons produced during inflation.

The residuals of the power spectra of Wilkinson Microwave Anisotropy Probe and Planck’s cosmic microwave background (CMB) anisotropies data are known to exhibit a few interesting anomalies at different scales with marginal statistical significance. Combining bottom-up and top-down model-building approaches and using a pipeline that efficiently compares model predictions with data, we construct a model of primordial standard clock that is able to link and address the anomalies at both the large and small scales. This model, and its variant, provide some of the best fits to the feature anomalies in CMB. According to Bayes evidences, these models are currently statistically indistinguishable from the Standard Model. We show that the difference between them will soon become statistically significant with various higher quality data on the CMB polarization. We demonstrate that such a model-building and data-analyses process may be used to uncover a portion of detailed evolutionary history of our universe during its primordial epoch.

Neutron star mergers are very violent events involving extreme physical processes: dynamic, strong-field gravity; large magnetic field; very hot, dense matter; and the copious production of neutrinos. Accurate modeling of such a system and its associated multimessenger signals, such as gravitational waves, short gamma ray bursts, and kilonova, requires the inclusion of all these processes and is increasingly important in light of advancements in multimessenger astronomy generally, and in gravitational wave astronomy in particular (such as the development of third-generation detectors). Several general relativistic codes have been incorporating some of these elements with different levels of realism. Here, we extend our code mhduet, which can perform large eddy simulations of magnetohydrodynamics to help capture the magnetic field amplification during the merger, and to allow for realistic equations of state and neutrino cooling via a leakage scheme. We perform several tests involving isolated and binary neutron stars demonstrating the accuracy of the code.

When searching for new gravitational-wave or electromagnetic sources, the $n$ signal parameters (masses, sky location, frequencies, etc.) are unknown. In practice, one hunts for signals at a discrete set of points in parameter space, called a template bank. These may be constructed systematically as a lattice or, alternatively, by placing templates at randomly selected points in parameter space. Here, we calculate the fraction of signals lost by an $n$-dimensional random template bank (compared to a very finely spaced bank). This fraction is compared to the corresponding loss fraction for the best possible lattice-based template banks containing the same number of grid points. For dimensions $n<4$, the lattice-based template banks significantly outperform the random ones. However, remarkably, for dimensions $n>8$, the difference is negligible. In high dimensions, random template banks outperform the best known lattices.

Achieving the quantum noise targets of third-generation detectors will require 10 dB of squeezed-light enhancement as well as megawatt laser power in the interferometer arms—both of which require unprecedented control of the internal optical losses. In this work, we present a novel optimization approach to gravitational-wave detector design aimed at maximizing the robustness to common, yet unavoidable, optical fabrication and installation errors, which have caused significant loss in Advanced LIGO. As a proof of concept, we employ these techniques to perform a two-part optimization of the LIGO $\mathrm{A}+$ design. First, we optimize the arm cavities for reduced scattering loss in the presence of point absorbers, as currently limit the operating power of Advanced LIGO. Then, we optimize the signal recycling cavity for maximum squeezing performance, accounting for realistic errors in the positions and radii of curvature of the optics. Our findings suggest that these techniques can be leveraged to achieve substantially greater quantum noise performance in current and future gravitational-wave detectors.