In the largest, currently known, class of one quadrillion globally consistent F-theory Standard Models with gauge coupling unification and no chiral exotics, the vectorlike spectra are counted by cohomologies of root bundles. In this work, we apply a previously proposed method to identify toric base threefolds, which are promising to establish F-theory Standard Models with exactly three quark doublets and no vectorlike exotics in this representation. The base spaces in question are obtained from triangulations of 708 polytopes. By studying root bundles on the quark-doublet curve $C_{(\mathbf{3},\mathbf{2}{)}_{1/6}}$ and employing well-known results about desingularizations of toric K3 surfaces, we derive a triangulation independent lower bound ${\check{N}}_P^{(3)}$ for the number $N_P^{(3)}$ of root bundles on $C_{(\mathbf{3},\mathbf{2}{)}_{1/6}}$ with exactly three sections. The ratio ${\check{N}}_P^{(3)}/N_P$, where $N_P$ is the total number of roots on $C_{(\mathbf{3},\mathbf{2}{)}_{1/6}}$, is largest for base spaces associated with triangulations of the eighth three-dimensional polytope ${\mathrm{\Delta }}_8^{\circ }$ in the Kreuzer-Skarke list. For each of these $\mathcal{O}({10}^{15})$ threefolds, we expect that many root bundles on $C_{(\mathbf{3},\mathbf{2}{)}_{1/6}}$ are induced from F-theory gauge potentials and that at least every 3000th root on $C_{(\mathbf{3},\mathbf{2}{)}_{1/6}}$ has exactly three global sections and thus no exotic vectorlike quark-doublet modes.

We reply to a recent Comment on [Phys. Rev. D 103, 124010 (2021)] and on its implications for the subject of maximum force. The value of the criticism raised consists of removing confusion present in [Phys. Rev. D 103, 124010 (2021)] and in previous literature and of distinguishing clearly between local forces acting on pointlike particles and other “forces,” which are still interesting, although not subject to a universal upper bound.

Despite suggestions to the contrary, no counterargument to the principle of maximum force or to the equivalent principle of maximum power has yet been provided.

We formulate an equivalence between the 2-dim $\sigma$-model spectrum expanded on a nontrivial massive vacuum and a classical particle Hamiltonian with variable mass and potential. By considering methods of analytic Galoisian nonintegrability on the appropriate geodesics of the Hamiltonian system we algebraically constrain the particle masses at fixed time, such that integrability is allowed. Through our equivalence, this explicitly constrains the masses of the excited spectrum of the dual 2-dim theory in such a way to imply the $S$-matrix factorization and no particle production. In particular, the integrability of the classical particle system implies the factorization of the $S$-matrix in the dual quantum 2-dim theory. Our proposal provides also nontrivial evidence on the connection between integrability and $S$-matrix factorization for large class of theories with interactions that break Lorentz invariance.

We consider quantum effects of gravitational and electromagnetic fields in spherically symmetric black hole spacetimes in the asymptotic safety scenario. Introducing both the running gravitational and electromagnetic couplings from the renormalization group equations and applying a physically sensible scale identification scheme based on the Kretschmann scalar, we construct a quantum-mechanically corrected, or “quantum improved” Reissner-Nordstrom metric. We study the global structure of the quantum improved geometry and show, in particular, that the central singularity is resolved, being generally replaced with a regular Minkowski core, where the curvature tensor vanishes. Exploring cases with more general scale identifications, we further find that the space of quantum improved geometries is divided into two regions: one for geometries with a regular Minkowski core and the other for those with a weak singularity at the center. At the boundary of the two regions, the geometry has either Minkowski-, de Sitter-, or anti-de Sitter core.

Chiral symmetries in field theory are typically affected by an anomaly in the quantum theory. This anomaly emerges when one introduces an interaction with a Yang-Mills or gravitational background. Physical applications of this quantum effect have been traditionally connected to topological questions of the background field and the study of instantons. We show here how one can alternatively find situations of physical interest that only involve ordinary, but dynamical solutions of the background field equations. More precisely, we show that solutions to the Einstein (Maxwell) equations are able to trigger the chiral anomaly if and only if they admit a flux of gravitational (electromagnetic) radiation with net circular polarization. As a consequence, astrophysical systems that admit such radiation spontaneously generate a flux of particles with net helicity from the quantum vacuum.

We analyze the properties of the circular orbits for massive particles in the equatorial plane of symmetric rotating Ellis wormholes. In particular, we obtain the orbital frequencies and the radial and vertical epicyclic frequencies, and consider their lowest parametric, forced and Keplerian resonances. These show that quasiperiodic oscillations in accretion disks around symmetric rotating Ellis wormholes have many distinct properties as compared to quasiperiodic oscillations in accretion disks around rotating Teo wormholes and the Kerr black hole. Still we can distinguish some common features which appear in wormhole spacetimes as opposed to black holes. The most significant ones include the possibility of excitation of stronger resonances such as lower order parametric and forced resonances and the localization of these resonances deep in the region of strong gravitational interaction near the wormhole throat, which will lead to further amplification of the signal.

Multiple scalar fields appear in vast modern particle physics and gravity models. When they couple to gravity nonminimally, conformal transformation is utilized to bring the theory into the Einstein frame. However, the kinetic terms of scalar fields are usually not canonical, which makes analytic treatment difficult. Here, we investigate under what conditions the theories can be transformed to the quasicanonical form, in which case the effective metric tensor in field space is conformally flat. We solve the relevant nonlinear partial differential equations for an arbitrary number of scalar fields and present several solutions that may be useful for future phenomenological model building, including the $\sigma$ model with a particular nonminimal coupling. We also find conformal flatness can always be achieved in some modified gravity theories, for example, the Starobinsky model.

We consider the motion of a gyroscope on a closed timelike curve (CTC). A gyroscope is identified with a unit-length spacelike vector—a spin-vector—orthogonal to the tangent to the CTC, and satisfying the equations of Fermi-Walker transport along the curve. We investigate the consequences of the periodicity of the coefficients of the transport equations, which arise from the periodicty of the CTC, which is assumed to be piecewise $C^2$. We show that every CTC with period $T$ admits at least one $T$–periodic spin-vector. Further, either every other spin-vector is $T$-periodic, or no others are. It follows that gyroscopes carried by CTCs are either all $T$-periodic, or are generically not $T$-periodic. We consider examples of spacetimes admitting CTCs, and address the question of whether $T$-periodicity of gyroscopic motion occurs generically or only on a negligible set for these CTCs. We discuss these results from the perspective of principles of consistency in spacetimes admitting CTCs.

A double new class of solutions to the general relativity field equations describing interior spacetimes sourced by stationary cylindrical anisotropic fluids with principal stress directed along the symmetry axis is displayed. These solutions are required to satisfy regularity and junction conditions so that they can be possibly used to represent rotating astrophysical objects. Mathematical and physical properties are analyzed. The spacetime two independent parameters are physically interpreted, and they are shown to define two different solution classes together with stating the latters’ properties.

We explore the structure of shadow for a Kerr-de Sitter black hole with a nonmagnetized, pressureless plasma surrounding it. Specific plasma distributions are considered to separate the Hamilton-Jacobi equation and find the photon regions. An analytic formula describing the boundary curve of the shadow for such a black hole in an expanding universe for an observer at any finite point outside the horizon is derived. We observe deviations which are further explored by calculating the curvature radius at a particular point and distortion parameter for such structures in the presence and absence of plasma and calculate the diameter of the shadow.

In this article, we construct exact black hole solutions with many horizons (more than two) in the Einstein-nonlinear electrodynamic theories. In particular, we acquire the explicit expression of a nonlinear electrodynamic Lagrangian for the 3-horizon black holes. Then we make the investigations of three-horizon black holes on the horizons, the null and timelike geodesics, the Love numbers, and the thermodynamics.

In scalar-tensor Horndeski theories, nonsingular cosmological models—bounce and genesis—are problematic because of potential ghost and/or gradient instabilities. One way to get around this obstacle is to send the effective Planck mass to zero in the asymptotic past (“strong gravity in the past”). One may suspect that this feature is a signal of a strong coupling problem at early times. However, the classical treatment of the cosmological background is legitimate, provided that the strong coupling energy scale remains at all times much higher than the scale associated with the classical evolution. We construct various models of this sort, namely (i) bouncing Universe which proceeds through inflationary epoch to kination (expansion within general relativity, driven by massless scalar field); (ii) bouncing Universe with kination stage immediately after bounce; (iii) combination of genesis and bounce, with the Universe starting from flat space-time, then contracting and bouncing to the expansion epoch; (iv) “standard” genesis evading the strong coupling problem in the past. All these models are stable, and perturbations about the backgrounds are not superluminal.

It has been intensively discussed if modifications in the dynamics of the Universe at late times are able or not able to solve the $H_0$ tension. On the other hand, it has also been argued that the $H_0$ tension is actually a tension on the supernova absolute magnitude $M_B$. In this work, we robustly constrain $M_B$ using Pantheon supernovae Ia sample, baryon acoustic oscillations, and big bang nucleosynthesis data, and assess the $M_B$ tension by comparing three theoretical models, namely the standard $\mathrm{\Lambda }\mathrm{CDM}$, the $w\mathrm{CDM}$, and a nongravitational interaction between dark energy (IDE) and dark matter. We find that the IDE model can solve the $M_B$ tension with a coupling different from zero at 95% CL, confirming the results obtained using a $H_0$ prior.

We investigate the effect of accreting primordial black holes (PBHs) on the thermal history of the intergalactic medium (IGM), including the accretion of baryonic matter and dark matter particles. The variations of the thermal history of the IGM caused by accreting PBHs will result in the changes of the global 21-cm signal in the cosmic dawn. Based on the detection of the global 21-cm signal by EDGES, by requiring the differential brightness temperature, e.g., $\delta \lesssim -100(-50)\mathrm{mK}$, we obtain the upper limits on the abundance of PBHs for the mass range $10\lesssim M_{\mathrm{PBH}}\lesssim {10}^4{M}_{\odot }$. Compared with previous works, the limits are stronger for the mass range $10\lesssim M_{\mathrm{PBH}}\lesssim 50M_{\odot }$.

We elaborate on the correspondence between the canonical partition function in asymptotically AdS universes and the no-boundary proposal for positive vacuum energy. For the case of a pure cosmological constant, the analytic continuation of the AdS partition function is seen to define the no-boundary wave function (in dS) uniquely in the simplest minisuperspace model. A consideration of the AdS gravitational path integral implies that on the dS side, saddle points with Hawking-Moss/Coleman-De Luccia-type tunneling geometries are irrelevant. This implies that simple topology changing geometries do not contribute to the nucleation of the universe. The analytic AdS/dS equivalence holds up once tensor fluctuations are added. It also works, at the level of the saddle point approximation, when a scalar field with a mass term is included, though in the latter case, it is the mass that must be analytically continued. Our results illustrate the emergence of time from space by means of a Stokes phenomenon, in the case of positive vacuum energy. Furthermore, we arrive at a new characterization of the no-boundary condition, namely that there should be no momentum flux at the nucleation of the universe.

New physics increasing the expansion rate just prior to recombination is among the least unlikely solutions to the Hubble tension and would be expected to leave an important signature in the early integrated Sachs-Wolfe (eISW) effect, a source of cosmic microwave background (CMB) anisotropies arising from the time variation of gravitational potentials when the Universe was not completely matter dominated. Why, then, is there no clear evidence for new physics from the CMB alone, and why does the $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model fit CMB data so well? These questions and the vastness of the Hubble tension theory model space provide the motivation for general consistency tests of $\mathrm{\Lambda }\mathrm{CDM}$. I perform an eISW-based consistency test of $\mathrm{\Lambda }\mathrm{CDM}$ introducing the parameter $A_{\mathrm{eISW}}$, which rescales the eISW contribution to the CMB power spectra. A fit to Planck CMB data yields $A_{\mathrm{eISW}}=0.988\pm 0.027$, in perfect agreement with the $\mathrm{\Lambda }\mathrm{CDM}$ expectation $A_{\mathrm{eISW}}=1$ and posing an important challenge for early-time new physics, which I illustrate in a case study focused on early dark energy (EDE). I explicitly show that the increase in ${\omega }_c$ needed for EDE to preserve the fit to the CMB, which has been argued to worsen the fit to weak lensing and galaxy clustering measurements, is specifically required to lower the amplitude of the eISW effect, which would otherwise exceed $\mathrm{\Lambda }\mathrm{CDM}$’s prediction by $\approx 20\%$: this is a generic problem beyond EDE that likely applies to most models enhancing the expansion rate around recombination. Early-time new physics models invoked to address the Hubble tension are therefore faced with the significant challenge of making a similar prediction to $\mathrm{\Lambda }\mathrm{CDM}$ for the eISW effect while not degrading the fit to other measurements in doing so.

The marginally stable circular orbits (MSCOs) of test particles in the spacetime exterior to a charged Kiselev black hole are investigated for three characteristic values of the equation of state parameter ${\omega }_q$, namely (i) ${\omega }_q=-1/3$, (ii) ${\omega }_q=-1$, and (iii) ${\omega }_q=-2/3$, and for different values of the normalization factor $\alpha$ and electric charge $Q$ of the black hole. It is found that the presence of the quintessence field shifts outward the innermost stable circular orbits (ISCOs) around the Kiselev black hole, having the same charge parameter $Q$, as compared to the ISCOs around a Riessner-Nordstrom black hole, while the effect of the quintessence field on the outermost stable circular orbits (OSCOs) is just opposite to that on the ISCOs. Further, the radii of the photon circular orbits are also calculated for different ranges of the parameters $\alpha$ and $Q$. It is observed that the photon orbits are also shifted outward as the value of $\alpha$ increases. The radial and latitudinal epicyclic motion of test particles, which can be related to the quasiperiodic oscillations of test particles slightly above the MSCOs in the vicinity of the charged Kiselev black hole, is analyzed for the three different values of ${\omega }_q$. It is seen that the azimuthal and latitudinal frequencies coincide, and the radial epicyclic frequency is different in dependence on the spacetime parameters. In the case of ${\omega }_q=-1/3$, the azimuthal and latitudinal frequencies depend on the radial position $r$ of the particle, the charge $Q$, and the mass $M$ of the black hole, and do not depend on the factor $\alpha$. However, for ${\omega }_q=-2/3$ and ${\omega }_q=-1$, these two frequencies, along with the black hole parameters—i.e., $M$ and $Q$ and the radial position $r$—also depend on the factor $\alpha$. The radial epicyclic frequency for all the values of ${\omega }_q$ depends on $M$, $Q$, $r$, and also on the normalization factor $\alpha$. We also compare the epicyclic frequencies with that for an uncharged black hole. With the increase of electric charge, the ISCO becomes closer to the central object, and one can observe epicyclic frequencies closer to the central object, which makes the epicyclic frequencies larger. The ISCO gets larger as $\alpha$ increases, and thus the epicyclic frequencies can be observed away from the central object and would be smaller as compared to the case of a pure Riessner-Nordstrom black hole without quintessence. As the effect of the parameters $Q$ and $\alpha$ on the OSCOs is just opposite to that on the ISCOs, the epicyclic frequencies near the OSCOs behave the other way around.

Long-term neutrino-radiation resistive-magnetohydrodynamics simulations in full general relativity are performed for a system composed of a massive neutron star and a torus formed as a remnant of binary neutron-star mergers. The simulation is performed in axial symmetry incorporating a mean-field dynamo term for a hypothetical amplification of the magnetic-field strength. We first calibrate the mean-field dynamo parameters by comparing the results for the evolution of black hole–disk systems with viscous hydrodynamics results. We then perform simulations for the system of a remnant massive neutron star and a torus. As in the viscous hydrodynamics case, the mass ejection occurs primarily from the torus surrounding the massive neutron star. The total ejecta mass and electron fraction in the new simulation are similar to those in the viscous hydrodynamics case. However, the velocity of the ejecta can be significantly enhanced by magnetohydrodynamics effects caused by global magnetic fields.

Gravitational wave backgrounds generate correlated noises to separated detectors. This correlation can induce statistical losses to actual detector networks, compared with idealized noise-independent networks. Assuming that the backgrounds are isotropic, we examine the statistical losses specifically for the angular averaged sensitivity curves, and derive simple expressions that depend on the overlap reduction functions and the strength of the background noises relative to the instrumental noises. For future triangular interferometers such as ET and LISA, we also discuss preferred network geometries to suppress the potential statistical losses.