Recently, the action growth rate of a variety of four-dimensional regular magnetic black holes in the $\mathcal{F}$ frame was obtained by El Moumni and Masmar [Nucl. Phys. B950, 114837 (2020)]. Here, we study the action growth rate of a four-dimensional regular electric black hole in the $\mathcal{P}$ frame that is the Legendre transformation of the $\mathcal{F}$ frame. We also investigate the action growth rates of the Wheeler–De Witt patch for such black hole configurations at the late time and examine the Lloyd bound on the rate of quantum computation. We show that although the form of the Lloyd bound formula remains unaltered, the energy modifies due to a nonvanishing trace of the energy-momentum tensor, and some extra terms may appear in the total growth action. We also investigate the asymptotic behavior of complexity in two conjectures for static and rotating regular black holes.

In general relativity it is difficult to work with the concept of a classical phenomenological spring model since it involves action at a distance. We propose a toy relativistic model exhibiting oscillatory behavior and investigate its motion in selected gravitational fields. The simple model can be used to study the behavior of extended objects falling freely in a background gravitational field. Unlike previous glider-type models, the present system only involves local interaction, avoiding thus the pitfalls of superluminal motion. Moreover, it locally satisfies energy-momentum conservation.

In a search for the effects of quintessence dark energy on the kinetics of black hole phase transition, we investigate in detail the dynamic phase transition of charged anti–de Sitter black holes surrounded by quintessence in this paper. We compare the case with dark energy and the case without dark energy. It is shown that the initial black hole state evolves more quickly in the case with dark energy than in the case without dark energy, no matter what the initial black hole state is. The result concerning the first passage process further supports this finding. The transition from the large (small) black hole state to the small (large) black hole state happens quickly. Last but not least, we calculate the mean first passage time for various choices of parameter ${\omega }_q$. It is shown that the mean first passage time for the case with dark energy is much shorter than that of the case without dark energy, which can be understood by the result that the height of the barrier of Gibbs free energy for the case with dark energy is lower than that of the case without dark energy. Interestingly enough, the effect of dark energy is quite unique. For the range of ${\omega }_q$, there exists a minimum mean first passage time. With the increasing of ${\omega }_q$ from $-0.99$ to $-0.34$, the mean first passage time decreases dramatically and then increases. Considering the mean first passage time is an observable of black hole dynamic phase transition, the unique results we obtain here may shed new light on constraining the parameters of the quintessence dark energy theory based on future observations.

This is the first of two papers studying localization of massive bulk fields on a bane in 5D anti–de Sitter spacetime, and some of their cosmological consequences. Here we focus on a massive 5D scalar, which is known to lack a localized mode, and discuss how a seeming discontinuity between this theory and the massless theory—known to support a localized zero mode—is resolved thanks to peculiar analytic properties of the massive two-point amplitude. Furthermore, we propose a boundary term that leads to the emergence of a massless localized mode in the massive theory. Last but not least, we consider the case when the brane world volume is de Sitter spacetime, and prove the existence of a localized massive mode. We discuss how these results, taken collectively, can be used to describe the accelerated expansion due to the massive 5D scalar field in an early, or in a late-time universe.

The effective one-body formalism of the gravitational two-body problem in general relativity is reconsidered in the light of recent scattering amplitude calculations. Based on the kinematic relationship between momenta and the effective potential, we consider an energy-dependent effective metric describing the scattering in terms of an effective one-body problem for the reduced mass. The identification of the effective metric simplifies considerably in isotropic coordinates when combined with a redefined angular momentum map. While the effective energy-dependent metric as expected is not unique, solutions can be chosen perturbatively in the post-Minkowskian expansion without the need to introduce nonmetric corrections. By a canonical transformation, our condition maps to the one based on the standard angular momentum map. Expanding our metric around the Schwarzschild solution we recover the solution based on additional nonmetric contributions.

We study single-field inflationary models with steep steplike features in the potential that lead to the temporary violation of the slow-roll conditions during the evolution of the inflaton. These features enhance the power spectrum of the curvature perturbations by several orders of magnitude at certain scales and also produce prominent oscillatory patterns. We study analytically and numerically the inflationary dynamics. We describe quantitatively the size of the enhancement, as well as the profile of the oscillations, which are shaped by the number and position of the features in the potential. The induced tensor power spectrum inherits the distinctive oscillatory profile of the curvature spectrum and is potentially detectable by near-future space interferometers. The enhancement of the power spectrum by steplike features, though significant, may be insufficient to trigger the production of a sizable number of primordial black holes if radiation dominates the energy density of the early Universe. However, it can result in sufficient black hole production if the Universe is dominated by nonrelativistic matter. For the latter scenario, we find that deviations from the standard monochromatic profile of the mass spectrum of primordial black holes are possible because of the multiple-peak structure of the curvature power spectrum.

The Universe’s initial conditions—in particular, baryon and cold dark matter (CDM) isocurvature perturbations—are poorly constrained on sub-Mpc scales. In this paper, we develop a new formalism to compute the effect of small-scale baryon perturbations on the mean free-electron abundance, and thus on cosmic microwave background (CMB) anisotropies. Our framework can accommodate perturbations with arbitrary time and scale dependence. We apply this formalism to four different combinations of baryon and CDM isocurvature modes, and we use Planck CMB-anisotropy data to probe their initial amplitude. We find that Planck data is consistent with no small-scale isocurvature perturbations, and that this additional ingredient does not help to alleviate the Hubble tension. We set upper bounds to the dimensionless initial power spectrum ${\mathrm{\Delta }}_{\mathcal{I}}^2(k)$ of these isocurvature modes at comoving wave numbers $1{\mathrm{Mpc}}^{-1}\le k\le {10}^3{\mathrm{Mpc}}^{-1}$, for several parametrizations. For a scale-invariant power spectrum, our 95% confidence-level limits on ${\mathrm{\Delta }}_{\mathcal{I}}^2$ are 0.023 for pure baryon isocurvature, 0.099 for pure CDM isocurvature, 0.026 for compensated baryon-CDM perturbations, and 0.009 for joint baryon-CDM isocurvature perturbations. Using a Fisher analysis generalized to nonanalytic parameter dependence, we forecast that a CMB Stage-4 experiment would be able to probe small-scale isocurvature perturbations with initial power 3 to 10 times smaller than Planck limits. The formalism introduced in this work is very general and can be used more widely to probe any physical processes or initial conditions sourcing small-scale baryon perturbations.

Goryachev et al. [M. Goryachev, W. M. Campbell, I. S. Heng, S. Galliou, E. N. Ivanov, and M. E. Tobar, Phys. Rev. Lett. 127, 071102 (2021)] recently announced the detection of “two strongly significant events” in their bulk acoustic wave high frequency gravitational wave antenna. They claim many possibilities for the cause of these events, including high-frequency megahertz gravitational waves. We demonstrate these events are not due to gravitational waves for two reasons. (i) The inferred stochastic gravitational-wave background from these events implies the gravitational-wave energy density of the Universe is ${\mathrm{\Omega }}_{\mathrm{gw}}\approx {10}^8$, approximately ${10}^8$ times the closure density of the Universe. (ii) The low-frequency gravitational-wave memory signal that accompanies any high-frequency gravitational-wave source visible by the current generation of high-frequency detectors would have been visible by LIGO/Virgo as a transient burst with signal-to-noise ratio $\gtrsim {10}^6$. The nondetection of such loud memory bursts throughout the operation of LIGO/Virgo rules out the gravitational-wave explanation for the high-frequency events detected by Goryachev et al. We discuss broader implications of this work for the ongoing experimental search for ultra high-frequency (MHz-GHz) gravitational waves.

We present new equilibrium solutions of stationary models of magnetized thick disks (or tori) around Kerr black holes with synchronized scalar hair. The models reported here largely extend our previous results based on constant radial distributions of the specific angular momentum along the equatorial plane. We introduce a new way to prescribe the distribution of the disk’s angular momentum based on a combination of two previous proposals and compute the angular momentum distribution outside the equatorial plane by resorting to the construction of von Zeipel cylinders. We find that the effect of the scalar hair on the black hole spacetime can yield significant differences in the disk morphology and properties compared to what is found if the spacetime is purely Kerr. Some of the tori built within the most extreme, background hairy black hole spacetime of our sample exhibit the appearance of two maxima in the gravitational energy density which impacts the radial profile distributions of the disk’s thermodynamical quantities. The models reported in this paper can be used as initial data for numerical evolutions with general relativistic magnetohydrodynamic codes to study their stability properties. Moreover, they can be employed as illuminating sources to build shadows of Kerr black holes with scalar hair which might help further constrain the no-hair hypothesis as new observational data are collected.

We investigate the prospects for discovering axionlike particles (ALPs) via a light by light scattering at two colliders, the future circular collider (FCC-ee) and circular electron-positron collider (CEPC). The promising sensitivities to the effective ALP-photon coupling $g_{a\gamma \gamma }$ are obtained. Our numerical results show that the FCC-ee and CEPC might be more sensitive to the ALPs with mass 2–8 GeV than the LHC and CLIC.

We probe the rare semileptonic decays $B_{(s)}\to K_2^{*}(1430)(f_2^{\prime }(1525)){\ell }^{+}{\ell }^{-}$ proceeding via $b\to s\ell \ell$ transition in the presence of a light $Z^{\prime }$ boson. We employ the presence of an additional vector-type interaction and constrain the new physics coupling parameter using the existing experimental measurements on $R_K$ and $R_{K^{*}}$ observables. To understand the sensitivity of the new physics coupling, we investigate the impact of this coupling on various physical observables such as differential branching ratio, the forward-backward asymmetry, the lepton polarization asymmetry, the angular observable $P_5^{\prime }$, and the lepton universality parameters such as the ratio of the branching ratio $R_{f_2^{\prime }(K_2^{*})}$ and some important Q parameters of $B_{(s)}\to K_2^{*}(1430)(f_2^{\prime }(1525)){\ell }^{+}{\ell }^{-}$ processes at large recoil. We find some noticeable differences of the observables in the presence of light $Z^{\prime }$ contribution.

We consider a composite Higgs model based on the $SU(6)/Sp(6)$ coset, where an $U(1)$ subgroup of $Sp(6)$ is identified as the flavor symmetry. A complex scalar field $s$, which is a pseudo-Nambu-Goldstone boson of the broken symmetry, carries a flavor charge and plays the role of a flavon field. The $U(1{)}_F$ flavor symmetry is then broken by a VEV of the flavon field, which leads to a small parameter and generates the mass hierarchy between the top and bottom quarks. A light flavon below the TeV scale can be naturally introduced, which provides a fully testable model for the origin of flavor hierarchy. A light flavon also leads to substantial flavor changing neutral currents, which are strongly constrained by the flavor experiments. The direct search of additional scalar bosons can also be conducted in HL-LHC and future hadron colliders.

We construct a new holographic description of QCD using domain wall fermions. The construction consists of probe D7 branes in a D5 brane geometry describing quarks on a $(4+1)$-dimensional defect in a $(5+1)$-dimensional gauge theory. We then compactify one dimension of the D5 to introduce confinement in the gauge degrees of freedom. In addition we allow a spatial dependent mass term for the D7 brane quarks to isolate chiral fermions on $(3+1)$-dimensional domain walls. The D7 world volume fields, when restricted to the domain wall position, provide an AdS/QCD description. We compute the spectrum and compare to data. We include higher dimension operators to systematically improve the description.

We extend our previous calculations of the hadronic light-by-light scattering contribution to the muon anomalous magnetic moment in holographic QCD to models with finite quark masses and a tower of massive pions. Analyzing the role of the latter in the Wess-Zumino-Witten action, we show that the Melnikov-Vainshtein short-distance constraint is satisfied solely by the summation of contributions from the infinite tower of axial-vector meson contributions. There is also an enhancement of the asymptotic behavior of pseudoscalar contributions when their infinite tower of excitations is summed, but this leads only to subleading contributions for the short-distance constraints on light-by-light scattering. We also refine our numerical evaluations, particularly in the pion and $a_1$ sector, which corroborates our previous findings of contributions from axial-vector mesons that are significantly larger than those adopted for the effects of axials and short-distance constraints in the recent white paper on the Standard Model prediction for $(g-2{)}_{\mu }$.

We study chaos in non-Lorentzian field theories, specifically Galilean and Carrollian conformal field theories in two dimensions. In a large central charge limit, we find that the Lyapunov exponent saturates the bound on chaos, conjectured originally for relativistic field theories. We recover the same Lyapunov exponent holographically by a shock-wave calculation in three-dimensional flat space cosmologies, providing further evidence for flat space holography.

The variational method is a powerful approach to solve many-body quantum problems nonperturbatively. However, in the context of relativistic quantum field theory, it needs to meet three seemingly incompatible requirements outlined by Feynman: extensivity, computability, and lack of UV sensitivity. In practice, variational methods break one of the three, which translates into the need to have an IR or UV cutoff. In this letter, I introduce a relativistic modification of continuous matrix product states that satisfies the three requirements jointly in $1+1$ dimensions. I apply it to the self-interacting scalar field, without UV cutoff and directly in the thermodynamic limit. Numerical evidence suggests the error decreases faster than any power law in the number of parameters, while the cost remains only polynomial.

The shrinking of the bottomonium spectral function towards narrow quasiparticle states in a cooling strong-interaction medium at finite baryon density is followed within a holographic bottom-up model. The five-dimensional Einstein-dilaton-Maxwell background is adjusted to the lattice-QCD results of sound velocity and susceptibilities. The zero-temperature bottomonium spectral function is adjusted to the experimental $\mathrm{\Upsilon }$ ground state mass and the first radial excitations. At baryo-chemical potential ${\mu }_B=0$, these two pillars let emerge the narrow quasiparticle state of the $\mathrm{\Upsilon }$ ground state at a temperature of about 150 MeV. Excited states are consecutively formed at lower temperatures by about 10 (20) MeV for the $2S$ ($3S$) vector states. The baryon density, i.e., ${\mu }_B>0$, pulls that formation pattern to lower temperatures. At ${\mu }_B=200\mathrm{MeV}$, we find a shift by about 15 MeV.

We consider $\mathcal{N}=1$ superconformal field theories in three dimensions possessing a conserved current multiplet ${\mathcal{F}}_{({\alpha }_1{\alpha }_2{\alpha }_3{\alpha }_4)}$, which we refer to as the superspin-2 current multiplet. At the component level it contains a conserved spin-2 current different from the energy-momentum tensor and a conserved fermionic higher-spin current of spin $5/2$. Using a superspace formulation, we calculate correlation functions involving $\mathcal{F}$, focusing particularly on the three-point function $⟨\mathcal{F}\mathcal{F}\mathcal{F}⟩$. After imposing the constraints arising from conservation equations and invariance under permutation of superspace points, we find that the parity-even and parity-odd sectors of this three-point function are each fixed up to a single coefficient. The presence of the parity-odd contribution is rather nontrivial, as there is an apparent tension between supersymmetry and the existence of parity-odd structures.

Schwarzschild black-hole interiors border on spacelike singularities representing classical information leaks. We show that local quantum physics is decoupled from these leaks due to dynamically generated boundaries, called Zeno borders. Beyond Zeno borders black-hole interiors become asymptotically silent, and quantum fields evolve freely toward the geodesic singularity with vanishing probability measure for populating the geodesic boundary. Thus Zeno borders represent a probabilistic completion of Schwarzschild black holes within the semiclassical framework.