Ultralight axions are theoretically interesting and phenomenologically rich dark sector candidates, but they are difficult to track across cosmological timescales because of their fast oscillations. We resolve this problem by developing a novel method to evolve them efficiently and accurately. We first construct an exact effective fluid which at late times matches the axion but which evolves in a simple way. We then approximate this evolution with a carefully chosen equation of state and sound speed. With our scheme we find that we can obtain subpercent accuracy for the linear theory suppression of axion density fluctuations relative to that of cold dark matter without tracking even a single complete oscillation of the axion field. We use our technique to test other approximation schemes and to provide a fitting formula for the transfer function for the matter power spectrum in linear theory in axion models. Implementing our approach in existing cosmological axion codes is straightforward and will help unleash the potential of high-precision next-generation experiments.

Fuzzy dark matter (FDM) models admit self-similar solutions which are very different from the standard cold dark matter (CDM) self-similar solutions and do not converge to the latter in the semiclassical limit. In contrast with the familiar CDM hierarchical collapse, they correspond to an inverse-hierarchy blowup. Constant-mass shells start in the nonlinear regime, at early times, with small radii and high densities, and expand to reach at late times the Hubble flow, up to small linear perturbations. Thus, larger masses become linear first. This blowup approximately follows the Hubble expansion, so that the central density contrast remains constant with time, although the width of the self-similar profile shrinks in comoving coordinates. As in a gravitational cooling process, matter is ejected from the central peaks through successive clumps. As in wave systems, the velocities of the geometrical structures and of the matter do not coincide, and matter slowly moves from one clump to the next, with intermittent velocity bursts at the transitions. These features are best observed using the density-velocity representation of the nonrelativistic scalar field, or the mass-shell trajectories, than with the Husimi phase-space distribution, where an analog of the Heisenberg uncertainty principle blurs the resolution in the position or velocity direction. These behaviors are due to the quantum pressure and the wavelike properties of the Schrödinger equation. Although the latter has been used as an alternative to $N$-body simulations for CDM, these self-similar solutions show that the semiclassical limit needs to be handled with care.

The power spectrum of weak lensing fluctuations has a non-Gaussian distribution due to its quadratic nature. On small scales the central limit theorem acts to Gaussianize this distribution but non-Gaussianity in the signal due to gravitational collapse is increasing and the functional form of the likelihood is unclear. Analyses have traditionally assumed a Gaussian likelihood with nonlinearity incorporated into the covariance matrix; here we provide the theory underpinning this assumption. We calculate, for the first time, the leading-order correction to the distribution of angular power spectra from non-Gaussianity in the underlying signal and study the transition to Gaussianity. Our expressions are valid for an arbitrary number of correlated maps and correct the Wishart distribution in the presence of weak (but otherwise arbitrary) non-Gaussianity in the signal. Surprisingly, the resulting distribution is not equivalent to an Edgeworth expansion. The leading-order effect is to broaden the covariance matrix by the usual trispectrum term, with residual skewness sourced by the trispectrum and the square of the bispectrum. Using log-normal lensing maps we demonstrate that our likelihood is uniquely able to model both large and mildly nonlinear scales. We provide easy-to-compute statistics to quantify the size of the non-Gaussian corrections. We show that the full non-Gaussian likelihood can be accurately modeled as a Gaussian on small, nonlinear scales. On large angular scales nonlinearity in the lensing signal imparts a negligible correction to the likelihood, which takes the Wishart form in the full-sky case. Our formalism is equally applicable to any kind of projected field.

In this paper, we calculate the ratio of Cabibbo-Kobayashi-Maskawa matrix elements, $|V_{ub}|/|V_{cb}|$, based on the semileptonic decay $B_s^0\to K^{-}{\mu }^{+}{\nu }_{\mu }$. Its key component, the $B_s\to K$ transition form factor $f_{+}^{B_s\to K}(q^2)$, is studied within the QCD light-cone sum rules approach by using a chiral correlator. The derived $f_{+}^{B_s\to K}(q^2)$ is dominated by the leading-twist part, and to improve its precision, we construct a new model for the kaon leading-twist distribution amplitude ${\varphi }_{2;K}(x,\mu )$, whose parameters are fixed by using the least-squares method with the help of the moments calculated by using the QCD sum rules within the background field theory. The first four moments at the initial scale ${\mu }_0=1\mathrm{GeV}$ are $⟨{\xi }^1{⟩}_{2;K}=-0.0438_{-0.0075}^{+0.0053}$, $⟨{\xi }^2{⟩}_{2;K}=0.262\pm 0.010$, $⟨{\xi }^3{⟩}_{2;K}=-0.0210_{-0.0035}^{+0.0024}$, and $⟨{\xi }^4{⟩}_{2;K}=0.132\pm 0.006$, respectively. And the corresponding Gegenbauer moments are $a_1^{2;K}=-0.0731_{-0.0124}^{+0.0089}$, $a_2^{2;K}=0.182_{-0.030}^{+0.029}$, $a_3^{2;K}=-0.0114_{-0.0016}^{+0.0008}$, and $a_4^{2;K}=0.041_{+0.005}^{-0.003}$, respectively. At the large recoil region, we obtain $f_{+}^{B_s\to K}(0)=0.270_{-0.020}^{+0.025}$. By extrapolating $f_{+}^{B_s\to K}(q^2)$ to all the physical allowable region, we obtain a $|V_{ub}|$-independent decay width for the semileptonic decay $B_s^0\to K^{-}{\mu }^{+}{\nu }_{\mu }$, ${5.626}_{-0.864}^{+1.292}\times {10}^{-12}\mathrm{GeV}$, which then leads to $|V_{ub}|/|V_{cb}|=0.072\pm 0.005$.

The solution of the Dirac equation in the presence of an arbitrary plane wave, corresponding to the so-called Volkov states, has provided an enormous insight in strong-field QED. In [Phys. Rev. A 103, 076011 (2021)], a new “fully quasiclassical” representation of the Volkov states has been found, which is equivalent to the one known in the literature but which more transparently shows the quasiclassical nature of the quantum dynamics of an electron in a plane-wave field. Here, we derive the corresponding expression of the propagator by constructing it using the fully quasiclassical form of the Volkov states. The found expression allows one, together with the fully quasiclassical expression of the Volkov states, to compute probabilities in strong-field QED in an intense plane wave by manipulating only 2-by-2 rather than 4-by-4 Dirac matrices as in the usual approach. Moreover, apart from the exponential functions featuring the classical action of an electron in a plane wave, the fully quasiclassical Volkov propagator depends only on the electron kinetic four-momentum in the plane wave, which is a gauge-invariant quantity. Finally, we also compute the one-loop tadpole diagram in a plane wave starting from the Volkov propagator and we find that after renormalization it identically vanishes.

Based on a model-independent framework including the vectorlike top partner (VLQ-$T$), we investigate the prospect of discovering the singlet or doublet VLQ-$T$ via the single production process $e^{-}{e}^{+}\to T\overline{t}+t\overline{T}$ with the $T\to Zt$ decay channel at a future high-energy linear $e^{+}{e}^{-}$ collider with $\sqrt{s}=3\mathrm{TeV}$. We focus on the hadronic decay of the top quark and two types of decay channels for the $Z$ boson: $Z\to {\ell }^{+}{\ell }^{-}$ and $Z\to \nu \overline{\nu }$. By carrying out a full simulation for the signals and the relevant Standard Model backgrounds, the $2\sigma$ exclusion limit and $5\sigma$ discovery prospects are, respectively, obtained on the VLQ-$T$ mass and the coupling strength $g^{*}$ with the integrated luminosity of $5{\mathrm{ab}}^{-1}$. In addition, we considered the initial state radiation and beamstrahlung effects as well as the systematic uncertainty effects of backgrounds, which are found to reduce the excluding or discovery capability.

In recent years, the sensitivity of optomechanical force sensors has improved leading to increased interest in using these devices as particle detectors. In this study we consider scenarios where dark matter with mass close to the Planck scale may be probed by a large array of optomechanical accelerometers. We motivate a macroscopic mechanical search for ultraheavy dark matter, exemplified by the efforts of the Windchime Collaboration, by providing a survey of the model space that would be visible to such a search. We consider two classes of models, one that invokes a new long-range unscreened force and another that is only gravitationally interacting. We identify significant regions of well-motivated, potentially visible parameter space for versatile models such as Q-balls, composite dark matter, relics of gravitational singularities, and gravitationally produced ultraheavy particles.

Exclusive production of light vector mesons in deep inelastic scattering is calculated at next-to-leading order in the dipole picture in the limit of high photon virtuality. The resulting expression is free of any divergences and suitable for numerical evaluations. The higher-order corrections are found to be numerically important, but they can be mostly captured by the nonperturbative fit parameters describing the initial condition for the small-$x$ evolution of the dipole scattering amplitude. The vector meson production cross section is shown to depend only weakly on the meson distribution amplitude and the factorization scale. We also present phenomenological comparisons of our result to the existing exclusive $\varphi$ and $\rho$ production data from HERA and find an excellent agreement at high virtualities.

The rare $b\to s\nu \overline{\nu }$ decays are sensitive to contributions of new physics (NP) and are helpful to resolve the puzzle of multiple $B$ flavor anomalies. In this work, we propose to study the $b\to s\nu \overline{\nu }$ transition at a future lepton collider operating at the $Z$ pole through the $B_s\to \varphi \nu \overline{\nu }$ decay. Using the $B_s\to \varphi$ decay form factors from lattice simulations, we first update the standard model (SM) prediction of $\mathrm{BR}(B_s\to \varphi \nu \overline{\nu }{)}_{\mathrm{SM}}=(9.93\pm 0.72)\times {10}^{-6}$ and the corresponding $\varphi$ longitudinal polarization fraction $F_{L,\mathrm{SM}}=0.53\pm 0.04$. Our analysis uses the full Circular Electron-Positron Collider (CEPC) simulation samples with a net statistic of $\mathcal{O}({10}^9)$ $Z$ decays. Precise $\varphi$ and $B_s$ reconstructions are used to suppress backgrounds. The results show that $\mathrm{BR}(B_s\to \varphi \nu \overline{\nu })$ can be measured with a statistical uncertainty of $\mathcal{O}(\%)$ and an $S/B$ ratio of $\mathcal{O}(1)$ at the CEPC. The quality measures for the event reconstruction are also derived. By combining the measurement of $\mathrm{BR}(B_s\to \varphi \nu \overline{\nu })$ and $F_L$, the constraints on the effective theory couplings at low energy are given.

Schwarzschild–de Sitter black holes have two horizons that are at different temperatures for generic values of the black hole mass. Since the horizons are out of equilibrium, the solutions do not admit a smooth Euclidean continuation, and it is not immediately clear what role they play in the gravitational path integral. We show that Euclidean Schwarzschild–de Sitter is a genuine saddle point of a certain constrained path integral, providing a consistent Euclidean computation of the probability $\sim e^{-(S_{dS}-S_{SdS})}$ to find a black hole in the de Sitter bath.

Recently, a new procedure to quantize the $SU(N)$ Yang-Mills theory in the nonperturbative regime was proposed. The idea is to divide the configuration space $\{A_{\mu }\}$ into sectors labeled by different topological degrees of freedom and fix the gauge separately on each one of them. As Singer’s theorem on gauge copies only refers to gauge fixing conditions that are global in $\{A_{\mu }\}$, this construction might avoid the Gribov problem. In this work, we present a proof of the renormalizability in the center-vortex sectors, thus establishing the calculability of the Yang-Mills center-vortex ensemble.

In this paper we study the quantum Brownian motion of a scalar point particle in the analog Friedman-Robertson-Walker spacetime in the presence of a disclination, in a condensed matter system. The analog spacetime is obtained as an effective description of a Bose-Einstein condensate in terms of quantum excitations of sound waves, named phonons. The dynamics of the phonons is described by a massless real scalar field whose modes are also subjected to a quasiperiodic condition. In this sense, we find exact solutions for the real scalar field in this scenario and calculate the two-point function which makes it possible to analyze the mean squared velocity dispersion of the particle in all directions. We thus analyze some interesting particular cases and show some graphs where it is possible to see the consistency of our results.

A black hole as an elementary particle is a fairly glamorous idea. For ordinary black holes, a surrounding particle inevitably penetrates into the interior of the hole since the center of the hole is an infinite potential well. For the first time, we demonstrate that an extreme dilatonic black hole in spherical symmetry perfectly behaves as an atom, in the sense that its surrounding cloud of particles is completely stable. Thus we reach a spherical cloud of a dilatonic black hole. We find exact wave functions of the cloud for the arbitrary gravitational fine structure constant $\mu M$ and clear the underlying physical nature of the stability. Through careful studies of the exact wave function, we find the spectrum of this system. We discuss the physical meaning of this discovery, especially from considerations of entropy, and the resultant possibility to explore quantization of gravitational waves from coming observations.

The study of the primordial black hole (PBH) gravitational collapse process requires the determination of a critical energy density perturbation threshold ${\delta }_{\mathrm{c}}$, which depends on the equation of state of the universe at the time of PBH formation. Up to now, the majority of analytical and numerical techniques calculate ${\delta }_{\mathrm{c}}$ by assuming a constant equation-of-state (EoS) parameter $w$ at the time of PBH formation. In this work, after generalizing the constant $w$ prescription of [T. Harada et al., Phys. Rev. D 88, 084051 (2013); T. Harada et al.Phys. Rev. D89, 029903(E) (2014).] for the computation of ${\delta }_{\mathrm{c}}$ and commenting its limitations we give a first estimate for the PBH threshold in the case of a time-dependent $w$ background. In particular, we apply our formalism in the case of the QCD phase transition, where the EoS parameter varies significantly with time and one expects an enhanced PBH production due to the abrupt softening of $w$. At the end, we compare our results with analytic and numerical approaches for the determination of ${\delta }_{\mathrm{c}}$ assuming a constant EoS parameter.

We present a procedure to link the deformation parameter $\beta$ of the generalized uncertainty principle (GUP) to the two free parameters $\tilde{\omega }$ and $\gamma$ of the running Newtonian coupling constant of the asymptotically safe gravity program. To this aim, we compute the Hawking temperature of a black hole in two different ways. The first way involves the use of the GUP in place of the Heisenberg uncertainty relations, and therefore we get a deformed Hawking temperature containing the parameter $\beta$. The second way involves the deformation of the Schwarzschild metric due to the Newtonian coupling constant running according to the asymptotically safe gravity prescription. The comparison of the two techniques yields a relation between $\beta$ and $\tilde{\omega }$, $\gamma$. As a particular case, we discuss also the so-called $\xi$-model. The relations between $\beta$ and $\tilde{\omega }$, $\xi$ allow us to transfer upper bounds from one parameter to the others.

Some parts of the accretion model of the Jovian planets’ formation are studied in the context of Palatini gravity. We mainly focus on the critical core mass, that is, a mass for which there is no hydrostatic equilibrium solution for the planet’s envelope, which is a starting point for the runaway accretion. We also discuss the conditions a planet needs to satisfy such that it can possess a massive gaseous envelope around a solid core.

Boson stars are stationary, axially symmetric solutions of a complex scalar field theory coupled to gravity. Recently, multisolitonic configurations interpreted as static chains of multiple boson stars bound by gravity and carrying no angular momentum were reported. We propose to generalize those solutions to the stationary case by constructing chains of rotating boson stars and analyze their properties. The nonlinear elliptic field equations are solved using the finite element method. We find that chains with an even number of constituents exhibit the same spiral-like frequency dependence of their mass, angular momentum and Noether charge as single boson stars. In contrast, sequences of chains with an odd number of constituents show nontrivial loops starting and ending at the flat vacuum. As a consequence, such solutions cannot be uniquely parametrized by a single parameter. We conjecture that all rotating chains correspond to excitations of single boson stars or pairs of them. We also analyze their flat space limit and find that they reduce to chains of $Q$-balls.

We study scalar test-field perturbations on top of a Kerr–black-bounce background, i.e., a family of rotating regular black holes and/or rotating traversable wormholes that can mimic Kerr black holes. We compute the quasinormal modes for a massless field in both the regular black holes and wormhole branches, confirming the stability of the former and identifying a set of growing modes that renders the latter unstable. We further compute the superradiance amplification factors, for massless and massive fields, in the regular black hole branch, confirming that these objects superradiate, though to a lesser degree than the corresponding Kerr black holes.

We consider extreme mass ratio inspirals during which an electrically charged compact object with mass $m_p$ and the charge to mass ratio $q$ inspirals around a Schwarzschild black hole of mass $M$. Using the Teukolsky and generalized Sasaki-Nakamura formalisms for the gravitational and electromagnetic perturbations around a Schwarzschild black hole, we numerically calculate the energy flux of both gravitational and electromagnetic waves induced by a charged particle moving in circular orbits. With one year observation of these extreme mass ratio inspirals, we show that a space-based gravitational wave detector such as the Laser Interferometer Space Antenna can detect the charge to mass ratio as small as $q\sim {10}^{-3}$.