A configuration of a test magnetic field in Hayward spacetime is obtained by solving Maxwell’s equation with the Hayward metric as the background. The magnetic field lines show a dipole looplike configuration in the regular Hayward interior, and tends to an asymptotically uniform structure away from the cylindrical axis. The motion of charged particles is then studied in this spacetime. The parameters and stability of circular orbits on the equatorial plane are studied. Aspects of nonequatorial motion are also studied.

We investigate entanglement production by inhomogeneous perturbations over a homogeneous and isotropic cosmic background, demonstrating that the interplay between quantum and geometric effects can have relevant consequences on entanglement entropy, with respect to homogeneous scenarios. To do so, we focus on a conformally coupled scalar field and discuss how geometric production of scalar particles leads to entanglement. Perturbatively, at first order, we find oscillations in entropy correction, whereas at second order, the underlying geometry induces mode mixing on entanglement production. We thus quantify entanglement solely due to geometrical contribution and compare our outcomes with previous findings. We characterize the geometric contribution through geometric (quasi)particles, interpreted as dark matter candidates.

Black holes binaries coming from a distribution of primordial black holes might exhibit a large merger rate up to large redshifts. Using a phenomenological model for the merger rate, we show that changes in its slope, up to redshifts $z\sim 4$, are constrained by current limits on the amplitude of the stochastic gravitational wave background from LIGO/Virgo-O3 run. This shows that the stochastic background constrains the merger rate for redshifts larger than the single event horizon of detection ($z\simeq 1$ for the same detector). Moreover, we show that for steep merger rates the shape of the stochastic gravitational wave signal at intermediate frequencies differs from the usual $2/3$ IR scaling. We discuss the implications of our model for future experiments in a wide range of frequencies, such as the design LIGO/Virgo array, Einstein Telescope, LISA, and PTA. Additionally, we show that (i) the stochastic background and the present merger rate provide equally constraining bounds on the abundance of PBHs arising from a Gaussian distribution of inhomogeneities and (ii) degeneracies at the level of the stochastic background (i.e., different merger histories leading to a similar stochastic background) can be broken by considering the complementary direct observation of the merger rate from number counts by future detectors such as the Einstein Telescope.

We investigate static and spherically symmetric solutions in the minimal theory of bigravity (MTBG). First, we show that a pair of Schwarzschild-de Sitter spacetimes with different cosmological constants and black hole masses written in the spatially flat Gullstrand-Painlevé coordinates is a solution in the self-accelerating branch of MTBG, while it cannot be a solution in the normal branch. We then illustrate how Schwarzschild-de Sitter solutions can become compatible with the normal branch when using different coordinates. We also confirm that the self-accelerating branch of MTBG admits static and spherically symmetric general relativity solutions with matter written in the spatially flat coordinates, including neutron stars with arbitrary matter equations of state. Finally, we show that in the self-accelerating branch nontrivial solutions are given by the Schwarzschild-de Sitter metrics written in nonstandard coordinates.

If a system of flavor-oscillating neutrinos is at high enough densities that neutrino-neutrino coherent forward scatterings are non-negligible, the system becomes a time-dependent many-body problem. An important and open question is whether the flavor evolution is sufficiently described by a mean-field approach or can be strongly affected by correlations arising from two-body interactions in the neutrino Hamiltonian, as measured by nontrivial quantum entanglement. Numerical computations of the time evolution of many-body quantum systems are challenging because the size of the Hilbert space scales exponentially with the number of particles $N$ in the system. Thus, it is important to investigate approximate but beyond-mean-field numerical treatments at larger values of $N$. Here we investigate the efficacy of tensor network methods to calculate the time evolution of interacting neutrinos at larger values of $N$ than are possible with conventional methods. In particular, we introduce the use of time-dependent variational principle methods to address the long-range (in momentum space) interactions of the neutrino Hamiltonian when including many distinct vacuum oscillation frequencies. We also define new error measures based upon the instantaneously conserved charge operators known for this Hamiltonian to determine validity of large-$N$ tensor network calculations.

One fundamental goal of the newly born gravitational wave astronomy is discovering the origin of the observed binary black hole mergers. Toward this end, identifying features in the growing wealth of data may help in distinguishing different formation pathways. While large uncertainties still affect the binary formation models, spin-mass relations remain characteristic features of specific classes of channels. By focusing on the effective inspiral spin ${\chi }_{\text{eff}}$, the best reconstructed spin-related merger parameter, we show that current GWTC-3 data support the hypothesis that a fraction of events may display mass-spin correlations similar to one expected by dynamical formation channels of either astrophysical or primordial nature. We quantify the Bayesian evidence in favor of those models, which are substantially preferred when compared to the Gaussian phenomenological model adopted to describe the distribution of ${\chi }_{\text{eff}}$ in the recent LIGO/Virgo/KAGRA population analyses.

The cosmic-ray fluxes of electrons and positrons ($e^{\pm }$) are measured with high precision by the space-borne particle spectrometer AMS-02. To infer a precise interpretation of the production processes for $e^{\pm }$ in our Galaxy, it is necessary to have an accurate description of the secondary component, produced by the interaction of cosmic-ray proton and helium with the interstellar medium atoms. We determine new analytical functions of the Lorentz invariant cross section for the production of ${\pi }^{\pm }$ and $K^{\pm }$ by fitting data from collider experiments. We also evaluate the invariant cross sections for several other channels, involving for example hyperon decays, contributing at the few % level on the total cross section. For all these particles, the relevant 2 and 3 body decay channels are implemented, with the polarized ${\mu }^{\pm }$ decay computed with next-to-leading order corrections. The cross section for scattering of nuclei heavier than protons is modeled by fitting data on $p+C$ collisions. The total differential cross section $d\sigma /d{T}_{e^{\pm }}(p+p\to e^{\pm }+X)$ is predicted from 10 MeV up to 10 TeV of $e^{\pm }$ energy with an uncertainty of about 5–7% in the energies relevant for AMS-02 positron flux, thus dramatically reducing the precision of the theoretical model with respect to the state of the art. Finally, we provide a prediction for the secondary Galactic $e^{\pm }$ source spectrum with an uncertainty of the same level. As a service for the scientific community, we provide numerical tables and a script to calculate energy-differential cross sections.

We consider axions coupled to nucleons and photons only through the nucleon electric-dipole moment (EDM) portal. This coupling is a model-independent feature of QCD axions, which solve the strong $CP$ problem, and might arise as well in more general axionlike particle setups. We revise the supernova (SN) axion emission induced by the nucleon EDM coupling and refine accordingly the SN 1987A bound. Furthermore, we calculate the axion flux from a future Galactic SN and show that it might produce a peculiar and potentially detectable gamma-ray signal in a large underground neutrino detector such as the proposed Hyper-Kamiokande. The possibility to detect such a signal offers a way to search for an oscillating nucleon EDM complementary to CASPERe, without relying on the assumption that axions are a sizeable component of the dark matter. Furthermore, if axions from SN produce an observable signal, they could also lead to an amount of cosmological extra radiation observable in future cosmic surveys.

Proposed future gravitational wave detectors place high demands on their prestabilized laser system. We present a prototype for such a prestabilized laser system at $1550\mathrm{nm}$ wavelength with frequency and power stabilizations optimized for the needs of gravitational wave detectors. A power stabilization with shot noise limited operation below a relative power noise of $1\times {10}^{-8}{\mathrm{Hz}}^{-1/2}$ between 100 Hz to 100 kHz and an active frequency stabilization with a unity-gain bandwidth above 2 MHz were operated simultaneously. Out-of-loop measurements are performed to characterize the achieved stability and to analyze sensor noise limits. We find that nonlinear noise couplings at the spatial mode-filter cavity are of high relevance and lead to increased frequency stability requirements above 100 kHz . This prestabilized laser system can serve as the baseline for the Einstein Telescope gravitational wave detector [ET steering committee, Design report Update 2020 for the Einstein Telescope, Technical Report, Einstein gravitational wave Telescope, 2020.] and demonstrates stabilization concepts generally applicable to optical precision experiments.

We provide a simple new argument for a lower bound on the coupling of a $U(1)$ gauge interaction in an effective field theory (EFT), originally obtained from the weak gravity conjecture. Our argument employs basic principles of quantum mechanical energy-time uncertainty and Lorentz invariance, plus Bekenstein’s entropy bound on the ultraviolet (UV) and infrared (IR) scales of an EFT. We show that using an alternative UV-IR relation based on the Cohen-Kaplan-Nelson (CKN) bound results in a stronger lower bound on the $U(1)$ coupling, consistent with the more stringent nature of the CKN relation. Applicability of our reasoning to other interactions is briefly discussed. We also slightly extend the CKN bound, by accounting for the effective degrees of freedom, and examine some of its phenomenological implications.

In this paper we develop and compare different real-time methods to calculate spectral functions. These include classical-statistical simulations, the Gaussian state approximation (GSA), and the functional renormalization group (FRG) formulated on the Keldysh closed-time path. Our test-bed system is the quartic anharmonic oscillator, a single self-interacting bosonic degree of freedom, coupled to an external heat bath providing dissipation analogous to the Caldeira-Leggett model. As our benchmark we use the spectral function from exact diagonalization with constant Ohmic damping. To extend the GSA for the open system, we solve the corresponding Heisenberg-Langevin equations in the Gaussian approximation. For the real-time FRG, we introduce a novel general prescription to construct causal regulators based on introducing scale-dependent fictitious heat baths. Our results explicitly demonstrate how the discrete transition lines of the quantum system gradually build up the broad continuous structures in the classical spectral function as temperature increases. At sufficiently high temperatures, classical, GSA, and exact-diagonalization results all coincide. The real-time FRG is able to reproduce the effective thermal mass, but it overestimates broadening and only qualitatively describes higher excitations, at the present order of our combined vertex and loop expansion. As temperature is lowered, the GSA follows the ensemble average of the exact solution better than the classical spectral function. In the low-temperature strong-coupling regime, the qualitative features of the exact result are best captured by our real-time FRG calculation, with quantitative improvements to be expected at higher truncation orders.

We investigate photon bremsstrahlung in chiral media. The chiral medium response to the magnetic field is described by the chiral magnetic current $\mathit{j}=b_0\mathit{B}$, where $b_0$ is the chiral magnetic conductivity. This current modifies the photon dispersion relation producing a resonance in the scattering amplitude. We show that the resonant contribution is proportional to the magnetic moment $\mu$ of the target nucleus. We analytically compute the corresponding cross section. We argue that the anomalous contribution is enhanced by a factor $b_0^2/{\mathrm{\Gamma }}^2$, where $\mathrm{\Gamma }$ is a width of the resonance related to the chiral magnetic instability of the electromagnetic field. The most conspicuous feature of the anomalous contribution to the photon spectrum is the emergence of the kneelike structure at photon energies proportional to $b_0$. We argue that the phenomenological significance of the anomalous terms depends on the magnitude of the ratio of $b_0$ to the projectile fermion mass.

In this work, we study the impact of electroweak and Higgs precision measurements at future electron-positron colliders on several typical supersymmetric models, including the constrained minimal supersymmetric Standard Model (CMSSM), nonuniversal Higgs mass generalizations (NUHM1, NUHM2), and the seven-dimensional minimal supersymmetric Standard Model (MSSM7). Using publicly available data from the $\mathsf{GAMBIT}$ community, we postprocess previous SUSY global fits with additional likelihoods to explore the discovery potential of Higgs factories, such as the Circular Electron Positron Collider (CEPC), the Future Circular Collider (FCC), and the International Linear Collider (ILC). We show that the currently allowed parameter space of these models will be further tested by future precision measurements. In particular, dark matter annihilation mechanisms may be distinguished by precise measurements of Higgs observables.

The long persistent discrepancies in $b\to s{\ell }^{+}{\ell }^{-}$ quark level transitions continue to be the ideal platform for an indirect search of beyond the standard model physics. The recent updated measurements of $R_K$, $\mathcal{B}(B_s\to \varphi {\mu }^{+}{\mu }^{-})$ and $\mathcal{B}(B_s\to {\mu }^{+}{\mu }^{-})$ from LHCb deviate from the standard model expectations at more than the $3\sigma$ level. Similarly, measurements of $R_{K^{*}}$ and $P_5^{\prime }$ in $B\to K^{*}{\ell }^{+}{\ell }^{-}$ decays disagree with the standard model predictions at $\sim 2.4\sigma$ and $\sim 3.3\sigma$, respectively. Moreover, recent measurement of ratio of branching ratios $R_{K_S^0}$ and $R_{K^{*+}}$ in $B^0\to K_S^0{\ell }^{+}{\ell }^{-}$ and $B^{+}\to K^{+*}{\ell }^{+}{\ell }^{-}$ decays deviate from the standard model prediction at $1.4\sigma$ and $1.5\sigma$, respectively. Considering the $R_{K_S^0}-R_{K^{*+}}$ combination, the difference with the SM predictions currently stands at about $2\sigma$. Motivated by these anomalies we search for the patterns of new physics in the family of flavor changing neutral current decays with neutral leptons in the final state undergoing $b\to s\nu \overline{\nu }$ quark level transitions. There are close relations between $b\to s{\ell }^{+}{\ell }^{-}$ and $b\to s\nu \overline{\nu }$ transition decays not only in the standard model but also in beyond the standard model physics. In beyond the standard model physics the left handed charged leptons can be related to the neutral leptons via $SU(2{)}_L$ gauge symmetry. Moreover, there are several advantages of studying $b\to s\nu \overline{\nu }$ transitions over $b\to s{\ell }^{+}{\ell }^{-}$ as they are free from various hadronic uncertainties such as the nonfactorizable corrections and photonic penguin contributions. In this context, we use the standard model effective field theory formalism and explore the consequences of $b\to s{\mu }^{+}{\mu }^{-}$ anomalies on $B\to K^{(*)}\nu \overline{\nu }$, $B_s\to (\eta ,{\eta }^{\prime })\nu \overline{\nu }$, and $B_s\to \varphi \nu \overline{\nu }$ decay observables in several 1D and 2D new physics scenarios.

Large fermionic multiplets appear in different extensions of the Standard Model (SM), which are essential to predict small neutrino masses, relic abundance of the dark matter, and the measured value of muon anomalous magnetic moment [muon ($g-2$)]. Models containing a quintuplet of fermions ($\mathrm{\Sigma }$), along with other scalar multiplets, can address recent anomalies in the flavor sector while satisfying the constraints from the electroweak physics. In standard scenarios, the exotic fermions couple with the SM particles directly and there exists a strong limit on their masses from collider experiments such as the Large Hadron Collider (LHC). In this paper, we choose a particular scenario where the quintuplet fermions are heavier than the scalars, which is naturally motivated from the muon ($g-2$) data. A unique nature of these models is that they predict nonstandard signatures at the colliders as the quintuplet fermions decay via the scalars once produced at the colliders. We study these nonstandard interactions and provide alternative search strategies for these exotic fermions at the LHC and future linear colliders (such as $e^{+}{e}^{-}$ colliders). We also discuss their exclusion and discovery limits. For the doubly charged quintuplet fermion (${\mathrm{\Sigma }}^{\pm \pm }$), discovery is possible with $5\sigma$ significance at integrated luminosity of $3000{\mathrm{fb}}^{-1}$ at the 14 TeV LHC if $M_{\mathrm{\Sigma }}\le 980\mathrm{GeV}$. For the singly charged quintuplet fermion (${\mathrm{\Sigma }}^{\pm }$), the discovery is challenging at the LHC but there might be a possibility of $5\sigma$ discovery with $1000{\mathrm{fb}}^{-1}$ luminosity at $e^{+}{e}^{-}$ collider for $M_{\mathrm{\Sigma }}\le 700\mathrm{GeV}$.

Based on $(10087\pm 44)\times {10}^{6}J/\psi$ events collected with the BESIII detector at BEPCII, the double Dalitz decay ${\eta }^{\prime }\to e^{+}{e}^{-}{e}^{+}{e}^{-}$ is observed for the first time via the $J/\psi \to \gamma {\eta }^{\prime }$ decay process. The significance is found to be $5.7\sigma$ with systematic uncertainties taken into consideration. Its branching fraction is determined to be $\mathcal{B}({\eta }^{\prime }\to e^{+}{e}^{-}{e}^{+}{e}^{-})=(4.5\pm 1.0(\mathrm{stat})\pm 0.5(\mathrm{sys}))\times {10}^{-6}$.

Recent experiments searching for $\mathrm{sub}\text{−}\mathrm{GeV}/c^2$ dark matter have observed event excesses close to their respective energy thresholds. Although specific to the individual technologies, the measured excess event rates have been consistently reported at or below event energies of a few-hundred eV, or with charges of a few electron-hole pairs. In the present work, we operated a 1-g silicon SuperCDMS-HVeV detector at three voltages across the crystal (0, 60 and 100 V). The 0 V data show an excess of events in the tens of eV region. Despite this event excess, we demonstrate the ability to set a competitive exclusion limit on the spin-independent dark matter–nucleon elastic scattering cross section for dark matter masses of $\mathcal{O}(100)\mathrm{MeV}/c^2$, enabled by operation of the detector at 0 V potential and achievement of a very low $\mathcal{O}(10)\mathrm{eV}$ threshold for nuclear recoils. Comparing the data acquired at 0, 60 and 100 V potentials across the crystal, we investigated possible sources of the unexpected events observed at low energy. The data indicate that the dominant contribution to the excess is consistent with a hypothesized luminescence from the printed circuit boards used in the detector holder.

Schwarzschild-de Sitter (SdS) black holes do not admit a completely smooth Euclidean continuation. We discuss some modifications of the gravitational path integral that give Euclidean SdS a semiclassical equilibrium interpretation. First we consider “gravity in a cavity,” defining the canonical ensemble in a box that excises one horizon. However, this standard approach does not work for positive cosmological constant: the solution of lowest free energy has a negative heat capacity, which is inconsistent if it is to provide the leading semiclassical contribution to a canonical partition function. Instead we modify the boundary conditions in the path integral to construct the microcanonical partition function, which appears to be well-defined. We then bring two ensembles into contact and remove the boundary, producing states of a larger microcanonical ensemble that contain, for example, both a black hole and a cosmological horizon at once. These systems are closed and have no boundary, but they must possess some form of mild metric discontinuity. We discuss the case where the discontinuity is equivalent to the insertion of a thin, rigid membrane, separating two systems that can exchange energy and are at local equilibrium. Equilibrium configurations obtained in this way are found to be thermodynamically unstable if they contain a black hole.

In this work, we investigate, for the first time, the melting of charmonium states within a holographic QCD model in the context of Einstein-Maxwell-dilaton theory. In the dual field theory, the model describes the heavy mesons inside a finite temperature and density medium. First, we calculate the spectrum at zero temperature. Then, at finite temperature, we obtain the spectral functions, where the heavy vector meson are represented by peaks. We show that the charmonium melts down at temperatures above the confinement/deconfinement temperature of the quark-gluon plasma. We also observe that the chemical potential speeds up the melting process. In the gravitational side of the theory, we solve the perturbation equations in the hydrodynamic limit. From this result, we read off the diffusion coefficient, then the quark number susceptibility. We show that the quark number susceptibility computed in this way does not blow up at the critical end point. We interpret this result as the lack of backreaction on the background by the action describing the vector mesons. To get the quasinormal frequencies, we solve the perturbation equations numerically. We report the emergence of a new mode whose real part increases rapidly at a certain value of the chemical potential, while its imaginary part decreases with the increasing of the chemical potential. Finally, by comparing against results obtained in the conformal plasma, we observe that the real part of the frequency increases, while the imaginary part decreases when we consider the nonconformal plasma.

We study the perturbation due to rotating shockwaves in Banados-Teitelboim-Zanelli geometries at late times and analyze the change in mutual information between the two subsystems belonging to the dual ${\mathrm{CFT}}_L$ and ${\mathrm{CFT}}_R$. We find that the scrambling of mutual information is in general governed by the Lyapunov index ${\lambda }_L$ which is bounded by $\kappa =\frac{2\pi }{\beta (1-\mu \mathcal{L})}\ge \frac{2\pi }{\beta }$, where $\mu =r_{-}/r_{+}$ and $\mathcal{L}$ is the angular momentum of the shockwave. For the special case of $\mathcal{L}=1$ we find the mutual information analytically and show that it is characterized by ${\lambda }_L=\kappa /2$ with the scrambling time for large black holes given as $t_{*}=\frac{\beta (1-\mu )}{\pi }\log S$.