Fluctuations play a critical role in cosmology. They are relevant across a range of phenomena from the dynamics of inflation to the formation of structure. In many cases, these fluctuations are coarse grained and follow a Gaussian distribution as a consequence of the central limit theorem. Yet, some classes of observables are dominated by rare fluctuations and are sensitive to the details of the underlying microphysics. In this paper, we argue that the large deviation principle can be used to diagnose when one must appeal to the fundamental description. Concretely, we investigate the regime of validity for the Fokker-Planck equation that governs stochastic inflation. For typical fluctuations, this framework leads to the central limit-type behavior expected of a random walk. However, fluctuations in the regime of the large deviation principle are determined by instantonlike saddle points accompanied by a new energy scale. When this energy scale is above the UV cutoff of the effective field theory, the tail is only calculable in the microscopic description. We explicitly demonstrate this phenomenon in the context of determining the phase transition to eternal inflation, the distribution of scalar field fluctuations in de Sitter, and the production of primordial black holes.

The origin of the bulk of the TeV–PeV astrophysical neutrinos seen by the IceCube neutrino telescope is unknown. If they are made in photohadronic, i.e., proton-photon, interactions in astrophysical sources, this may manifest as a bumplike feature in their diffuse flux, centered around a characteristic energy. We search for evidence of this feature, allowing for variety in its size and shape, in 7.5 years of High-Energy Starting Events (HESE) collected by IceCube, and make forecasts using larger data samples expected from upcoming neutrino telescopes. Present-day data reveals no evidence of bumplike features, which allows us to constrain candidate populations of photohadronic neutrino sources. Near-future forecasts show promising potential for stringent constraints or decisive discovery of bumplike features. Our results provide new insight into the origins of high-energy astrophysical neutrinos, complementing those from point-source searches.

Future ground-based gravitational wave observatories will be ideal probes of the environments surrounding black holes with masses $1-10M_{\odot }$. Binary black hole mergers with mass ratios of order $q=m_2/m_1\lesssim {10}^{-3}$ can remain in the frequency band of such detectors for months or years, enabling precision searches for modifications of their gravitational waveforms with respect to vacuum inspirals. As a concrete example of an environmental effect, we consider here a population of binary primordial black holes which are expected to be embedded in dense cold dark matter spikes. We provide a viable formation scenario for these systems compatible with all observational constraints and predict upper and lower limits on the merger rates of small-mass-ratio pairs. Given a detected signal of one such system by either Einstein Telescope or Cosmic Explorer, we show that the properties of the binary and of the dark matter spike can be measured to excellent precision with one week’s worth of data, if the effect of the dark matter spike on the waveform is taken into account. However, we show that there is a risk of biased parameter inference or missing the events entirely if the effect of the predicted dark matter overdensity around these objects is not properly accounted for.

In extensive air showers induced by ultrahigh energy (UHE) cosmic rays, secondary particles are produced with energies far above those accessible by other means. These extreme energies can be used to search for new physics. We study the effects of isotropic, nonbirefringent Lorentz violation in the photon sector. In case of a photon velocity smaller than the maximum attainable velocity of standard Dirac fermions, vacuum Cherenkov radiation becomes possible. Implementing this Lorentz-violating effect in air-shower simulations, a significant reduction of the calculated average atmospheric depth of the shower maximum $⟨X_{\max }⟩$ is obtained. Based on $⟨X_{\max }⟩$ and its shower-to-shower fluctuations $\sigma (X_{\max })$, a new bound on Lorentz violation is derived which improves the previous one by a factor of 2. This is the first such bound based on the absence of vacuum Cherenkov radiation from fundamental particles (electrons and positrons) in air showers. Options for further improvements are discussed.

Using the external-field method, i.e., evaluating the effective action $V_{\mathrm{eff}}$ for an arbitrarily strong constant and homogeneous field, we explore nonperturbative properties of QED allowing arbitrary gyromagnetic ratio $g$. We find a cusp at $g=2$ in (a) The QED $b_0$-renormalization group coefficient, and in the infinite-wavelength limit in (b) a subclass containing the pseudoscalar ${\mathcal{P}}^{2n}=(\overrightarrow{E}·\overrightarrow{B}{)}^{2n}$ of light-light scattering coefficients. Properties of $b_0$ imply for certain domains of $g$ asymptotic freedom in an Abelian theory.

In this paper, we evaluate the energy loss rate of supernovae induced by the axion emission process ${\pi }^{-}+p\to n+a$ with the $\mathrm{\Delta }(1232)$ resonance in the heavy baryon chiral perturbation theory for the first time. Given the axion-nucleon-$\mathrm{\Delta }$ interactions, we include the previously ignored $\mathrm{\Delta }$-mediated graphs to the ${\pi }^{-}+p\to n+a$ process. In particular, the ${\mathrm{\Delta }}^0$-mediated diagram can give a resonance contribution to the supernova axion emission rate when the center-of-mass energy of the pion and proton approaches the $\mathrm{\Delta }(1232)$ mass. With these new contributions, we find that for the typical supernova temperatures, compared with the earlier work with the axion-nucleon (and axion-pion-nucleon contact) interactions, the supernova axion emissivity can be enhanced by a factor of $\sim 4(2)$ in the Kim-Shifman-Vainshtein-Zakharov model and up to a factor of $\sim 5(2)$ in the Dine-Fischler-Srednicki-Zhitnitsky model with small $\tan \beta$ values. Remarkably, we notice that the $\mathrm{\Delta }(1232)$ resonance gives a destructive contribution to the supernova axion emission rate at high supernova temperatures, which is a nontrivial result in this study.

We study the partial decay widths of charmonium (bottomonium) states to $\mathrm{D}\overline{\mathrm{D}}(\mathrm{B}\overline{\mathrm{B}})$ mesons in magnetized (nuclear) matter using a field theoretical model of composite hadrons with quark (and antiquark) constituents. These are computed from the mass modifications of the decaying and produced mesons within a chiral effective model, including the nucleon Dirac sea effects. The mass modifications of the open charm (bottom) mesons are calculated from their interactions with the nucleons and the scalar mesons, whereas the mass shift of the heavy quarkonium state is obtained from the medium change of a scalar dilaton field, $\chi$, which mimics the gluon condensates of QCD. The Dirac sea contributions are observed to lead to a rise (drop) in the quark condensates as the magnetic field is increased; an effect called the (inverse) magnetic catalysis. These effects are observed to be significant, and the anomalous magnetic moments (AMMs) of the nucleons are observed to play an important role. For ${\rho }_B=0$, there is observed to be magnetic catalysis (MC) without and with AMMs, whereas, for ${\rho }_B={\rho }_0$, the inverse magnetic catalysis is observed when the AMMs are taken into account, contrary to MC, when the AMMs are ignored. In the presence of a magnetic field, there are also mixings of spin 0 (pseudoscalar) and spin 1 (vector) states (PV mixing), which modify the masses of these mesons. The magnetic field effects on the heavy quarkonium decay widths should have observable consequences on the production the heavy flavor mesons, which are created in the early stage of ultrarelativistic peripheral heavy ion collisions, at RHIC and LHC, when the produced magnetic fields can still be extremely large.

We study the $\rho$ and $\omega$ meson contribution to the radiative decays $X(3872)\to J/\psi \pi \gamma$ and $X(3872)\to J/\psi \pi \pi \gamma$. The $X(3872)\to J/\psi \pi \gamma$ is dominated by the $\omega$ meson. As for the $X(3872)\to J/\psi \pi \pi \gamma$, the contributions of the cascade decays through the $\rho$ and $\omega$ mesons are strongly suppressed with respect to the diagrams which proceed either through the $\psi (2S)$ or the three body decay of $\rho$. The branching ratios of $X(3872)\to J/\psi \pi \gamma$ and $X(3872)\to J/\psi \pi \pi \gamma$ are $({8.10}_{-2.88}^{+3.50})\times {10}^{-3}$ and $(2.38\pm 1.06)\%$, which may be accessible by the BESIII and LHCb collaborations. Especially, the $X(3872)\to J/\psi \pi \gamma$ and $X(3872)\to J/\psi {\pi }^{+}{\pi }^{-}\gamma$ decays can be employed to extract the couplings $g_{X\psi \omega }$ and $g_{X\psi \rho }$, which probe the isoscalar and isovector components of the $X(3872)$ wave function, respectively.

We study the processes $e^{+}{e}^{-}\to K^{+}{K}^{-}{\pi }^0{\pi }^0{\pi }^0\gamma$, $K_S^0{K}^{\pm }{\pi }^{\mp }{\pi }^0{\pi }^0\gamma$, and $K_S^0{K}^{\pm }{\pi }^{\mp }{\pi }^{+}{\pi }^{-}\gamma$ in which an energetic photon is radiated from the initial state. The data were collected with the BABAR detector at the SLAC National Accelerator Laboratory. About 1200, 2600, and 6000 events, respectively, are selected from a data sample corresponding to an integrated luminosity of $469{\mathrm{fb}}^{-1}$. The invariant mass of the hadronic final state defines the effective $e^{+}{e}^{-}$ center-of-mass energy. The center-of-mass energies range from threshold to 4.5 GeV. From the mass spectra, the first ever measurements of the $e^{+}{e}^{-}\to K^{+}{K}^{-}{\pi }^0{\pi }^0{\pi }^0$, $e^{+}{e}^{-}\to K_S^0{K}^{\pm }{\pi }^{\mp }{\pi }^0{\pi }^0$, and $e^{+}{e}^{-}\to K_S^0{K}^{\pm }{\pi }^{\mp }{\pi }^{+}{\pi }^{-}$ cross sections are performed. The contributions from the intermediate states that include $\eta$, $\varphi$, $\rho$, $K^{*}(892)$, and other resonances are presented. We observe the $J/\psi$ and $\psi (2S)$ in most of these final states and measure the corresponding branching fractions, many of them for the first time.

The real-time dynamics of chiral phase transition is investigated in a two-flavor ($N_f=2$) soft-wall anti–de Sitter/QCD model. To understand the dynamics of thermalization, we quench the system from initial states deviating from the equilibrium states. Then, we solve the nonequilibrium evolution of the order parameter (chiral condensate $⟨\sigma \equiv \overline{q}q⟩$). It is shown that the system undergoes an exponential relaxation at temperatures away from the critical temperature $T_c$. The relaxation time diverges at $T_c$, presenting a typical behavior of critical slowing-down. Numerically, we extract the dynamic critical exponent $z$ and get $z\approx 2$ by fitting the scaling behavior $\sigma \propto t^{-\beta /(\nu z)}$, where the mean-field static critical exponents (order parameter critical exponent $\beta =1/2$, correlation length critical exponent $\nu =1/2$) have been applied. More interestingly, it is remarked that, for a large class of initial states, the system would linger over a quasi-steady-state for a certain period of time before the thermalization. It is suggested that the interesting phenomenon, known as prethermalization, has been observed in the framework of holographic models. In such prethermal stage, we verify that the system is characterized by a universal dynamical scaling law and described by the initial-slip exponent $\theta =0$.

We investigate the transition of a two-level atom as the Unruh-Dewitt detector accelerated in the electromagnetic field in this paper. The enhancement of the transition probability is found for different field states under the conditions that the anti-Unruh effect appears. In particular, the enhancement is the most prominent when the field state takes the squeezed state. We also construct a new atomic trajectory to realize the effect of acceleration-induced transparency. Based on this, we show that the anti-Unruh effect still exists even at the specific atomic energy difference where acceleration-induced transparency happens.

In this work we continue with our recent study, using the Feynman-Vernon worldline influence action and the Schwinger-Keldysh closed-time-path formalism, to consider the effects of quantum noise of gravitons on the motion of point masses. This effect can be regarded as due to a stochastic tensorial force whose correlator is given by the graviton noise kernel associated with the Hadamard function of the quantized gravitational field. Solving the Langevin equation governing the motion of the separation of two masses, the fluctuations of the separation due to the graviton noise can be obtained for various states of the quantum field. Since this force has the stretching and compressing effects like the tidal force, we can view it as one. We therefore derive the expressions for, and estimate the magnitude of, this tidal force for the cases of the Minkowski and the squeezed vacua. The influence of this force on the evolution of the geodesic congruence through the Raychaudhuri equation is then studied and the effects of quantum graviton noise on the shear and rotation tensors presented.

We start by presenting the general set of structure equations for the $1+3$ threading spacetime decomposition in four spacetime dimensions, valid for any theory of gravitation based on a metric compatible affine connection. We then apply these equations to the study of cosmological solutions of the Einstein-Cartan theory in which the matter is modeled by a perfect fluid with intrinsic spin. It is shown that the metric tensor can be described by a generic Friedman-Lemaître-Robertson-Walker solution. However, due to the presence of torsion the Weyl tensors might not vanish. The coupling between the torsion and Weyl tensors leads to the conclusion that, in this cosmological model, the universe must either be flat or open, excluding definitely the possibility of a closed universe. In the open case, we derive a wave equation for the traceless part of the magnetic part of the Weyl tensor and show how the intrinsic spin of matter in a dynamic universe leads to the generation and emission of gravitational waves. Last, in this cosmological model, it is found that the torsion tensor, which has an intrinsic spin as its source, contributes to a positive accelerated expansion of the universe. Comparing the theoretical predictions of the model with the current experimental data, we conclude that torsion cannot completely replace the role of a cosmological constant.

We investigate the bound orbits of massive/massless, neutral particles and photons moving around regular black holes of Fan and Wang. For massive particles, we show the existence of stable/unstable circular orbits and the charge dependence of the radius of the innermost stable circular orbit. Remarkably, we find an unstable circular orbit of photons inside the event horizon. For massless particles and photons, we show that both stable and unstable circular orbits can exist in a regular and horizonless spacetime with a slight overcharge. Then, we also discuss the periapsis shift of massive neutral particles orbiting around the black hole, and show that the charge gives a negative correction to the shift for black holes with small nonlinearity of electrodynamics.

In this paper, we extend our previous work [D. Wu, Phys. Rev. D 107, 024024 (2023)] to the more general cases with a negative cosmological constant, and investigate the topological numbers for the singly rotating Kerr-AdS black holes in all dimensions and the four-dimensional Kerr-Newman-AdS black hole as well as the three-dimensional Bañados-Teitelboim-Zanelli black hole. We find that the topological numbers of black holes are remarkably influenced by the cosmological constant. In addition, we also demonstrate that the dimension of spacetimes has an important effect on the topological number for rotating anti–de Sitter (AdS) black holes. Furthermore, it is interesting to observe that the difference between the topological number of the AdS black hole and that of its corresponding asymptotically flat black hole is always unity. This new observation leads us to conjure that it might be valid also for other black holes. Of course, this novel conjecture needs to be further verified by examining the topological numbers of many other black holes and their AdS counterparts in the future work.

We study the linear stability of nonrelativistic $\ell$-boson stars, describing static, spherically symmetric configurations of the Schrödinger-Poisson system with multiple wave functions having the same value of the angular momentum $\ell$. In this work we restrict our analysis to time-dependent perturbations of the radial profiles of the $2\ell +1$ wave functions, keeping their angular dependency fixed. Based on a combination of analytic and numerical methods, we find that for each $\ell$, the ground state is linearly stable, whereas the $n$th excited states possess $2n$ unstable (exponentially in time growing) modes. Our results also indicate that all excited states correspond to saddle points of the conserved energy functional of the theory.

Intermediate mass ratio inspirals (IMRIs) will be observable with space-based gravitational wave detectors such as the Llaser interferometer space antenna. To this end, the environmental effects in such systems have to be modeled and understood. These effects can include (baryonic) accretion disks and dark matter (DM) overdensities, so-called spikes. For the first time, we model an IMRI system with both an accretion disk and a DM spike present and compare their effects on the inspiral and the emitted gravitational wave signal. We study the eccentricity evolution, employ the braking index and derive the dephasing index, which turn out to be complementary observational signatures. They allow us to disentangle the accretion disk and DM spike effects in the IMRI system and can be utilized to study environmental effects in general.

We estimate the long-lasting gravitational wave (GW) emission of compact dark objects following a binary neutron-star (NS) merger. We consider compact dark objects, which initially reside in the centers of NSs and which may consist of self-interacting dark matter (DM). By approximating the compact dark objects as test particles, we model the merging of NS binaries hosting DM components with three-dimensional relativistic simulations. Our simulation results suggest that the DM components remain gravitationally bound and orbit inside the merger remnant with orbital separations of typically a few km. The subsequent orbital motion of the DM components generates a GW signal with frequencies in the range of a few kHz. When considering a range of different binary masses and high-density equations of state (EOS), we find that the GW frequency of the orbiting DM components scales with the compactness of NSs. Similarly, we find relations between the DM GW frequency and the dominant postmerger GW frequency of the stellar fluid or the tidal deformability, which quantifies EOS effects during the binary inspiral. Hence, a measurement of these quantities can be used to specify the frequency range of the GW emission by DM. Under the assumption that GW back reaction is the only relevant dissipative process, the GW signal may last between seconds and years depending on the mass of the DM component. We estimate the detectibility of the GW signals and find that DM components in NS mergers may only be detectable with existing and projected GW instruments if the dark objects are as massive as about 0.01 to $0.1M_{\odot }$. We emphasize that the GW emission is limited by the lifetime of the remnant. A forming black hole will immediately swallow the DM objects because their orbits are smaller than the innermost stable circular orbit of the black hole.

There are still some significant and unanswered questions about the incredible very-high-energy $\gamma$-ray signatures. To help understand the mechanism, focusing on the linear and quadratic perturbation mode for the subluminal regime, we revisit the expected signature for the Lorentz invariance violation (LIV) effects on $\gamma \text{−}\gamma$ absorption in the TeV spectra of gamma-ray bursts (GRBs). We note that there is a critical energy for the pair production process, which is sensitive to the assumed quantum gravity energy scale. We suggest that a reemergence of the energy spectrum of $\gamma$ rays at several tens of TeV is a rough observational diagnostic for the LIV effects. The expected spectra characteristics are applied to GRB 221009A. The results show that the cosmic opacity with LIV effects considered here can roughly reproduce the observed $\gamma$-ray spectra for the source, which enables us to constrain the upper limit of the values of the energy scale to $E_{\mathrm{QG},1}\le 3.35\times {10}^{20}\mathrm{GeV}$ for the linear perturbation and $E_{\mathrm{QG},2}\le 9.19\times {10}^{12}\mathrm{GeV}$ for the quadratic perturbation. These scenarios lead to updated bounds on the LIV coefficient, with ${\xi }_1^{\prime }\ge 3.62\times {10}^{-2}$ for the linear perturbation and ${\xi }_2^{\prime }\ge 1.33\times {10}^6$ for the quadratic perturbation, in the standard model extension framework.

The $T_{cc}^{+}$ exotic meson, discovered by the LHCb Collaboration in 2021, can be interpreted as a molecular state of $D^{(*)0}$ and $D^{(*)+}$ mesons. We compute next-to-leading-order (NLO) contributions to the strong decay of $T_{cc}^{+}$ in an effective field theory for $D$ mesons and pions, considering contributions from one-pion exchange and final-state rescattering. Corrections to the total width, as well as the differential distribution in the invariant mass of the final-state $D$-meson pair are computed. The results remain in good agreement with LHCb experimental results when the NLO contributions are added. The leading uncertainties in the calculation come from terms which depend on the scattering length and effective range in $D$-meson scattering.