We present the first nonlinear lattice simulation of an axion field coupled to a U(1) gauge field during inflation. We use it to fully characterize the statistics of the primordial curvature perturbation $\zeta$. We find high-order statistics to be essential in describing non-Gaussianity of $\zeta$ in the linear regime of the theory. On the contrary, non-Gaussianity is suppressed when the dynamics become nonlinear. This relaxes the bounds from overproduction of primordial black holes, allowing for an observable gravitational waves signal at pulsar timing array and interferometer scales. Our work establishes lattice simulations as a crucial tool to study the inflationary epoch and its predictions.

We investigate the connection between the full- and flat-sky angular power spectra. First, we revisit this connection established on the geometric and physical grounds, namely, that the angular correlations on the sphere and in the plane (flat-sky approximation) correspond to each other in the limiting case of small angles and a distant observer. To establish the formal conditions for this limit, we first resort to a simplified shape of the 3D power spectrum, which allows us to obtain analytic results for both the full- and flat-sky angular power spectra. Using a saddle point approximation, we find that the flat-sky results are obtained in the limit when the comoving distance and wave modes $\ell$ approach infinity at the same rate. This allows us to obtain an analogous asymptotic expansion of the full-sky angular power spectrum for general 3D power spectrum shapes, including the $\mathrm{\Lambda }$ cold dark matter universe. In this way, we find a robust limit of correspondence between the full- and flat-sky results. These results also establish a mathematical relation, i.e., an asymptotic expansion of the ordinary hypergeometric function of a particular choice of arguments that physically corresponds to the flat-sky approximation of a distant observer. This asymptotic form of the ordinary hypergeometric function is obtained in two ways: relying on our saddle point approximation and using some of the known properties of the hypergeometric function.

Starting from May 2023, the LIGO Scientific, Virgo and KAGRA Collaboration has been conducting the fourth observing run with improved detector sensitivities and an expanded detector network including KAGRA. Accordingly, it is vital to optimize the detection algorithm of low-latency search pipelines, increasing their sensitivities to gravitational waves from compact binary coalescences. In this work, we discuss several new features developed for ranking statistics of GstLAL-based inspiral pipeline, which mainly consist of the signal contamination removal, the bank-${\xi }^2$ incorporation, the upgraded $\rho -{\xi }^2$ signal model, and the integration of KAGRA. An injection study demonstrates that these new features improve the pipeline’s sensitivity by approximately 15% to 20%, paving the way to further multimessenger observations during the upcoming observing run.

Previous theoretical works using the premerger orbital evolution of coalescing neutron stars to constrain properties of dense nuclear matter assume a gravitational wave phase uncertainty of a few radians, or about a half cycle. However, recent studies of the signal from GW170817 and next-generation detector sensitivities indicate actual phase uncertainties at least twenty times better. Using these refined estimates, we show that future observations of nearby sources like GW170817 may be able to reveal neutron star properties beyond just radius and tidal deformability, such as the matter composition and/or presence of a superfluid inside neutron stars, via tidal excitation of g-mode oscillations. Data from GW170817 already limits the amount of orbital energy that is transferred to the neutron star to $<2\times {10}^{47}\mathrm{erg}$ and the g-mode tidal coupling to $Q_{\alpha }<{10}^{-3}$ at 50 Hz ($5\times {10}^{48}\mathrm{erg}$ and $4\times {10}^{-3}$ at 200 Hz), and future observations and detectors will greatly improve upon these constraints. In addition, analysis using general parametrization models that have been applied to the so-called p-g instability show that the instability already appears to be restricted to regimes where the mechanism is likely to be inconsequential; in particular, we show that the number of unstable modes is $\ll 100$ at $\lesssim 100\mathrm{Hz}$, and next generation detectors will essentially rule out this mechanism (assuming that the instability remains undetected). Finally, we illustrate that measurements of tidal excitation of r-mode oscillations in nearby rapidly rotating neutron stars are within reach of current detectors and note that even nondetections will limit the inferred inspiralling neutron star spin rate to $<20\mathrm{Hz}$, which will be useful when determining other parameters such as neutron star mass and tidal deformability.

The existence of quark matter inside the heaviest neutron stars has been the topic of numerous recent studies, many of them suggesting that a phase transition to strongly interacting conformal matter inside neutron stars is feasible. Here we examine this hybrid star scenario using a soft and a stiff hadronic model, a constituent quark model with three quark flavors, and applying a smooth crossover transition between the two. Within a Bayesian framework, we study the effect of up-to-date constraints from neutron star observations on the equation-of-state (EOS) parameters and various neutron star observables. Our results show that a pure quark core is only possible if the maximum mass of neutron stars is below $\sim 2.35M_{\odot }$. However, we also find, consistent with other studies, that a peak in the speed of sound, exceeding $1/3$, is highly favored by astrophysical measurements, which might indicate the percolation of hadrons at $\sim 3–4n_0$. Even though our prediction for the phase transition parameters varies depending on the specific astrophysical constraints utilized, the position of the speed of sound peak only changes slightly, while the existence of pure quark matter below $\sim 4n_0$, using our parametrization, is disfavored. On the other hand, the preferred range for the EOS shows signs of conformality above $\sim 4n_0$. Additionally, we present the difference in the upper bounds of radius estimates using the full probability density data and sharp cutoffs and stress the necessity of using the former.

This study searches for neutrino signals from 18 dwarf spheroidal galaxies (dSphs) using 10 years of publicly available muon-track data of the IceCube neutrino observatory. We apply an unbinned likelihood analysis on each of these dSphs to derive the significance the putative neutrino emission. To further enhance our sensitivity, we also stack all dSphs together to perform a joint analysis. However, no significant neutrino emission signal was detected in either the single-source or stacking analysis. Based on these null results, we derive constraints on the annihilation cross section of dark matter particles. Compared to the existing literature, our constraints via the channel $\chi \chi \to {\mu }^{+}{\mu }^{-}$ are comparable to the ones from the VERITAS observations of dSphs.

The spaceborne gravitational wave detection mission has a demanding requirement for the precision of displacement sensing, which is conducted by the interaction between the laser field and test mass. However, due to the roughness of the reflecting surface of the test mass, the displacement measurement along the sensitive axis suffers a coupling error caused by the residue motion of other degrees of freedom. In this article, we modeled the coupling of the test mass residue random motion to the displacement sensing along the sensitive axis and derived an analytical formula of the required precision of the surface error for the spaceborne gravitational wave detectors. Our result shows that for the test masses in the LISA pathfinder, this coupling error will not contaminate the picometer displacement sensing.

Neutrino-antineutrino ($\nu \overline{\nu }$) pair production is one of the main processes responsible for the energy loss of stars. Apart from the collision of two ($\gamma \gamma \to \nu \overline{\nu }$) or three ($\gamma \gamma \gamma \to \nu \overline{\nu }$) real photons, pair creation from a photon and photon collisions in the presence of nuclear Coulomb fields or external magnetic fields have been considered previously. Here, we study pair production of a neutrino and antineutrino from a low-energy photon in the presence of a combined homogeneous magnetic field and the Coulomb field of a nucleus with charge number $Z$.

Many new physics scenarios beyond the Standard Model (BSM) necessitate the existence of new neutral and/or charged scalar fields, which might couple to the SM charged leptons (but not hadrons) and, thus, can give rise to BSM signals while evading strong constraints mostly coming from the hadronic sector. I show that future lepton colliders provide a clean environment to probe these leptophilic new scalars via multilepton final states, including some interesting lepton flavor violating channels. I also study the kinematic distributions of the final state leptons to distinguish the BSM contributions from neutral and doubly charged scalars giving rise to the same final state, as well as from the irreducible SM background.

According to the conservation of angular momentum, when a plane-wave polarized photon splits into a pair of electron-positron under the influence of the Coulomb field, the spin angular momentum (SAM) of the photon is converted into the angular momentum of the leptons. We investigate this process (the Bethe-Heitler process) by describing the final electron and positron with twisted states and find that the SAM of the incident photon is not only converted into SAM of the produced pair, but also into their orbital angular momentum (OAM), which has not been considered previously. The average OAM gained by the leptons surpasses the average SAM, while their orientations coincide. Both properties depend on the energy and open angle of the emitted leptons. The demonstrated spin-orbit transfer shown in the Bethe-Heitler process may exist in a large group of QED scattering processes.

Inspired by the recent anomalies on the lepton flavor universalities, we present an investigation of baryonic form factors induced by heavy-to-light tensor currents. With the light-front quark model, we calculate the tensor form factors, and the momentum distributions are accessed with two parametrization forms. Numerical results for the form factors at $q^2=0$ are derived and parameters in $q^2$ distributions are obtained through extrapolation. Our results are helpful for the analysis of new physics contributions in the heavy-to-light transition.

The charged Higgs boson plays an essential role in distinguishing between a wide variety of standard model extensions with multiple Higgs doublets, and has been searched for in various collider experiments. This paper expands our previous work to a broader Higgs mass space with discussions on subsequent issues. We study the prospect of a light charged Higgs boson, produced by top quark pairs at the Large Hadron Collider (LHC), and decaying into a $W$ boson (can be off shell) and a pair of bottom quarks via on-shell production of an intermediate neutral Higgs boson. We reinterpret the cross sections of $WWbb\overline{b}\overline{b}$ final states measured by the ATLAS Collaboration at LHC 13 TeV in the presence of the decay chain $t\to H^{+}b,H^{+}\to W^{+}{H}_i,H_i\to b\overline{b}$, and H.c., where $H_i$ is a neutral Higgs boson variably lighter than the charged Higgs boson. We find improved agreements with the data and obtain limits on the total branching ratio of the aforementioned decay chain. The limits impose the strongest constraints on the parameter space of type-I two-Higgs-doublet model for most Higgs masses sampled when $H_i$ is the $CP$-odd Higgs boson $A$. We also calculate potential constraints with pseudodata in high-luminosity runs of the LHC.

We investigate the global properties of hybrid stars and quark-matter cores by using a quasiparticle model that rules out the possibility of the existence of absolutely stable strange quark matter within the hybrid stars. Results from our study indicate that the coupling constant $g$ can stiffen the equation of state of hybrid star matter and thus increase the hybrid star maximum mass and its tidal deformability, whereas it also decreases the mass and radius of the pure quark. By breaking the absolutely stable condition, we provide the maximum mass, minimum radius $R_{1.4}$, and minimum tidal deformation ${\mathrm{\Lambda }}_{1.4}$ of the hybrid stars as well as the maximum mass and radius of the quark-matter core with different $g$ values within the allowable regions (the energy per nucleon of both $u$-$d$ quark matter and strange quark matter must exceed 930 MeV) on the $g\text{−}{B}^{1/4}$ plane. In addition, we find that a step change of the sound velocity occurs in the hadron-quark mixed phase, and the approximate rule that the polytropic index $\gamma \le 1.75$ can also be used as a criterion for separating hadronic from quark matter in our work. Our results also confirm that the sizable quark-matter cores ($R_{QC}>6.5\mathrm{km}$) containing the mixed phase can appear in $2M_{\odot }$ massive stars.

There has been growing interest in the near-threshold production of heavy quarkonium which can access the gluonic structure in the nucleon. Previously [ , Phys. Rev. D 103, 096010 (2021)], we studied this process with QCD and showed that it can be factorized with the gluon generalized parton distributions in the heavy quark limit. We further argued that the hadronic matrix element is dominated by its leading moments corresponding to the gluonic gravitational form factors (GFFs) in this limit. Since then, there have been many new developments on this subject. More experimental measurements have been made and published, and the lattice simulation of gluonic GFFs has been improved as well. In this work, we make an important revision to a previous result and perform an updated analysis with the new inputs. We also study the importance of the large momentum transfer to extract these gluonic structures reliably in this framework.

We investigate entanglement of local spatial modes defined by a quantum field in a de Sitter universe. The introduced modes show disentanglement behavior when the separation between two regions where local modes are assigned becomes larger than the cosmological horizon. To understand the emergence of separability between these local modes, we apply the monogamy inequality proposed by S. Camalet. We embed the focusing bipartite mode defined by the quantum field in a pure four-mode Gaussian state, and identify its partner modes. Then applying a Gaussian version of the monogamy relation, we show that the external entanglement between the bipartite mode and its partner modes constrains the entanglement of the bipartite mode. Thus the emergence of separability of local modes in the de Sitter universe can be understood from the perspective of entanglement monogamy.

Within the trace-logarithm formalism for the effective action we investigate the vacuum interaction of cosmic strings and the influence of string’s width on this effect. For the massless real scalar field we compute the Casimir contribution into the total vacuum energy. The dimensional-regularization technique is used. It is shown that the regularized Casimir term contains neither the UV divergences, nor the divergences related with the nonintegrability of the renormalized vacuum mean of the energy-momentum tensor. In the case of two infinitely-thin strings, the limit coincides with the known result. The effect related with the finite width becomes significant on the distances of several core diameters.

A metric that describes a collapsing star and the surrounding black hole geometry accounting for quantum gravity effects has been derived independently by different research groups. There is consensus regarding this metric up until the star reaches its minimum radius, but there is disagreement about what happens past this event. The discrepancy stems from the appearance of a discontinuity in the Hamiltonian evolution of the metric components in Painlevé-Gullstrand coordinates. Here we show that the continuous geometry that describes this phenomenon is represented by a discontinuous metric when written in these coordinates. The discontinuity disappears by changing coordinates. The discontinuity found in the Hamiltonian approach can therefore be interpreted as a coordinate effect. The geometry continues regularly into an expanding white hole phase, without the occurrence of a shock wave caused by a physical discontinuity.

Black holes with dyonic charges in Einstein-Maxwell-dilaton-axion supergravity theory are revisited in the context of black hole shadows. We consider static as well as rotating (namely the dyonic Kerr-Sen) black holes. The matter stress-energy tensor components, sourced by the Maxwell, axion and dilaton fields, satisfy the standard energy conditions. The analytical expressions for the horizon and the shadow radius of the static spacetimes demonstrate their dependence on $P^2+Q^2$ ($P$, $Q$ the magnetic and electric charges, respectively) and the mass parameter $M$. The shadow radius lies in the range $2M<R_{\text{shadow}}<3\sqrt{3}M$ and there is no stable photon orbit outside the horizon. Further, shadows cast by the rotating dyonic Kerr-Sen black holes are also studied and compared graphically with their Kerr-Newman and Kerr-Sen counterparts. Deviation of the shadow boundary is prominent with the variation of the magnetic charge, for the relatively slowly rotating dyonic Kerr-Sen spacetimes. We test any possible presence of a magnetic monopole charge in the backdrop of recent EHT observations for the supermassive black holes ${\mathrm{M}87}^{*}$ and $\mathrm{Sgr}{\mathrm{A}}^{*}$. Deviation from circularity of the shadow boundary ($\mathrm{\Delta }C$) and deviation of the average shadow radius from the Schwarzschild shadow radius (quantified as the fractional deviation parameter $\delta$) are the two observables used here. The observational bound on $\mathrm{\Delta }C$ (available only for ${\mathrm{M}87}^{*}$) is satisfied for all theoretically allowed regions of parameter space and thus cannot constrain the parameters. The observational bound on $\delta$ available for $\mathrm{Sgr}{\mathrm{A}}^{*}$ translates into an upper limit on any possible magnetic monopole charge linked to $\mathrm{Sgr}{\mathrm{A}}^{*}$ and is given as $P\lesssim 0.873M$. Constraints on $P$ obtained from other astrophysical effects are however expected to be far more stringent though rigorous analyses along these lines is lacking in the literature. In addition, future refined imaging (shadow) observations will surely help in improving the bound on $P$ arrived at here.

We constrain the chameleon screening mechanism in galaxy clusters, essentially obtaining limits on the coupling strength $\beta$ and the asymptotic value of the field ${\varphi }_{\infty }$. For this purpose, we utilized a collection of the nine relaxed galaxy clusters within the X-COP compilation in the redshift range of $z\le 0.1$. We implement the formalism assuming a Navarro-Frenk-White mass profile for the dark matter density and study the degeneracy present between the mass $M_{500}$ and the chameleon coupling with a high degree of improvement in the constraints for excluded parameter space. We recast our constrain to an upper limit on the scalaron field in $f(R)$ subclass of models of $|f_{R0}|\le 9.2\times {10}^{-6}$, using all the nine clusters and $|f_{R0}|\le 1.2\times {10}^{-5}$ using only five clusters with Weak lensing priors taken into account, at a 95% confidence level. These bounds are consistent with existing limits in the literature and tighter than the constraints obtained with the same method by previous studies.

We investigate the real-time dynamics of the ($1+1$)-dimensional U(1) gauge theory known as the Schwinger model via variational quantum algorithms. Specifically, we simulate quench dynamics in the presence of an external electric field. First, we use a variational quantum eigensolver to obtain the ground state of the system in the absence of an external field. With this as the initial state, we perform real-time evolution under an external field via a fixed-depth, parameterized circuit whose parameters are updated using McLachlan’s variational principle. We use the same ansatz for initial-state preparation and time evolution, by which we are able to reduce the overall circuit depth. We test our method with a classical simulator and confirm that the results agree well with exact diagonalization.