We revise the non-Gaussianity of canonical curvaton scenario with a generalized $\delta N$ formalism, in which it can handle the generic potentials. In various curvaton models, the energy density is dominant in different periods including the secondary inflation of curvaton, matter domination, and radiation domination. Our method can unify to deal with these periods since the nonlinearity parameter $f_{\mathrm{NL}}$ associated with non-Gaussianity is a function of equation of state $w$. We first investigate the most simple curvaton scenario, namely, the chaotic curvaton with quadratic potential. Our study shows that most parameter spaces are satisfied with observational constraints. And our formula will nicely recover the well-known value of the $f_{\mathrm{NL}}$ parameter in the absence of nonlinear evolution. From the micro-origin of curvaton, we also investigate the pseudo-Nambu-Goldstone curvaton. Our result clearly indicates that the second short inflationary process for pseudo-Nambu-Goldstone curvaton is ruled out in light of these observations. Finally, our method sheds a new way of investigating the non-Gaussianity of curvaton mechanism, especially for exploring the non-Gaussianity in minimal supersymmetric Standard Model curvaton model.

We present the results of an all-sky search for continuous gravitational wave signals with frequencies in the 1700–2000 Hz range from neutron stars with ellipticity of $\approx {10}^{-8}$. The search employs the Falcon analysis pipeline [V. Dergachev and M. A. Papa, Phys. Rev. Lett. 123, 101101 (2019)] on LIGO O2 public data. Our results improve by a factor greater than 5 over [B. P. Abbott et al. (LIGO Scientific and Virgo Collaborations), Phys. Rev. D 100, 024004 (2019)]. This is a huge leap forward: it takes an entirely new generation of gravitational wave detectors to achieve a 10-fold sensitivity increase over the previous generation [D. Reitze et al., Bull. Am. Astron. Soc. 51, 035 (2019)]. Within the probed frequency range and aside from the detected outliers, we can exclude neutron stars with ellipticity of ${10}^{-8}$ within 65 pc of Earth. We set upper limits on the gravitational wave amplitude that holds even for worst-case signal parameters. New outliers are found, some of which we are unable to associate with any instrumental cause. If any were associated with a rotating neutron star, this would likely be the fastest neutron star today.

We investigate interacting quark matter (IQM), including the perturbative QCD correction and color superconductivity, for both up-down quark matter and strange quark matter. We first derive an equation of state (EOS) unifying all cases by a simple reparametrization and rescaling, through which we manage to maximally reduce the number of degrees of freedom. We find, in contrast to the conventional EOS $p=1/3(\rho -4B_{\mathrm{eff}})$ for noninteracting quark matter, that taking the extreme strongly interacting limit on the unified IQM EOS gives $p=\rho -2B_{\mathrm{eff}}$, where $B_{\mathrm{eff}}$ is the effective bag constant. We employ the unified EOS to explore the properties of pure interacting quark stars (IQSs) composed of IQM. We describe how recent astrophysical observations, such as the pulsar-mass measurements, the NICER analysis, and the binary merger gravitational-wave events GW170817, GW190425, and GW190814, further constrain the parameter space. An upper bound for the maximum allowed mass of IQSs is found to be $M_{\mathrm{TOV}}\lesssim 3.23M_{\odot }$. Our analysis indicates a new possibility that the currently observed compact stars, including the recently reported GW190814’s secondary component ($M=2.59_{-0.09}^{+0.08}{M}_{\odot }$), can be quark stars composed of interacting quark matter.

Since their serendipitous discovery, fast radio bursts (FRBs) have garnered a great deal of attention from both observers and theorists. A new class of radio telescopes with wide fields of view have enabled a rapid accumulation of FRB observations, confirming that FRBs originate from cosmological distances. The high occurrence rate of FRBs and the development of new instruments to observe them create opportunities for FRBs to be utilized for a host of astrophysical and cosmological studies. We focus on the rare, and as yet undetected, subset of FRBs that undergo repeated bursts and are strongly gravitationally lensed by intervening structure. An extremely precise timing of burst arrival times is possible for strongly lensed repeating FRBs, and we show how this timing precision enables the search for long-wavelength gravitational waves, including those sourced by supermassive black hole binary systems. The timing of burst arrival for strongly lensed repeating FRBs is sensitive to gravitational-wave sources near the FRB host galaxy, which may lie at cosmological distances and would therefore be extremely challenging to detect by other means. Timing of strongly lensed FRBs can also be combined with pulsar timing array data to search for correlated time delays characteristic of gravitational waves passing through the Earth.

Sufficient statistics are combinations of data in terms of which the likelihood function can be rewritten without loss of information. Depending on the data volume reduction, the use of sufficient statistics as a preliminary step in a Bayesian analysis can lead to significant increases in efficiency when sampling from posterior distributions of model parameters. Here we show that the frequency integrand of the cross-correlation statistic and its variance are approximate sufficient statistics for ground-based searches for stochastic gravitational-wave backgrounds. The sufficient statistics are approximate because one works in the weak-signal approximation and uses measured estimates of the autocorrelated power in each detector. We perform analytic and numerical calculations to show that, in this approximation, LIGO-Virgo’s hybrid frequentist-Bayesian parameter estimation analysis is equivalent to a fully Bayesian analysis. This work closes a gap in the LIGO-Virgo literature and suggests directions for additional searches.

The global gravitational-wave detector network achieves higher detection rates, better parameter estimates, and more accurate sky localization as the number of detectors $\mathcal{I}$ increases. This paper quantifies network performance as a function of $\mathcal{I}$ for BayesWave, a source-agnostic, wavelet-based, Bayesian algorithm which distinguishes between true astrophysical signals and instrumental glitches. Detection confidence is quantified using the signal-to-glitch Bayes factor ${\mathcal{B}}_{\mathcal{S},\mathcal{G}}$. An analytic scaling is derived for ${\mathcal{B}}_{\mathcal{S},\mathcal{G}}$ versus $\mathcal{I}$, the number of wavelets, and the network signal-to-noise ratio ${\mathrm{SNR}}_{\mathrm{net}}$, which is confirmed empirically via injections into detector noise of the Hanford-Livingston (HL), Hanford-Livingston-Virgo (HLV), and Hanford-Livingston-KAGRA-Virgo (HLKV) networks at projected sensitivities for the fourth observing run (O4). The empirical and analytic scalings are consistent; ${\mathcal{B}}_{\mathcal{S},\mathcal{G}}$ increases with $\mathcal{I}$. The accuracy of waveform reconstruction is quantified using the overlap between injected and recovered waveform, ${\mathcal{O}}_{\mathrm{net}}$. The HLV and HLKV network recovers 87% and 86% of the injected waveforms with ${\mathcal{O}}_{\mathrm{net}}>0.8$, respectively, compared to 81% with the HL network. The accuracy of BayesWave sky localization is $\approx 10$ times better for the HLV network than the HL network, as measured by the search area $\mathcal{A}$, and the sky areas contained within 50% and 90% confidence intervals. Marginal improvement in sky localization is also observed with the addition of the Kamioka Gravitational Wave Detector.

One of the main motivations to look beyond the Standard Model is the discrepancy between the theoretical prediction and observation of the anomalous magnetic moment of the muon. Alleviating this tension between theory and experiment and simultaneously satisfying the bounds from lepton flavor violation data is a challenging task. In this paper, we consider a generalized two-Higgs-doublet model with a Yukawa structure as a perturbation of a type X two-Higgs-doublet model. In view of this model, we explore the muon anomaly and lepton flavor violation along with constraints coming from $B$ physics, theoretical constraints, electroweak observables, and collider data which can restrict the model parameter space significantly. We find that within the framework of this model it is possible to obtain regions allowed by all constraints that can provide an explanation for the observed muon anomaly and at the same time predict interesting signatures of lepton flavor violation. Furthermore, we consider the flavor-violating decay of a low-mass $CP$-odd scalar to probe the allowed parameter space at future runs of the LHC. With a simple cut-based analysis, we show that part of this parameter space can be probed with a significance $>5\sigma$. We also provide an artificial neural network analysis that significantly improves our cut-based results.

Systems with the quantum numbers of up to 12 charged and neutral pseudoscalar mesons, as well as one-, two-, and three-nucleon systems, are studied using dynamical lattice quantum chromodynamics and quantum electrodynamics ($\mathrm{QCD}+\mathrm{QED}$) calculations and effective field theory. QED effects on hadronic interactions are determined by comparing systems of charged and neutral hadrons after tuning the quark masses to remove strong isospin breaking effects. A nonrelativistic effective field theory, which perturbatively includes finite-volume Coulomb effects, is analyzed for systems of multiple charged hadrons and found to accurately reproduce the lattice $\mathrm{QCD}+\mathrm{QED}$ results. QED effects on charged multihadron systems beyond Coulomb photon exchange are determined by comparing the two- and three-body interaction parameters extracted from the lattice $\mathrm{QCD}+\mathrm{QED}$ results for charged and neutral multihadron systems.

The three body pion decays ${\pi }^{+}\to l^{+}\nu X(l=e,\mu )$, where $X$ is a weakly interacting neutral boson, were searched for using the full data set from the PIENU experiment. An improved limit on $\mathrm{\Gamma }({\pi }^{+}\to e^{+}\nu X)/\mathrm{\Gamma }({\pi }^{+}\to {\mu }^{+}{\nu }_{\mu })$ in the mass range $0<m_X<120\mathrm{MeV}/c^2$ and a first result for $\mathrm{\Gamma }({\pi }^{+}\to {\mu }^{+}\nu X)/\mathrm{\Gamma }({\pi }^{+}\to {\mu }^{+}{\nu }_{\mu })$ in the region $0<m_X<33.9\mathrm{MeV}/c^2$ were obtained. The Majoron-neutrino coupling model was also constrained using the current experimental result of the ${\pi }^{+}\to e^{+}{\nu }_e(\gamma )$ branching ratio.

Broad searches for continuous gravitational wave signals rely on hierarchies of follow-up stages for candidates above a given significance threshold. An important step to simplify these follow-ups and reduce the computational cost is to bundle together in a single follow-up nearby candidates. This step is called clustering and we investigate carrying it out with a deep learning network. In our first paper [B. Beheshtipour and M. A. Papa, Phys. Rev. D 101, 064009 (2020)], we implemented a deep learning clustering network capable of correctly identifying clusters due to large signals. In this paper, a network is implemented that can detect clusters due to much fainter signals. These two networks are complementary and we show that a cascade of the two networks achieves an excellent detection efficiency across a wide range of signal strengths, with a false alarm rate comparable/lower than that of methods currently in use.

We examine the tidal deformation of a nonrotating compact body (material body or black hole) in general relativity. The body’s exterior metric is calculated in a simultaneous expansion in powers of the ratio between the distance to the body and three distinct length scales. The first is the radius of curvature of the external spacetime in which the body is inserted, the second is the scale of spatial inhomogeneity of the curvature, and the third is the scale of temporal variation. The metric is valid in the body’s immediate neighborhood, which excludes the external matter responsible for the tidal environment. The body’s tidal response is encapsulated in four types of relativistic Love numbers. The first is $k_{\ell }$, the familiar Love number that measures the linear response to a static tidal field. A second is $p_{\ell }$, which measures the quadratic response to the tidal field. A third is ${\dot{k}}_{\ell }$, which is associated with the first time derivative of the tidal field. And the fourth is ${\ddot{k}}_{\ell }$, associated with the second time derivative of the tidal field. All Love numbers are gauge-invariant constants that appear in the body’s exterior metric. Their computation (not carried out here, except for black holes) requires extending the metric to the body’s interior. The Love numbers acquire an operational meaning through the definition of tidally induced multipole moments. Previously proposed definitions for the moments suffer from ambiguities associated with the subtraction of a “pure tidal field” from the full metric; such subtraction prescriptions are artificial and subjective. A robust operational definition is proposed here. It relies on inserting the body’s local metric within a global metric constructed in post-Newtonian theory; the global metric includes the external matter responsible for the tidal environment. When viewed in the post-Newtonian spacetime, the compact body appears as a skeletonized object with a specific multipole structure, moving on a given world line. The tidally induced multipole moments provide a description of this multipole structure. They manifest themselves, for example, in the body’s tidal acceleration, which is nonlinear in the tidal field. At leading order in the tidal interaction, the acceleration is proportional to the $k_2$ Love number as calculated in full general relativity. The computation of the multipole moments is carried out to the first post-Newtonian order, but the general method can in principle be extended to higher orders.

Using a set of high-resolution simulations we study the statistical correlation of dark matter halo properties with the large-scale environment. We consider halo populations split into four cosmic web (CW) elements: voids, walls, filaments, and nodes. For the first time we present a study of CW effects for halos covering six decades in mass: ${10}^8–{10}^{14}{h}^{-1}{\mathrm{M}}_{\odot }$. We find that the fraction of halos living in various web components is a strong function of mass, with the majority of $M>{10}^{12}{h}^{-1}{\mathrm{M}}_{\odot }$ halos living in filaments and nodes. Low mass halos are more equitably distributed in filaments, walls, and voids. For halo density profiles and formation times we find a universal mass threshold of $M_{th}\sim 6\times {10}^{10}{h}^{-1}{\mathrm{M}}_{\odot }$ below which these properties vary with environment. Here, filament halos have the steepest concentration-mass relation, walls are close to the overall mean, and void halos have the flattest relation. This amounts to $c_{200}$ for filament and void halos that are, respectively, 14% higher and 7% lower than the mean at $M=2\times {10}^8{h}^{-1}{\mathrm{M}}_{\odot }$. We find double power-law fits that very well describe $c(M)$ for the four environments in the whole probed mass range. A complementary picture is found for the average formation times, with the mass-formation time relations following trends shown for the concentrations: the nodes halos being the oldest and void halo the youngest. The CW environmental effect is much weaker when studying the halo spin and shapes. The trend with halo mass is reversed: the small halos with $M<{10}^{10}{h}^{-1}{\mathrm{M}}_{\odot }$ seem to be unaffected by the CW environment. Some weak trends are visible for more massive void and wall halos, which, on average, are characterized by lower spin and higher triaxiality parameters.

We investigate the prospects of the Spectrum-Roentgen-Gamma (SRG) mission in search for the keV-scale mass sterile neutrino dark matter radiatively decaying into active neutrinos and photons. The ongoing all-sky x-ray survey of the SRG space observatory with data acquired by the ART-XC and eROSITA telescopes can provide a possibility to fully explore the resonant production mechanism of the dark matter sterile neutrino, which exploits the lepton asymmetry in the primordial plasma consistent with cosmological limits from the big bang nucleosynthesis. In particular, it is shown that at the end of the four year all-sky survey, the sensitivity of the eROSITA telescope near the 3.5 keV line signal reported earlier can be comparable to that of the XMM-Newton with all collected data, which will allow one to carry out another independent study of the possible sterile neutrino decay signal in this area. In the energy range below $\approx 2.4\mathrm{keV}$, the expected constraints on the model parameters can be significantly stronger than those obtained with the XMM-Newton. From the ART-XC data, in the energy range approximately from 5 to 20 keV, it can be possible to get more stringent constraints than those obtained with NuSTAR so far. We conclude that the SRG mission has a very high potential in testing the sterile neutrino dark matter hypothesis.

Rossby modes ($r$-modes) of rotating neutron stars can be excited by the gravitomagnetic forces in coalescing binary systems. A previous study by Flanagan and Racine [Phys. Rev. D 75, 044001 (2007)] showed that this kind of dynamical tide (DT) can induce phase shifts of $\sim 0.1\mathrm{rad}$ on gravitational waveforms, which is detectable by third-generation (3G) detectors. We study the impact of this DT on measuring neutron-star parameters in the era of 3G detectors. We incorporate two universal relations among neutron-star properties predicted by different equations of state: (i) the well-known I-Love relation between momentum of inertia and ($f$-mode) tidal Love number, and (ii) a relation between the $r$-mode overlap and tidal Love number, which we newly explore. We find that $r$-mode DT will provide rich information about slowly rotating neutron stars with frequency 10–100 Hz and spin inclination angle 18°–110°. For a binary neutron-star system (with a signal-to-noise ratio $\sim 1500$ in the Cosmic Explorer), the spin frequency of each individual neutron star can be constrained to 6% (fractional error) in the best-case scenario. The degeneracy between the Love numbers of individual neutron stars is dramatically reduced: each individual Love number can be constrained to around 20% in the best case, while the fractional error for both symmetric and antisymmetric Love numbers are reduced by factors of around 300. Furthermore, DT also allows us to measure the spin inclination angles of the neutron stars, to 0.09 rad in the best case, and thus place constraints on neutron-star natal kicks and supernova explosion models. In addition to parameter estimation, we also develop a semianalytic method that accurately describes detailed features of the binary evolution that arise due to the DT.

The data from ground-based gravitational-wave detectors such as Advanced LIGO and Virgo must be calibrated to convert the digital output of photodetectors into a relative displacement of the test masses in the detectors, producing the quantity of interest for inference of astrophysical gravitational-wave sources. Both statistical uncertainties and systematic errors are associated with the calibration process, which would in turn affect the analysis of detected sources, if not accounted for. Currently, source characterization algorithms either entirely neglect the possibility of calibration uncertainties or account for them in a way that does not use knowledge of the calibration process itself. We present physiCal, a new approach to account for calibration errors during the source characterization step, which directly uses all the information available about the instrument calibration process. Rather than modeling the overall detector’s response function, we consider the individual components that contribute to the response. We implement this method and apply it to the compact binaries detected by LIGO and Virgo during the second observation run, as well as to simulated binary neutron stars for which the sky position and distance are known exactly. We find that the physiCal model performs as well as the method currently used within the LIGO-Virgo Collaboration, but additionally it enables improving the measurement of specific components of the instrument control through astrophysical calibration.

TianQin is a proposed space-borne gravitational-wave detection mission using circular high Earth orbits. The geocentric concept has raised questions about the disturbing effect of the nearby gravity field of the Earth-Moon system on the highly sensitive intersatellite ranging measurements. Here we examine the issue through high-precision numerical orbit simulations with detailed gravity-field models. By evaluating range accelerations between distant free-falling test masses, the study shows that the majority of the Earth-Moon’s gravity disturbances are not in TianQin’s detection frequency band above ${10}^{-4}\mathrm{Hz}$, and hence present no showstoppers to the mission.

We investigate the nonlinear transport processes and hydrodynamization of a system of gluons undergoing longitudinal boost-invariant expansion. The dynamics is described within the framework of the Boltzmann equation in the small-angle approximation. The kinetic equations for a suitable set of moments of the one-particle distribution function are derived. By investigating the stability and asymptotic resurgent properties of this dynamical system, we demonstrate, that its solutions exhibit a rather different behavior for large (UV) and small (IR) effective Knudsen numbers. Close to the forward attractor in the IR regime the constitutive relations of each moment can be written as a multiparameter transseries. This resummation scheme allows us to extend the definition of a transport coefficient to the nonequilibrium regime naturally. Each transport coefficient is renormalized by the nonperturbative contributions of the nonhydrodynamic modes. The Knudsen number dependence of the transport coefficient is governed by the corresponding renormalization group flow equation. An interesting feature of the Yang-Mills plasma in this regime is that it exhibits transient non-Newtonian behavior while hydrodynamizing. In the UV regime the solution for the moments can be written as a power-law asymptotic series with a finite radius of convergence. We show that radius of convergence of the UV perturbative expansion grows linearly as a function of the shear viscosity to entropy density ratio. Finally, we compare the universal properties in the pullback and forward attracting regions to other kinetic models including the relaxation time approximation and the effective kinetic Arnold-Moore-Yaffe theory.

The importance of implementing a proper regularization procedure in order to treat thermo and magnetic contributions within nonrenormalizable theories is investigated. Our study suggests that potential divergences should be isolated into the vacuum and purely magnetic contributions and then regularized while the convergent thermomagnetic contributions should be integrated over the full momentum range. This prescription is illustrated by applying the proper time formalism to the two flavor Polyakov-Nambu-Jona-Lasinio model, whose magnetic field–dependent coupling has been recently determined. Observables such as the pressure, magnetization, speed of sound squared, and specific heat evaluated within our scheme are compared with results furnished by other three possible prescriptions. We show that these quantities display a thermomagnetic behavior which is physically more consistent when our scheme is adopted. In particular, we demonstrate that naively regulating the (entangled) vacuum, magnetic, and thermomagnetic contributions leads to physically inconsistent results especially at the high temperature domain.