Standard detection and analysis techniques for transient gravitational waves make the assumption that detector data contains, at most, one signal at any time. As detectors improve in sensitivity, this assumption will no longer be valid. In this paper we examine how current search techniques for transient gravitational waves will behave under the presence of more than one signal. We perform searches on simulated data sets containing time-overlapping compact binary coalescences. This includes a modeled matched filter search (pycbc) and an unmodeled coherent search, coherent WaveBurst (cwb). Both of these searches are used by the LIGO-Virgo-KAGRA collaboration [1]. We find that both searches are capable of identifying both signals correctly when the signals are dissimilar in merger time, $|\mathrm{\Delta }{t}_c|\ge 1\mathrm{s}$, with pycbc missing only 1% of the overlapping binary black hole mergers it was provided. Both pipelines can find signal pairings within the region $|\mathrm{\Delta }{t}_c|<1\mathrm{s}$. However, clustering routines in the pipelines will cause only one of the two signals to be recovered, as such, the efficiency is reduced. Within this region, we find that cwb can identify both signals. We also find that matched filter searches can be modified to provide estimates of the correct parameters for each signal.

We simulate the decay of isolated, spherically symmetric droplets in a cosmological phase transition. It has long been posited that such heated droplets of the metastable state could form, and they have recently been observed in 3D multibubble simulations. In those simulations, the droplets were associated with a reduction in the wall velocity and a decrease in the kinetic energy of the fluid, with a consequent suppression in the gravitational wave power spectrum. In the present work, we track the wall speed and kinetic energy production in isolated droplets and compare them to those found in multibubble collisions. The late-time wall velocities that we observe match those of the 3D simulations, though we find that the spherical simulations are a poor predictor of the kinetic energy production. This implies that spherically symmetric simulations could be used to refine baryogenesis predictions due to the formation of droplets, but not to estimate any accompanying suppression of the gravitational wave signal.

In compact astrophysical objects, the neutrino density can be so high that neutrino-neutrino refraction can lead to fast flavor conversion of the kind ${\nu }_e{\overline{\nu }}_e\leftrightarrow {\nu }_x{\overline{\nu }}_x$ with $x=\mu$, $\tau$, depending on the neutrino angle distribution. Previously, we have shown that in a homogeneous, axisymmetric two-flavor system, these collective solutions evolve in analogy to a gyroscopic pendulum. In flavor space, its deviation from the weak-interaction direction is quantified by a variable $\cos \vartheta$ that moves between $+1$ and $\cos {\vartheta }_{\min }$, the latter following from a linear mode analysis. As a next step, we include collisional damping of flavor coherence, assuming a common damping rate $\mathrm{\Gamma }$ for all modes. Empirically we find that the damped pendular motion reaches an asymptotic level of pair conversion $f=A+(1-A)\cos {\vartheta }_{\min }$ (numerically $A\simeq 0.370$) that does not depend on details of the angular distribution (except for fixing $\cos {\vartheta }_{\min }$), the initial seed, nor $\mathrm{\Gamma }$. On the other hand, even a small asymmetry between the neutrino and antineutrino damping rates strongly changes this picture and can even enable flavor instabilities in otherwise stable systems.

We have evolved mergers of equal-mass binary quark stars, the total mass of which is close to the mass shedding limit of uniformly rotating configurations, in fully general relativistic hydrodynamic simulations, aimed at investigating the postmerger outcomes. In particular, we have identified the threshold mass for prompt black hole formation after the merger, by tracing the minimum lapse function as well as the amount of ejected material during the merger simulation. A semianalytical investigation based on the angular momentum contained in the merger remnant is also performed to verify the results. For the equation of state considered in this work, the maximum mass of cold spherical configurations is $2.10M_{\odot }$, the threshold mass is found between 3.05 and $3.10M_{\odot }$. This result is consistent (with a quantitative error smaller than 1%) with the universal relation derived from the numerical results of symmetric binary neutron star mergers. Contrary to the neutron star case, the threshold mass is close to the mass shedding limit of uniformly rotating quark star. Consequently, we have found that binary quark stars with total mass corresponding to the long-lived supramassive remnant for neutron star case, could experience collapse to black hole within several times dynamical timescale, making quark stars as exceptions of the commonly accepted postmerger scenarios for binary neutron star mergers. We have suggested explanation for both the similarity and the difference, between quark stars and neutron stars.

Fast and collisional flavor instabilities possibly occur in the neutrino decoupling regions of core-collapse supernovae and neutron-star mergers. To gain a better understanding of the relevant flavor dynamics, we numerically solve for the collisionally unstable evolution in a homogeneous, anisotropic model. In these calculations collisional instability is precipitated by unequal neutrino and antineutrino scattering rates. We compare the solutions obtained using neutral-current and charged-current interactions. We then study the nonlinear development of fast instabilities subjected to asymmetric scattering rates, finding evidence that the onset of collisional instability is hastened by fast oscillations. We also discuss connections to other recent works on collision-affected fast flavor conversion.

We consider a muonphilic axionlike particle (ALP), denoted as $a$, lighter than twice the muon mass. ALPs of this mass range dominantly decay into a pair of photons, induced by a triangular muon loop. Such light muonphilic ALPs are naturally long lived. At the atmosphere, the ALPs are copiously produced from charged-meson decays in air showers, such as ${\pi }^{\pm }\to {\mu }^{\pm }\nu a$, via the ALP-muon coupling $g_{a\mu \mu }$. After propagating tens of kilometers, the ALPs decay with $a\to \gamma \gamma$ inside large-volume Cherenkov detectors near Earth’s surface, such as Super-Kamiokande (SK). We find the present SK observation constrains on muonphilic ALPs of mass range [1 MeV, 30 MeV] and ALP-muon coupling $[{10}^{-3},{10}^2]$, assuming the proper decay length $c{\tau }_a$ in [${10}^{-3}\mathrm{km}$, ${10}^6\mathrm{km}$] either dependent on or independent of $g_{a\mu \mu }$. We conclude that atmospheric searches of such exotic states can be complementary to collider and beam-dump experiments as well as astrophysical probes.

We propose a novel and minimal framework where a light scalar field can give rise to dark matter (DM) self-interactions, while enhancing the $CP$ asymmetry required for successful baryon asymmetry of the Universe via leptogenesis route. For demonstration purpose we choose to work in a scotogenic seesaw scenario where the lightest among the right-handed neutrinos (RHN), introduced for generating light neutrino masses radiatively, play the role of DM while the heavier two can play nontrivial roles in generating DM relic as well as lepton asymmetry. While dark matter self-interactions mediated by an additional singlet scalar can alleviate the small scale issues of cold dark matter paradigm, the same scalar can give rise to new one-loop decay processes of heavy RHN into standard model leptons providing an enhanced contribution to $CP$ asymmetry, even with sub-TeV scale RHN mass. The thermally underabundant relic of DM due to large annihilation rates into its light mediator receives a late nonthermal contribution from a heavier RHN. With only five new particles involved in the scotogenic seesaw, each having nontrivial roles in generating DM relic and baryon asymmetry, the model can explain nonzero neutrino mass while being verifiable at different experiments related to DM direct detection, flavor physics, and colliders. The mechanism we demonstrated here by using a scotogenic seesaw scenario is also applicable to other models.

Interactions with a background medium modify in general the dispersion relation and canonical normalization of propagating particles. This can have an important phenomenological consequence when considering light dark matter coupling to quarks and leptons. In this paper, we address this issue in the vector dark matter background with the randomly distributed polarizations or a fixed polarization to the single direction. The observations associated with particle dispersion can give constraints on new light Abelian gauge boson models. Considering the solar neutrino transition and the electron mass measurement, stringent bounds can be put on the gauged $L_{\mu }-L_{\tau }$ model and the dark photon model. Moreover, the classical vector field turns out to induce drastic changes in the particle normalization, which rule out a significant parameter region of the generic vector dark matter model.

This paper investigates the importance of radiative corrections for first-order phase transitions. While it is known how to incorporate higher-order corrections to the rate, a detailed convergence analysis has not been performed. This paper performs such an analysis, and the results indicate that radiative corrections can be large while retaining perturbativity. To illustrate the calculations, three representative models are considered. Relevant observables are calculated for each model, and the reliability of perturbation theory is discussed.

We study the localization properties of the eigenmodes of the staggered Dirac operator across the deconfinement transition in finite-temperature ${\mathbb{Z}}_3$ pure gauge theory on the lattice in $2+1$ dimensions. This allows for nontrivial tests of the sea-islands picture of localization, according to which low modes should localize on favorable Polyakov-loop fluctuations in the deconfined phase of a gauge theory. We observe localized low modes in the deconfined phase of the theory, both in the real Polyakov-loop sector, where they are expected, and in the complex Polyakov-loop sectors, where they are not. Our findings expose the limitations of the standard sea-islands picture and call for its refinement. An improved picture, where spatial hopping terms play a more prominent role, is proposed and found to be in excellent agreement with numerical results.

The production of single-charmed baryons ${\mathrm{\Lambda }}_c^{+}{\mathrm{\Lambda }}_c^{-}$, ${\mathrm{\Lambda }}_c^{+}{\mathrm{\Sigma }}_c^{-}+\mathrm{H}.\mathrm{c}.$, and ${\mathrm{\Sigma }}_c^{+}{\mathrm{\Sigma }}_c^{-}$ in $p\overline{p}$ collisions is studied in the framework of a constituent quark model that has satisfactorily described the $N\overline{N}$ system and the strangeness production $p\overline{p}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}$, $\mathrm{\Lambda }\overline{\mathrm{\Sigma }}$, and $\mathrm{\Sigma }\overline{\mathrm{\Sigma }}$ processes. Predictions on the total cross sections are analyzed for different approaches to the underlying $n\overline{n}\to c\overline{c}$ process, mediated by one-gluon annihilation diagrams. The results indicate that the cross section is on the order of 1 nb between 10 and 14 GeV for ${\mathrm{\Lambda }}_c^{+}{\mathrm{\Lambda }}_c^{-}$ and ${\mathrm{\Lambda }}_c^{+}{\mathrm{\Sigma }}_c^{-}$ channels and around 0.01–0.1 nb for ${\mathrm{\Sigma }}_c^{+}{\mathrm{\Sigma }}_c^{-}$. These estimations can be relevant for their future search in facilities like PANDA.

In this article, we present the result for the QCD corrections to the decay of the Higgs boson into two photons in the large-${\beta }_0$ limit of QCD, providing the first two terms in the heavy-top expansion. From our results, one can easily read off the exact leading-$n_f$ QCD contributions in analytic form to all orders in the strong coupling, ${\alpha }_s$, where $n_f$ is the number of massless quarks, and identify the leading renormalon singularities. We give explicit results for the leading-$n_f$ coefficients at six and seven loops and use the large-${\beta }_0$ result to speculate about the size of yet unknown (but small) higher-order contributions to the QCD series.

By analyzing $e^{+}{e}^{-}$ annihilation data with an integrated luminosity of $2.93{\mathrm{fb}}^{-1}$ collected at the center-of-mass energy $\sqrt{s}=3.773\mathrm{GeV}$ with the BESIII detector, we present the first absolute measurements of the branching fractions of twenty Cabibbo-suppressed hadronic $D^{0(+)}$ decays involving multiple pions. The highest four branching fractions obtained are $\mathcal{B}(D^0\to {\pi }^{+}{\pi }^{-}{\pi }^0)=(1.343\pm 0.013_{\mathrm{stat}}\pm 0.016_{\mathrm{syst}})\%$, $\mathcal{B}(D^0\to {\pi }^{+}{\pi }^{-}2{\pi }^0)=(1.002\pm 0.019_{\mathrm{stat}}\pm 0.024_{\mathrm{syst}})\%$, $\mathcal{B}(D^{+}\to 2{\pi }^{+}{\pi }^{-}{\pi }^0)=(1.165\pm 0.021_{\mathrm{stat}}\pm 0.021_{\mathrm{syst}})\%$, and $\mathcal{B}(D^{+}\to 2{\pi }^{+}{\pi }^{-}2{\pi }^0)=(1.074\pm 0.040_{\mathrm{stat}}\pm 0.030_{\mathrm{syst}})\%$. The $CP$ asymmetries for the six decays with highest signal yields are also determined and found to be compatible with zero.

The quantum effective action of nonminimal vector fields with Abelian or non-Abelian gauge degrees of freedom in curved spacetime is studied. The Proca or Yang-Mills fields are coupled to a local masslike term acting in both coordinate and gauge spaces. Pathologies due to gauge invariance in the ultraviolet are avoided through the introduction of a non-Abelian version of the Stueckelberg field. It is found that the breaking of gauge invariance induced by the mass term affects only the tree-level part of the effective action. The ultraviolet divergent part of the effective action to one loop is obtained using the method of covariant symbols and dimensional regularization. Formulas are given valid for any spacetime dimension and explicit results are shown for the two-dimensional case. As already happened for a single vector field, the ultraviolet divergences are local but not of polynomial type.

Physical principles such as unitarity, causality, and locality can constrain the space of consistent effective field theories (EFTs) by imposing two-sided bounds on the allowed values of Wilson coefficients. In this paper, we consider the bounds that arise from the requirement of low energy causality alone, without appealing to any assumptions about UV physics. We focus on shift-symmetric theories, and consider bounds that arise from the propagation around both a homogeneous and a spherically symmetric scalar field background. We find that low energy causality, namely the requirement that there are no resolvable time advances within the regime of validity of the EFT, produces two-sided bounds in agreement with compact positivity constraints previously obtained from $2\to 2$ scattering amplitude dispersion relations using full crossing symmetry.

The Gibbons-Werner method has been widely used in the gravitational deflection problem of particles moving in the curved spacetime. By applying the Gauss-Bonnet theorem (GBT) to regions constructed in a two-dimensional manifold, the deflection angle can be expressed and calculated in a geometric manner. For asymptotically flat spacetimes, an infinite region is usually chosen. While for some asymptotically nonflat spacetimes, the infinite region is ill defined due to the singular behavior of the metric, thus some special regions were constructed to solve the ill-defined problem. We propose a generalized method in which the choice freedom of the region where the GBT is applied is significantly enlarged. Our generalized method not only describes the conventional methods uniformly, but also lead to a formula which greatly simplifies the calculation. Additionally, we work out the deflection angle of the massive particle in the static spherically symmetric spacetime in conformal Weyl gravity based on the generalized method and the new formula.

A crucial challenge to the ongoing endeavor of spaceborne gravitational wave (GW) detection resides in the laser phase noise, typically 7 to 8 orders of magnitude above the inevitable noise. The arm-locking technique was proposed to suppress the noise in prestabilized laser beams. Based on the feedback control theory, it is implemented by appropriate design of the signal routing architecture, particularly the controllers’ transfer functions. Theoretically and experimentally, the technique has been demonstrated to be capable of suppressing the laser phase noise by approximately 2–4 orders of magnitude while taking into account various aspects, such as the gain and distribution of nulls in the Bode plot and the laser frequency pulling associated with the Doppler frequency subtraction. Consequently, the resultant noise floor is composed of the sources attributed to the clock jitter, optical bench motion, test mass fluctuations, and shot-noise phase fluctuations at the photodetectors, whereas the magnitudes of these noises largely remain unchanged during the process. In addition, the original GW signals are deformed through the arm-locking control loop and therefore bear specific features governed by the associated arm-locking scheme. Nonetheless, the remaining laser phase noise from the arm-locking feedback routing settles within the capability threshold of the time-delay interferometry (TDI). In this regard, it is generally understood that the output of arm locking furnishes the input of TDI, through which the residual noise is further reduced to the desired level at a postprocessing stage. In this work, we investigate the specific schemes regarding how the arm-locking output is processed further by the TDI algorithm. Specific forms of the TDI combinations are derived in accordance with suppressed laser phase noise and deformed signals of GWs. To the best of our knowledge, such explicit TDI schemes aiming at the processed signals by the arm-locking technique have not been explored in the literature. Also, we propose a real-time acousto-optic modulation scheme to compensate for the noise due to optical bench motion. The resultant noise floor, in turn, is primarily composed of those due to the test mass noise and shot noise. The sensitivity curves are evaluated and indicate that the resulting performance meets the requirement of the Laser Interferometer Space Antenna detector. Although the forms of the obtained arm-locking TDI solutions are different from the conventional ones, the response functions, residual noise power spectral densities, and sensitivity curves are found to be identical to their counterparts. Further implications of the present findings are also addressed.

A primordial black hole (PBH) is thought to be made of the regular matter or ordinary mass ($M$) only, and hence could have already been decayed due to the Hawking radiation if its initial ordinary mass were $\lesssim 5\times {10}^{11}\mathrm{kg}$. Here, we study the role of a gravitomagnetic monopole for the evaporation of PBHs, and propose that the lower-energy PBHs (equivalent to ordinary mass $M\ll 5\times {10}^{11}\mathrm{kg}$) could still exist in our present Universe, if it has a gravitomagnetic monopole. If a PBH was initially made of both regular matter and a gravitomagnetic monopole, the regular matter could decay away due to the Hawking radiation. The remnant gravitomagnetic monopole might not entirely decay, which could still be found as a PBH in the form of the ‘pseudomass-energy’. If a PBH with $M\gtrsim 5\times {10}^{11}\mathrm{kg}$ is detected, one may not be able to conclude if it has gravitomagnetic monopole, but, a plausible detection of a relatively low-energy (equivalent to $2.176\times {10}^{-8}\mathrm{kg}<M\lesssim 5\times {10}^{11}\mathrm{kg}$) PBH in future may imply the existence of a gravitomagnetic monopole PBH, which may or may not contain the ordinary mass.

It is anticipated that the gravitational radiation detected in future gravitational wave (GW) detectors from binary neutron star (NS) mergers can probe the high-density equation of state (EOS). We perform the first simulations of binary NS mergers which adopt various parametrizations of the quark-hadron crossover (QHC) EOS. These are constructed from combinations of a hadronic EOS ($n_b<2n_0$) and a quark-matter EOS ($n_b>5n_0$), where $n_b$ and $n_0$ are the baryon number density and the nuclear saturation density, respectively. At the crossover densities ($2n_0<n_b<5n_0$) the QHC EOSs continuously soften, while remaining stiffer than hadronic and first-order phase transition EOSs, achieving the stiffness of strongly correlated quark matter. This enhanced stiffness leads to significantly longer lifetimes of the postmerger NS than that for a pure hadronic EOS. We find a dual nature of these EOSs such that their maximum chirp GW frequencies $f_{\max }$ fall into the category of a soft EOS while the dominant peak frequencies ($f_{\mathrm{peak}}$) of the postmerger stage fall in between that of a soft and stiff hadronic EOS. An observation of this kind of dual nature in the characteristic GW frequencies will provide crucial evidence for the existence of strongly interacting quark matter at the crossover densities for QCD.