During their most recent observing run, LIGO/Virgo reported the gravitational wave (GW) transient S191110af, a burst signal at a frequency of 1.78 kHz that lasted for 0.104 s. While this signal was later deemed nonastrophysical, genuine detections of uncertain origin will occur in the future. Here we study the potential for detecting GWs from neutron star fluid oscillations, which have mode frequency and duration matching those of S191110af and which can be used to constrain the equation of state of nuclear matter. Assuming that such transient oscillations can be excited to energies typical of a pulsar glitch, we use measured properties of known glitching pulsars to estimate the amplitude of GWs produced by such events. We find that current GW detectors may observe nearby pulsars undergoing large events with energy similar to Vela pulsar glitch energies, while next-generation detectors could observe a significant number of events. Finally, we show that it is possible to distinguish between GWs produced by rapidly rotating and slowly rotating pulsars from the imprint of rotation on the $f$-mode frequency.

While the gravitational-wave (GW) signal GW170817 was accompanied by a variety of electromagnetic (EM) counterparts, sufficiently high-mass binary neutron star (BNS) mergers are expected to be unable to power bright EM counterparts. The putative high-mass binary BNS merger GW190425, for which no confirmed EM counterpart has been identified, may be an example of such a system. Since current and future GW detectors are expected to detect many more BNS mergers, it is important to understand how well we will be able to distinguish high-mass BNSs and low-mass binary black holes (BBHs) solely from their GW signals. To do this, we consider the imprint of the tidal deformability of the neutron stars on the GW signal for systems undergoing prompt black hole formation after merger. We model the BNS signals using hybrid numerical relativity–tidal effective-one-body waveforms. Specifically, we consider a set of five nonspinning equal-mass BNS signals with total masses of 2.7, 3.0, $3.2M_{\odot }$ and with three different equations of state, as well as the analogous BBH signals. We perform Bayesian parameter estimation on these signals at luminosity distances of 40 and 98 Mpc in an Advanced LIGO-Advanced Virgo network and an Advanced LIGO-Advanced Virgo-KAGRA network with sensitivities similar to the third and fourth observing runs (O3 and O4), respectively, and at luminosity distances of 369 and 835 Mpc in a network of two Cosmic Explorers and one Einstein Telescope, with a Cosmic Explorer sensitivity similar to Stage 2. Our analysis suggests that we cannot distinguish the signals from high-mass BNSs and BBHs at a 90% credible level with the O3-like network even at 40 Mpc. However, we can distinguish all but the most compact BNSs that we consider in our study from BBHs at 40 Mpc at a $\ge 95\%$ credible level using the O4-like network and can even distinguish them at a $>99.2\%$ ($\ge 97\%$) credible level at 369 (835) Mpc using the 3G network. Additionally, we present a simple method to compute the leading effect of the Earth’s rotation on the response of a gravitational wave detector in the frequency domain.

It is entirely plausible that during the primordial quark-hadron phase transition, microseconds after the big bang, the Universe may experience supercooling accompanied by mini inflation leading to a first-order phase transition from quarks to hadrons. The relics, in the form of quark nuggets, with baryon number beyond a critical value will survive the evolution of the Universe. The quark nuggets are candidates of strange quark matter. It is conjectured that color confinement turns the physical vacuum to an event horizon for quarks and gluons. The horizon can be crossed only by quantum tunneling. The process just mentioned is the QCD counterpart of Hawking radiation from gravitational black holes. Tunneling of neutrons from the nuggets is equivalent to Hawking radiation from the gravitational black hole. Thus, when the Hawking temperature of the quark nuggets gets turned off, tunneling will stop and the nuggets will survive forever. The baryon number and the mass of these nuggets are derived using this theoretical format. The results agree well with the prediction using other phenomenological models. Further, the variation of Hawking temperature as a function of baryon number and mass of the nugget mimics chiral phase transition, somewhat similar to the QCD phase transition. Finally, the strange quark nuggets may well be the candidates of baryonic dark matter.

Dilepton production rate (DPR) from hot and dense quark matter is studied in the presence of an arbitrary external magnetic field using the 2-flavor Nambu–Jona-Lasinio model. The anomalous magnetic moment (AMM) of the quarks is taken into consideration while calculating the constituent quark mass as well as the DPR from the thermomagnetic medium. An infinite number of quark Landau levels is incorporated so that no approximations are made on the strength of the background magnetic field. The analytic structure of the two point vector current correlation function in the complex energy plane reveals that, in addition to the usual unitary cut, a nontrival Landau cut appears in the physical kinematic domains solely due to the external magnetic field. Moreover, these kinematic domains of the unitary and Landau cuts are found to be significantly modified due to the AMM of the quarks. With finite AMM of the quarks, for certain values of the external magnetic field, the kinematically forbidden gap between the unitary and Landau cuts are shown to vanish leading to the generation of a continuous spectrum of dilepton emission over the whole invariant mass region not observed earlier.

In this paper, we perform a detailed analysis of the phenomenology of leptogenesis and dark matter from a low scale seesaw mechanism. In the framework of Neutrinophilic two Higgs doublet model, we further introduce one scalar singlet $\varphi$ and one Dirac fermion singlet $\chi$, which are charged under a $Z_2$ symmetry. Assuming the coupling of $\chi$ is extremely small, it serves as feebly interacting massive particle (FIMP) dark matter. Heavy right-hand neutrinos $N$ provide a common origin for tiny neutrino mass (via a seesaw mechanism), leptogenesis (via $N\to {\ell }_L{\mathrm{\Phi }}_{\nu }^{*}$, ${\overline{\ell }}_L{\mathrm{\Phi }}_{\nu }$), and dark matter (via $N\to \chi \varphi$). With hierarchical right-hand neutrino masses, the explicit calculation shows that successful thermal leptogenesis is viable even for TeV-scale $N_1$ with $0.4\mathrm{GeV}\lesssim v_{\nu }\lesssim 1\mathrm{GeV}$ and lightest neutrino mass $m_1\lesssim {10}^{-11}\mathrm{eV}$. In such a scenario, light FIMP dark matter in the keV to MeV range is naturally expected. The common parameter space for neutrino mass, natural leptogenesis, and FIMP dark matter is also obtained in this paper.

Given the lack of evidence for new particle discoveries at the Large Hadron Collider (LHC), it is critical to broaden the search program. A variety of model-independent searches have been proposed, adding sensitivity to unexpected signals. There are generally two types of such searches: those that rely heavily on simulations and those that are entirely based on (unlabeled) data. This paper introduces a hybrid method that makes the best of both approaches. For potential signals that are resonant in one known feature, this new method first learns a parametrized reweighting function to morph a given simulation to match the data in sidebands. This function is then interpolated into the signal region, and then the reweighted background-only simulation can be used for supervised learning as well as for background estimation. The background estimation from the reweighted simulation allows for nontrivial correlations between features used for classification and the resonant feature. A dijet search with jet substructure is used to illustrate the new method. Future applications of Simulation Assisted Likelihood-free Anomaly Detection (salad) include a variety of final states and potential combinations with other model-independent approaches.

We study the phenomenology of simplified $Z^{\prime }$ models with a global $U(2{)}^3$ flavor symmetry in the quark sector, broken solely by the Standard Model Yukawa couplings. This flavor symmetry, known as less-minimal flavor violation, protects $\mathrm{\Delta }F=2$ processes from dangerously large new physics (NP) effects and at the same time provides a free complex phase in $b\to s$ transitions, allowing for an explanation of the hints for additional direct $CP$ violation in kaon decays (${\epsilon }^{\prime }/\epsilon$) and in hadronic $B$-decays ($B\to K\pi$ puzzle). Furthermore, including the couplings of the $Z^{\prime }$ boson to the leptons, it is possible to address the intriguing hints for NP (above the $5\sigma$ level) in $b\to s{\ell }^{+}{\ell }^{-}$ transitions. Taking into account all flavor observables in a global fit, we find that our model can (for the first time) provide a common explanation for ${\epsilon }^{\prime }/\epsilon$, the $B\to K\pi$ puzzle and $b\to s{\ell }^{+}{\ell }^{-}$ data. Sizeable $CP$ violation in $b\to s{\ell }^{+}{\ell }^{-}$ observables, in particular $A_8$, is predicted, which can be tested in the near future, and an explanation of the $B\to K\pi$ and ${\epsilon }^{\prime }/\epsilon$ puzzles leads to effects in dijet tails at the LHC that are not far below the current limits. If we require that also $b\to s{\ell }^{+}{\ell }^{-}$ anomalies are explained, cancellations in dimuon tails (possibly by a second $Z^{\prime }$) are needed to satisfy LHC data.

The transition of quark-gluon plasma from fluid-dynamical regime to freeze-out is accompanied by the onset of instabilities. In the present paper, we investigate the impact of the magnetic field on the Rayleigh instability. We show that extremely strong field generated in peripheral heavy ion collisions has an insignificant influence on the Rayleigh bubble dynamics. Magnetic “friction” turns out to be much weaker than the viscous friction.

Ratio of the yield of strange hadrons to pions is considered as an important observable in studying the properties of the system produced in relativistic heavy ion collisions. Production of strange hadrons $K,\overline{K},\mathrm{\Lambda },\mathrm{\Sigma },\mathrm{\Xi }$, and $\mathrm{\Omega }$ has been evaluated microscopically using rate equations by considering their hadronic interaction cross sections in an expanding medium. The yields obtained from rate equations are normalized with thermal pions and compared with the measurements from Pb-Pb collisions at various multiplicities at LHC energy. The calculation has been done for various initial and freeze-out conditions. At 2760 GeV, LHC energy, $\mathrm{\Lambda }$, $\mathrm{\Xi }$, $\mathrm{\Omega }$ freeze-out close to $T_C$ and $K_s^0$ freezes-out little later. But there is a subtle difference in freeze-out temperatures of different species which may be distinguishable at lower colliding energies.

We propose and validate a method of antineutrino energy reconstruction for charged-current meson-less interactions on composite fully active targets containing hydrogen (such as hydrocarbon scintillator), which is largely free of the poorly understood nuclear effects that usually distort and bias attempts to measure neutrino energy. The method is based on the precise event-by-event measurement of the outgoing neutron kinetic energy and the subsequent assessment of the momentum imbalance on the plane transverse to the incoming antineutrino direction. For an antineutrino flux peaked at around 600 MeV measured using a finely grained $2\times 2\times 2{\mathrm{m}}^3$ three-dimensional scintillator tracker, the neutrino energy resolution is expected to be around 7%, compared to the 15% expected using traditional neutrino energy reconstruction techniques. Analogous results can be obtained for other detectors with similar characteristics.

We analytically compute the three-loop corrections to the relation between the renormalized quark masses defined in the minimal-subtraction ($\overline{\mathrm{MS}}$) and the regularization-invariant symmetric momentum-subtraction (RI/SMOM) schemes. Our result is valid in the Landau gauge and can be used to reduce the uncertainty in a lattice determination of the $\overline{\mathrm{MS}}$ quark masses.

Previous research has shown that the peak of the quarkonium entropy at the deconfinement transition would be related to the entropic force which induces the melting of quarkonium. In this article, we study the effect of backreaction on the entropic force in a strongly coupled plasma of adjoint matter. The backreaction covered here comes from the presence of static heavy quarks evenly distributed over such a plasma. It is found that the inclusion of backreaction increases the entropic force thus enhancing the quarkonium dissociation, in accord with the findings of the imaginary potential.

In the present paper we numerically construct new nontopological, spontaneously scalarized neutron stars in the tensor-multiscalar theories of gravity whose target space is a three-dimensional maximally symmetric space, namely either ${\mathbb{S}}^3$, ${\mathbb{H}}^3$ or ${\mathbb{R}}^3$, and in the case of a nontrivial map $\phi :\text{spacetime}\to \text{target space}$. The theories of gravity admitting scalarization are characterized by the fact that the field equations always admit the general relativistic solution but for certain ranges of the parameters space it loses stability and nonlinear development of a scalar field is observed. Thus, in order to determine the values of the parameters where such scalarization is possible we studied the stability of the general relativistic solution within the framework of the considered tensor-multiscalar theories. Based on these results we could obtain a family of scalarized branches characterized by the number of the scalar field nodes. These branches bifurcate from the general relativistic solution at the points where new unstable modes appear and they are energetically more favorable over the pure Einstein solutions. Interestingly, in certain parameter ranges we could obtained nonuniqueness within a single branch of scalarized solutions.

It is known that approximating the Regge-Wheeler potential with step functions significantly modifies the Schwarzschild black hole quasinormal mode spectrum. Surprisingly, this change in the spectrum has little impact on the ringdown waveform. We examine whether this issue is caused by the jump discontinuities and/or the piecewise constant nature of step functions. We show that replacing the step functions with a continuous piecewise linear function does not qualitatively change the results. However, in contrast to previously published results, we discover that the ringdown waveform can be approximated to arbitrary precision using either step functions or a piecewise linear function. Thus, this approximation process provides a new mathematical tool to calculate the ringdown waveform. In addition, similar to normal modes, the quasinormal modes of the approximate potentials seem to form a complete set that describes the entire time evolution of the ringdown waveform. We also examine smoother approximations to the Regge-Wheeler potential, where the quasinormal modes can be computed exactly, to better understand how different portions of the potential impact various regions of the quasinormal mode spectrum.

The equilibrium configuration of white dwarfs composed of a charged perfect fluid is investigated in the context of the $f(R,\mathcal{T})$ gravity, for which $R$ and $\mathcal{T}$ stand for the Ricci scalar and the trace of the energy-momentum tensor, respectively. By considering the functional form $f(R,\mathcal{T})=R+2\chi \mathcal{T}$, where $\chi$ is the matter-geometry coupling constant, and for a Gaussian ansatz for the electric distribution, some physical properties of charged white dwarfs were derived, namely, mass, radius, charge, electric field, effective pressure, and energy density; their dependence on the parameter $\chi$ was also derived. In particular, the $\chi$ value important for the equilibrium configurations of charged white dwarfs has the same scale of $10^{-4}$ of that for noncharged stars and the order of the charge was $10^{20}\mathrm{C}$, which scales with the value of one solar mass, i.e., $\sqrt{G}{M}_{\odot }\sim 10^{20}\mathrm{C}$. We have also shown that charged white dwarf stars in the context of the $f(R,\mathcal{T})$ have surface electric fields below the Schwinger limit of $1.3\times {10}^{18}\mathrm{V}/\mathrm{m}$. In particular, a striking feature of the coupling between the effects of charge and $f(R,\mathcal{T})$ gravity theory is that the modifications in the background gravity increase the stellar radius, which in turn diminishes the surface electric field, thus enhancing stellar stability of charged stars in comparison with general relativity (GR) theory. Most importantly, our study reveals that the present $f(R,\mathcal{T})$ gravity model can suitably explain the super-Chandrasekhar limiting mass white dwarfs, which are supposed to be the reason behind the overluminous SNeIa and remain mostly unexplained in the background of GR.

We present SphericalNR, a new framework for the publicly available Einstein Toolkit that numerically solves the Einstein field equations coupled to the equations of general relativistic magnetohydrodynamic (GRMHD) in a $3+1$ split of spacetime in spherical coordinates without symmetry assumptions. The spacetime evolution is performed using reference-metric versions of either the Baumgarte-Shapiro-Shibata-Nakamura equations or the fully covariant and conformal Z4 system with constraint damping. We have developed a reference-metric version of the Valencia formulation of GRMHD with a vector potential method, guaranteeing the absence of magnetic monopoles during the evolution. In our framework, every dynamical field (both spacetime and matter) is evolved using its components in an orthonormal basis with respect to the spherical reference metric. Furthermore, all geometric information about the spherical coordinate system is encoded in source terms appearing in the evolution equations. This allows for the straightforward extension of Cartesian high-resolution shock-capturing finite volume codes to use spherical coordinates with our framework. To this end, we have adapted GRHydro, a Cartesian finite volume GRMHD code already available in the Einstein Toolkit, to use spherical coordinates. We present the full evolution equations of the framework, as well as details of its implementation in the Einstein Toolkit. We validate SphericalNR by demonstrating it passes a variety of challenging code tests in static and dynamical spacetimes.

We present simulations of binary neutron star mergers with equations of state (EoSs) that have input from holography, and analyze the spectral properties of the resulting waveforms. These EoSs consist of a standard nuclear matter EoS at low densities, transitioning to a state-of-the-art holographic EoS with first-order deconfinement phase transition in the otherwise intractable high-density regime. Depending on the transition density, the characteristic frequencies in the spectrum produced from the hybrid EoSs are shifted to significantly lower values. Equal-mass binaries with a total mass of $2.8M_{\odot }$ reach densities in the quark matter phase in the core of the transient hypermassive neutron star, which then induces an immediate gravitational collapse.

Probing low mass (sub-GeV—few GeV) weakly interacting massive particle (WIMP) candidates of dark matter through WIMP-induced nuclear recoils in direct detection experiments requires the use of detector materials consisting of low mass target nuclei and low threshold energy. Here we explore the potential of superheated liquid detectors (SLD) with a hydrogen containing liquid, namely, tetrafluoroethane (${\mathrm{C}}_2{\mathrm{H}}_2{\mathrm{F}}_4$) (b.p.$-26.3°\mathrm{C}$), as the target material for probing low mass WIMPs. It is found that few-keV level recoil energy thresholds possible for bubble nucleation by WIMP-induced ${}^{12}\mathrm{C}$ and ${}^{19}\mathrm{F}$ recoils in ${\mathrm{C}}_2{\mathrm{H}}_2{\mathrm{F}}_4$ SLDs operated at atmospheric pressure and gamma-ray insensitive temperatures of $T\lesssim 35°\mathrm{C}$ have the potential to allow WIMPs in the few-GeV mass range to be probed at a WIMP-nucleon spin-independent cross section sensitivity levels (90% C.L.) better than $4.6\times {10}^{-5}\mathrm{pb}$ at WIMP masses down to $\sim 4\mathrm{GeV}$ with a total exposure of $\sim 1000\mathrm{kg}.\mathrm{day}$, provided that the “thermodynamic efficiency” ${\eta }_{\mathrm{T}}$ that determines the bubble nucleation thresholds for the recoiling nuclei in ${\mathrm{C}}_2{\mathrm{H}}_2{\mathrm{F}}_4$ is $\sim 50\%$ or higher. Sensitivity to sub-GeV WIMP masses generally requires the detector to be sensitive to the WIMP-induced ${}^1\mathrm{H}$ recoils, which in turn requires the detector to be operated at temperatures $T\gtrsim 50°\mathrm{C}$ and ${\eta }_{\mathrm{T}}$ close to 100%. At such relatively high temperatures (at atmospheric pressure), however, the detector would be sensitive to background gamma rays.

A first detection of terrestrial gravity noise in gravitational-wave detectors is a formidable challenge. With the help of environmental sensors, it can in principle be achieved before the noise becomes dominant by estimating correlations between environmental sensors and the detector. The main complication is to disentangle different coupling mechanisms between the environment and the detector. In this paper, we analyze the relations between physical couplings and correlations that involve ground motion and LIGO strain data h(t) recorded during its second science run in 2016 and 2017. We find that all noise correlated with ground motion was more than an order of magnitude lower than dominant low-frequency instrument noise, and the dominant coupling over part of the spectrum between ground and h(t) was residual coupling through the seismic-isolation system. We also present the most accurate gravitational coupling model so far based on a detailed analysis of data from a seismic array. Despite our best efforts, we were not able to unambiguously identify gravitational coupling in the data, but our improved models confirm previous predictions that gravitational coupling might already dominate linear ground-to-h(t) coupling over parts of the low-frequency, gravitational-wave observation band.

We analyze the Gross-Neveu model in the limit of large number of flavors of massless fermions. We study the phase diagram in a two and three dimensional periodic box at a fixed thermal to spatial aspect ratio, $\frac{\beta }{\ell }$, with a flavor independent chemical potential. We assume the bilinear condensate, when one exists, has a specific momentum in the spatial direction(s). The main known features of the phase diagram in the $\ell \to \infty$ limit of the two dimensional model are also seen on a finite $\ell \times \beta$ torus—a phase with a homogeneous (zero momentum) condensate; a phase with an inhomogeneous (nonzero momentum) condensate and a phase with no condensate. We observe that the inhomogeneous phase contains several subphases characterized by a specific spatial momentum. Unlike the two dimensional model, we do not find evidence for a phase with a inhomogeneous condensate in the three dimensional model.