Working by analogy, we use the description of light fluctuations due to random collisions of the radiating atoms to figure out why the reduction of the coherence for light propagating a cosmological distance in the fluctuating background space is negligibly small to be observed by the stellar interferometry.

We propose a space-based gravitational wave (GW) detector consisting of two spatially separated, drag-free satellites sharing ultrastable optical laser light over a single baseline. Each satellite contains an optical lattice atomic clock, which serves as a sensitive, narrowband detector of the local frequency of the shared laser light. A synchronized two-clock comparison between the satellites will be sensitive to the effective Doppler shifts induced by incident GWs at a level competitive with other proposed space-based GW detectors, while providing complementary features. The detected signal is a differential frequency shift of the shared laser light due to the relative velocity of the satellites, and the detection window can be tuned through the control sequence applied to the atoms’ internal states. This scheme enables the detection of GWs from continuous, spectrally narrow sources, such as compact binary inspirals, with frequencies ranging from $\sim 3\mathrm{mHz}–10\mathrm{Hz}$ without loss of sensitivity, thereby bridging the detection gap between space-based and terrestrial optical interferometric GW detectors. Our proposed GW detector employs just two satellites, is compatible with integration with an optical interferometric detector, and requires only realistic improvements to existing ground-based clock and laser technologies.

The inspiral of stellar-mass compact objects, like neutron stars or stellar-mass black holes, into supermassive black holes provides a wealth of information about the strong gravitational-field regime via the emission of gravitational waves. In order to detect and analyze these signals, accurate waveform templates which include the effects of the compact object’s gravitational self-force are required. For computational efficiency, adiabatic templates are often used. These accurately reproduce orbit-averaged trajectories arising from the first-order self-force, but neglect other effects, such as transient resonances, where the radial and poloidal fundamental frequencies become commensurate. During such resonances the flux of gravitational waves can be diminished or enhanced, leading to a shift in the compact object’s trajectory and the phase of the waveform. We present an evolution scheme for studying the effects of transient resonances and apply this to an astrophysically motivated population. We find that a large proportion of systems encounter a low-order resonance in the later stages of inspiral; however, the resulting effect on signal-to-noise recovery is small as a consequence of the low eccentricity of the inspirals. Neglecting the effects of transient resonances leads to a loss of 4% of detectable signals.

We consider stationary, axially symmetric toroids rotating around spinless black holes, assuming the general-relativistic Keplerian rotation law, in the first post-Newtonian approximation. Numerical investigation shows that the angular momentum accumulates almost exclusively within toroids. It appears that various types of dragging (antidragging) effects are positively correlated with the ratio $M_{\mathrm{D}}/m$ ($M_{\mathrm{D}}$ is the mass of a toroid, and $m$ is the mass of the black hole)—moreover, their maxima are proportional to $M_{\mathrm{D}}/m$. The horizontal sizes of investigated toroids range from c. 50 to c. 450 of Schwarzschild radii $R_{\mathrm{S}}$ of the central black hole; their mass $M_{\mathrm{D}}\in ({10}^{-4}m,40m)$, and the radial size of the system is c. 500 $R_{\mathrm{S}}$. We found that the relative strength of various dragging (antidragging) effects does not change with the mass ratio, but it depends on the size of toroids. Several isoperimetric inequalities involving angular momentum are shown to hold true.

Gravitational wave astronomy has become a reality after the historical detections accomplished during the first observing run of the two advanced LIGO detectors. In the following years, the number of detections is expected to increase significantly with the full commissioning of the advanced LIGO, advanced Virgo and KAGRA detectors. The development of sophisticated data analysis techniques to improve the opportunities of detection for low signal-to-noise-ratio events is, hence, a most crucial effort. In this paper, we present one such technique, dictionary-learning algorithms, which have been extensively developed in the last few years and successfully applied mostly in the context of image processing. However, to the best of our knowledge, such algorithms have not yet been employed to denoise gravitational wave signals. By building dictionaries from numerical relativity templates of both binary black holes mergers and bursts of rotational core collapse, we show how machine-learning algorithms based on dictionaries can also be successfully applied for gravitational wave denoising. We use a subset of signals from both catalogs, embedded in nonwhite Gaussian noise, to assess our techniques with a large sample of tests and to find the best model parameters. The application of our method to the actual signal GW150914 shows promising results. Dictionary-learning algorithms could be a complementary addition to the gravitational wave data analysis toolkit. They may be used to extract signals from noise and to infer physical parameters if the data are in good enough agreement with the morphology of the dictionary atoms.

In this paper, we show that a rigidly rotating string can extract the rotational energy from a rotating black hole. We consider Nambu-Goto strings stationary with respect to a corotating Killing vector with an uniform angular velocity $\omega$ in the Kerr spacetime. We show that a necessary condition of the energy-extraction process is that an effective horizon on the string world sheet, which corresponds to the inner light surface, is inside the ergosphere of the Kerr black hole and the angular velocity $\omega$ is less than that of the black hole ${\mathrm{\Omega }}_{\mathrm{h}}$. Furthermore, we discuss global configurations of such strings in both of a slow-rotation limit and the extremal Kerr case.

The MICROSCOPE space mission, launched on April 25, 2016, aims to test the weak equivalence principle (WEP) with a ${10}^{-15}$ precision. Reaching this performance requires an accurate and robust data analysis method, especially since the possible WEP violation signal will be dominated by a strongly colored noise. An important complication is brought by the fact that some values will be missing—therefore, the measured time series will not be strictly regularly sampled. Those missing values induce a spectral leakage that significantly increases the noise in Fourier space, where the WEP violation signal is looked for, thereby complicating scientific returns. Recently, we developed an inpainting algorithm to correct the MICROSCOPE data for missing values. This code has been integrated in the official MICROSCOPE data processing and analysis pipeline because it enables us to significantly measure an equivalence principle violation (EPV) signal in a model-independent way, in the inertial satellite configuration. In this work, we present several improvements to the method that may allow us now to reach the MICROSCOPE requirements for both inertial and spin satellite configurations. The main improvement has been obtained using a prior on the power spectrum of the colored noise that can be directly derived from the incomplete data. We show that after reconstructing missing values with this new algorithm, a least-squares fit may allow us to significantly measure an EPV signal with a $0.96\times {10}^{-15}$ precision in the inertial mode and $1.20\times {10}^{-15}$ precision in the spin mode. Although, the inpainting method presented in this paper has been optimized to the MICROSCOPE data, it remains sufficiently general to be used in the general context of missing data in time series dominated by an unknown colored noise. The improved inpainting software, called inpainting for colored-noise dominated signals, is freely available at http://www.cosmostat.org/software/icon.

We investigate the properties of strange quark matter (SQM) and quark stars (QSs) in the framework of SU(3) Nambu–Jona-Lasinio (NJL) model with two types of vector interactions under strong magnetic fields: (1) the flavor-dependent repulsion among $u$, $d$, and $s$ quarks with the coupling constant $G_V$, and (2) the universal repulsion and the vector-isovector interaction with the coupling constants $g_V$ and $G_{IV}$. The effects of the two types of vector interactions on the constituent quark mass, vacuum quark mass, quark chemical potential, and quark fraction in SQM under strong magnetic fields are studied, and the results indicate that these physical quantities for SQM are all sensitive to the two types of vector interactions in NJL model under magnetic fields. Using a density-dependent magnetic field profile which is introduced to describe the magnetic field strength distribution inside the magnetars, we calculate the properties of spherical QSs by using two extreme cases for the orientation of the magnetic field inside the stars, i.e., the radial orientation in which the magnetic fields are along the radial direction in stars, and the transverse orientation in which the magnetic fields are randomly oriented in the plane which is perpendicular to the radial direction. Our results indicate that the maximum mass of QSs may dependent on both the strength distribution and the orientation of the magnetic fields inside QSs by using SU(3) NJL model.

Over a handful of rotation periods, dynamical processes in barred galaxies induce nonaxisymmetric structure in dark matter halos. Using $n$-body simulations of a Milky Way–like barred galaxy, we identify both a trapped dark matter component, a shadow bar, and a strong response wake in the dark matter distribution that affects the predicted dark matter detection rates for current experiments. The presence of a baryonic disk, together with well-known dynamical processes (e.g. spiral structure and bar instabilities), increases the dark matter density in the disk plane. We find that the magnitude of the combined stellar and shadow bar evolution, when isolated from the effect of the axisymmetric gravitational potential of the disk, accounts for $>30\%$ of this overall increase in disk-plane density. This is significantly larger than that of previously claimed deviations from the standard halo model. The dark matter density and kinematic wakes driven by the Milky Way bar increase the detectability of dark matter overall, especially for the experiments with higher $v_{\min }$. These astrophysical features increase the detection rate by more than a factor of 2 when compared to the standard halo model and by a factor of 10 for experiments with high minimum recoil energy thresholds. These same features increase (decrease) the annual modulation for low (high) minimum recoil energy experiments. We present physical arguments for why these dynamics are generic for barred galaxies such as the Milky Way rather than contingent on a specific galaxy model.

A detection of a core-collapse supernova (CCSN) gravitational-wave (GW) signal with an Advanced LIGO and Virgo detector network may allow us to measure astrophysical parameters of the dying massive star. GWs are emitted from deep inside the core, and, as such, they are direct probes of the CCSN explosion mechanism. In this study, we show how we can determine the CCSN explosion mechanism from a GW supernova detection using a combination of principal component analysis and Bayesian model selection. We use simulations of GW signals from CCSN exploding via neutrino-driven convection and rapidly rotating core collapse. Previous studies have shown that the explosion mechanism can be determined using one LIGO detector and simulated Gaussian noise. As real GW detector noise is both nonstationary and non-Gaussian, we use real detector noise from a network of detectors with a sensitivity altered to match the advanced detectors design sensitivity. For the first time, we carry out a careful selection of the number of principal components to enhance our model selection capabilities. We show that with an advanced detector network we can determine if the CCSN explosion mechanism is driven by neutrino convection for sources in our Galaxy and rapidly-rotating core collapse for sources out to the Large Magellanic Cloud.

In this work, we develop a model for Higgs-like composites based on two generations of right-handed neutrinos that condense. We analyze the spontaneous symmetry breaking of the theory with two explicit breakings, setting the different scales of the model and obtaining massive bosons as a result. Finally, we calculate the gravitational wave imprint left by the phase transition associated with the symmetry breaking of a generic potential dictated by the symmetries of the composites.

Motivated by realistic scattering processes of composite systems, we study the dynamics of a two-particle bound system which is scattered at a mirror. We consider two different scenarios: In the first case we assume that only one particle interacts directly with the mirror whereas in the second case both particles are scattered. The coherence between the transmitted and the reflected wave packet is reduced when the internal degree of freedom (the relative coordinate) of the bound system becomes excited. Depending on the particular system-mirror interaction, long-lived resonances can occur.

The cosmological evolution of topological defect networks can broadly be divided into two stages. At early times they are friction dominated due to particle scattering and therefore nonrelativistic and may either be conformally stretched or evolve in the Kibble regime. At late times they are relativistic and evolve in the well-known linear scaling regime. In this work we show that a sufficiently large Hubble damping (that is a sufficiently fast expansion rate) leads to a linear scaling regime where the network is nonrelativistic. This is therefore another realization of a Kibble scaling regime and also has a conformal stretching regime counterpart which we characterize for the first time. We describe these regimes using analytic arguments in the context of the velocity-dependent one-scale model, and we confirm them using high-resolution $4096^3$ field-theory simulations of domain wall networks. We also use these simulations to improve the calibration of this analytic model for the case of domain walls.

In this paper we investigate the phase structure of a ($1+1$)-dimensional schematic quark model with four-quark interaction and in the presence of baryon (${\mu }_B$), isospin (${\mu }_I$) and chiral isospin (${\mu }_{I5}$) chemical potentials. It is established that in the large-$N_c$ limit ($N_c$ is the number of colored quarks) there exists a duality correspondence between the chiral symmetry breaking phase and the charged pion condensation (PC) one. The role and influence of this property on the phase structure of the model are studied. Moreover, it is shown that the chemical potential ${\mu }_{I5}$ promotes the appearance of the charged PC phase with nonzero baryon density.

We develop a seesaw model for neutrino masses and mixing with an $S_3\times Z_3$ symmetry. It involves an interplay of type-I and type-II seesaw contributions of which the former is subdominant. The $S_3\times Z_3$ quantum numbers of the fermion and scalar fields are chosen such that the type-II seesaw generates a mass matrix which incorporates the atmospheric mass splitting and sets ${\theta }_{23}=\pi /4$. The solar splitting and ${\theta }_{13}$ are absent, while the third mixing angle can achieve any value, ${\theta }_{12}^0$. Specific choices of ${\theta }_{12}^0$ are of interest, e.g., 35.3° (tribimaximal), 45.0° (bimaximal), 31.7° (golden ratio), and 0° (no solar mixing). The role of the type-I seesaw is to nudge all the above into the range indicated by the data. The model results in novel interrelationships between these quantities due to their common origin, making it readily falsifiable. For example, normal (inverted) ordering is associated with ${\theta }_{23}$ in the first (second) octant. $CP$ violation is controlled by phases in the right-handed neutrino Majorana mass matrix, $M_{\nu R}$. In their absence, only normal ordering is admissible. When $M_{\nu R}$ is complex, the Dirac $CP$ phase, $\delta$, can be large, i.e., $\sim \pm \pi /2$, and inverted ordering is also allowed. The preliminary results from T2K and NOVA which favor normal ordering and $\delta \sim -\pi /2$ are indicative, in this model, of a lightest neutrino mass of 0.05 eV or more.

We demonstrate that the condition of vacuum stability severely restricts scenarios with fermionic WIMP dark matter in the scotogenic model. The sizable Yukawa couplings that are required to satisfy the dark matter constraint via thermal freeze-out in these scenarios tend to destabilize the vacuum at scales below that of the heaviest singlet fermion, rendering the model inconsistent from a theoretical point of view. By means of a scan over the parameter space, we study the impact of these renormalization group effects on the viable regions of this model. Our analysis shows that a fraction of more than 90% of the points compatible with all known experimental constraints—including neutrino masses, the dark matter density, and lepton flavor violation—is actually inconsistent.

There exist well-motivated models of particle dark matter which predominantly scatter inelastically off nuclei in direct detection experiments. This inelastic transition causes the dark matter to upscatter in terrestrial experiments into an excited state up to 550 keV heavier than the dark matter itself. An inelastic transition of this size is highly suppressed by both kinematics and nuclear form factors. In this paper, we extend previous studies of inelastic dark matter to determine the present bounds on the scattering cross section and the prospects for improvements in sensitivity. Three scenarios provide illustrative examples: nearly pure Higgsino supersymmetric dark matter, magnetic inelastic dark matter, and inelastic models with dark photon exchange. We determine the elastic scattering rate (through loop diagrams involving the heavy state) as well as verify that exothermic transitions are negligible (in the parameter space we consider). Presently, the strongest bounds on the cross section are from xenon at LUX-PandaX (when the mass splitting $\delta \lesssim 160\mathrm{keV}$), iodine at PICO (when $160\lesssim \delta \lesssim 300\mathrm{keV}$), and tungsten at CRESST (when $\delta \gtrsim 300\mathrm{keV}$). Amusingly, once $\delta \gtrsim 200\mathrm{keV}$, weak scale (and larger) dark matter–nucleon scattering cross sections are allowed. The relative competitiveness of these diverse experiments is governed by the upper bound on the recoil energies employed by each experiment, as well as strong sensitivity to the mass of the heaviest element in the detector. Several implications, including sizable recoil energy-dependent annual modulation and improvements for future experiments, are discussed. We show that the xenon experiments can improve on the PICO results, if they were to analyze their existing data over a larger range of recoil energies, i.e., 20–500 keV Intriguingly, CRESST has reported several events in the recoil energy range 45–100 keV that, if interpreted as dark matter scattering, is compatible with $\delta \sim 200\mathrm{keV}$ and an approximately weak scale cross section. Future data from PICO and CRESST can test this speculation, while xenon experiments could verify or refute this upon analyzing their higher energy recoil data.

The type II seesaw model requires that its scalar doublet $H$ and triplet $\mathrm{\Delta }$ get specific patterns of vacuum expectation values $⟨H⟩\propto (0,1{)}^T$ and $⟨\mathrm{\Delta }⟩\propto (0,0,1{)}^T$ to accommodate neutrino masses. However, other types of minima could also exist in the scalar potential, which may strongly contradict to experimental observations. This paper studies when the minimum at $⟨H⟩\propto (0,1{)}^T$ and $⟨\mathrm{\Delta }⟩\propto (0,0,1{)}^T$ will be global and finds the necessary and sufficient condition for that, assuming that the lepton number violating term $H^2\mathrm{\Delta }$ in the potential is perturbatively small.

The rare decays of a kaon into a pion and a charged lepton/antilepton pair proceed via a flavor changing neutral current and therefore may only be induced beyond tree level in the Standard Model. This natural suppression makes these decays sensitive to the effects of potential new physics. The $CP$-conserving $K\to \pi {\ell }^{+}{\ell }^{-}$ decay channels however are dominated by a single-photon exchange; this involves a sizeable long-distance hadronic contribution which represents the current major source of theoretical uncertainty. Here we outline our methodology for the computation of the long-distance contributions to these rare decay amplitudes using lattice QCD and present the numerical results of the first exploratory studies of these decays in which all but the disconnected diagrams are evaluated. The domain wall fermion ensembles of the RBC and UKQCD Collaborations are used, with a pion mass of $M_{\pi }\sim 430\mathrm{MeV}$ and a kaon mass of $M_K\sim 625\mathrm{MeV}$. In particular we determine the form factor, $V(z)$, of the $K^{+}\to {\pi }^{+}{\ell }^{+}{\ell }^{-}$ decay from the lattice at small values of $z=q^2/M_K^2$, obtaining $V(z)=1.37(36)$, 0.68(39), 0.96(64) for the three values of $z=-0.5594(12)$, $-1.0530(34)$, $-1.4653(82)$ respectively.

The complex Langevin method is a promising approach to the complex-action problem based on a fictitious time evolution of complexified dynamical variables under the influence of a Gaussian noise. Although it is known to have a restricted range of applicability, the use of gauge cooling made it applicable to various interesting cases including finite density QCD in certain parameter regions. In this paper we revisit the argument for justification of the method. In particular, we point out a subtlety in the use of time-evolved observables, which play a crucial role in the previous argument. This requires that the probability of the drift term should fall off exponentially or faster at large magnitude. We argue that this is actually a necessary and sufficient condition for the method to be justified. Using two simple examples, we show that our condition tells us clearly whether the results obtained by the method are trustable or not. We also discuss a new possibility for the gauge cooling, which can reduce the magnitude of the drift term directly.