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the laser interferometer gravitational wave observatory (ligo) has been directly detecting gravitational waves from compact binary mergers since 2015. we report on the first use of squeezed vacuum states in the direct measurement of gravitational waves with the advanced ligo h1 and l1 detectors. this achievement is the culmination of decades of research to implement squeezed states in gravitational-wave detectors. during the ongoing o3 observation run, squeezed states are improving the sensitivity of the ligo interferometers to signals above 50 hz by up to 3 db, thereby increasing the expected detection rate by 40% (h1) and 50% (l1). | quantum-enhanced advanced ligo detectors in the era of gravitational-wave astronomy |
the global network of gravitational-wave observatories now includes five detectors, namely ligo hanford, ligo livingston, virgo, kagra, and geo 600. these detectors collected data during their third observing run, o3, composed of three phases: o3a starting in 2019 april and lasting six months, o3b starting in 2019 november and lasting five months, and o3gk starting in 2020 april and lasting two weeks. in this paper we describe these data and various other science products that can be freely accessed through the gravitational wave open science center at https://gwosc.org. the main data set, consisting of the gravitational-wave strain time series that contains the astrophysical signals, is released together with supporting data useful for their analysis and documentation, tutorials, as well as analysis software packages. | open data from the third observing run of ligo, virgo, kagra, and geo |
we propose an optimization procedure for euclidean path-integrals that evaluate cft wave functionals in arbitrary dimensions. the optimization is performed by minimizing certain functional, which can be interpreted as a measure of computational complexity, with respect to background metrics for the path-integrals. in two dimensional cfts, this functional is given by the liouville action. we also formulate the optimization for higher dimensional cfts and, in various examples, find that the optimized hyperbolic metrics coincide with the time slices of expected gravity duals. moreover, if we optimize a reduced density matrix, the geometry becomes two copies of the entanglement wedge and reproduces the holographic entanglement entropy. our approach resembles a continuous tensor network renormalization and provides a concrete realization of the proposed interpretation of ads/cft as tensor networks. the present paper is an extended version of our earlier report arxiv:1703.00456 and includes many new results such as evaluations of complexity functionals, energy stress tensor, higher dimensional extensions and time evolutions of thermofield double states. | liouville action as path-integral complexity: from continuous tensor networks to ads/cft |
internal gravity waves, the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in the ocean. because of their strong vertical and horizontal currents, and the turbulent mixing caused by their breaking, they affect a panoply of ocean processes, such as the supply of nutrients for photosynthesis, sediment and pollutant transport and acoustic transmission; they also pose hazards for man-made structures in the ocean. generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking, making it challenging to observe them and to include them in numerical climate models, which are sensitive to their effects. for over a decade, studies have targeted the south china sea, where the oceans' most powerful known internal waves are generated in the luzon strait and steepen dramatically as they propagate west. confusion has persisted regarding their mechanism of generation, variability and energy budget, however, owing to the lack of in situ data from the luzon strait, where extreme flow conditions make measurements difficult. here we use new observations and numerical models to (1) show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena, (2) reveal the existence of >200-metre-high breaking internal waves in the region of generation that give rise to turbulence levels >10,000 times that in the open ocean, (3) determine that the kuroshio western boundary current noticeably refracts the internal wave field emanating from the luzon strait, and (4) demonstrate a factor-of-two agreement between modelled and observed energy fluxes, which allows us to produce an observationally supported energy budget of the region. together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions. | the formation and fate of internal waves in the south china sea |
magis-100 is a next-generation quantum sensor under construction at fermilab that aims to explore fundamental physics with atom interferometry over a 100 m baseline. this novel detector will search for ultralight dark matter, test quantum mechanics in new regimes, and serve as a technology pathfinder for future gravitational wave detectors in a previously unexplored frequency band. it combines techniques demonstrated in state-of-the-art 10-meter-scale atom interferometers with the latest technological advances of the world's best atomic clocks. magis-100 will provide a development platform for a future kilometer-scale detector that would be sufficiently sensitive to detect gravitational waves from known sources. here we present the science case for the magis concept, review the operating principles of the detector, describe the instrument design, and study the detector systematics. | matter-wave atomic gradiometer interferometric sensor (magis-100) |
according to quantum theory the energy exchange between physical systems is quantized. as a direct consequence, measurement sensitivities are fundamentally limited by quantization noise, or just 'quantum noise' in short. furthermore, heisenberg's uncertainty principle demands measurement back-action for some observables of a system if they are measured repeatedly. in both respects, squeezed states are of high interest since they show a 'squeezed' uncertainty, which can be used to improve the sensitivity of measurement devices beyond the usual quantum noise limits including those impacted by quantum back-action noise. squeezed states of light can be produced with nonlinear optics, and a large variety of proof-of-principle experiments were performed in past decades. as an actual application, squeezed light has now been used for several years to improve the measurement sensitivity of geo 600 - a laser interferometer built for the detection of gravitational waves. given this success, squeezed light is likely to significantly contribute to the new field of gravitational-wave astronomy. this review revisits the concept of squeezed states and two-mode squeezed states of light, with a focus on experimental observations. the distinct properties of squeezed states displayed in quadrature phase-space as well as in the photon number representation are described. the role of the light's quantum noise in laser interferometers is summarized and the actual application of squeezed states in these measurement devices is reviewed. | squeezed states of light and their applications in laser interferometers |
state-of-the-art atomic clocks are based on the precise detection of the energy difference between two atomic levels, which is measured in terms of the quantum phase accumulated over a given time interval1-4. the stability of optical-lattice clocks (olcs) is limited both by the interrupted interrogation of the atomic system by the local-oscillator laser (dick noise5) and by the standard quantum limit (sql) that arises from the quantum noise associated with discrete measurement outcomes. although schemes for removing the dick noise have been recently proposed and implemented4,6-8, performance beyond the sql by engineering quantum correlations (entanglement) between atoms9-20 has been demonstrated only in proof-of-principle experiments with microwave clocks of limited stability. the generation of entanglement on an optical-clock transition and operation of an olc beyond the sql represent important goals in quantum metrology, but have not yet been demonstrated experimentally16. here we report the creation of a many-atom entangled state on an olc transition, and use it to demonstrate a ramsey sequence with an allan deviation below the sql after subtraction of the local-oscillator noise. we achieve a metrological gain of 4 .4-0.4 +0 .6? decibels over the sql by using an ensemble consisting of a few hundred ytterbium-171 atoms, corresponding to a reduction of the averaging time by a factor of 2.8 ± 0.3. our results are currently limited by the phase noise of the local oscillator and dick noise, but demonstrate the possible performance improvement in state-of-the-art olcs1-4 through the use of entanglement. this will enable further advances in timekeeping precision and accuracy, with many scientific and technological applications, including precision tests of the fundamental laws of physics21-23, geodesy24-26 and gravitational-wave detection27. | entanglement on an optical atomic-clock transition |
we give a detailed treatment of electromagnetic signals generated by gravitational waves (gws) in resonant cavity experiments. our investigation corrects and builds upon previous studies by carefully accounting for the gauge dependence of relevant quantities. we work in a preferred frame for the laboratory, the proper detector frame, and show how to resum short-wavelength effects to provide analytic results that are exact for gws of arbitrary wavelength. this formalism allows us to firmly establish that, contrary to previous claims, cavity experiments designed for the detection of axion dark matter only need to reanalyze existing data to search for high-frequency gws with strains as small as h ∼10-22- 10-21 . we also argue that directional detection is possible in principle using readout of multiple cavity modes. further improvements in sensitivity are expected with cutting-edge advances in superconducting cavity technology. | detecting high-frequency gravitational waves with microwave cavities |
litebird is a candidate satellite for a strategic large mission of jaxa. with its expected launch in the middle of the 2020s with a h3 rocket, litebird plans to map the polarization of the cosmic microwave background radiation over the full sky with unprecedented precision. the full success of litebird is to achieve δ r < 0.001, where δ r is the total error on the tensor-to-scalar ratio r. the required angular coverage corresponds to 2 ≤ ℓ ≤ 200, where ℓ is the multipole moment. this allows us to test well-motivated cosmic inflation models. full-sky surveys for 3 years at a lagrangian point l2 will be carried out for 15 frequency bands between 34 and 448 ghz with two telescopes to achieve the total sensitivity of 2.5 μ k arcmin with a typical angular resolution of 0.5° at 150 ghz. each telescope is equipped with a half-wave plate system for polarization signal modulation and a focal plane filled with polarization-sensitive tes bolometers. a cryogenic system provides a 100 mk base temperature for the focal planes and 2 k and 5 k stages for optical components. | litebird: a satellite for the studies of b-mode polarization and inflation from cosmic background radiation detection |
the global network of gravitational-wave detectors has completed three observing runs with ~50 detections of merging compact binaries. a third ligo detector, with comparable astrophysical reach, is to be built in india (ligo-aundha) and expected to be operational during the latter part of this decade. such additions to the network increase the number of baselines and the network snr of gw events. these enhancements help improve the sky-localization of those events. multiple detectors simultaneously in operation will also increase the baseline duty factor, thereby, leading to an improvement in the detection rates and, hence, the completeness of surveys. in this paper, we quantify the improvements due to the expansion of the ligo global network in the precision with which source properties will be measured. we also present examples of how this expansion will give a boost to tests of fundamental physics. | the science case for ligo-india |
in this paper, which is of programmatic rather than quantitative nature, we aim to further delineate and sharpen the future potential of the lisa mission in the area of fundamental physics. given the very broad range of topics that might be relevant to lisa,we present here a sample of what we view as particularly promising fundamental physics directions. we organize these directions through a "science-first" approach that allows us to classify how lisa data can inform theoretical physics in a variety of areas. for each of these theoretical physics classes, we identify the sources that are currently expected to provide the principal contribution to our knowledge, and the areas that need further development. the classification presented here should not be thought of as cast in stone, but rather as a fluid framework that is amenable to change with the flow of new insights in theoretical physics. | prospects for fundamental physics with lisa |
owing to the low-gravity conditions in space, space-borne laboratories enable experiments with extended free-fall times. because bose-einstein condensates have an extremely low expansion energy, space-borne atom interferometers based on bose-einstein condensation have the potential to have much greater sensitivity to inertial forces than do similar ground-based interferometers. on 23 january 2017, as part of the sounding-rocket mission maius-1, we created bose-einstein condensates in space and conducted 110 experiments central to matter-wave interferometry, including laser cooling and trapping of atoms in the presence of the large accelerations experienced during launch. here we report on experiments conducted during the six minutes of in-space flight in which we studied the phase transition from a thermal ensemble to a bose-einstein condensate and the collective dynamics of the resulting condensate. our results provide insights into conducting cold-atom experiments in space, such as precision interferometry, and pave the way to miniaturizing cold-atom and photon-based quantum information concepts for satellite-based implementation. in addition, space-borne bose-einstein condensation opens up the possibility of quantum gas experiments in low-gravity conditions1,2. | space-borne bose-einstein condensation for precision interferometry |
the recent detections of gravitational waves (gws) reported by the ligo and virgo collaborations have made a significant impact on physics and astronomy. a global network of gw detectors will play a key role in uncovering the unknown nature of the sources in coordinated observations with astronomical telescopes and detectors. here we introduce kagra, a new gw detector with two 3 km baseline arms arranged in an `l' shape. kagra's design is similar to the second generations of advanced ligo and advanced virgo, but it will be operating at cryogenic temperatures with sapphire mirrors. this low-temperature feature is advantageous for improving the sensitivity around 100 hz and is considered to be an important feature for the third-generation gw detector concept (for example, the einstein telescope of europe or the cosmic explorer of the united states). hence, kagra is often called a 2.5-generation gw detector based on laser interferometry. kagra's first observation run is scheduled in late 2019, aiming to join the third observation run of the advanced ligo-virgo network. when operating along with the existing gw detectors, kagra will be helpful in locating gw sources more accurately and determining the source parameters with higher precision, providing information for follow-up observations of gw trigger candidates. | kagra: 2.5 generation interferometric gravitational wave detector |
we present a gauge-invariant framework for bubble nucleation in theories with radiative symmetry breaking at high temperature. as a procedure, this perturbative framework establishes a practical, gauge-invariant computation of the leading order nucleation rate, based on a consistent power counting in the high-temperature expansion. in model building and particle phenomenology, this framework has applications such as the computation of the bubble nucleation temperature and the rate for electroweak baryogenesis and gravitational wave signals from cosmic phase transitions. | nucleation at finite temperature: a gauge-invariant perturbative framework |
the recent observation of the hellings-downs angular correlation by nanograv and other pta experiments indicates the presence of stochastic gravitational wave background in the frequency $\sim 1-10$ nhz. in the clockwork axion model, the network of cosmic strings and domain walls forms after the spontaneous symmetry breaking and can survive until the qcd phase transition. the qcd axion potential induced by the qcd phase transition can serve as an energy bias, which leads to the annihilation of the domain walls. in ref.~\cite{chiang:2020aui}, we have shown that the gws radiated during the annihilation of the domain walls formed at the peccei-quinn symmetry breaking scale $f\simeq 200$~tev can give rise to the potential signal in the nanograv 12.5-year data. in this work, we show that both the amplitude and the spectrum shape of the gw signals from the domain walls annihilation at a scale $f=1.69_{-0.34}^{+0.36}\times 100$~tev can well account for the nanograv 15-year results. | nano-hertz stochastic gravitational wave background from domain wall annihilation |
we study a minimal extension of the standard model by introducing three right-handed neutrinos and a new scotogenic scalar doublet, in which the mass splittings between neutral and charged components are responsible for the w-boson mass newly measured by the cdf collaboration. this model can not only generate non-vanishing majorana neutrino masses via the interaction of right-handed neutrinos and scotogenic scalars, but also explain the universe's missing matter in the form of fimp dark matter. we also study the influence of the mass splitting on the first order electroweak phase transition, and find that it can further enhance the transition strength and thus induce gravitational waves during the phase transition, which may be detected in the forthcoming detectors such as u-decigo. | correlating gravitational waves with w-boson mass, fimp dark matter, and majorana seesaw mechanism |
we present a new infinite class of gravitational observables in asymptotically anti-de sitter space living on codimension-one slices of the geometry, the most famous of which is the volume of the maximal slice. we show that these observables display universal features for the thermofield-double state: they grow linearly in time at late times and reproduce the switchback effect in shock wave geometries. we argue that any member of this class of observables is an equally viable candidate as the extremal volume for a gravitational dual of complexity. | does complexity equal anything? |
for computing thermodynamics of the electroweak phase transition, we discuss a minimal approach that reconciles both gauge invariance and thermal resummation. such a minimal setup consists of a two-loop dimensional reduction to three-dimensional effective theory, a one-loop computation of the effective potential and its expansion around the leading-order minima within the effective theory. this approach is tractable and provides formulae for resummation that are arguably no more complicated than those that appear in standard techniques ubiquitous in the literature. in particular, we implement renormalisation group improvement related to the hard thermal scale. despite its generic nature, we present this approach for the complex singlet extension of the standard model which has interesting prospects for high energy collider phenomenology and dark matter predictions. the presented expressions can be used in future studies of phase transition thermodynamics and gravitational wave production in this model. | combining thermal resummation and gauge invariance for electroweak phase transition |
after their successful first observing run (september 12, 2015 - january 12, 2016), the advanced ligo detectors were upgraded to increase their sensitivity for the second observing run (november 30, 2016 - august 26, 2017). the advanced virgo detector joined the second observing run on august 1, 2017. we discuss the updates that happened during this period in the gstlal-based inspiral pipeline, which is used to detect gravitational waves from the coalescence of compact binaries both in low latency and an offline configuration. these updates include deployment of a zero-latency whitening filter to reduce the over-all latency of the pipeline by up to 32 seconds, incorporation of the virgo data stream in the analysis, introduction of a single-detector search to analyze data from the periods when only one of the detectors is running, addition of new parameters to the likelihood ratio ranking statistic, increase in the parameter space of the search, and introduction of a template mass-dependent glitch-excision thresholding method. | the gstlal search analysis methods for compact binary mergers in advanced ligo's second and advanced virgo's first observing runs |
the quantum superposition principle allows massive particles to be delocalized over distant positions. though quantum mechanics has proved adept at describing the microscopic world, quantum superposition runs counter to intuitive conceptions of reality and locality when extended to the macroscopic scale, as exemplified by the thought experiment of schrödinger’s cat. matter-wave interferometers, which split and recombine wave packets in order to observe interference, provide a way to probe the superposition principle on macroscopic scales and explore the transition to classical physics. in such experiments, large wave-packet separation is impeded by the need for long interaction times and large momentum beam splitters, which cause susceptibility to dephasing and decoherence. here we use light-pulse atom interferometry to realize quantum interference with wave packets separated by up to 54 centimetres on a timescale of 1 second. these results push quantum superposition into a new macroscopic regime, demonstrating that quantum superposition remains possible at the distances and timescales of everyday life. the sub-nanokelvin temperatures of the atoms and a compensation of transverse optical forces enable a large separation while maintaining an interference contrast of 28 per cent. in addition to testing the superposition principle in a new regime, large quantum superposition states are vital to exploring gravity with atom interferometers in greater detail. we anticipate that these states could be used to increase sensitivity in tests of the equivalence principle, measure the gravitational aharonov-bohm effect, and eventually detect gravitational waves and phase shifts associated with general relativity. | quantum superposition at the half-metre scale |
non-classical states of light find applications in enhancing the performance of optical interferometric experiments, with notable example of gravitational wave-detectors. still, the presence of decoherence hinders significantly the performance of quantum-enhanced protocols. in this review, we summarize the developments of quantum metrology with particular focus on optical interferometry and derive fundamental bounds on achievable quantum-enhanced precision in optical interferometry taking into account the most relevant decoherence processes including: phase diffusion, losses and imperfect interferometric visibility. we introduce all the necessary tools of quantum optics as well as quantum estimation theory required to derive the bounds. we also discuss the practical attainability of the bounds derived and stress in particular that the techniques of quantum-enhanced interferometry which are being implemented in modern gravitational wave detectors are close to the optimal ones. | quantum limits in optical interferometry |
we extend the boundary-to-bound (b2b) correspondence to incorporate radiative as well as conservative radiation-reaction effects. we start by deriving a map between the total change in observables due to gravitational wave emission during hyperbolic-like motion and in one period of an elliptic-like orbit, which is valid in the adiabatic expansion for non-spinning as well as aligned-spin configurations. we also discuss the inverse problem of extracting the associated fluxes from scattering data. afterwards we demonstrate, to all orders in the post-minkowskian expansion, the link between the radiated energy and the ultraviolet pole in the radial action in dimensional regularization due to tail effects. this implies, as expected, that the b2b correspondence for the conservative sector remains unchanged for local-in-time radiation-reaction tail effects with generic orbits. as a side product, this allows us to read off the energy flux from the associated pole in the tail hamiltonian. we show that the b2b map also holds for non-local-in-time terms, but only in the large-eccentricity limit. remarkably, we find that all of the trademark logarithmic contributions to the radial action map unscathed between generic unbound and bound motion. however, unlike logarithms, other terms due to non-local effects do not transition smoothly to quasi-circular orbits. we conclude with a discussion on these non-local pieces. several checks of the b2b dictionary are displayed using state-of-the-art knowledge in post-newtonian/minkowskian theory. | from boundary data to bound states. part iii. radiative effects |
sparse seismic instrumentation in the oceans limits our understanding of deep earth dynamics and submarine earthquakes. distributed acoustic sensing (das), an emerging technology that converts optical fiber to seismic sensors, allows us to leverage pre-existing submarine telecommunication cables for seismic monitoring. here we report observations of microseism, local surface gravity waves, and a teleseismic earthquake along a 4192-sensor ocean-bottom das array offshore belgium. we observe in-situ how opposing groups of ocean surface gravity waves generate double-frequency seismic scholte waves, as described by the longuet-higgins theory of microseism generation. we also extract p- and s-wave phases from the 2018-08-19 mw8.2 ? fiji deep earthquake in the 0.01-1 hz frequency band, though waveform fidelity is low at high frequencies. these results suggest significant potential of das in next-generation submarine seismic networks. | distributed sensing of microseisms and teleseisms with submarine dark fibers |
the laser interferometer space antenna (lisa) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. in this white paper, the fundamental physics working group of the lisa consortium summarizes the current topics in fundamental physics where lisa observations of gravitational waves can be expected to provide key input. we provide the briefest of reviews to then delineate avenues for future research directions and to discuss connections between this working group, other working groups and the consortium work package teams. these connections must be developed for lisa to live up to its science potential in these areas. | new horizons for fundamental physics with lisa |
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 ∼3 mhz - 10 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. | gravitational wave detection with optical lattice atomic clocks |
we propose a new approach to the solution of the wave propagation and full waveform inversions (fwis) based on a recent advance in deep learning called physics-informed neural networks (pinns). in this study, we present an algorithm for pinns applied to the acoustic wave equation and test the method with both forward models and fwi case studies. these synthetic case studies are designed to explore the ability of pinns to handle varying degrees of structural complexity using both teleseismic plane waves and seismic point sources. pinns' meshless formalism allows for a flexible implementation of the wave equation and different types of boundary conditions. for instance, our models demonstrate that pinn automatically satisfies absorbing boundary conditions, a serious computational challenge for common wave propagation solvers. furthermore, a priori knowledge of the subsurface structure can be seamlessly encoded in pinns' formulation. we find that the current state-of-the-art pinns provide good results for the forward model, even though spectral element or finite difference methods are more efficient and accurate. more importantly, our results demonstrate that pinns yield excellent results for inversions on all cases considered and with limited computational complexity. we discuss the current limitations of the method with complex velocity models as well as strategies to overcome these challenges. using pinns as a geophysical inversion solver offers exciting perspectives, not only for the full waveform seismic inversions, but also when dealing with other geophysical datasets (e.g., mt, gravity) as well as joint inversions because of its robust framework and simple implementation. | physics-informed neural networks (pinns) for wave propagation and full waveform inversions |
in brown et al. [prx quantum, tba, tba (2023)], we discuss how holographic quantum gravity may be simulated using quantum devices and we give a specific proposal—teleportation by size and the phenomenon of size winding. here, we elaborate on what it means to do quantum gravity in the lab and how size winding connects to bulk gravitational physics and traversable wormholes. perfect size winding is a remarkable fine-grained property of the size wave function of an operator; we show from a bulk calculation that this property must hold for quantum systems with a nearly ads 2 bulk. we then examine in detail teleportation by size in three systems—the sachdev-ye-kitaev model, random matrices, and spin chains—and discuss prospects for realizing these phenomena in near-term quantum devices. | quantum gravity in the lab. ii. teleportation by size and traversable wormholes |
using data from more than 2000 seismic stations from multiple networks arrayed throughout china (cearray, china array, necess, passcal, gsn) and surrounding regions (korean seismic network, f-net, knet), we perform ambient noise rayleigh wave tomography across the entire region and earthquake tomography across parts of south china and northeast china. we produce isotropic rayleigh wave group and phase speed maps with uncertainty estimates from 8 to 50 s period across the entire region of study, and extend them to 70 s period where earthquake tomography is performed. maps of azimuthal anisotropy are estimated simultaneously to minimize anisotropic bias in the isotropic maps, but are not discussed here. the 3d model is produced using a bayesian monte carlo formalism covering all of china, extending eastwards through the korean peninsula, into the marginal seas, to japan. we define the final model as the mean and standard deviation of the posterior distribution at each location on a 0.5° × 0.5° grid from the surface to 150 km depth. surface wave dispersion data do not strongly constrain internal interfaces, but shear wave speeds between the discontinuities in the crystalline crust and uppermost mantle are well determined. we design the resulting model as a reference model, which is intended to be useful to other researchers as a starting model, to predict seismic wave fields and observables and to predict other types of data (e.g. topography, gravity). the model and the data on which it is based are available for download. in addition, the model displays a great variety and considerable richness of geological and tectonic features in the crust and in the uppermost mantle deserving of further focus and continued interpretation. | a seismic reference model for the crust and uppermost mantle beneath china from surface wave dispersion |
in part 2 of this two-part paper, documentation is provided of key aspects of a version of the am4.0/lm4.0 atmosphere/land model that will serve as a base for a new set of climate and earth system models (cm4 and esm4) under development at noaa's geophysical fluid dynamics laboratory (gfdl). the quality of the simulation in amip (atmospheric model intercomparison project) mode has been provided in part 1. part 2 provides documentation of key components and some sensitivities to choices of model formulation and values of parameters, highlighting the convection parameterization and orographic gravity wave drag. the approach taken to tune the model's clouds to observations is a particular focal point. care is taken to describe the extent to which aerosol effective forcing and cess sensitivity have been tuned through the model development process, both of which are relevant to the ability of the model to simulate the evolution of temperatures over the last century when coupled to an ocean model. | the gfdl global atmosphere and land model am4.0/lm4.0: 2. model description, sensitivity studies, and tuning strategies |
we describe the formalism to compute gravitational-wave observables for compact binaries via the effective field theory framework in combination with modern tools from collider physics. we put particular emphasis on solving the `multi-loop' integration problem via the methodology of differential equations and expansion by regions. this allows us to bootstrap the two-body relativistic dynamics in the post-minkowskian (pm) expansion from boundary data evaluated in the near-static (soft) limit. we illustrate the procedure with the derivation of the total spacetime impulse in the scattering of non-spinning bodies to 4pm (three-loop) order, i.e. o (g4), including conservative and dissipative effects. | bootstrapping the relativistic two-body problem |
the measurement of minuscule forces and displacements with ever greater precision is inhibited by the heisenberg uncertainty principle, which imposes a limit to the precision with which the position of an object can be measured continuously, known as the standard quantum limit1-4. when light is used as the probe, the standard quantum limit arises from the balance between the uncertainties of the photon radiation pressure applied to the object and of the photon number in the photoelectric detection. the only way to surpass the standard quantum limit is by introducing correlations between the position/momentum uncertainty of the object and the photon number/phase uncertainty of the light that it reflects5. here we confirm experimentally the theoretical prediction5 that this type of quantum correlation is naturally produced in the laser interferometer gravitational-wave observatory (ligo). we characterize and compare noise spectra taken without squeezing and with squeezed vacuum states injected at varying quadrature angles. after subtracting classical noise, our measurements show that the quantum mechanical uncertainties in the phases of the 200-kilowatt laser beams and in the positions of the 40-kilogram mirrors of the advanced ligo detectors yield a joint quantum uncertainty that is a factor of 1.4 (3 decibels) below the standard quantum limit. we anticipate that the use of quantum correlations will improve not only the observation of gravitational waves, but also more broadly future quantum noise-limited measurements. | quantum correlations between light and the kilogram-mass mirrors of ligo |
spacetime curvature induces tidal forces on the wave function of a single quantum system. using a dual light-pulse atom interferometer, we measure a phase shift associated with such tidal forces. the macroscopic spatial superposition state in each interferometer (extending over 16 cm) acts as a nonlocal probe of the spacetime manifold. additionally, we utilize the dual atom interferometer as a gradiometer for precise gravitational measurements. | phase shift in an atom interferometer due to spacetime curvature across its wave function |
the characterization of the advanced ligo detectors in the second and third observing runs has increased the sensitivity of the instruments, allowing for a higher number of detectable gravitational-wave signals, and provided confirmation of all observed gravitational-wave events. in this work, we present the methods used to characterize the ligo detectors and curate the publicly available datasets, including the ligo strain data and data quality products. we describe the essential role of these datasets in ligo–virgo collaboration analyses of gravitational-waves from both transient and persistent sources and include details on the provenance of these datasets in order to support analyses of ligo data by the broader community. finally, we explain anticipated changes in the role of detector characterization and current efforts to prepare for the high rate of gravitational-wave alerts and events in future observing runs. | ligo detector characterization in the second and third observing runs |
rapid progress in optical atomic clock performance has advanced the frontiers of timekeeping, metrology and quantum science1-3. despite considerable efforts, the instabilities of most optical clocks remain limited by the local oscillator rather than the atoms themselves4,5. here we implement a `multiplexed' one-dimensional optical lattice clock, in which spatially resolved strontium atom ensembles are trapped in the same optical lattice, interrogated simultaneously by a shared clock laser and read-out in parallel. in synchronous ramsey interrogations of ensemble pairs we observe atom-atom coherence times of 26 s, a 270-fold improvement over the measured atom-laser coherence time, demonstrate a relative instability of 9.7 (4 ) ×10−18/√{τ }? (where τ is the averaging time) and reach a relative statistical uncertainty of 8.9 × 10−20 after 3.3 h of averaging. these results demonstrate that applications involving optical clock comparisons need not be limited by the instability of the local oscillator. we further realize a miniaturized clock network consisting of 6 atomic ensembles and 15 simultaneous pairwise comparisons with relative instabilities below 3 ×10−17/√{τ }?, and prepare spatially resolved, heterogeneous ensemble pairs of all four stable strontium isotopes. these results pave the way for multiplexed precision isotope shift measurements, spatially resolved characterization of limiting clock systematics, the development of clock-based gravitational wave and dark matter detectors6-12 and new tests of relativity in the lab13-16. | differential clock comparisons with a multiplexed optical lattice clock |
we review the physics of near-inertial waves (niws) in the ocean and the observations, theory, and models that have provided our present knowledge. niws appear nearly everywhere in the ocean as a spectral peak at and just above the local inertial period f, and the longest vertical wavelengths can propagate at least hundreds of kilometers toward the equator from their source regions; shorter vertical wavelengths do not travel as far and do not contain as much energy, but lead to turbulent mixing owing to their high shear. niws are generated by a variety of mechanisms, including the wind, nonlinear interactions with waves of other frequencies, lee waves over bottom topography, and geostrophic adjustment; the partition among these is not known, although the wind is likely the most important. niws likely interact strongly with mesoscale and submesoscale motions, in ways that are just beginning to be understood. | near-inertial internal gravity waves in the ocean |
we revisit the einstein-gauss-bonnet theory in view of the gw170817 event, which compels that the gravitational wave speed is equal to ct2 = 1 in natural units. we use an alternative approach compared to one previous work of ours, which enables us to express all the slow-roll indices and the observational indices as functions of the scalar field. using our formalism we investigate if the swampland criteria are satisfied for the einstein-gauss-bonnet theory and as we demonstrate, the swampland criteria are satisfied for quite general forms of the potential and the gauss-bonnet coupling function ξ (ϕ), if the slow-roll conditions are assumed to hold true. | swampland implications of gw170817-compatible einstein-gauss-bonnet gravity |
gravity curves space and time. this can lead to proper time differences between freely falling, nonlocal trajectories. a spatial superposition of a massive particle is predicted to be sensitive to this effect. we measure the gravitational phase shift induced in a matter-wave interferometer by a kilogram-scale source mass close to one of the wave packets. deflections of each interferometer arm due to the source mass are independently measured. the phase shift deviates from the deflection-induced phase contribution, as predicted by quantum mechanics. in addition, the observed scaling of the phase shift is consistent with heisenberg’s error-disturbance relation. these results show that gravity creates aharonov-bohm phase shifts analogous to those produced by electromagnetic interactions. | observation of a gravitational aharonov-bohm effect |
we report an improved test of the weak equivalence principle by using a simultaneous 85rb-87rb dual-species atom interferometer. we propose and implement a four-wave double-diffraction raman transition scheme for the interferometer, and demonstrate its ability in suppressing common-mode phase noise of raman lasers after their frequencies and intensity ratios are optimized. the statistical uncertainty of the experimental data for eötvös parameter η is 0.8 ×1 0-8 at 3200 s. with various systematic errors corrected, the final value is η =(2.8 ±3.0 )×1 0-8. the major uncertainty is attributed to the coriolis effect. | test of equivalence principle at 1 0-8 level by a dual-species double-diffraction raman atom interferometer |
mechanical resonators are important components of devices that range from gravitational wave detectors to cellular telephones. they serve as high-performance transducers, sensors and filters by offering low dissipation, tunable coupling to diverse physical systems, and compatibility with a wide range of frequencies, materials and fabrication processes. systems of mechanical resonators typically obey reciprocity, which ensures that the phonon transmission coefficient between any two resonators is independent of the direction of transmission1,2. reciprocity must be broken to realize devices (such as isolators and circulators) that provide one-way propagation of acoustic energy between resonators. such devices are crucial for protecting active elements, mitigating noise and operating full-duplex transceivers. until now, nonreciprocal phononic devices3-11 have not simultaneously combined the features necessary for robust operation: strong nonreciprocity, in situ tunability, compact integration and continuous operation. furthermore, they have been applied only to coherent signals (rather than fluctuations or noise), and have been realized exclusively in travelling-wave systems (rather than resonators). here we describe a scheme that uses the standard cavity-optomechanical interaction to produce robust nonreciprocal coupling between phononic resonators. this scheme provides about 30 decibels of isolation in continuous operation and can be tuned in situ simply via the phases of the drive tones applied to the cavity. in addition, by directly monitoring the dynamics of the resonators we show that this nonreciprocity can control thermal fluctuations, and that this control represents a way to cool phononic resonators. | nonreciprocal control and cooling of phonon modes in an optomechanical system |
quantum metrology has many important applications in science and technology, ranging from frequency spectroscopy to gravitational wave detection. quantum mechanics imposes a fundamental limit on measurement precision, called the heisenberg limit, which can be achieved for noiseless quantum systems, but is not achievable in general for systems subject to noise. here we study how measurement precision can be enhanced through quantum error correction, a general method for protecting a quantum system from the damaging effects of noise. we find a necessary and sufficient condition for achieving the heisenberg limit using quantum probes subject to markovian noise, assuming that noiseless ancilla systems are available, and that fast, accurate quantum processing can be performed. when the sufficient condition is satisfied, a quantum error-correcting code can be constructed that suppresses the noise without obscuring the signal; the optimal code, achieving the best possible precision, can be found by solving a semidefinite program. | achieving the heisenberg limit in quantum metrology using quantum error correction |
measuring gravity from an aircraft or a ship is essential in geodesy, geophysics, mineral and hydrocarbon exploration, and navigation. today, only relative sensors are available for onboard gravimetry. this is a major drawback because of the calibration and drift estimation procedures which lead to important operational constraints. atom interferometry is a promising technology to obtain onboard absolute gravimeter. but, despite high performances obtained in static condition, no precise measurements were reported in dynamic. here, we present absolute gravity measurements from a ship with a sensor based on atom interferometry. despite rough sea conditions, we obtained precision below 10-5 m s-2. the atom gravimeter was also compared with a commercial spring gravimeter and showed better performances. this demonstration opens the way to the next generation of inertial sensors (accelerometer, gyroscope) based on atom interferometry which should provide high-precision absolute measurements from a moving platform. | absolute marine gravimetry with matter-wave interferometry |
the production of a stochastic background of gravitational waves is a fundamental prediction of any cosmological inflationary model. the features of such a signal encode unique information about the physics of the early universe and beyond, thus representing an exciting, powerful window on the origin and evolution of the universe. we review the main mechanisms of gravitational-wave production, ranging from quantum fluctuations of the gravitational field to other mechanisms that can take place during or after inflation. these include e.g. gravitational waves generated as a consequence of extra particle production during inflation, or during the (p)reheating phase. gravitational waves produced in inflation scenarios based on modified gravity theories and second-order gravitational waves are also considered. for each analyzed case, the expected power spectrum is given. we discuss the discriminating power among different models, associated with the validity/violation of the standard consistency relation between tensor-to-scalar ratio r and tensor spectral index nt in light of the prospects for (directly/indirectly) detecting primordial gravitational waves, we give the expected present-day gravitational radiation spectral energy-density, highlighting the main characteristics imprinted by the cosmic thermal history, and we outline the signatures left by gravitational waves on the cosmic microwave background and some imprints in the large-scale structure of the universe. finally, current bounds and prospects of detection for inflationary gravitational waves are summarized. | gravitational waves from inflation |
quasi-biennial oscillations (qbos) in thirteen atmospheric general circulation models forced with both observed and annually repeating sea surface temperatures (ssts) are evaluated. in most models the qbo period is close to, but shorter than, the observed period of 28 months. amplitudes are within ±20% of the observed qbo amplitude at 10 hpa, but typically about half of that observed at lower altitudes (50 and 70 hpa). for almost all models, the oscillation's amplitude profile shows an overall upward shift compared to reanalysis and its meridional extent is too narrow. asymmetry in the duration of eastward and westward phases is reasonably well captured, though not all models replicate the observed slowing of the descending westward shear. westward phases are generally too weak, and most models have an eastward time mean wind bias throughout the depth of the qbo. the intercycle period variability is realistic and in some models is enhanced in the experiment with observed ssts compared to the experiment with repeated annual cycle ssts. mean periods are also sensitive to this difference between ssts, but only when parametrized non-orographic gravity wave (nogw) sources are coupled to tropospheric parameters and not prescribed with a fixed value. overall, however, modelled qbos are very similar whether or not the prescribed ssts vary interannually. a portrait of the overall ensemble performance is provided by a normalized grading of qbo metrics. to simulate a qbo, all but one model used parametrized nogws, which provided the majority of the total wave forcing at altitudes above 70 hpa in most models. hence the representation of nogws either explicitly or through parametrization is still a major uncertainty underlying qbo simulation in these present-day experiments. | evaluation of the quasi-biennial oscillation in global climate models for the sparc qbo-initiative |
the ligo open science center (losc) fulfills ligo's commitment to release, archive, and serve ligo data in a broadly accessible way to the scientific community and to the public, and to provide the information and tools necessary to understand and use the data. in august 2014, the losc published the full dataset from initial ligo's “s5” run at design sensitivity, the first such large-scale release and a valuable testbed to explore the use of ligo data by non-ligo researchers and by the public, and to help teach gravitational-wave data analysis to students across the world. in addition to serving the s5 data, the losc web portal (losc.ligo.org) now offers documentation, data-location and data-quality queries, tutorials and example code, and more. we review the mission and plans of the losc, focusing on the s5 data release. | the ligo open science center |
we develop a formalism to calculate the response of a model gravitational wave detector to a quantized gravitational field. coupling a detector to a quantum field induces stochastic fluctuations ("noise") in the length of the detector arm. the statistical properties of this noise depend on the choice of quantum state of the gravitational field. we characterize the noise for vacuum, coherent, thermal, and squeezed states. for coherent states, corresponding to classical gravitational configurations, we find that the effect of gravitational field quantization is small. however, the standard deviation in the arm length can be enhanced—possibly significantly—when the gravitational field is in a noncoherent state. the detection of this fundamental noise could provide direct evidence for the quantization of gravity and for the existence of gravitons. | signatures of the quantization of gravity at gravitational wave detectors |
gravitational waves (gws) from strong first-order phase transitions (sfopts) in the early universe are a prime target for upcoming gw experiments. in this paper, i construct novel peak-integrated sensitivity curves (piscs) for these experiments, which faithfully represent their projected sensitivities to the gw signal from a cosmological sfopt by explicitly taking into account the expected shape of the signal. designed to be a handy tool for phenomenologists and model builders, piscs allow for a quick and systematic comparison of theoretical predictions with experimental sensitivities, as i illustrate by a large range of examples. piscs also offer several advantages over the conventional power-law-integrated sensitivity curves (pliscs); in particular, they directly encode information on the expected signal-to-noise ratio for the gw signal from a sfopt. i provide semianalytical fit functions for the exact numerical piscs of lisa, decigo, and bbo. in an appendix, i moreover present a detailed review of the strain noise power spectra of a large number of gw experiments. the numerical results for all piscs, pliscs, and strain noise power spectra presented in this paper can be downloaded from the zenodo online repository [1]. in a companion paper [2], the concept of piscs is used to perform an in-depth study of the gw signal from the cosmological phase transition in the real-scalar-singlet extension of the standard model. the piscs presented in this paper will need to be updated whenever new theoretical results on the expected shape of the signal become available. the pisc approach is therefore suited to be used as a bookkeeping tool to keep track of the theoretical progress in the field. | new sensitivity curves for gravitational-wave signals from cosmological phase transitions |
in the emergence proposal in quantum gravity it is conjectured that all light-particle kinetic terms are absent in the fundamental ultraviolet theory and are generated by quantum corrections in the infrared. it has been argued that this may provide for some microscopic understanding of the weak gravity and distance conjectures. in the present paper we take the first steps towards a systematic study of emergence in the context of string theory. we emphasize the crucial role of the species scale in any effective field theory coupled to gravity, and discuss its computation in string theory and general systems with light towers of states. we then introduce the notion of emergence and show how kinetic terms for moduli, gauge bosons and fermions may be generated. one-loop computations play an important role in emergence, so we present detailed calculations in d spacetime dimensions for the wave-function renormalization of scalars, vectors and fermions. we extend and check the emergence proposal in a number string vacua, including 4d n = 2 theories arising from type iia on a cy3, where the towers at strong coupling are comprised by d0 and (wrapped) d2-branes, and also elaborate on how instanton corrections would fit within the emergence picture. higher dimensional examples are also discussed, including 6d and 7d models arising from f-/m-theory on an elliptic cy3 or a k3 surface. we also consider 10d string theories and study in some detail the emergence mechanism in type iia. we show as well how the flux potential in 4d may be obtained from the emergence prescription, by analyzing the corresponding decompactification limits to m-theory. we find that the required kinetic terms for the dual 3-form fields can arise upon integrating out towers of massive gravitini (and bosonic superpartners). our analysis renders support to the emergence proposal, and to the idea that infinite distance singularities may arise in quantum gravity as an intrinsic infrared phenomenon. | the emergence proposal in quantum gravity and the species scale |
the effects of local lorentz violation on dispersion and birefringence of gravitational waves are investigated. the covariant dispersion relation for gravitational waves involving gauge-invariant lorentz-violating operators of arbitrary mass dimension is constructed. the chirp signal from the gravitational-wave event gw150914 is used to place numerous first constraints on gravitational lorentz violation. | testing local lorentz invariance with gravitational waves |
we use a dual-species atom interferometer with 2 s of free-fall time to measure the relative acceleration between rb 85 and rb 87 wave packets in the earth's gravitational field. systematic errors arising from kinematic differences between the isotopes are suppressed by calibrating the angles and frequencies of the interferometry beams. we find an eötvös parameter of η =[1.6 ±1.8 (stat ) ±3.4 (syst ) ]×10-12, consistent with zero violation of the equivalence principle. with a resolution of up to 1.4 ×10-11 g per shot, we demonstrate a sensitivity to η of 5.4 ×10-11/√{hz }. | atom-interferometric test of the equivalence principle at the 10-12 level |
advances in scattering amplitudes have exposed previously-hidden color-kinematics and double-copy structures in theories ranging from gauge and gravity theories to effective field theories such as chiral perturbation theory and the born-infeld model. these novel structures both simplify higher-order calculations and pose tantalizing questions related to a unified framework underlying relativistic quantum theories. this introductory mini-review article invites further exploration of these topics. after a brief introduction to color-kinematics duality and the double copy as they emerges at tree and loop-level in gauge and gravity theories, we present two distinct examples: 1) an introduction to the web of double-copy-constructible theories, and 2) a discussion on the application of the double copy to calculation relevant to gravitational-wave physics. | the sagex review on scattering amplitudes, chapter 2: an invitation to color-kinematics duality and the double copy |
this study presents the version of the lmdz global atmospheric model used as the atmospheric component of the institut pierre simon laplace coupled model (ipsl-cm6a-lr) to contribute to the 6th phase of the international coupled model intercomparison project (cmip6). this lmdz6a version includes original convective parameterizations that define the lmdz "new physics": a mass flux parameterization of the organized structures of the convective boundary layer, the "thermal plume model," and a parameterization of the cold pools created by reevaporation of convective rainfall. the vertical velocity associated with thermal plumes and gust fronts of cold pools are used to control the triggering and intensity of deep convection. because of several shortcomings, the early version 5b of this new physics was worse than the previous "standard physics" version 5a regarding several classical climate metrics. to overcome these deficiencies, version 6a includes new developments: a stochastic triggering of deep convection, a modification of the thermal plume model that allows the representation of stratocumulus and cumulus clouds in a unified framework, an improved parameterization of very stable boundary layers, and the modification of the gravity waves scheme targeting the quasi-biennal oscillation in the stratosphere. these improvements to the physical content and a more well-defined tuning strategy led to major improvements in the lmdz6a version model climatology. beyond the presentation of this particular model version and documentation of its climatology, the present paper underlines possible methodological pathways toward model improvement that can be shared across modeling groups. | lmdz6a: the atmospheric component of the ipsl climate model with improved and better tuned physics |
internal gravity waves (igws) and balanced motions (bms) with scales <100-km capture most of the vertical velocity field in the upper ocean. they have, however, different impacts on the ocean energy budget, which explains the need to partition motions into bms and igws. one way is to exploit the synergy of using different satellite observations, the only observations with global coverage, and a reasonable spatial and temporal resolution. but we need first to characterize and understand their signatures on the different surface oceanic fields. this study addresses this issue by using an ocean global numerical simulation with high-resolution (1/48°). our methodology is based on the analysis of the 12,000 frequency-wave number spectra to discriminate these two classes of motions in the surface kinetic energy, sea surface height, sea surface temperature, sea surface salinity, relative vorticity, and divergence fields and for two seasons. results reveal a complex picture worldwide of the partition of motions between igws and bms in the different surface fields, depending on the season, the hemisphere, and low and high eddy kinetic energy regions. but they also highlight some generic properties on the impact of these two classes of motions on the different fields. this points to the synergy of using present and future satellite observations to assess the ocean kinetic energy on a global scale. the 12,000 frequency-wave number spectra represent a world ocean atlas of the surface ocean dynamics not fully exploited in the present study. we hope the use of this world ocean atlas by other studies will lead to extend much these results. | partitioning ocean motions into balanced motions and internal gravity waves: a modeling study in anticipation of future space missions |
we study the effect of cubic and tidal interactions on the spectrum of gravitational waves emitted in the inspiral phase of the merger of two nonspinning objects. there are two independent parity-even cubic interaction terms, which we take to be i1 = rαβμν rμνρσ rρσαβ and g3 = i1-2 rαμβν rμρνσ rρασβ. the latter has vanishing pure graviton amplitudes but modifies mixed scalar/graviton amplitudes which are crucial for our study. working in an effective field theory setup, we compute the modifications to the quadrupole moment due to i1, g3 and tidal interactions, from which we obtain the power of gravitational waves radiated in the process to first order in the perturbations and leading order in the post-minkowskian expansion. the i1 predictions are novel, and we find that our results for g3 are related to the known quadrupole corrections arising from tidal perturbations, although the physical origin of the g3 coupling is unrelated to the finite-size effects underlying tidal interactions. we show this by recomputing such tidal corrections and by presenting an explicit field redefinition. in the post-newtonian expansion our results are complete at leading order, which for the gravitational-wave flux is 5pn for g3 and tidal interactions and 6pn for i1. finally, we compute the corresponding modifications to the waveforms. | from amplitudes to gravitational radiation with cubic interactions and tidal effects |
volcanoes can produce tsunamis by means of earthquakes, caldera and flank collapses, pyroclastic flows or underwater explosions1-4. these mechanisms rarely displace enough water to trigger transoceanic tsunamis. violent volcanic explosions, however, can cause global tsunamis1,5 by triggering acoustic-gravity waves6-8 that excite the atmosphere-ocean interface. the colossal eruption of the hunga tonga-hunga ha'apai volcano and ensuing tsunami is the first global volcano-triggered tsunami recorded by modern, worldwide dense instrumentation, thus providing a unique opportunity to investigate the role of air-water-coupling processes in tsunami generation and propagation. here we use sea-level, atmospheric and satellite data from across the globe, along with numerical and analytical models, to demonstrate that this tsunami was driven by a constantly moving source in which the acoustic-gravity waves radiating from the eruption excite the ocean and transfer energy into it by means of resonance. a direct correlation between the tsunami and the acoustic-gravity waves' arrival times confirms that these phenomena are closely linked. our models also show that the unusually fast travel times and long duration of the tsunami, as well as its global reach, are consistent with an air-water-coupled source. this coupling mechanism has clear hazard implications, as it leads to higher waves along land masses that rise abruptly from long stretches of deep ocean waters. | global tonga tsunami explained by a fast-moving atmospheric source |
celestial amplitudes which use conformal primary wave functions rather than plane waves as external states offer a novel opportunity to study properties of amplitudes with manifest conformal covariance and give insight into a potential holographic celestial conformal field theory at the null boundary of asymptotically flat space. since translation invariance is obscured in the conformal basis, features of amplitudes that heavily rely on it appear to be lost. among these are the remarkable relations between gauge theory and gravity amplitudes known as the double copy. nevertheless, properties of amplitudes reflecting fundamental aspects of the perturbative regime of quantum field theory are expected to survive a change of basis. here we show that there exists a well-defined procedure for a celestial double copy. this requires a generalization of the usual squaring of numerators which entails first promoting them to generalized differential operators acting on external wave functions and then squaring them. we demonstrate this procedure for three- and four-point celestial amplitudes and give an argument for its validity to all multiplicities. | double copy for celestial amplitudes |
this paper investigates the local and global ionospheric responses to the 2022 tonga volcano eruption, using ground-based global navigation satellite system total electron content (tec), swarm in situ plasma density measurements, the ionospheric connection explorer (icon) ion velocity meter (ivm) data, and ionosonde measurements. the main results are as follows: (a) a significant local ionospheric hole of more than 10 tecu depletion was observed near the epicenter ∼45 min after the eruption, comprising of several cascading tec decreases and quasi-periodic oscillations. such a deep local plasma hole was also observed by space-borne in situ measurements, with an estimated horizontal radius of 10-15° and persisted for more than 10 hr in icon-ivm ion density profiles until local sunrise. (b) pronounced post-volcanic evening equatorial plasma bubbles (epbs) were continuously observed across the wide asia-oceania area after the arrival of volcano-induced waves; these caused a ne decrease of 2-3 orders of magnitude at swarm/icon altitude between 450 and 575 km, covered wide longitudinal ranges of more than 140°, and lasted around 12 hr. (c) various acoustic-gravity wave modes due to volcano eruption were observed by accurate beidou geostationary orbit (geo) tec, and the huge ionospheric hole was mainly caused by intense shock-acoustic impulses. tec rate of change index revealed globally propagating ionospheric disturbances at a prevailing lamb-wave mode of ∼315 m/s; the large-scale epbs could be seeded by acoustic-gravity resonance and coupling to less-damped lamb waves, under a favorable condition of volcano-induced enhancement of dusktime plasma upward e×b drift and postsunset rise of the equatorial ionospheric f-layer. | significant ionospheric hole and equatorial plasma bubbles after the 2022 tonga volcano eruption |
this study discusses the upper-ocean (0-200 m) horizontal wavenumber spectra in the drake passage from 13 yr of shipboard adcp measurements, altimeter data, and a high-resolution numerical simulation. at scales between 10 and 200 km, the adcp kinetic energy spectra approximately follow ak−3power law. the observed flows are more energetic at the surface, but the shape of the kinetic energy spectra is independent of depth. these characteristics resemble predictions of isotropic interior quasigeostrophic turbulence. the ratio of across-track to along-track kinetic energy spectra, however, significantly departs from the expectation of isotropic interior quasigeostrophic turbulence. the inconsistency is dramatic at scales smaller than 40 km. a helmholtz decomposition of the adcp spectra and analyses of synthetic and numerical model data show that horizontally divergent, ageostrophic flows account for the discrepancy between the observed spectra and predictions of isotropic interior quasigeostrophic turbulence. in drake passage, ageostrophic motions appear to be dominated by inertia-gravity waves and account for about half of the near-surface kinetic energy at scales between 10 and 40 km. model results indicate that ageostrophic flows imprint on the sea surface, accounting for about half of the sea surface height variance between 10 and 40 km. | mesoscale to submesoscale wavenumber spectra in drake passage |
atom interferometers have been developed in the last three decades as new powerful tools to investigate gravity. they were used for measuring the gravity acceleration, the gravity gradient, and the gravity-field curvature, for the determination of the gravitational constant, for the investigation of gravity at microscopic distances, to test the equivalence principle of general relativity and the theories of modified gravity, to probe the interplay between gravitational and quantum physics and to test quantum gravity models, to search for dark matter and dark energy, and they were proposed as new detectors for the observation of gravitational waves. here i describe past and ongoing experiments with an outlook on what i think are the main prospects in this field and the potential to search for new physics. | testing gravity with cold atom interferometry: results and prospects |
dark matter may induce apparent temporal variations in the physical "constants", including the electromagnetic fine-structure constant and fermion masses. in particular, a coherently oscillating classical dark-matter field may induce apparent oscillations of physical constants in time, while the passage of macroscopic dark-matter objects (such as topological defects) may induce apparent transient variations in the physical constants. in this paper, we point out several new signatures of the aforementioned types of dark matter that can arise due to the geometric asymmetry created by the beam-splitter in a two-arm laser interferometer. these new signatures include dark-matter-induced time-varying size changes of a freely suspended beam-splitter and associated time-varying shifts of the main reflecting surface of the beam-splitter that splits and recombines the laser beam, as well as time-varying refractive-index changes in the freely suspended beam-splitter and time-varying size changes of freely suspended arm mirrors. we demonstrate that existing ground-based experiments already have sufficient sensitivity using existing data to probe extensive regions of the unconstrained parameter space in models involving oscillating scalar dark-matter fields and domain walls composed of scalar fields. in the case of oscillating dark-matter fields, michelson interferometers—in particular, the geo 600 detector—are especially sensitive. the sensitivity of fabry-perot-michelson interferometers, including ligo, virgo, and kagra, to oscillating dark-matter fields can be significantly increased by making the thicknesses of the freely suspended fabry-perot arm mirrors different in the two arms. not-too-distantly separated laser interferometers can benefit from cross-correlation measurements in searches for effects of spatially coherent dark-matter fields. in addition to broadband searches for oscillating dark-matter fields, we also discuss how small-scale michelson interferometers, such as the fermilab holometer, could be used to perform resonant narrowband searches for oscillating dark-matter fields with enhanced sensitivity to dark matter. finally, we discuss the possibility of using future space-based detectors, such as lisa, to search for dark matter via time-varying size changes of and time-varying forces exerted on freely floating test masses. | novel signatures of dark matter in laser-interferometric gravitational-wave detectors |
studies of the madden-julian oscillation (mjo) have progressed considerably during the past decades in observations, numerical modeling, and theoretical understanding. many theoretical attempts have been made to identify the most essential processes responsible for the existence of the mjo. criteria are proposed to separate a hypothesis from a theory (based on the first principles with quantitative and testable assumptions, able to predict quantitatively the fundamental scales and eastward propagation of the mjo). four mjo theories are selected to be summarized and compared in this article: the skeleton theory, moisture-mode theory, gravity-wave theory, and trio-interaction theory of the mjo. these four mjo theories are distinct from each other in their key assumptions, parameterized processes, and, particularly, selection mechanisms for the zonal spatial scale, time scale, and eastward propagation of the mjo. the comparison of the four theories and more recent development in mjo dynamical approaches lead to a realization that theoretical thinking of the mjo is diverse and understanding of mjo dynamics needs to be further advanced. | four theories of the madden-julian oscillation |
this whitepaper summarizes the status of the esa-led laser interferometer space antenna (lisa) mission and advocates for an increased us role within the ‘medium’ mission category. the lisa science case, mission concept, technical readiness, and organizational partnerships are summarized and broad scenarios for us participation are described. | the laser interferometer space antenna: unveiling the millihertz gravitational wave sky |
we compute the partition function of $2d$ jackiw-teitelboim (jt) gravity at finite cutoff in two ways: (i) via an exact evaluation of the wheeler-dewitt wave-functional in radial quantization and (ii) through a direct computation of the euclidean path integral. both methods deal with dirichlet boundary conditions for the metric and the dilaton. in the first approach, the radial wavefunctionals are found by reducing the constraint equations to two first order functional derivative equations that can be solved exactly, including factor ordering. in the second approach we perform the path integral exactly when summing over surfaces with disk topology, to all orders in perturbation theory in the cutoff. both results precisely match the recently derived partition function in the schwarzian theory deformed by an operator analogous to the $t\bar{t}$ deformation in $2d$ cfts. this equality can be seen as concrete evidence for the proposed holographic interpretation of the $t\bar{t}$ deformation as the movement of the ads boundary to a finite radial distance in the bulk. | jt gravity at finite cutoff |
the physics of low-energy quantum systems is usually studied without explicit consideration of the background spacetime. phenomena inherent to quantum theory in curved spacetime, such as hawking radiation, are typically assumed to be relevant only for extreme physical conditions: at high energies and in strong gravitational fields. here we consider low-energy quantum mechanics in the presence of gravitational time dilation and show that the latter leads to the decoherence of quantum superpositions. time dilation induces a universal coupling between the internal degrees of freedom and the centre of mass of a composite particle. the resulting correlations lead to decoherence in the particle position, even without any external environment. we also show that the weak time dilation on earth is already sufficient to affect micrometre-scale objects. gravity can therefore account for the emergence of classicality and this effect could in principle be tested in future matter-wave experiments. | universal decoherence due to gravitational time dilation |
we show that we can derive the asymptotic einstein's equations that arises at order 1/r in asymptotically flat gravity purely from symmetry considerations. this is achieved by studying the transformation properties of functionals of the metric and the stress-energy tensor under the action of the weyl bms group, a recently introduced asymptotic symmetry group that includes arbitrary diffeomorphisms and local conformal transformations of the metric on the 2-sphere. our derivation, which encompasses the inclusion of matter sources, leads to the identification of covariant observables that provide a definition of conserved charges parametrizing the non-radiative corner phase space. these observables, related to the weyl scalars, reveal a duality symmetry and a spin-2 generator which allow us to recast the asymptotic evolution equations in a simple and elegant form as conservation equations for a null fluid living at null infinity. finally we identify non-linear gravitational impulse waves that describe transitions among gravitational vacua and are non-perturbative solutions of the asymptotic einstein's equations. this provides a new picture of quantization of the asymptotic phase space, where gravitational vacua are representations of the asymptotic symmetry group and impulsive waves are encoded in their couplings. | gravity from symmetry: duality and impulsive waves |
we calculate the tidal corrections to the loss of angular momentum in a two-body collision at leading post-minkowskian order from an amplitude-based approach. the eikonal operator allows us to efficiently combine elastic and inelastic amplitudes, and captures both the contributions due to genuine gravitational-wave emissions and those due to the static gravitational field. we calculate the former by harnessing powerful collider-physics techniques such as reverse unitarity, thereby reducing them to cut two-loop integrals, and cross check the result by performing an independent calculation in the post-newtonian limit. for the latter, we can employ the results of p. di vecchia et al. [angular momentum of zero-frequency gravitons, j. high energy phys. 08 (2022) 172., 10.1007/jhep08(2022)172], where static-field effects were calculated for generic gravitational scattering events using the leading soft graviton theorem. | angular momentum loss due to tidal effects in the post-minkowskian expansion |
the observation of gravitational waves is hindered by the presence of transient noise (glitches). we study data from the third observing run of the advanced ligo detectors, and identify new glitch classes: fast scattering/crown and low-frequency blips. using training sets assembled by monitoring of the state of the detector, and by citizen-science volunteers, we update the gravity spy machine-learning algorithm for glitch classification. we find that fast scattering/crown, linked to ground motion at the detector sites, is especially prevalent, and identify two subclasses linked to different types of ground motion. reclassification of data based on the updated model finds that ~27% of all transient noise at ligo livingston belongs to the fast scattering class, while ~8% belongs to the low-frequency blip class, making them the most frequent and fourth most frequent sources of transient noise at that site. our results demonstrate both how glitch classification can reveal potential improvements to gravitational-wave detectors, and how, given an appropriate framework, citizen-science volunteers may make discoveries in large data sets. | discovering features in gravitational-wave data through detector characterization, citizen science and machine learning |
working within the post-minkowskian approach to general relativity, we prove that the radiation-reaction to the emission of gravitational waves during the large-impact-parameter scattering of two (classical) point masses modifies the conservative scattering angle by an additional contribution of order g3 which involves a high-energy (or massless) logarithmic divergence of opposite sign to the one contained in the third-post-minkowskian result of bern et al. [phys. rev. lett. 122, 201603 (2019), 10.1103/physrevlett.122.201603]. the high-energy limit of the resulting radiation-reaction-corrected (classical) scattering angle is finite, and is found to agree with the one following from the (quantum) eikonal-phase result of amati et al. [nucl. phys. b347, 550 (1990), 10.1016/0550-3213(90)90375-n]. | radiative contribution to classical gravitational scattering at the third order in g |
the linear- and quadratic-in-spin contributions to the binding potential and gravitational-wave flux from binary systems are derived to next-to-next-to-leading order in the post-newtonian (pn) expansion of general relativity, including finite-size and tail effects. the calculation is carried out through the worldline effective field theory framework. we find agreement in the overlap with the available pn and self-force literature. as a direct application, we complete the knowledge of spin effects in the evolution of the orbital phase for aligned-spin circular orbits to fourth pn order. we estimate the impact in the number of accumulated gravitational-wave cycles and find they make a significant contribution for next-generation observatories. the results presented here will therefore play an important role in providing reliable physical interpretation of gravitational-wave signals from spinning binaries with future gravitational-wave detectors such as lisa and the einstein telescope. | gravitational radiation from inspiralling compact objects: spin effects to the fourth post-newtonian order |
for the purpose of analyzing observed phenomena, it has been convenient, and thus far sufficient, to regard gravity as subject to the deterministic principles of classical physics, with the gravitational field obeying newton's law or einstein's equations. here we treat the gravitational field as a quantum field and determine the implications of such treatment for experimental observables. we find that falling bodies in gravity are subject to random fluctuations ("noise") whose characteristics depend on the quantum state of the gravitational field. we derive a stochastic equation for the separation of two falling particles. detection of this fundamental noise, which may be measurable at gravitational wave detectors, would vindicate the quantization of gravity, and reveal important properties of its sources. | quantum mechanics of gravitational waves |
we present the first-generation global tomographic model constructed based on adjoint tomography, an iterative full-waveform inversion technique. synthetic seismograms were calculated using gpu-accelerated spectral-element simulations of global seismic wave propagation, accommodating effects due to 3-d anelastic crust & mantle structure, topography & bathymetry, the ocean load, ellipticity, rotation, and self-gravitation. fréchet derivatives were calculated in 3-d anelastic models based on an adjoint-state method. the simulations were performed on the cray xk7 named `titan', a computer with 18 688 gpu accelerators housed at oak ridge national laboratory. the transversely isotropic global model is the result of 15 tomographic iterations, which systematically reduced differences between observed and simulated three-component seismograms. our starting model combined 3-d mantle model s362ani with 3-d crustal model crust2.0. we simultaneously inverted for structure in the crust and mantle, thereby eliminating the need for widely used `crustal corrections'. we used data from 253 earthquakes in the magnitude range 5.8 ≤ mw ≤ 7.0. we started inversions by combining ∼30 s body-wave data with ∼60 s surface-wave data. the shortest period of the surface waves was gradually decreased, and in the last three iterations we combined ∼17 s body waves with ∼45 s surface waves. we started using 180 min long seismograms after the 12th iteration and assimilated minor- and major-arc body and surface waves. the 15th iteration model features enhancements of well-known slabs, an enhanced image of the samoa/tahiti plume, as well as various other plumes and hotspots, such as caroline, galapagos, yellowstone and erebus. furthermore, we see clear improvements in slab resolution along the hellenic and japan arcs, as well as subduction along the east of scotia plate, which does not exist in the starting model. point-spread function tests demonstrate that we are approaching the resolution of continental-scale studies in some areas, for example, underneath yellowstone. this is a consequence of our multiscale smoothing strategy in which we define our smoothing operator as a function of the approximate hessian kernel, thereby smoothing gradients less wherever we have good ray coverage, such as underneath north america. | global adjoint tomography: first-generation model |
cold-atom inertial sensors target several applications in navigation, geoscience and tests of fundamental physics. reaching high sampling rates and high inertial sensitivities, obtained with long interrogation times, represents a challenge for these applications. we report on the interleaved operation of a cold-atom gyroscope, where 3 atomic clouds are interrogated simultaneously in an atom interferometer featuring a 3.75 hz sampling rate and an interrogation time of 801 ms. interleaving improves the inertial sensitivity by efficiently averaging vibration noise, and allows us to perform dynamic rotation measurements in a so-far unexplored range. we demonstrate a stability of $3\times 10^{-10}$ rad.s$^{-1}$, which competes with the best stability levels obtained with fiber-optics gyroscopes. our work validates interleaving as a key concept for future atom-interferometry sensors probing time-varying signals, as in on-board navigation and gravity-gradiometry, searches for dark matter, or gravitational wave detection. | interleaved atom interferometry for high-sensitivity inertial measurements |
we analyze the classically scale-invariant b -l model in the context of resonant leptogenesis with the recently proposed mass-gain mechanism. the b -l symmetry breaking in this scenario is associated with a strong first-order phase transition that gives rise to detectable gravitational waves (gws) via bubble collisions. the same b -l symmetry breaking also gives majorana mass to right-handed neutrinos inside the bubbles, and their out-of-equilibrium decays can produce the observed baryon asymmetry of the universe via leptogenesis. we show that the current ligo-virgo limit on stochastic gw background already excludes part of the b -l parameter space, complementary to the collider searches for heavy z' resonances. moreover, future gw experiments like einstein telescope and cosmic explorer can effectively probe the parameter space of leptogenesis over a wide range of the b -l symmetry-breaking scales and gauge coupling values. | gravitational wave pathway to testable leptogenesis |
this is a snowmass white paper on the utility of existing and future superconducting cavities to probe fundamental physics. superconducting radio frequency (srf) cavity technology has seen tremendous progress in the past decades, as a tool for accelerator science. with advances spear-headed by the sqms center at fermilab, they are now being brought to the quantum regime becoming a tool in quantum science thanks to the high degree of coherence. the same high quality factor can be leveraged in the search for new physics, including searches for new particles, dark matter, including the qcd axion, and gravitational waves. we survey some of the physics opportunities and the required directions of r&d. given the already demonstrated integration of srf cavities in large accelerator systems, this r&d may enable larger scale searches by dedicated experiments. | searches for new particles, dark matter, and gravitational waves with srf cavities |
tensor network theory and quantum simulation are, respectively, the key classical and quantum computing methods in understanding quantum many-body physics. here, we introduce the framework of hybrid tensor networks with building blocks consisting of measurable quantum states and classically contractable tensors, inheriting both their distinct features in efficient representation of many-body wave functions. with the example of hybrid tree tensor networks, we demonstrate efficient quantum simulation using a quantum computer whose size is significantly smaller than the one of the target system. we numerically benchmark our method for finding the ground state of 1d and 2d spin systems of up to 8 ×8 and 9 ×8 qubits with operations only acting on 8 +1 and 9 +1 qubits, respectively. our approach sheds light on simulation of large practical problems with intermediate-scale quantum computers, with potential applications in chemistry, quantum many-body physics, quantum field theory, and quantum gravity thought experiments. | quantum simulation with hybrid tensor networks |
we compare the response of the quasi-biennial oscillation (qbo) to a warming climate in eleven atmosphere general circulation models that performed time-slice simulations for present-day, doubled, and quadrupled co2 climates. no consistency was found among the models for the qbo period response, with the period decreasing by 8 months in some models and lengthening by up to 13 months in others in the doubled co2 simulations. in the quadrupled co2 simulations, a reduction in qbo period of 14 months was found in some models, whereas in several others the tropical oscillation no longer resembled the present-day qbo, although it could still be identified in the deseasonalized zonal mean zonal wind timeseries. in contrast, all the models projected a decrease in the qbo amplitude in a warmer climate with the largest relative decrease near 60 hpa. in simulations with doubled and quadrupled co2, the multi-model mean qbo amplitudes decreased by 36 and 51%, respectively. across the models the differences in the qbo period response were most strongly related to how the gravity wave momentum flux entering the stratosphere and tropical vertical residual velocity responded to the increases in co2 amounts. likewise it was found that the robust decrease in qbo amplitudes was correlated across the models to changes in vertical residual velocity, parametrized gravity wave momentum fluxes, and to some degree the resolved upward wave flux. we argue that uncertainty in the representation of the parameterized gravity waves is the most likely cause of the spread among the eleven models in the qbo's response to climate change. | response of the quasi-biennial oscillation to a warming climate in global climate models |
we present our broad-band study of gw170817 from radio to hard x-rays, including nustar and chandra observations up to 165 d after the merger, and a multimessenger analysis including ligo constraints. the data are compared with predictions from a wide range of models, providing the first detailed comparison between non-trivial cocoon and jet models. homogeneous and power-law shaped jets, as well as simple cocoon models are ruled out by the data, while both a gaussian shaped jet and a cocoon with energy injection can describe the current data set for a reasonable range of physical parameters, consistent with the typical values derived from short grb afterglows. we propose that these models can be unambiguously discriminated by future observations measuring the post-peak behaviour, with fν ∝ t∼-1.0 for the cocoon and fν∝ t∼-2.5 for the jet model. | the outflow structure of gw170817 from late-time broad-band observations |
this study puts forward a generalization of the short-time fourier-based synchrosqueezing transform using a new local estimate of instantaneous frequency. such a technique enables not only to achieve a highly concentrated time-frequency representation for a wide variety of am-fm multicomponent signals but also to reconstruct their modes with a high accuracy. numerical investigation on synthetic and gravitational-wave signals shows the efficiency of this new approach. | high-order synchrosqueezing transform for multicomponent signals analysis—with an application to gravitational-wave signal |
the colloquium reviews recent progress in the effective description of strongly correlated phases of matter with spontaneously broken translations, such as charge density waves or wigner crystals. in real materials, disorder is inevitable and pins the goldstones of broken translations. the colloquium describes how pinning can be incorporated into the effective field theory at low energies without making any assumptions on the presence of boost symmetry. the essential role played by gauge-gravity duality models in establishing these effective field theories with only approximate symmetries is reviewed. the colloquium closes with a discussion on the relevance of these models to the phenomenology of dc and ac transport in strongly correlated strange and bad metals, such as high-temperature superconductors. | colloquium: hydrodynamics and holography of charge density wave phases |
an ensemble of atoms can operate as a quantum sensor by placing atoms in a superposition of two different states. upon measurement of the sensor, each atom is individually projected into one of the two states. creating quantum correlations between the atoms, that is entangling them, could lead to resolutions surpassing the standard quantum limit1-3 set by projections of individual atoms. large amounts of entanglement4-6 involving the internal degrees of freedom of laser-cooled atomic ensembles4-16 have been generated in collective cavity quantum-electrodynamics systems, in which many atoms simultaneously interact with a single optical cavity mode. here we report a matter-wave interferometer in a cavity quantum-electrodynamics system of 700 atoms that are entangled in their external degrees of freedom. in our system, each individual atom falls freely under gravity and simultaneously traverses two paths through space while entangled with the other atoms. we demonstrate both quantum non-demolition measurements and cavity-mediated spin interactions for generating squeezed momentum states with directly observed sensitivity 3 .4−0.9+1.1 db and 2 .5−0.6+0.6 db below the standard quantum limit, respectively. we successfully inject an entangled state into a mach-zehnder light-pulse interferometer with directly observed sensitivity 1 .7−0.5+0.5 db below the standard quantum limit. the combination of particle delocalization and entanglement in our approach may influence developments of enhanced inertial sensors17,18, searches for new physics, particles and fields19-23, future advanced gravitational wave detectors24,25 and accessing beyond mean-field quantum many-body physics26-30. | entanglement-enhanced matter-wave interferometry in a high-finesse cavity |
decigo (deci-hertz interferometer gravitational wave observatory) is the planned japanese space gravitational wave antenna, aiming to detect gravitational waves from astrophysically and cosmologically significant sources mainly between 0.1 hz and 10 hz and thus to open a new window for gravitational wave astronomy and for the universe. decigo will consists of three drag-free spacecraft arranged in an equilateral triangle with 1000 km arm lengths whose relative displacements are measured by a differential fabry-perot interferometer, and four units of triangular fabry-perot interferometers are arranged on heliocentric orbit around the sun. decigo is vary ambitious mission, we plan to launch decigo in era of 2030s after precursor satellite mission, b-decigo. b-decigo is essentially smaller version of decigo: b-decigo consists of three spacecraft arranged in an triangle with 100 km arm lengths orbiting 2000 km above the surface of the earth. it is hoped that the launch date will be late 2020s for the present.. | the status of decigo |
do gravitational interactions respect the basic principles of relativity and quantum mechanics? we show that any graviton s -matrix that satisfies these assumptions cannot significantly differ from general relativity at low energies. we provide sharp bounds on the size of potential corrections in terms of the mass m of new higher-spin states, in spacetime dimensions d ≥5 where the s -matrix does not suffer from infrared ambiguities. the key novel ingredient is the full set of so (d -1 ) partial waves for this process, which we show how to efficiently compute with young tableau manipulations. we record new bounds on the central charges of holographic conformal theories. | graviton partial waves and causality in higher dimensions |
shortly after a new class of objects is discovered, the attention shifts from the properties of the individual sources to the question of their origin: do all sources come from the same underlying population, or several populations are required? what are the properties of these populations? as the detection of gravitational waves is becoming routine and the size of the event catalog increases, finer and finer details of the astrophysical distribution of compact binaries are now within our grasp. this chapter presents a pedagogical introduction to the main statistical tool required for these analyses: hierarchical bayesian inference in the presence of selection effects. all key equations are obtained from first principles, followed by two examples of increasing complexity. although many remarks made in this chapter refer to gravitational-wave astronomy, the write-up is generic enough to be useful to researchers and graduate students from other fields. | inferring the properties of a population of compact binaries in presence of selection effects |
we present a holographic analysis of diffractive photoproducton of charmonium j /ψ and upsilonium ϒ on a proton, considered as a bulk dirac fermion, for all ranges of √{s }, i.e., from near threshold to very high energy. using the bulk wave functions of the proton and vector mesons, within holographic qcd, and employing witten diagrams in the bulk, we compute the diffractive photoproduction amplitude of j /ψ and ϒ . the holographic amplitude shows elements of the strictures of vector meson dominance. it is dominated by the exchange of a massive graviton or 2++ glueball resonances near threshold, and its higher spin-j counterparts that reggeize at higher energies. both the differential and total cross sections are controlled by the gravitational form factor a (t ), and compare well to the recent results reported by the gluex collaboration near threshold and the world data at large √{s }. the holographic gravitational form factors, including the d-term, which is due to the exchange of massive spin-0 glueballs, are in good agreement with lattice simulations. we use it to extract the holographic pressure and shear forces inside the proton. finally, using a pertinent integral representation of the holographic gravitational form factor a (t ) near threshold, and its pomeron counterpart way above threshold, we extract the generalized parton distribution of gluons inside the proton at different resolutions. | diffractive photoproduction of j /ψ and ϒ using holographic qcd: gravitational form factors and gpd of gluons in the proton |
understanding the properties of transient gravitational waves (gws) and their sources is of broad interest in physics and astronomy. bayesian inference is the standard framework for astrophysical measurement in transient gw astronomy. usually, stochastic sampling algorithms are used to estimate posterior probability distributions over the parameter spaces of models describing experimental data. the most physically accurate models typically come with a large computational overhead which can render data analsis extremely time consuming, or possibly even prohibitive. in some cases highly specialized optimizations can mitigate these issues, though they can be difficult to implement, as well as to generalize to arbitrary models of the data. here, we investigate an accurate, flexible, and scalable method for astrophysical inference: parallelized nested sampling. the reduction in the wall-time of inference scales almost linearly with the number of parallel processes running on a high-performance computing cluster. by utilizing a pool of several hundreds or thousands of cpus in a high-performance cluster, the large wall times of many astrophysical inferences can be alleviated while simultaneously ensuring that any gw signal model can be used 'out of the box', i.e. without additional optimization or approximation. our method will be useful to both the ligo-virgo-kagra collaborations and the wider scientific community performing astrophysical analyses on gws. an implementation is available in the open source gravitational-wave inference library pbilby (parallel bilby). | massively parallel bayesian inference for transient gravitational-wave astronomy |
roger penrose proposed that a spatial quantum superposition collapses as a back-reaction from spacetime, which is curved in different ways by each branch of the superposition. in this sense, one speaks of gravity-related wave function collapse. he also provided a heuristic formula to compute the decay time of the superposition—similar to that suggested earlier by lajos diósi, hence the name diósi-penrose model. the collapse depends on the effective size of the mass density of particles in the superposition, and is random: this randomness shows up as a diffusion of the particles' motion, resulting, if charged, in the emission of radiation. here, we compute the radiation emission rate, which is faint but detectable. we then report the results of a dedicated experiment at the gran sasso underground laboratory to measure this radiation emission rate. our result sets a lower bound on the effective size of the mass density of nuclei, which is about three orders of magnitude larger than previous bounds. this rules out the natural parameter-free version of the diósi-penrose model. | underground test of gravity-related wave function collapse |
gamma-ray bursts (grbs) associated with gravitational wave events are, and will likely continue to be, viewed at a larger inclination than grbs without gravitational wave detections. as demonstrated by the afterglow of gw 170817a, this requires an extension of the common grb afterglow models, which typically assume emission from an on-axis top-hat jet. we present a characterization of the afterglows arising from structured jets, providing a framework covering both successful and choked jets. we compute new closure relations for decelerating structured jets and compare them with the established relations for energy injection and refreshed shock models. the temporal slope before the jet break is found to be a simple function of the ratio between the viewing angle and effective opening angle of the jet. a numerical model to calculate synthetic light curves and spectra is publicly available as the open-source python package afterglowpy. | gamma-ray burst afterglows in the multimessenger era: numerical models and closure relations |
this study analyzes a new high-resolution general circulation model with regard to secondary gravity waves in the mesosphere during austral winter. the model resolves gravity waves down to horizontal and vertical wavelengths of 165 and 1.5 km, respectively. the resolved mean wave drag agrees well with that from a conventional model with parameterized gravity waves up to the midmesosphere in winter and up to the upper mesosphere in summer. about half of the zonal-mean vertical flux of westward momentum in the southern winter stratosphere is due to orographic gravity waves. the high intermittency of the primary orographic gravity waves gives rise to secondary waves that result in a substantial eastward drag in the winter mesopause region. this induces an additional eastward maximum of the mean zonal wind at z ∼ 100 km. radar and lidar measurements at polar latitudes and results from other high-resolution global models are consistent with this finding. hence, secondary gravity waves may play a significant role in the general circulation of the winter mesopause region. | secondary gravity waves in the winter mesosphere: results from a high-resolution global circulation model |
the coalescence of compact objects is one of the most promising sources, as well as the source of the first detections, of gravitational waves for ground-based interferometric detectors, such as advanced ligo and virgo. generically, compact objects in binaries are expected to be spinning with spin angular momenta misaligned with the orbital angular momentum, causing the orbital plane to precess. this precession adds rich structure to the gravitational waves, introducing such complexity that an analytic closed-form description has been unavailable until now. we here construct the first closed-form frequency-domain gravitational waveforms that are valid for generic spin-precessing quasicircular compact binary inspirals. we first construct time-domain gravitational waves by solving the post-newtonian precession equations of motion with radiation reaction through multiple scale analysis. we then fourier transform these time-domain waveforms with the method of shifted uniform asymptotics to obtain closed-form expressions for frequency-domain waveforms. we study the accuracy of these analytic, frequency-domain waveforms relative to waveforms obtained by numerically evolving the post-newtonian equations of motion and find that they are suitable for unbiased parameter estimation for 99.2%(94.6%) of the binary configurations we studied at a signal-to-noise ratio of 10(25). these new frequency-domain waveforms could be used for detection and parameter estimation studies due to their accuracy and low computational cost. | constructing gravitational waves from generic spin-precessing compact binary inspirals |
atom interferometers are powerful tools for both measurements in fundamental physics and inertial sensing applications. their performance, however, has been limited by the available interrogation time of freely falling atoms in a gravitational field. by suspending the spatially separated atomic wave packets in a lattice formed by the mode of an optical cavity, we realize an interrogation time of 20 seconds. our approach allows gravitational potentials to be measured by holding, rather than dropping, atoms. after seconds of hold time, gravitational potential energy differences from as little as micrometers of vertical separation generate megaradians of interferometer phase. this trapped geometry suppresses the phase variance due to vibrations by three to four orders of magnitude, overcoming the dominant noise source in atom-interferometric gravimeters. | probing gravity by holding atoms for 20 seconds |
the tonga volcano eruption at 04:14:45 ut on 2022-01-15 released enormous amounts of energy into the atmosphere, triggering very significant geophysical variations not only in the immediate proximity of the epicenter but also globally across the whole atmosphere. this study provides a global picture of ionospheric disturbances over an extended period for at least 4 days. we find traveling ionospheric disturbances (tids) radially outbound and inbound along entire great-circle loci at primary speeds of ∼300–350 m/s (depending on the propagation direction) and 500–1,000 km horizontal wavelength for front shocks, going around the globe for three times, passing six times over the continental us in 100 h since the eruption. tids following the shock fronts developed for ∼8 h with 10–30 min predominant periods in near- and far- fields. tid global propagation is consistent with the effect of lamb waves which travel at the speed of sound. although these oscillations are often confined to the troposphere, lamb wave energy is known to leak into the thermosphere through channels such as atmospheric resonance at acoustic and gravity wave frequencies, carrying substantial wave amplitudes at high altitudes. prevailing lamb waves have been reported in the literature as atmospheric responses to the gigantic krakatoa eruption in 1883 and other geohazards. this study provides substantial first evidence of their long-duration imprints up in the global ionosphere. this study was enabled by ionospheric measurements from 5,000+ world-wide global navigation satellite system (gnss) ground receivers, demonstrating the broad implication of the ionosphere measurement as a sensitive detector for atmospheric waves and geophysical disturbances. | 2022 tonga volcanic eruption induced global propagation of ionospheric disturbances via lamb waves |
in 1957 feynman suggested that the quantum or classical character of gravity may be assessed by testing the gravitational interaction due to source masses in superposition. however, in all proposed experimental realizations using matter-wave interferometry, the extreme weakness of this interaction requires pure initial states with extreme squeezing to achieve measurable effects of nonclassical interaction for reasonable experiment durations. in practice, the systems that can be prepared in such nonclassical states are limited to small masses, which in turn limits the strength of their interaction. here we address this key challenge—the weakness of gravitational interaction—by using a massive body as an amplifying mediator of gravitational interaction between two test systems. our analysis shows that this results in an effective interaction between the two test systems that grows with the mass of the mediator, is independent of its initial state and, therefore, its temperature. this greatly reduces the requirement on the mass and degree of delocalization of the test systems and, while still highly challenging, brings experiments on gravitational source masses a step closer to reality. | enhancing gravitational interaction between quantum systems by a massive mediator |
we study the complementarity of the proposed multi-tev muon colliders and the near-future gravitational wave (gw) detectors to the first order electroweak phase transition (foewpt), taking the real scalar extended standard model as the representative model. a detailed collider simulation shows the foewpt parameter space can be greatly probed via the vector boson fusion production of the singlet, and its subsequent decay to the di-higgs or di-boson channels. especially, almost all the parameter space yielding detectable gw signals can be probed by the muon colliders. therefore, if we could detect stochastic gws in the future, a muon collider could provide a hopeful crosscheck to identify their origin. on the other hand, there is considerable parameter space that escapes gw detections but is within the reach of the muon colliders. the precision measurements of higgs couplings could also probe the foewpt parameter space efficiently. | probing electroweak phase transition with multi-tev muon colliders and gravitational waves |
we consider the uncertainty in the arm length of an interferometer due to metric fluctuations from the quantum nature of gravity, proposing a concrete microscopic model of energy fluctuations in holographic degrees of freedom on the surface bounding a causally connected region of spacetime. in our model, fluctuations longitudinal to the beam direction accumulate in the infrared and feature strong long distance correlation in the transverse direction. this leads to a signal that could be observed in a gravitational wave interferometer. we connect the positional uncertainty principle arising from our calculations to the 't hooft gravitational s-matrix. | observational signatures of quantum gravity in interferometers |
we compare recent one-loop-level, scattering-amplitude-based, computations of the classical part of the gravitational bremsstrahlung waveform to the frequency-domain version of the corresponding multipolar-post-minkowskian waveform result. when referring the one-loop result to the classical averaged momenta p¯ a=1/2 (pa+pa') , the two waveforms are found to agree at the newtonian and first post-newtonian levels, as well as at the first-and-a-half post-newtonian level, i.e., for the leading-order quadrupolar tail. however, we find that there are significant differences at the second-and-a-half post-newtonian level, o (g/2c5) , i.e., when reaching he following: (i) the first post-newtonian correction to the linear quadrupole tail; (ii) newtonian-level linear tails of higher multipolarity (odd octupole and even hexadecapole); (iii) radiation-reaction effects on the worldlines; and (iv) various contributions of cubically nonlinear origin (notably linked to the quadrupole × quadrupole × quadrupole coupling in the wave zone). these differences are reflected at the sub-sub-sub-leading level in the soft expansion, ∼ω ln ω , i.e., o (1/t2) in the time domain. finally, we computed the first four terms of the low-frequency expansion of the multipolar-post-minkowskian waveform and checked that they agree with the corresponding existing classical soft graviton results. | comparing one-loop gravitational bremsstrahlung amplitudes to the multipolar-post-minkowskian waveform |
if dark matter stems from the background of a very light gauge boson, this gauge boson could exert forces on test masses in gravitational wave detectors, resulting in displacements with a characteristic frequency set by the gauge boson mass. we outline a novel search strategy for such dark matter, assuming the dark photon is the gauge boson of u (1 )b or u (1 )b-l. we show that both ground-based and future space-based gravitational wave detectors have the capability to make a 5 σ discovery in unexplored parameter regimes. | searching for dark photon dark matter with gravitational-wave detectors |
the observation of the inspiral and merger of compact binaries by the ligo/virgo collaboration ushered in a new era in the study of strong-field gravity. we review current and future tests of strong gravity and of the kerr paradigm with gravitational-wave interferometers, both within a theory-agnostic framework (the parametrized post-einsteinian formalism) and in the context of specific modified theories of gravity (scalar-tensor, einstein-dilaton-gauss-bonnet, dynamical chern-simons, lorentz-violating, and extra dimensional theories). in this contribution we focus on (i) the information carried by the inspiral radiation, and (ii) recent progress in numerical simulations of compact binary mergers in modified gravity. | extreme gravity tests with gravitational waves from compact binary coalescences: (i) inspiral-merger |
models of large-field inflation based on axion-like fields with shift symmetries can be simple and natural, and make a promising prediction of detectable primordial gravitational waves. the weak gravity conjecture is known to constrain the simplest case in which a single compact axion descends from a gauge field in an extra dimension. we argue that the weak gravity conjecture also constrains a variety of theories of multiple compact axions including n-flation and some alignment models. we show that other alignment models entail surprising consequences for how the mass spectrum of the theory varies across the axion moduli space, and hence can be excluded if further conjectures hold. in every case that we consider, plausible assumptions lead to field ranges that cannot be parametrically larger than m pl. our results are strongly suggestive of a general inconsistency in models of large-field inflation based on compact axions, and possibly of a more general principle forbidding super-planckian field ranges. | weak gravity strongly constrains large-field axion inflation |
noise due to scattered light has been a frequent disturbance in the advanced ligo gravitational wave detectors, hindering the detection of gravitational waves. the non stationary scatter noise caused by low frequency motion can be recognized as arches in the time-frequency plane of the gravitational wave channel. in this paper, we characterize the scattering noise for ligo and virgo's third observing run o3 from april, 2019 to march, 2020. we find at least two different populations of scattering noise and we investigate the multiple origins of one of them as well as its mitigation. we find that relative motion between two specific surfaces is strongly correlated with the presence of scattered light and we implement a technique to reduce this motion. we also present an algorithm using a witness channel to identify the times this noise can be present in the detector. | reducing scattered light in ligo's third observing run |
advances in scattering amplitudes have exposed previously-hidden color-kinematics and double-copy structures in theories ranging from gauge and gravity theories to effective field theories such as chiral perturbation theory and the born-infeld model. these novel structures both simplify higher-order calculations and pose tantalizing questions related to a unified framework underlying relativistic quantum theories. this introductory mini-review article invites further exploration of these topics. after a brief introduction to color-kinematics duality and the double copy as they emerge at tree and loop-level in gauge and gravity theories, we present two distinct examples: (1) an introduction to the web of double-copy-constructible theories, and (2) a discussion of the application of the double copy to calculation relevant to gravitational-wave physics. | the sagex review on scattering amplitudes chapter 2: an invitation to color-kinematics duality and the double copy |
we study the imprint of light scalar fields on gravitational waves from extreme mass-ratio inspirals—binary systems with a very large mass asymmetry. we first show that, to leading order in the mass ratio, any effects of the scalar on the waveform are captured fully by two parameters: the mass of the scalar and the scalar charge of the secondary compact object. we then use this theory-agnostic framework to show that the future observations by lisa will be able to simultaneously measure both of these parameters with enough accuracy to detect ultralight scalars. | detecting massive scalar fields with extreme mass-ratio inspirals |
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