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Quantum fluctuations of the gravitational field in the early Universe, amplified by inflation, produce a primordial gravitational-wave background across a broad frequency band. We derive constraints on the spectrum of this gravitational radiation, and hence on theories of the early Universe, by combining experiments that cover 29 orders of magnitude in frequency. These include Planck observations of cosmic microwave background temperature and polarization power spectra and lensing, together with baryon acoustic oscillations and big bang nucleosynthesis measurements, as well as new pulsar timing array and ground-based interferometer limits. While individual experiments constrain the gravitational-wave energy density in specific frequency bands, the combination of experiments allows us to constrain cosmological parameters, including the inflationary spectral index nt and the tensor-to-scalar ratio r . Results from individual experiments include the most stringent nanohertz limit of the primordial background to date from the Parkes Pulsar Timing Array, ΩGW(f)<2.3×10−10 . Observations of the cosmic microwave background alone limit the gravitational-wave spectral index at 95% confidence to nt≲5 for a tensor-to-scalar ratio of r=0.11 . However, the combination of all the above experiments limits nt<0.36 . Future Advanced LIGO observations are expected to further constrain nt<0.34 by 2020. When cosmic microwave background experiments detect a nonzero r , our results will imply even more stringent constraints on nt and, hence, theories of the early Universe.

Pulsar timing arrays (PTAs) are designed to detect nanohertz-frequency gravitational waves (GWs). Since GWs are anticipated from cosmic strings, PTAs offer a viable approach to testing their existence. We present the results of the first Bayesian search for gravitational-wave bursts from cosmic string cusps (GWCSs) using the third PPTA data release for 30 ms pulsars. In this data collection, we find no evidence for GWCS signals. We compare a model with a GWCS signal to one with only noise, including a common spatially uncorrelated red noise (CURN), and find that our data are more consistent with the noise-only model. We then establish upper limits on the strain amplitude of GWCSs at the pulsar term, based on the analysis of 30 ms pulsars, after finding no compelling evidence. We find the addition of a CURN with different spectral indices into the noise model has a negligible impact on the upper limits. And the upper limit range of the amplitude of the pulsar-term GWCSs is concentrated between 10−12 and 10−11. Finally, we set upper limits on the amplitude of GWCS events, parametrized by width and event epoch, for a single-pulsar PSR J1857 + 0943. Moreover, we derive the upper limit on the cosmic string tension as a function of burst width and compare it with previous results.

In the centenary year of Einstein＇s General Theory of Relativity, this paper reviews the current status of gravitational wave as- tronomy across a spectrum which stretches from attohertz to kilohertz frequencies. Sect. 1 of this paper reviews the historical development of gravitational wave astronomy from Einstein＇s first prediction to our current understanding the spectrum. It is shown that detection of signals in the audio frequency spectrum can be expected very soon, and that a north-south pair of next generation detectors would provide large scientific benefits. Sect. 2 reviews the theory of gravitational waves and the principles of detection using laser interferometry. The state of the art Advanced LIGO detectors are then described. These detectors have a high chance of detecting the first events in the near future. Sect. 3 reviews the KAGRA detector currently under development in Japan, which will be the first laser interferometer detector to use cryogenic test masses. Sect. 4 of this paper reviews gravitational wave detection in the nanohertz frequency band using the technique of pulsar timing. Sect. 5 reviews the status of gravitational wave detection in the attohertz frequency band, detectable in the polarisation of the cosmic microwave background, and discusses the prospects for detection of primordial waves from the big bang. The techniques described in sects. 1-5 have already placed signifi- cant limits on the strength of gravitational wave sources. Sects. 6 and 7 review ambitious plans for future space based gravitational wave detectors in the millihertz frequency band. Sect. 6 presents a roadmap for development of space based gravitational wave detectors by China while sect. 7 discusses a key enabling technology for space interferometry known as time delay interferometry.

The heat exchange pipes in one synthetic ammonia plant were in use for only thirteen months, but obvious leakage occurred in the pipes. Investigations indicated that corrosion of the pipes was quite serious, resulting in corrosion pits penetrating the pipes in some spots. Analysis on the metallurgical structure indicated that no problems existed on the pipe material AISI 1020 low carbon steel; the corrosion inhibitors or scale inhibitors were added in the circulating water. The only problem was deduced to exist in the maintenance of the pipes during the idling period; survey of the maintenance of the pipes during the idling period proved the deduction above. Since no effective measures were taken to protect the pipes in the coolers and the circulating water was not emptied, the corrosion products and scales deposited on the pipes and formed local occluded cells; the occluded cells accelerated the pitting corrosion of the pipes and induced leakage in a short time.

Job crafting is the process of individuals redefining and adjusting their job in personally meaningful ways to improve their work experience. In this multiple case study, we explore how a group of kindergarten teachers conducted job crafting and examine its potential outcomes. Based on criterion sampling and purposeful selection, we recruit 28 kindergarten teachers and four principals working in Shanghai, China. Qualitative interviews and the analysis of kindergarten teachers’ diaries and work documents demonstrate that kindergarten teachers are not necessarily passive recipients of job characteristics; instead, they have the potential to be proactive agents in their work. Teachers craft their jobs in four main ways: task crafting, relational crafting, cognitive crafting, and work-life crafting. In addition, they employ 12 specific crafting techniques. The interviews reveal that by aligning work with teachers’ abilities, needs, and preferences, job crafting can help improve kindergarten teachers’ work experience and reduce occupational dysfunction. The results call for more focus on individual teachers’ discretionary and extra-role work behaviors. The findings have implications for policymakers, administrators, and principals in considering crafting a new pathway to increase staff stability, reduce teacher attrition, and improve education quality in early childhood settings. Some potential side effects of job crafting and precautionary strategies are also discussed.

The birth-mass function of neutron stars encodes rich information about supernova explosions, double-star evolution and the properties of matter under extreme conditions. To date, it has remained poorly constrained by observations, however. Applying probabilistic corrections to account for mass accreted by recycled pulsars in binary systems to mass measurements of 90 neutron stars, we find that the birth masses of neutron stars can be described by a unimodal distribution that smoothly turns on at 1.1  M ⊙ and peaks at ~1.27  M ⊙ , before declining as a steep power law. Such a ‘turn-on’ power-law distribution is strongly favoured against the widely adopted empirical double-Gaussian model at the 3 σ level. The power-law shape may be inherited from the initial mass function of massive stars, but the relative dearth of massive neutron stars implies that single stars with initial masses greater than ~18  M ⊙ do not form neutron stars, in agreement with the absence of massive red supergiant progenitors of supernovae. The neutron star birth-mass function, based on 90 mass measurements, shows a unimodal turn-on power-law shape peaking at 1.27 solar masses. This model links supernova progenitors and binary evolution to observed mass constraints.

A gravitational-wave background (GWB) arising from the superposition of numerous unresolved gravitational-wave signals has yet to be detected. Potential contributing sources to such a background include compact binary coalescences (CBCs) and core-collapse supernovae (CCSNe). In this work, we place upper limits on the gravitational-wave energy emitted by CCSNe using cross-correlation measurements made with Advanced LIGO and Advanced Virgo detectors during their third observing run. Specifically, we obtain a \\(95\\%\\) credibility upper limit of \\(0.01~ M_ c^2\\) while accounting for the contribution from CBC sources to a GWB. This result improves on previous constraint obtained from initial LIGO data by approximately two orders of magnitude. We also explore the detection prospects of third-generation ground-based detectors such as the Einstein Telescope and Cosmic Explorer for both individual CCSNe events and the GWB. Our results show that single events are likely to be detected prior to the GWB.

A gravitational-wave background (GWB) arising from the superposition of numerous unresolved gravitational-wave signals has yet to be detected. Potential contributing sources to such a background include compact binary coalescences (CBCs) and core-collapse supernovae (CCSNe). In this work, we place upper limits on the gravitational-wave energy emitted by CCSNe using cross-correlation measurements made with Advanced LIGO and Advanced Virgo detectors during their third observing run (O3). Specifically, we obtain a \\(95\\%\\) credibility upper limit of \\(0.01~ M_ c^2\\) while accounting for the contribution from CBC sources to a GWB. This result improves on previous constraint obtained from initial LIGO data by approximately two orders of magnitude. We also explore the detection prospects of third-generation ground-based detectors such as the Einstein Telescope and Cosmic Explorer for both individual CCSNe events and the GWB. Our results show that single events are likely to be detected prior to the GWB.

We present a comprehensive re-evaluation of pulsar radio spectra using the largest curated dataset of calibrated flux densities to date, comprising 897 pulsars, and employing a robust Bayesian framework for model comparison alongside frequentist methods. Contrary to the established consensus that pulsar spectra are predominantly simple power laws, our analysis reveals that complex spectral shapes with curvature or breaks are in fact the norm. The broken power law emerges as the most common spectral shape, accounting for 60\\% of pulsars, while the simple power law describes only 13.5\\%, with 68.8\\% of pulsars decisively favoring curved or broken models. We further identify 74 confident gigahertz-peaked spectrum pulsars, and demonstrate that millisecond pulsars frequently exhibit spectral curvature. A key finding is that the previously reported dominance of the simple power law was largely a statistical artifact of the frequentist method used in earlier work. These findings substantially revise the prevailing view of pulsar spectra and establish a critical, model-classified foundation for future theoretical work.

Pulsar Timing Arrays (PTAs) are rapidly advancing toward the detection of continuous gravitational waves from individual supermassive binary black holes. While it is well established that coherently utilizing the ``pulsar term\" requires astrometric distance uncertainties to be smaller than the gravitational wavelength, achieving this precision across an entire array is observationally prohibitive. Here, we demonstrate that achieving sub-wavelength precision for a few ``anchor\" pulsars is sufficient to phase-lock the array and drastically shrink the sky-localization error. Using 20 years of realistically simulated data, we systematically evaluate the localization performance of a 25-pulsar array containing three to six high-precision anchors. We show that while introducing three sub-wavelength anchors can reduce the 90\\% credible sky area by a factor of 30 in certain directions, expanding this high-precision subset to six anchor pulsars ensures high-precision localizations across diverse source directions. Evaluating a representative set of sky directions, including local galaxy clusters and the locations of maximum and minimum array sensitivity, this six-anchor configuration yields 90\\% credible localization areas ranging from \\( 0.1\\) to \\(9.2 deg^2\\) at a signal-to-noise ratio of 20. Furthermore, once this minimal subset crosses the sub-wavelength threshold, further reductions in distance uncertainty yield diminishing returns. This establishes a highly efficient near-term observational strategy: prioritizing intensive parallax campaigns for a small core of stable millisecond pulsars provides a cost-effective pathway to precision multi-messenger astronomy.