Jointly setting upper limits on multiple components of an anisotropic stochastic gravitational-wave background

With the increasing sensitivities of the gravitational wave (GW) detectors and more detectors joining the international network, the chances of detection of a stochastic GW background (SGWB) are progressively increasing. Different astrophysical and cosmological processes are likely to give rise to backgrounds with distinct spectral signatures and distributions on the sky. The observed SGWB will therefore be a superposition of these components. Hence, one of the first questions that will come up after the first detection of a SGWB will likely be about identifying the dominant components and their distributions on the sky. Both these questions were addressed separately in the literature, namely, how to separate components of isotropic backgrounds and how to probe the anisotropy of a single component. Here, we address the question of how to separate distinct anisotropic backgrounds with (sufficiently) different spectral shapes. We first obtain the combined Fisher information matrix from folded data using an efficient analysis pipeline PyStoch, which incorporates covariances between pixels and spectral indices. This is necessary for estimating the detection statistic and setting upper limits. However, based on a recent study, we ignore the pixel-to-pixel noise covariance that does not have a significant effect on the results at the present sensitivity levels of the detectors. We show that the joint analysis accurately separates and estimates backgrounds with different spectral shapes and different sky distributions with no major bias. This does come at the cost of increased variance. Thus making the joint upper limits safer, though less strict than the individual analysis. We finally set joint upper limits on the multicomponent anisotropic background using Advanced LIGO data taken up to the first half of the third observing run.Comment: 14 pages, 10 figures, 2 table

Source anisotropies and pulsar timing arrays

Pulsar timing arrays (PTA) hunt for gravitational waves (GW) by searching for the correlations that GWs induce in the time-of-arrival residuals from different pulsars. If the GW sources are of astrophysical origin, then they are located at discrete points on the sky. However, PTA data are often modeled, and subsequently analyzed, via a standard Gaussian ensemble . That ensemble is obtained in the limit of an infinite density of vanishingly weak, Poisson-distributed sources. In this paper, we move away from that ensemble, to study the effects of two types of source anisotropy . The first (a), which is often called shot noise , arises because there are N discrete GW sources at specific sky locations. The second (b) arises because the GW source positions are not a Poisson process, for example, because galaxy locations are clustered. Here, we quantify the impact of (a) and (b) on the mean and variance of the pulsar-averaged Hellings and Downs correlation. For conventional PTA sources, we show that the effects of shot noise (a) are much larger than the effects of clustering (b)

Bayesian parameter estimation for targeted anisotropic gravitational-wave background

Extended sources of the stochastic gravitational backgrounds have been conventionally searched on the spherical harmonics bases. The analysis during the previous observing runs by the ground-based gravitational-wave detectors, such as LIGO and Virgo, have yielded the constraints on the angular power spectrum Cℓ, yet it lacks the capability of estimating other parameters such as a spectral index. In this paper, we introduce an alternative Bayesian formalism to search for such stochastic signals with a particular distribution of anisotropies on the sky. This approach provides a Bayesian posterior of model parameters and also enables selection tests among different signal models. While the conventional analysis fixes the highest angular scale a priori, here we show a more systematic and quantitative way to determine the cutoff scale based on a Bayes factor, which depends on the amplitude and the angular scale of observed signals. Also, we analyze the third observing runs of LIGO and Virgo for the population of millisecond pulsars and obtain the 95% constraints of the signal amplitude, ϵ<2.7×10-8PGC2018-094773-B-C32, CEX2020-001007-

Targeted search for the stochastic gravitational-wave background from the galactic millisecond pulsar population

The millisecond pulsars, old-recycled objects spinning with high frequency $\mathcal{O}$(kHz) sustaining the deformation from their spherical shape, may emit gravitational-waves (GW). These are one of the potential candidates contributing to the anisotropic stochastic gravitational-wave background (SGWB) observable in the ground-based GW detectors. Here, we present the results from a likelihood-based targeted search for the SGWB due to millisecond pulsars in the Milky Way, by analyzing the data from the first three observing runs of Advanced LIGO and Advanced Virgo detector. We assume that the shape of SGWB power spectra and the sky distribution is known a priori from the population synthesis model. The information of the ensemble source properties, i.e., the in-band number of pulsars, $N_{obs}$ and the averaged ellipticity, $\mu_\epsilon$ is encoded in the maximum likelihood statistic. We do not find significant evidence for the SGWB signal from the considered source population. The best Bayesian upper limit with $95\%$ confidence for the parameters are $N_{obs}\leq8.8\times10^{4}$ and $\mu_\epsilon\leq1.1\times10^{-7}$, which is comparable to the bounds on mean ellipticity with the GW observations of the individual pulsars. Finally, we show that for the plausible case of $N_{obs}=40,000$, with the one year of observations, the one-sigma sensitivity on $\mu_\epsilon$ might reach $10^{-8}$ and $2.7\times10^{-9}$ for the second-generation detector network having A+ sensitivity and third-generation detector network respectively.Comment: 13 pages, 3 figures, 1 tabl

Investigating the association between tobacco use and oral health among security guards at a tertiary healthcare centre in New Delhi: a cross-sectional study

BackgroundTobacco usage is a major global public health concern, contributing to millions of deaths annually. This study focuses on security guards, an occupational group facing unique challenges, to investigate tobacco prevalence, usage patterns, and associated oral health risks.MethodsA cross-sectional study was conducted among security guards at a Tertiary Health Care Centre, from October 2022 to February 2023. Data on demographics, tobacco habits, and comorbidities were collected via a structured questionnaire. Clinical oral examinations provisionally diagnosed Oral Potentially Malignant Disorders (OPMDs) based on clinical findings. Appropriate Statistical analyses were employed.ResultsAmong 696 security guards, 40.1% used tobacco, including 15.0% smokers and 74.5% engaging in smokeless tobacco. Additionally, 10.3% reported using both smoking and smokeless forms. Non-tobacco users accounted for 59.9%. Tobacco users showed a higher prevalence of OPMDs (11.4%) compared to non-tobacco users (1.4%).DiscussionSecurity guards demonstrated a higher tobacco prevalence, with smokeless tobacco being predominant. Gender disparities in tobacco use emphasize the need for gender-specific interventions. The study highlights the significant impact of tobacco on oral health, especially the risk of OPMDs.ConclusionA high prevalence of tobacco usage (40.1%), particularly smokeless tobacco, among security guards, emphasizes the importance of targeted interventions within this occupational group. Oral Potentially Malignant Disorders (OPMDs) were significantly more prevalent (11.4%) in tobacco users. The association between tobacco usage and OPMDs reaffirms the well-established association between tobacco and adverse oral health outcomes

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Thyroid Cytology in India: Contemporary Review and Meta-analysis

Fine-needle aspiration cytology (FNAC) is a screening test for triaging thyroid nodules, aiding in subsequent clinical management. However, the advantages have been overshadowed by the multiplicity of reporting systems and a wide range of nomenclature used. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) was formulated in 2007, to give the world a uniform thyroid cytology reporting system, facilitating easy interpretation by the clinicians. Here, we review the status of thyroid FNAC in India in terms of various reporting systems used including a meta-analysis of the previously published data. An extensive literature search was performed using internet search engines. The reports with detailed classification system used in thyroid cytology were included. The meta-analysis of published data was compared with the implied risk of malignancy by TBSRTC. More than 50 studies were retrieved and evaluated. TBSRTC is currently the most widely used reporting system with different studies showing good efficacy and interobserver concordance. Ancillary techniques have, as of now, limited applicability and acceptability in thyroid cytology in India. Twenty-eight published articles met the criteria for inclusion in the meta-analysis. When compared with TBSRTC recommendations, the meta-analysis showed a higher risk of malignancy for categories I and III. Thyroid FNAC is practiced all over India. TBSRTC has found widespread acceptance, with most institutions using this system for routine thyroid cytology reporting. However, reasons for a high malignancy risk for categories I and III need to be looked into. Various possible contributing factors are discussed in the review