Non-linear instability of Kerr-type Cauchy horizons

Using the general solution to the Einstein equations on intersecting null surfaces developed by Hayward, we investigate the non-linear instability of the Cauchy horizon inside a realistic black hole. Making a minimal assumption about the free gravitational data allows us to solve the field equations along a null surface crossing the Cauchy Horizon. As in the spherical case, the results indicate that a diverging influx of gravitational energy, in concert with an outflux across the CH, is responsible for the singularity. The spacetime is asymptotically Petrov type N, the same algebraic type as a gravitational shock wave. Implications for the continuation of spacetime through the singularity are briefly discussed.Comment: 11 pages RevTeX, two postscript figures included using epsf.st

Saline in Acute Bronchiolitis RCT and Economic evaluation: hypertonic saline in acute bronchiolitis - randomised controlled trial and systematic review

BACKGROUND: Acute bronchiolitis is the most common cause of hospitalisation in infancy. Supportive care and oxygen are the cornerstones of management. A Cochrane review concluded that the use of nebulised 3% hypertonic saline (HS) may significantly reduce the duration of hospitalisation. OBJECTIVE: To test the hypothesis that HS reduces the time to when infants were assessed as being fit for discharge, defined as in air with saturations of > 92% for 6 hours, by 25%. DESIGN: Parallel-group, pragmatic randomised controlled trial, cost-utility analysis and systematic review. SETTING: Ten UK hospitals. PARTICIPANTS: Infants with acute bronchiolitis requiring oxygen therapy were allocated within 4 hours of admission. INTERVENTIONS: Supportive care with oxygen as required, minimal handling and fluid administration as appropriate to the severity of the disease, 3% nebulised HS every ± 6 hours. MAIN OUTCOME MEASURES: The trial primary outcome was time until the infant met objective discharge criteria. Secondary end points included time to discharge and adverse events. The costs analysed related to length of stay (LoS), readmissions, nebulised saline and other NHS resource use. Quality-adjusted life-years (QALYs) were estimated using an existing utility decrement derived for hospitalisation in children, together with the time spent in hospital in the trial. DATA SOURCES: We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials and other databases from inception or from 2010 onwards, searched ClinicalTrials.gov and other registries and hand-searched Chest, Paediatrics and Journal of Paediatrics to January 2015. REVIEW METHODS: We included randomised/quasi-randomised trials which compared HS versus saline (± adjunct treatment) or no treatment. We used a fixed-effects model to combine mean differences for LoS and assessed statistical heterogeneity using the I (2) statistic. RESULTS: The trial randomised 158 infants to HS (n = 141 analysed) and 159 to standard care (n = 149 analysed). There was no difference between the two arms in the time to being declared fit for discharge [median 76.6 vs. 75.9 hours, hazard ratio (HR) 0.95, 95% confidence interval (CI) 0.75 to 1.20] or to actual discharge (median 88.5 vs. 88.7 hours, HR 0.97, 95% CI 0.76 to 1.23). There was no difference in adverse events. One infant developed bradycardia with desaturation associated with HS. Mean hospital costs were £2595 and £2727 for the control and intervention groups, respectively (p = 0.657). Incremental QALYs were 0.0000175 (p = 0.757). An incremental cost-effectiveness ratio of £7.6M per QALY gained was not appreciably altered by sensitivity analyses. The systematic review comprised 15 trials (n = 1922) including our own. HS reduced the mean LoS by -0.36 days (95% CI -0.50 to -0.22 days). High levels of heterogeneity (I (2) = 78%) indicate that the result should be treated cautiously. CONCLUSIONS: In this trial, HS had no clinical benefit on LoS or readiness for discharge and was not a cost-effective treatment for acute bronchiolitis. Claims that HS achieves small reductions in LoS must be treated with scepticism. FUTURE WORK: Well-powered randomised controlled trials of high-flow oxygen are needed. STUDY REGISTRATION: This study is registered as NCT01469845 and CRD42014007569. FUNDING DETAILS: This project was funded by the NIHR Health Technology Assessment (HTA) programme and will be published in full in Health Technology Assessment; Vol. 19, No. 66. See the HTA programme website for further project information

Analyzing a fake news authorship network

This project synthesizes a set of 246 fake news websites previously identified in three earlier research projects. From this dataset, we extract a set of all authors who have written for these sites in 2016. This authorcentric dataset is itself a contribution that will allow future analysis of the fake news ecosystem. Based on the data we collected, we construct a network of fake news sites, linking them if they shared a common author. Our analysis shows a tight cluster of author-sharing sites, with a small core set of sites sharing dozens of authors

Search for the Chiral Magnetic Effect in Au+Au collisions at sNN=27\sqrt{s_{_{\rm{NN}}}}=27 GeV with the STAR forward Event Plane Detectors

A decisive experimental test of the Chiral Magnetic Effect (CME) is considered one of the major scientific goals at the Relativistic Heavy-Ion Collider (RHIC) towards understanding the nontrivial topological fluctuations of the Quantum Chromodynamics vacuum. In heavy-ion collisions, the CME is expected to result in a charge separation phenomenon across the reaction plane, whose strength could be strongly energy dependent. The previous CME searches have been focused on top RHIC energy collisions. In this Letter, we present a low energy search for the CME in Au+Au collisions at $\sqrt{s_{_{\rm{NN}}}}=27$ GeV. We measure elliptic flow scaled charge-dependent correlators relative to the event planes that are defined at both mid-rapidity $|\eta|<1.0$ and at forward rapidity $2.1 < |\eta|<5.1$. We compare the results based on the directed flow plane ($\Psi_1$) at forward rapidity and the elliptic flow plane ($\Psi_2$) at both central and forward rapidity. The CME scenario is expected to result in a larger correlation relative to $\Psi_1$ than to $\Psi_2$, while a flow driven background scenario would lead to a consistent result for both event planes[1,2]. In 10-50\% centrality, results using three different event planes are found to be consistent within experimental uncertainties, suggesting a flow driven background scenario dominating the measurement. We obtain an upper limit on the deviation from a flow driven background scenario at the 95\% confidence level. This work opens up a possible road map towards future CME search with the high statistics data from the RHIC Beam Energy Scan Phase-II.Comment: main: 8 pages, 5 figures; supplementary material: 2 pages, 1 figur

Measurement of the W+W- Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Dilepton Events

We present a measurement of the W+W- production cross section using 184/pb of ppbar collisions at a center-of-mass energy of 1.96 TeV collected with the Collider Detector at Fermilab. Using the dilepton decay channel W+W- -> l+l-vvbar, where the charged leptons can be either electrons or muons, we find 17 candidate events compared to an expected background of 5.0+2.2-0.8 events. The resulting W+W- production cross section measurement of sigma(ppbar -> W+W-) = 14.6 +5.8 -5.1 (stat) +1.8 -3.0 (syst) +-0.9 (lum) pb agrees well with the Standard Model expectation.Comment: 8 pages, 2 figures, 2 tables. To be submitted to Physical Review Letter

Combination of searches for Higgs boson pairs in pp collisions at \sqrts = 13 TeV with the ATLAS detector

This letter presents a combination of searches for Higgs boson pair production using up to 36.1 fb(-1) of proton-proton collision data at a centre-of-mass energy root s = 13 TeV recorded with the ATLAS detector at the LHC. The combination is performed using six analyses searching for Higgs boson pairs decaying into the b (b) over barb (b) over bar, b (b) over barW(+)W(-), b (b) over bar tau(+)tau(-), W+W-W+W-, b (b) over bar gamma gamma and W+W-gamma gamma final states. Results are presented for non-resonant and resonant Higgs boson pair production modes. No statistically significant excess in data above the Standard Model predictions is found. The combined observed (expected) limit at 95% confidence level on the non-resonant Higgs boson pair production cross-section is 6.9 (10) times the predicted Standard Model cross-section. Limits are also set on the ratio (kappa(lambda)) of the Higgs boson self-coupling to its Standard Model value. This ratio is constrained at 95% confidence level in observation (expectation) to -5.0 &lt; kappa(lambda) &lt; 12.0 (-5.8 &lt; kappa(lambda) &lt; 12.0). In addition, limits are set on the production of narrow scalar resonances and spin-2 Kaluza-Klein Randall-Sundrum gravitons. Exclusion regions are also provided in the parameter space of the habemus Minimal Supersymmetric Standard Model and the Electroweak Singlet Model. For complete list of authors see http://dx.doi.org/10.1016/j.physletb.2019.135103</p

Searches for lepton-flavour-violating decays of the Higgs boson in s=13\sqrt{s}=13 TeV pp\mathit{pp} collisions with the ATLAS detector

This Letter presents direct searches for lepton flavour violation in Higgs boson decays, H → eτ and H → μτ , performed with the ATLAS detector at the LHC. The searches are based on a data sample of proton–proton collisions at a centre-of-mass energy √s = 13 TeV, corresponding to an integrated luminosity of 36.1 fb−1. No significant excess is observed above the expected background from Standard Model processes. The observed (median expected) 95% confidence-level upper limits on the leptonflavour-violating branching ratios are 0.47% (0.34+0.13−0.10%) and 0.28% (0.37+0.14−0.10%) for H → eτ and H → μτ , respectively.publishedVersio

Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb⁻¹ of pp collisions at \sqrts = 13 TeV with the ATLAS experiment

A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb−1 of proton–proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tqγ coupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tuγ coupling of 36 fb (78 fb) and on the branching ratio for t→γu of 2.8×10−5 (6.1×10−5). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tcγ coupling of 40 fb (33 fb) and on the branching ratio for t→γc of 22×10−5 (18×10−5). © 2019 The Author(s

UBVRI Light curves of 44 Type Ia supernovae

We present UBVRI photometry of 44 Type la supernovae (SNe la) observed from 1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is the largest homogeneously observed and reduced sample of SNe la to date, nearly doubling the number of well-observed, nearby SNe la with published multicolor CCD light curves. The large sample of [U-band photometry is a unique addition, with important connections to SNe la observed at high redshift. The decline rate of SN la U-band light curves correlates well with the decline rate in other bands, as does the U - B color at maximum light. However, the U-band peak magnitudes show an increased dispersion relative to other bands even after accounting for extinction and decline rate, amounting to an additional ∼40% intrinsic scatter compared to the B band