16423131
Systematic distortion in cosmic microwave background maps
To minimize instrumentally the induced systematic errors, cosmic microwave background (CMB) anisotropy experiments measure temperature differences across the sky using pairs of horn antennas, temperature map is recovered from temperature difference obtained in sky survey through a map-making procedure. To inspect and calibrate residual systematic errors in the recovered temperature maps is important as most previous studies of cosmology are based on these maps. By analyzing pixel-ring coupling and latitude dependence of CMB temperatures, we find notable systematic deviation from CMB Gaussianity in released Wilkinson Microwave Anisotropy Probe (WMAP) maps. The detected deviation cannot be explained by the best-fit LCDM cosmological model at a confidence level above 99% and cannot be ignored for a precision cosmology study.
56439385
On the relation of hard X-ray peak flux and outburst waiting time in the black hole transient GX 339-4
Aims. We reinvestigate the empirical relation between the hard X-ray peak flux and the outburst waiting time found previously in the black hole transient GX 339-4. We verify the relation using the observed hard X-ray peak flux of the 2007 outburst of GX 339-4, we clarify the nature of faint flares, and we estimate the lower limit to hard X-ray peak flux of the next outburst.
121381895
Abnormal correlation in WMAP data: parity violation or data flaw?
The cosmic microwave background (CMB) temperature maps and the corresponding results published by the Wilkinson Microwave Anisotropy Probe (WMAP) team are the basis of precision cosmology. However, in our previous work, they have been questioned: it is discovered that the WMAP CMB temperatures are correlated with the number of observations (N-obs) (Li et al 2009 Mon. Not. R. Astron. Soc. 398 47). We have repeated this finding with a much simpler method and found more interesting attributes of the temperature-N-obs correlation. What is more, with our method, we have also found significant correlations between the CMB intensity and polarization components. With these results, either the law of parity conservation may be violated in the early universe or there may be a flaw in the WMAP data.
17242777
TEMPORAL AND SPECTRAL CORRELATIONS OF CYGNUS X-1
Temporal and spectral properties of X-ray rapid variability of Cyg X-l are studied through correlation analysis in the time domain on different timescales. The correlation coefficients between the total intensity in the 2-60 keV band and the hardness ratio of the 13-60 keV to the 2-6 keV band on the timescale of similar to 1 ms are always negative in all states. For soft states, the correlation coefficients are positive on all timescales from similar to 0.01 to similar to 100 s, which is significantly different from those for transition and low states. The temporal structures in the high-energy band are narrower than those in low-energy band in quite a few cases. The delay of high-energy photons relative to low-energy ones in the X-ray variations has also been revealed by the correlation analysis. The implications of the observed temporal and spectral characteristics for the production region and mechanism of Cyg X-l X-ray variations are discussed.
118555439
Attraction-repulsion coupled and energy conserved universe
The discovery of accelerated cosmic expansion implies that, in addition to the attractive gravity of matter, there exists in our universe some other form of energy (dark energy or cosmological constant) producing a repulsive force. The natural interpretation of dark energy is the vacuum energy. However, the density of vacuum energy expected by the quantum field theory is 120 orders of magnitude larger than what is allowed by cosmological observations, which is called the cosmological constant problem and remains one of the most significant unsolved problems in fundamental physics. Here we show that the huge discrepancy can be resolved by assuming that our universe is an attraction-repulsion coupled system with energy conservation, and that the pre-inflation vacuum is in equilibrium between attraction and repulsion (in flat Minkowski spacetime, not de Sitter or anti de Sitter). The attraction-repulsion coupling picture can also easily explain why both kinds of energy in our universe have similar magnitude today, and avoid singularity problems in general relativity and cosmology.
16231433
Temporal and spectral properties of gamma-ray flashes
[1] The temporal and spectral properties of terrestrial gamma-ray flashes (TGFs) are studied. The delay of low energy photons relative to high energy ones in the γ-ray variations of the TGFs with high signal to noise ratio has been revealed by an approach of correlation analysis in the time domain on different time scales. The temporal structures of the TGFs in high energy band are usually narrower than that in low energy band. The spectral hardness has a general trend of decreasing with time in a flash. The observed temporal and spectral characteristics give constraints and valuable hints on the flash production mechanism.
119268605
An incremental approach to unravel the neutrino mass hierarchy and CP violation with a long-baseline superbeam for large θ13
A bstractRecent data from long-baseline neutrino oscillation experiments have provided new information on θ13, hinting that $ 0.0{1}\mathop{ < }\limits_{ \sim } {\text{si}}{{\text{n}}^{{2}}} $$ {2}{\theta_{{{13}}}}\mathop{ < }\limits_{ \sim } 0.{1} $ at 2 σ confidence level. In the near future, further confirmation of this result with high significance will have a crucial impact on the optimization of the future long-baseline neutrino oscillation experiments designed to probe the neutrino mass ordering and leptonic CP violation. In this context, we expound in detail the physics reach of an experimental setup where neutrinos produced in a conventional wide-band beam facility at CERN are observed in a proposed Giant Liquid Argon detector at the Pyhasalmi mine, at a distance of 2290 km. Due to the strong matter effects and the high detection efficiency at both the first and second oscillation maxima, this particular setup would have unprecedented sensitivity to the neutrino mass ordering and leptonic CP violation in the light of the emerging hints of large θ13. With a 10 to 20 kt ‘pilot’ detector and just a few years of neutrino beam running, the neutrino mass hierarchy could be determined, irrespective of the true values of δCP and the mass hierarchy, at 3 σ (5 σ) confidence level if sin2 2θ13(true) = 0.05 (0.1). With the same exposure, we start to have 3 σ sensitivity to CP violation if sin2 2θ13(true) > 0.05, in particular testing maximally CP-violating scenarios at a high confidence level. After optimizing the neutrino and anti-neutrino running fractions, we study the performance of the setup as a function of the exposure, identifying three milestones to have roughly 30%, 50% and 70% coverage in δC P (true) for 3 σ CP violation discovery. For comparison, we also study the CERN to Slanic baseline of 1540 km. This work nicely demonstrates that an incremental program, staged in terms of the exposure, can achieve the desired physics goals within a realistically feasible timescale, and produce significant new results at each stage.
23581346
Demonstrating the feasibility of probing the neutron-star equation of state with second-generation gravitational-wave detectors.
Fisher matrix and related studies have suggested that, with second-generation gravitational-wave detectors, it may be possible to infer the equation of state of neutron stars using tidal effects in a binary inspiral. Here, we present the first fully Bayesian investigation of this problem. We simulate a realistic data analysis setting by performing a series of numerical experiments of binary neutron-star signals hidden in detector noise, assuming the projected final design sensitivity of the Advanced LIGO-Virgo network. With an astrophysical distribution of events (in particular, uniform in comoving volume), we find that only a few tens of detections will be required to arrive at strong constraints, even for some of the softest equations of state in the literature. Thus, direct gravitational-wave detection will provide a unique probe of neutron-star structure.
59492998
Sensitivity studies for third-generation gravitational wave observatories
Advanced gravitational wave detectors, currently under construction, are expected to directly observe gravitational wave signals of astrophysical origin. The Einstein Telescope (ET), a third-generation gravitational wave detector, has been proposed in order to fully open up the emerging field of gravitational wave astronomy. In this paper we describe sensitivity models for ET and investigate potential limits imposed by fundamental noise sources. A special focus is set on evaluating the frequency band below 10 Hz where a complex mixture of seismic, gravity gradient, suspension thermal and radiation pressure noise dominates. We develop the most accurate sensitivity model, referred to as ET-D, for a third-generation detector so far, including the most relevant fundamental noise contributions.
59497924
Towards a generic test of the strong field dynamics of general relativity using compact binary coalescence: Further investigations
In this paper we elaborate on earlier work by the same authors in which a novel Bayesian inference framework for testing the strong-field dynamics of General Relativity using coalescing compact binaries was proposed. Unlike methods that were used previously, our technique addresses the question whether one or more 'testing coefficients' (e.g. in the phase) parameterizing deviations from GR are non-zero, rather than all of them differing from zero at the same time. The framework is well-adapted to a scenario where most sources have low signal-to-noise ratio, and information from multiple sources as seen in multiple detectors can readily be combined. In our previous work, we conjectured that this framework can detect generic deviations from GR that can in principle not be accomodated by our model waveforms, on condition that the change in phase near frequencies where the detectors are the most sensitive is comparable to that induced by simple shifts in the lower-order phase coefficients of more than a few percent (~ 5 radians at 150 Hz). To further support this claim, we perform additional numerical experiments in Gaussian and stationary noise according to the expected Advanced LIGO/Virgo noise curves, and coherently injecting signals into the network whose phasing differs structurally from the predictions of GR, but with the magnitude of the deviation still being small. We find that even then, a violation of GR can be established with good confidence.
118632100
Determination of Dark Energy by the Einstein Telescope: Comparing with CMB, BAO and SNIa Observations
A design study is currently in progress for a third-generation gravitational-wave (GW) detector called the Einstein Telescope (ET). An important kind of source for ET will be the inspiral and merger of binary neutron stars up to $z\ensuremath{\sim}2$. If binary neutron star mergers are the progenitors of short-hard $\ensuremath{\gamma}$-ray bursts, then some fraction of them will be seen both electromagnetically and through GW, so that the luminosity distance and the redshift of the source can be determined separately. An important property of these ``standard sirens'' is that they are self-calibrating: the luminosity distance can be inferred directly from the GW signal, with no need for a cosmic distance ladder. Thus, standard sirens will provide a powerful independent check of the $\ensuremath{\Lambda}\mathrm{CDM}$ model. In previous work, estimates were made of how well ET would be able to measure a subset of the cosmological parameters (such as the dark energy parameter ${w}_{0}$) it will have access to, assuming that the others had been determined to great accuracy by alternative means. Here we perform a more careful analysis by explicitly using the potential Planck cosmic microwave background data as prior information for these other parameters. We find that ET will be able to constrain ${w}_{0}$ and ${w}_{a}$ with accuracies $\ensuremath{\Delta}{w}_{0}=0.099$ and $\ensuremath{\Delta}{w}_{a}=0.302$, respectively. These results are compared with projected accuracies for the JDEM baryon acoustic oscillations project and the SNAP type Ia supernovae observations.