The effective potential approach for composite operators is generalized to non-zero temperatures in order to derive the equation of state for pure SU(3) Yang--Mills fields. In the absence of external ...sources, this is nothing but the vacuum energy density. The key element of this derivation is the introduction of a temperature dependence into the expression for the bag constant. The non-perturbative analytical equation of state for gluon matter does not depend on the coupling constant, but instead introduces a dependence on the mass gap. This is responsible for the large-scale structure of the QCD ground state. The important thermodynamic quantities, such as the pressure, energy and entropy densities, etc, have been calculated. We show explicitly that the pressure may vary continuously around Tc = 266.5 MeV, whereas all other thermodynamic quantities undergo drastic changes at this point. The proposed analytical approach makes it possible to control for the first time the thermodynamics of gluon matter at low temperatures, below Tc. We reproduce the properties of the so-called fuzzy bag-type models through the presence of the mass gap in our equation of state. An analytic calculation of the gluon condensate is obtained as a function of temperature.
Matra Gravitational and Geophysical Laboratory (MGGL) was established near Gyöngyösoroszi, Hungary in 2015, in the cavern system of an unused ore mine. The laboratory is located 88 m below the ...surface, with the aim of measuring and analysing the advantages of the underground installation's third generation gravitational wave detectors. Specialized instruments have been installed to measure seismic, infrasound and electromagnetic noise, and the variation of the cosmic muon flux. In the preliminary (RUN-0) test period, March-August 2016, data collection was accomplished. In this paper we describe the research potential of the MGGL, list the installed equipment and summarize the experimental results of RUN-0. Here we report on the RUN-0 data, that prepares the systematic and synchronized data collection of the next run period.
Summary of the long term data taking, related to one of the proposed next generation ground-based gravitational detector’s location is presented here. Results of seismic and infrasound noise, ...electromagnetic attenuation and cosmic muon radiation measurements are reported in the underground Matra Gravitational and Geophysical Laboratory near Gyöngyösoroszi, Hungary. The collected seismic data of more than two years is evaluated from the point of view of the Einstein Telescope, a proposed third generation underground gravitational wave observatory. Applying our results for the site selection will significantly improve the signal to noise ratio of the multi-messenger astrophysics era, especially at the low frequency regime.
Status of the Virgo project Accadia, T; Acernese, F; Antonucci, F ...
Classical and quantum gravity,
06/2011, Letnik:
28, Številka:
11
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
We describe the present state and future evolution of the Virgo gravitational wave detector, realized by the Virgo Collaboration at the European Gravitational Observatory, in Cascina near Pisa in ...Italy. We summarize basic principles of the operation and the design features of the Virgo detector. We present the sensitivity evolution due to a series of intermediate upgrades called Virgo+ which is being completed this year and includes new monolithic suspensions. We describe the present scientific potential of the detector. Finally we discuss the plans for the second generation of the detector, called Advanced Virgo, introducing its new features, the expected sensitivity evolution and the scientific potential.
The site characterisation of future underground gravitational wave detectors is based on spectral properties of the low frequency seismic noise. The evaluation of the collected long term ...seismological data in the Mátra Gravitational and Geophysical Laboratory revealed some aspects that are not apparent in short term spectral noise characterisation. In this paper we survey the methodology. In particular, we argue that the spectral properties are best represented by percentiles of the data instead of the mode, because it is noisy, sensitive to the discretization and intrinsic averaging, therefore it is less suitable for a robust characterisation. The suitable cumulative measures are also scrutinized.
Spatially homogeneous and isotropic cosmological models, with a perfect fluid matter source and non-vanishing cosmological constant, are studied. The equations governing linear perturbations of the ...space-time and the variation of energy density are given. The complete solution of the problem is obtained for $C^{\infty}$ perturbations, using a comoving time. The Sachs-Wolfe fluctuations of the temperature of the cosmic background radiation are obtained for the relatively growing density perturbations. It is found that the observable celestial microwave fluctuation pattern underwent a reversal approximately two billion years ago. What is observed today is a negative image of the last scattering surface with an attenuation of the fluctuations, due to the presence of the cosmological constant.
Current interferometric gravitational-wave detectors are limited by quantum noise over a wide range of their measurement bandwidth. One method to overcome the quantum limit is the injection of ...squeezed vacuum states of light into the interferometer's dark port. Here, we report on the successful application of this quantum technology to improve the shot noise limited sensitivity of the Advanced Virgo gravitational-wave detector. A sensitivity enhancement of up to 3.2±0.1 dB beyond the shot noise limit is achieved. This nonclassical improvement corresponds to a 5%-8% increase of the binary neutron star horizon. The squeezing injection was fully automated and over the first 5 months of the third joint LIGO-Virgo observation run O3 squeezing was applied for more than 99% of the science time. During this period several gravitational-wave candidates have been recorded.
The stochastic gravitational-wave background is a superposition of sources that are either too weak or too numerous to detect individually. In this study, we present the results from a ...cross-correlation analysis on data from Advanced LIGO's second observing run (O2), which we combine with the results of the first observing run (O1). We do not find evidence for a stochastic background, so we place upper limits on the normalized energy density in gravitational waves at the 95% credible level of ΩGW<6.0×10−8 for a frequency-independent (flat) background and ΩGW<4.8×10−8 at 25 Hz for a background of compact binary coalescences. The upper limit improves over the O1 result by a factor of 2.8. Additionally, we place upper limits on the energy density in an isotropic background of scalar- and vector-polarized gravitational waves, and we discuss the implication of these results for models of compact binaries and cosmic string backgrounds. Finally, we present a conservative estimate of the correlated broadband noise due to the magnetic Schumann resonances in O2, based on magnetometer measurements at both the LIGO Hanford and LIGO Livingston observatories. We find that correlated noise is well below the O2 sensitivity.
We present the results from three gravitational-wave searches for coalescing compact binaries with component masses above1M⊙during the first and second observing runs of the advanced ...gravitational-wave detector network. During the first observing run (O1), from September 12, 2015 to January 19, 2016, gravitational waves from three binary black hole mergers were detected. The second observing run (O2), which ran from November 30, 2016 to August 25, 2017, saw the first detection of gravitational waves from a binary neutron star inspiral, in addition to the observation of gravitational waves from a total of seven binary black hole mergers, four of which we report here for the first time: GW170729, GW170809, GW170818, and GW170823. For all significant gravitational-wave events, we provide estimates of the source properties. The detected binary black holes have total masses between18.6−0.7+3.2M⊙and84.4−11.1+15.8M⊙and range in distance between320−110+120and2840−1360+1400Mpc. No neutron star–black hole mergers were detected. In addition to highly significant gravitational-wave events, we also provide a list of marginal event candidates with an estimated false-alarm rate less than 1 per 30 days. From these results over the first two observing runs, which include approximately one gravitational-wave detection per 15 days of data searched, we infer merger rates at the 90% confidence intervals of110−3840Gpc−3y−1for binary neutron stars and9.7−101Gpc−3y−1for binary black holes assuming fixed population distributions and determine a neutron star–black hole merger rate 90% upper limit of610Gpc−3y−1.
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