分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We construct few deep generative models of gravitational waveforms based on the semi-supervising scheme of conditional autoencoders and their variational extensions. Once the training is done, we find that our best waveform model can generate the inspiral-merger waveforms of binary black hole coalescence with more than $97\%$ average overlap matched filtering accuracy for the mass ratio between $1$ and $10$. Besides, the generation time of a single waveform takes about one millisecond, which is about $10$ to $100$ times faster than the EOBNR algorithm running on the same computing facility. Moreover, these models can also help to explore the space of waveforms. That is, with mainly the low-mass-ratio training set, the resultant trained model is capable of generating large amount of accurate high-mass-ratio waveforms. This result implies that our generative model can speed up the waveform generation for the low latency search of gravitational wave events. With the improvement of the accuracy in future work, the generative waveform model may also help to speed up the parameter estimation and can assist the numerical relativity in generating the waveforms of higher mass ratio by progressively self-training.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We construct a Bayesian inference deep learning machine for parameter estimation of gravitational wave events of binaries of black hole coalescence. The structure of our deep Bayesian machine adopts the conditional variational autoencoder scheme by conditioning on both the gravitational wave strains and the variations of the amplitude spectral density (ASD) of the detector noise. We show that our deep Bayesian machine is capable of yielding posteriors compatible with the ones from the nested sampling method and better than the one without conditioning on the ASD. Our result implies that the process of parameter estimation can be accelerated significantly by deep learning even with large ASD drifting/variation. We also apply our deep Bayesian machine to the LIGO/Virgo O3 events, the result is compatible with the one by the traditional Bayesian inference method for the gravitational wave events with signal-to-noise ratios higher than typical threshold value. We also discuss some possible ways for future improvement.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-08-05
摘要: In the three-dimensional sl(N) Chern-Simons higher-spin theory, we prove that the conical surplus and the black hole solution are related by the S-transformation of the modulus of the boundary torus. Then applying the modular group on a given conical surplus solution, we generate a 'SL(2,Z)' family of smooth constant solutions. We then show how these solutions are mapped into one another by coordinate transformations that act non-trivially on the homology of the boundary torus. After deriving a thermodynamics that applies to all the solutions in the 'SL(2,Z)' family, we compute their entropies and free energies, and determine how the latter transform under the modular transformations. Summing over all the modular images of the conical surplus, we write down a (tree-level) modular invariant partition function.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We consider the spike mass density profile in a dark halo by self-consistently solving the relativistic Bondi accretion of dark matter onto a non-spining black hole of mass $M$. We assume that the dominant component of the dark matter in the halo is a Standard model gauge-singlet scalar. Its mass $m\simeq 10^{-5}{\rm eV}$ and quartic self-coupling $\lambda\lesssim10^{-19}$ are constrained to be compatible with the properties of galactic dark halos. In the hydrodynamic limit, we find that the accretion rate is bounded from below, $\dot{M}_{\rm min}=96\pi G^2M^2 m^4/\lambda\hbar^3$. Therefore, for $M=10^6~{\rm M}_\odot$ we have $\dot{M}_{\rm min}\simeq1.41\times 10^{-9}~{\rm M}_\odot~{\rm yr}^{-1}$, which is subdominant compared to the Eddington accretion of baryons. The spike density profile $\rho_0(r)$ within the self-gravitating regime cannot be fitted well by a single-power law but a double-power one. Despite that, we can fit $\rho_0(r)$ piecewise and find that $\rho_0(r) \propto r^{-1.20}$ near the sound horizon, $\rho_0(r) \propto r^{-1.00}$ towards the Bondi radius and $\rho_0(r) \propto r^{-1.08}$ for the region in between. This contrasts with more cuspy $\rho_0(r) \propto r^{-1.75}$ for dark matter with Coulomb-like self-interaction.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-08-05
摘要: Quantum decoherence is the loss of a system's purity due to its interaction with the surrounding environment. Via the AdS/CFT correspondence, we study how a system decoheres when its environment is a strongly-coupled theory. In the Feynman-Vernon formalism, we compute the influence functional holographically by relating it to the generating function of Schwinger-Keldysh propagators and thereby obtain the dynamics of the system's density matrix. We present two exactly solvable examples: (1) a straight string in a BTZ black hole and (2) a scalar probe in AdS5. We prepare an initial state that mimics Schr\"odinger's cat and identify different stages of its decoherence process using the time-scaling behaviors of R\'enyi entropy. We also relate decoherence to local quantum quenches, and by comparing the time evolution behaviors of the Wigner function and R\'enyi entropy we demonstrate that the relaxation of local quantum excitations leads to the collapse of its wave-function.
分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Poly[bis(phenoxyphosphazene)] (PBPP) and magnesium hydroxide (MH) are used as a flame retardant blend with low-density polyethylene (LDPE) for the nuclear cable. This study aims to investigate the effects of PBPP in MH-LDPE blend composites on flame retardance and electron beam irradiation. The structure, morphology, and properties of the blend composites irradiated by an electron beam to different absorbed doses were characterized. The results indicated that PBPP provides lubrication during processing. As the PBPP content in the blend increases the melt flow rate at 20 phr MH, meaning the material is easier to process. The higher the PBPP content, the higher the limiting-oxygen index. The elongation at the break of the PBPP containing composites (at 50 phr MH) was evidently higher than the non-PBPP ones at different absorbed doses by electron beam irradiation. The thermogravimetric analysis results indicated that the improved mechanical property, resulting from electron-beam irradiation, could be attributed to the consumption of PBPP.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Conditioning an accelerating structure is important, and its performance is limited by breakdown and vacuum degradation, hence the necessity of finding problem in the conditioning. In order to save time, a judging process built in the firmware layer is applied in this paper. The system using the embedded algorithm in the Field Programmable Gate Array (FPGA) locates the position of breakdown and displays the result in the user interface. Also, the system has the functions of automatic conditioning and interlock protection, which are useful during the conditioning process of an S-band accelerating structure.
分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Reversible addition-fragmentation chain transfer (RAFT) mediated grafting of acrylonitrile onto Polyethylene/Poly(ethylene terephthalate) (PE/PET) composite fibers was performed using -irradiation as the initial source at ambient temperature. Different initial concentrations of 2-cyanoprop-2-yl dithiobenzonate were used as the chain transfer agent. The kinetics of graft polymerization is in accordance with the living RAFT polymerization. The successful grafting of acrylonitrile is proved by Fourier transform infrared spectroscopy analysis. The results of monofilament tensile test show that mechanical properties of the fibers change slightly after grafting. Scanning electronic microscopy images of the fibers show that the surface of RAFT grafted fibers is smoother than that of fibers grafted conventionally.