138041514
GENERATION AND CHARACTERIZATION OF 5-MICRON ELECTRON BEAM FOR PROBING OPTICAL SCALE STRUCTURES
In recent years advanced acceleration technologies have progress toward combination of electron beam, laser and optical scale dielectric structures. In present paper described generation of the electron beam probe with parameters satisfied to perform test of such optical structures.
35408696
WITNESS BUNCH ACCELERATION IN A MULTI-BUNCH PWFA ∗
We present initial experimental results showing the excitation of plasma wakefields by a train of two drive bunches. These wakefields are experienced by a trailing witness bunch that gains energy while retaining a finite energy spread. These well controlled plasma wakefield accelerator (PWFA) experiments are important to test the theory of the PWFA and serve as a testbed for techniques that will be used in high energy experiments.
117985245
Structure Formation Seeded by Cosmic Strings
We describe the results of high-resolution numerical simulations of structure formation seeded by a cosmic string network with a large dynamical range taking into account, for the first time, modifications due to the radiation-matter transition [1]. The resulting linear power spectrum of density perturbations is calculated with either cold or hot dark matter backgrounds and compared with the linear power spectrum inferred from various galaxy surveys [2]. Finally, we investigate the performance of cosmic string models in open universes and those with a non-zero cosmological constant. This direct numerical approach marks a considerable quantitative advance by incorporating important aspects of the relevant physics not included in previous treatments.
18473016
The Einstein Telescope: a third-generation gravitational wave observatory
Advanced gravitational wave interferometers, currently under realization, will soon permit the detection of gravitational waves from astronomical sources. To open the era of precision gravitational wave astronomy, a further substantial improvement in sensitivity is required. The future space-based Laser Interferometer Space Antenna and the third-generation ground-based observatory Einstein Telescope (ET) promise to achieve the required sensitivity improvements in frequency ranges. The vastly improved sensitivity of the third generation of gravitational wave observatories could permit detailed measurements of the sources' physical parameters and could complement, in a multi-messenger approach, the observation of signals emitted by cosmological sources obtained through other kinds of telescopes. This paper describes the progress of the ET project which is currently in its design study phase.
55413960
SEARCHING FOR PULSARS USING IMAGE PATTERN RECOGNITION
In the modern era of big data, many fields of astronomy are generating huge volumes of data, the analysis of which can sometimes be the limiting factor in research. Fortunately, computer scientists have developed powerful data-mining techniques that can be applied to various fields. In this paper, we present a novel artificial intelligence (AI) program that identifies pulsars from recent surveys by using image pattern recognition with deep neural nets—the PICS (Pulsar Image-based Classification System) AI. The AI mimics human experts and distinguishes pulsars from noise and interference by looking for patterns from candidate plots. Different from other pulsar selection programs that search for expected patterns, the PICS AI is taught the salient features of different pulsars from a set of human-labeled candidates through machine learning. The training candidates are collected from the Pulsar Arecibo L-band Feed Array (PALFA) survey. The information from each pulsar candidate is synthesized in four diagnostic plots, which consist of image data with up to thousands of pixels. The AI takes these data from each candidate as its input and uses thousands of such candidates to train its ~9000 neurons. The deep neural networks in this AI system grant it superior ability to recognize various types of pulsars as well as their harmonic signals. The trained AI's performance has been validated with a large set of candidates from a different pulsar survey, the Green Bank North Celestial Cap survey. In this completely independent test, the PICS ranked 264 out of 277 pulsar-related candidates, including all 56 previously known pulsars and 208 of their harmonics, in the top 961 (1%) of 90,008 test candidates, missing only 13 harmonics. The first non-pulsar candidate appears at rank 187, following 45 pulsars and 141 harmonics. In other words, 100% of the pulsars were ranked in the top 1% of all candidates, while 80% were ranked higher than any noise or interference. The performance of this system can be improved over time as more training data are accumulated. This AI system has been integrated into the PALFA survey pipeline and has discovered six new pulsars to date.
18080099
The third generation of gravitational wave observatories and their science reach
Large gravitational wave interferometric detectors, like Virgo and LIGO, demonstrated the capability to reach their design sensitivity, but to transform these machines into an effective observational instrument for gravitational wave astronomy a large improvement in sensitivity is required. Advanced detectors in the near future and third-generation observatories in more than one decade will open the possibility to perform gravitational wave astronomical observations from the Earth. An overview of the possible science reaches and the technological progress needed to realize a third-generation observatory are discussed in this paper. The status of the project Einstein Telescope (ET), a design study of a third-generation gravitational wave observatory, will be reported.
118708943
Multi-taper Spectral Analysis in Gravitational Wave Data Analysis
Spectral estimation plays a significant role in gravitational wave data analysis. We provide a brief introduction to multi-taper methods which use multiple orthogonal tapers (or windows) to provide spectral estimators with excellent bias and variance properties. Multi-taper methods are also extremely powerful for the estimation and removal of sharp spectral peaks in the presence of noise such as arise due to power line harmonics or suspension resonances. We present examples of these methods using the GRASP (Gravitational Radiation Analysis and Simulation Package) software package.