A5071649843- Radio Astronomy Observations and Technology
- Antenna Design and Optimization
- Astrophysics and Cosmic Phenomena
- Microwave Engineering and Waveguides
- Cosmology and Gravitation Theories
- Galaxies: Formation, Evolution, Phenomena
- Black Holes and Theoretical Physics
- Superconducting and THz Device Technology
- Antenna Design and Analysis
- Pulsars and Gravitational Waves Research
- Radio Wave Propagation Studies
- Advanced Adaptive Filtering Techniques
- Geophysics and Gravity Measurements
- Scientific Research and Discoveries
- Advanced Antenna and Metasurface Technologies
- Direction-of-Arrival Estimation Techniques
- Radar Systems and Signal Processing
- Astrophysical Phenomena and Observations
- Satellite Communication Systems
- Advanced Image Processing Techniques
- Radio Frequency Integrated Circuit Design
- Electromagnetic Compatibility and Measurements
- Space Satellite Systems and Control
- GNSS positioning and interference
- Image Processing Techniques and Applications
University of Oxford
2014-2025
University of Malta
2015-2025
Osservatorio Astrofisico di Catania
2020-2024
Queen Mary University of London
2021
National Institute for Astrophysics
2021
Borough of Manhattan Community College
2016
City University of New York
2016
Rhodes University
2014
We present first results from the third GRavitational lEnsing Accuracy Testing (GREAT3) challenge, in a sequence of challenges for testing methods inferring weak gravitational lensing shear distortions simulated galaxy images. GREAT3 was divided into experiments to test three specific questions, and included space- ground-based data with constant or cosmologically varying fields. The simplest (control) experiment parametric galaxies realistic distribution signal-to-noise, size, ellipticity,...
We report on the MIT Epoch of Reionization (MITEoR) experiment, a pathfinder low-frequency radio interferometer whose goal is to test technologies that improve calibration precision and reduce cost high-sensitivity 3D mapping required for 21 cm cosmology. MITEoR accomplishes this by using massive baseline redundancy, which enables both automated correlator reduction. demonstrate quantify power robustness redundancy scalability precision. find parameters precisely describe effect instrument...
Abstract In this work, we use a combined approach of Hubble parameter data together with redshift-space-distortion ( f σ 8 ) data, which are used to reconstruct the teleparallel gravity (TG) Lagrangian via Gaussian processes (GP). The adopted mainly comes from cosmic chronometers, while for Type Ia supernovae latest jointly calibrated Pantheon compilation. Moreover, consider two main GP covariance functions, namely squared-exponential and Cauchy kernels in order show consistency (to within...
The prospect of nonparametric reconstructions cosmological parameters from observational data sets has been a popular topic in the literature for number years. This mainly taken form technique based on Gaussian processes but this approach is exposed to several foundational issues ranging overfitting kernel consistency problems. In work, we explore possibility using artificial neural networks (ANN) reconstruct late-time expansion and large scale structure parameters. We first show how mock...
The identification and subsequent discovery of fast radio transients using blind-search surveys require a large amount processing power, in worst cases scaling as . For this reason, survey data are generally processed off-line, high-performance computing architectures or hardware-based designs. In recent years, graphics units (GPUs) have been extensively used for numerical analysis scientific simulations, especially after the introduction new high-level application programming interfaces....
Following the reported detection of an absorption profile associated with 21[Formula: see text]cm sky-averaged signal from Cosmic Dawn by EDGES experiment in 2018, a number experiments have been set up to verify this result. This paper discusses design process used for global experiments, focusing specifically on Radio Experiment Analysis Hydrogen (REACH). will seek understand and compensate systematic errors present using detailed modeling characterization instrumentation. Detailed...
The design and development process for the Square Kilometre Array (SKA) radio telescope’s Low Frequency Aperture component was progressed during SKA pre-construction phase by an international consortium, with goal of meeting requirements a critical review. As part full-sized prototype ‘station’ deployed – Verification System 1 (AAVS1). We provide system overview describe commissioning results AAVS1, which is low frequency telescope 256 dual-polarisation log-periodic dipole antennas working...
We detail the REACH radiometric system designed to enable measurements of 21-cm neutral hydrogen line. Included is radiometer architecture and end-to-end simulations as well a discussion challenges intrinsic highly-calibratable development. Following this, we share laboratory results based on calculation noise wave parameters utilising an over-constrained least squares approach. For five hours integration custom-made source with comparable impedance that antenna used in field, demonstrate...
It has recently been pointed out that arbitrary center-of-mass energies may be obtained for particle collisions near the horizon of an extremal Kerr black hole. We investigate this mechanism in cylindrical topology. In particular we consider a hole with rotation and charge parameter. The geodesics are first derived rotating charged producing background gravitational field. Finally is determined its limit taken.
A signal processing hardware platform has been developed for the Low Frequency Aperture Array component of Square Kilometre (SKA). The board, called an Analog Digital Unit (ADU), is able to acquire and digitize broadband (up 500[Formula: see text]MHz bandwidth) radio-frequency streams from 16 dual polarized antennas, channel data then combine them flexibly as part a larger beamforming system. It envisaged that there will be more than 8000 these platforms in first phase SKA, so particular...
Digital beamforming for the aperture array components of Square Kilometre Array (SKA) poses considerable computational challenges. We propose a hierarchical scheme aimed at tackling them and introduce OSKAR, simulator which implements these ideas algorithms. The continues to be developed investigate possible designs custom devices envisaged phase 1 SKA construction.
We present the exact exterior solution for a static and neutral cylindrically symmetric source in locally conformal invariant Weyl gravity. As special case general relativity analogue still can be attained, however only as sub-family of solutions. Our contains linear term that would thus result potential grows linearly over large distances. This may have implications exotic astrophysical structures well matter fields on extremely small scale.
We present a new method for interferometric imaging that is ideal the large fields of view and compact arrays common in 21 cm cosmology. first demonstrate with simulations two very different low-frequency interferometers, Murchison Widefield Array MIT Epoch Reionization (MITEoR) experiment. then apply to MITEoR data set collected 2013 July obtain northern sky map from 128 175 MHz at ∼2° resolution find an overall spectral index −2.73 ± 0.11. The success this bodes well upcoming redundant...
In this work, decision tree learning algorithms and fuzzy inferencing systems are applied for galaxy morphology classification. particular, the CART, C4.5, Random Forest logic studied reliable classifiers developed to distinguish between spiral galaxies, elliptical galaxies or star/unknown galactic objects. Morphology information training testing datasets is obtained from Galaxy Zoo project while corresponding photometric spectra parameters downloaded SDSS DR7 catalogue.
Using $f(R)$ gravity in the Palatini formularism, metric for a charged spherically symmetric black hole is derived, taking Ricci scalar curvature to be constant. The generalized uncertainty principle then used calculate temperature of resulting hole; through this entropy found correcting Bekenstein-Hawking case. tunneling probability and heat capacity are calculated up order Planck length, which produces an extra factor that becomes important as holes become small, such case mini-black holes.
A new digital backend has been developed for the Basic Element SKA Training II (BEST-2) array at Radiotelescopi di Medicina, INAF-IRA, Italy, which allows concurrent operation of an FX correlator, and a direct-imaging correlator beamformer. This serves as platform testing some spatial Fourier transform concepts have proposed use in computing correlations on regularly gridded arrays. While transform-based beamformers implemented previously, this is, to our knowledge, first time deployed radio...
As the amount of space debris orbiting earth is continuously increasing, it becoming essential to monitor and predict debris' trajectories in order avoid collision that could threaten missions, i.e. operative satellites or manned spacecraft. An innovative bistatic radar system, couples multi-beaming ranging techniques, proposed this work as an instrument for observation Earth-orbiting objects. The main characteristics sensor are described. In addition, tailored algorithms have been...
Considering cylindrical topology, we present the static solution for a charged black hole in conformal gravity. We show that unlike general relativistic case, there are two different solutions, both including factor which gives rise to linear term potential, also features neutral case. This may have significant ramifications particle trajectories.
Gravitomagnetic effects are characterized by two phenomena: first, the geodetic effect which describes precession of spin a gyroscope in free orbit around massive object, second, Lense-Thirring orbital plane about rotating source mass. We calculate both these fourth-order theory conformal Weyl gravity for test case circular orbits. show that linear term arises may be interesting high radial orbits, whereas additional has diminishing most Circular orbits also considered general leading up to...
The signal processing firmware that has been developed for the Low Frequency Aperture Array component of Square Kilometre is described. implemented on a dual FPGA board, capable streams from 16 polarization antennas. Data includes channelization sampled data each antenna, correction instrumental response and geometric delays formation one or more beams by combining aligned streams. channelizer uses an oversampling polyphase filterbank architecture, allowing frequency continuous input without...
Conformal Weyl gravity (CWG) predicts galactic rotation curves without invoking dark matter. This makes CWG an interesting candidate theory as alternative to general relativity (GR). removal of the necessity for matter arises because exact exterior solution in a static, spherically symmetric source provides linear potential γr, which can explain observed with value γ ∼+10−26 m−1. Previous work has also shown that lensing observations, but ∼ −10−26 m−1, order ensure converging rays light...
A violation of the distance-duality relation is directly linked with a temporal variation electromagnetic fine-structure constant. We consider number well-studied f(T) gravity models and we revise theoretical prediction their corresponding induced relationship. further extract constraints on involved model parameters through constant data, alongside supernovae Hubble parameter measurements. Moreover, constrain evolution effective gravitational Finally, compare revised phenomenological...