A wide bandwidth, dual polarized, modi¯ed four-square antenna is presented as a feed antenna for radio astronomical measurements. A linear array of these antennas is used as a line-feed for cylindrical re°ectors for Tianlai, a radio interferometer designed for 21 cm intensity mapping. Simulations of the feed antenna beam patterns and scattering parameters are compared to experimental results at multiple frequencies across the 650-1420 MHz range. Simulations of the beam patterns of the combined feed array/re°ector are presented as well.
The Tianlai Pathfinder is designed to demonstrate the feasibility of using wide field of view radio interferometers to map the density of neutral hydrogen in the Universe after the Epoch of Reionizaton. This approach, called 21 cm intensity-mapping, promises an inexpensive means for surveying the large-scale structure of the cosmos. The Tianlai Pathfinder presently consists of an array of three, 15 m × 40 m cylinder telescopes and an array of sixteen, 6 m diameter dish antennas located in a radio-quiet part of western China. The two types of arrays were chosen to determine the advantages and disadvantages of each approach. The primary goal of the Pathfinder is to make 3D maps by surveying neutral hydrogen over large areas of the sky in two different redshift ranges: first at 1.03 > z > 0.78 (700 − 800 MHz) and later at 0.21 > z > 0.12 (1170 − 1270 MHz). The most significant challenge to 21 cm intensity-mapping is the removal of strong foreground radiation that dwarfs the cosmological signal. It requires exquisite knowledge of the instrumental response, i.e. calibration. In this paper we provide an overview of the status of the Pathfinder and discuss the details of some of the analysis that we have carried out to measure the beam function of both arrays. We compare electromagnetic simulations of the arrays to measurements, discuss measurements of the gain and phase stability of the instrument, and provide a brief overview of the data processing pipeline.
We continue the search for rules that govern when off-shell 4D, $$ \mathcal{N} $$
N
= ∞ supermultiplets can be combined to form off-shell 4D, $$ \mathcal{N} $$
N
= ∈ supermultiplets. We study the 𝕊8 permutations and Height Yielding Matrix Numbers (HYMN) embedded within the adinkras that correspond to these putative off-shell 4D, $$ \mathcal{N} $$
N
= 2 supermultiplets. Even though the HYMN definition was designed to distinguish between the raising and lowering of nodes in one dimensional valise supermultiplets, they are shown to accurately select out which combinations of off-shell 4D, $$ \mathcal{N} $$
N
= 1 supermultiplets correspond to off-shell 4D, $$ \mathcal{N} $$
N
= 2 supermultiplets. Only the combinations of the chiral + vector and chiral + tensor are found to have valises in the same class. This is consistent with the well known structure of 4D, $$ \mathcal{N} $$
N
= 2 supermultiplets.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.