arXiv subjects

Samuel Goldstein

Publications and source records attributed to Samuel Goldstein.

23 records · Page 2Linked to original sources

arXiv2021

Connecting galaxy evolution in clusters with their radial profiles and phase space distribution: results from the IllustrisTNG hydrodynamical simulations

We study the population of galaxies around galaxy clusters in the hydrodynamic simulation suite IllustrisTNG 300-1 to study the signatures of their evolutionary history on observable properties. We measure the radial number density profile, phase space distribution, and splashback radius for galaxies of different masses and colors over the redshift range $z=0-1$. The three primary physical effects which shape the galaxy distribution within clusters are the galaxy quenching, angular momentum distribution and dynamical friction. We find three distinct populations of galaxies by applying a Gaussian mixture model to their distribution in color and mass. They have distinct evolutionary histories and leave distinct signatures on their distribution around cluster halos. We find that low-mass red galaxies show the most concentrated distribution in clusters and the largest splashback radius, while high-mass red galaxies show a less concentrated distribution and a smaller splashback radius. Blue galaxies, which mostly quench into the low-mass red population, have the shallowest distribution within the clusters, with those on radial orbits quenched rapidly before reaching pericenter. Comparison with the distribution of galaxies from the Dark Energy Survey (DES) survey around Sunyaev-Zeldovich (SZ) clusters from the Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) surveys shows evidence for differences in galaxy evolution between simulations and data.

astro-ph.CO↗

arXiv2021

Linear and nonlinear properties of a compact high-kinetic-inductance WSi multimode resonator

The kinetic inductance (KI) of superconducting devices can be exploited for reducing the footprint of linear elements as well as for introducing nonlinearity to the circuit. We characterize the linear and nonlinear properties of a multimode resonator fabricated from amorphous tungsten silicide (WSi) with a fundamental frequency of $f_1 = 172$ MHz. We show how the multimode structure of the device can be used to extract the different quality factors and to aid the nonlinear characterization. In the linear regime the footprint is reduced by a factor of $\sim 2.9$ with standard lateral dimensions with no significant degradation of the internal quality factor compared to a similar Al device . In the nonlinear regime we observe self positive frequency shifts at low powers which can be attributed to saturation of tunneling two-level systems. The cross mode nonlinearities are described well by a Kerr model with a self-Kerr coefficient in the order of $|K_{11}|/2π\approx 1.5\times10^{-7}$ Hz/photon. These properties together with a reproducible fabrication process make WSi a promising candidate for creating linear and nonlinear circuit QED elements.

cond-mat.supr-con↗

arXiv2020

Four wave-mixing in a microstrip kinetic inductance travelling wave parametric amplifier

Superconducting quantum circuits are typically operated at low temperatures (mK), necessitating cryogenic low-noise, wide-band amplifiers for signal readout ultimately also compatible with room temperature electronics. While existing implementations partly meet these criteria, they suffer from certain limitations, such as rippled transmission spectra or limited dynamic range, some of which are caused by the lack of proper impedance matching. We develop a MIcrostrip Kinetic Inductance Travelling Wave Amplifier (MI-KITWA), exploiting the nonlinear kinetic inductance of tungsten-silicide for wave-mixing of the signal and a pump, and engineer the impedance to $50 Ω$, while decreasing the phase velocity, with benefit for the amplification. Despite losses, pumping on our device amplifies the signal by 15 dB over a 2 GHz bandwidth.

physics.app-ph↗

arXiv2019

Decoding Working Memory Load from EEG with LSTM Networks

Working memory (WM) is a mechanism that temporarily stores and manipulates information in service of behavioral goals and is a highly dynamic process. Previous studies have considered decoding WM load using EEG but have not investigated the contribution of sequential information contained in the temporal patterns of the EEG data that can differentiate different WM loads. In our study, we develop a novel method of investigating the role of sequential information in the manipulation and storage of verbal information at various time scales and localize topographically the sources of the sequential information based decodability. High density EEG (128-channel) were recorded from twenty subjects performing a Sternberg verbal WM task with varying memory loads. Long Short-Term Memory Recurrent Neural Networks (LSTM-RNN) were trained to decode memory load during encoding, retention, activity-silent, and retrieval periods. Decoding accuracy was compared between ordered data and a temporally shuffled version that retains pattern based information of the data but not temporal relation to assess the contribution of sequential information to decoding memory load. The results show that (1) decoding accuracy increases with increase in the length of the EEG time series given to the LSTM for both ordered and temporally shuffled cases, with the increase being faster for ordered than temporally shuffled time series, and (2) according to the decoding weight maps, the frontal, temporal and some parietal areas are an important source of sequential information based decodability. This study, to our knowledge, is the first study applying a LSTM-RNN approach to investigate temporal dynamics in human EEG data in encoding WM load information.

q-bio.NC↗

arXiv2017

Decoherence and Interferometric Sensitivity of BosonSampling in Superconducting Networks

Multiple bosons undergoing coherent evolution in a coupled network of sites constitute a so-called quantum walk system. The simplest example of such a two-particle interference is the celebrated Hong-Ou-Mandel interference. When scaling to larger boson numbers, simulating the exact distribution of bosons has been shown, under reasonable assumptions, to be exponentially hard. We analyze the feasibility and expected performance of a globally connected superconducting resonator based quantum walk system, using the known characteristics of state-of-the-art components. We simulate the sensitivity of such a system to decay processes and to perturbations and compare with coherent input states.

quant-ph↗