The Formation of Brown Dwarfs: Observations

We review the current state of observational work on the formation of brown dwarfs, focusing on their initial mass function, velocity and spatial distributions at birth, multiplicity, accretion, and circumstellar disks. The available measurements of these various properties are consistent with a common formation mechanism for brown dwarfs and stars. In particular, the existence of widely separated binary brown dwarfs and a probable isolated proto-brown dwarf indicate that some substellar objects are able to form in the same manner as stars through unperturbed cloud fragmentation. Additional mechanisms such as ejection and photoevaporation may play a role in the birth of some brown dwarfs, but there is no observational evidence to date to suggest that they are the key elements that make it possible for substellar bodies to form.Comment: Protostars and Planets V, in pres

Demonstration of non-Markovian process characterisation and control on a quantum processor

In the scale-up of quantum computers, the framework underpinning fault-tolerance generally relies on the strong assumption that environmental noise affecting qubit logic is uncorrelated (Markovian). However, as physical devices progress well into the complex multi-qubit regime, attention is turning to understanding the appearance and mitigation of correlated -- or non-Markovian -- noise, which poses a serious challenge to the progression of quantum technology. This error type has previously remained elusive to characterisation techniques. Here, we develop a framework for characterising non-Markovian dynamics in quantum systems and experimentally test it on multi-qubit superconducting quantum devices. Where noisy processes cannot be accounted for using standard Markovian techniques, our reconstruction predicts the behaviour of the devices with an infidelity of $10^{-3}$. Our results show this characterisation technique leads to superior quantum control and extension of coherence time by effective decoupling from the non-Markovian environment. This framework, validated by our results, is applicable to any controlled quantum device and offers a significant step towards optimal device operation and noise reduction

Period derivative of the M15 X-ray Binary AC211/X2127+119

We have combined Rossi X-ray Timing Explorer observations of X2127+119, the low-mass X-ray binary in the globular cluster M15, with archival X-ray lightcurves to study the stability of the 17.1 hr orbital period. We find that the data cannot be fit by the Ilovaisky (1993) ephemeris, and requires either a 7sigma change to the period or a period derivative Pdot/P~9x10e-7 per year. Given its remarkably low L_X/L_opt such a Pdot lends support to models that require super-Eddington mass transfer in a q~1 binary.Comment: 11 pages, 3 figures, to be published in New Astronom

Complete Genome Sequence of a Divergent Human Rhinovirus C Isolate from an Infant with Severe Community-Acquired Pneumonia in Colorado, USA.

Here, we report the genome sequence of a divergent human rhinovirus C isolate identified from an infant with a severe community-acquired respiratory infection. RNA sequencing performed on an Illumina platform identified reads aligning to human rhinovirus species, which were de novo assembled to produce a coding-complete genome sequence

Historical Fire In Longleaf Pine (\u3ci\u3ePinus palustris\u3c/i\u3e) Forests of South Mississippi and Its Relation to Land Use and Climate

We characterized historical fire regimes in Pinus palustris (longleaf pine) forests of southern Mississippi with regard to global and regional coupled climate systems (e.g., El Niño–Southern Oscillation) and past human activity. The composite fire chronology spanned 1756–2013 with 132 individual scars representing 89 separate fire events. The mean fire interval was 2.9 yr, and mean intervals were significantly different between identified time periods (e.g., settlement period vs. management period). Evidence of biannual fire activity (up to three fires occurring within a 12‐ to 15‐month period) was found coeval with a peak in livestock grazing and logging from the 1850s through the 1880s. Connections were also found between historical fire and Pacific climate variability (e.g., El Niño–Southern Oscillation and Pacific Decadal Oscillation; P \u3c 0.05), yet the fire–climate linkage was likely at least partially masked by substantial human land use activities over the past several centuries. Coupled climate and human land use activity controlled the historical fire regime over the past ca. 240 yr. Although the many fire adaptions of P. palustris yield limitations in tree‐ring‐based fire history studies (e.g., thick bark), we highlight the efficacy of considering the height at which fire scars are analyzed along the bole as a way to glean a more accurate depiction of historical fire occurrence, especially in ecosystems characterized by a frequent, low‐severity fire regime. This study suggests growing‐season fire prescribed at a 2‐ to 3‐yr interval would be the first step toward simulating historical landscape conditions and fire activity, should that be the goal by land managers

Detecting paired and counterflow superfluidity via dipole oscillations

We suggest an experimentally feasible procedure to observe paired and counterflow superfluidity in ultra-cold atom systems. We study the time evolution of one-dimensional mixtures of bosonic atoms in an optical lattice following an abrupt displacement of an additional weak confining potential. We find that the dynamic responses of the paired superfluid phase for attractive inter-species interactions and the counterflow superfluid phase for repulsive interactions are qualitatively distinct and reflect the quasi long-range order that characterizes these states. These findings suggest a clear experimental procedure to detect these phases, and give an intuitive insight into their dynamics.Comment: 4 pages,5 figure

Filtering crosstalk from bath non-Markovianity via spacetime classical shadows

From an open system perspective non-Markovian effects due to a nearby bath or neighbouring qubits are dynamically equivalent. However, there is a conceptual distinction to account for: neighbouring qubits may be controlled. We combine recent advances in non-Markovian quantum process tomography with the framework of classical shadows to characterise spatiotemporal quantum correlations. Observables here constitute operations applied to the system, where the free operation is the maximally depolarising channel. Using this as a causal break, we systematically erase causal pathways to narrow down the progenitors of temporal correlations. We show that one application of this is to filter out the effects of crosstalk and probe only non-Markovianity from an inaccessible bath. It also provides a lens on spatiotemporally spreading correlated noise throughout a lattice from common environments. We demonstrate both examples on synthetic data. Owing to the scaling of classical shadows, we can erase arbitrarily many neighbouring qubits at no extra cost. Our procedure is thus efficient and amenable to systems even with all-to-all interactions.Comment: 5 pages, 4 figure

What have we already learned from the CMB?

The COBE satellite, and the DMR experiment in particular, was extraordinarily successful. However, the DMR results were announced about 7 years ago, during which time a great deal more has been learned about anisotropies in the Cosmic Microwave Background (CMB). The CMB experiments currently being designed and built, including long-duration balloons, interferometers, and two space missions, promise to address several fundamental cosmological issues. We present our evaluation of what we already know, what we are beginning to learn now, and what the future may bring.Comment: 20 pages, 3 figures. Changes to match version accepted by PAS