9,905 research outputs found
Infrared interferometry to spatially and spectrally resolve jets in X-ray binaries
Infrared interferometry is a new frontier for precision ground based
observing, with new instrumentation achieving milliarcsecond (mas) spatial
resolutions for faint sources, along with astrometry on the order of 10
microarcseconds. This technique has already led to breakthroughs in the
observations of the supermassive black hole at the Galactic centre and its
orbiting stars, AGN, and exo-planets, and can be employed for studying X-ray
binaries (XRBs), microquasars in particular. Beyond constraining the orbital
parameters of the system using the centroid wobble and spatially resolving jet
discrete ejections on mas scales, we also propose a novel method to discern
between the various components contributing to the infrared bands: accretion
disk, jets and companion star. We demonstrate that the GRAVITY instrument on
the Very Large Telescope Interferometer (VLTI) should be able to detect a
centroid shift in a number of sources, opening a new avenue of exploration for
the myriad of transients expected to be discovered in the coming decade of
radio all-sky surveys. We also present the first proof-of-concept GRAVITY
observation of a low-mass X-ray binary transient, MAXI J1820+070, to search for
extended jets on mas scales. We place the tightest constraints yet via direct
imaging on the size of the infrared emitting region of the compact jet in a
hard state XRB.Comment: 12 Pages, 3 figures, accepted for publication in MNRA
Elementary solution to the time-independent quantum navigation problem
A quantum navigation problem concerns the identification of a time-optimal Hamiltonian that realizes a required quantum process or task, under the influence of a prevailing ‘background’ Hamiltonian that cannot be manipulated. When the task is to transform one quantum state into another, finding the solution in closed form to the problem is nontrivial even in the case of timeindependent Hamiltonians. An elementary solution, based on trigonometric analysis, is found here when the Hilbert space dimension is two. Difficulties arising from generalizations to higher-dimensional systems are discussed
A global fit of top quark effective theory to data
In this paper we present a global fit of beyond the Standard Model (BSM)
dimension six operators relevant to the top quark sector to currently available
data. Experimental measurements include parton-level top-pair and single top
production from the LHC and the Tevatron. Higher order QCD corrections are
modelled using differential and global K-factors, and we use novel fast-fitting
techniques developed in the context of Monte Carlo event generator tuning to
perform the fit. This allows us to provide new, fully correlated and
model-independent bounds on new physics effects in the top sector from the most
current direct hadron-collider measurements in light of the involved
theoretical and experimental systematics. As a by-product, our analysis
constitutes a proof-of-principle that fast fitting of theory to data is
possible in the top quark sector, and paves the way for a more detailed
analysis including top quark decays, detector corrections and precision
observables.Comment: Additional references and preprint code added. Minor error in
generation of plots fixed, no conclusions affecte
Candidates for asteroid dust trails
The contribution of different sources to the circumsolar dust cloud (known as the zodiacal cloud) can be deduced from diagnostic observations. We used the Spitzer Space Telescope to observe the diffuse thermal emission of the zodiacal cloud near the ecliptic. Several structures were identified in these observations, including previously known asteroid dust bands, which are thought to have been produced by recent asteroid collisions, and cometary trails. Interestingly, two of the detected dust trails, denoted t1 and t2 here, cannot be linked to any known comet. Trails t1 and t2 represent a much larger integrated brightness than all known cometary trails combined and may therefore be major contributors to the circumsolar dust cloud. We used our Spitzer observations to determine the orbits of these trails and were able to link them to two ("orphan" or type II) trails that were discovered by the Infrared Astronomical Satellite (IRAS) in 1983. The orbits of trails t1 and t2 that we determined by combining the Spitzer and IRAS data have semimajor axes, eccentricities, and inclinations like those of the main-belt asteroids. We therefore propose that trails t1 and t2 were produced by very recent (<~100 kyr old) collisional breakups of small, <~10 km diameter main-belt asteroids
Factors Influencing Willingness-to-Pay for the Energy Star Label
In the United States, nearly 17 percent of greenhouse gas emissions come from residential energy use. Increases in energy efficiency for the residential sector can generate significant energy savings and emissions reductions. Consumer labels, such as USEPA’s Energy Star, promote conservation by providing consumers with information on energy usage for household appliances. This study examines how the Energy Star label affects consumer preferences for refrigerators. An online survey of a national sample of adults suggest that consumers are, on average, willing to pay an extra 349.30 for a refrigerator that has been awarded the Energy Star label. Furthermore, the results provide evidence that willingness to pay was motivated by both private (energy cost savings) and public (environmental) benefits.Energy Star, willingness-to-pay, eco-label, Consumer/Household Economics, Demand and Price Analysis, Environmental Economics and Policy,
Bistability in a simple fluid network due to viscosity contrast
We study the existence of multiple equilibrium states in a simple fluid
network using Newtonian fluids and laminar flow. We demonstrate theoretically
the presence of hysteresis and bistability, and we confirm these predictions in
an experiment using two miscible fluids of different viscosity--sucrose
solution and water. Possible applications include bloodflow, microfluidics, and
other network flows governed by similar principles
Results from TopFitter
We discuss a global fit of top quark BSM couplings, phrased in the
model-independent language of higher-dimensional effective operators, to the
currently available data from the LHC and Tevatron. We examine the interplay
between inclusive and differential measurements, and the complementarity of LHC
and Tevatron results. We conclude with a discussion of projections for
improvement over LHC Run II.Comment: 5 pages, 4 figures, proceedings of the 9th International Workshop on
the CKM Unitarity Triangle, 28 November - 3 December 2016, Tata Institute for
Fundamental Research (TIFR), Mumbai, Indi
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