10,141 research outputs found
Multiple junction biasing of superconducting tunnel junction detectors
We describe a new biasing scheme for single photon detectors based on
superconducting tunnel junctions. It replaces a single detector junction with a
circuit of three junctions and achieves biasing of a detector junction at
subgap currents without the use of an external magnetic field. The biasing
occurs through the nonlinear interaction of the three junctions, which we
demonstrate through numerical simulation. This nonlinear state is numerically
stable against external fluctuations and is compatible with high fidelity
electrical readout of the photon-induced current. The elimination of the
external magnetic field potentially increases the capability of these types of
photon detectors and eases constraints involved in the fabrication of large
detector arrays.Comment: 15 pages, including 3 figure
Corfu 05 lectures - part I: Strings on curved backgrounds
In these introductory lectures we summarize some basic facts and techniques
about perturbative string theory (sections 1 to 6). These are further developed
(sections 7 and 8) for describing string propagation in the presence of
gravitational or gauge fields. We also remind some solutions of the string
equations of motion, which correspond to remarkable (NS or D) brane
configurations.
A part II by Emilian Dudas will be devoted to orientifold constructions and
applications to string model building
Multi-wavelength Signatures of Cosmic Rays in the Milky Way
Cosmic rays (CRs) propagate in the Milky Way and interact with the
interstellar medium and magnetic fields. These interactions produce emissions
that span the electromagnetic spectrum, and are an invaluable tool for
understanding the intensities and spectra of CRs in distant regions, far beyond
those probed by direct CR measurements. We present updates on the study of CR
properties by combining multi-frequency observations of the interstellar
emission and latest CR direct measurements with propagation models.Comment: 8 pages, 4 figures. Proceedings of the 35th International Cosmic Ray
Conference, ICRC201
Bright hot impacts by erupted fragments falling back on the Sun: magnetic channelling
Dense plasma fragments were observed to fall back on the solar surface by the
Solar Dynamics Observatory after an eruption on 7 June 2011, producing strong
EUV brightenings. Previous studies investigated impacts in regions of weak
magnetic field. Here we model the km/s impact of fragments
channelled by the magnetic field close to active regions. In the observations,
the magnetic channel brightens before the fragment impact. We use a 3D-MHD
model of spherical blobs downfalling in a magnetized atmosphere. The blob
parameters are constrained from the observation. We run numerical simulations
with different ambient density and magnetic field intensity. We compare the
model emission in the 171\AA~ channel of the Atmospheric Imaging Assembly with
the observed one. We find that a model of downfall channelled in a MK
coronal loop confined by a magnetic field of G, best explains
qualitatively and quantitatively the observed evolution. The blobs are highly
deformed, further fragmented, when the ram pressure becomes comparable to the
local magnetic pressure and they are deviated to be channelled by the field,
because of the differential stress applied by the perturbed magnetic field.
Ahead of them, in the relatively dense coronal medium, shock fronts propagate,
heat and brighten the channel between the cold falling plasma and the solar
surface. This study shows a new mechanism which brightens downflows channelled
by the magnetic field, such as in accreting young stars, and also works as a
probe of the ambient atmosphere, providing information about the local plasma
density and magnetic field.Comment: 17 pages, 14 figure
Do primary energy resources influence industry location?
By choosing to locate in a particular place, firms create employment opportunities for workers living there. And the wages they pay increase demand for local goods and services, creating additional job opportunities and further increasing the tax base. Consequently, state and local governments go to great lengths to encourage firms to locate within their boundaries.> In recent years, volatility in energy markets due to deregulation and events in the Middle East have increased the role that energy resource endowments may play in firm location. Thus, economic development agencies in energy producing states have highlighted their natural advantages as a way to attract and retain businesses. Yet there is scant evidence that firms base their location decisions on the availability of primary energy resources, such as coal, oil, and natural gas.> Martinek and Orlando explore the role of primary energy resources in industry location. They examine the relationship between state energy supplies and employment in energy-intensive industries and suggest there is a limited relationship between the production of primary energy resources and industry location. State energy supplies are associated with the location of only the most energy-intensive firms. In other energy-intensive industries, firm location decisions appear largely unresponsive to state energy conditions.Industrial location ; Natural resources ; Employment (Economic theory)
Fast partial decoherence of a superconducting flux qubit in a spin bath
The superconducting flux qubit has two quantum states with opposite magnetic
flux. Environment of nuclear spins can find out the direction of the magnetic
flux after a decoherence time inversely proportional to the magnitude
of the flux and the square root of the number of spins. When the Hamiltonian of
the qubit drives fast coherent Rabi oscillations between the states with
opposite flux, then flux direction is flipped at a constant rate and
the decoherence time is much longer than .
However, on closer inspection decoherence actually takes place on two
timescales. The long time is a time of full decoherence but a part of
quantum coherence is lost already after the short time . This fast
partial decoherence biases coherent flux oscillations towards the initial flux
direction and it can affect performance of the superconducting devices as
qubits.Comment: 7 page
Model Order Selection Rules For Covariance Structure Classification
The adaptive classification of the interference covariance matrix structure
for radar signal processing applications is addressed in this paper. This
represents a key issue because many detection architectures are synthesized
assuming a specific covariance structure which may not necessarily coincide
with the actual one due to the joint action of the system and environment
uncertainties. The considered classification problem is cast in terms of a
multiple hypotheses test with some nested alternatives and the theory of Model
Order Selection (MOS) is exploited to devise suitable decision rules. Several
MOS techniques, such as the Akaike, Takeuchi, and Bayesian information criteria
are adopted and the corresponding merits and drawbacks are discussed. At the
analysis stage, illustrating examples for the probability of correct model
selection are presented showing the effectiveness of the proposed rules
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