2,083 research outputs found
Spontaneous Interlayer Charge Transfer near the Magnetic Quantum Limit
Experiments reveal that a confined electron system with two equally-populated
layers at zero magnetic field can spontaneously break this symmetry through an
interlayer charge transfer near the magnetic quantum limit. New fractional
quantum Hall states at unusual total filling factors such as \nu = 11/15 (= 1/3
+ 2/5) stabilize as signatures that the system deforms itself, at substantial
electrostatic energy cost, in order to gain crucial correlation energy by
"locking in" separate incompressible liquid phases at unequal fillings in the
two layers (e.g., layered 1/3 and 2/5 states in the case of \nu = 11/15).Comment: 4 pages, 4 figures (1 color) included in text. Related papers at
http://www.ee.princeton.edu/~hari/papers.htm
Magnetic-Field-Induced Hybridization of Electron Subbands in a Coupled Double Quantum Well
We employ a magnetocapacitance technique to study the spectrum of the soft
two-subband (or double-layer) electron system in a parabolic quantum well with
a narrow tunnel barrier in the centre. In this system unbalanced by gate
depletion, at temperatures T\agt 30 mK we observe two sets of quantum
oscillations: one originates from the upper electron subband in the
closer-to-the-gate part of the well and the other indicates the existence of
common gaps in the spectrum at integer fillings. For the lowest filling factors
and , both the common gap presence down to the point of one- to
two-subband transition and their non-trivial magnetic field dependences point
to magnetic-field-induced hybridization of electron subbands.Comment: Major changes, added one more figure, the latest version to be
published in JETP Let
Quantum Hall effect in single wide quantum wells
We study the quantum Hall states in the lowest Landau level for a single wide
quantum well. Due to a separation of charges to opposite sides of the well, a
single wide well can be modelled as an effective two level system. We provide
numerical evidence of the existence of a phase transition from an
incompressible to a compressible state as the electron density is increased for
specific well width. Our numerical results show a critical electron density
which depends on well width, beyond which a transition incompressible double
layer quantum Hall state to a mono-layer compressible state occurs. We also
calculate the related phase boundary corresponding to destruction of the
collective mode energy gap. We show that the effective tunneling term and the
interlayer separation are both renormalised by the strong magnetic field. We
also exploite the local density functional techniques in the presence of strong
magnetic field at to calculate renormalized . The
numerical results shows good agreement between many-body calculations and local
density functional techniques in the presence of a strong magnetic field at
. we also discuss implications of this work on the
incompressible state observed in SWQW.Comment: 30 pages, 7 figures (figures are not included
Conflicts and common interests in committees
Committees improve decisions by pooling members' independent information, but promote manipulation, obfuscation, and exaggeration of private information when members have conflicting preferences. Committee decision procedures transform continuous data into ordered ranks through voting. This coarsens the transmission of information, but controls strategic manipulations and allows some degree of information sharing. Each member becomes more cautious in casting the crucial vote than when he alone makes the decision based on own information. Increased quality of one member's information results in his casting the crucial vote more often. Committees make better decisions for members than does delegation. (JEL D71, D82, C72).postprin
MACS: Multi-agent COTR system for Defense Contracting
The field of intelligent multi-agent systems has expanded rapidly in the recent past. Multi-agent architectures and systems are being investigated and continue to develop. To date, little has been accomplished in applying multi-agent systems to the defense acquisition domain. This paper describes the design, development, and related considerations of a multi-agent system in the area of procurement and contracting for the defense acquisition community
The Shapiro Conjecture: Prompt or Delayed Collapse in the head-on collision of neutron stars?
We study the question of prompt vs. delayed collapse in the head-on collision
of two neutron stars. We show that the prompt formation of a black hole is
possible, contrary to a conjecture of Shapiro which claims that collapse is
delayed until after neutrino cooling. We discuss the insight provided by
Shapiro's conjecture and its limitation. An understanding of the limitation of
the conjecture is provided in terms of the many time scales involved in the
problem. General relativistic simulations in the Einstein theory with the full
set of Einstein equations coupled to the general relativistic hydrodynamic
equations are carried out in our study.Comment: 4 pages, 7 figure
The Collision of Two Black Holes
We study the head-on collision of two equal mass, nonrotating black holes. We
consider a range of cases from holes surrounded by a common horizon to holes
initially separated by about , where is the mass of each hole. We
determine the waveforms and energies radiated for both the and
waves resulting from the collision. In all cases studied the normal
modes of the final black hole dominate the spectrum. We also estimate
analytically the total gravitational radiation emitted, taking into account the
tidal heating of horizons using the membrane paradigm, and other effects. For
the first time we are able to compare analytic calculations, black hole
perturbation theory, and strong field, nonlinear numerical calculations for
this problem, and we find excellent agreement.Comment: 14 pages, 93-
Resolved Young Binary Systems And Their Disks
We have conducted a survey of young single and multiple systems in the Taurus–Auriga star-forming region with the Atacama Large Millimeter Array (ALMA), substantially improving both the spatial resolution and sensitivity with which individual protoplanetary disks in these systems have been observed. These ALMA observations can resolve binary separations as small as 25–30 au and have an average 3σ detection level of 0.35 mJy, equivalent to a disk mass of 4 × 10−5 M ⊙ for an M3 star. Our sample was constructed from stars that have an infrared excess and/or signs of accretion and have been classified as Class II. For the binary and higher-order multiple systems observed, we detect λ = 1.3 mm continuum emission from one or more stars in all of our target systems. Combined with previous surveys of Taurus, our 21 new detections increase the fraction of millimeter-detected disks to over 75% in all categories of stars (singles, primaries, and companions) earlier than spectral type M6 in the Class II sample. Given the wealth of other information available for these stars, this has allowed us to study the impact of multiplicity with a much larger sample. While millimeter flux and disk mass are related to stellar mass as seen in previous studies, we find that both primary and secondary stars in binary systems with separations of 30–4200 au have lower values of millimeter flux as a function of stellar mass than single stars. We also find that for these systems, the circumstellar disk around the primary star does not dominate the total disk mass in the system and contains on average 62% of the total mass
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