268 research outputs found
Parent Hamiltonians for lattice Halperin states from free-boson conformal field theories
We introduce a family of many-body quantum states that describe interacting
spin one-half hard-core particles with bosonic or fermionic statistics on
arbitrary one- and two-dimensional lattices. The wave functions at lattice
filling fraction are derived from deformations of the
Wess-Zumino-Witten model and are related to the
Halperin fractional quantum Hall states. We derive long-range
SU(2) invariant parent Hamiltonians for these states which in two dimensions
are chiral -- models with additional three-body interaction terms. In
one dimension we obtain a generalisation to open chains of a periodic
inverse-square -- model proposed in [Z. N. C. Ha and F. D. M. Haldane,
Phys. Rev. B , 9359 (1992)]. We observe that the gapless
low-energy spectrum of this model and its open-boundary generalisation can be
described by rapidity sets with the same generalised Pauli exclusion principle.
A two-component compactified free boson conformal field theory is identified
that has the same central charge and scaling dimensions as the periodic bosonic
inverse-square -- model.Comment: 19 pages, 2 figures. v2: minor corrections and partial rewriting of
section IV B
Transmission Phase of an Isolated Coulomb-Blockade Resonance
In two recent papers, O. Entin-Wohlman et al. studied the question: ``Which
physical information is carried by the transmission phase through a quantum
dot?'' In the present paper, this question is answered for an islolated
Coulomb-blockade resonance and within a theoretical model which is more closely
patterned after the geometry of the actual experiment by Schuster et al. than
is the model of O. Entin-Wohlman et al. We conclude that whenever the number of
leads coupled to the Aharanov-Bohm interferometer is larger than two, and the
total number of channels is sufficiently large, the transmission phase does
reflect the Breit-Wigner behavior of the resonance phase shift.Comment: 6 pages and one figur
Dynamical tunneling in optical cavities
The lifetime of whispering gallery modes in a dielectric cavity with a
metallic inclusion is shown to fluctuate by orders of magnitude when size and
location of the inclusion are varied. We ascribe these fluctuations to
tunneling transitions between resonances quantized in different regions of
phase space. This interpretation is confirmed by a comparison of the classical
phase space structure with the Husimi distribution of the resonant modes. A
model Hamiltonian is introduced that describes the phenomenon and shows that it
can be expected in a more general class of systems.Comment: 8 pages LaTeX with 5 postscript figure
Correlations of conductance peaks and transmission phases in deformed quantum dots
We investigate the Coulomb blockade resonances and the phase of the
transmission amplitude of a deformed ballistic quantum dot weakly coupled to
leads. We show that preferred single--particle levels exist which stay close to
the Fermi energy for a wide range of values of the gate voltage. These states
give rise to sequences of Coulomb blockade resonances with correlated peak
heights and transmission phases. The correlation of the peak heights becomes
stronger with increasing temperature. The phase of the transmission amplitude
shows lapses by between the resonances. Implications for recent
experiments on ballistic quantum dots are discussed.Comment: 29 pages, 9 eps-figure
Quality-Driven Disorder Handling for M-way Sliding Window Stream Joins
Sliding window join is one of the most important operators for stream
applications. To produce high quality join results, a stream processing system
must deal with the ubiquitous disorder within input streams which is caused by
network delay, asynchronous source clocks, etc. Disorder handling involves an
inevitable tradeoff between the latency and the quality of produced join
results. To meet different requirements of stream applications, it is desirable
to provide a user-configurable result-latency vs. result-quality tradeoff.
Existing disorder handling approaches either do not provide such
configurability, or support only user-specified latency constraints.
In this work, we advocate the idea of quality-driven disorder handling, and
propose a buffer-based disorder handling approach for sliding window joins,
which minimizes sizes of input-sorting buffers, thus the result latency, while
respecting user-specified result-quality requirements. The core of our approach
is an analytical model which directly captures the relationship between sizes
of input buffers and the produced result quality. Our approach is generic. It
supports m-way sliding window joins with arbitrary join conditions. Experiments
on real-world and synthetic datasets show that, compared to the state of the
art, our approach can reduce the result latency incurred by disorder handling
by up to 95% while providing the same level of result quality.Comment: 12 pages, 11 figures, IEEE ICDE 201
Crossing of two Coulomb-Blockade Resonances
We investigate theoretically the transport of non--interacting electrons
through an Aharanov--Bohm (AB) interferometer with two quantum dots (QD)
embedded into its arms. In the Coulomb-blockade regime, transport through each
QD proceeds via a single resonance. The resonances are coupled through the arms
of the AB device but may also be coupled directly. In the framework of the
Landauer--Buttiker approach, we present expressions for the scattering matrix
which depend explicitly on the energies of the two resonances and on the AB
phase. We pay particular attention to the crossing of the two resonances.Comment: 15 pages, 1 figur
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