7,210 research outputs found
Anomalous slow fidelity decay for symmetry breaking perturbations
Symmetries as well as other special conditions can cause anomalous slowing
down of fidelity decay. These situations will be characterized, and a family of
random matrix models to emulate them generically presented. An analytic
solution based on exponentiated linear response will be given. For one
representative case the exact solution is obtained from a supersymmetric
calculation. The results agree well with dynamical calculations for a kicked
top.Comment: 4 pages, 2 figure
Parametric correlations versus fidelity decay: the symmetry breaking case
We derive fidelity decay and parametric energy correlations for random matrix
ensembles where time--reversal invariance of the original Hamiltonian is broken
by the perturbation. Like in the case of a symmetry conserving perturbation a
simple relation between both quantities can be established.Comment: 8 pages, 8 figure
Time-Resolved Measurement of a Charge Qubit
We propose a scheme for monitoring coherent quantum dynamics with good
time-resolution and low backaction, which relies on the response of the
considered quantum system to high-frequency ac driving. An approximate
analytical solution of the corresponding quantum master equation reveals that
the phase of an outgoing signal, which can directly be measured in an
experiment with lock-in technique, is proportional to the expectation value of
a particular system observable. This result is corroborated by the numerical
solution of the master equation for a charge qubit realized with a Cooper-pair
box, where we focus on monitoring coherent oscillations.Comment: 4 pages, 3 figure
Frustration of decoherence in -shaped superconducting Josephson networks
We examine the possibility that pertinent impurities in a condensed matter
system may help in designing quantum devices with enhanced coherent behaviors.
For this purpose, we analyze a field theory model describing Y- shaped
superconducting Josephson networks. We show that a new finite coupling stable
infrared fixed point emerges in its phase diagram; we then explicitly evidence
that, when engineered to operate near by this new fixed point, Y-shaped
networks support two-level quantum systems, for which the entanglement with the
environment is frustrated. We briefly address the potential relevance of this
result for engineering finite-size superconducting devices with enhanced
quantum coherence. Our approach uses boundary conformal field theory since it
naturally allows for a field-theoretical treatment of the phase slips
(instantons), describing the quantum tunneling between degenerate levels.Comment: 11 pages, 5 .eps figures; several changes in the presentation and in
the figures, upgraded reference
Detecting failure events in buildings: a numerical and experimental analysis
A numerical method is used to investigate an approach for detecting the brittle fracture of welds associated with beam
-column connections in instrumented buildings in real time through the use of time-reversed Green’s functions and
wave propagation reciprocity. The approach makes use of a prerecorded catalog of Green’s functions for an instrumented building to detect failure events in the
building during a later seismic event by screening continuous data for the presence of waveform similarities to one of the prerecorded events. This study
addresses whether a set of Green’s functions in response to an impulsive force load can be used to approximate the response of the structure to a localized failure
event such as a brittle weld fracture. Specifically, we investigate whether prerecorded Green’s functions can be used to determine the absolute time and location of a localized failure event in a building. We also seek to differentiate between sources such as a weld fracture that are structurally damaging and sources such as falling or colliding furniture and other non-structural elements
that do not contribute to structural failure. This is explored numerically by comparing the dynamic response of a finite-element cantilevered beam model structure to a variety of loading mechanisms. A finite-element method is
employed to determine the behavior of the resulting elastic waves and to obtain a general understanding of the structural response
Supersymmetric Extensions of Calogero--Moser--Sutherland like Models: Construction and Some Solutions
We introduce a new class of models for interacting particles. Our
construction is based on Jacobians for the radial coordinates on certain
superspaces. The resulting models contain two parameters determining the
strengths of the interactions. This extends and generalizes the models of the
Calogero--Moser--Sutherland type for interacting particles in ordinary spaces.
The latter ones are included in our models as special cases. Using results
which we obtained previously for spherical functions in superspaces, we obtain
various properties and some explicit forms for the solutions. We present
physical interpretations. Our models involve two kinds of interacting
particles. One of the models can be viewed as describing interacting electrons
in a lower and upper band of a one--dimensional semiconductor. Another model is
quasi--two--dimensional. Two kinds of particles are confined to two different
spatial directions, the interaction contains dipole--dipole or tensor forces.Comment: 21 pages, 4 figure
Structural health monitoring through dense instrumentation by community participants: the Community Seismic Network and Quake-Catcher Network
The Community Seismic Network and Quake-Catcher Network involve participants from communities at large to install low-cost accelerometers in houses and buildings for assessment of shaking intensity due to earthquakes. The seismometers are designed for two types of connec-tions: a USB-connected device which connects to the host’s computer, and a stand-alone sensor-plug-computer device that directly connects to the internet. The three-component sensors report both continuous data and amplitude anomalies in local acceleration to a Cloud computing service consisting of data centers geographically distributed across the continent, or to a distributed computing system. The continuous time series waveform data are being used to evaluate response parameters such as peak acceleration, peak velocity, and inter-story drift values. In addition, modal properties such as fundamental and higher mode frequencies and mode shapes are being computed from small and moderate earthquake data from the building. Building motion is computed for every floor of the building using only earthquake records from a single floor. Visualization models that map the instrumented buildings’ responses have been construct-ed using SketchUp and an associated plug-in to Matlab with recorded shaking data. This data visualization approach is different from other techniques because each building model is customized to show actual data recorded from that building on varying spatial scales, without the need for large-scale parallel computing facilities or complicated software that requires a steep learning curve
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