19,477 research outputs found
Iterative solutions to the steady state density matrix for optomechanical systems
We present a sparse matrix permutation from graph theory that gives stable
incomplete Lower-Upper (LU) preconditioners necessary for iterative solutions
to the steady state density matrix for quantum optomechanical systems. This
reordering is efficient, adding little overhead to the computation, and results
in a marked reduction in both memory and runtime requirements compared to other
solution methods, with performance gains increasing with system size. Either of
these benchmarks can be tuned via the preconditioner accuracy and solution
tolerance. This reordering optimizes the condition number of the approximate
inverse, and is the only method found to be stable at large Hilbert space
dimensions. This allows for steady state solutions to otherwise intractable
quantum optomechanical systems.Comment: 10 pages, 5 figure
High-growth firms: introduction to the special section
High-growth firms (HGFs) have attracted considerable attention recently, as academics and policymakers have increasingly recognized the highly skewed nature of many metrics of firm performance. A small number of HGFs drives a disproportionately large amount of job creation, while the average firm has a limited impact on the economy. This article explores the reasons for this increased interest, summarizes the existing literature, and highlights the methodological considerations that constrain and bias research. This special section draws attention to the importance of HGFs for future industrial performance, explores their unusual growth trajectories and strategies, and highlights the lack of persistence of high growth. Consequently, while HGFs are important for understanding the economy and developing public policy, they are unlikely to be useful vehicles for public policy given the difficulties involved in predicting which firms will grow, the lack of persistence in high growth levels, and the complex and often indirect relationship between firm capability, high growth, and macro-economic performance
Preference reversal: Memory and contextual biases with choice
A virtue of good theory is that it is general; theories that predict a wide range of events have obvious merit. Several promi- nent theories of decision making achieve this objective by proposing that all decisions can be modeled with the same generic representation (e.g., Birnbaum, 2008; Tversky & Kahneman, 1992; von Neumann & Mor- genstern, 1947). For example, these theories assume that all decisions under risk or uncertainty can be represented as gambles, with monetary amounts representing the outcomes. In five experiments, we pursue an opposing, not previously investigated idea: Risky choices are affected by decision content, even when utilities and probabilities are known. We studied the influences of context (Experiments 1 and 2), memory (Experiments 3 and 4) and computational complexity (Experiment 5). In contrast with traditional theories, we find that people do not have un- derlying generic preferences; people’s experiences “leak” into decisions
even when risk information is explicitly provided
Internally Electrodynamic Particle Model: Its Experimental Basis and Its Predictions
The internally electrodynamic (IED) particle model was derived based on
overall experimental observations, with the IED process itself being built
directly on three experimental facts, a) electric charges present with all
material particles, b) an accelerated charge generates electromagnetic waves
according to Maxwell's equations and Planck energy equation and c) source
motion produces Doppler effect. A set of well-known basic particle equations
and properties become predictable based on first principles solutions for the
IED process; several key solutions achieved are outlined, including the de
Broglie phase wave, de Broglie relations, Schr\"odinger equation, mass,
Einstein mass-energy relation, Newton's law of gravity, single particle self
interference, and electromagnetic radiation and absorption; these equations and
properties have long been broadly experimentally validated or demonstrated. A
specific solution also predicts the Doebner-Goldin equation which emerges to
represent a form of long-sought quantum wave equation including gravity. A
critical review of the key experiments is given which suggests that the IED
process underlies the basic particle equations and properties not just
sufficiently but also necessarily.Comment: Presentation at the 27th Int Colloq on Group Theo Meth in Phys, 200
The Effects of X-Ray Feedback from AGN on Host Galaxy Evolution
Hydrodynamic simulations of galaxies with active galactic nuclei (AGN) have
typically employed feedback that is purely local: i.e., an injection of energy
to the immediate neighborhood of the black hole. We perform GADGET-2
simulations of massive elliptical galaxies with an additional feedback
component: an observationally calibrated X-ray radiation field which emanates
from the black hole and heats gas out to large radii from the galaxy center. We
find that including the heating and radiation pressure associated with this
X-ray flux in our simulations enhances the effects which are commonly reported
from AGN feedback. This new feedback model is twice as effective as traditional
feedback at suppressing star formation, produces 3 times less star formation in
the last 6 Gyr, and modestly lowers the final BH mass (30%). It is also
significantly more effective than an X-ray background in reducing the number of
satellite galaxies.Comment: 9 emulateapj pages, 8 figures; accepted to Ap
Coherent and sequential photoassisted tunneling through a semiconductor double barrier structure
We have studied the problem of coherent and sequential tunneling through a
double barrier structure, assisted by light considered to be present All over
the structure, i,e emitter, well and collector as in the experimental evidence.
By means of a canonical transformation and in the framework of the time
dependent perturbation theory, we have calculated the transmission coefficient
and the electronic resonant current. Our calculations have been compared with
experimental results turning out to be in good agreement. Also the effect on
the coherent tunneling of a magnetic field parallel to the current in the
presence of light, has been considered.Comment: Revtex3.0, 8figures uuencoded compressed tar-fil
Partial-measurement back-action and non-classical weak values in a superconducting circuit
We realize indirect partial measurement of a transmon qubit in circuit
quantum electrodynamics by interaction with an ancilla qubit and projective
ancilla measurement with a dedicated readout resonator. Accurate control of the
interaction and ancilla measurement basis allows tailoring the measurement
strength and operator. The tradeoff between measurement strength and qubit
back-action is characterized through the distortion of a qubit Rabi oscillation
imposed by ancilla measurement in different bases. Combining partial and
projective qubit measurements, we provide the solid-state demonstration of the
correspondence between a non-classical weak value and the violation of a
Leggett-Garg inequality.Comment: 5 pages, 4 figures, and Supplementary Information (8 figures
- …