54,332 research outputs found
Geometric Phase, Hannay's Angle, and an Exact Action Variable
Canonical structure of a generalized time-periodic harmonic oscillator is
studied by finding the exact action variable (invariant). Hannay's angle is
defined if closed curves of constant action variables return to the same curves
in phase space after a time evolution. The condition for the existence of
Hannay's angle turns out to be identical to that for the existence of a
complete set of (quasi)periodic wave functions. Hannay's angle is calculated,
and it is shown that Berry's relation of semiclassical origin on geometric
phase and Hannay's angle is exact for the cases considered.Comment: Submitted to Phys. Rev. Lett. (revised version
Coherent output of photons from coupled superconducting transmission line resonators controlled by charge qubits
We study the coherent control of microwave photons propagating in a
superconducting waveguide consisting of coupled transmission line resonators,
each of which is connected to a tunable charge qubit. While these coupled line
resonators form an artificial photonic crystal with an engineered photonic band
structure, the charge qubits collectively behave as spin waves in the low
excitation limit, which modify the band-gap structure to slow and stop the
microwave propagation. The conceptual exploration here suggests an
electromagnetically controlled quantum device based on the on-chip circuit QED
for the coherent manipulation of photons, such as the dynamic creation of
laser-like output from the waveguide by pumping the artificial atoms for
population inversion.Comment: 8 pages, 3 figure
How Robust Are the Size Measurements of High-redshift Compact Galaxies?
Massive quiescent galaxies at are apparently much more compact
than galaxies of comparable mass today. How robust are these size measurements?
We perform comprehensive simulations to determine possible biases and
uncertainties in fitting single-component light distributions to real galaxies.
In particular, we examine the robustness of the measurements of the luminosity,
size, and other structural parameters. We devise simulations with increasing
realism to systematically disentangle effects due to the technique
(specifically using GALFIT) and the intrinsic structures of the galaxies. By
accurately capturing the detailed substructures of nearby elliptical galaxies
and then rescaling their sizes and signal-to-noise to mimic galaxies at
different redshifts, we confirm that the massive quiescent galaxies at are significantly more compact intrinsically than their local
counterparts. Their observed compactness is not a result of missing faint outer
light due to systematic errors in modeling. In fact, we find that fitting
multi-component galaxies with a single S\'ersic profile, the procedure most
commonly adopted in the literature, biases the inferred sizes higher by up to
10% - 20%, which accentuates the amount of size evolution required. If the sky
estimation has been done robustly and the model for the point-spread function
is fairly accurate, GALFIT can retrieve the properties of single-component
galaxies over a wide range of signal-to-noise ratios without introducing any
systematic errors.Comment: 18 pages, 11 figures, 8 tables; Accepted for publication in Ap
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