11,573 research outputs found
Half Cycle Pulse Train Induced State Redistribution of Rydberg Atoms
Population transfer between low lying Rydberg states independent of the
initial state is realized using a train of half-cycle pulses with pulse
durations much less than the classical orbit period. We demonstrate
experimentally the transfer of population from initial states around n=50 down
to n<40 as well as up to the continuum. The measured population transfer
matches well to a model of the process for 1D atoms.Comment: V2: discussion extended, version accepted for publication in Physical
Review
Fatigue life estimates for helicopter loading spectra
Helicopter loading histories applied to notch metal samples are used as examples, and their fatigue lives are calculated by using a simplified version of the local strain approach. This simplified method has the advantage that it requires knowing the loading history in only the reduced form of ranges and means and number of cycles from the rain-flow cycle counting method. The calculated lives compare favorably with test data
Facilitated spin models of dissipative quantum glasses
We introduce a class of dissipative quantum spin models with local
interactions and without quenched disorder that show glassy behaviour. These
models are the quantum analogs of the classical facilitated spin models. Just
like their classical counterparts, quantum facilitated models display complex
glassy dynamics despite the fact that their stationary state is essentially
trivial. In these systems, dynamical arrest is a consequence of kinetic
constraints and not of static ordering. These models display a quantum version
of dynamic heterogeneity: the dynamics towards relaxation is spatially
correlated despite the absence of static correlations. Associated dynamical
fluctuation phenomena such as decoupling of timescales is also observed.
Moreover, we find that close to the classical limit quantum fluctuations can
enhance glassiness, as recently reported for quantum liquids.Comment: 7 pages, 6 figure
Determination of the Rb ng-series quantum defect by electric-field-induced resonant energy transfer between cold Rydberg atoms
Resonant energy transfer between cold Rydberg atoms was used to determine
Rydberg atom energy levels, at precisions approaching those obtainable in
microwave spectroscopy. Laser cooled Rb atoms from a magneto-optical trap were
optically excited to 32d Rydberg states. The two-atom process 32d(j=5/2) +
32d(j=5/2) -> 34p(j=3/2) + 30g is resonant at an electric field of
approximately 0.3 V/cm. This process is driven by the electric dipole-dipole
interaction, which is allowed due to the partial f character that the g state
acquires in an electric field. The experimentally observed resonant field,
together with the Stark map calculation is used to make a determination of the
Rb ng-series quantum defect: delta_g (n=30) = 0.00405(6)
Cosmic Pathways for Compact Groups in the Milli-Millennium Simulation
We detected 10 compact galaxy groups (CGs) at in the semi-analytic
galaxy catalog of Guo et al. (2011) for the milli-Millennium Cosmological
Simulation (sCGs in mGuo2010a). We aimed to identify potential canonical
pathways for compact group evolution and thus illuminate the history of
observed nearby compact groups. By constructing merger trees for sCG
galaxies, we studied the cosmological evolution of key properties, and compared
them with Hickson CGs (HCGs). We found that, once sCG galaxies come
within 1 (0.5) Mpc of their most massive galaxy, they remain within that
distance until , suggesting sCG "birth redshifts". At stellar masses
of sCG most-massive galaxies are within . In several cases, especially in the two 4- and 5-member
systems, the amount of cold gas mass anti-correlates with stellar mass, which
in turn correlates with hot gas mass. We define the angular difference between
group members' 3D velocity vectors, , and note that
many of the groups are long-lived because their small values of
indicate a significant parallel component. For
triplets in particular, values range between
and so that galaxies are coming together along
roughly parallel paths, and pairwise separations do not show large pronounced
changes after close encounters. The best agreement between sCG and HCG physical
properties is for galaxy values, but HCG values are higher overall,
including for SFRs. Unlike HCGs, due to a tail at low SFR and , and a
lack of galaxies, only a few sCG galaxies
are on the star-forming main sequence.Comment: Style fixes to better match ApJ published version. Uses likeapj1.1
style files: 17 pages, 13 figures, 2 tables. LaTex style files available at
https://github.com/qtast/likeapj/releases/lates
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