5,724 research outputs found
Synthesis and structure of the inclusion complex {NdQ[5]K@Q[10](H₂O)4}·4NO₃·20H₂O
Heating a mixture of Nd(NO₃)₃·6H₂O, KCl, Q[10] and Q[5] in HCl for 10 min affords the inclusion complex {NdQ[5]K@Q[10](H₂O)₄}·4NO₃·20H₂O. The structure of the inclusion complex has been investigated by single crystal X-ray diffraction and by X-ray Photoelectron spectroscopy (XPS)
Asymptotic Freedom of Elastic Strings and Barriers
We study the problem of a quantized elastic string in the presence of an
impenetrable wall. This is a two-dimensional field theory of an N-component
real scalar field which becomes interacting through the restriction that
the magnitude of is less than , for a spherical wall of
radius . The N=1 case is a string vibrating in a plane between
two straight walls. We review a simple nonperturbative argument that there is a
gap in the spectrum, with asymptotically-free behavior in the coupling (which
is the reciprocal of ) for N greater than or equal to one. This
scaling behavior of the mass gap has been disputed in some of the recent
literature. We find, however, that perturbation theory and the 1/N expansion
each confirms that these theories are asymptotically free. The large N limit
coincides with that of the O(N) nonlinear sigma model. A theta parameter exists
for the N=2 model, which describes a string confined to the interior of a
cylinder of radius .Comment: Text slightly improved, bibilography corrected, more typos corrected,
still Latex 7 page
Fast and robust population transfer in two-level quantum systems with dephasing noise and/or systematic frequency errors
We design, by invariant-based inverse engineering, driving fields that invert
the population of a two-level atom in a given time, robustly with respect to
dephasing noise and/or systematic frequency shifts. Without imposing
constraints, optimal protocols are insensitive to the perturbations but need an
infinite energy. For a constrained value of the Rabi frequency, a flat
pulse is the least sensitive protocol to phase noise but not to systematic
frequency shifts, for which we describe and optimize a family of protocols.Comment: 7 pages, 2 figure
Conditional HI mass functions and the HI-to-halo mass relation in the local Universe
We present a new HI mass estimator which relates the HI-to-stellar mass ratio
to four galaxy properties: stellar surface mass density, color index ,
stellar mass and concentration index, with the scatter of individual galaxies
around the mean HI mass modeled with a Gaussian distribution. We calibrate the
estimator using the xGASS sample, including both HI detection and
non-detection, and constrain the model parameters through Bayesian inferences.
Tests with mock catalogs demonstrate that our estimator provides unbiased HI
masses for optical samples like the SDSS, thus suitable for statistical studies
of HI gas contents in galaxies and dark matter halos. We apply our estimator to
the SDSS spectroscopic sample to estimate the local HI mass function (HIMF),
the conditional HI mass function (CHIMF) in galaxy groups and the HI-halo mass
(HIHM) relation. Our HIMF agrees with the ALFALFA measurements at
, but with higher amplitude and a steeper
slope at lower masses. We show that this discrepancy is caused primarily by the
cosmic variance which is corrected for the SDSS sample but not for the ALFALFA.
The CHIMFs for all halo masses can be described by a single Schechter function,
and this is true for red, blue and satellite galaxies. For central galaxies the
CHIMFs show a double-Gaussian profile, with the two components contributed by
the red and blue galaxies, respectively. The total HI mass in a group increases
monotonically with halo mass. The HI mass of central galaxies in galaxy groups
increases rapidly with halo mass only at , while
the mass dependence becomes much weaker at higher halo masses. The observed
HI-halo mass relation is not reproduced by current hydrodynamic simulations and
semi-analytic models of galaxy formation.Comment: 10 figures, 2 tables, published in ApJ. : The version
published in ApJ has a typo. In the last paragraph of section 3.2, the
maximum posterior value of c_a should be c_a = 0.10 \pm 0.08, not c_a = 0.16
\pm 0.1
Fast shuttling of a trapped ion in the presence of noise
We theoretically investigate the motional excitation of a single ion caused
by spring-constant and position uctuations of a harmonic trap during trap
shuttling processes. A detailed study of the sensitivity on noise for several
transport protocols and noise spectra is provided. The effect of slow
spring-constant drifts is also analyzed. Trap trajectories that minimize the
excitation are designed combining invariant-based inverse engineering,
perturbation theory, and optimal control
Partition Function Expansion on Region-Graphs and Message-Passing Equations
Disordered and frustrated graphical systems are ubiquitous in physics,
biology, and information science. For models on complete graphs or random
graphs, deep understanding has been achieved through the mean-field replica and
cavity methods. But finite-dimensional `real' systems persist to be very
challenging because of the abundance of short loops and strong local
correlations. A statistical mechanics theory is constructed in this paper for
finite-dimensional models based on the mathematical framework of partition
function expansion and the concept of region-graphs. Rigorous expressions for
the free energy and grand free energy are derived. Message-passing equations on
the region-graph, such as belief-propagation and survey-propagation, are also
derived rigorously.Comment: 10 pages including two figures. New theoretical and numerical results
added. Will be published by JSTAT as a lette
Phase-sensitive Manipulations of Squeezed Vacuum Field in an Optical Parametric Amplifier inside an Optical Cavity
Squeezed vacuum field can be amplified or deamplified when it is injected, as
the signal beam, into a phase-sensitive optical parametric amplifier (OPA)
inside an optical cavity. The spectral features of the reflected quantized
signal field are controlled by the relative phase between the injected squeezed
vacuum field and the pump field for the OPA. The experimental results
demonstrate coherent phenomena of OPA in the quantum regime, and show
phase-sensitive manipulations of quantum fluctuations for quantum information
processing.Comment: 4 pages, 3 figures, appear in Phys. Rev. Let
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