45,496 research outputs found
Fundamental length in quantum theories with PT-symmetric Hamiltonians
The direct observability of coordinates x is often lost in PT-symmetric
quantum theories. A manifestly non-local Hilbert-space metric enters
the double-integral normalization of wave functions there. In the
context of scattering, the (necessary) return to the asymptotically fully local
metric has been shown feasible, for certain family of PT-symmetric toy
Hamiltonians H at least, in paper I (M. Znojil, Phys. Rev. D 78 (2008) 025026).
Now we show that in a confined-motion dynamical regime the same toy model
proves also suitable for an explicit control of the measure or width
of its non-locality. For this purpose each H is assigned here, constructively,
the complete menu of its hermitizing metrics
distinguished by their optional "fundamental lengths" .
The local metric of paper I recurs at while the most popular
CPT-symmetric hermitization proves long-ranged, with .Comment: 31 pp, 3 figure
Stability of negative and positive trions in quantum wires
Binding energies of negative () and positive trions () in quantum
wires are studied for strong quantum confinement of carriers which results in a
numerical exactly solvable model. The relative electron and hole localization
has a strong effect on the stability of trions. For equal hole and electron
confinement, is more stable but a small imbalance of the particle
localization towards a stronger hole localization e.g. due to its larger
effective mass, leads to the interchange of and recombination lines
in the photoluminescent spectrum as was recently observed experimentally. In
case of larger stability, a magnetic field oriented parallel to the wire
axis leads to a stronger increase of the binding energy resulting in a
crossing of the and lines
Entanglement quantification by local unitaries
Invariance under local unitary operations is a fundamental property that must
be obeyed by every proper measure of quantum entanglement. However, this is not
the only aspect of entanglement theory where local unitaries play a relevant
role. In the present work we show that the application of suitable local
unitary operations defines a family of bipartite entanglement monotones,
collectively referred to as "mirror entanglement". They are constructed by
first considering the (squared) Hilbert-Schmidt distance of the state from the
set of states obtained by applying to it a given local unitary. To the action
of each different local unitary there corresponds a different distance. We then
minimize these distances over the sets of local unitaries with different
spectra, obtaining an entire family of different entanglement monotones. We
show that these mirror entanglement monotones are organized in a hierarchical
structure, and we establish the conditions that need to be imposed on the
spectrum of a local unitary for the associated mirror entanglement to be
faithful, i.e. to vanish on and only on separable pure states. We analyze in
detail the properties of one particularly relevant member of the family, the
"stellar mirror entanglement" associated to traceless local unitaries with
nondegenerate spectrum and equispaced eigenvalues in the complex plane. This
particular measure generalizes the original analysis of [Giampaolo and
Illuminati, Phys. Rev. A 76, 042301 (2007)], valid for qubits and qutrits. We
prove that the stellar entanglement is a faithful bipartite entanglement
monotone in any dimension, and that it is bounded from below by a function
proportional to the linear entropy and from above by the linear entropy itself,
coinciding with it in two- and three-dimensional spaces.Comment: 13 pages, 3 figures. Improved and generalized proof of monotonicity
of the mirror and stellar entanglemen
The Keck/OSIRIS Nearby AGN Survey (KONA) I. The Nuclear K-band Properties of Nearby AGN
We introduce the Keck Osiris Nearby AGN survey (KONA), a new adaptive
optics-assisted integral-field spectroscopic survey of Seyfert galaxies. KONA
permits at ~0.1" resolution a detailed study of the nuclear kinematic structure
of gas and stars in a representative sample of 40 local bona fide active
galactic nucleus (AGN). KONA seeks to characterize the physical processes
responsible for the coevolution of supermassive black holes and galaxies,
principally inflows and outflows. With these IFU data of the nuclear regions of
40 Seyfert galaxies, the KONA survey will be able to study, for the first time,
a number of key topics with meaningful statistics. In this paper we study the
nuclear K-band properties of nearby AGN. We find that the luminosities of the
unresolved Seyfert 1 sources at 2.1 microns are correlated with the hard X-ray
luminosities, implying that the majority of the emission is non-stellar. The
best-fit correlation is logLK = 0.9logL2-10 keV + 4 over 3 orders of magnitude
in both K-band and X-ray luminosities. We find no strong correlation between
2.1 microns luminosity and hard X-ray luminosity for the Seyfert 2 galaxies.
The spatial extent and spectral slope of the Seyfert 2 galaxies indicate the
presence of nuclear star formation and attenuating material (gas and dust),
which in some cases is compact and in some galaxies extended. We detect
coronal-line emission in 36 galaxies and for the first time in five galaxies.
Finally, we find 4/20 galaxies that are optically classified as Seyfert 2 show
broad emission lines in the near-IR, and one galaxy (NGC 7465) shows evidence
of a double nucleus.Comment: Accepted for publication in ApJ, 19 pages with 18 figure
Range safety signal propagation through the SRM exhaust plume of the space shuttle
Theoretical predictions of plume interference for the space shuttle range safety system by solid rocket booster exhaust plumes are reported. The signal propagation was calculated using a split operator technique based upon the Fresnel-Kirchoff integral, using fast Fourier transforms to evaluate the convolution and treating the plume as a series of absorbing and phase-changing screens. Talanov's lens transformation was applied to reduce aliasing problems caused by ray divergence
Reionization history constraints from neural network based predictions of high-redshift quasar continua
Observations of the early Universe suggest that reionization was complete by
, however, the exact history of this process is still unknown. One
method for measuring the evolution of the neutral fraction throughout this
epoch is via observing the Ly damping wings of high-redshift quasars.
In order to constrain the neutral fraction from quasar observations, one needs
an accurate model of the quasar spectrum around Ly, after the spectrum
has been processed by its host galaxy but before it is altered by absorption
and damping in the intervening IGM. In this paper, we present a novel machine
learning approach, using artificial neural networks, to reconstruct quasar
continua around Ly. Our QSANNdRA algorithm improves the error in this
reconstruction compared to the state-of-the-art PCA-based model in the
literature by 14.2% on average, and provides an improvement of 6.1% on average
when compared to an extension thereof. In comparison with the extended PCA
model, QSANNdRA further achieves an improvement of 22.1% and 16.8% when
evaluated on low-redshift quasars most similar to the two high-redshift quasars
under consideration, ULAS J1120+0641 at and ULAS J1342+0928 at
, respectively. Using our more accurate reconstructions of these two
quasars, we estimate the neutral fraction of the IGM using a homogeneous
reionization model and find at
and at . Our
results are consistent with the literature and favour a rapid end to
reionization
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