16,174 research outputs found
Nonuniqueness in spin-density-functional theory on lattices
In electronic many-particle systems, the mapping between densities and spin
magnetizations, {n(r), m(r)}, and potentials and magnetic fields, {v(r), B(r)},
is known to be nonunique, which has fundamental and practical implications for
spin-density-functional theory (SDFT). This paper studies the nonuniqueness
(NU) in SDFT on arbitrary lattices. Two new, non-trivial cases are discovered,
here called local saturation and global noncollinear NU, and their properties
are discussed and illustrated. In the continuum limit, only some well-known
special cases of NU survive.Comment: 4 pages, 1 figur
Learning associations between clinical information and motion-based descriptors using a large scale MR-derived cardiac motion atlas
The availability of large scale databases containing imaging and non-imaging
data, such as the UK Biobank, represents an opportunity to improve our
understanding of healthy and diseased bodily function. Cardiac motion atlases
provide a space of reference in which the motion fields of a cohort of subjects
can be directly compared. In this work, a cardiac motion atlas is built from
cine MR data from the UK Biobank (~ 6000 subjects). Two automated quality
control strategies are proposed to reject subjects with insufficient image
quality. Based on the atlas, three dimensionality reduction algorithms are
evaluated to learn data-driven cardiac motion descriptors, and statistical
methods used to study the association between these descriptors and non-imaging
data. Results show a positive correlation between the atlas motion descriptors
and body fat percentage, basal metabolic rate, hypertension, smoking status and
alcohol intake frequency. The proposed method outperforms the ability to
identify changes in cardiac function due to these known cardiovascular risk
factors compared to ejection fraction, the most commonly used descriptor of
cardiac function. In conclusion, this work represents a framework for further
investigation of the factors influencing cardiac health.Comment: 2018 International Workshop on Statistical Atlases and Computational
Modeling of the Hear
Quantum memory for non-stationary light fields based on controlled reversible inhomogeneous broadening
We propose a new method for efficient storage and recall of non-stationary
light fields, e.g. single photon time-bin qubits, in optically dense atomic
ensembles. Our approach to quantum memory is based on controlled, reversible,
inhomogeneous broadening. We briefly discuss experimental realizations of our
proposal.Comment: 4 page
Two-component generalizations of the Camassa-Holm equation
A classification of integrable two-component systems of non-evolutionary partial differential equations that are analogous to the Camassa-Holm equation is carried out via the perturbative symmetry approach. Independently, a classification of compatible pairs of Hamiltonian operators is carried out, which leads to bi-Hamiltonian structures for the same systems of equations. Some exact solutions and Lax pairs are also constructed for the systems considered
Triple sign reversal of Hall effect in HgBa_{2}CaCu_{2}O_{6} thin films after heavy-ion irradiations
Triple sign reversal in the mixed-state Hall effect has been observed for the
first time in ion-irradiated HgBa_{2}CaCu_{2}O_{6} thin films. The negative dip
at the third sign reversal is more pronounced for higher fields, which is
opposite to the case of the first sign reversal near T_c in most high-T_c
superconductors. These observations can be explained by a recent prediction in
which the third sign reversal is attributed to the energy derivative of the
density of states and to a temperature-dependent function related to the
superconducting energy gap. These contributions prominently appear in cases
where the mean free path is significantly decreased, such as our case of
ion-irradiated thin films.Comment: 4 pages, 3 eps figures, submitted Phys. Rev. Let
A possible hadronic excess in psi(2S) decay and rho-pi puzzle
We examine the so-called rho-pi puzzle of the psi(2S) decay by incorporating
two inputs: One is the relative phase between the one-photon and the gluon
decay amplitude, and the other is a possible anomaly in the inclusive
nonelectromagnetic decay rate of psi(2S). We propose the possibility that in
the psi(2S) decay a hadronic decay process of long distance origin is important
in addition to the short-distance decay process. The amplitude of this
additional process should nearly cancel the three-gluon amplitude in the
exclusive psi(2S)---> 1-0- and turn the sum dominantly real in contrast to the
J/psi decay. We present general consequences of this mechanism and then briefly
look into two models which possibly explain the course of this additional
amplitude.Comment: 14 pages, 2 Tables, and 3 eps figures. Replaces the original version
with a minor change in the title and inclusion of more references. The
version to appear in Phys. Rev.
Determination of astrophysical 12N(p,g)13O reaction rate from the 2H(12N, 13O)n reaction and its astrophysical implications
The evolution of massive stars with very low-metallicities depends critically
on the amount of CNO nuclides which they produce. The
N(,\,)O reaction is an important branching point in
the rap-processes, which are believed to be alternative paths to the slow
3 process for producing CNO seed nuclei and thus could change the fate
of massive stars. In the present work, the angular distribution of the
H(N,\,O) proton transfer reaction at =
8.4 MeV has been measured for the first time. Based on the Johnson-Soper
approach, the square of the asymptotic normalization coefficient (ANC) for the
virtual decay of O N + was
extracted to be 3.92 1.47 fm from the measured angular
distribution and utilized to compute the direct component in the
N(,\,)O reaction. The direct astrophysical S-factor at
zero energy was then found to be 0.39 0.15 keV b. By considering the
direct capture into the ground state of O, the resonant capture via the
first excited state of O and their interference, we determined the total
astrophysical S-factors and rates of the N(,\,)O
reaction. The new rate is two orders of magnitude slower than that from the
REACLIB compilation. Our reaction network calculations with the present rate
imply that N()O will only compete successfully with
the decay of N at higher (two orders of magnitude)
densities than initially predicted.Comment: 8 figures, 2 tables, Submitted to Physical Review
Monotonicity results and bounds for the inverse hyperbolic sine
In this note, we present monotonicity results of a function involving to the
inverse hyperbolic sine. From these, we derive some inequalities for bounding
the inverse hyperbolic sine.Comment: 3 page
Two monotonic functions involving gamma function and volume of unit ball
In present paper, we prove the monotonicity of two functions involving the
gamma function and relating to the -dimensional volume of the
unit ball in .Comment: 7 page
- …