60,684 research outputs found
On the Cauchy problem for the magnetic Zakharov system
In this paper, we study the Cauchy problem of the magnetic type Zakharov
system which describes the pondermotive force and magnetic field generation
effects resulting from the non-linear interaction between plasma-wave and
particles. By using the energy method to derive a priori bounds and an
approximation argument for the construction of solutions, we obtain local
existence and uniqueness results for the magnetic Zakharov system in the case
of
Analytical infrared intensities for periodic systems with local basis sets
We report a method for the efficient evaluation of analytic infrared (IR)
intensities within generalized Kohn-Sham density functional theory using
Gaussian orbitals and periodic boundary conditions. A discretized form of the
Berry phase is used to evaluate a periodic dipole moment and its derivatives
with respect to in-phase nuclear coordinate displacements. Benchmark
calculations are presented for one-dimensional chains of water molecules and
poly(paraphenylenevinylene).Comment: 16 pages, 3 figures, 4 tables, submitted to Phys. Rev.
The private capacity of quantum channels is not additive
Recently there has been considerable activity on the subject of additivity of
various quantum channel capacities. Here, we construct a family of channels
with sharply bounded classical, hence private capacity. On the other hand,
their quantum capacity when combined with a zero private (and zero quantum)
capacity erasure channel, becomes larger than the previous classical capacity.
As a consequence, we can conclude for the first time that the classical
private capacity is non-additive. In fact, in our construction even the quantum
capacity of the tensor product of two channels can be greater than the sum of
their individual classical private capacities.
We show that this violation occurs quite generically: every channel can be
embedded into our construction, and a violation occurs whenever the given
channel has larger entanglement assisted quantum capacity than (unassisted)
classical capacity.Comment: 4+4 pages, 2 eps figures. V2 has title and abstract changed; its new
structure reflects the final version of a main paper plus appendices
containing mathematical detail
Remote polarization entanglement generation by local dephasing and frequency upconversion
We introduce a scheme for remote entanglement generation for the photon
polarization. The technique is based on transferring the initial frequency
correlations to specific polarization-frequency correlations by local dephasing
and their subsequent removal by frequency up-conversion. On fundamental level,
our theoretical results show how to create and transfer entanglement, to
particles which never interact, by means of local operations. This possibility
stems from the multi-path interference and its control in frequency space. For
applications, the developed techniques and results allow for the remote
generation of entanglement with distant parties without Bell state measurements
and opens the perspective to probe frequency-frequency entanglement by
measuring the polarization state of the photons.Comment: 8 page
Geometries for Possible Kinematics
The algebras for all possible Lorentzian and Euclidean kinematics with
isotropy except static ones are re-classified. The geometries
for algebras are presented by contraction approach. The relations among the
geometries are revealed. Almost all geometries fall into pairs. There exists correspondence in each pair. In the viewpoint of
differential geometry, there are only 9 geometries, which have right signature
and geometrical spatial isotropy. They are 3 relativistic geometries, 3
absolute-time geometries, and 3 absolute-space geometries.Comment: 40 pages, 7 figure
Systematically improvable optimized atomic basis sets for {\it ab inito} calculations
We propose a unique scheme to construct fully optimized atomic basis sets for
density-functional calculations. The shapes of the radial functions are
optimized by minimizing the {\it spillage} of the wave functions between the
atomic orbital calculations and the converged plane wave calculations for dimer
systems. The quality of the bases can be systematically improved by increasing
the size of the bases within the same framework. The scheme is easy to
implement and very flexible. We have done extensive tests of this scheme for
wide variety of systems. The results show that the obtained atomic basis sets
are very satisfactory for both accuracy and transferability
Mixable Shuffles, Quasi-shuffles and Hopf Algebras
The quasi-shuffle product and mixable shuffle product are both
generalizations of the shuffle product and have both been studied quite
extensively recently. We relate these two generalizations and realize
quasi-shuffle product algebras as subalgebras of mixable shuffle product
algebras. As an application, we obtain Hopf algebra structures in free
Rota-Baxter algebras.Comment: 14 pages, no figure, references update
Evidence for Weyl fermions in a canonical heavy-fermion semimetal YbPtBi
The manifestation of Weyl fermions in strongly correlated electron systems is
of particular interest. We report evidence for Weyl fermions in the heavy
fermion semimetal YbPtBi from electronic structure calculations, angle-resolved
photoemission spectroscopy, magnetotransport and calorimetric measurements. At
elevated temperatures where -electrons are localized, there are triply
degenerate points, yielding Weyl nodes in applied magnetic fields. These are
revealed by a contribution from the chiral anomaly in the magnetotransport,
which at low temperatures becomes negligible due to the influence of electronic
correlations. Instead, Weyl fermions are inferred from the topological Hall
effect, which provides evidence for a Berry curvature, and a cubic temperature
dependence of the specific heat, as expected from the linear dispersion near
the Weyl nodes. The results suggest that YbPtBi is a Weyl heavy fermion
semimetal, where the Kondo interaction renormalizes the bands hosting Weyl
points. These findings open up an opportunity to explore the interplay between
topology and strong electronic correlations.Comment: 19 pages, 5 figures, Supplementary Information available with open
access at https://www.nature.com/articles/s41467-018-06782-
- …