696 research outputs found
The Vortex Phase Diagram of Rotating Superfluid He-B
We present the first theoretical calculation of the
pressure-temperature-field phase diagram for the vortex phases of rotating
superfluid He-B. Based on a strong-coupling extension of the
Ginzburg-Landau theory that accounts for the relative stability of the bulk A
and B phases of He at all pressures, we report calculations for the
internal structure and free energies of distinct broken-symmetry vortices in
rotating superfluid He-B. Theoretical results for the equilibrium vortex
phase diagram in zero field and an external field of H=284\,\mbox{G} parallel
to the rotation axis, , are reported, as well as
the supercooling transition line, . In zero field the vortex
phases of He-B are separated by a first-order phase transition line that terminates on the bulk critical line at a triple point.
The low-pressure, low-temperature phase is characterized by an array of
singly-quantized vortices that spontaneously breaks axial rotation symmetry,
exhibits anisotropic vortex currents and an axial current anomaly (D-core
phase). The high-pressure, high-temperature phase is characterized by vortices
with both bulk A phase and phase in their cores (A-core phase). We show
that this phase is metastable and supercools down to a minimum temperature,
, below which it is globally unstable to an array of D-core
vortices. For H\gtrsim 60\,\mbox{G} external magnetic fields aligned along
the axis of rotation increase the region of stability of the A-core phase of
rotating He-B, opening a window of stability down to low pressures. These
results are compared with the experimentally reported phase transitions in
rotating He-B.Comment: 14 pages, 11 figure
Two Pests Overlap: Drosophila suzukii (Diptera: Drosophilidae) Use of Fruit Exposed to Halyomorpha halys (Hemiptera: Pentatomidae)
Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) and brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), are global economic pests that may co-occur on small fruits. We investigated whether fruit recently exposed to H. halys affected subsequent host use by D. suzukii. Laboratory no-choice and choice tests presented D. suzukii with H. halys-fed and unfed raspberries and blueberries immediately or 3 d after H. halys feeding. Resulting D. suzukii eggs, or larvae and pupae, were counted. The number of D. suzukii immatures among fed and unfed fruit was not significantly different in lab studies. There was no relationship between the intensity of H. halys feeding, as estimated by the number of stylet sheaths, and D. suzukii oviposition on blueberry. Lastly, field studies compared D. suzukii infestation between H. halys-fed and unfed raspberries. Raspberries were previously exposed to H. halys for 3 d or simultaneously exposed to both pests for 7 d. Natural infestation by D. suzukii in the field was similar among raspberries previously or simultaneously exposed to H. halys compared to control fruit
Historical records of the digger wasps, Astata Latreille 1796 (Hymenoptera: Crabronidae: Astatinae), from the United States and Canada in the Oregon State Arthropod Collection
A dataset of 345 observational records is presented for the genus Astata (Hymenoptera: Crabronidae: Astatinae) based on 329 museum specimens and 16 photo vouchers. Summary information for the Pacific Northwest records is provided, including the species present, seasonality and county records for Oregon
Maximally symmetric stabilizer MUBs in even prime-power dimensions
One way to construct a maximal set of mutually unbiased bases (MUBs) in a
prime-power dimensional Hilbert space is by means of finite phase-space
methods. MUBs obtained in this way are covariant with respect to some subgroup
of the group of all affine symplectic phase-space transformations. However,
this construction is not canonical: as a consequence, many different choices of
covariance sugroups are possible. In particular, when the Hilbert space is
dimensional, it is known that covariance with respect to the full group
of affine symplectic phase-space transformations can never be achieved. Here we
show that in this case there exist two essentially different choices of maximal
subgroups admitting covariant MUBs. For both of them, we explicitly construct a
family of covariant MUBs. We thus prove that, contrary to the odd
dimensional case, maximally covariant MUBs are very far from being unique.Comment: 22 page
Clifford algebra as quantum language
We suggest Clifford algebra as a useful simplifying language for present
quantum dynamics. Clifford algebras arise from representations of the
permutation groups as they arise from representations of the rotation groups.
Aggregates using such representations for their permutations obey Clifford
statistics. The vectors supporting the Clifford algebras of permutations and
rotations are plexors and spinors respectively. Physical spinors may actually
be plexors describing quantum ensembles, not simple individuals. We use
Clifford statistics to define quantum fields on a quantum space-time, and to
formulate a quantum dynamics-field-space-time unity that evades the
compactification problem. The quantum bits of history regarded as a quantum
computation seem to obey a Clifford statistics.Comment: 13 pages, no figures. Some of these results were presented at the
American Physical Society Centennial Meeting, Atlanta, March 25, 199
Making mentoring work: The need for rewiring epistemology
To help produce expert coaches at both participation and performance levels, a number of governing bodies have established coach mentoring systems. In light of the limited literature on coach mentoring, as well as the risks of superficial treatment by coach education systems, this paper therefore critically discusses the role of the mentor in coach development, the nature of the mentor-mentee relationship and, most specifically, how expertise in the mentee may best be developed. If mentors are to be effective in developing expert coaches then we consequently argue that a focus on personal epistemology is required. On this basis, we present a framework that conceptualizes mentee development on this level through a step by step progression, rather than unrealistic and unachievable leap toward expertise. Finally, we consider the resulting implications for practice and research with respect to one-on-one mentoring, communities of practice, and formal coach education
Accuracy and Stability of Computing High-Order Derivatives of Analytic Functions by Cauchy Integrals
High-order derivatives of analytic functions are expressible as Cauchy
integrals over circular contours, which can very effectively be approximated,
e.g., by trapezoidal sums. Whereas analytically each radius r up to the radius
of convergence is equal, numerical stability strongly depends on r. We give a
comprehensive study of this effect; in particular we show that there is a
unique radius that minimizes the loss of accuracy caused by round-off errors.
For large classes of functions, though not for all, this radius actually gives
about full accuracy; a remarkable fact that we explain by the theory of Hardy
spaces, by the Wiman-Valiron and Levin-Pfluger theory of entire functions, and
by the saddle-point method of asymptotic analysis. Many examples and
non-trivial applications are discussed in detail.Comment: Version 4 has some references and a discussion of other quadrature
rules added; 57 pages, 7 figures, 6 tables; to appear in Found. Comput. Mat
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