11,686 research outputs found
Local trace formulae and scaling asymptotics in Toeplitz quantization, II
In the spectral theory of positive elliptic operators, an important role is
played by certain smoothing kernels, related to the Fourier transform of the
trace of a wave operator, which may be heuristically interpreted as smoothed
spectral projectors asymptotically drifting to the right of the spectrum. In
the setting of Toeplitz quantization, we consider analogues of these, where the
wave operator is replaced by the Hardy space compression of a linearized
Hamiltonian flow, possibly composed with a family of zeroth order Toeplitz
operators. We study the local asymptotics of these smoothing kernels, and
specifically how they concentrate on the fixed loci of the linearized dynamics.Comment: Typos corrected. Slight expository change
Scaling asymptotics for quantized Hamiltonian flows
In recent years, the near diagonal asymptotics of the equivariant components
of the Szeg\"{o} kernel of a positive line bundle on a compact symplectic
manifold have been studied extensively by many authors. As a natural
generalization of this theme, here we consider the local scaling asymptotics of
the Toeplitz quantization of a Hamiltonian symplectomorphism, and specifically
how they concentrate on the graph of the underlying classical map
Propagating and evanescent internal waves in a deep ocean model
We present experimental and computational studies of the propagation of
internal waves in a stratified fluid with an exponential density profile that
models the deep ocean. The buoyancy frequency profile (proportional to
the square root of the density gradient) varies smoothly by more than an order
of magnitude over the fluid depth, as is common in the deep ocean. The
nonuniform stratification is characterized by a turning depth , where
is equal to the wave frequency and .
Internal waves reflect from the turning depth and become evanescent below the
turning depth. The energy flux below the turning depth is shown to decay
exponentially with a decay constant given by , which is the horizontal
wavenumber at the turning depth. The viscous decay of the vertical velocity
amplitude of the incoming and reflected waves above the turning depth agree
within a few percent with a previously untested theory for a fluid of arbitrary
stratification [Kistovich and Chashechkin, J. App. Mech. Tech. Phys. 39,
729-737 (1998)].Comment: 13 pages, 4 figures, 4 table
Local trace formulae and scaling asymptotics in Toeplitz quantization
A trace formula for Toeplitz operators was proved by Boutet de Monvel and
Guillemin in the setting of general Toeplitz structures. Here we give a local
version of this result for a class of Toeplitz operators related to continuous
groups of symmetries on quantizable compact symplectic manifolds. The local
trace formula involves certain scaling asymptotics along the clean fixed locus
of the Hamiltonian flow of the symbol, reminiscent of the scaling asymptotics
of the equivariant components of the Szeg\"o kernel along the diagonal
Preferential utilization of endogenous arachidonate by cyclo-oxygenase in incubations of human platelets
AbstractThromboxane B2 (TXB2) and 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) formed from the endogenous and exogenous arachidonate during human platelet incubation, was evaluated by selected ion monitoring (SIM). TXB2 formed from endogenous substrate accounted for about one third of the total, whereas the great part of 12-HETE derived from exogenous arachidonate. These data indicate that under the tested conditions the pool of arachidonate that acts as substrate for cyclo-oxygenase is different from the pool that acts as substrate for lipoxygenase and that the arachidonate released from phospholipids is preferentially utilized by cyclo-oxygenase
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