24,105 research outputs found
Kounis Syndrome Associated With Selective Anaphylaxis to Cefazolin.
info:eu-repo/semantics/publishedVersio
Neutral heavy lepton production at next high energy linear colliders
The discovery potential for detecting new heavy Majorana and Dirac neutrinos
at some recently proposed high energy colliders is discussed. These
new particles are suggested by grand unified theories and superstring-inspired
models. For these models the production of a single heavy neutrino is shown to
be more relevant than pair production when comparing cross sections and
neutrino mass ranges.
The process is calculated
including on-shell and off-shell heavy neutrino effects.
We present a detailed study of cross sections and distributions that shows a
clear separation between the signal and standard model contributions, even
after including hadronization effects.Comment: 4 pages including 15 figures, 1 table. RevTex. Accepted in Physical
Review
High magnetic field induced charge density wave states in a quasi-one dimensional organic conductor
We have measured the high field magnetoresistence and magnetization of
quasi-one- dimensional (Q1D) organic conductor (Per)2Pt(mnt)2 (where Per =
perylene and mnt = maleonitriledithiolate), which has a charge density wave
(CDW) ground state at zero magnetic field below 8 K. We find that the CDW
ground state is suppressed with moderate magnetic fields of order 20 T, as
expected from a mean field theory treatment of Pauli effects[W. Dieterich and
P. Fulde, Z. Physik 265, 239 - 243 (1973)]. At higher magnetic fields, a new,
density wave state with sub-phases is observed in the range 20 to 50 T, which
is reminiscent of the cascade of field induced, quantized, spin density wave
phases (FISDW) observed in the Bechgaard salts. The new density wave state,
which we tenatively identify as a field induced charge density wave state
(FICDW), is re-entrant to a low resistance state at even higher fields, of
order 50 T and above. Unlike the FISDW ground state, the FICDW state is only
weakly orbital, and appears for all directions of magnetic field. Our findings
are substantiated by electrical resistivity, magnetization, thermoelectric, and
Hall measurements. We discuss our results in light of theoretical work
involving magnetic field dependent Q1D CDW ground states in high magnetic
fields [D. Zanchi, A. Bjelis, and G. Montambaux, Phys. Rev. B 53, (1996)1240;
A. Lebed, JETP Lett. 78,138(2003)].Comment: 16 pages, 5 figure
Decoherence of Semiclassical Wigner Functions
The Lindblad equation governs general markovian evolution of the density
operator in an open quantum system. An expression for the rate of change of the
Wigner function as a sum of integrals is one of the forms of the Weyl
representation for this equation. The semiclassical description of the Wigner
function in terms of chords, each with its classically defined amplitude and
phase, is thus inserted in the integrals, which leads to an explicit
differential equation for the Wigner function. All the Lindblad operators are
assumed to be represented by smooth phase space functions corresponding to
classical variables. In the case that these are real, representing hermitian
operators, the semiclassical Lindblad equation can be integrated. There results
a simple extension of the unitary evolution of the semiclassical Wigner
function, which does not affect the phase of each chord contribution, while
dampening its amplitude. This decreases exponentially, as governed by the time
integral of the square difference of the Lindblad functions along the classical
trajectories of both tips of each chord. The decay of the amplitudes is shown
to imply diffusion in energy for initial states that are nearly pure.
Projecting the Wigner function onto an orthogonal position or momentum basis,
the dampening of long chords emerges as the exponential decay of off-diagonal
elements of the density matrix.Comment: 23 pg, 2 fi
Spin-glass behaviour on random lattices
The ground-state phase diagram of an Ising spin-glass model on a random graph
with an arbitrary fraction of ferromagnetic interactions is analysed in the
presence of an external field. Using the replica method, and performing an
analysis of stability of the replica-symmetric solution, it is shown that
, correponding to an unbiased spin glass, is a singular point in the
phase diagram, separating a region with a spin-glass phase () from a
region with spin-glass, ferromagnetic, mixed, and paramagnetic phases
()
Duality between quantum and classical dynamics for integrable billiards
We establish a duality between the quantum wave vector spectrum and the
eigenmodes of the classical Liouvillian dynamics for integrable billiards.
Signatures of the classical eigenmodes appear as peaks in the correlation
function of the quantum wave vector spectrum. A semiclassical derivation and
numerical calculations are presented in support of the results. These classical
eigenmodes can be observed in physical experiments through the auto-correlation
of the transmission coefficient of waves in quantum billiards. Exact classical
trace formulas of the resolvent are derived for the rectangle, equilateral
triangle, and circle billiards. We also establish a correspondence between the
classical periodic orbit length spectrum and the quantum spectrum for
integrable polygonal billiards.Comment: 12 pages, 4 figure
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