8,114 research outputs found
Measurement models for time-resolved spectroscopy: a comment
We present an exactly solvable model for photon emission, which allows us to
examine the evolution of the photon wavefunction in space and time. We apply
this model to coherent phenomena in three-level systems with a special emphasis
on the photon detection process.Comment: 14 pages RevTex, 4 figure
The Functional Derivation of Master Equations
Master equations describe the quantum dynamics of open systems interacting
with an environment. They play an increasingly important role in understanding
the emergence of semiclassical behavior and the generation of entropy, both
being related to quantum decoherence. Presently we derive the exact master
equation for a homogeneous scalar Higgs or inflaton like field coupled to an
environment field represented by an infinite set of harmonic oscillators. Our
aim is to demonstrate a derivation directly from the path integral
representation of the density matrix propagator. Applications and
generalizations of this result are discussed.Comment: 10 pages; LaTex. - Contribution to the workshop Hadron Physics VI,
March 1998, Florianopolis (Brazil); proceedings, E. Ferreira et al., eds.
(World Scientific). Replaced by slightly modified published versio
In-hospital safety in field conditions of Nifurtimox Eflornithine Combination Therapy (NECT) for T. B. Gambiense Sleeping Sickness
Trypanosoma brucei (T.b.) gambiense Human African trypanosomiasis (HAT; sleeping sickness) is a fatal disease. Until 2009, available treatments for 2(nd) stage HAT were complicated to use, expensive (eflornithine monotherapy), or toxic, and insufficiently effective in certain areas (melarsoprol). Recently, nifurtimox-eflornithine combination therapy (NECT) demonstrated good safety and efficacy in a randomised controlled trial (RCT) and was added to the World Health Organisation (WHO) essential medicines list (EML). Documentation of its safety profile in field conditions will support its wider use
Percolation model for nodal domains of chaotic wave functions
Nodal domains are regions where a function has definite sign. In recent paper
[nlin.CD/0109029] it is conjectured that the distribution of nodal domains for
quantum eigenfunctions of chaotic systems is universal. We propose a
percolation-like model for description of these nodal domains which permits to
calculate all interesting quantities analytically, agrees well with numerical
simulations, and due to the relation to percolation theory opens the way of
deeper understanding of the structure of chaotic wave functions.Comment: 4 pages, 6 figures, Late
The equation of state for two flavor QCD at N_t=6
We calculate the two flavor equation of state for QCD on lattices with
lattice spacing a=(6T)^{-1} and find that cutoff effects are substantially
reduced compared to an earlier study using a=(4T)^{-1}. However, it is likely
that significant cutoff effects remain. We fit the lattice data to expected
forms of the free energy density for a second order phase transition at
zero-quark-mass, which allows us to extrapolate the equation of state to m_q=0
and to extract the speed of sound. We find that the equation of state depends
weakly on the quark mass for small quark mass.Comment: 24 pages, latex, 11 postscipt figure
A Supersymmetric D4 Model for mu-tau Symmetry
We construct a supersymmeterized version of the model presented by Grimus and
Lavoura (GL) in [1] which predicts theta_{23} maximal and theta_{13}=0 in the
lepton sector. For this purpose, we extend the flavor group, which is D4 x
Z2^{(aux)} in the original model, to D4 x Z5. An additional difference is the
absence of right-handed neutrinos. Despite these changes the model is the same
as the GL model, since theta_{23} maximal and theta_{13}=0 arise through the
same mismatch of D4 subgroups, D2 in the charged lepton and Z2 in the neutrino
sector. In our setup D4 is solely broken by gauge singlets, the flavons. We
show that their vacuum structure, which leads to the prediction of theta_{13}
and theta_{23}, is a natural result of the scalar potential. We find that the
neutrino mass matrix only allows for inverted hierarchy, if we assume a certain
form of spontaneous CP violation. The quantity |m_{ee}|, measured in
neutrinoless double beta decay, is nearly equal to the lightest neutrino mass
m3. The Majorana phases phi1 and phi2 are restricted to a certain range for m3
< 0.06 eV. We discuss the next-to-leading order corrections which give rise to
shifts in the vacuum expectation values of the flavons. These induce deviations
from maximal atmospheric mixing and vanishing theta_{13}. It turns out that
these deviations are smaller for theta_{23} than for theta_{13}.Comment: 19 pages, 4 figure
Quantum nondemolition-like, fast measurement scheme for a superconducting qubit
We present a measurement protocol for a flux qubit coupled to a
dc-Superconducting QUantum Interference Device (SQUID), representative of any
two-state system with a controllable coupling to an harmonic oscillator
quadrature, which consists of two steps. First, the qubit state is imprinted
onto the SQUID via a very short and strong interaction. We show that at the end
of this step the qubit dephases completely, although the perturbation of the
measured qubit observable during this step is weak. In the second step,
information about the qubit is extracted by measuring the SQUID. This step can
have arbitrarily long duration, since it no longer induces qubit errors.Comment: published version, minor correction
Quasienergy spectrum and tunneling current in ac-driven triple quantum dot shuttles
The dynamics of electrons in ac driven double quantum dots have been
extensively analyzed by means of Floquet theory. In these systems, coherent
destruction of tunneling has been shown to occur for certain ac field
parameters. In the present work we analyze, by means of Floquet theory, the
electron dynamics of a triple quantum dot in series attached to electric
contacts, where the central dot position oscillates. In particular, we analyze
the quasienergy spectrum of this ac driven nanoelectromechanical system, as a
function of the intensity and frequency of the ac field and of external dc
voltages. For strong driving fields, we derive, by means of perturbation
theory, analytical expressions for the quasienergies of the driven oscillator
system. From this analysis we discuss the conditions for coherent destruction
of tunneling (CDT) to occur as a function of detuning and field parameters. For
zero detuning, and from the invariance of the Floquet Hamiltonian under a
generalized parity transformation, we find analytical expressions describing
the symmetry properties of the Fourier components of the Floquet states under
such transformation. By using these expressions, we show that in the vicinity
of the CDT condition, the quasienergy spectrum exhibits exact crossings which
can be characterized by the parity properties of the corresponding
eigenvectors
Successful desensitization to pomalidomide in a patient with POEMS syndrome with delayed-type hypersensitivity to immunomodulatory imid drugs.
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