410 research outputs found
Dynamical fidelity of a solid-state quantum computation
In this paper we analyze the dynamics in a spin-model of quantum computer.
Main attention is paid to the dynamical fidelity (associated with dynamical
errors) of an algorithm that allows to create an entangled state for remote
qubits. We show that in the regime of selective resonant excitations of qubits
there is no any danger of quantum chaos. Moreover, in this regime a modified
perturbation theory gives an adequate description of the dynamics of the
system. Our approach allows to explicitly describe all peculiarities of the
evolution of the system under time-dependent pulses corresponding to a quantum
protocol. Specifically, we analyze, both analytically and numerically, how the
fidelity decreases in dependence on the model parameters.Comment: 9 pages, 6 figures, submitted to PR
Global Curriculum in Surgical Oncology
Background
The significant global variations in surgical oncology training paradigms can have a detrimental effect on tackling the rising global cancer burden. While some variations in training are essential to account for the differences in types of cancer and biology, the fundamental principles of providing care to a cancer patient remain the same. The development of a global curriculum in surgical oncology with incorporated essential standards could be very useful in building an adequately trained surgical oncology workforce, which in turn could help in tackling the rising global cancer burden.
Materials and Methods
The leaders of the Society of Surgical Oncology and European Society of Surgical Oncology convened a global curriculum committee to develop a global curriculum in surgical oncology.
Results
A global curriculum in surgical oncology was developed to incorporate the required domains considered to be essential in training a surgical oncologist. The curriculum was constructed in a modular fashion to permit flexibility to suit the needs of the different regions of the world. Similarly, recognizing the various sociocultural, financial and cultural influences across the world, the proposed curriculum is aspirational and not mandatory in intent.
Conclusions
A global curriculum was developed which may be considered as a foundational scaffolding for training surgical oncologists worldwide. It is envisioned that this initial global curriculum will provide a flexible and modular scaffolding that can be tailored by individual countries or regions to train surgical oncologists in a way that is appropriate for practice in their local environmen
Ehrenfest times for classically chaotic systems
We describe the quantum mechanical spreading of a Gaussian wave packet by
means of the semiclassical WKB approximation of Berry and Balazs. We find that
the time scale on which this approximation breaks down in a chaotic
system is larger than the Ehrenfest times considered previously. In one
dimension \tau=\fr{7}{6}\lambda^{-1}\ln(A/\hbar), with the Lyapunov
exponent and a typical classical action.Comment: 4 page
Doppler-Free Spectroscopy of Weak Transitions: An Analytical Model Applied to Formaldehyde
Experimental observation of Doppler-free signals for weak transitions can be
greatly facilitated by an estimate for their expected amplitudes. We derive an
analytical model which allows the Doppler-free amplitude to be estimated for
small Doppler-free signals. Application of this model to formaldehyde allows
the amplitude of experimentally observed Doppler-free signals to be reproduced
to within the experimental error.Comment: 7 pages, 7 figures, 1 table, v2: many small improvements + corrected
line assignmen
Ratios of Elastic Scattering of Pions from 3H and 3He
We have measured the elastic-scattering ratios of normalized yields for
charged pions from 3H and 3He in the backward hemisphere. At 180 MeV, we
completed the angular distribution begun with our earlier measurements, adding
six data points in the angular range of 119 deg to 169 deg in the pi-nucleus
center of mass. We also measured an excitation function with data points at
142, 180, 220, and 256 MeV incident pion energy at the largest achievable angle
for each energy between 160 deg and 170 deg in the pi-nucleus center of mass.
This excitation function corresponds to the energies of our forward-hemisphere
studies. The data, taken as a whole, show an apparent role reversal of the two
charge-symmetric ratios r1 and r2 in the backward hemisphere. Also, for data >
100 deg we observe a strong dependence on the four-momentum transfer squared
(-t) for all of the ratios regardless of pion energy or scattering angle, and
we find that the superratio R data match very well with calculations based on
the forward-hemisphere data that predicts the value of the difference between
the even-nucleon radii of 3H and 3He. Comparisons are also made with recent
calculations incorporating different wave functions and double scattering
models.Comment: RevTex 8pages, 12 figure file
Recommended from our members
Operationalising and measuring language dominance
The paper offers a new way to measure language ability in bilinguals, based on measures of lexical richness. The validity of proposed approach is tested in a variety of ways
Decay of the classical Loschmidt echo in integrable systems
We study both analytically and numerically the decay of fidelity of classical
motion for integrable systems. We find that the decay can exhibit two
qualitatively different behaviors, namely an algebraic decay, that is due to
the perturbation of the shape of the tori, or a ballistic decay, that is
associated with perturbing the frequencies of the tori. The type of decay
depends on initial conditions and on the shape of the perturbation but, for
small enough perturbations, not on its size. We demonstrate numerically this
general behavior for the cases of the twist map, the rectangular billiard, and
the kicked rotor in the almost integrable regime.Comment: 8 pages, 3 figures, revte
Nonlinear analysis of spacecraft thermal models
We study the differential equations of lumped-parameter models of spacecraft
thermal control. Firstly, we consider a satellite model consisting of two
isothermal parts (nodes): an outer part that absorbs heat from the environment
as radiation of various types and radiates heat as a black-body, and an inner
part that just dissipates heat at a constant rate. The resulting system of two
nonlinear ordinary differential equations for the satellite's temperatures is
analyzed with various methods, which prove that the temperatures approach a
steady state if the heat input is constant, whereas they approach a limit cycle
if it varies periodically. Secondly, we generalize those methods to study a
many-node thermal model of a spacecraft: this model also has a stable steady
state under constant heat inputs that becomes a limit cycle if the inputs vary
periodically. Finally, we propose new numerical analyses of spacecraft thermal
models based on our results, to complement the analyses normally carried out
with commercial software packages.Comment: 29 pages, 4 figure
Some FRW Models of Accelerating Universe with Dark Energy
The paper deals with a spatially homogeneous and isotropic FRW space-time
filled with perfect fluid and dark energy components. The two sources are
assumed to interact minimally, and therefore their energy momentum tensors are
conserved separately. A special law of variation for the Hubble parameter
proposed by Berman (1983) has been utilized to solve the field equations. The
Berman's law yields two explicit forms of the scale factor governing the FRW
space-time and constant values of deceleration parameter. The role of dark
energy with variable equation of state parameter has been studied in detail in
the evolution of FRW universe. It has been found that dark energy dominates the
universe at the present epoch, which is consistent with the observations. The
physical behavior of the universe is discussed in detail.Comment: 10 pages, 5 figure
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