3,972 research outputs found
A High Current Proton Linac with 352 MHz SC Cavities
A proposal for a 10-120 mA proton linac employing superconducting
beta-graded, CERN type, four cell cavities at 352 MHz is presented. The high
energy part (100 MeV-1 GeV) of the machine is split in three beta-graded
sections, and transverse focusing is provided via a periodic doublet array. All
the parameters, like power in the couplers and accelerating fields in the
cavities, are within the state of the art, achieved in operating machines. A
first stage of operation at 30 mA beam current is proposed, while the upgrade
of the machine to 120 mA operation can be obtained increasing the number of
klystrons and couplers per cavity. The additional coupler ports, up to four,
will be integrated in the cavity design. Preliminary calculations indicate that
beam transport is feasible, given the wide aperture of the 352 MHz structures.
A capital cost of less than 100 M for the 120
mA extension, has been estimated for the superconducting high energy section
(100 MeV-1 GeV). The high efficiency of the proposed machine, reaching 50% at
15 mA, makes it a good candidate for proposed nuclear waste incineration
facilities and Energy Amplifier studies.Comment: 9 Pages, 4 figures, LaTeX2e, html version found from
http://hptesla.mi.infn.it/~pierini/publication_list.html . To Appear in the
Proceedings of the 1996 LINAC Conference, Geneve, August 26-30 199
On the foundations of cancer modelling: selected topics, speculations, & perspectives
This paper presents a critical review of selected topics related to the modelling of cancer onset, evolution and growth, with the aim of illustrating, to a wide applied mathematical readership, some of the novel mathematical problems in the field. This review attempts to capture, from the appropriate literature, the main issues involved in the modelling of phenomena related to cancer dynamics at all scales which characterise this highly complex system: from the molecular scale up to that of tissue. The last part of the paper discusses the challenge of developing a mathematical biological theory of tumour onset and evolution
Classical Evolution of Quantum Elliptic States
The hydrogen atom in weak external fields is a very accurate model for the
multiphoton excitation of ultrastable high angular momentum Rydberg states, a
process which classical mechanics describes with astonishing precision. In this
paper we show that the simplest treatment of the intramanifold dynamics of a
hydrogenic electron in external fields is based on the elliptic states of the
hydrogen atom, i.e., the coherent states of SO(4), which is the dynamical
symmetry group of the Kepler problem. Moreover, we also show that classical
perturbation theory yields the {\it exact} evolution in time of these quantum
states, and so we explain the surprising match between purely classical
perturbative calculations and experiments. Finally, as a first application, we
propose a fast method for the excitation of circular states; these are
ultrastable hydrogenic eigenstates which have maximum total angular momentum
and also maximum projection of the angular momentum along a fixed direction. %Comment: 8 Pages, 2 Figures. Accepted for publication in Phys. Rev.
Comment on "Quantum discord through the generalized entropy in bipartite quantum states"
In [X.-W. Hou, Z.-P. Huang, S. Chen, Eur. Phys. J. D 68, 1 (2014)], Hou et
al. present, using Tsallis' entropy, possible generalizations of the quantum
discord measure, finding original results. As for the mutual informations and
discord, we show here that these two types of quantifiers can take negative
values. In the two qubits instance we further determine in which regions they
are non-negative. Additionally, we study alternative generalizations on the
basis of R\'enyi entropies.Comment: 5 pages, 4 figure
Unified entropic measures of quantum correlations induced by local measurements
We introduce quantum correlations measures based on the minimal change in
unified entropies induced by local rank-one projective measurements, divided by
a factor that depends on the generalized purity of the system in the case of
non-additive entropies. In this way, we overcome the issue of the artificial
increasing of the value of quantum correlations measures based on non-additive
entropies when an uncorrelated ancilla is appended to the system without
changing the computability of our entropic correlations measures with respect
to the previous ones. Moreover, we recover as limiting cases the quantum
correlations measures based on von Neumann and R\'enyi entropies (i.e.,
additive entropies), for which the adjustment factor becomes trivial. In
addition, we distinguish between total and semiquantum correlations and obtain
some relations between them. Finally, we obtain analytical expressions of the
entropic correlations measures for typical quantum bipartite systems.Comment: 10 pages, 1 figur
Dispersion of Klauder's temporally stable coherent states for the hydrogen atom
We study the dispersion of the "temporally stable" coherent states for the
hydrogen atom introduced by Klauder. These are states which under temporal
evolution by the hydrogen atom Hamiltonian retain their coherence properties.
We show that in the hydrogen atom such wave packets do not move
quasi-classically; i.e., they do not follow with no or little dispersion the
Keplerian orbits of the classical electron. The poor quantum-classical
correspondence does not improve in the semiclassical limit.Comment: 6 pages, 2 figure
Two-qubit entanglement dynamics for two different non-Markovian environments
We study the time behavior of entanglement between two noninteracting qubits
each immersed in its own environment for two different non-Markovian
conditions: a high- cavity slightly off-resonant with the qubit transition
frequency and a nonperfect photonic band-gap, respectively. We find that
revivals and retardation of entanglement loss may occur by adjusting the
cavity-qubit detuning, in the first case, while partial entanglement trapping
occurs in non-ideal photonic-band gap.Comment: 8 pages, 2 figure
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