2,908 research outputs found
Radiation Damping and Quantum Excitation for Longitudinal Charged Particle Dynamics in the Thermal Wave Model
On the basis of the recently proposed {\it Thermal Wave Model (TWM) for
particle beams}, we give a description of the longitudinal charge particle
dynamics in circular accelerating machines by taking into account both
radiation damping and quantum excitation (stochastic effect), in presence of a
RF potential well. The longitudinal dynamics is governed by a 1-D
Schr\"{o}dinger-like equation for a complex wave function whose squared modulus
gives the longitudinal bunch density profile. In this framework, the
appropriate {\it r.m.s. emittance} scaling law, due to the damping effect, is
naturally recovered, and the asymptotic equilibrium condition for the bunch
length, due to the competition between quantum excitation (QE) and radiation
damping (RD), is found. This result opens the possibility to apply the TWM,
already tested for protons, to electrons, for which QE and RD are very
important.Comment: 10 pages, plain LaTeX; published in Phys. Lett. A194 (1994) 113-11
Full Phase-Space Analysis of Particle Beam Transport in the Thermal Wave Model
Within the Thermal Wave Model framework a comparison among Wigner function,
Husimi function, and the phase-space distribution given by a particle tracking
code is made for a particle beam travelling through a linear lens with small
aberrations. The results show that the quantum-like approach seems to be very
promising.Comment: 15 pages, plain LaTeX, + 3 uuencoded figures, to be published in
Phys. Lett.
Coherent States for Particle Beams in the Thermal Wave Model
In this paper, by using an analogy among {\it quantum mechanics}, {\it
electromagnetic beam optics in optical fibers}, and {\it charge particle beam
dynamics}, we introduce the concept of {\it coherent states} for charged
particle beams in the framework of the {\it Thermal Wave Model} (TWM). We give
a physical meaning of the Gaussian-like coherent structures of charged particle
distribution that are both naturally and artificially produced in an
accelerating machine in terms of the concept of coherent states widely used in
quantum mechanics and in quantum optics. According to TWM, this can be done by
using a Schr\"{o}dinger-like equation for a complex function, the so-called
{\it beam wave function} (BWF), whose squared modulus is proportional to the
transverse beam density profile, where Planck's constant and the time are
replaced by the transverse beam emittance and by the propagation coordinate,
respectively. The evolution of the particle beam, whose initial BWF is assumed
to be the simplest coherent state (ground-like state) associated with the beam,
in an infinite 1-D quadrupole-like device with small sextupole and octupole
aberrations, is analytically and numerically investigated.Comment: 21 pages, Late
Inconstant Planck's constant
Motivated by the Dirac idea that fundamental constant are dynamical variables
and by conjectures on quantum structure of spacetime at small distances, we
consider the possibility that Planck constant is a time depending
quantity, undergoing random gaussian fluctuations around its measured constant
mean value, with variance and a typical correlation timescale
. We consider the case of propagation of a free particle and a
one--dimensional harmonic oscillator coherent state, and show that the time
evolution in both cases is different from the standard behaviour. Finally, we
discuss how interferometric experiments or exploiting coherent electromagnetic
fields in a cavity may put effective bounds on the value of .Comment: To appear on the International Journal of Modern Physics
Intramyocardial hemorrhage: An enigma for cardiac MRI?
Cardiovascular magnetic resonance (CMR) is a useful noninvasive technique for determining the presence of microvascular obstruction (MVO) and intramyocardial hemorrhage (IMH), frequently occurring in patients after reperfused myocardial infarction (MI). MVO, or the so-called no-reflow phenomenon, is associated with adverse ventricular remodeling and a poor prognosis during follow-up. Similarly, IMH is considered a severe damage after revascularization by percutaneous primary coronary intervention (PPCI) or fibrinolysis, which represents a worse prognosis. However, the pathophysiology of IMH is not fully understood and imaging modalities might help to better understand that phenomenon. While, during the past decade, several studies examined the distribution patterns of late gadolinium enhancement with different CMR sequences, the standardized CMR protocol for assessment of IMH is not yet well established. The aim of this review is to evaluate the available literature on this issue, with particular regard to CMR sequences. New techniques, such as positron emission tomography/magnetic resonance imaging (PET/MRI), could be useful tools to explore molecular mechanisms of the myocardial infarction healing process
The thermal-wave model: A Schroedinger-like equation for charged particle beam dynamics
We review some results on longitudinal beam dynamics obtained in the framework of the Thermal Wave Model (TWM). In this model, which has recently shown the capability to describe both longitudinal and transverse dynamics of charged particle beams, the beam dynamics is ruled by Schroedinger-like equations for the beam wave functions, whose squared modulus is proportional to the beam density profile. Remarkably, the role of the Planck constant is played by a diffractive constant epsilon, the emittance, which has a thermal nature
Optical and infrared properties of V1647 Orionis during the 2003-2006 outburst. II. Temporal evolution of the eruptive source
The occurrence of new FU Orionis-like objects is fundamental to understand
the outburst mechanism in young stars and their role in star formation and disk
evolution. Our work is aimed at investigating the properties of the recent
outburst of V1647 Ori. Using optical and mid infrared long slit spectroscopy we
monitored V1647 Ori in outburst between February 2004 and January 2006. The
optical spectrum is characterized by Halpha and Hbeta in P-Cygni profile and by
many weak FeI and FeII emission lines. Short timescale variability was measured
in the continuum and line emission. On January 2006 we detected for the first
time forbidden emission lines ([OI], [SII] and [FeII]). These lines are likely
produced by an Herbig-Haro object driven by V1647 Ori. The mid infrared the
spectrum of V1647 Ori is flat and featureless at all epochs. The SED changed
drastically: the source was much redder in the early outburst than in the final
phase. The magnitude rise and the SED of V1647 Ori resembles that of a FUor
while the duration and recurrence of the outburst resemble that of a EXor. The
optical spectrum is clearly distinct from either the absorption line spectrum
of a FUor or the T Tauri-like spectrum of an EXor. Our data are consistent with
a disk instability event which led to an increase of the mass accretion rate.
The data also suggest the presence of a circumstellar envelope around the
star+disk system. The peculiar N band spectrum might be explained by dust
sublimation in the outer layers of the disk. The presence of the envelope and
the outburst statistics suggest that these instability events occur only in a
specific stage of a Class I source (e.g. in the transition phase to an
optically visible star surrounded by a protoplanetary disk). We discuss the
outburst mechanisms in term of the thermal instability model.Comment: 12 pages, 7 figures, accepted for publication in A&
A Deadbeat Observer for Two and Three-dimensional LTI Systems by a Time/Output-Dependent State Mapping
The problem of deadbeat state reconstruction for non-autonomous linear systems
has been solved since several decades, but all the architectures formulated since now require
either high-gain output injection, which amplifies measurement noises (e.g., in the case of
sliding-mode observers), either state augmentation, which yields a non-minimal realization of
the deadbeat observer (e.g., in the case of integral methods and delay-based methods). In this
context, the present paper presents, for the first time, a finite-time observer for continuous-time
linear systems enjoying minimal linear-time-varying dynamics, that is, the observer has the same
order of the observed system. The key idea behind the proposed method is the introduction of
an almost-always invertible time/output-dependent state mapping which allows to recast the
dynamics of the system in a new observer canonical form whose initial conditions are known
Kinematics signature of a giant planet in the disk of AS 209
[abridged] ALMA observations of dust in protoplanetary disks are revealing
the existence of sub-structures such as rings, gaps and cavities. Such
morphology are expected to be the outcome of dynamical interaction between the
disk and planets. However, other mechanisms are able to produce similar dust
sub-structures. A solution is to look at the perturbation induced by the planet
to the gas surface density and/or to the kinematics. In the case of the disk
around AS 209, a prominent gap has been reported in the surface density of CO
at au. Recently, Bae et al. (2022) detected a localized velocity
perturbation in the CO emission along with a clump in CO
at nearly 200 au, interpreted as a gaseous circumplanetary disk. We
report a new analysis of ALMA archival observations of CO and CO
J=2-1. A clear kinematics perturbation (kink) is detected in multiple channels
and over a wide azimuth range in both dataset. We compared the observed
perturbation with a semi-analytic model of velocity perturbations due to
planet-disk interaction. The observed kink is not consistent with a planet at
200\,au as this would require a low gas disk scale height () in
contradiction with previous estimate ( at au). When
we fix the disk scale height to 0.118 (at au) we find instead that a
planet of 3-5 M at 100 au induces a kinematics perturbation similar
to the observed one. Thus, we conclude that a giant protoplanet orbiting at au is responsible of the large scale kink as well as of the
perturbed dust and gas surface density previously detected. The position angle
of the planet is constrained to be between 60-100. Future
observations with high contrast imaging technique in the near- and mid-
infrared are needed to confirm the presence and position of such a planet.Comment: Accepted by A&
Volterra's kernels-based finite-time parameters estimation of the Chua system
In this work, the unknown set of parameters of the Chua system is recovered under the hypothesis that the voltages of the capacitors are available. The system is shown to be algebraically observable and identifiable with respect to the chosen outputs. Focusing on the differential equations, the Volterra kernel-based approach is used to perform an estimation without the uncertainty of the unmeasurable derivatives and the unknown initial conditions
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