12,200 research outputs found
Handbook explaining the fundamentals of nuclear and atomic physics
Indoctrination document presents nuclear, reactor, and atomic physics in an easy, straightforward manner. The entire subject of nuclear physics including atomic structure ionization, isotopes, radioactivity, and reactor dynamics is discussed
Bounded Model Checking of State-Space Digital Systems: The Impact of Finite Word-Length Effects on the Implementation of Fixed-Point Digital Controllers Based on State-Space Modeling
The extensive use of digital controllers demands a growing effort to prevent
design errors that appear due to finite-word length (FWL) effects. However,
there is still a gap, regarding verification tools and methodologies to check
implementation aspects of control systems. Thus, the present paper describes an
approach, which employs bounded model checking (BMC) techniques, to verify
fixed-point digital controllers represented by state-space equations. The
experimental results demonstrate the sensitivity of such systems to FWL effects
and the effectiveness of the proposed approach to detect them. To the best of
my knowledge, this is the first contribution tackling formal verification
through BMC of fixed-point state-space digital controllers.Comment: International Symposium on the Foundations of Software Engineering
201
Investigations on T violation and CPT symmetry in the neutral kaon system -- a pedagogical approach --
During the recent years experiments with neutral kaons have yielded
remarkably sensitive results which are pertinent to such fundamental phenomena
as CPT invariance (protecting causality), time-reversal invariance violation,
coherence of wave functions, and entanglement of kaons in pair states. We
describe the phenomenological developments and the theoretical conclusions
drawn from the experimental material. An outlook to future experimentation is
indicated.Comment: 41 pages, 9 figures. See arXiv:hep-ph/0603075 for an enlarged versio
Ion Trap Mass Spectrometers for Identity, Abundance and Behavior of Volatiles on the Moon
NASA GSFC and The Open University (UK) are collaborating to deploy an Ion Trap Mass Spectrometer on the Moon to investigate the lunar water cycle. The ITMS is flight-proven throughthe Rosetta Philae comet lander mission. It is also being developed under ESA funding to analyse samples drilled from beneath the lunar surface on the Roscosmos Luna-27 lander (2025).Now, GSFC and OU will now develop a compact ITMS instrument to study the near-surface lunar exosphere on board a CLPS Astrobotic lander at Lacus Mortis in 2021
The delayed uncoupled continuous-time random walks do not provide a model for the telegraph equation
It has been alleged in several papers that the so called delayed
continuous-time random walks (DCTRWs) provide a model for the one-dimensional
telegraph equation at microscopic level. This conclusion, being widespread now,
is strange, since the telegraph equation describes phenomena with finite
propagation speed, while the velocity of the motion of particles in the DCTRWs
is infinite. In this paper we investigate how accurate are the approximations
to the DCTRWs provided by the telegraph equation. We show that the diffusion
equation, being the correct limit of the DCTRWs, gives better approximations in
norm to the DCTRWs than the telegraph equation. We conclude therefore
that, first, the DCTRWs do not provide any correct microscopic interpretation
of the one-dimensional telegraph equation, and second, the kinetic (exact)
model of the telegraph equation is different from the model based on the
DCTRWs.Comment: 12 pages, 9 figure
Capillary-gravity waves: The effect of viscosity on the wave resistance
The effect of viscosity on the wave resistance experienced by a 2d
perturbation moving at uniform velocity over the free surface of a fluid is
investigated. The analysis is based on Rayleigh's linearized theory of
capillary-gravity waves. It is shown in particular that the wave resistance
remains bounded as the velocity of the perturbation approches the minimun phase
speed, unlike what is predicted by the inviscid theory.Comment: Europhysics Letters, in pres
Till Studies, Shelburne Vermont
Guidebook for field trips in Vermont: 64th annual meeting October 13, 14, 15, 1972 Burlington, Vermont: Trip G-
Spectral densities for hot QCD plasmas in a leading log approximation
We compute the spectral densities of and in high
temperature QCD plasmas at small frequency and momentum,\, . The leading log Boltzmann equation is reformulated as a Fokker Planck
equation with non-trivial boundary conditions, and the resulting partial
differential equation is solved numerically in momentum space. The spectral
densities of the current, shear, sound, and bulk channels exhibit a smooth
transition from free streaming quasi-particles to ideal hydrodynamics. This
transition is analyzed with conformal and non-conformal second order
hydrodynamics, and a second order diffusion equation. We determine all of the
second order transport coefficients which characterize the linear response in
the hydrodynamic regime.Comment: 39 pages, 6 figures. v3 contains an analysis of the bulk channel with
non-conformal hydrodynamics. Otherwise no significant change
Zitterbewegung of Klein-Gordon particles and its simulation by classical systems
The Klein-Gordon equation is used to calculate the Zitterbewegung (ZB,
trembling motion) of spin-zero particles in absence of fields and in the
presence of an external magnetic field. Both Hamiltonian and wave formalisms
are employed to describe ZB and their results are compared. It is demonstrated
that, if one uses wave packets to represent particles, the ZB motion has a
decaying behavior. It is also shown that the trembling motion is caused by an
interference of two sub-packets composed of positive and negative energy states
which propagate with different velocities. In the presence of a magnetic field
the quantization of energy spectrum results in many interband frequencies
contributing to ZB oscillations and the motion follows a collapse-revival
pattern. In the limit of non-relativistic velocities the interband ZB
components vanish and the motion is reduced to cyclotron oscillations. The
exact dynamics of a charged Klein-Gordon particle in the presence of a magnetic
field is described on an operator level. The trembling motion of a KG particle
in absence of fields is simulated using a classical model proposed by Morse and
Feshbach -- it is shown that a variance of a Gaussian wave packet exhibits ZB
oscillations.Comment: 16 pages and 7 figure
Radiation from perfect mirrors starting from rest and the black body spectrum
We address the question of radiation emission from a perfect mirror that
starts from rest and follows the trajectory z=-ln(cosht) till t->Infinity. We
show that a correct derivation of the black body spectrum via the calculation
of the Bogolubov amplitudes requires consideration of the whole trajectory and
not just of its asymptotic part.Comment: Typos correcte
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