arXiv
(422.153 recursos)
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Mostrando recursos 1 - 20 de 20.975
1.
Exo-interferometric Phase Determination of X rays - Sturhahn, Wolfgang; L'abbe, Caroline; Toellner, Thomas S.
The time-dependent phase change of x rays after transmission through a sample
has been determined experimentally. We used an x-ray interferometer with a
reference sample containing sharp nuclear resonances to prepare a
phase-controlled x-ray beam. A sample with similar resonances was placed in the
beam but outside of the interferometer; hence our use of the term
``exo-interferometric.'' We show that the phase change of the x rays due to the
sample can be uniquely determined from the time-dependent transmitted
intensities. The energy response of the sample was reconstructed from the phase
and the intensity data with a resolution of 23neV.
2.
Spin and Statistics in Classical Mechanics - Morgan, J. A.
The spin-statistics conection is obtained for classical point particles. The
connection holds within pseudomechanics, a theory of particle motion that
extends classical physics to include anticommuting Grassmann variables, and
which exhibits classical analogs of both spin and statistics. Classical
realizations of Lie groups can be constructed in a canonical formalism
generalized to include Grassmann variables. The theory of irreducible canonical
realizations of the Poincare group is developed in this framework, with
particular emphasis on the rotation subgroup. The behavior of irreducible
realizations under time inversion and charge conjugation is obtained. The
requirement that the Lagrangian retain its form under the cominbed operation CT
leads directly to the spin-statistics connection, by...
3.
What object does the wave function describe? - Rylov, Yuri A.
It is shown that the wave function describes the state of the statistical
ensemble E[S] of individual particles, or the statistical average particle .
This result follows from the fact that in the classical limit h=0 the
Schroedinger equation turns to the dynamic equations for the statistical
ensemble of classical particles. The statement that the wave function describes
the state of an individual particle is incompatible with the quantum mechanics
formalism. It is shown that the statistical interpretation of quantum mechanics
is a corollary of the fact, that the QM formalism is the technique of the
statistical ensemble description, restricted by constraints of the dynamic
equation linearity.
4.
Physical model for the latent heat of fusion - Garai, Jozsef
The atomic movement induced on melting has to overcome a viscous drag
resistance. It is suggested that the latent heat of fusion supplies the
required energy for this physical process. The viscosity model introduced here
allows computation of the latent heat from viscosity, molar volume, melting
temperature, and atomic mass and diameter. The correlation between these
parameters and the latent heat of 14 elements with body and face centered cubic
structures was exceptional, with the correlation coefficients of 0.97 and 0.95
respectively.
5.
Drawing Particle Symbols and Feynman Diagrams with Office - Cakir, Orhan
Particle symbols and Feynman diagrams often used in particle physics can be
generated by a word document processor. Standard office packages have their
built in symbols such as solid-line, dashed-line, arrows, etc. which are also
used in particle physics. Three symbols corresponding to photon, gluon and
fermion line are not present in the standard office packages. By importing
these two symbols and using the built in symbols, tree-level Feynman diagrams
can be easily generated in an office program.
6.
Adaptive observer scheme for a three-parameter free damped oscillator - Ibarra-Junquera, V.; Rosu, H. C.; Cornejo-Perez, O.
We apply the recent adaptive observer scheme introduced by Besancon et al
(2004) to the three-parameter free damped oscillator obtained in 1998 by Rosu
and Reyes by factorization methods. In order to do this, the scheme is applied
in a nonstandard form in which a time-varying quantity containing the unknown
value of the Riccati parameter is estimated. Results of computer simulations
are presented to illustrate the good feasibility of the approach
7.
Eigenmodes of index-modulated layers with lateral PMLs - Skigin, Diana C.
Maxwell equations are solved in a layer comprising a finite number of
homogeneous isotropic dielectric regions ended by anisotropic perfectly matched
layers (PMLs). The boundary-value problem is solved and the dispersion relation
inside the PML is derived. The general expression of the eigenvalues equation
for an arbitrary number of regions in each layer is obtained, and both
polarization modes are considered. The modal functions of a single layer ended
by PMLs are found, and their orthogonality relation is derived. The present
method is useful to simulate scattering problems from dielectric objects as
well as propagation in planar slab waveguides. Its potential to deal with more
complex problems such as...
8.
On the motion of a classical charged particle - Aguirregabiria, J. M.; Llosa, J.; Molina, A.
We show that the Lorentz-Dirac equation is not an unavoidable consequence of
energy-momentum conservation for a point charge. What follows solely from
conservation laws is a less restrictive equation already obtained by Honig and
Szamosi. The latter is not properly an equation of motion because, as it
contains an extra scalar variable, it does not determine the future evolution
of the charge. We show that a supplementary constitutive relation can be added
so that the motion is determined and free from the troubles that are customary
in Lorentz-Dirac equation, i. e. preacceleration and runaways.
9.
Optical coherence properties of planar microcavity emission - Oulton, R. F.; Stavrinou, P. N.; Parry, G.
An analytical expression for the self coherence function of a microcavity and
partially coherent source is derived from first principles in terms of the
component self coherence functions. Excellent agreement between the model and
experimental measurements of two Resonant Cavity LEDs (RCLEDs) is evident. The
variation of coherence length as a function of numerical aperture is also
described by the model. This is explained by a microcavity's angular
sensitivity in filtering out statistical fluctuations of the underlying light
source. It is further demonstrated that the variable coherence properties of
planar microcavities can be designed by controlling the underlying coherences
of microcavity and emitter whereby coherence lengths ranging over nearly...
10.
Studies of Lanthanides 6s Ionization Energy - Gaigalas, G.; Rudzikas, Z.; Zalandauskas, T.
This work is aimed at the multi-configuration Hartree-Fock calculations of
the 6s ionization energies of lanthanides with configurations [Xe]4f^{N}6s^{2}.
Authors have used the ATSP MCHF version in which there are new codes for
calculation of spin-angular parts of matrix elements of the operators of
intraatomic interactions written on the basis of the methodology Gaigalas,
Rudzikas and Froese Fischer, based on the second quantization in coupled
tensorial form, the angular momentum theory in 3 spaces (orbital, spin and
quasispin), graphical technique of spin-angular integrations and reduced
coefficients (subcoefficients) of fractional parentage. This methodology allows
us to study the configurations with open f-shells without any restrictions,
thus providing the possibility to investigate...
11.
Charged State of a Spherical Plasma in Vacuum - Cornolti, F.; Ceccherini, F.; Betti, S.; Pegoraro, F.
The stationary state of a spherically symmetric plasma configuration is
investigated in the limit of immobile ions and weak collisions. Configurations
with small radii are positively charged as a significant fraction of the
electron population evaporates during the equilibration process, leaving behind
an electron distribution function with an energy cutoff. Such charged plasma
configurations are of interest for the study of Coulomb explosions and ion
acceleration from small clusters irradiated by ultraintense laser pulses and
for the investigation of ion bunches propagation in a plasma.
12.
Influence and Inference in Bell's Theorem - Potvin, Guy
Jaynes' criticism of Bell's theorem is examined. It is found that Bell's
reasoning leading to his theorem is sound when properly interpreted. The nature
of physical influence and logical inference in quantum mechanics, and its
relationship with the notions of realism and locality, is discussed.
13.
Group velocity of the acoustic eigen-modes in sonic crystals - Ye, Zhen
In this brief report, the group velocity of the eigen-modes in sonic crystals
is derived, and shown to equal the averaged energy velocity of the eigen-modes.
How the group velocity can be used to describe acoustic energy flows in sonic
crystals is discussed.
14.
Two Common Misconceptions about the Theory of Special Relativity - Bakhoum, Ezzat G.
Two common misconceptions about the theory of Special Relativity that are
actively taught in textbooks are discussed. It is shown, first, that the
Lorentz transformations are actually transformations of the coordinates of a
photon, not the coordinates of a particle as taught by some authors. Secondly,
a misconception concerning the relativistic Lagrangian is discussed. It is
shown that the currently accepted formulation of the Lagrangian is missing an
important constant of integration. By incorporating the missing constant of
integration, the new Lagrangian directly supports the conclusions reached
previously by the author concerning the mass-energy equivalence principle.
15.
Theoretical calculation of the surface energy of water - Ogawa, Naohisa; Matsuura, Yoshiki
The estimation of the surface tension of water is theoretically dealt on the
basis of the dipole molecular model. It is known that the experimentally
determined surface tension of freshly exposed surface has a higher value than
the nominal value of 73 [mN/m]. We calculated the value corresponding to the
fresh surface where the reorientation of the molecules has not occurred.
16.
A Sensitivity Study for a MICE Liquid Hydrogen Absorber - Errede, D.; Rakhno, I.
The International Muon Ionization Cooling Experiment (MICE) is devoted to a
study of a muon cooling channel capable of giving the desired performance for a
Neutrino Factory. One of the goals is achieving an absolute accuracy of
measurements of emittance reduction as high as 0.1%. The paper describes
results of a Monte Carlo study on allowed density variations of liquid hydrogen
corresponding to the desired accuracy of the measurements.
17.
A Sketch for a Quantum Theory of Gravitity - Gilson, J. G.
The numerical quantum electronic structure for the energies of the states of
the hydrogen like atoms as given by Sommerfeld in 1915-16 is studied and is
shown to present a scheme that is able to express a unique observer point of
view. The perspective of this observer is essentially how he, if fixed on a
trapped electron, would see his and his electron's state of containment within
the full atomic quantum state. This particular internal view of a quantum state
is then shown to have strong analytic powers in the extremely different
numerical scale of gravitation theory. This unexpected analogy becomes possible
when it is recognised that a...
18.
Spatial snowdrift game with myopic agents - Sysi-Aho, Marko; Saramaki, Jari; Kertesz, Janos; Kaski, Kimmo
We have studied a spatially extended snowdrift game, in which the players are
located on the sites of two-dimensional square lattices and repeatedly have to
choose one of the two strategies, either cooperation (C) or defection (D). A
player interacts with its nearest neighbors only, and aims at playing a
strategy which maximizes its instant pay-off, assuming that the neighboring
agents retain their strategies. If a player is not content with its current
strategy, it will change it to the opposite one with probability $p$ next
round. Here we show through simulations and analytical approach that these
rules result in cooperation levels, which differ to large extent from...
19.
Bound-state corrections in laser-induced nonsequential double ionization - Faria, C. Figueira de Morisson; Lewenstein, M.
We perform a systematic analysis of how nonsequential double ionization in
intense, linearly polarized laser fields is influenced by the initial states in
which both electrons are bound, and by the residual ionic potential. We assume
that the second electron is released by electron-impact ionization of the first
electron with its parent ion, using an S-Matrix approach. We work within the
Strong-Field Approximation, and compute differential electron momentum
distributions using saddle-point methods. Specifically, we consider electrons
in $1s$, $2p$, $3p$ and localized states, which are released by either a
contact or a Coulomb-type interaction. We also perform an adequate treatment of
the bound-state singularity which is present in this...
1.
