1,442 research outputs found
A variational atomic model of plasma accounting for ion radial correlations and electronic structure of ions (VAMPIRES)
We propose a model of ion-electron plasma (or nucleus-electron plasma) that
accounts for the electronic structure around nuclei (i.e. ion structure) as
well as for ion-ion correlations. The model equations are obtained through the
minimization of an approximate free-energy functional, and it is shown that the
model fulfills the virial theorem. The main hypotheses of this model are 1)
nuclei are treated as classical indistinguishable particles 2) electronic
density is seen as a superposition of a uniform background and
spherically-symmetric distributions around each nucleus (system of ions in a
plasma) 3) free energy is approached using a cluster expansion (non-overlapping
ions) 4) resulting ion fluid is modeled through an approximate integral
equation. In the present paper, the model is described only in its average-atom
version
Study of time lags in HETE-2 Gamma-Ray Bursts with redshift: search for astrophysical effects and Quantum Gravity signature
The study of time lags between spikes in Gamma-Ray Bursts light curves in
different energy bands as a function of redshift may lead to the detection of
effects due to Quantum Gravity. We present an analysis of 15 Gamma-Ray Bursts
with measured redshift, detected by the HETE-2 mission between 2001 and 2006 in
order to measure time lags related to astrophysical effects and search for
Quantum Gravity signature in the framework of an extra-dimension string model.
The use of photon-tagged data allows us to consider various energy ranges.
Systematic effects due to selection and cuts are evaluated. No significant
Quantum Gravity effect is detected from the study of the maxima of the light
curves and a lower limit at 95% Confidence Level on the Quantum Gravity scale
parameter of 3.2x10**15 GeV is set.Comment: 4 pages, 5 figures. v3: Error corrected in Eq. 1. Results updated.
Proceedings of the 30th ICRC, Merida, Mexico (2007
Ephemeral properties and the illusion of microscopic particles
Founding our analysis on the Geneva-Brussels approach to quantum mechanics,
we use conventional macroscopic objects as guiding examples to clarify the
content of two important results of the beginning of twentieth century:
Einstein-Podolsky-Rosen's reality criterion and Heisenberg's uncertainty
principle. We then use them in combination to show that our widespread belief
in the existence of microscopic particles is only the result of a cognitive
illusion, as microscopic particles are not particles, but are instead the
ephemeral spatial and local manifestations of non-spatial and non-local
entities
An active feedback recovery technique from disruption events induced by m=2 n=1 tearing modes in ohmically heated tokamak plasmas
We present experimental results of magnetic feedback control on the m=2, n=1
tearing mode in RFX-mod operated as a circular ohmically heated tokamak. The
feedback suppression of the non-resonant m=2, n=1 Resistive Wall Mode (RWM) in
q(a)<2 plasmas is a well-established result of RFX-mod. The control of the
tearing counterpart, which develops in q(a)>2 equilibrium, is instead a more
difficult issue. In fact, the disruption induced by a growing amplitude m=2,
n=1 tearing mode can be prevented by feedback only when the resonant surface
q=2 is close to the plasma edge, namely 2<q(a)<2.5, and the electron density
does not exceed approximately half of the Greenwald limit. A combined technique
of tearing mode and q(a) control has been therefore developed to recover the
discharge from the most critical conditions: the potentially disruptive tearing
mode is converted into the relatively benign RWM by suddenly decreasing q(a)
below 2. The experiments demonstrate the concept with 100% of successful cases.
The q(a) control has been performed through the plasma current, given the
capability of the toroidal loop-voltage power supply of RFX-mod. We also
propose a path for controlling q(a) by acting on the plasma shape, which could
be applied to medium size elongated tokamaks
The dud detector: An empirically-based real-time algorithm to save neutron and T budgets during JET DT operation
Thermodynamic coherence of the Variational Average-Atom in Quantum Plasmas (VAAQP) approach
A new code called VAAQP (Variational Average-Atom in Quantum Plasmas) is
reported. The model as well as main results of previous studies are briefly
recalled. The code is based on a new fully variational model of dense plasmas
at equilibrium with quantum treatment of all electrons. The code can calculate
the Average Atom structure and the mean ionization from the variational
equations respecting the virial theorem and without imposing the neutrality of
the Wigner-Seitz sphere. The formula obtained for the electronic pressure is
simple and does not require any numerical differentiation. A description of the
principal features of the code is given. The thermodynamic consistency of the
results obtained with VAAQP is shown by a comparison with another approach on
the example of the aluminium 10 eV isotherm EOS curve. A first comparison to an
INFERNO-type model is also presented
How Events Come Into Being: EEQT, Particle Tracks, Quantum Chaos, and Tunneling Time
In sections 1 and 2 we review Event Enhanced Quantum Theory (EEQT). In
section 3 we discuss applications of EEQT to tunneling time, and compare its
quantitative predictions with other approaches, in particular with
B\"uttiker-Larmor and Bohm trajectory approach. In section 4 we discuss quantum
chaos and quantum fractals resulting from simultaneous continuous monitoring of
several non-commuting observables. In particular we show self-similar,
non-linear, iterated function system-type, patterns arising from quantum jumps
and from the associated Markov operator. Concluding remarks pointing to
possible future development of EEQT are given in section 5.Comment: latex, 27 pages, 7 postscript figures. Paper submitted to Proc.
Conference "Mysteries, Puzzles And Paradoxes In Quantum Mechanics, Workshop
on Entanglement And Decoherence, Palazzo Feltrinelli, Gargnano, Garda Lake,
Italy, 20-25 September, 199
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