1,604 research outputs found
Brownian motion of a charged test particle near a reflecting boundary at finite temperature
We discuss the random motion of charged test particles driven by quantum
electromagnetic fluctuations at finite temperature in both the unbounded flat
space and flat spacetime with a reflecting boundary and calculate the mean
squared fluctuations in the velocity and position of the test particle. We show
that typically the random motion driven by the quantum fluctuations is one
order of magnitude less significant than that driven by thermal noise in the
unbounded flat space. However, in the flat space with a reflecting plane
boundary, the random motion of quantum origin can become much more significant
than that of thermal origin at very low temperature.Comment: 11 pages,no figures, Revtex
Markov evolutions and hierarchical equations in the continuum I. One-component systems
General birth-and-death as well as hopping stochastic dynamics of infinite
particle systems in the continuum are considered. We derive corresponding
evolution equations for correlation functions and generating functionals.
General considerations are illustrated in a number of concrete examples of
Markov evolutions appearing in applications.Comment: 47 page
Does the Babcock--Leighton Mechanism Operate on the Sun?
The contribution of the Babcock-Leighton mechanism to the generation of the
Sun's poloidal magnetic field is estimated from sunspot data for three solar
cycles. Comparison of the derived quantities with the A-index of the
large-scale magnetic field suggests a positive answer to the question posed in
the title of this paper.Comment: 5 pages, 2 figures, to apper in Astronomy Letter
On the stability of black hole event horizons
In this work we study a {\it gedanken} experiment constructed in order to
test the cosmic censorship hypothesis and the second law of black hole
thermo-dynamics. Matter with a negative gravitating energy is imagined added to
a near extremal -charged static black hole in Einstein-Maxwell theory.
The dynamics of a similar process is studied and the thermo-dynamical
properties of the resulting black hole structure is discussed. A new mechanism
which stabilizes black hole event horizons is shown to operate in such
processes.Comment: 16, grammatical errors corrected and two references adde
Simulation of wavepacket tunneling of interacting identical particles
We demonstrate a new method of simulation of nonstationary quantum processes,
considering the tunneling of two {\it interacting identical particles},
represented by wave packets. The used method of quantum molecular dynamics
(WMD) is based on the Wigner representation of quantum mechanics. In the
context of this method ensembles of classical trajectories are used to solve
quantum Wigner-Liouville equation. These classical trajectories obey
Hamilton-like equations, where the effective potential consists of the usual
classical term and the quantum term, which depends on the Wigner function and
its derivatives. The quantum term is calculated using local distribution of
trajectories in phase space, therefore classical trajectories are not
independent, contrary to classical molecular dynamics. The developed WMD method
takes into account the influence of exchange and interaction between particles.
The role of direct and exchange interactions in tunneling is analyzed. The
tunneling times for interacting particles are calculated.Comment: 11 pages, 3 figure
Electronic Structure of Disclinated Graphene in an Uniform Magnetic Field
The electronic structure in the vicinity of the 1-heptagonal and 1-pentagonal
defects in the carbon graphene plane is investigated. Using a continuum gauge
field-theory model the local density of states around the Fermi energy is
calculated for both cases. In this model, the disclination is represented by an
SO(2) gauge vortex and corresponding metric follows from the elasticity
properties of the graphene membrane. To enhance the interval of energies, a
self-consistent perturbation scheme is used. The Landau states are investigated
and compared with the predicted values.Comment: keywords: graphene, heptagonal defect, elasticity, carbon nanohorns,
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