2,816 research outputs found
Generalization of the Schott energy in electrodynamic radiation theory
We discuss the origin of the Schott energy in the Abraham-Lorentz version of
electrodynamic radiation theory and how it can be used to explain some apparent
paradoxes. We also derive the generalization of this quantity for the
Ford-O'Connell equation, which has the merit of being derived exactly from a
microscopic Hamiltonian for an electron with structure and has been shown to be
free of the problems associated with the Abraham-Lorentz theory. We emphasize
that the instantaneous power supplied by the applied force not only gives rise
to radiation (acceleration fields), but it can change the kinetic energy of the
electron and change the Schott energy of the velocity fields. The important
role played by boundary conditions is noted
A quantum violation of the second law?
An apparent violation of the second law of thermodynamics occurs when an atom
coupled to a zero-temperature bath, being necessarily in an excited state, is
used to extract work from the bath. Here the fallacy is that it takes work to
couple the atom to the bath and this work must exceed that obtained from the
atom. For the example of an oscillator coupled to a bath described by the
single relaxation time model, the mean oscillator energy and the minimum work
required to couple the oscillator to the bath are both calculated explicitly
and in closed form. It is shown that the minimum work always exceeds the mean
oscillator energy, so there is no violation of the second law
Consistency of a Causal Theory of Radiative Reaction with the Optical Theorem
The Abraham-Lorentz-Dirac equation for a point electron, while suffering from
runaway solutions and an acausal response to external forces, is compatible
with the optical theorem. We show that a theory of radiative reaction that
allows for a finite charge distribution is not only causal and free of runaway
solutions, but is also consistent with the optical theorem and the standard
formula for the Rayleigh scattering cross section.Comment: 4 pages, 2 figure
Does the Third Law of Thermodynamics hold in the Quantum Regime?
The first in a long series of papers by John T. Lewis,
G. W. Ford and the present author, considered the problem of the most general
coupling of a quantum particle to a linear passive heat bath, in the course of
which they derived an exact formula for the free energy of an oscillator
coupled to a heat bath in thermal equilibrium at temperature T. This formula,
and its later extension to three dimensions to incorporate a magnetic field,
has proved to be invaluable in analyzing problems in quantum thermodynamics.
Here, we address the question raised in our title viz. Nernst's third law of
thermodynamics
Signatures of the Youngest Starbursts: Optically-thick Thermal Bremsstrahlung Radio Sources in Henize 2-10
VLA radio continuum imaging reveals compact (<8 pc) ~1 mJy radio sources in
the central 5" starburst region of the blue compact galaxy Henize 2-10. We
interpret these radio knots as extremely young, ultra-dense HII regions. We
model their luminosities and spectral energy distributions, finding that they
are consistent with unusually dense HII regions having electron densities, 1500
cm^-3 < n_e < 5000 cm^-3, and sizes of 3-8 pc. Since these H II regions are not
visible in optical images, we propose that the radio data preferentially reveal
the youngest, densest, and most highly obscured starforming events. Energy
considerations imply that each of the five \HII regions contains ~750 O7V
equivalent stars, greater than the number found in 30 Doradus in the LMC. The
high densities imply an over-pressure compared to the typical interstellar
medium so that such objects must be short-lived (<0.5 Myr expansion
timescales). We conclude that the radio continuum maps reveal the very young
(<0.5 Myr) precursors of ``super starclusters'' or ``proto globular clusters''
which are prominent at optical and UV wavelengths in He 2-10. If the
ultra-dense HII regions are typical of those which we predict will be found in
other starbursting systems, then super starclusters spend 15% of their lifetime
in heavily-obscured environments, similar to Galactic ultra-compact HII
regions. This body of work leads us to propose that massive extragalactic star
clusters (i.e. proto globular clusters) with ages <10^6 yr may be most easily
identified by finding compact radio sources with optically-thick thermal
bremsstrahlung spectral signatures.Comment: AASTeX, 8 figures 2 included with psfig in text; other 6 in jpeg
format; Postscript versions of figures may be found at
http://zem.ucolick.org/chip/Research/young_clusters.html -- Accepted for
publication in the Astrophysical Journa
Anomalous diffusion in quantum Brownian motion with colored noise
Anomalous diffusion is discussed in the context of quantum Brownian motion
with colored noise. It is shown that earlier results follow simply and directly
from the fluctuation-dissipation theorem. The limits on the long-time
dependence of anomalous diffusion are shown to be a consequence of the second
law of thermodynamics. The special case of an electron interacting with the
radiation field is discussed in detail. We apply our results to wave-packet
spreading
Quantum collapse in ground-state Fermi-Dirac-Landau plasmas
It is revealed that in a relativistically degenerate dense highly-magnetized
electron-ion plasma the effective quantum-potential due to the total
quantum-force acting on fermions may cancel-out causing a quantum transverse
collapse in the ground-state Fermi-Dirac-Landau (GSFDL) plasma. The condition
for the plasma transverse collapse is found to be restricted to the minimum
relativistic degeneracy parameter and minimum impressed magnetic field strength
values satisfied for many superdense astrophysical objects such as white dwarfs
and neutron stars. In such plasmas, the magnetization pressure is shown to
cancel the lateral electron degeneracy pressure counteracting the existing
gravitational pressure. Furthermore, using the Sagdeev pseudopotential method
in the framework of quantum magnetohydrodynamics (QMHD) model including spin
magnetization it is confirmed that the quantum pressure due to spin-orbit
polarization and the electron relativistic degeneracy has significant effects
on the existence criteria and the propagation of localized magnetosonic density
excitations in GSFDL plasmas. Current findings can have important implications
for the density excitations mechanism and gravitational collapse of the highly
magnetized astrophysical relativistically dense objects such as white-dwarfs,
neutron stars, magnetars and pulsars.Comment: To be Published in Journal Physics of Plasma
Nonlinear Excitations in Strongly-Coupled Fermi-Dirac Plasmas
In this paper we use the conventional quantum hydrodynamics (QHD) model in
combination with the Sagdeev pseudopotential method to explore the effects of
Thomas-Fermi nonuniform electron distribution, Coulomb interactions, electron
exchange and ion correlation on the large-amplitude nonlinear soliton dynamics
in Fermi-Dirac plasmas. It is found that in the presence of strong interactions
significant differences in nonlinear wave dynamics of Fermi-Dirac plasmas in
the two distinct regimes of nonrelativistic and relativistic degeneracies
exist. Furthermore, it is remarked that first-order corrections due to such
interactions (which are proportional to the fine-structure constant) are
significant on soliton dynamics in nonrelativistic plasma degeneracy regime
rather than relativistic one. In the relativistic degeneracy regime, however,
these effects become less important and the electron quantum-tunneling and
Pauli-exclusion dominate the nonlinear wave dynamics. Hence, application of
non-interacting Fermi-Dirac QHD model to study the nonlinear wave dynamics in
quantum plasmas such as compact stars is most appropriate for the relativistic
degeneracy regime
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