1,081 research outputs found
New relations between spinor and scalar one-loop effective Lagrangians in constant background fields
Simple new relations are presented between the one-loop effective Lagrangians
of spinor and scalar particles in constant curvature background fields, both
electromagentic and gravitational. These relations go beyond the well-known
cases for self-dual background fields
High time resolution observation of the transient event of 5 March 1979
The detection of an intense gamma ray burst with the monitor proportional counter on the HEAO 2 spacecraft is discussed with particular emphasis on the measurement of the time of onset of the event. Based on the mean observed counting rate in the burst and assuming a sharp rise, the uncertainty in the burst onset is found to be + or - 220 microseconds. The time of occurrence was 57124.826908 + or - 0.000220 s UT on March 5, 1979, and the location of the HEAO 2 satellite at this time was latitude 22.15 deg, longitude -27.60 deg at an altitude of 525.0 km
QED One-loop Corrections to a Macroscopic Magnetic Dipole
We consider the field equations of a static magnetic field including one-loop
QED corrections, and calculate the corrections to the field of a magnetic
dipole.
PACS: 12.20.Ds, 97.60.Jd, 97.60.GbComment: 11 pages, 4 figures, to appear in Journal of Physics
Influence of radiative damping on the optical-frequency susceptibility
Motivated by recent discussions concerning the manner in which damping
appears in the electric polarizability, we show that (a) there is a dependence
of the nonresonant contribution on the damping and that (b) the damping enters
according to the "opposite sign prescription." We also discuss the related
question of how the damping rates in the polarizability are related to
energy-level decay rates
Singularity-Free Electrodynamics for Point Charges and Dipoles: Classical Model for Electron Self-Energy and Spin
It is shown how point charges and point dipoles with finite self-energies can
be accomodated into classical electrodynamics. The key idea is the introduction
of constitutive relations for the electromagnetic vacuum, which actually
mirrors the physical reality of vacuum polarization. Our results reduce to
conventional electrodynamics for scales large compared to the classical
electron radius cm. A classical simulation for a
structureless electron is proposed, with the appropriate values of mass, spin
and magnetic moment.Comment: 3 page
Dissipation in a 2-dimensional Hilbert space: Various forms of complete positivity
We consider the time evolution of the density matrix in a
2-dimensional complex Hilbert space. We allow for dissipation by adding to the
von Neumann equation a term , which is of Lindblad type in order to
assure complete positivity of the time evolution. We present five equivalent
forms of . In particular, we connect the familiar dissipation matrix
with a geometric version of , where consists of a positive sum
of projectors onto planes in . We also study the minimal number
of Lindblad terms needed to describe the most general case of . All
proofs are worked out comprehensively, as they present at the same time a
practical procedure how to determine explicitly the different forms of
. Finally, we perform a general discussion of the asymptotic behaviour
of the density matrix and we relate the two types of asymptotic
behaviour with our geometric version of .Comment: 11 pages, LaTeX, no figures. Further aspects of complete positivity
worked out and references added; version accepted for publication in Phys.
Lett.
QED vacuum fluctuations and induced electric dipole moment of the neutron
Quantum fluctuations in the QED vacuum generate non-linear effects, such as
peculiar induced electromagnetic fields. In particular, we show here that an
electrically neutral particle, possessing a magnetic dipole moment, develops an
induced electric dipole-type moment with unusual angular dependence, when
immersed in a quasistatic, constant external electric field. The calculation of
this effect is done in the framework of the Euler-Heisenberg effective QED
Lagrangian, corresponding to the weak field asymptotic expansion of the
effective action to one-loop order. It is argued that the neutron might be a
good candidate to probe this signal of non-linearity in QED.Comment: A misprint has been corrected, and three new references have been
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