6,378 research outputs found
Proposed New Test of Spin Effects in General Relativity
The recent discovery of a double-pulsar PSR J0737-3039A/B provides an
opportunity of unequivocally observing, for the first time, spin effects in
general relativity. Existing efforts involve detection of the precession of the
spinning body itself. However, for a close binary system, spin effects on the
orbit may also be discernable. Not only do they add to the advance of the
periastron (by an amount which is small compared to the conventional
contribution) but they also give rise to a precession of the orbit about the
spin direction. The measurement of such an effect would also give information
on the moment of inertia of pulsars
The Equation of Motion of an Electron
The claim by Rohrlich that the Abraham-Lorentz-Dirac equation is not the
correct equation for a classical point charge is shown to be incorrect and it
is pointed out that the equation which he proposes is the equation
{\underline{derived}} by Ford and O'Connell for a charge with structure. The
quantum-mechanical case is also discussed
Stochastic Methods in Atomic Systems and QED
We show that treating the blackbody radiation field as a heat bath enables
one to utilize powerful techniques from the realm of stochastic physics (such
as the fluctuation-dissipation theorem and the related radiation damping) in
order to treat problems that could not be treated rigorously by conventional
methods. We illustrate our remarks by discussing specifically the effect of
temperature on atomic spectral lines, and the solution to the problem of
runaway solutions in the equation of motion of a radiating electron. We also
present brief discussions relating to anomalous diffusion and wave packet
spreading in a radiation field and the influence of quantum effects on the laws
of thermodynamics.Comment: Contribution to the Festschrift in honor of Professor Walter R.
Johnson on the occasion of his retirement after 50 years at the University of
Notre Dam
Fluctuations and Noise: A General Model with Applications
A wide variety of dissipative and fluctuation problems involving a quantum
system in a heat bath can be described by the independent-oscillator (IO) model
Hamiltonian. Using Heisenberg equations of motion, this leads to a generalized
quantum Langevin equation (QLE) for the quantum system involving two quantities
which encapsulate the properties of the heat bath. Applications include: atomic
energy shifts in a blackbody radiation heat bath; solution of the problem of
runaway solutions in QED; electrical circuits (resistively shunted Josephson
barrier, microscopic tunnel junction, etc.); conductivity calculations (since
the QLE gives a natural separation between dissipative and fluctuation forces);
dissipative quantum tunneling; noise effects in gravitational wave detectors;
anomalous diffusion; strongly driven quantum systems; decoherence phenomena;
analysis of Unruh radiation and entropy for a dissipative system.Comment: Presented at the SPIE International Symposium on Fluctuations and
Noise in Photonics and Quantum Optics (Austin, May 2005
Decoherence in Quantum Systems
We discuss various definitions of decoherence and how it can be measured. We
compare and contrast decoherence in quantum systems with an infinite number of
eigenstates (such as the free particle and the oscillator) and spin systems. In
the former case, we point out the essential difference between assuming
"entanglement at all times" and entanglement with the reservoir occuring at
some initial time. We also discuss optimum calculational techniques in both
arenas.Comment: To be published in Proceedings of the 2004 IEEE NTC Quantum Device
Technology Workshop, IEEE Transactions on Nanotechnology, 4, 77, 200
Position and Spin Operators, Wigner Rotation and the Origin of Hidden Momentum Forces
Using a position operator obtained for spin 1 particles by the present author
and Wigner, we obtain a quantum relativistic result for the hidden momentum
force experienced by particles with structure. In particular, our result
applies to the hidden magnetic forces manifest in some problems of
electromagnetism. We also discuss spin and orbital angular momentum operators,
as well as Wigner rotation.Comment: Proceedings of Wigner 111 Symposium to open the Wigner Research
Institute, Budapes
Two oscillators in a common heat bath
We show that the case of two oscillators in a common heat bath cannot be
reduced to an effective one body problem. In addition, there is an interaction
between the oscillators, even at zero temperature, due to the fluctuations
caused in both oscillators by the zero-point oscillations of the
electromagnetic field
Lorentz Transformation of Blackbody Radiation
We present a simple calculation of the Lorentz transformation of the spectral
distribution of blackbody radiation at temperature T. Here we emphasize that T
is the temperature in the blackbody rest frame and does not change. We thus
avoid the confused and confusing question of how temperature transforms. We
show by explicit calculation that at zero temperature the spectral distribution
is invariant. At finite temperature we find the well known result familiar in
discussions of the the 2.7! K cosmic radiation.Comment: 6 page
A pair of oscillators interacting with a common heat bath
Here the problem considered is that of a pair of oscillators coupled to a
common heat bath. Many, if not most, discussions of a single operator coupled
to a bath have used the independent oscillator model of the bath. However, that
model has no notion of separation, so the question of phenomena when the
oscillators are near one another compared with when they are widely separated
cannot be addressed. Here the Lamb model of an oscillator attached to a
stretched string is generalized to illustrate some of these questions. The
coupled Langevin equations for a pair of oscillators attached to the string at
different points are derived and their limits for large and small separations
obtained. Finally, as an illustration of a different phenomenon, the
fluctuation force between a pair of masses attached to the string is
calculated, with closed form expressions for the force at small and large
separations
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