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Re: virtual particles preferred frame?



I'm sorry, but John's comments re "why the virtual particles don't
propagate very far" and "Because they have zero total energy. They've
got negative kinetic energy
which just cancels their rest-mass energy" strike me as a misread of
the theory of virtual particles.

Virtual particles don't go very far because they cannot exist longer
than a time interval defined by the uncertainty principle; not because
they have "imaginary momentum." E.g., creation of a virtual
electron-positron pair violates conservation of energy by an amount at
least 2mc^2 (m=electron mass=positron mass) which is a very positive
amount, but which is allowed only for a time interval delta-t =
h-bar/2mc^2. Hence, the electron or positron can move at most a
distance c*delta-t = h-bar/2mc from their point of creation; any
farther is prohibited by the uncertainty principle. "Advanced Quantum
Mechanics," Sakurai, p. 138.

Also, both the virtual electron and the virtual positron have very
positive energies (kinetic + mass). In Dirac's hole theory, the only
particles with negative energy are the electrons in the negative sea.
When a negative energy electron makes the transition to positive
energy (delta-E=2mc^2), the "hole in the sea of negative-energy states
looks like a positive-energy particle." "Advanced Quantum Mechanics,"
Sakurai, p. 132.

Glenn A. Carlson, P.E.
St. Charles County Community College
St. Peters, MO
gcarlson@mail.win.org

Subject: Re: virtual particles preferred frame?
Date: Fri, 5 Nov 1999 18:47:16 -0500
From: John Denker <jsd@MONMOUTH.COM>

At 05:03 PM 11/5/99 -0600, Glenn A. Carlson wrote:

Charge density zero? Yes. Mass density zero? No. Particles and
antiparticles have positive mass.

Right.

A spherical (isotropic) distribution of *real* particles, as observed
by one stationary with respect to the particles' center of mass, will
be contracted (anisotropic) along the direction of relative motion, as
observed by one moving with respect to the particles' center of mass.

Right.

Why would it be different for a distribution of virtual particles?

Because they have zero total energy. They've got negative kinetic
energy
which just cancels their rest-mass energy. Zero total energy in one
frame
looks exactly like zero total energy in another frame.

========

In case you're wondering whether it is nutty to have negative kinetic
energy: well, no, it's not. If you think in terms of P squared over
2 M,
then you conclude there must be imaginary momentum, which is also not
as
nutty as you might think. It explains why the virtual particles don't
propagate very far.
______________________________________________________________
copyright (C) 1999 John S. Denker jsd@monmouth.com