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From: cpf@lasspvax.UUCP (Courtenay Footman)
Newsgroups: net.physics
Subject: Re: Re: Question on FTL and quantum mechanics
Message-ID: <146@lasspvax.UUCP>
Date: Wed, 5-Dec-84 15:56:16 EST
Article-I.D.: lasspvax.146
Posted: Wed Dec  5 15:56:16 1984
Date-Received: Fri, 7-Dec-84 01:39:16 EST
References: <654@ames.UUCP> <6201@mcvax.UUCP> <274@mhuxm.UUCP> <>
Reply-To: cpf@lasspvax.UUCP (Courtenay Footman)
Distribution: net
Organization: Theory Center (Cornell University)
Lines: 37
Summary: 

In article <> gjk@talcott.UUCP (Greg J Kuperberg) writes:
>> You ought to read up on tachyons which are particles moving faster
>> than light.  They can't slow down in the same way that we can't speed
>> up to c.  There is no known evidence of tachyons.
>
>Tachyons are dead.  Some respected physicist published a paper on them
>once.  There were many replies, to the effect of, "you made a mistake in
>your physics."  The guy then said, "oops", and that was the end of it.

Tachyons are not dead.  In the latest Physics and Astronomy Clasification
System, (PRL 26 Nov), classification 14.80.Pb exists, with the following
definition:
    The Physics of Elementary Particles and Fields  (the 1)
    Properties of specific particles and resonances (the 4)    
    Others and hypothetical  (the 80)
    Others (including tachyons) (the P; the b is a check sum)

The last 4 Physics Abstracts (~two months worth) describe three papers 
with the word tachyons in the title.  This is not a very active field,
but neither is it "dead".

It is true that most practicing physicists (including me) do not believe in
tachyons and that tachyons seem to have serious diseases, most notably with
causality.

Also no evidence for tachyons has yet been found, and there is strong evidence
that charged tachyons with a "mass" less than a few times the electron mass
do not exist.  (If they did, they would strongly affect the rate of light
by light scattering;  since QED correctly predicts this rate with the
electron being the only light charged particle, other light charged particles,
including tachyons, do not exist). However, some people are still doing
research on the subject, and while I think most of them would also agree that 
tachyons probably don't exist, they would insist on the "probably".
-- 
Courtenay Footman			arpa:	cpf@lnsvax
Newman Lab. of Nuclear Studies		usenet:	cornell!lnsvax!cpf
Cornell University