HDTenEightyP/NetNews huggingface dataset:
From: carlip@landau.ucdavis.edu (Steve Carlip)
Newsgroups: sci.physics
Subject: Re: STRUCTURE OF TIME
Date: 11 Oct 92 02:35:08 GMT
Organization: Physics, UC Davis

In article <BvsBGH.AzB@well.sf.ca.us> sarfatti@well.sf.ca.us (Jack Sarfatti) writes:
>
>In Newton's classical mechanics of the 17th century F = ma and a force law
>for F gives an ordinary differential equation second order in time that can
>be solved from an initial condition by giving both initial position and
>initial speed. This is why we used to say that the least action principle
>of the calculus of variations is not teleological. However, we see that we
>were too hasty and that the nonlinearity of classical general relativity
>forces us back to teleology in that ther is no analog to the local initial
>data x(0) and dx(0)/dt. Rather we must go to nonlocal x(0) and x(1) since
>dx(0)/dt is meaningless in the general relativity case. Thus, gravitation
>demands final cause or destiny even on the classical level. 

I may be misunderstanding this.  Are you claiming that the initial-
value problem in classical general relativity is not well-posed?  This
is false --- see, for instance, chapter 7 of Hawking and Ellis, _The
Large Scale Structure of Spacetime_.  It is true that the proper
specification of the initial data is a little tricky --- instead of
the time derivative of the metric, you should give the extrinsic
curvature of the initial spacelike hypersurface, and the initial
data must satisfy a set of constraints --- but the suggestion that
you need both initial and final data is simply wrong.

I'm not sure where this misconception is coming from.  Maybe it's
this: while a set of initial conditions determines a solution of the
field equations of general relativity, there are also _other_
solutions that cannot be obtained from any choice of initial data,
because there is no initial ``space at a fixed time'' (no Cauchy
surface, for the technically inclined).  Another possibility: in a
path integral approach to _quantum_ gravity, one would compute a
transition function by specifying an initial and a final spatial
geometry, and classical interpolations would be important in a
saddlepoint approximation.  But in this, general relativity is no
different from any other field theory, except for the fact that
we don't know whether the path integral exists at all.

Steve Carlip
carlip@dirac.ucdavis.edu
Newsgroups: sci.physics,sci.math
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: OQ (Open Question) on particles
Keywords: OQ, (Elementary) particles
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Tue, 13 Oct 92 16:35:40 GMT

In article <phfrom.345@nyx.uni-konstanz.de> phfrom@nyx.uni-konstanz.de (Hartmut Frommert) writes:
>jbaez@riesz.mit.edu (John C. Baez) writes:
>>phfrom@nyx.uni-konstanz.de (Hartmut Frommert) writes:
>>>* What is a particle really ?
>
>>For quantum field theorists one common definition is: an eigenvector of
>>the mass operator (the square root of the operator energy^2 -
>>momentum^2).  
>
>If I understood right, the mass operator is usually applied to quantum
>states (Qst's) which can be only identified with "a particle" if you are
>in one-(or few-) particle theory. Then the particle(s) is (are) described
>by fields which are more or less classical with regard to 2nd quantization.
>
>The difficulty of figuring out what "a particle" is in QFT was at least 
>mentioned by Bjorken/Drell and Streater/Wightman who point out that their
>formalism is good for the large-distance limit (e.g. cross sections) but
>somewhat incomplete at short distance and "really local" considerations,
>due to Heisenberg relations, of course. So you can say that there are, say, 
>22 particles (so, what ?), in a configuration, but I still do not see what
>one (or each) of them is. 

Hmm.  My definition was only intended to allow one to say "in this
theory there are the following elementary particles: electrons and
protons" or some such thing.  As soon as one has a 2-particle state it
is no longer an eigenvalue of the mass operator (since the relative
velocities can vary continuously, essentially).  One must then mess with
cluster decompositions, which as you note are only good when the state has
spread out into essentially noninteracting clumps.  I only know the
rudiments about cluster decompositions so please don't ask about them.

>Although I regard my question still as open, thanx, John, for your in a
>certain sense enlightning discussion.

That's faint praise if I ever heard it.  :-)  Anyway, yes, if someone
hands you and QFT satisfying the Garding-Wightman axioms or Haag-Kastler
axioms you will have to work very hard to say for each state what
particles are around, and in general one shouldn't expect a very good
answer.  One of the lessons of QFT, it seems to me, is that particles
are only approximate concepts, while superselection sectors (conserved
charges) are precise and mathematically tractable.  For example, see the
spectacular work of Doplicher and Roberts (hope I got the right guys)
who showed that superselection sectors always come from a compact
symmetry group.
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Black Holes, Hawking Radiation, and Entropy
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Fri, 16 Oct 92 04:43:03 GMT

In article <MATT.92Oct15103913@physics2.berkeley.edu> matt@physics.berkeley.edu writes:
>The most general situation for a physical system, of course, isn't a
>pure quantum-mechanical state, but a mixture of states, represented by
>the density matrix.  (A pure state is represented by a density matrix
>rho where Tr(rho^2) = 1.)  You can write an equation for the time
>evolution of the density matrix, and it is straightforward to show
>that if the density matrix starts with Tr(rho^2)=1, this condition
>will persist.  In other words: pure states don't evolve into mixed
>states.

Just one quibble with this; a density matrix is a nonnegative matrix (or
linear operator) with Tr(rho) = 1.  One then uses the density matrix to
calculate the expectation value of any operator A by means of the
formula <A> = Tr(rho A).  The nonnegativity condition makes <A>
nonnegative for any nonnegative A, the Tr(rho) = 1 condition makes <1> =
1.

>So what's the solution?  I don't know.  Some people have suggested
>that quantum mechanics has to be modified in such a way so that it is
>possible for pure states to evolve into mixed states.

It's worth noting that, should it come to this, there is already a
well-worked-out formalism for doing QM where pure states can evolve to
mixed states; unitary operators are then replaced by "completely
positive" linear transformations on the space of (mixed) states.  The
basics on these appear in Takesaki's book "Theory of operator algebras
I", and I believe a more physical treatment is in Bratteli and Robinson's
"Operator algebras and quantum statistical mechanics".  These have been
used in the study of *open* systems (e.g. systems coupled to a heat
bath), in which pure states *do* turn into mixed states in normal
quantum mechanics.  Of course it would be shocking to see pure states
turn into mixed states in the quantum mechanics of closed systems like
the whole universe.

>My own feeling
>is that since we haven't even observed black holes at all, let alone
>Hawking radiation, it's a bit premature to start modifying quantum
>mechanics on the basis of how Hawking radiation works.

Agreed.
From: rabjab@golem.ucsd.edu (Jeff Bytof)
Newsgroups: sci.physics
Subject: Who is Alexander Abian and why is he doing this?
Date: Mon, 12 Oct 1992 16:47:13 GMT
Organization: ucsd
NNTP-Posting-Host: lutherlab.ucsd.edu

I hope that someone close to the scene of the crime will publicly identify
Alexander Abian and put a stop to this nonsense.  

---------------------
rabjab@golem.ucsd.edu
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: 1992 Nobel Prizes: a prediction
Date: 15 Oct 92 00:59:15 GMT
Distribution: na
Organization: Rutgers Univ., New Brunswick, N.J.


 metzler@pablo.physics.lsa.umich.edu writes:
>It has amazed me for some time now that Penzias and Wilson's accidental
>discovery of the CMBR was worthy of a Nobel Prize, but Gamow's prediction
>of a 3 K CMBR and approximately correct primordial nucleosynthesis 
>calculations -- in the absence of compelling observations to suggest 
>either -- was somehow not worthy.  Very strange.

Penzias and Wilson may have discovered it accidentally, but they
discovered it, so they got the prize.  The discovery of pennicillin
was an accident, too ... Results are what count.  Good planning and a
buck will get you a cup of coffee.

You are probably right that Gamow should have shared in the prize;
my understanding is that the committee decided to sidestep the issue
of whom to credit for the prediction (Gamow et al or the Princeton 
group, Dicke et al) by giving the prize to the experimenters only.
From: sichase@csa1.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: Time to develop a crackpot index?
Date: 15 Oct 1992 12:44 PST
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: world
NNTP-Posting-Host: 128.3.254.196
News-Software: VAX/VMS VNEWS 1.41    

In article <1992Oct15.181831.13283@asl.dl.nec.com>, terry@aslws01.asl.dl.nec.com (Terry Bollinger) writes...
>I can't resist:
> 
>1) 1 point for every statement that is widely agreed on to be false.
> 
>   The statement you are now reading is clearly false.
> 
>My score, please?  }=-)>

I am tempted to give you a 5, for making a mockery of the crackpot index.
But that doesn't seem sporting, and besides, it's not in the rules.

However, I will say that you have the wierdest mutant smiley I have yet seen.
I don't know how many points that is worth.

BTW, there is a new sci.astro crackpot, who is now claiming to have discovered
that all of geology is wrong and the earthquakes are an electromagnetic 
process induced by the Sun and Moon.  He even capitalizes every third word.
He is, of course, prosecuted for his beliefs by closed minded scientists
who are hiding the truth to protect their careers.

I am beginning to think that there is a good sociology or psychology 
thesis in this for someone who can identify the etiology of this syndrome.

-Scott
--------------------
Scott I. Chase			"It is not a simple life to be a single cell,
SICHASE@CSA2.LBL.GOV		 although I have no right to say so, having
				 been a single cell so long ago myself that I 
				 have no memory at all of that stage of my 
				 life." - Lewis Thomas
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: The quantum mechanics of closed systems
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Tue, 13 Oct 92 16:54:32 GMT

People in the interpretation of quantum mechanics may want to check
out the following paper, available electronically from gr-qc.  

Paper: gr-qc/9210006
From: James Hartle <hartle@cosmic.physics.ucsb.edu>
Date: Mon, 12 Oct 92 17:53:23 -0700

The Quantum Mechanics of Closed Systems, James B. Hartle, 31 pages,
UCSBTH-92-16.
\\
A pedagogical introduction is given to the quantum mechanics of closed systems,
most generally the universe as a whole.  Quantum mechanics aims at predicting
the probabilities of alternative coarse-grained time histories of a closed
system.  Not every set of alternative coarse-grained histories that can be
described may be consistently assigned probabilities because of quantum
mechanical interference between individual histories of the set.
In the quantum mechanics of closed systems, containing both observer and
observed, probabilities are assigned to those sets of alternative histories for
which there is negligible interference between individual histories
as a consequence of the system's initial condition and dynamics.
Such sets of histories are said to decohere. Typical mechanisms of
decoherence that are widespread in our universe are illustrated.
Copenhagen quantum mechanics is an approximation to the more general
quantum framework of closed subsystems.  It is appropriate when there is
an approximately isolated subsystem that is a participant in a
measurement situation in which (among other things) the decoherence of
alternative registrations of the apparatus can be idealized as exact.
Since the quantum mechanics of closed systems does not posit the
existence of the quasiclassical domain of everyday experience, the
domain of the approximate aplicability of classical physics must be
explained.  We describe how a quasiclassical domain described by
averages of densities of approximately conserved quantities could be an
emergent feature of an initial condition of the universe that implies
the approximate classical behavior of spacetime on accessible scales.
From: aw3@ukc.ac.uk (A.Wilson)
Newsgroups: sci.physics
Subject: Re: 1992 Nobel Prizes: a prediction
Date: 16 Oct 92 08:40:09 GMT
Reply-To: aw3@ukc.ac.uk (Alan Wilson)
Organization: Chemical Laboratory, University of Kent at Canterbury, CT2 7NH, UK

In article <93071@netnews.upenn.edu> weemba@sagi.wistar.upenn.edu (Matthew P Wiener) writes:
>In article <9OCT199221030655@utahep.uta.edu>, sawyer@utahep (Lee Sawyer) writes:
>>other is not de Broglie (the work that he was cited for was
>>in his dissertation - a unique occurance as well, I believe).
>
>Didn't Glaser invent the bubble chamber as a grad student?
>-- 
>-Matthew P Wiener (weemba@sagi.wistar.upenn.edu)

And I'm fairly sure that Josephson developed the theory behind his
junction in his Ph.D. thesis...

Alan

--
Dr. Alan Wilson        (Approved by Morrissey, the consumer monkey)

" That was MY idea "
=================================================================
From: columbus@strident.think.com (Michael Weiss)
Newsgroups: sci.physics
Subject: Re: Religion & Physics Don't Mix (?)
Date: 16 Oct 92 13:15:50
Organization: Thinking Machines Corporation, Cambridge MA, USA
	<1992Oct15.141620.11197@asl.dl.nec.com>
NNTP-Posting-Host: strident.think.com
In-reply-to: terry@aslws01.asl.dl.nec.com's message of Thu, 15 Oct 1992 14:16:20 GMT

In article <1992Oct15.141620.11197@asl.dl.nec.com>
terry@aslws01.asl.dl.nec.com (Terry Bollinger) writes: 

   If I recall the mathematician correctly, I believe it was Lagrange who
   was so intrigued by his own results that he used them as an argument
   for the existence of God.

This an old myth about Euler.  The story goes that Diderot was spreading
atheism at the court of Queen Christiana of Sweden, delighting the
sophisticates but irritating the conservatives.  The Queen needed some way
to squelch her famous guest without creating an international incident.
Euler agreed to cooperate.  It was announced that Euler would present an
algebraical proof of the existence of God.  At court, with Diderot in
attendence, Euler arose and proclaimed (in TeX, naturally):

	Monsieur, $(a+b^n)/n = x$, donc le Dieu existe; respond, s'il vous
	plait! 

(Probably I got the french wrong.)  Diderot, ignorant of mathematics, had
no choice but to withdraw in embarrassment.

I have read that this story has about as much truth to it as George
Washington's chopping down the cherry tree.  In particular, Diderot was
apparently quite knowledgeable mathematically.
Newsgroups: sci.physics
From: snyder@henry.ece.cmu.edu (John Snyder)
Subject: Re: lemon-radio
Organization: Physics Department, Carnegie Mellon University
Date: Fri, 9 Oct 1992 05:47:57 GMT

In article <Oct.8.22.10.06.1992.1294@ruhets.rutgers.edu> bweiner@ruhets.rutgers.edu (Benjamin Weiner) writes:
>Bronis Vidugiris writes:
>:I don't think you'd need a battery at all, what you need for an AM
>:radio is a tuned circuit, a rectifier of some kind (which is where I
>:suspect the lemon could come in, assuming this is more than an Urban
>:Legend), and a high (preferably) impedance earphone.  [I'd bet that the
>:earphone  *was* an extra part, just not mentioned as being part of the
>:radio.]
>
>:However, you'd only detect strong signals this way - strong enough to
>:forward bias the rectifier.  (Germanium or some other sort with a low
>:forward voltage would be preferred, as opposed to silicon diodes which take
>:significantly more forward bias to 'turn on')  Old 'crystal' sets used a
>:cats-whisker on a crystal to form the rectifier, for example)
>
>This is right, (tho' I dunno about the lemon), for a demonstration in
>a general lab I once put together an AM radio out of:
>
>- about 50 feet of wire, stretched-out (one end floating!)
>- one of those tunable inductors
>- a capacitor
>- a germanium diode
>
>I think I cheated and used an amplifier to drive the speaker, because
>you don't get much power out of it!  And the reception was terrible
>... I could only get one or two stations.
>
>The rectifier is there to get rid of the carrier frequency, BTW.
>It should be obvious why this only works for AM and not FM (given what
>the initials stand for)


When I was a kid (1960's) I built a crystal set radio out of a kit.
It consisted of nothing but an antenna, a coil that I wound myself,
a germanium diode, a variable capacitor, and an earphone.  I could
only get 2 stations reliably (I was about 40 miles from Philadelphia,
and could get KYW Philadelphia over about 1/2 of the dial.  There
were other stations nearby for which reception depended on the weather.
Now and then, I could get AM stations over considerable distances (one near 
Buffalo, NY for one).

Another interesting effect was the short wave reception.  This was sporadic,
but for the right conditions, I heard Voice of America, the Armed Forces
News Burea, and my brother heard english-language broadcasts from
Russia.  (There were others that I forget now.)  For all the short-wave
receptions, there was some kind of "beat" phenomena in the volume.
It would slowly get louder and louder, then softer and softer, untill
briefly fading out, then repeat.  The timescale of one cycle was
(if I remember correctly), about 10 to 15 seconds or so, and it
was only so soft that you could not hear it for a second or 2.
Does anyone out there know what effect could cause this unusual
shortwave reception?  (Our antenna was strung almost the whole
length of our parents' attic, which would have been about 40 feet or
so of wire, which, I understand, is close to the length required
for one of the short-wave bands.

John
snyder@henry.ece.cmu.edu
From: quest@iowegia.uucp (Steve J. Quest)
Newsgroups: sci.physics
Subject: Re: lemon-radio
Date: 10 Oct 92 18:48:08 GMT
Organization: Iowegia Public Access Usenet/UUCP, Clive IA USA.

bhv@areaplg2.corp.mot.com (Bronis Vidugiris) writes:

> However, at sufficiently high power levels (I lived *really* close to
> an AM radio station as a kid), you can get strange effects.  Our
> neighbors used to get the local AM station in their bathroom, sans
> receiver!  (I *think* I heard this effect for myself, not 100% positive
> anymore, though.)  I've heard stories (not sure if these are true) that
> people have also occasionally gotten AM reception through fillings in their
> teeth!
> 


Bronis,

        Yes, you are correct.  If one takes a couple of pieces of 
iron, and holds them so that they barely touch (while standing 
lets say a few hundred yards or less from a 50,000 watt AM 
transmission tower) you get to hear the audio representations as 
the magnetic attractions and repulsions "buzz" the metal pieces 
together.  Same goes with fillings I would imagine, tho I have not 
experienced this.  The buzzing wrench trick was demonstrated to me 
however.

sq
From: sichase@csa1.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: Over the hill at 40?
Date: 9 Oct 1992 10:07 PST
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: world
NNTP-Posting-Host: 128.3.254.196
News-Software: VAX/VMS VNEWS 1.41    

In article <1992Oct9.094759.25778@nuscc.nus.sg>, matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)) writes...
>Some time ago I received a letter from the son of an old friend, seeking
>advice as to whether he should endeavour to become a [theoretical]
>physicist. He has just completed a BS in a respectable US university.
>Among other penetrating remarks, he observes: " I noticed that
>relatively few of the profs over the age of 40 were active in research,
>even though they obviously knew their stuff. Why is that? What do I do
>if I find myself in that situation?"

I don't know what university this guy is from, but I can tell you from 
experience that it's just not true at either of the schools which I know
well, MIT and Berkeley.  I think that it's mostly a myth that people start
sitting on their hands when they start getting to middle age.  

One possible reason for this perception is that older scientists may 
not be as visable to the public.  The average scientist follows a career
path which makes him very visible, giving lots of talks, hosting conferences,
sitting on committees, etc., just around the time for a tenure decision.   
After that, many people cut back heavily on their public commitments, in 
order to spend more time on their work.  

-Scott
--------------------
Scott I. Chase			"The question seems to be of such a character
SICHASE@CSA2.LBL.GOV		that if I should come to life after my death
				and some mathematician were to tell me that it
				had been definitely settled, I think I would
				immediately drop dead again."      - Vandiver
Newsgroups: sci.physics
From: hsue@ellis.uchicago.edu (marc jacobson)
Subject: Looking for Doctor Strayer
Reply-To: hsue@midway.uchicago.edu
Organization: none to speak of
Distribution: usa
Date: Sun, 11 Oct 1992 18:08:05 GMT

Hi,

I would like to contact: 

 Mike R. Strayer
 SeCtion Head, Theoretical Physics
 Oak Ridge National Laboratory


If you know his email address, woulld you please forward the address to me
or to let him know I want to contact him.

Thanks.


Newsgroups: sci.physics
From: sarfatti@well.sf.ca.us (Jack Sarfatti)
Subject: FEYNMAN 5
Organization: Whole Earth 'Lectronic Link
Date: Wed, 14 Oct 1992 02:08:44 GMT


Feynman 5
Feynman on quantum reality:
"It has not yet become obvious to me that there's no real problem. I cannot
define the real problem, therefore I suspect there's no real problem, but
I'm not sure there's no real problem." p.13 GENIUS by Gleick

I say there is a real problem. The real problem is the issue of the
existence of objectively measurable quantum action at a distance.  The Bohm
picture of the "quantum potential" has real quantum action different from
the ordinary forces which it supplements.

My gedankenexperiment brings the real problem into sharp focus. The
consensus that I go against is that unitarity prevents communication on the
quantum connection in standard quantum mechanics. I say that unitarity is
no barrier to connection communication when full advantage is taken of the
superposition principle in the total experimental arrangement.

If I am right on the specific prediction of communication on the connection
it solves the "real problem" showing that the traditional idea of causality
(i.e., that causes are always before their effects in all frames of
reference) is false.  The downfall of causality opens new explanations for
the the creation of the universe and our role in it.
From: terry@aslws01.asl.dl.nec.com (Terry Bollinger)
Newsgroups: sci.physics
Subject: Re: Time to develop a crackpot index?
Date: 15 Oct 92 21:02:23 GMT
Organization: NEC America, Inc Irving TX

And again I succumb:

4) 30 points for each posting that claims a revolutionary theory but
   gives no concrete testable predictions.

   I'll have you know that immediately after reading this rule I went out
   and bought 50 pounds of high quality cement and mixed it in with 5000
   copies of my favorite theory that I extracted from multiple posts in
   sci.physics theory, "How The Aliens of Alpha Centari Are Controlling
   Our Brains via FTL Bell Correlations." The mix set up solid as a rock,
   so this particular theory has *clearly* met your criterion for concrete
   testability...  :)