HDTenEightyP/NetNews huggingface dataset:
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics,sci.math
Subject: Re: Ansatz (as used in mathematical physics)
Date: 11 Jan 93 19:49:01 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Followup-To: sci.physics
Organization: SCRI, Florida State University

In article <1993Jan11.025132.18641@EE.Stanford.EDU> siegman@EE.Stanford.EDU (Anthony E. Siegman) writes:
>
>   I've seen the term Ansatz used (in English) to describe the
>mathematical structure that is set up to analyse a physics problem or
>solve a mathematical physics problem; but none of several English
>dictionaries I've check contain this term, nor do my Deutsch-English
>dictionaries give much clue to this usage.  Can anyone quote any
>authoritative references on this particular usage?

Two answers: 

1) The word is taken from a German word that is not spelled quite the 
   same way in its dictionary entry.  I know because I tried to look 
   it up once, could not find it, and my wife (who actually knows 
   something of German) showed me the root word.  The word, as far 
   as I know (and I have not looked in the new OED supplement), was 
   imported into English by German physicists who used it in a 
   colloquial or slang version.  The German word means something like 
   "the starting place", but the colloquial meaning is that it is a 
   guess at the form of the answer as a substitute for a derivation. 

2) Despite all that linquistic stuff, I always think of a bad german 
   accent saying "and zat's it" when I use the word.  It is a word 
   for a result that looks derived but has actually been logically 
   deduced from something (the ansatz) pulled out of thin air.  

I suppose you could substitute "educated guess" for "ansatz", but it 
does not carry the same meanings for me.  An ansatz is most often used 
when there is a theory that is not amenable to actual solution, such 
as QCD or the BCS theory, but where some analytical form suggested by 
the equations or physical intuition might have all the properties 
required of a solution.  It can then serve as a starting point for 
trying to make connections between theory and experiment while some of 
the actual connections between the theory and the ansatz remain vague 
(but are - hopefully - being worked on independently).  Thus it is 
more than just a parameterization used for phenomenological analysis, 
although not much more at first glance, and sometimes the word is used 
as a fancy substitute for "parameterization". 

--
J. A. Carr                                    |  "The New Frontier of which I  
jac@gw.scri.fsu.edu                           |  speak is not a set of promises
Florida State University  B-186               |  -- it is a set of challenges."
Supercomputer Computations Research Institute |   John F. Kennedy (15 July 60)
From: paul@mtnmath.UUCP (Paul Budnik)
Newsgroups: sci.physics
Subject: Re: A proof that quantum mechanics is an incomplete theory
Date: 7 Jan 93 16:56:46 GMT
Organization: Mountain Math Software, P. O. Box 2124, Saratoga. CA 95070

In article <1ig6pcINN32r@chnews.intel.com>, bhoughto@sedona.intel.com (Blair P. Houghton) writes:
> But then, so is classical mechanics.
> 
> So what's your point?
> 
Surely you jest? Of course every physical theory is incomplete in some
sense, but there is a 60 year old debate about the completeness of
quantum mechanics in the range of phenomena that it applys to. My result
makes it clear that quantum mechanics does not fully describe the
experimental results that fit in that range. There are time delays
related to the structure of the wave function itself that quantum
mechanics does not predict.

The ultimate significance lies in the powerful argument it provides against
the assumption that the wave function changes instantaneously when an
observation is made. This assumption is too vague to predict some results
that can be measured experimentally and thus is probably not simply
vague but absolutely false. If this is the case then there is an entirely
new class of experimental phenomena that is accessible through tests
of Bell's inequality. There is a space-time structure to the nonlinear
changes in the wave function that occur when an observation is made.
Understanding this structure could ultimately be as important as
quantum mechanics itself.

Paul Budnik
From: sichase@csa1.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: two point masses in an expanding universe
Date: 5 Jan 1993 12:15 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 <38145@uflorida.cis.ufl.edu>, rubio@pine.circa.ufl.edu writes...
> 
>	This is a simple question that bothers me a lot:
> 
>Imagine there are two (point) masses separated by a finite distance in an 
>expanding universe. The distance between the two masses increases and so 
>does their (relative) velocities, both of which imply that the energy of 
>one of them with respect to the other is increasing.

No.  At a given point in time in an expanding Universe, objects further
apart move faster with respect to one another.  But over time, the
relative velocity, due to the Hubble expansion, of two objects *decreases*
due to the self-gravitation of the objects in the Universe slowing 
the expansion.

Your confusion arises from a common misunderstanding of the Hubble "constant"
which, in fact, is not constant in time.  The Hubble constant is getting
smaller as time passes.  Here's why:

The initial impulse which set the Universe expanding was the Big Bang.  But
since that time, all the objects therein have been interacting according to
gravity - mutually attracting.  So the relative speeds have been slowing down. 
Even neglecting gravity, the Hubble constant would decrease.  Say we are now at
time t1.  At time t2 = 2*t1, every retreating object will be twice as far away. 
But neglecting any gravitational slowing down, they will be receeding by the
same velocity, so the Hubble constant will have half of today's measured value
at time t2.  The fact that the expansion is slowing due to gravity only makes
this effect larger. 

>Thanks for any help. Even flames will be nice (I hate it when I don't get 
>any reponses).

-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: rfeldman@theory.TC.Cornell.EDU (Bob Feldman)
Subject: Recommend high school physics text?
Keywords: text
Organization: Cornell Theory Center
Date: Fri, 8 Jan 1993 19:45:26 GMT

My son is frustrated because his high school physics textbook doesn't
explain how mathematical formulas have been derived.  Can anyone recommend
a textbook that will give clear, concise, mathematical derivations
of formulas used in high school physics?

Bob Feldman


Xref: sparky sci.physics:22438 sci.chem:5722
From: andrew@rentec.com (Andrew Mullhaupt)
Newsgroups: sci.physics,sci.chem
Subject: Re: Functional minimization with constraints
Keywords: conjugate gradient, quasi-Newton, Newton Raphson
Date: 10 Jan 93 16:14:11 GMT
Followup-To: sci.physics
Organization: Renaissance Technologies Corp., Setauket, NY.

In article <1993Jan9.010623.27893@leland.Stanford.EDU> edremy@leland.Stanford.EDU (eric remy) writes:
>Does anyone know of a good reference work for problems involving
>functional minimization with non-linear constraints? 

Check Gill Murray and Wright's _Practical Optimization_, L. E. Scales
_Linear and Nonlinear Optimization_. Both have decision charts for selecting
methods. Fancy methods are best used off the shelf rather than programming
them yourself, unless you inform yourself very carefully and have some
peculiar requirement.

For a more theoretical book, I suggest Avriel's book the title of which
escapes me at the moment.

Later,
Andrew Mullhaupt
Newsgroups: sci.physics
From: sarfatti@well.sf.ca.us (Jack Sarfatti)
Subject: re: sci.physics.research
Organization: Whole Earth 'Lectronic Link
Date: Sat, 9 Jan 1993 19:32:45 GMT


I think much of what Jack Sarfatti posts would probably be accepted.
>It at least reaches the level of being wrong rather than `not even
>wrong'. I do not think that is what you want the group to be,

In other words you only want "normal" science in Kuhn's sense. You
do not want any investigation of extending the standard models. The
only controversial thing I am suggesting is "quantum connection
communication" with the testable prediction that the polarization of
the receiver light would be sin2@cos&, @,& controlled from transmitter.
Yes this does need a minimal non-unitary evolution - but it is , as you
admit, testable by experiment. It is bad physics for you to decide
apriori that it contradicts well known principles. Unless you think that
unitarity is both necessary and sufficient for conservation of
probability - my claim is that it is sufficient and not necessary. I could
bw wrong on that. My point here is that you would deny such a discussion.

I would be in favor of two moderated conferences.

sci.physics.conventional

sci.physics.speculative

but even in speculative the claims would have to be testable, capable
of being wrong.

what about the pedagogical stuff like John Baez likes to do and like
my thread on Feynman and lately on wavelets,coherent states etc. Would
you ban that too?

maybe third conference

sci.physics.lectures

I volunteer for last two.

by the way my credentials are:

B.A. physics Cornell (1960)
M.S. physics UCSD (1967)
Ph.D. physics (1969)
thesis advisor Fred Cummings
(Gauge invariance in theory of superconductivity)
Asst. Professor of Physics (SDSU)
Honorary Research Fellow , Birkbeck College, University of London
under David Bohm
IAEA Trieste by invitation of Abdus Salam
Visiting Full Professor , Institut Mathematica, UNICAMP, Brasil
Newsgroups: sci.physics,news.groups
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: sci.physics.research: Are there important unresolved issues?
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Wed, 13 Jan 93 02:12:57 GMT

Mark Corscadden writes:

>I'll vote against this group because there is nothing in the proposed
>charter that justifies eliminating discussion of QM interpretations or
>Mach's principle.

Does that mean that you'll vote for it if we put something in the
charter that justifies eliminating discussion of QM interpretations or
Mach's principle?  (I don't think so...)  Or are you - as I am - a bit
worried about the divergence between the charter and the moderator's
public statements about what they might accept or reject?  The charter
is still just a *proposed* charter and we are debating it.  I strongly
believe that the newsgroup should be run along the lines stated in the
charter that people vote on when a vote is finally taken.  I would
LIKE to reject boringly re-hashed arguments about Mach's principle and
QM interpretations, or at least have them suitably marked so people can
easily eliminate them via killfiles.  But the former, at least, is
something I could only feel decent about doing if it is in the charter
that people have voted for!  You are gright that if the charter
says "lightly moderated," I damn well better moderate lightly.
Similarly, some moderators (including me) have expressed a desire for
about 20 posts a day to be accepted.  But if this isn't in the charter
(or at least something like "the number of posts accepted will be kept
to a reasonable level, with the most interesting posts being accepted) I
don't see how I can rightly do this.

So - fellow proposed moderators, sci.physics fans, and countryfolk, let
us debate things, perhaps modify the proposed charter, vote on the
charter, and if it passes, do what the charter says.
From: matt@physics2.berkeley.edu (Matt Austern)
Newsgroups: sci.physics,news.groups
Subject: Re: sci.physics.research: Are there important unresolved issues?
Date: 12 Jan 93 19:46:16 GMT
Reply-To: matt@physics.berkeley.edu
Organization: Lawrence Berkeley Laboratory (Theoretical Physics Group)
NNTP-Posting-Host: physics2.berkeley.edu
In-reply-to: chisnall@cosc.canterbury.ac.nz's message of Tue, 12 Jan 1993 11:40:49 GMT

In article <C0qoG2.Gnu@cantua.canterbury.ac.nz> chisnall@cosc.canterbury.ac.nz (The Technicolour Throw-up) writes:

> I have no real objection to the name sci.physics.research.  I do, however,
> have mild objections to retaining sci.physics as is.  How about renaming
> sci.physics to sci.physics.misc at the same time?  

In principle, if I were allowed unlimited powers of social
engineering, I think sci.physics.misc would be a good name for the
moderated physics newsgroup, with sci.physics.misc.d (for example) for
the unmoderated group that is now called sci.physics.

In practice, I think that there are a fair number of people who like
sci.physics as it is, and who don't want it to be altered in any way.
I think we should respect their wishes, and that we ought to just
create a new group, and not change sci.physics at all.

Some day, it will probably be necessary (due to increased traffic) to
do a complete reorganization of the physics newsgroups; when that day
comes, then maybe it will be time to talk about a new name for the
unmoderated discussion group.
--
Matthew Austern                   Just keep yelling until you attract a
(510) 644-2618                    crowd, then a constituency, a movement, a
austern@lbl.bitnet                faction, an army!  If you don't have any
matt@physics.berkeley.edu         solutions, become a part of the problem!
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: sci.physics.research: research-level only?
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Mon, 11 Jan 93 21:21:32 GMT

In article <1993Jan9.025345.1224@nuscc.nus.sg> matmcinn@nuscc.nus.sg (brett mcinnes) writes:
>baez@guitar.ucr.edu (john baez) writes:
>: 5.  GR also generates a lot of questions.  I'll give one example, from
>:     maybe a year ago: does it make any sense to ask whether the universe as
>:     a whole is rotating (Mach's principle, Newton's buckets)?
>: 
>: --
>: This is a hoary old chestnut -- precisely the sort of thing that tends to lead
>: to endless pseudophilosophical divagation -- so the basic question should be
>: in the FAQ, and fairly stringent requirements should be placed on further
>: discussion of it.                                                       
> Can you be more specific? :)   My observations suggest that a great deal
>of murky philosophising goes on inside the heads of research level
>[indeed, celebrated] physicists and that the new group is an appropriate
>place for such people seeking therapy. For example, who has not heard that
>the problem with string theory is that we don't know the analogue of the
>principle of equivalence? Here we have a case where murky philosophising
>could affect the course of entire research programmes. 

Certainly if this were 1920 I would be in favor of discussions of the
interpretation of QM on sci.physics.research, and straightening out
currently relevant murk would indeed be a laudable function for this
proposed newsgroup.  I would not like old murk to drive out the new murk
on sci.physics.research, though.

>The mere fact that
>a topic has been debated ad nauseam does not imply that professionals
>understand it. 

Indeed, but it's not clear that still more debate of hoary chestnuts is the
best use of sci.physics.research.  I am sure sci.physics will continue
to be a forum for such debate, and there is also the ever-growing FAQ.
From: paul@mtnmath.UUCP (Paul Budnik)
Newsgroups: sci.physics
Subject: Re: The instantaneous transfer of information in QM calculations
Date: 10 Jan 93 21:50:27 GMT
Organization: Mountain Math Software, P. O. Box 2124, Saratoga. CA 95070

In article <1993Jan10.164016.16419@cs.wayne.edu>, atems@igor.physics.wayne.edu (Dale Atems) writes:
> In article <481@mtnmath.UUCP> paul@mtnmath.UUCP (Paul Budnik) writes:
> >
> >The only way to reproduce the predictions of QM is to reduce the wave
> >function as a result of a detection at one site. This *instantaneously*
> >alters the singlet state wave function for both particles throughout all space
> >and transfers the information about the polarizer where the reduction was
> >assumed to occur to the distant detector. (Note I am only talking about how
> >one does the calculation. I am making no assumptions about what is `really
> >happening'.)  One then uses this `reduced wave function' at the other site
> >to compute the probability of a detection there. As long as the polarizers
> >are not changing this calculation is straight forward and produces the
> >standard quantum mechanical predictions.
> 
> What do you mean by "reproduce"?

I should have said `the only way to derive the predictions' ...

> In discussions of Bell's inequalities
> this word usually applies to hidden-variables theories making the same
> statistical predictions as QM.

What you say is unfortunately true. However Eberhard has shown that
no local theory can reproduce the predictions of quantum mechanics.
There is no need to bring in hidden variable theorys when discussing
Bell's result.

> It sounds as if you are saying that even
> within QM, you cannot predict the correlations without making use of wave
> function collapse.

This is what I am saying.

> Is there something special about the photon case here?

No.

> This is certainly not true of the spin-1/2 analog. I can do that
> calculation using only the "linear" part of QM, and the prediction is
> valid as interaction with Stern-Gerlach magnets does not affect the
> spin part of the wave function. The predicted correlations depend only
> on the singlet state wave function before detection; what happens to the
> wave function as a result of detection is not relevant.

Then you will not be able to prove Bell's inequality is violated. It is
important to understand that tests of Bell's inequality involve more than
just two detections. They also involve a knob or device for affecting those
detections. In the photon case it is a polarizer. In the case your describe
it would be some apparatus that would force the spin to be aligned along
a certain axis if a detection is made. You will only be able to prove
the expected correlations violate Bell's inequality if the measurement
or alignment of the spin of one particle influences the probability of
detection of the other. Since these two events, the alignment of the spin
of one particle and the detection of the other are space-like separated,
the only law of physics that would predict such an influence is some
version of quantum collapse.

Paul Budnik
Newsgroups: sci.physics
From: matmcinn@nuscc.nus.sg (brett mcinnes)
Subject: geodesic motion from the einstein equation
Organization: National University of Singapore
X-Newsreader: Tin 1.1 PL4
Date: Tue, 12 Jan 1993 07:26:20 GMT



Long ago I remember being told that Einstein, Infeld and Hoffman had
succeeded in deriving the geodesic equation for the motion of a free
particle from the *vacuum* Einstein equation. I seem also to recall a
rather snide remark about this work in Pais' biography, and I think I have
seen more recent references to it which apparently implied that EIH had in
fact got it wrong. Can anyone tell me the current thinking on this business?
Newsgroups: sci.physics,news.groups
From: trodrigu@spock.ecs.umass.edu (Tao R or Stephen L)
Subject: Re: sci.physics.research: Important unresolved issues!
Organization: University of Massachusetts, Amherst
Date: Tue, 12 Jan 1993 08:27:56 GMT

In order to decide if I should worry about the "not even wrong" clause,
I would be interested to know if any of the following topics are "not
even wrong", based on content as described:
 
1) A theoretical claim that time will run backward near the end of the
   life of the universe.
2) The initial 'cold fusion' announcement.
3) A claim that 'red shift' appears to be quantized, and that this calls
   into question the prominent theories about the age of the universe.
4) A claim that the energy of a vacuum should be presumed to be zero
   unless proven otherwise.
 
- Stephen Linhart

Newsgroups: sci.physics
From: daryl@oracorp.com (Daryl McCullough)
Subject: Re: hidden variables
Organization: ORA Corporation
Date: Sun, 10 Jan 1993 14:11:41 GMT

Paul Budnik writes:

>> In other words, the only way a hidden variables theory can work to
>> explain the twin pair experiment is if the orientation of a distant
>> measurement device instantaneously affects the measured properties of
>> a particle here.
>
>This argument strikes me as bordering on the perverse, not because it is
>untrue but because it implys a difference between hidden variable theories
>and quantum mechanics that does not exist. Bell's result implys that
>quantum mechanics is a nonlocal theory. The observation of at least
>one of the two particles in a test of Bell's inequality must be influenced
>by *both* measurements to reproduce the predictions of quantum mechanics
>PERIOD. Quantum mechanics implys that the observation of one particle
>is instantaneously influenced by *both* measurements even if those
>measurements are separated by billions of light years. This prediction
>of quantum mechanics is not evidence against more complete theories.
>On the contrary it is a powerful argument against the arbitrary and completely
>unjustified assumption in quantum mechanics that the wave function changes
>instantaneously when an observation is made. If this assumption
>is false, quantum mechanics *must* be an incomplete theory because there
>is an unknown space-time structure to these nonlinear changes in the
>wave function.

Paul, I agree with you (and disagree with the complacency of most
physicists such as John Baez) that Bell's Theorem should be worrisome
for quantum mechanics. However, I don't see how in the world you can
claim that quantum mechanics predicts nonlocal effects, regardless of
whether one assumes a hidden-variables completion. The form of Bell's
proof is the following:

   1. Assume a hidden-variables completion of quantum mechanics.
   2. Assume that all interactions are local (travel at light-speed
      or lower).
   3. Assume classical probability theory.
   4. Assume the probabilistic predictions of quantum mechanics are
      correct.
   5. Show that all this leads to a contradiction.

Assumption 1 is necessary (in Bell's proof, anyway) to get a
contradiction. Therefore, I don't know how you can say that quantum
mechanics is nonlocal, regardless of whether one assumes a
hidden-variables completion.

Also, I don't know how you can say that collapse of the wave function
is a necessary assumption in the derivation of the contradiction. Bell
didn't mention collapse of the wave function, he simply used the
quantum mechanical prediction for probabilities of measurements. In
the case of the EPR experiment, there is a compound measurement, where
the spin of two different particles is measured (with respect to two
different axes). Since spins of different particles are commuting
observables, the results don't depend on the order the measurements
are made. There is no need to assume collapse of the wave function
between measurements.

Daryl McCullough
ORA Corp.
Ithaca, NY

Xref: sparky sci.physics:22592 news.groups:25420 sci.misc:2014
From: jaapjl@tab00.larc.nasa.gov (J Lee Jaap)
Newsgroups: sci.physics,news.groups,sci.misc
Subject: Re: knots and stat.mech.
Followup-To: sci.physics,news.groups,sci.misc
Date: 12 Jan 1993 18:10:44 GMT
Organization: AS&M Inc
Reply-To: J Lee Jaap <J.L.Jaap@larc.nasa.gov>
NNTP-Posting-Host: cmb00.larc.nasa.gov
In-reply-to: kermits@cc.uch.gr's message of 11 Jan 93 00:28:40 GMT

In article <1993Jan11.002840.12240@csd.uch.gr> kermits@cc.uch.gr (Aggelos Keromyths) writes:

   What ?
   Aggelos

Perhaps to elaborate:  What does this have to do with news.groups?
Please be more careful in your choice of newsgroups.
--
J Lee Jaap <J.L.Jaap@LaRC.NASA.Gov> +1 804/864-2148
    employed by, not speaking for, AS&M Inc, at
         NASA LaRC, Hampton VA 23681-0001
Newsgroups: sci.physics