Date: 14 January 1983 06:05-EST
From: Richard Pavelle <RP @ MIT-MC>
Subject:  GR10
To: INFO-TENSOR @ MIT-MC

Many of you on this list do not work in relativity but if
some of your colleagues have used MACSYMA for relativity
applications please forward the following to them:

Lars Hornfeldt and his colleagues at Stockholm would like
to get together a list of papers for the 10th International
Conference on General Relativity and Gravitation this July
in Padova. The papers are to be those which have used MACSYMA
for General Relativity and I am trying to collect them for
Hornfeldt. If you have published any, or if you have any in 
preprint form, send them or the references to me. 

Thanks.

Date: 20 November 1982 16:44-EST
From: Richard Pavelle <RP at MIT-MC>
Subject: RATRIEMAN
To: INFO-TENSOR at MIT-MC

At ASB's suggestion, for consistency, I have changed RATRIEMAN to RATRIEMANN 
in CTENSR. 

Date: 2 July 1982 13:58-EDT
From: Richard Pavelle <RP at MIT-MC>
To: INFO-TENSOR at MIT-MC
cc: RP at MIT-MC

I have revised the tensor manual, TM-167 (June 1980), to reflect
some changes and additions to the CTENSR and ITENSR packages. If
you wish to receive a copy let me know.

Date: 11 March 1982 16:37-EST
From: Richard Pavelle <RP at MIT-MC>
Subject: change to ITENSR
To: INFO-TENSOR at MIT-MC

The RIEMANN function in ITENSR, which represents the standard Riemann 
4 index curvature tensor, has been renamed to CURVATURE to stop the 
conflict with the RIEMANN function in CTENSR. 

Date: 9 March 1982 14:38-EST
From: Richard Pavelle <TENSOR at MIT-MC>
Subject: TRANSFORM in CTENSR
To: INFO-TENSOR at MIT-MC
cc: JPG at MIT-MC, ELLEN at MIT-MC, RJF at MIT-MC, RP at MIT-MC,
    ELL at MIT-MC

The TRANSFORM function in CTENSR has been renamed to TTRANSFORM.

Date: 1 March 1982 08:38-EST
From: Richard Pavelle <TENSOR at MIT-MC>
To: INFO-TENSOR at MIT-MC

ITENSR is now fixed.  Thanks JPG.

Date: 19 February 1982 07:26-EST
From: Richard Pavelle <TENSOR at MIT-MC>
To: INFO-TENSOR at MIT-MC

Do not use ITENSR until further notice. It is broken!

Date: 14 January 1982 16:03-EST
From: Anthony D. Kennedy <ADK at MIT-MC>
Subject: Dirac Algebra.
To: HEP at MIT-MC, INFO-TENSOR at MIT-MC, WEC at MIT-MC,
    MACSYM at MIT-MC

	I am considering implementing a new Dirac gamma-matrix
algorithm in Macsyma.  The algorithm is much faster than the
previously used brute-force methods for arbitrary n-dimensional
calculations, and is quite possibly faster than tricks like the 
Kahane algorithm in four dimensions.  I would like to know all
your comments, suggestions, and uses (past, present, or future)
for such a program, as well as your preferences for input/output
formats and syntax.  Now is the chance to make your prejudices known!
		- Tony Kennedy (ADK@MIT-MC)
[Apologies for multiple copies due to overlapping mailing-lists]


Date: 30 May 1981 12:35-EDT
From: Lars S. Hornfeldt <LSH at MIT-MC>
Sender: LSH0 at MIT-MC
Subject: TRIGSUM accepts all trigfunctions
To: INFO-MACSYM at MIT-MC, INFO-TENSOR at MIT-MC


-at input, i.e. also tan, cot, sec and csc, and converts them
to sin and cos, so that all equivalent formulations of the
relation   sin^2 + cos^2 = 1    are exploited fully
     (decreasing the number of terms).
Then it also COMBINES BACK the sin- and cos-es into the most
advantageous combination of the other functions (not offered
by earlier methods as I know).  If nothing better, at least
neg. powers of sin or cos are replaced with csc and sec.
   Both conversions are integrated in an excisting one, costing
negligible extra time.  Please send +/-  -experiences and bugs to me.
-lsh

Date: 25 JAN 1981 1017-EST
From: RP at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC

I wish to remind users of the tensor packages that if you have written
any code which you feel should/could be added to the existing code then
please let me know. This is the best way to expand the capabilities!

Date: 16 DEC 1980 2010-EST
From: LSH at MIT-MC (Lars S. Hornfeldt)
Subject: Human-like new TRIG-SIMPLIFIER and SUMSUBSTITUTOR
To: INFO-MACSYM at MIT-MC, INFO-TENSOR at MIT-MC, HEP at MIT-MC


TRIGSUM(exp);  is a new function (autoloading) that exploits the
TRIG-onometric SUM-relation:     2         2
                              sin (x) + cos (x) - 1  ==> 0

in an optimal fashion; ie it uses DIFFERENT formulations:
   2      2                   2        2             2        2
sin  + cos  ==> 1,     1 - sin  ==> cos ,     1 - cos  ==> sin

selectively only where they are BENEFICIAL, and the program returns
THAT mixture of sin and cos that constitutes the least number of terms.
For instance, TRIGSUM on the 6-term-expression:

  (ONE - C     )*SIN(X)^2 \  Returns 3 terms: /    (      S)*SIN(X)^2
+ (ONE      - S)*COS(X)^2  >      ===>       <   + (    C  )*COS(X)^2
+ (    + C  + S)          /                   \  + (ONE    )

This works equally well and fast if multiplied with any sin-cos power.

TRIGSUM uses the sum-substitutor (=1yr work) in STENSR. For references
and pointers see SHARE;STENSR USAGE.  Any arb.-length-sum of arb.-length-
products of tensors can be substituted, and in PRINCIPLE also of scalars.
Send bugs, and such sum-relations that you want to exploit, to me.

Being a complicated program, it's not small, but you can ALWAYS type
TRIGSUM(..);  since it tests space to fit the program before it autoloads.
Also the workspace consumption =0, in contrast to explicit subst. sin=>cos.

Do   :PRINT LSH;TRGSUM DEMOUT    to see a demo writefile, or run the demo
itself by  DEMO(TRGSUM,DEMO,DSK,LSH)$   which takes 5 cpu-min to end
[but (a curiosum): substituting sin=>cos would give results requiring
an Earthsized machine to store, and would take 10^7 Universe-lifetimes].

-lsh

Date:  5 NOV 1980 0833-EST
From: LSH at MIT-MC (Lars S. Hornfeldt)
Subject: STENSR's humanoid trig simplifier
To: MACSYMA-I at MIT-MC, ELL at MIT-MC, STOUTE at MIT-MC
CC: INFO-TENSOR at MIT-MC, MRM at MIT-MC, JPFF at MIT-MC

TRIGSUM(exp);   is a new function that exploits the trig sum-relation:
			     2         2
                          sin (x) + cos (x) -1  => 0

simultaneously in all formulations: sin+cos->1,  1-sin->cos,  1-cos->sin.
Each direction is selectively used only where it is BENEFICIAL, and
the program returns THAT mixture of sin and cos that constitutes the
least number of terms.		For instance:

TRIGSUM of: (ONE - C     )*SIN(X)^2   Returns     (      S)*SIN(X)^2
          + (ONE      - S)*COS(X)^2     ===>    + (    C  )*COS(X)^2
          + (    + C  + S)                      + (ONE    )

This works equally well and fast if multiplied with any sin-cos power.
The workspace consumption =0, in contrast to explicit subst. sin=>cos.
See the output file  LSH;TRGSUM DEMOUT   -which is a writefile
of  the batch		 TRGSUM,DEMO

TRIGSUM calls the arbitrary-sum-substitutor (=1yr work) in STENSR (6y).
An attempt to explain it's main lines is in TRGSUM MAIL
(complementing Springer Verlag.. see lsh;STENSR INFO)

I've the last two months [besides beating RP's Sci. Am-problem on 4
machines] made long planned improvements of the sumsubstitutor as to:

1) Substitute COLLAPSABLE sums, ie sums for which the number of, and
   sequence of, the terms may change in certain malign environments.
   Eg. the cyclic sum of 3 Riemann tensors (=identically zero) can
   collapse to 2 or less terms if contracted with symmetric tensors.

2) allow a user-provided, optional ELECTION-function, that determines
   what terms to get rid of when that choice is extra tricky. A such
   one is built into TRIGSUM, doing the choice between the terms
   associated with  "sin", "cos" and "-1".

Let me know if you can repeat any demo example with trigsimp,ratsubst
,exponentialize..
			-lsh

Date:  5 OCT 1980 2226-EDT
From: RP at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC
CC: GJC at MIT-MC


There is now a new version of CTENSR called TENSOR;CTENSR FASL. 
It is translated and compiled and it runs several times as fast 
as the old version while providing more work space for the user. 

I would like users to test it and let me know if there are any 
problems. CTENSR FASL may be loaded by calling TSETUP() in MACYSMA
or loading the file directly.

Thanks go to GJC for creating the new version.

Date: 28 SEP 1980 1446-EDT
From: TENSOR at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC
CC: GJC at MIT-MC

There is now a new version of CTENSR called TENSOR;CTENSR NFASL. 
It runs about twice as fast as the old version, CTENSR FASL, 
but may leave less work space for the user. This may not, however, 
be apparant for standard problems. 

I am asking users to test the new version and let me know how it
runs. If there are no core problems I will let this become the working
version with the fassave as the backup version. However, for the
present the old version will still be loaded by calling TSETUP()
in MACYSMA.

Thanks go to GJC for creating CTENSR NFASL.


Date: 21 SEP 1980 1115-EDT
From: RP at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC

Plans are being made to extend CTENSR to include interaction with LSH's
STENSR package. This will mean that a user in CTENSR may decide that
a 5dimensional array such as the covariant derivative of the Riemann
tensor is needed or perhaps a scalar constructed from the Riemann
tensor and its dual- whatever.  A new function in CTENSR will interact
with STENSR to allow construction of a large number of geometrical
objects.

We need some input and hence this note. We must have some idea
of the kinds of objects you may be interested in so we can build
a decent input function in CTENSR. Therefore, if you have some ideas
of the kinds of objects you may want to construct send mail to TENSOR@MC.


Date:  7 AUG 1980 1351-EDT
From: TENSOR at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC

The new tensor manual has been reproduced as an LCS document. If you
wish to have a copy for your very own then send me a note. If your
inquir listing does not give your address then send that as well.
Send requests to TENSOR@MC

Date: 10 JUL 1980 0746-EDT
From: RP at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC

John Fitch, Michael Rothstein and I are writing an article on Computer 
Algebra for Scientific American.  I am soliciting ideas about specific 
items of interest we might include.

The proposal to Scientific American suggested the following topics:
1) a historical introduction to algebraic manipulation
2) a description of algorithm implementation and capabilities
3) the various programming languages and their advantages to specific 
   systems
4) a description of some specific problems which have been solved. This
   would include some of the big problems which had been done by hand 
   and have now been checked by computer with comments on the accuracy of 
   scientists of that day.
5) the future of the field and comments on problems which may be solved 
   (in the physical sciences for example).

The article must, of course, be directed to the educated layman. In addition,
no equations may appear in the text but we can put them in separate boxes.

Bearing in mind that the 5 topics above are not cast in stone, but there
are the two constraints, I would appreciate any suggestions and/or 
comments.  Please reply to RP@MC. Thanks.

P.S. Please excuse the multiple copies some of you may receive because
of my choice of mailing lists.

Date: 16 FEB 1980 1631-EST
From: TENSOR at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC

The new tensor packages are operational. The ETENSR pack is now called
CTENSR and is available by doing

LOADFILE(CTENSR,FASL,SHARE); for component tensor manipulation.

The ITENSR pack, as before, is loaded by doing

LOADFILE(ITENSR,FASL,SHARE); for indicial tensor manipulation.

Both packages have many new  functions as well  as old ones which have
been modified. A full description is available by printing

SHARE;TENSOR DESCR.

In addition,  demos  exist  on the TENSOR  directory  under  the first
filenames CTENSR and ITENSR. Send bugs or comments to RP or TENSOR.

Date: 16 DEC 1979 0822-EST
From: TENSOR at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC


The new  tensor code will  be released shortly.  There has been  a great
deal of revision to ITENSR and ETENSR. During the next few weeks, before
the programs are released, it would be helpful if some of you  would try
the code and examine an early  draft of the manual which is on  the file
TENSOR;MANUAL  DOCUME.  If  anyone does  not  have  a  hardcopy terminal
available I  can send a  copy. Recall there  are also demo  files called
TENSOR;ETENSR DEMO(1,2,...) and  ITENSR DEMO(1,2,...). Send  comments to
RP or TENSOR.


Date: 5 AUG 1979 1345-EDT
From: RP at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC

During the next months, before a new manual appears, there will appear
on the tensor directory a sequence of batch files. These will give
some problems which have been solved using the new tensor packges and
should give the user some understanding of the new features which have
been implemented by MIKE and me. The names of the files will be
ITENSR DEMO1, ITENSR DEMO2,....    and
ETENSR DEMO1, ETENSR DEMO2,....
Send comments or bugs to RP@MIT-MC.

Date: 15 JUN 1979 1636-EDT
From: RP at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC

		ATTENTION TENSOR USERS

It is important that I know the kind of problems which users have for
which they hope ITENSR can help.  In particular I wish to know about
problems which involve symmetries.  As you know ITENSR does not yet
manipulate indexed objects which are skew- symmetric.  If you can tell
me what you would like perhaps it will happen this summer. Be specific!
Send mail to me or TENSOR.

Date: 7 JUN 1979 1344-EDT
From: MIKE at MIT-MC (Michael Wester)
To: INFO-TENSOR at MIT-MC

Does anyone use the so-called "special metric file" (TENSOR;METRIC FILE)
in ETENSR?
    
Date: 4 JUN 1979 1345-EDT
From: RP at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC

ETENSR is being modified at this time.  I will let you know the changes
which are being made at a later date.  It is now a good time to send 
suggestions for changes to me.
   
Date: 5 MAY 1979 0815-EDT
From: TENSOR at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC

Has anyone ever found an example where the CANTEN function was
useful. There is a bug in it now but we will have to decide whether
it should be kept. 

Date: 30 APR 1979 2008-EDT
From: TENSOR at MIT-MC (Richard Pavelle)
To: INFO-TENSOR at MIT-MC

This is RP.  Sorry about the last message which was inadvertently sent.
INFO-TENSOR is now back up and each of you who receives this is on the
mailing list.  If you wish to communicate with everyone on the mailing
list simply send mail to INFO-TENSOR.  If you wish your name removed or
wish another name added let me know.  The following is the list at the
moment.

(ASB) (DAVEK) (RP) (AMENT) (STAN) (TENSOR) (ADK) (ZIM) (YEKTA) 
(SWOLF) (CMA) (JPLHDW) (JPLFBE) (BIRREL) (FORWRD) (SHAP) (STOUTE) (JLK)

In closing, this is the final time you will see the system message which
was sent twice.  Somehow, a number of people do not like to look at msgs.


                Attention TENSOR users

There are plans to rewrite the tensor code this summer.  There are a number
of known difficulties with the ETENSR and ITENSR (or original CTMS and ITMS)
packs.  However, we would like to know who uses them and more important we
would appreciate any comments, criticisms, suggestions etc on improving 
the ETENSR AND ITENSR code. If you have developed any special purpose routines
utilizing the code let us know this as well.  Further, please criticise the 
description of these packages in the manual.  Send mail to TENSOR or 
INFO-TENSOR if you wish to share your ideas.  Work on the tensor packs
will begin in early June.
   
DISTRIB:  *CMU, *DM, *MC, *ML, *AI
EXPIRES: 04/30/79 20:29:20
RP@MIT-MC 04/15/79 20:29:20 Re: Attention TENSOR users
There are plans to rewrite the tensor code this summer.  There are a number
of known difficulties with the ETENSR and ITENSR (or original CTMS and ITMS)
packs.  However, we would like to know who uses them and more important we
would appreciate any comments, criticisms, suggestions etc on improving 
the ETENSR AND ITENSR code. If you have developed any special purpose routines
utilizing the code let us know this as well.  Further, please criticise the 
description of these packages in the manual.  Send mail to TENSOR.

