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Rotations - why are they not vectors
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Terry Padden
science forum beginner


Joined: 17 Jun 2005
Posts: 28

PostPosted: Fri Jul 21, 2006 10:14 am    Post subject: Re: Rotations - why are they not vectors Reply with quote

"Shmuel (Seymour J.) Metz" <spamtrap@library.lspace.org.invalid> wrote in
message news:44bf7072$51$fuzhry+tra$mr2ice@news.patriot.net...
..
Quote:

And what is a rotation of 180 followed by a rotation of 180?

All other axioms woukd be satisfied in this interpretation.

No. See above.


Whatever 180 deg + 180 deg is, it is NOT the Zero Vector for rotations
!!!!!!

By AXIOMATIC definition the Zero Vector is ALWAYs the algebraic sum of
opposing equal vectors

e.g. (Rotate +180 deg) + (Rotate -180deg)

PLEASE, PLEASE try to understand the question. It is about conformity with
the axioms. Not about your infantile arithmetic.

Your total misunderstanding of vectors and of rotations which are
multi-valued entities is showing. Equating any number of complete turns
with no rotation is a disgraceful trick played on innocent young minds by
stupid mathematicians. It is on a par with the rubbish that tells them that
3 x 4 = 4 x 3. Anyone who has ever moved house knows that to be rubbish;
they don't need a Ph D in non-commutative geometry to work it out. Just
proper reasoning based on relevant experience.

If you wish to make some progress start by discarding that 360 degree
rubbish. 1 turn = 1 are the only sensible units..
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mariano.suarezalvarez@gma
science forum addict


Joined: 28 Apr 2006
Posts: 58

PostPosted: Thu Jul 20, 2006 3:53 pm    Post subject: Re: Rotations - why are they not vectors Reply with quote

Terry Padden wrote:
Quote:
By assuming your definition you are unable to even consider my question. You
have already defined rotations as operators!

When you asked your original question, you gave absolutely
no indication that you were using the words "vector"
and "rotation" with a meaning different from what the
mathematical community has used them for the last hundred
years (of course, you are free to do that, and you obviously do not
need me to tell you so). I fail to see on what base you imagined
that anyone would have understood your question in your terms.

Moreover, when you realised that most people had not
telepathically picked the fact that you were using definitions
different from the usual ones, you did not provide the definitions
you are using, but called them (us, in fact) idiots and went on
to rant on the mathematical establishment and what not.

I'd appreciate that in the future you were more explicit about
the intended meaning of your words, in the situations---such as
the current one,---in which confusion is quite likely to occur.
Actually, I am quite sure this would be of the most utility to
yourself, as it would, in all likelyhood, reduce the number of
"idiots" that respond to you, so that in the end you'll get a higher
signal-to-noise ratio. For example, if you had clearly stated
that you were using "vector" and "rotation" in the (yet
unspecified) meaning you have in mind, I probably would
have not have even attempted to answer your question.

Cheers,

-- m
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William Elliot
science forum Guru


Joined: 24 Mar 2005
Posts: 1906

PostPosted: Thu Jul 20, 2006 11:30 am    Post subject: [] Rotations - why are they not vectors Reply with quote

On Thu, 20 Jul 2006, Terry Padden wrote:
Quote:
However you have been showing some signs of being able to think for yourself
so I will try to be patient with you - it's not easy but we all have to make
sacrifices - even me !

Oh pity poor pathetic down talking Terry, Padden is superfical ego

by grunting great grandious sacrifices made just for me and y'all.
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Shmuel (Seymour J.) Metz1
science forum Guru


Joined: 03 May 2005
Posts: 604

PostPosted: Thu Jul 20, 2006 11:00 am    Post subject: Re: Rotations - why are they not vectors Reply with quote

In <1153110681.231177.132530@m73g2000cwd.googlegroups.com>, on
07/16/2006
at 09:31 PM, jw12jw12jw12@yahoo.com said:

Quote:
1-D rotations ARE a vector space...this space is isomorphic to R^1.

No.

Quote:
For example, one of the axioms of a vector space is: u+v=v+u

It's not enough to satisfy one axiom, you must satisfy them all.

Quote:
and in the case of 1-D rotations a rotation of (for example) 30
degrees followed by a rotation of 40 degrees is equivalent to a
rotation of 40 degrees follwed by a rotation of 30 degrees.

And what is a rotation of 180 followed by a rotation of 180?

Quote:
All other axioms woukd be satisfied in this interpretation.

No. See above.

--
Shmuel (Seymour J.) Metz, SysProg and JOAT <http://patriot.net/~shmuel>

Unsolicited bulk E-mail subject to legal action. I reserve the
right to publicly post or ridicule any abusive E-mail. Reply to
domain Patriot dot net user shmuel+news to contact me. Do not
reply to spamtrap@library.lspace.org
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Terry Padden
science forum beginner


Joined: 17 Jun 2005
Posts: 28

PostPosted: Thu Jul 20, 2006 10:33 am    Post subject: Re: Rotations - why are they not vectors Reply with quote

"ben" <benedict.williams@gmail.com> wrote in message
news:1153300013.052124.53220@b28g2000cwb.googlegroups.com...
Quote:

I'm quite happy with my understanding of rotations, which is that they
are orientation preserving linear isometries of a vector space. If you
want to use a different definition of rotation from me, go ahead.

I think it is very likely that rotations (in your sense of the word)
form a vector space. I would be greatly pleased if you could offer a
rigorous definition of what you understand by "a rotation", as this
might allow me to say for certain.

My guess is that a rotation, for you, is a measurement along with the
implicit understanding of what this rotation might do if you applied it
to something,

Of course you are happy with the mathematical status quo. "happy as a pig
in swill" is the relevant proverb. It means you can be mentally lazy and
not think for yourself. Have you not heard of and digested "the Parable of
the talents" ?

However you have been showing some signs of being able to think for yourself
so I will try to be patient with you - it's not easy but we all have to make
sacrifices - even me !

By assuming your definition you are unable to even consider my question. You
have already defined rotations as operators! Now I am aware that the
mathematical high church dictates that rotations are operators - hence all
that matrix jazz you people blindly chant whenever an unbeliever is sighted
; but a heretic like me does not have to worry about your sacred gospel.

Think of it this way - and try not to jump your fences - take them one at a
time. In vector space theory there are (a) vectors = passive things; and
(b) operators = active things which can operate on the (a)'s. Hereabouts
you may need to use the forgetful functor whatsit so you can disregard
Einstein's credo that it is wrong to assume such an active / passive
distinction.

Then reword my question like so. We think of linear displacements as
passive = vectors (a); why can't we think of angular displacements as also
being passive i.e. as vectors ? (This is where the axioms come in). Why
are you forced to think of them as (b) ?

Remember one question at a time. It may help to free up your thought
patterns if you consider that angular displacements are only linear
displacements for rotations of infinite radius.
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Narcoleptic Insomniac
science forum Guru


Joined: 02 May 2005
Posts: 323

PostPosted: Thu Jul 20, 2006 12:27 am    Post subject: Re: Rotations - why are they not vectors Reply with quote

On Jul 19, 2006 1:15 AM CT, Timothy Golden wrote:

Quote:
Narcoleptic Insomniac wrote:
On Jul 18, 2006 9:34 PM CT, Timothy Golden wrote:

Terry Padden wrote:
Most of what you write is correct - i.e. heading
in the right direction - except for that "Pi"
stuff; but remember there are innocent
mathematicians reading this and we don't want to
frighten them. However if you attach the magic
phrase "forgetful functors" to what you have
written they will mistake you for one of their
senior wizards and let you pass without attacking
you - unlike what they try on me.

For now I am just trying to get them to think
about vectors. It is not easy. They are taught
so much rubbish it is hard for them to think
clearly. You ask them a simple, but not easy,
question about vector space axioms and they -
with one or two honourable exceptions -
automatically talk about groups, matrices, Rn,
Euclidean space, Lie Algebras, "pi", and god
knows what; any old rubbish except considering
and responding to the question ; and of course
they think they are really smart mathematicians -
god help us !

*bites tounge*

Rotation seems to be a product relationship. The
complex numbers perform geometrical rotation via
product.

Indeed they do.

Your winding concept is pretty easily expressed
in the polar coordinate system but what about for a
value a+bi? As I read around about winding number

http://www.geom.uiuc.edu/~ross/webtex/webmmlSamples/node2.html
I see that it is mostly used in the context of
paths. But should it apply to the complex plane?

Here is one way to implement winding counters in
them. So for example rather than a+bi lets just
look at just the a part.
a i i i i i = a i
would be the ordinary notation. But to implement
counting we need to add a component to the
elemental structure like:
( 0, a ) i i i i i = 1, a i
or
( 2, 1.2 )( 3, 2.0 i ) = 5, 2.4 i
and
( 0 , -i )( 0 , -i ) = 1, i .

It seems you are grasping at a way to determine what
branch you're working within after a given set of
rotations.

The question arises wether these are nondecreasing
as more products are taken, or can they unwind? I
think they are nondecreasing; they are coupled to
the handedness of the coordinate system. So the
discrete product would produce a discontinuity on
the positive real axis, where a slight change
toward -i from a slightly positive i value will
cause an abrupt change, though the usual math is
undisturbed.

Again, it seems that you're thinking about moving
from one branch to the next.

By branch do you mean the lines dividing the quadrants?

No, any complex number, like z = a + bi you were talking
about, can be represented as z = |z| * e^(it) where |z|
is the modulus (a real number) and t is the argument.
The modulus |z| is the distance from the origin and the
argument t is the angle (similar to polar coordinates).

I guess a good way to bring up "branch" here is by
elaborating on that concept you brought up earlier that
multiplication acts as a rotation.

Since i = e^(pi * i / 2) each time you multiply by i you
are rotating pi * i / 2 radians. This implies that

i^5 = e^(5 * pi * i / 2)

...but e^(it) has a period of 2pi so...

5 pi / 2 == pi / 2 (mod 2pi)

...which gives us i^5 = e^(pi * i / 2) = i.

Basically this says a rotation of 90 degress is the same
as a rotation of 360 + 90 (...but we wanted to avoid
this...)

Okay, what I'm getting at is that this periodicity of
e^(it) can be a problem when we deal with multivalued
functions (e.g. the complex log). To get rid of the
problem we define a specific "branch" to work on. This
just means that we specify a period of 2pi to work within.
For instance, the principal branch is -pi < t <= pi, see

http://mathworld.wolfram.com/PrincipalBranch.html

...for a pretty picture. So why the hell did I even bring
this all up? Because when you wrote...

Quote:
( 0, a ) i i i i i = 1, a i

...above the "1" just signified that we moved up one
branch.

Quote:
But we can take a sum of these values and get off of
the branches. The counters would generally track but
for instance
( ( 0, 3 ) + ( 0, -3 i ) )( 0, i )
= ( 0, 3i ) + ( 1, 3 )
So that independent counters are needed even though
generally a variable z could be construed to have a
singular counter. The z counter can be seen in the
polar domain as added directly to the angle. What
this implies about negative angles I'm not quite
sure. That would need some thought.

Just as positive arguments made us jump up branches,
negative arguments would make us jump down branches.

Quote:
I think that this system asks that all continuous motion
be taken in a singular angular direction. It's the only
coherent behavior. In a physics regard this could be
acceptable since the complex plane already posesses
perfect symmetry about the real axis.


From a physical point of view this may be meaningful
since handedness plays a part in physics. If an
iterative product raises the winding count should an
iterative division process bottom out? That would
imply disallowing negative winding numbers which
might be a coherent choice.

It all seems contrived but might be worth keeping an
awareness of these options.

- Tim

Hmmmmm I dunno, one guy who tried to generalize this
kind of geometry of complex numbers ended up inventing
the quaternions...

Ha,ha. I'm surprised he didn't wind up with polysigned
numbers. They are quite a different beast yet have the
same common features of real and complex numbers in
their midst. But you are suggesting that winding number
in particular could have some interesting effects. The
puzzle might be one of hunting for these things in the
physical. They are suggestive of a lattice structure,
where the winding portion is like a discrete lattice
and the continuous part is the continuum between.
That's fairly close to the traditional buildout of the
real numbers; integers then continuum. Perhaps we
should just leave it a can of worms up on the shelf
rather than open it up. Letting out all those worms
could be a lot of work to clean up.

I have yet to open the can of polysigned worms; looks
pretty interesting though.

Quote:

..and we all know how horrible that turned out to be
(their imaginary parts can describe 3-D rotation and
the whole concept leaked into groups, matrices, and
god knows what).

Another way to look at rotation is in terms of point
fixing. So in 2D upon fixing a point there is one
dimension of freedom to rotate in. Likewise in 3D upon
fixing 2 points (forming an axis) there is one degree
of freedom. Fixing one point in 3D leaves two degrees of
freedom. So in n dimensions there are n-m degrees of
freedom, where m is the number of fixed points. I
understand that is not a proof but it is easily
convincing.

This is the traditional sense of rotation instead of
allowing for a real line binary rotation (flip) and then
generalizing to scaling also. In that most general case
I think is is simply a matter of allowing scale in and
so the degree of freedom is raised by one to n-m+1. When
the scale is negative things get their handedness
flipped.

But all of this does go on in vector projection right?
so an n-dimensional system is put though an nxn matrix
multiplication and out comes a new image. If the matrix
was orthogonal and unitary (probably not the right
lingo; something about a determinant here) then the
result conserves its shape. Where is the winding in
that?

-Tim

Hooooold on a minute, now you're talking about using
matrices...

...remember, this thread isn't supposed to be about how
matrices (or virtually anything else) can describe
rotations. I immediately brought that up (along with a
few others) and was deemed a "fool" and told to get lost
until I could understand the axioms. I think I shall take
that advice and get out of here.

Regards,
Kyle Czarnecki
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Tim Golden
science forum Guru Wannabe


Joined: 12 May 2005
Posts: 176

PostPosted: Wed Jul 19, 2006 4:15 pm    Post subject: Re: Rotations - why are they not vectors Reply with quote

Narcoleptic Insomniac wrote:
Quote:
On Jul 18, 2006 9:34 PM CT, Timothy Golden wrote:

Terry Padden wrote:
Most of what you write is correct - i.e. heading in
the right direction - except for that "Pi" stuff; but
remember there are innocent mathematicians reading
this and we don't want to frighten them. However if
you attach the magic phrase "forgetful functors" to
what you have written they will mistake you for one
of their senior wizards and let you pass without
attacking you - unlike what they try on me.

For now I am just trying to get them to think about
vectors. It is not easy. They are taught so much
rubbish it is hard for them to think clearly. You ask
them a simple, but not easy, question about vector
space axioms and they - with one or two honourable
exceptions -automatically talk about groups,
matrices, Rn, Euclidean space, Lie Algebras, "pi",
and god knows what; any old rubbish except
considering and responding to the question ;
and of course they think they are really smart
mathematicians - god help us !

*bites tounge*

Rotation seems to be a product relationship. The
complex numbers perform geometrical rotation via
product.

Indeed they do.

Your winding concept is pretty easily expressed in the
polar coordinate system but what about for a value
a+bi? As I read around about winding number


http://www.geom.uiuc.edu/~ross/webtex/webmmlSamples/node2.html
I see that it is mostly used in the context of paths.
But should it apply to the complex plane?

Here is one way to implement winding counters in
them. So for example rather than a+bi lets just look at
just the a part.
a i i i i i = a i
would be the ordinary notation. But to implement
counting we need to add a component to the elemental
structure like:
( 0, a ) i i i i i = 1, a i
or
( 2, 1.2 )( 3, 2.0 i ) = 5, 2.4 i
and
( 0 , -i )( 0 , -i ) = 1, i .

It seems you are grasping at a way to determine what
branch you're working within after a given set of
rotations.

The question arises wether these are nondecreasing as
more products are taken, or can they unwind? I think
they are nondecreasing; they are coupled to the
handedness of the coordinate system. So the discrete
product would produce a discontinuity on the positive
real axis, where a slight change toward -i from a
slightly positive i value will cause an abrupt change,
though the usual math is undisturbed.

Again, it seems that you're thinking about moving from
one branch to the next.
By branch do you mean the lines dividing the quadrants?

But we can take a sum of these values and get off of the branches.
The counters would generally track but for instance
( ( 0, 3 ) + ( 0, -3 i ) )( 0, i )
= ( 0, 3i ) + ( 1, 3 )
So that independent counters are needed even though generally a
variable z could be construed to have a singular counter. The z counter
can be seen in the polar domain as added directly to the angle. What
this implies about negative angles I'm not quite sure. That would need
some thought. I think that this system asks that all continuous motion
be taken in a singular angular direction. It's the only coherent
behavior. In a physics regard this could be acceptable since the
complex plane already posesses perfect symmetry about the real axis.

Quote:

From a physical point of view this may be meaningful
since handedness plays a part in physics. If an
iterative product raises the winding count should an
iterative division process bottom out? That would imply
disallowing negative winding numbers which might be a
coherent choice.

It all seems contrived but might be worth keeping an
awareness of these options.

- Tim

Hmmmmm I dunno, one guy who tried to generalize this kind
of geometry of complex numbers ended up inventing the
quaternions...

Ha,ha. I'm surprised he didn't wind up with polysigned numbers.
They are quite a different beast yet have the same common features of
real and complex numbers in their midst.
But you are suggesting that winding number in particular could have
some interesting effects. The puzzle might be one of hunting for these
things in the physical. They are suggestive of a lattice structure,
where the winding portion is like a discrete lattice and the continuous
part is the continuum between. That's fairly close to the traditional
buildout of the real numbers; integers then continuum. Perhaps we
should just leave it a can of worms up on the shelf rather than open it
up. Letting out all those worms could be a lot of work to clean up.

Quote:

..and we all know how horrible that turned out to be
(their imaginary parts can describe 3-D rotation and the
whole concept leaked into groups, matrices, and god knows
what).

Another way to look at rotation is in terms of point fixing. So in 2D
upon fixing a point there is one dimension of freedom to rotate in.
Likewise in 3D upon fixing 2 points (forming an axis) there is one
degree of freedom. Fixing one point in 3D leaves two degrees of
freedom. So in n dimensions there are n-m degrees of freedom, where m
is the number of fixed points. I understand that is not a proof but it
is easily convincing.

This is the traditional sense of rotation instead of allowing for a
real line binary rotation (flip) and then generalizing to scaling also.
In that most general case I think is is simply a matter of allowing
scale in and so the degree of freedom is raised by one to n-m+1. When
the scale is negative things get their handedness flipped.

But all of this does go on in vector projection right? so an
n-dimensional system is put though an nxn matrix multiplication and out
comes a new image. If the matrix was orthogonal and unitary (probably
not the right lingo; something about a determinant here) then the
result conserves its shape. Where is the winding in that?

-Tim
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Tim Golden
science forum Guru Wannabe


Joined: 12 May 2005
Posts: 176

PostPosted: Wed Jul 19, 2006 12:53 pm    Post subject: Re: Rotations - why are they not vectors Reply with quote

Terry Padden wrote:
Quote:
"Timothy Golden BandTechnology.com" <tttpppggg@yahoo.com> wrote in message
news:1153276468.410161.56060@75g2000cwc.googlegroups.com...

Rotation seems to be a product relationship. The complex numbers
perform geometrical rotation via product. Your winding concept is
pretty easily expressed in the polar coordinate system but what about
for a value a+bi? As I read around about winding number
http://www.geom.uiuc.edu/~ross/webtex/webmmlSamples/node2.html
I see that it is mostly used in the context of paths. But should it
apply to the complex plane?


I would reccommend that you discard conventional notions such as complex
numbers & polar co-ordinates as mathematical impositions if you wish to
continue making progress.

Well, I am able to derive the complex numbers as P3 in the polysign
domain so I do see them as natural and as an integral part of
spacetime. The construction is starkly different from the usual
development. In effect a few polysign definitions( the identity law and
the product) generate the real numbers for n = 2 and complex numbers
for n = 3. There are higher sign systems as well and they have the same
notion of arithmetic product but the law
| A B | = | A || B |
is broken beyond P3. Still all of these systems obey the usual
associative, commutative, and distributive laws that the real and
complex numbers posess.
P1 is congruent with time and so the family can be argued to derive
spacetime as
P1 P2 P3
This argument relies upon the product being fundamentally involved in
physical processes since that is what causes the breakpoint behavior
beyond P3. At a macro scale we see rotation and planar features exist
in the physical environment. That they are exhibited by some
fundamental math as well should not be overlooked.

-Tim
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ben1
science forum beginner


Joined: 16 May 2006
Posts: 9

PostPosted: Wed Jul 19, 2006 9:44 am    Post subject: Re: Rotations - why are they not vectors Reply with quote

I said:
"A more subtle definition (the matrices are harder to write down) will
work for n-dimensions."

This is completely false. Please disregard.
Ben
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ben1
science forum beginner


Joined: 16 May 2006
Posts: 9

PostPosted: Wed Jul 19, 2006 9:06 am    Post subject: Re: Rotations - why are they not vectors Reply with quote

Terry Padden wrote:
Quote:
"ben" <benedict.williams@gmail.com> wrote in message
news:1153124461.756415.119060@s13g2000cwa.googlegroups.com...
Rotations (in Euclidean space) do not form a vector space over the
reals because of the failure of the consistency axiom. If r,s are real
numbers and T is a rotation, then it is not necessarily the case that
r(sT) = (rs) T

For instance, let T denote rotation through one quarter-circle (90
degrees or pi/2 radians). Then
4T= Id, the identity rotation
1/4 ( 4T) = Id
which is not the same as
(1/4 * 4) T = T

Ben


Now that I've had some time to digest this, I have to tell you your argument
is wrong. I have read your later comment on the Wikipedia stuff but that
is irrelevant.

Also by referring to Id's you are sneaking in non-vector stuff. The special
vector is the Zero (or Null) vector - not the Id

Also for rotations there is no rational place for values scaled by "pi". I
complete rotation has the value = 1.

Here is why your argument is wrong;

1. The Zero vector is defined as the algebraic sum of any PAIR of equal but
opposite vectors i.e. 0 = +x + -x

2. For rotations every vector is multi-valued. If something is
multi-valued it does NOT mean that all the values are equal; it means all
the values are different.

3. So - I know this may come as a great shock after all your professors
have told you, so I hope you are sitting down with a strong restorative
readily available -

One complete rotation, 1 Turn (value = 1) is NOT the same as no rotation
(value =0).

i.e. your statement that when T = 1/4 of 1 Turn, 4T = Id = 0 is incorrect.
So your argument from consistency or associavity or whatever fails.

4. Moreover after 1 complete Turn we do not have a PAIR of opposing values
so again we cannot by definition/axiom have 0, the Zero vector after 1 Turn.
Again the argument fails.

You may be aware of things called winding numbers. They are needed
precisely because of this situation; so that differences in the number of
Turns can be recognised. The differences are real; e.g. Midnight on
Wednesday is not the same as Midnight on Thursday.

So your argument - based on the axioms- fails. So we still don't now
whether rotations are vectors or not.

I'm quite happy with my understanding of rotations, which is that they
are orientation preserving linear isometries of a vector space. If you
want to use a different definition of rotation from me, go ahead.

I think it is very likely that rotations (in your sense of the word)
form a vector space. I would be greatly pleased if you could offer a
rigorous definition of what you understand by "a rotation", as this
might allow me to say for certain.

My guess is that a rotation, for you, is a measurement along with the
implicit understanding of what this rotation might do if you applied it
to something, soam guessing that your definition of rotation (again,
1-dimensional) might looks something like this:

Let f: R -> O(2) be the linear map taking t to the matrix [cos 2pi t,
-sin 2pi t; sin 2pi t, cos 2pi t]. Then a rotation is an element of R x
O(2) of the form (t, f(t)). Addition of rotations is given by
(a,f(a))+(b,f(b)) = (a+b,f(a+b)).

Under this definition, of course, rotations have all the properties you
ascribe to them, and also form a 1-dimensional vector space over the
reals.

A more subtle definition (the matrices are harder to write down) will
work for n-dimensions.

If one omits the map f, and says "a rotation is a measurement of an
angle", then one arrives at a theory of rotations that is essentially
useless, since there is no geometric content.

Ben
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Terry Padden
science forum beginner


Joined: 17 Jun 2005
Posts: 28

PostPosted: Wed Jul 19, 2006 6:35 am    Post subject: Re: Rotations - why are they not vectors Reply with quote

"Timothy Golden BandTechnology.com" <tttpppggg@yahoo.com> wrote in message
news:1153276468.410161.56060@75g2000cwc.googlegroups.com...
Quote:

Rotation seems to be a product relationship. The complex numbers
perform geometrical rotation via product. Your winding concept is
pretty easily expressed in the polar coordinate system but what about
for a value a+bi? As I read around about winding number
http://www.geom.uiuc.edu/~ross/webtex/webmmlSamples/node2.html
I see that it is mostly used in the context of paths. But should it
apply to the complex plane?


I would reccommend that you discard conventional notions such as complex
numbers & polar co-ordinates as mathematical impositions if you wish to
continue making progress.
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Narasimham G.L.
science forum Guru Wannabe


Joined: 28 Apr 2005
Posts: 216

PostPosted: Wed Jul 19, 2006 5:42 am    Post subject: Re: Rotations - why are they not vectors Reply with quote

Terry Padden wrote:
Quote:
mariano.suarezalvarez@gmail.com> wrote in message
news:1153025545.663758.95150@75g2000cwc.googlegroups.com...
Terry Padden wrote:
I am bothered by the mathematics of rotations. It is I believe
mathematically acceptable for any physical reality to be defined on an
abstract axiomatic basis. Then anything that fulfills a given defining set
of axioms for a type of mathematical object is a mathematically valid
example of the defined mathematical object.

A set does not make a vector space.

You B***** Fool. Who mentioned sets !!
.......

The obvious ones you moron. You can ADD rotations; and you can SCALE
rotations by a suitable Field. Idiot !!

Yes you fool - but that is in 1-D ; and I wrote do-not-commute in 2-D.
Can't you even read a simple sentence ???

You may want to review Halmos' presentation of what a vector space
is, if you think that commutativity is irrelevant, by the way...

NO ! I want you to go AWAY !!!!!!

Your courtesy and manners seem to have undergone disorientation
somewhere along the line.It is never too late to rotate it backwards to
let others join in your quests in better harmony.
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Narcoleptic Insomniac
science forum Guru


Joined: 02 May 2005
Posts: 323

PostPosted: Wed Jul 19, 2006 3:26 am    Post subject: Re: Rotations - why are they not vectors Reply with quote

On Jul 18, 2006 9:34 PM CT, Timothy Golden wrote:

Quote:
Terry Padden wrote:
Most of what you write is correct - i.e. heading in
the right direction - except for that "Pi" stuff; but
remember there are innocent mathematicians reading
this and we don't want to frighten them. However if
you attach the magic phrase "forgetful functors" to
what you have written they will mistake you for one
of their senior wizards and let you pass without
attacking you - unlike what they try on me.

For now I am just trying to get them to think about
vectors. It is not easy. They are taught so much
rubbish it is hard for them to think clearly. You ask
them a simple, but not easy, question about vector
space axioms and they - with one or two honourable
exceptions -automatically talk about groups,
matrices, Rn, Euclidean space, Lie Algebras, "pi",
and god knows what; any old rubbish except
considering and responding to the question ;
and of course they think they are really smart
mathematicians - god help us !

*bites tounge*

Quote:
Rotation seems to be a product relationship. The
complex numbers perform geometrical rotation via
product.

Indeed they do.

Quote:
Your winding concept is pretty easily expressed in the
polar coordinate system but what about for a value
a+bi? As I read around about winding number


http://www.geom.uiuc.edu/~ross/webtex/webmmlSamples/node2.html
I see that it is mostly used in the context of paths.
But should it apply to the complex plane?

Here is one way to implement winding counters in
them. So for example rather than a+bi lets just look at
just the a part.
a i i i i i = a i
would be the ordinary notation. But to implement
counting we need to add a component to the elemental
structure like:
( 0, a ) i i i i i = 1, a i
or
( 2, 1.2 )( 3, 2.0 i ) = 5, 2.4 i
and
( 0 , -i )( 0 , -i ) = 1, i .

It seems you are grasping at a way to determine what
branch you're working within after a given set of
rotations.

Quote:
The question arises wether these are nondecreasing as
more products are taken, or can they unwind? I think
they are nondecreasing; they are coupled to the
handedness of the coordinate system. So the discrete
product would produce a discontinuity on the positive
real axis, where a slight change toward -i from a
slightly positive i value will cause an abrupt change,
though the usual math is undisturbed.

Again, it seems that you're thinking about moving from
one branch to the next.

Quote:
From a physical point of view this may be meaningful
since handedness plays a part in physics. If an
iterative product raises the winding count should an
iterative division process bottom out? That would imply
disallowing negative winding numbers which might be a
coherent choice.

It all seems contrived but might be worth keeping an
awareness of these options.

- Tim

Hmmmmm I dunno, one guy who tried to generalize this kind
of geometry of complex numbers ended up inventing the
quaternions...

...and we all know how horrible that turned out to be
(their imaginary parts can describe 3-D rotation and the
whole concept leaked into groups, matrices, and god knows
what).
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Tim Golden
science forum Guru Wannabe


Joined: 12 May 2005
Posts: 176

PostPosted: Wed Jul 19, 2006 2:34 am    Post subject: Re: Rotations - why are they not vectors Reply with quote

Terry Padden wrote:
Quote:
Most of what you write is correct - i.e. heading in the right direction -
except for that "Pi" stuff; but remember there are innocent mathematicians
reading this and we don't want to frighten them.
However if you attach the magic phrase "forgetful functors" to what you have
written they will mistake you for one of their senior wizards and let you
pass without attacking you - unlike what they try on me.

For now I am just trying to get them to think about vectors. It is not
easy. They are taught so much rubbish it is hard for them to think clearly.
You ask them a simple, but not easy, question about vector space axioms and
they - with one or two honourable exceptions -automatically talk about
groups, matrices, Rn, Euclidean space, Lie Algebras, "pi", and god knows
what; any old rubbish except considering and responding to the question ;
and of course they think they are really smart mathematicians - god help us
!

Rotation seems to be a product relationship. The complex numbers
perform geometrical rotation via product. Your winding concept is
pretty easily expressed in the polar coordinate system but what about
for a value a+bi? As I read around about winding number
http://www.geom.uiuc.edu/~ross/webtex/webmmlSamples/node2.html
I see that it is mostly used in the context of paths. But should it
apply to the complex plane?

Here is one way to implement winding counters in them. So for example
rather than a+bi lets just look at just the a part.
a i i i i i = a i
would be the ordinary notation. But to implement counting we need to
add a component to the elemental structure like:
( 0, a ) i i i i i = 1, a i
or
( 2, 1.2 )( 3, 2.0 i ) = 5, 2.4 i
and
( 0 , -i )( 0 , -i ) = 1, i .
The question arises wether these are nondecreasing as more products are
taken, or can they unwind? I think they are nondecreasing; they are
coupled to the handedness of the coordinate system. So the discrete
product would produce a discontinuity on the positive real axis, where
a slight change toward -i from a slightly positive i value will cause
an abrupt change, though the usual math is undisturbed.

Quote:
From a physical point of view this may be meaningful since handedness
plays a part in physics. If an iterative product raises the winding

count should an iterative division process bottom out? That would imply
disallowing negative winding numbers which might be a coherent choice.

It all seems contrived but might be worth keeping an awareness of these
options.

-Tim
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Terry Padden
science forum beginner


Joined: 17 Jun 2005
Posts: 28

PostPosted: Wed Jul 19, 2006 12:25 am    Post subject: Re: Rotations - why are they not vectors Reply with quote

"Timothy Golden BandTechnology.com" <tttpppggg@yahoo.com> wrote in message
news:1153244888.808681.236240@b28g2000cwb.googlegroups.com...
Quote:

These 'winding numbers' can be applied to polysign numbers:
http://bandtechnology.com/PolySigned/PolySigned.html
But I do not do anything with them. Instead they disappear via modulo
math.
I believe that the modulo math is correct, but when a product is taken
perhaps the net value could be accounted for. Is there a physical
meaning that you would assign? In terms of string you could have an
unwinding almost as an independent entity since the usual math just
throws it away. At a macro level we could look at the solar system and
ask if its winding is influential. Could magnetic winding and unwinding
explain the discrepancy of the planetary magnetic moments? They are
claimed to oscillate.
Perhaps electron spin is a more appropriate thing to worry about.
There is a funny 2pi/sign relation to do with electron spin.
There seems to be an important distinction between continuous and
discrete rotation.
If we rotate a globe on its axis half way around we cannot inherently
say which way it went unless the rotation was continuous. The very word
'rotation' implies continuous I think, but the polysign construction
allows discrete rotations. This stuff seems pretty suggestive.

-Tim


Most of what you write is correct - i.e. heading in the right direction -
except for that "Pi" stuff; but remember there are innocent mathematicians
reading this and we don't want to frighten them.
However if you attach the magic phrase "forgetful functors" to what you have
written they will mistake you for one of their senior wizards and let you
pass without attacking you - unlike what they try on me.

For now I am just trying to get them to think about vectors. It is not
easy. They are taught so much rubbish it is hard for them to think clearly.
You ask them a simple, but not easy, question about vector space axioms and
they - with one or two honourable exceptions -automatically talk about
groups, matrices, Rn, Euclidean space, Lie Algebras, "pi", and god knows
what; any old rubbish except considering and responding to the question ;
and of course they think they are really smart mathematicians - god help us
!
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