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From: PD on 19 Jul 2010 14:59
On Jul 16, 2:16 pm, va...(a)icmf.inf.cu wrote:
> I suppose we are all in agreement about the increase of U(r) with an
> increase of r. Has U(r) a finite maximal limit value when r tends to
> infinite? In case of positive answer, which is that maximal value?

You may have heard in freshman physics that the zero point of
potential is physically arbitary. In all interactions, the only thing
that is important is the *change* in potential energy between initial
and final states, and that number is independent of the overall scale.

It is frequently customary to put U(r=infinity) = 0, so that all
values of U(r) for finite r are negative. But this by no means
required and many problems are more convenient to solve with a
completely different choice.

PD
From: PD on 19 Jul 2010 15:00
On Jul 19, 8:38 am, "Dono." <sa...(a)comcast.net> wrote:
> On Jul 16, 12:16 pm, va...(a)icmf.inf.cu wrote:
>
> > I suppose we are all in agreement about the increase of U(r) with an
> > increase of r.
>
> No, imbecile, the potential DECRESES with distance. No one agrees with
> your idiocies.

You may want to check your comment. The OP was asking about a positron-
electron pair.
From: valls on 19 Jul 2010 17:38
On 19 jul, 12:11, dlzc <dl...(a)cox.net> wrote:
> Dear va...:
>
> On Jul 19, 4:24 am, va...(a)icmf.inf.cu wrote:
>
>
>
>
>
> > On 16 jul, 15:13,dlzc<dl...(a)cox.net> wrote:
> > > On Jul 16, 12:16 pm, va...(a)icmf.inf.cu wrote:
>
> > > > I suppose we are all in agreement about the
> > > > increase of U(r) with an increase of r. Has
> > > > U(r) a finite maximal limit value when r
> > > > tends to infinite?
>
> > > r probably will tend to a maximum at r_U
> > > (radius of the Universe, in a non-expanding,
> > > flat Universe), and r_U may be a function of
> > > time as well, in this Universe.  If one of
> > > the charges moves across the Rindler horizon
> > > of the other...
>
> > > > In case of positive answer, which is that
> > > > maximal value?
>
> > > That'll probably depend on when you ask.
> > > But I'd think it will asymptotically approach
> > > some value with increasing values of r.
>
> > Even using modern cosmology, you give only a
> > naive answer. I was waiting a much more
> > detailed answer, a quantitative one related with
> > the electron known intrinsic constants.
>

> Then maybe you'll need to develop this answer yourself.
>
Sure. I will do it a little ahead.
> > Maybe this is an open problem in today Physics?
>
> Finding the size of the Universe is, yes.
>
No, I refer only to find the finite maximal limit value considered for
the potential energy.
> > I found a very simple answer using only 1905
> > Relativity:
>
> Who cares about your insistence on 105 year old physics?  Why did I
> know you were going to drag this back to your old stomping grounds?
>
If you can’t offer an adequate solution even using modern cosmology,
it seems to me reasonable that you would be interested in knowing one
that uses only 1905 Relativity.
Anyway, it is a lot much simple to show the solution that to talk
about its existence.
Following 1905 Relativity (1905R), the maximal limit value for the
potential energy of a pair electron-positron is 2 m_e c^2, where m_e
is the today rest mass for the free electron. That value corresponds
to the experimentally measured energy of the photons that result from
the pair annihilation.
The essential support is in a thread I opened some time ago. The title
and the link are the following:

Potential energy in 1905 Relativity
http://groups.google.com.cu/group/sci.physics.relativity/browse_frm/thread/0ea5fc8334fa1353?hl=es#

I found (many years ago) analysing the 27Sep1905 Einstein’s paper in
his historical context that “The (rest) mass of a body is a measure of
its (potential) energy-content”. This is a particular case of his much
general result about mass measuring energy. As the arbitrary additive
constants characteristic of potential energies (managed by 1905
Einstein) all disappear in his final result (mass has not an arbitrary
additive constant), this means that 1905 Einstein finds a unique
natural zero for potential energies (even if not realizing it at all).
And the potential field energy and the body rest energy is one and the
same thing.

> David A. Smith

RVHG (Rafael Valls Hidalgo-Gato)
From: valls on 19 Jul 2010 17:56
On 19 jul, 13:59, PD <thedraperfam...(a)gmail.com> wrote:
> On Jul 16, 2:16 pm, va...(a)icmf.inf.cu wrote:
>
> > I suppose we are all in agreement about the increase of U(r) with an
> > increase of r. Has U(r) a finite maximal limit value when r tends to
> > infinite? In case of positive answer, which is that maximal value?
>
> You may have heard in freshman physics that the zero point of
> potential is physically arbitary. In all interactions, the only thing
> that is important is the *change* in potential energy between initial
> and final states, and that number is independent of the overall scale.
>
Well, you don’t answer my question, but what you say is compatible
with an infinite value for U(r) when r tends to infinite (any
arbitrary additive constant doesn’t change the infinite). Anyway, I
consider more interesting the other alternative with a finite maximal
limit value. I just address it in an answer to dlzc (David) in this
same thread. I consider adequate to refer you to it, instead of
repeating here my analysis.
> It is frequently customary to put U(r=infinity) = 0, so that all
> values of U(r) for finite r are negative. But this by no means
> required and many problems are more convenient to solve with a
> completely different choice.
>
> PD

RVHG (Rafael Valls Hidalgo-Gato)
From: PD on 22 Jul 2010 14:58
On Jul 19, 4:56 pm, va...(a)icmf.inf.cu wrote:
> On 19 jul, 13:59, PD <thedraperfam...(a)gmail.com> wrote:> On Jul 16, 2:16 pm, va...(a)icmf.inf.cu wrote:
>
> > > I suppose we are all in agreement about the increase of U(r) with an
> > > increase of r. Has U(r) a finite maximal limit value when r tends to
> > > infinite? In case of positive answer, which is that maximal value?
>
> > You may have heard in freshman physics that the zero point of
> > potential is physically arbitary. In all interactions, the only thing
> > that is important is the *change* in potential energy between initial
> > and final states, and that number is independent of the overall scale.
>
> Well, you don’t answer my question, but what you say is compatible
> with an infinite value for U(r) when r tends to infinite (any
> arbitrary additive constant doesn’t change the infinite).

Read what I wrote. U(r)=0 is quite finite.

> Anyway, I
> consider more interesting the other alternative with a finite maximal
> limit value. I just address it in an answer to dlzc (David) in this
> same thread. I consider adequate to refer you to it, instead of
> repeating here my analysis.
>
> > It is frequently customary to put U(r=infinity) = 0, so that all
> > values of U(r) for finite r are negative. But this by no means
> > required and many problems are more convenient to solve with a
> > completely different choice.
>
> > PD
>
> RVHG (Rafael Valls Hidalgo-Gato)

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