An issue between GR and QM
Rich L.
between General Relativity and Quantum Mechanics for some time now.
It seems to me that there is a major conceptual issue around exactly
where/when is something located. Let me suggest a precise example:
Suppose we have a two slit experiment with a source emitting massive
particles (let's say neutrons, for example), a wall with two apertures
in it and a detector on the other side. To do General Relativity in
this situation, we need to know the energy density (actually, the
stress-energy tensor) throughout this volume. From this energy
density the curvature of space can be calculated. Quantum Mechanics
is of limited help here, however, as the wave function is generally
recognized to NOT represent the actual location of the particle at any
time, but only our degree of knowledge about its location and
activity. In particular, it seems from the two slit experiments
themselves that one cannot say that the particle followed a particular
path (e.g. through one or the other slit) to travel from the source
to the detector, but in some sense passes through both apertures.
Bells Inequality and the experiments based on it seem to suggest that
even the particle does not "know" where it is or where it is going
until the moment of detection. (I have some arguments with this
interpretation, but that is a slightly different issue.)
So my question is: what can we say about where the particle is at any
given time, and is that knowledge sufficient to do the calculations of
GR? I'd like to throw out a few possiblities, even though some of
them clearly don't make sense.
1) The particle actually does follow a single, well defined path
through the experiment, even though QM cannot predict this path and we
don't have knowledge of this path, even after detection. This is the
most classical conception of the particles motion, and is generally
considered to be incompatible with QM.
2) The particle follows a fuzzy path through the aparatus, possibly
splitting into two or more branches that pass through each of the
slits separately and ending at the detector. This is different from
the QM wave function in that it includes only the case of a particle
emitted at a particular time and then being absorbed by the detector
at a specific later time. This concept is an attempt to blend the
completely deterministic and localized classical concept of the
particle with the fuzzy wave-like conception of QM. Again, we may not
be able to determine the shape-extent of this fuzzy path in advance,
but we might, in concept, infer it after detection.
3) The particle "follows" the QM wave function up until detection,
then suddenly condenses into the detector. This weird conception
seems to be implied by some descriptions of Bell Inequality
experiments, but is clearly incompatible with Relativity as currently
formulated.
I don't find any of these concepts very reasonable. GR seems to
require that the particle be at a particular location at any instant
(or at least there needs to be a density function that propagates with
time), yet that seems to be incompatible with QM theory and
experiment. I think this indicates that there is a fundamental
conceptual error in one or both theories. I'd like to get peoples
opinion about this question, and what the conceptual error might be.
Rich L.
mpc755
The C-60 molecule enters and exits a single slit and the displacement
wave it creates in the aether enters and exits all available slits.
The displacement wave creates interference when exiting the slits
which alters the direction the C-60 molecule travels. Detecting the
C-60 molecule causes decoherence of the interaction of the C-60
molecule and the wave(s).
~NewsgroupDirect
> between General Relativity and Quantum Mechanics for some time now.
> It seems to me that there is a major conceptual issue around exactly
It seems to me that QM describes decoherence of a non-dimensional
cloud of probabilities into specific observations, whereas GR describes
after-the-fact spacetime relationships among such observations.
Tom M.
meopemuk
> �I think this indicates that there is a fundamental
> conceptual error in one or both theories. �I'd like to get peoples
> opinion about this question, and what the conceptual error might be.
I think that QM is perfectly OK as it is, but GR needs a revision. If
we treat gravitational interaction between particles similar to other
forces (i.e., as a distance- and velocity-dependent potential rather
than the "space-time curvature"), then the QM/GR controversy
disappears.
Mike
Surely, there is a common theory that gives rise to both QM and GR. QM
is the theory of the very small, and GR is the theory of the very
large. And typically the very large is considered the classical limit
of QM. So here we should probably assume that GR is the classical
limit of some properties of QM. The classical limit in non-
gravitational physics is derived from the invariance of the lagrangian
in the path integral formulation of QM. And we also know that GR can
be derived as the invariance of the Einstein-Hilbert action. So we put
the Einstein-Hilbert action in the path integral formulation and hope
it will give us a quantum theory of gravity. But that does not explain
why the Einstein-Hilbert action is correct. It may be, and I think it
is, that the Einstein-Hilbert action is an approximation, and there
might be other terms in that action which will only be determined once
we know the underlying theory that gives rise to both QM and GR. I
suppose these other terms will explain dark matter and dark energy.
These other terms are probably higher order derivatives of the
curvature that appears in the Einstein-Hilbert action. So they might
explain the change in curvature at larger scales which is dark matter,
and they might explain the acceleration of the curvature which is dark
energy.
Rich L.
addresses the conceptual issue I'm trying to resolve. GR treats
energy (of any form) as the source for curvature of space. This
implies that there must be some sort of definite location for the
energy in order to determine the geometry, but that seems to be
incompatible with our understanding of QM.
It isn't clear to me that the Aether concept offered by mpc755 helps
with this issue, as that has generally been discredited (unless there
is a more refined theory of the Aether that I'm not aware of). If
there is an Aether, the description given in the earlier post implies
that the molecule has a precise and specific location, even if we
don't know where it is. It isn't clear to me that that is compatible
with experiments, such as those testing Bells Inequality.
Tom M. seems to be suggesting that GR responds to the cloud of
probabilities "after the fact", but I have difficulty with this
concept as well. The cloud of probabilities is, first of all, not
real. They exist only as a mathematical tool. Second, the cloud does
not necessarily resolve itself for a long time. For example, two
correlated photons emitted early in the universe may not be detected,
and their cloud resolved, for many billions of years until one or both
photons are detected. How is the geometry of space to respond to
these photons during the intervening billions of years? How is their
propagation through the universe possible without some definite
geometry for the space?
This inspires yet another concept for propagation of the particle
through the experiment: the particle could "disappear" at the source
and "appear" again only when detected, and have no existence, and no
impact on the geometry of space, in between these two events. I don't
like this much on the basis of conservation of energy, but I'm not
sure we really have any experimental evidence that refutes this
concept either.
Mike suggests that GR is a macroscopic theory and QM a microscopic
theory and that never the twain shall meet. I'm trying to explore how
to make these two meet up, and I think this question addresses a
concept that will have to be re-conceived first, or at least as part
of the solution.
Thanks to all for your responses,
Rich L.
mpc755
>
> It isn't clear to me that the Aether concept offered by mpc755 helps
> with this issue, as that has generally been discredited (unless there
> is a more refined theory of the Aether that I'm not aware of). �If
> there is an Aether, the description given in the earlier post implies
> that the molecule has a precise and specific location, even if we
> don't know where it is. �It isn't clear to me that that is compatible
> with experiments, such as those testing Bells Inequality.
>
Bell's Inequality is testing against 'Hidden-value theories" which is
not at all what I am suggesting. 'Hidden-value theories' are a false
premise. For the EPR Paradox (http://en.wikipedia.org/wiki/
EPR_paradox), the electron-positron pair are not entangled. All that
is occurring is for momentum to be conserved, which it is in EPR, the
electron-positron pair must be exact opposites in every measurable
way.
For more information on Aether Displacement, see the Aether
Displacement thread in this forum.
Mike
> It doesn't seem to me that any of the above responses directly
> addresses the conceptual issue I'm trying to resolve. �GR treats
> energy (of any form) as the source for curvature of space. �This
> implies that there must be some sort of definite location for the
> energy in order to determine the geometry, but that seems to be
> incompatible with our understanding of QM.
So if massive partices are a superposition of possible location, then
so must the curvature be in superposition. I don't have a problem with
that.
...
> Mike suggests that GR is a macroscopic theory and QM a microscopic
> theory and that never the twain shall meet. �I'm trying to explore how
> to make these two meet up, and I think this question addresses a
> concept that will have to be re-conceived first, or at least as part
> of the solution.
No, I was saying quite the opposite, that if there is an underlying
theory from which particle QM and GR both emerge, then the two
theories absolutely do meet ... at that underlying theory.
Oh No
>It doesn't seem to me that any of the above responses directly
>addresses the conceptual issue I'm trying to resolve. GR treats
>energy (of any form) as the source for curvature of space. This
>implies that there must be some sort of definite location for the
>energy in order to determine the geometry, but that seems to be
>incompatible with our understanding of QM.
yes. this is the fundamental, unresolved issue. see my response to Ken,
and also my discussion in the context of relational quantum gravity,
which contains links to the papers by Page and Geilker and Eppley &
Hannah
http://rqgravity.net/SpacetimeStructure
Regards
--
Charles Francis
moderator sci.physics.foundations.
charles (dot) e (dot) h (dot) francis (at) googlemail.com (remove spaces and
braces)
Mike
> Thus spake Rich L. <ralivings...@sbcglobal.net>
>
> >It doesn't seem to me that any of the above responses directly
> >addresses the conceptual issue I'm trying to resolve. �GR treats
> >energy (of any form) as the source for curvature of space. �This
> >implies that there must be some sort of definite location for the
> >energy in order to determine the geometry, but that seems to be
> >incompatible with our understanding of QM.
What I'd like to know is if greater matter density makes curvature
larger, then how could the universe expand at all? Wouldn't such
densities at the big bang cause the universe to curl up and die?
Rich L.
If inflation is real, I think that implies something that would
counter act that induced curvature. Perhaps there was a "surplus" of
"dark energy" initially that, at some reduced temperature, condensed
out into ordinary matter and energy which is constrained to sublight
speeds by Relativity, thus bringing the inflationary epoch to an end.
Of course I'm waving my hands furiously here as no one has any idea
what "dark energy" is, if it even exists.
Rich L.
~NewsgroupDirect
Rich L:
> Tom M. seems to be suggesting that GR responds to the cloud of
> probabilities "after the fact", but I have difficulty with this
> concept as well. The cloud of probabilities is, first of all, not
> real. They exist only as a mathematical tool. Second, the cloud does
> not necessarily resolve itself for a long time. For example, two
> correlated photons emitted early in the universe may not be detected,
> and their cloud resolved, for many billions of years until one or both
> photons are detected. How is the geometry of space to respond to
> these photons during the intervening billions of years? How is their
> propagation through the universe possible without some definite
> geometry for the space?
>
> This inspires yet another concept for propagation of the particle
> through the experiment: the particle could "disappear" at the source
> and "appear" again only when detected, and have no existence, and no
> impact on the geometry of space, in between these two events. I don't
> like this much on the basis of conservation of energy, but I'm not
> sure we really have any experimental evidence that refutes this
> concept either.
Here's a diagram of how I presently reconcile the observed complexity:
◄
eternal coherence
▼ ▲
infinite potential
▼ ▲
boundlessly inflating probabilities
▼ ▲
fractal awareness
▼ ▲
decohering perception
▼ ▲
observational universe
►
Infinite potential
born of eternal coherence
inflates boundless possibilities
eventuating in fractal awareness
proliferating as individual perspectives
upon universal decoherence.
Decohering perception
instantiates the spacetime universe
of its observation.
All else is non-dimensional.
Tom Murphy
Rich L.
Are you able to express these ideas in a mathematically precise way?
I don't know how to do physics with these concepts alone.
Rich L.
Hendrik Boom
Have a look at the Big Bounce, partway down the page at http://
math.ucr.edu/home/baez/week280.html
-- hendrik
.
brad
> I've been trying to understand exactly what is the incompatibility
> between General Relativity and Quantum Mechanics for some time now.
> It seems to me that there is a major conceptual issue around exactly
> where/when is something located.
Indeed, Time is not properly defined. Gravity affects Time. A precise
model
that shows how this occurs is necessary.
>�Let me suggest a precise example:
> Suppose we have a two slit experiment with a source emitting massive
> particles (let's say neutrons, for example), a wall with two apertures
> in it and a detector on the other side. �To do General Relativity in
> this situation, we need to know the energy density (actually, the
> stress-energy tensor) throughout this volume.
And that is another problem, because one is left to assume the
existance of
the Gravitational Field without any idea as to how it arises. Everyone
knows it's
there! But, how? Einstein bypassed this problem by saying that
trajectory is proof of
the shape of space. No one has ever explained how matter alters the
shape of space.
The concept of 'curved space' may be an intellectual dead end.
>�From this energy
> density the curvature of space can be calculated.
What if there were no energy involved? Suppose motion in a
Gravitational
Field results from only from Hamilton's Principle? If matter displaces
space,
then the intersection of displaced space between 2 interacting masses
would
result in a volume of higher density space. Trajectories will be
altered because
a *shorter space-time path* will exist and the action principle, being
always paramount,
will ensure that motion is altered. To me , the Least Action Principle
lies at the
heart of Classical Mechanics. Under these conditions one could make a
case
that Fermat's Principle and Hamilton's Principle are just variations
of the same
principle.
>�Quantum Mechanics
> is of limited help here,
I think because the masses and volumes of spacetime involved are not
great enough.
> I don't find any of these concepts very reasonable. �GR seems to
> require that the particle be at a particular location at any instant
> (or at least there needs to be a density function that propagates with
> time), yet that seems to be incompatible with QM theory and
> experiment. �I think this indicates that there is a fundamental
> conceptual error in one or both theories. �I'd like to get peoples
> opinion about this question, and what the conceptual error might be.
>
> Rich L.
I think Gravity *requires* a greater ratio of matter to spacetime.
Consider
that for 2 massive objects gravity actually decreases as they become
very
close. For those 2 objects there is less space to alter as they
converge.
Brad
Oh No
glird
> �Thus spake Mike <mj...@sirus.com>>On Sep 26, 8:26�am, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:
> >> Thus spake Rich L. <ralivings...@sbcglobal.net>
>
> >> >It doesn't seem to me that any of the above responses directly
> >> >addresses the conceptual issue I'm trying to resolve. �GR treats
> >> >energy (of any form) as the source for curvature of space. �This
> >> >implies that there must be some sort of definite location for the
> >> >energy in order to determine the geometry, but that seems to be
> >> >incompatible with our understanding of QM.
>
> >What I'd like to know is if greater matter density makes curvature
> >larger, then how could the universe expand at all? Wouldn't such
> >densities at the big bang cause the universe to curl up and die?
>
> At the time of the big bang the universe was already flying apart.
There are two incompatible points of view expressed there, and a
third that is unrelated to them both.
1. GR treats energy (of any form) as the source for curvature of
space.
2. Greater matter density makes curvature larger.
3. When time began "the universe was already flying apart".
Which is wrong is a matter of choice. (I say all three - plus one -
are false.}
glird