# B Does right/left spin reverse in tunneling particles?

1. Feb 15, 2017

### fredt17

As I understand it, a relativistic reversal can occur in a Lorentz
boost. A particle's forward angular momentum can become backward
angular momentum, if the observer accelerates sufficiently. But the
particle and its angular momentum are unchanged. The only change
is in the observer’s frame of reference.

Could tunneling particles similarly reverse right/left angular
momentum from a change in the observer’s frame of reference?

The basis for this question is that a spinning object passing through
a surface twice reverses its apparent direction of spin, at least to an
observer on the surface.

Quantum tunneling maybe a result of quantum uncertainty, or
a wormhole, a loop, a tunnel, or some other mechanism. But this
reversal effect does not depend on the mechanism. This effect is
determined solely by the observer’s frame of reference.

This effect can be seen by poking a spinning pencil through a
folded sheet of paper. At one intersection with the paper,
the pencil will be spinning clockwise. At the other intersection, the
pencil will be spinning counter-clockwise, relative to the surface.

But there is only one pencil spinning in one direction. The apparent
direction of spin depends solely on which end of the tunnel (or wormhole
or other mechanism) the observer is looking at. It is purely a relativistic
effect.

So perhaps a Lorentz-boost-like relativistic reversal could occur in
tunneling particles. Has an experiment ever been conducted to test for
such an effect?

2. Feb 15, 2017

### Staff: Mentor

Yes--and you have to be careful describing what the effect actually is. Note that this effect is not particular to relativity; it also occurs in Newtonian mechanics. The apparent reversal is of the particle's spin relative to its direction of motion. It's just a consequence of changing the observer's motion relative to the object: if the object is moving in the positive $x$ direction, for example, in the original frame, and spinning clockwise about an axis pointing along its direction of motion, then in the new frame, it will be moving in the negative $x$ direction, and spinning counterclockwise about an axis pointing along its (new) direction of motion. But the change is not in its spin, only in its direction of relative motion, because of the change in the observer's frame.

More precisely, relative to vectors normal to the surface on the same side of it. This is a different kind of effect than what you were describing before: it has nothing to do with changing frames, at least not as you're describing it. It has to do with the change in orientation of the surface from one intersection to the other.

Not if "relativistic" here is intended to mean the same thing it meant earlier in your post. See above.

Also, the "tunnel" here has nothing whatever to do with quantum tunneling; it's just a surface intersecting an object twice. So the real answer to your question is no, the kind of effect you are talking about is not going to appear in quantum tunneling.

3. Feb 16, 2017

### fredt17

Thanks for your response. Could you clarify one point?

The apparent reversal is of the particle's spin relative to its direction of motion.
It's just a consequence of changing the observer's motion relative to the object:

Wouldn't the effect occur independent of the observer's motion? If Bob
is at one intersection on the surface, and Alice is at the other, wouldn't
their observations be different?

4. Feb 16, 2017

### Staff: Mentor

Which effect? What you quoted from me (please use the PF quote feature, btw) was referring to your first example, which is an effect due to a change in relative motion. What you are asking about in the last paragraph of your latest post is referrring to your second example. The effect in your second example depends on the direction that Alice and Bob view as the "positive" $x$ direction. This is a change in frame of reference, just not one due to relative motion (it's due to a spatial rotation). Neither of your examples describes any change in the object itself or its angular momentum.

5. Feb 16, 2017

### fredt17

One question. Whatever is happening in quantum tunneling that creates the reversal in apparent angular momentum
is this similar to the opposing right/left angular momentum in entangled particles?
Is it possible that entangled particles are connected by the same mechanism that
allows particles to appear to tunnel?

6. Feb 17, 2017

### Staff: Mentor

None of your examples are examples of quantum tunneling doing this. Can you give an example of quantum tunneling doing this?

Entanglement and tunneling are both quantum processes, but they're not the same quantum process. So I think the answer to this is no.

7. Feb 18, 2017

### fredt17

Perhaps I am confused (certainly a definite possibility). My question related to the way tunneling and quantum entanglement may share
a common attribute of reversed right/left angular momentum . Maybe they don't, but if they do, this may be from a similar source,
namely that the two effects are a result of connections that pass through the surface of our world twice.

8. Feb 18, 2017

### Staff: Mentor

Tunneling does not reverse right/left angular momentum.

I'm not even sure what this means--what is "the surface of our world"? But in any case it doesn't appear to apply to either tunneling or entanglement. It doesn't even apply to the original case you brought up in your OP, of a Lorentz boost.

9. Feb 18, 2017

### fredt17

Well, how do entangled particles interact instantaneously? There appears to be some method of transmission. And if that interaction takes zero time,
then there may be zero distance between the particles, from the particles frame of reference. That could be a tunnel or a wormhole or some other mechanism,
but the effect on left/right angular momentum would be the same. The two intersections would display opposite directions of spin.

10. Feb 18, 2017

### Staff: Mentor

They don't.

11. Feb 19, 2017

### fredt17

I hope you will consider Maldacena's article on entangled black holes in the November 2016 Scientific American.
His theory is based on entangled particles and he suggests entangled black holes could be connected by
a wormhole, and thus could interact to some extent.
His illustration shows a wormhole looping beneath a surface and reconnecting with the surface
at a different location. If an object entered that wormhole spinning clockwise, it would emerge at the
other wormhole spinning counter-clockwise.

12. Feb 19, 2017

Staff Emeritus
After 11 messages, I still can't figure what this thread is about.

13. Feb 19, 2017

### ZapperZ

Staff Emeritus
This is highly speculative! You need to show the physics that support this.

Spin-dependent tunneling is a known process. It resembles nothing like you mentioned here.

Zz.

14. Feb 19, 2017

### fredt17

Sorry for the confusion. Let me try again.

As suggested in Maldacena's article in Scientific American, entangled black holes may connect two different locations in
our universe through a wormhole.

This concept might also be applicable to quantum particles as quantum entanglement was the foundation of Maldacena's theory.
If so, a particle passing through such a wormhole could reverse its angular momentum.

Evidence in support of this idea might be found in possible reversals in tunneling particles. Has an experiment
ever been conducted to test for this possibility?
.

15. Feb 19, 2017

### ZapperZ

Staff Emeritus
Sorry, what evidence is there to connect this to tunneling particles? The particles undergoing tunneling do NOT go through "a wormhole". Do a search on "inelastic tunneling" where I've posted rebuttals to the idea that the particles do not pass through the barrier.

Again, spin-dependent tunneling is so well-known, it is not even funny.

Zz.

16. Feb 19, 2017

### fredt17

You could be right. Quantum tunneling is not what we know as tunneling.
It is only a label.

But forward/backward quantum momentum reverses in a Lorentz boost without any interaction
with the particle or its angular momentum.

So however the particle is getting from one place to another, a change in the observer's frame
of reference (as occurs in a Lorentz boost) could produce a similar reversal in right/left
angular momentum.

This is very speculative (to put it mildly), but it seems simple enough to test for..
.
.

17. Feb 19, 2017

### ZapperZ

Staff Emeritus
Then the title of this thread and your starting premise is faulty. This has nothing to do with the tunneling phenomenon.

Zz.

18. Feb 19, 2017