

Our universe within a larger universe? So suggests wormhole research (2010) - coderdude
http://newsinfo.iu.edu/news/page/normal/13995.html

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pdonis
A red flag: the paper is using isotropic coordinates, which don't cover the
region inside the horizon (which would be the region including the wormhole if
it's present); they only cover the exterior region. That makes me suspicious
that whatever result the paper claims to be deriving is a mathematical
artifact of the coordinates being used, and does not reflect the actual
physics.

Looking at the figures on the ScienceDirect page...

[http://www.sciencedirect.com/science/article/pii/S0370269310...](http://www.sciencedirect.com/science/article/pii/S0370269310003370)

...the second figure bears this out; it shows the worldline of an object going
through the wormhole (A-B-C-D) as disconnected, which is physically invalid;
it violates local energy conservation. So I've got to conclude that the
paper's claimed result is not physically valid.

Note: The ScienceDirect page claims that "B and C are the same event", but you
can't just claim that arbitrarily; you have to show that it's physically
valid. I strongly doubt that the paper can do that, for reasons which are too
long to fit in the margin of this post. :-)

~~~
kevin_rubyhouse
I see comments like this all the time - where people with a strong background
find faults in scientific articles and such written online. Why do these
articles get things wrong so often? In this case I think you're saying the
paper itself should not have been using isotropic coordinates. Is this because
of different schools of thought in this higher realm of physics? Or... what?

~~~
pdonis
_Why do these articles get things wrong so often?_

Different journals have different standards of rigor. I believe Physics
Letters B, where this paper was published, is one of the less rigorous ones.
They might also be more inclined to publish speculative papers, figuring that
it's better to publish it and let someone else publish a refutation if it's
wrong, as opposed to refusing to publish it in the first place.

 _In this case I think you're saying the paper itself should not have been
using isotropic coordinates._

I suspect that the use of isotropic coordinates misled the paper's author,
yes. I can't know for sure since I can't read the paper itself (it's behind a
paywall). [Edit: someone downthread posted a link to an arxiv preprint; I'll
take a look and respond further there.]

 _Is this because of different schools of thought in this higher realm of
physics?_

This could be a factor--it certainly is in some cases--but I'm inclined to
think that in this case it's more a matter of a less rigorous journal being
willing to publish a speculative paper, as above.

~~~
Osmium
I think you might be doing Physics Letters B a bit of a disservice there. I'm
not saying it's the best, but it's certainly reputable and there are a lot
worse...

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gjm11
(This is from April 2010.)

As usual, phys.org have simply reproduced someone else's press release and
made a bunch of the words in it link to other phys.org pages. The original
press release is at <http://newsinfo.iu.edu/news/page/normal/13995.html> and
differs from the phys.org version only in not being blogspam.

An arXiv preprint of the paper in question is at
<http://arxiv.org/abs/0902.1994>; I think it's actually identical to the
version published in Phys. Lett. B.

There's a bit more information on Popławski's Wikipedia page:
<http://en.wikipedia.org/wiki/Nikodem_Pop%C5%82awski>.

------
Xcelerate
I am frequently bothered by the misuse of the word "universe". It is defined
as the totality of all that exists -- that we can observe. So if there is
anything out there, which we didn't think existed before, but we now suspect
does exist, well... it's just part of our same old universe.

~~~
dmayle
I'm not an astrophysicist, so hopefully one can chime in, but my understanding
is that 'universe' == the x,y,z,t continuum. Anything outside of that is a
different 'universe'.

If you can imagine a place that requires alternate dimensions in order to
access (e.g. klein bottle), you would be traveling through a different
'universe' (though it is possible that a passage through other universes could
lead back to our own). If, however, the other place has a different x,y,z,t
continuum, even if there is a passage between the two (wormhole), it's still a
different universe.

EDIT: (Appending this) Also, if you think of the word universe, it means one
totality (uni=one, verse=totality). So, if you want to refer to all that can
exist, you probably want to say 'omniverse'.

~~~
yk
I think the concept of outside the universe or inside of it are not developed
in a sufficiently rigorous way to really define what a universe is. However in
some theories objects appear were it is actually quite natural to speak of an
universe and something else. For example there is a unique way to extend the
Schwartzschild space time [1] such that all geodesics either terminate in the
singularity or go to infinity. But if you do this, then a region of the
spacetime appears, that is 'on the other side' of the black hole. And there is
no way to communicate with this region of spacetime, since all geodesics
leading to it are space like, that is they would require (local) superluminal
travel. It is therefore sometimes called a parallel universe.

It is similar in certain string theories, that patches of spacetime with
different physical laws appear, this is then called the landscape. Or the
multiverse in some cosmological models, where a far away region may appear,
which is vastly different from or 'local' universe, that is in this case
everything we can possibly observe.

So I think that it is quite possible that a theory of quantum gravity will
have some object which we will call a universe, but until we have such a
theory the appearance of anything outside of the universe marks highly
speculative physics.

[1] That is the spacetime describing a black hole.

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drucken
Could you not prove this (or at least go a long way to do it) just by finding
a "white hole"?

~~~
mvzink
I am probably totally misunderstanding all this, but it sounds like the big
bang is the white hole.

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Aardwolf
And that larger universe is yet within another larger universe! We must go
deeper.

~~~
evanb
<http://inception.davepedu.com/>

