This is all good fun and provides
a little of the flavor of present efforts to create a fresh new tarpaulin to cover
the known facts and include gravity.
For the record my new metric for
physics allows us to construct the cosmos without any recourse to a spare
dimension or two although such a spare dimension can be posited with little disturbance
to hold the space time manifold itself although this is likely
unnecessary. Please note I have
published the third and forth order but it is easy but time consuming to extend
it to the necessary nth order for cosmological discussions.
The reason that it has been
necessary to play with higher dimensions is because of the underlying
assumption in our mathematica that the inverse of empirical infinity is
zero. This is a bad mistake and has led
to lots of nonsense.
It is enough to know that no
point in the universe is perfectly smooth.
If you recall nothing else, then you should not go to far wrong
Our universe has three dimensions
because it is the least needed. Proving
that is certain to produce a headache.
WHY DOES OUR UNIVERSE HAVE THREE DIMENSIONS?
Analysis by Jennifer
Ouellette
Thu Jan 19, 2012 01:02 PM ET
Why does our universe look the way it does? In particular, why do we
only experience three spatial dimensions in our universe, when superstring
theory, for instance, claims that there are ten dimensions -- nine
spatial dimensions and a tenth dimension of time?
Japanese scientists think they may have an explanation for how a
three-dimensional universe emerged from the original nine dimensions of space.
They describe their new supercomputer calculations simulating the birth of
our universe in a forthcoming paper in Physical Review Letters.
Before we delve into the mind-bending specifics, it's helpful to have a
bit of background.
The Big Bang theory of how the universe was born has been bolstered by
some pretty compelling observational evidence, including the measurement of the
cosmic microwave background and the relative abundance of elements.
But while cosmologists can gaze back in time to within a few seconds of
the Big Bang, at the actual moment it came into existence, when the whole
universe was just a tiny point -- well, at that point, the physics we know and
love breaks down. We need a new kind of theory, one that combines relativity
with quantum mechanics, to make sense of that moment.
Over the course of the 20th century, physicists painstakingly
cobbled together a reasonably efficient "standard model" of physics.
The model they came up with almost works, without resorting to extra
dimensions. It merges electromagnetism with the strong and weak nuclear forces
(at almost impossibly high temperatures), despite the differences in their
respective strengths, and provides a neat theoretical framework for the big,
noisy "family" of subatomic particles.
But there is a gaping hole. The standard model doesn't include the
gravitational force. That's why Jove, the physicist in Jeanette Winterson's
novel, Gut Symmetries, calls the Standard Model the "Flying
Tarpaulin" -- it's "big, ugly, useful, covers what you want and
ignores gravity.” Superstring theory aims to plug that hole.
Pulling Strings
According to string theorists, there are the three full-sized spatial
dimensions we experience every day, one dimension of time, and six extra
dimensions crumpled up at the Planck scale like itty-bitty wads of paper. As
tiny as these dimensions are, strings -- the most fundamental unit in nature,
vibrating down at the Planck scale -- are even smaller.
###
The geometric shape of those extra dimensions helps determine the
resonant patterns of string vibration. Those vibrating patterns in turn
determine the kind of elementary particles that are formed, and generate the
physical forces we observe around us, in much the same way that vibrating
fields of electricity and magnetism give rise to the entire spectrum of light,
or vibrating strings can produce different musical notes on a violin.
All matter (and all forces) are composed of these vibrations --
including gravity. And one of the ways in which strings can vibrate corresponds
to a particle that mediates gravity.
Voila! General relativity has now been quantized. And that means
string theory could be used to explore the infinitely tiny point of our
universe's birth (or, for that matter, the singularity that lies at the center
of a black hole).
Shattered Symmetry
There's one more wrinkle, and that's this whole business of extra
dimensions, when our world as we currently experience it has only three.
Physicists have hammered out a pretty convincing hypothetical scenario for how
this might have come about.
Before the Big Bang, the cosmos was a perfectly symmetrical
nine-dimensional universe (or ten, if you add in the dimension of time) with
all four fundamental forces unified at unimaginably high temperatures. But this
universe was highly unstable and cracked in two, sending an immense shock wave
reverberating through the embryonic cosmos.
The result was two separate space-times: the unfurled three-dimensional
one that we inhabit, and a six-dimensional one that contracted as violently as
ours expanded, shrinking into a tiny Planckian ball. As our universe expanded
and cooled, the four forces split off one by one, beginning with gravity.
Everything we see around us today is a mere shard of the original shattered
nine-dimensional universe.
Physicists who espouse this view aren't sure why it happened, but they
suspect it might be due to the incredible tension and high energy required to
maintain a supersymmetric state, which could render it inherently unstable.
Imagine that you are trying to making the bed on laundry day, but the
bed sheet has shrunk slightly in the wash. You manage to get it to fit around
all four corners of the bed, but the sheet is stretched so tightly that it just
won't stay in place.
There is too much strain on the fabric, so one corner inevitably pops
loose, causing the bed sheet to curl up in that spot. Sure, you can force that
corner back into place, but again, the strain will prove to be too much and
another corner will pop.
Like the bed sheet, the original ten-dimensional fabric of space-time
was stretched tight in a supersymmetric state. But the tension became too
great, and space-time cracked in two. One part curled up into a tight little
ball, while the aftershock from the cataclysmic cosmic cracking caused the
other part to expand outward rapidly, a period known as inflation. This became
our visible universe.
Birthing Pains
That's what the Japanese simulation shows: the universe had nine
spatial dimensions at its birth, but only three of them experienced expansion.
It's the first practical demonstration of how a three-dimensional universe
emerges from nine-dimensional space, providing strong support in favor of the
theory's validity.
What is the mechanism by which this happened? For a ten-dimensional
universe, there are millions of ways for supersymmetry to break. So is there
something special about three spatial dimensions that causes that configuration
to be favored in our own universe? The new simulations may help shed some light
on why this symmetry breaking might have unfolded the way it did.
Jun Nishimura (KEK), Asato Tsuchiya (Shizuoka
University ), and Sang-Woo Kim (Osaka University
For very complicated technical reasons, the connection between the
original IKKT matrix model and the real world was, well, a bit vague, mostly
because (a) it assumes weak interactions, when in fact the interactions between
strings are quite strong; and (b) the variable of time in the calculations
wasn't treated as "real" in a mathematical sense. These new
simulations assume strong interactions, and treat time as a real variable.
So the takeaway message is that string theorists now have a useful tool
for analyzing superstring theory's predictions with computer simulations,
shedding light on such knotty problems as inflation, dark matter, and the
accelerating expansion of the universe. And it also explains why our universe
looks the way it does.
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