Cosmic structure explained without dark matter?

Sam Wormley wrote:
Cosmic structure explained without dark matter?
http://physicsweb.org/articles/news/10/12/11/1

18 December 2006

An alternative to Einstein's theory of general relativity called
"TeVeS" could describe the formation of cosmic structure without
requiring the existence of dark matter, say physicists in the US (Phys.
Rev. Lett. 97 2006).

Cosmologists have long puzzled over the origin of structure in the
universe. In whichever direction of the sky you look, there is a
hierarchy of stars, galaxies and galaxy clusters. Yet intuitively, the
Big Bang should have created a uniform spread of matter and left the
universe a rather uninteresting place.

The breakthrough came with the discovery of temperature fluctuations in
the cosmic microwave background radiation, formed some 380 000 years
after the Big Bang, which supported the idea that the early universe
was a plasma filled with tiny fluctuations in density. The denser areas
caused the matter to "clump" together, providing the seeds for the
cosmic structure we see today.

Unfortunately, our theory of gravitation -- Einstein's theory of
general relativity -- cannot account for the extent of clumping
without invoking the right amount of a mysterious substance called
"dark matter". Originally introduced in the 1930s to explain anomalous
galaxy dynamics, dark matter (which cosmologists think could make up to
95% of matter in the universe) is gravitationally attractive yet does
not couple to light. But crucially it can describe how the initial
plasma fluctuations were sustained for long enough to allow large
structures to form -- on its own, general relativity attests that
they simply petered out. Even though dark matter has never been
observed, the majority of physicists now believe that general
relativity combined with dark matter is the only satisfactory
explanation for the universe's large-scale structure.

However, in recent years there has been growing support for alternative
theories of gravitation to general relativity that do away with the
need for dark matter altogether. One of these, devised by Jacob
Bekenstein in 2004 at the Hebrew University of Jerusalem, uses vector
and scalar fields in addition to the tensor used in relativity, hence
the name "TeVeS" (Tensor Vector Scalar). TeVeS has already been shown
to explain galaxy dynamics without the need for dark matter. But now,
building upon the numerical studies by Pedro Ferreira and colleagues
performed earlier this year, Scott Dodelson and Michele Liguori from
Fermilab in the US have confirmed that TeVeS can also provide such
sustained plasma fluctuations. (See figu "Powering galaxy
formation".)

In particular, the pair found that it is TeVeS's additional vector
field that provides the "extra" gravitation on large mass scales,
meaning that denser regions of the primordial plasma could have
accreted matter much faster than general relativity alone (without dark
matter) predicts.

"Their elegant calculation brings us closer to understanding why a
modified theory of gravity may be a viable alternative to dark matter,"
Ferreira told Physics Web. "The presence of the cosmic [vector] field
-- akin to an aether -- drives the growth of the structure,
making this theory compatible with observations of the cosmic microwave
background and the distribution of galaxies."


Sam posting a reference to an alternative theory? Has Hell frozen over
yet?

Double-A

"The presence of the.. field --
akin to an aether -- drives the growth of
the structure..."

"Akin to an aether"? Oh horrors no!
(-: oc

Double-A Seems the macro realm has its clumps. It is not homogenized. it
clumps are seen thesame in all direction,but still as clumps. Random
fluctuations (YES) Uncertainty principle can apply (YES) Has motion,and
gravity a lot to do to answer this (YES) I will post why this condition
has to be the way its is(reality) I'll just say if the universe of
spacetime was completely "smooth" with no Quantum jumps. No time laps
and light stopping and going or even changing its seed by less than a
trillionth of a second. All this would destroy universes before they
could create a structure for universes. This is my today's theory that
is "Universes have to begin at the beginning "right" Bert

"Sam Wormley" wrote:

Let the data be the final arbiter!


Well done Sam.

G=EMC^2 Glazier wrote:
Double-A Seems the macro realm has its clumps. It is not homogenized. it
clumps are seen thesame in all direction,but still as clumps.


You mean like the clumps in milk that's past the expiration date?


Random
fluctuations (YES) Uncertainty principle can apply (YES) Has motion,and
gravity a lot to do to answer this (YES) I will post why this condition
has to be the way its is(reality) I'll just say if the universe of
spacetime was completely "smooth" with no Quantum jumps. No time laps
and light stopping and going or even changing its seed by less than a
trillionth of a second. All this would destroy universes before they
could create a structure for universes. This is my today's theory that
is "Universes have to begin at the beginning "right" Bert


Maybe those that don't begin at the beginning "right" become failed
universes!

Double-A

Double-A Perhaps for nature to create the very first original universe
there were a lot of failures. It could have taken trillions and
trillions of failures for nature to create one that was "right" Once
this was achieved and the cosmos had its mother universe,all
mini-universes became possible,and here were are to talk about it Bert