http://motls.blogspot.com/2006/07/from-strings-to-lhc.html

Dear Lumos,

Suppose string theory is correct, and gravity mediated by spin 2 gauge bosons (exchange radiation between masses, since masses are the units of gravitational charge).

Assuming this, would the exchange radiation (gravitons, gravity gauge bosons, vector bosons, whatever you call it) be redshifted by cosmological expansion over large distances?

If so this would weaken gravity over immense distances, explaining why gravity doesn't slow the recession of distant supernovae. Hence the need to invent a small positive cosmological constant (and a massive amount of "dark energy" to explain that cosmological constant) disappears.

Also, the disagreement between this "dark energy observation" and the vacuum energy, as calculated by supersymmetry predictions, will disappear.

Suppose you were confronted by the argument above, would you be able to put a note on arxiv.org about it?

Kind regards,
anon
anon Homepage 07.29.06 - 12:07 pm #


Dear anon,

I don't want to discourage you much but what you wrote here is far from an acceptable paper on arxiv.org. Moreover I don't quite understand how could I publish YOUR ideas.

Indeed, the rough idea that something is drastically changed at cosmological distances and forces become weaker has been formulated by many people.

A more important point at this moment is that according to the standard theories we love and trust today, the very long distance behavior of the forces IS given by the well-known power laws and there are no easy ways to make these power laws break down.

Physical gravitons and photons get red shifted by expansion, but the force they cause right now is always given by the same laws, regardless of the cosmological history.

However, I sympathize that the 1/r^2 becomes much weaker at very long distances, which could eventually even explain the cosmological data - and Hubble = 1.0/AgeOfTheUniverse - without dark energy. But you need to create a theory that is also consistent with other things we know which is not trivial.

Best
Lubos
Luboš Motl Homepage 07.30.06 - 4:39 am #

Dear Lumos,

Thanks for your remarks, but can you tell me if anyone has formulated this gauge boson redshift mechanism before? I'm not interested in ad hoc speculative MOND stuff that anyone can sketch on the back of an envelope (pet theories), this is a mechanism which is true. Redshift is confirmed [> http://www.astro.ucla.edu/~wright/tiredlit.htm. There NO other explanations of redshift that work other tha recession and big bang. Light isn't being coloured red or scattered, it is being shifted by the same amount at all frequencies which cannot result from scattering or filtering which are frequency dependent effects; notice that the most redshifted big bang radiation is the cosmic background radiation emitted when ions and electrons combined to form hydrogen molecules at 300,000 years after BB, and this radiation is the most PERFECT BLACK BODY SPECTRUM ever observed in physics! No evidence that redshift is due to red-colouring or scattering or any other speculative, false drivel from people like Catt and Arp. The facts are that redshift is proved to occur to light due to motion of the source away from you (recession) and all alternatives are UNPROVED speculation], and all the evidence points to forces being mediated by exchange radiation.

The earth and moon are not receding from one another significantly. Hence redshift is not a contributor to inverse square law in most cases. Newton showed that gravity between earth and moon is given by inverse square law, see http://www.math.columbia.edu/~woit/wordpress/?p=432#comment-13697, where redshift of light and gauge bosons between the two masses is NOT involved!

Redshift of the gravitons is significant on cosmological distance scales. It is easy to calculate the precise effect due to redshift: the proportionate loss of energy of photons and gravitons at any distance would reduce gravity constant G by the same factor.

I plot the predicted recession curve allowing for the reduced G involved in gravity retardation effects on receding galaxies at any given distance from us. If you want I'll draft a paper with the equations and some graphs, comparing the redshift mechanism to the ad hoc Lambda-CDM speculation, and to the actual data: http://www.phys.lsu.edu/GRBHD/ . I can provide a reference to a publication of this dated Oct96, preceding the current Lambda-CDM theory and also preceding Perlmutter's discovery that there is no observable gravitational retardation (the so called evidence for a small positive CC and dark energy; which is actually confirmation of the redshift mechanism).

This would wipe out all the paradoxes of a small positive CC, leaving a slate clean for new ideas.

Best wishes,
anon

anon Homepage 07.30.06 - 11:46 am #

Isn't it the case that what is actually observed is the acceleration of cosmological expansion. In which case, even if gravity were redshifted to zero at cosmological distance scales, one would still need to introduce a small but non-zero vacuum energy to explain the acceleration, right?

Chris 07.30.06 - 7:30 pm #

Dear anon,

Your line of thinking vaguely reminds me of a gravitational model presented by Gia Dvali at the Space Telescope Science Institute (12/4). He essentially proposes the idea that dark energy is actually a modification of gravity at long distances. This model embraces the notion that gravity has an attractive side as well as a repulsive side. {a lot more speculative, non factual, non predictive, non-scientific ad hoc MOND drivel deleted} ... Dvali has had lunar thoughts ...

Best,
Cynthia 07.31.06 - 10:04 am #

"Isn't it the case that what is actually observed is the acceleration of cosmological expansion. In which case, even if gravity [graviton radiation] were redshifted to zero at cosmological distance scales, one would still need to introduce a small but non-zero vacuum energy to explain the acceleration, right?" - Chris

Chris, what acceleration??? The acceleration I'm referring to is being postulated to counteract gravity, which slows expansion if you ignore redshift of gravitons.

See Nobel Laureate Phil Anderson's comment http://cosmicvariance.com/2006/01/03/danger-phil-anderson/#comment-10901 on the discussion http://cosmicvariance.com/2006/01/03/danger-phil-anderson:

"the flat universe is just not decelerating, it isn’t really accelerating ... there’s a bit of the 'phlogiston fallacy' here, one thinks if one can name Dark Energy or the Inflaton one knows something about it. And yes, inflation predicts flatness, and I even conditionally accept inflation, but how does the crucial piece Dark Energy follow from inflation?–don’t kid me, you have no idea."

In a sense of course the universe is accelerating in a completely different context (the regular Hubble effect).

If you assume graviton exchange works simply by imparting momentum, then this be a dark energy driving the Hubble expansion, but that is entirely diferent to the pseudo-acceleration in the Lambda-CDM model of mainstream cosmology (which is horses***).

The REGULAR Hubble recession formula is: recession velocity = Hubble constant x distance.

But this ignores Minkowshi's spacetime, where distance = c x time.

Hence recession velocity rises linearly with time of observed stars in the past, not merely distance of the stars.

Any variatio of velocity with respect to time is acceleration a = v/t ~ c/(1/H) ~ cH ~ 10^-10 ms^-2, so the mass of universe m is subject to outward force of F = ma ~ 10^43 Newtons. Since Yang-Mills exchange radiation drives gravity, it probably does this by simply delivering momentum [and causing the general relativity contraction the same way, ie, the earth's radius is contracted by GM/(3c^2) = 1.5 millimetres according to the contraction in general relativity, which resembles an ideal fluid frictionless compression by gravitons which distinguishes general relativity from Newtonian dynamics]. There is no evidence that the dynamics are far more complicated than radiation exchange.

Because the expansion of the universe is then like a balloon inflating under molecule collisions, the vacuum energy is then easy to calculate: it is equivalent to the total kinetic energy of all the receding matter in the universe.

This is IMMENSELY larger than the energy implied by the small positive CC Lambda-CDM acceleration "dark energy". It is FAR closer to supersymmetry predictions than the Lambda-CDM s***.

Best wishes,
anon
anon Homepage 07.31.06 - 3:45 pm #