Are Large Extra Dimensions still acceptable?

[GRQC]

Sol2, your posts have nothing to do with large extra dimensions. I don't understand the point you're trying to make. There are lots of theories which require extra dimensions. That's not new. Large extra dimensions are a very specific area.

Are you confusing LED and LQG?

 

[sol2]

Would we have not considered one end of the dimension and its strength in terms of energy, and not have considered the weak measure of gravity, as the other?

Are you confusing LED and LQG?

I am looking geometrical consistancy in the quantum world that connects to the world we understand around us. That one would call it discrete and one continuos , is part and parcel of their own distinctions. But they all began from the attempt to describe what?

it turns out that within string theory ... there is actually an identification, we believe, between the very tiny and the very huge. So it turns out that if you, for instance, take a dimension - imagine its in a circle, imagine its really huge - and then you make it smaller and smaller and smaller, the equations tell us that if you make it smaller than a certain length (its about 10-33 centimeters, the so called 'Planck Length') ... its exactly identical, from the point of view of physical properties, as making the circle larger. So you're trying to squeeze it smaller, but actually in reality your efforts are being turned around by the theory and you're actually making the dimension larger. So in some sense, if you try to squeeze it all the way down to zero size, it would be the same as making it infinitely big. ... (CSPAN Archives Videotape #125054)

I am looking for something more. Where each of these theories began. They had to all start from a fundamental principal? What is "that" which joins them all? Then these theories branch out into their respective differences.

Building that basis is important for me, and really, that the dimension would have some sort of scale was Quite intriguing once you considered the interaction of the graviton and the photon.

But as was pointed out there are respective differences where this would work with LQG and not with strings becuase of its continuous nature. But in respect of dimension, and what that graviton represents, how the heck could we have enter into the realm of GR and QM without considering a way in which to satisfy what this dimension could mean.

To strings it was specific that the approach of glast was not functionable to the Lorentz invariance as a exact symmetry in nature to strings?

Look deep, Deep into Nature, and Then You will Understand Everything Better--Albert Einstein

 

[Quantum_gravity]

Not sure why you would ask this in this section of PF since there clearly is a String/Brane/etc section.

The Arkani-Hamed conclusion that one can detect deviation to Newtonian law of gravity at the millimeter scale is having some problems. There have been TWO (count 'em) experimental measurements within the past 3 years that have measured G up to sub-millimeter scale, and have found no such deviations.[1,2]

So draw your own conclusions from that.

Zz.

[1] C.D. Hoyle et al., PRL v.86, p.1418 (2001).
[2] J.C. Long et al., Nature v.421, p.922 (2003).

Actually, there have been several experiments, including mine, that have set limits on compactified extra dimensions.
Fir a list of most of the current experiments, check out my paper at:
http://www.phys.lsu.edu/mog/mog22/node9.html

I have a question about your avitar. It is hard to see, but is it an ARPES scan of bi-layer splitting in a cuperate?

Regards,
Mike

 

[sol2]

http://www.nature.com/nature/journal/v411/n6841/images/411986af.0.jpg

Eric Adelberger and Blayne Heckel of the University of Washington in Seattle are no strangers to difficult gravity experiments. In the 1980s, they led one of a number of groups that investigated the existence of a postulated fifth force, which would show up as a gravitational anomaly over distances of up to 100 metres. Their findings helped to kill the idea.

http://www.nature.com/nature/journal/v411/n6841/box/411986a0_bx1.html

http://www.physics.harvard.edu/nimaphoto.jpg[/URL]

[QUOTE][B]What got you started on the research in large extra dimensions, for which you're so highly cited? [/B]

Well, I had just obtained my degree from UC Berkeley and had just started my post-doc at the Stanford Linear Accelerator Center (SLAC). As a Ph.D. student, I had been working on what was a mature field. It was supersymmetry at low energies: the point was that everyone expects some sort of new physics to come in at a distance around 10-17 centimeters, and what we can see at accelerators today goes up to 10-16 centimeters. For 20 years, the dominant view has been that a new symmetry of nature will be revealed, called supersymmetry, and it will manifest itself in a variety of new particles with very distinctive properties. But this framework has been around for 20 years, and it may still very well be right, and it's what I spent my time exploring as a graduate student, but by the time I got to my post-doc I was definitely getting restless, wondering if there was some completely different framework for what might be happening at the 10-17 centimeter scale.

When I arrived at SLAC, I immediately started talking to Savas Dimopoulos, who's one of the people responsible for inventing this old paradigm of supersymmetry. We quickly realized we were both on the same page as far as wanting to think about something completely different. Gia Dvali was also interested in thinking that way. So the three of us started thinking about whether we could make sense of some older ideas about extra dimensions that might be large compared with what people normally thought about extra dimensions.

[url]http://www.esi-topics.com/brane/interviews/DrNimaArkani-Hamed.html[/url]

[/QUOTE]

[PLAIN]http://www.sciencewatch.com/may-june2001/savas-dimopoulos-big.jpg[/URL]


[QUOTE]In 1981 Savas Dimopoulos of Stanford University and Howard Georgi of Harvard University proposed the supersymmetric extension to the standard model. Revolutionary at the time, it is now accepted by many physicists. Dimopoulos has been strongly driven in his research by a desire to understand what lies beyond the standard model. His contributions have included work on grand unified theories of baryogenesis, which would provide an explanation of the origin of matter. Jointly with Stanford colleague Nima Arkani-Hamed and Gia Dvali of ICTP, Trieste, Italy, he has proposed an audacious solution to the problem of explaining the weakness of the gravitational force. [B]The proposal invokes new large dimensions accessible to the graviton. Among the extraordinary implications of this thinking is the notion that our entire universe is a single point in space of extra dimensions, and is but one of innumerable parallel universes.[/B] Thanks to this work, Dimopoulos has recently been a mainstay of the Physics Top Ten—one of the trio's papers on this subject has ranked among physics's most cited for more than a year (see table on next page, paper #3).

[PLAIN]http://www.sciencewatch.com/may-june2001/sw_may-june2001_page3.htm[/URL]
[/QUOTE]

 

[sol2]

http://www.nature.com/nature/journal/v411/n6841/images/411986af.0.jpg

http://physics.nyu.edu/people/dvali.georgi.jpg

http://www.physics.harvard.edu/nimaphoto.jpg[/URL]



[PLAIN]http://www.sciencewatch.com/may-june2001/savas-dimopoulos-big.jpg[/URL][/QUOTE]

When you see them together you learn to [PLAIN]http://wc0.worldcrossing.com/WebX?14@66.eO6PctewETX.5@.1ddf4a5f/123[/URL] where I am headed



[QUOTE=sol2][URL=https://www.physicsforums.com/showpost.php?p=303482&postcount=17][So I'll finish this post to prepare for others to follow. If you do not follow this history, you will never understand what Nima Arkani-Hamed, Sava Dimopoulos, and Gia Dvali been doing with extra dimensions. There is a conceptual feature here that I have spoken too in regards to gravity that few understand.[/URL] [/QUOTE]



I resurrected this post for those who had a hard time understanding what was going on here in terms of the what the measures mean and considered ,although many links were supplied for consideration, was something taken from this discussion?