Friday, 20 September 2013

Faster than Light?


John Walker · September 23, 2011 at 12:03pm 

Ref Ricochet Blog


The King Prawn started a conversation about this earlier, but it attracted only six comments and didn't make it to the Main Feed, so let me try again.  Here is my idiosyncratic take on the CERN announcement that results from CERN's OPERA experiment provide evidence that neutrinos propagate faster than the speed of light.
Since the 1990s there have been tantalising hints that the mass of the neutrino might beimaginary based upon studies of the endpoint of the energy spectrum of the decay of tritium.  Here is the 1998 paper which first caused my ears to perk up about this.
Now, if the mass of a particle is imaginary, Einstein's equations predict that it is a “tachyon”—a particle which always travels faster than light and cannot travel slower, just as a real mass particle cannot ever reach or exceed the speed of light.  There is nothing in this which implies “Einstein was wrong”, just that at the time he wrote down his equations in 1905 nobody imagined there would be particles with imaginary mass.  If neutrinos have a very small imaginary mass, then it's perfectly consistent with special relativity that they travel slightly faster than light.
That said, I think it will be quite a while before this result is generally accepted.  For the results to mean anything at all, you have to assume that they've accurately measured the location of the source and target of the neutrinos to better than 60 feet (as light travels about one foot per nanosecond) over a distance of around 500 miles, with both the source and target underground.  A very small surveying error could null out the reported effect.
The press release from CERN and the preprint describing the work were both very cautious and simply presented the results as (paraphrasing) “Here's what we've seen, and we invite others to look over our shoulders and see if we've made a mistake and other labs to see if they can reproduce the results in their own experiments”.  This is precisely what they should have said, and any blowing of this out of proportion is due to the media, not the experimenters or the labs for whom they work.
If this is confirmed (which will probably take years, as experiments in the U.S. and Japan will have to be reconfigured to make similar measurements), the consequences will behuge, at least from a theoretical standpoint.  If the neutrino is a tachyon, it means you can (in principle) build a “tachyonic antitelephone” which allows sending signals into one's own past light cone and thus potentially violate causality.  For example, imagine sending a signal from a sensor which has detected a superluminal neutrino via another neutrino beam to the source which, if detected, causes the source to cancel sending the original neutrino.  This signal, in the reference frame of the source, will arrive before the original neutrino was sent and cause it not to be sent.  Then where did the neutrino which started the whole process originate?

Comments:



Cas Balicki
Joined
Jun '10
Cas Balicki
Thanks for the post. 

The King Prawn
Joined
Dec '10
The King Prawn
Is imaginary mass the same thing as no mass? Is it mass saved or created?

Casey
Joined
Mar '11
Casey
Is there a For Dummies book to get me started on this stuff?  I'm fascinated but stupid.

John Walker
Joined
Oct '10
John Walker
Casey: Is there a For Dummies book to get me started on this stuff?  I'm fascinated but stupid. · Sep 24 at 7:05am
It isn't a For Dummies book, but a beautifully-written introduction to particle physics and its foundations is Longing for the Harmonies by Frank Wilczek and his wife Betsy Devine.  It was published in 1987, but since there have been relatively few discoveries in the field since then, it's not outdated.  The book is accessible to the intelligent layman.  Wilczek won the Nobel Prize in Physics in 2004.

Casey
Joined
Mar '11
Casey
intelligent layman
You flatter me  ;)   Thanks

Jack Sarfatti
Joined
Mar '11
Jack Sarfatti
Consensus at the moment is that the experiment has a systematic error - probably something to do with the GPS. Real electron-positrion pairs from the Cherenkov effect not seen.

Jack Sarfatti
Joined
Mar '11
Jack Sarfatti
imaginary mass has an "i" in front of the m where i^2 = -1.
Einstein's special relativity has a "mass shell" equation for the propagation of real particles
E^2 = (pc)^2 + (mc^2)^2
m is called rest mass
ordinary particles have real m
The hypothetical tachyon mass shell equation
E^2 = (pc)^2 - (mc^2)^2
The "group speed" of a real particle is dE/dp
2EdE/dp = 2pc^2
dE/dp = pc^2/E = pc^2/[(pc)^2 - (mc^2)^2]^1/2  for a tachyon
Therefore, a zero energy tachyon has infinite group speed.
However, there are several reasons why real tachyons almost certainly do not exist in Nature - another story.

Jack Sarfatti
Joined
Mar '11
Jack Sarfatti
Wilczek's newest book "Lightness of Being" is also very good on elementary particle physics.

Midget Faded Rattlesnake
Joined
Aug '10
Midget Faded Rattlesnake
Jack Sarfatti: imaginary mass has an "i" in front of the m where i^2 = -1.
If you don't mind a stupid question from a math major, what does it really mean for mass to happen over the complex numbers?
I use complex numbers for math all the time without a problem, but when it comes to how physicists use them (I was briefly a physics major), I'm still prone to confusion. Are there any books that help with that?

Jack Sarfatti
Joined
Mar '11
Jack Sarfatti
Basically it means the the square of the rest mass of a particle is negative. This affects how the real particle moves in space as the algebra I gave showed in the relation between energy E and linear momentum p. This, however, is only the top of the iceberg because there are virtual particles inside the vacuum as well as real particles outside the vacuum. Get Zee's "Quantum Field Theory in a Nutshell" 2nd edition for a readable account. Virtual particles do not obey the constraint between E, p and m.

Midget Faded Rattlesnake
Joined
Aug '10
Midget Faded Rattlesnake
Weird double-post going backwards in time. Somehow appropriate for this topic, no?
Edited on November 12, 2011 at 11:11am

Midget Faded Rattlesnake
Joined
Aug '10
Midget Faded Rattlesnake
Jack Sarfatti: Basically it means the the square of the rest mass of a particle is negative. This affects how the real particle moves in space as the algebra I gave showed in the relation between energy E and linear momentum p. This, however, is only the top of the iceberg because there are virtual particles inside the vacuum as well as real particles outside the vacuum. Get Zee's "Quantum Field Theory in a Nutshell" 2nd edition for a readable account. Virtual particles do not obey the constraint between E, p and m. · Nov 12 at 10:44am
Thanks!  Look forward to reading -- or at least browsing -- the book. 
I keep hoping that, now that I have a solid foundation in math (which I didn't, when I started as a physics major), I'll someday be able to revisit the math physicists use with much better understanding.

Jack Sarfatti
Joined
Mar '11
Jack Sarfatti
Extending the topic to the current excitement over that other CERN experiment on finding the Higgs.
Edited on December 10, 2011 at 11:42am

Jack Sarfatti
Joined
Mar '11
Jack Sarfatti
Impending discovery of the God Particle
I suggested that Regge trajectory universal slope (1 Gev)^-2  was an Abdus Salam strong Yukawa gravity effect in 1972 or so. Indeed, that's why Salam invited me to Trieste in 1973. In other words hadronic resonances were little black holes in a micro gravity 10^40 that of Newton's macro-gravity. From the dual resonance model to superstrings - the closed connection between tangled strings and black holes was anticipated by me back then.
The issue now at hand is if there is a significant connection between the positive squared mass Higgs God Particle and the negative squared mass Pomeron where the vacuum trajectory intersects the J = 0 M^2 horizontal line on the Regge plots.
http://universe-review.ca/I15-51-Regge1.jpg
http://universe-review.ca/R15-18-string.htm
the relation is indirect of course and there are several intervening fudge factors.

Jack Sarfatti
Joined
Mar '11
Jack Sarfatti
trying to delete unintended duplicates here
Edited on January 27, 2012 at 1:01pm

Jack Sarfatti
Joined
Mar '11
Jack Sarfatti
deleted duplicate
Edited on January 27, 2012 at 1:02pm

Jack Sarfatti
Joined
Mar '11
Jack Sarfatti

On Dec 9, 2011, at 4:04 PM, JACK SARFATTI wrote:

let me rephrase last message in my own simpler notation

the effective quartic c-number vacuum condensate order parameter Psi renormalizable potential is

V = (mass)^2|Psi|^2 + (nonlinearity)|Psi|^4

the J = 0 intercept of the vacuum pomeron Regge trajectory would then be

(mass)^2 < 0

from that one needs to calculate the positive squared mass of the quantized Higgs amplitude vibrations up and down the sides of the Mexican hat potential.

Jack Sarfatti
Joined
Mar '11
Jack Sarfatti
another duplicate I don't know if it's something I am doing or the ricochet software - also no command to delete
Edited on January 27, 2012 at 1:06pm






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