Speed of Light barrier

[Qfwfq]

There seems to be a bit of confusion around here between two different things, having two different meanings: time-reversed causality and "time going the opposite way". The former doesn't mean the latter Paul, it means (loosely) causality going the opposite way of time (which goes "the same" way as usual). If you know what I mean...

 

The stuff about dispersive media and different measuring rods doesn't tell me much about tachyons either. Here's what I think: tachyons exist, sure as hell they do, you can bet on their existence at no risk, but we'll never run fast enough to catch up with'em. Which means you'll never win nor lose your bet, despite it being an otherwise won bet. :naughty:

 

Of course if one doesn't consider new things, nothing new get done. Yes, until new ideas become the norm, they often quite considered unbelievable, unlikely, wrong, etc. It is the road one takes to hone a "new" theory.

Obviously, as long as one considers it the right way till any conflict with observation is sorted out. Even when a conjecture can't be ruled out, that ain't the same as proving it. In any case Linda's point is certainly a good one, relief relief relief...

 

time for instance.. it may very well be just something we consider that exist but has never existed in the first place..

Sounds a little bit like Kant. Well... it depends on what you mean by 'exist', I guess...

[Qfwfq]

Perhaps it is a barrier much like absolute zero.

The two barriers are quite different. Negative temperatures experimentally exhibit the effects that can be anticipated by the equations, which don't even run into trouble such as complex values of observables and whatnot.

 

The violation they cause is that of the entropy rule, which has a statistical basis totally different from that of the causality matter and certainly doesn't cause any paradox. So what if a heat engine could concieveably have a better efficiency than Carnot, Klausis and the rest of that bunch allowed? Big deal, it wouldn't cause problems, it would actually be all the better. Anyway negatemperatures are but a lab curio and I don't know when we'll get practical applications in heat engines. Spin gas is only a subsystem and the negatemperature is a quite formal phenomenon.

[paultrr]

There seems to be a bit of confusion around here between two different things, having two different meanings: time-reversed causality and "time going the opposite way". The former doesn't mean the latter Paul, it means (loosely) causality going the opposite way of time (which goes "the same" way as usual). If you know what I mean...

 

..

 

The above mentioned idea involves no time-reversed causality and "time going backwards at all. Its strickly forward time with the usual atomic processes that are time-reversed like say anti-matter being one exception to that rule. It also involves no real usuable time travel in the classical sence of backwards in time. Forward time travel is something on one level we do everyday of our lives from moment to moment. We can also observe backwards in time as we do with observations of the universe as a whole. Something that cannot be "proved" which is rather a loose term in physics as compared to say math, is simply just a theory without epherical support. Its also commonly seen as the earmark of crackpots to suggest theories that can never be proved either by observation or experiment.

 

Its not much of a safe bet on the issue of tachions to make the prediction or bet they exist. For one, a lot of modern theory also suggests there may be ways at certain energy levels to determine if they exist or not. That means one is actually betting on something that may one day be proved one way or another and not actually something which can never be proved. Also as noted earlier certain modern theories do allow for their existance even if they exist outside of our normal spacetime.

 

Physics is not like math. One can propose a theory. But for the theory to become accepted(Notice the word proved is not used) that theory has to eventually be backed up with observation and duplicated experimental evidence. In math a theory can be self proving which is something that is never allowed in physics. In physics we use the language of math to explain theory. But the only type of proof any theory can have is experimental and observational. All theory is also always subject to further refinement under physics. At one time no one actually strongly questioned Newton's idea on the Aether. After the time of Einstein Newton's idea was rather not accepted anymore. Here is a case where our knowledge eventually displaced what at that time was a seemingly sound theory. The math used by Newton at one time seemed to hold in all cases. But further observation and experiment expanded upon that math. Now the math he used still remains valid even if certain parts of his theory had gaps in them. The math was not wrong in this case. It simply was not the complete picture of what was going on in all situations. Math may be the backbone of physics. But its experimental/observational evidence we really base the proof of anything on and even then we generally never consider something proved beyond a shadow of a doubt.

[Qfwfq]

The above mentioned idea involves no time-reversed causality and "time going backwards at all.

I was talking about the difference between the two things. The confusion doesn't seem to be waning.

 

Its not much of a safe bet on the issue of tachions to make the prediction or bet they exist.

Think I was being serious?

 

Also as noted earlier certain modern theories do allow for their existance even if they exist outside of our normal spacetime.

How could a theory rule out their existence? What is troublesome is interaction with them.

 

Proving the existence of something is a bit different from proving a theory. You use the word several times yourself in the same post.

 

Physics is not like math.

Physics is what I graduated in. So many things are clearer now that, finally, someone points this out to me.

 

At one time no one actually strongly questioned Newton's idea on the Aether.

First time I hear about it being Newton's idea. After the time of Einstein it was rather not necessary anymore. This further to the crushing experimental evidence against it. Even before Michelson and Morley, it was not a seemingly sound theory. It was a hypothesis, and a very tentative patch of one too. Do you think that M&M really believed they would find positive results? I suspect they weren't quite totally convinced they would, simply people didn't know what to think.

[maddog]

To both paultrr & Qfwfq,

 

Do either of you know of the "Ghosts" mentioned within the Bosonic String Theory that was in 26

dimensions ? And why these ghosts were not desired (due to causality problems) ? Were these ghosts in

someway related to Tachyons or particles of a Superluminal nature ?

 

BTW, I thought the notion of Aether was contemprorary of post-Maxwell... Maxwell published his paper

about 1860 or so. I started reading about stuff like Aether just after that. I suppose like Newton, thinking

all waves needed a medium to travel in... It was interesting of that time as physics was as polarized then

as now with M-Theory and LQG (it does or it doesn't exist...)

 

I always desire to have any theory created meet with the crucible of verifiability.

 

Maddog

[Qfwfq]

Do either of you know of the "Ghosts" mentioned within the Bosonic String Theory that was in 26 dimensions ? And why these ghosts were not desired (due to causality problems) ? Were these ghosts in someway related to Tachyons or particles of a Superluminal nature ?

Not specifically that stuff, I see it as just yet another detail dragged into the argument... the whole of RQFT was built up due to problems, including causality ones.

 

BTW, I thought the notion of Aether was contemprorary of post-Maxwell... Maxwell published his paper about 1860 or so. I started reading about stuff like Aether just after that. I suppose like Newton, thinking all waves needed a medium to travel in... It was interesting of that time as physics was as polarized then as now with M-Theory and LQG (it does or it doesn't exist...)

Quite right about post-Maxwell. That's exactly where trouble with the principle of relativity came in. It wasn't so much thinking waves need a medium to travel in; that was a far less troublesome matter. Science always gets "polarized" and that's part of how it progresses... fierce arguments between factions... just like us! :cup:

 

It isn't the "existence" of tachyons I'm arguing against, or that of "something" having a superluminal velocity. According to John Stewart Bell, several things go faster than light, including British Sovereignty. However, the Prince of Wales cannot possibly know that he is already the King of the UK before the news can actually reach him. I renew my offer about the national lottery over here, but I don't know what next week's jackpot will be... I'll let you know... or you can look it up at http://www.sisal.it/giochi/giochi_main/1,1047,giochi_SuperEnalotto_Default,00.html Goodness, it's already higher than it was Wedensday. I've never played it, I don't know much about how it works but apparently it's cumulative and nobody has won a Jackpot 6 for a while. :hyper:

[paultrr]

To both paultrr & Qfwfq,

 

Do either of you know of the "Ghosts" mentioned within the Bosonic String Theory that was in 26

dimensions ? And why these ghosts were not desired (due to causality problems) ? Were these ghosts in

someway related to Tachyons or particles of a Superluminal nature ?

 

BTW, I thought the notion of Aether was contemprorary of post-Maxwell... Maxwell published his paper

about 1860 or so. I started reading about stuff like Aether just after that. I suppose like Newton, thinking

all waves needed a medium to travel in... It was interesting of that time as physics was as polarized then

as now with M-Theory and LQG (it does or it doesn't exist...)

 

I always desire to have any theory created meet with the crucible of verifiability.

 

Maddog

 

Nathan Berkovits’s pure-spinor approach, which is one more recent example involves commuting ghost fields. However, the pure-spinnor fields he proposes do not represent a free field theory, as we tend to term them. He also incoporates with one of these ghost fields a bilocality that does break lorentz invariance. In short this generates a whole set of lorentz breaking operators. There is a reference for the no-ghost theorem, as its sometimes refered to: see: hep-th/0005002 Makoto Natsuume.

 

The Lorentz transformation in special relativity has been generalized to D-dimensions. The requirement of being Lorentz covariant is to ensure that the superstring theory behaves the same in all inertial frames and in most cases these ghost fields do not obey that rule as the above example illustrates somewhat. However, a short glance into most major archives also shows that such subjects as a variable speed of light, lorentz symmetry breaking, etc are not as taboo as once was thought. So some of the thinking here has been changing of late a bit.

 

The problem so far has been finding a consistant way for these superluminal fields to exist without self hyperinflating themselves away in runaway inflation. Another problem is all of these theories are designed in the end run to yield a solution that produces the vacuum state we live in. From all observational evidence at present outside of certain debated early conditions in this universe, lorentz invariance seems to hold which implies if these ghost fields do actually exist outside of the equations they are derived from they all somehow cancel out in this spacetime or brane.

[paultrr]

In generally what everyone is after is a solution that works:

 

1. for any target space dimension,

 

2. for Minkowski signature of the target space,

 

3. without tachyons,

 

4. manifestly ghost -- free (no negative norm states),

 

5. without fixing a worldsheet or target space gauge,

 

6. without (Virasoro) anomalies (zero central charge),

 

7. while preserving manifest target space Poincare invariance and

 

8. without picking up UV divergences.

 

These ghost fields pose a problem on several fronts here: ie UV divergences, Poincare invariance, no tachyons, negative norm states, and Minkowski signature. 26 dimensional theory predicts particles whose masses are imaginary numbers and which never move at less than the speed of light. They all lead to an unstable vacuum state and ghost particles and fields tend to lead to a infinite series of particles and fields. Both cases also break invariance.

[paultrr]

One side question not often asked is what happened to these fields if they are more than a product of the math involved when they superinflated. Its possible, and here I think we have no argument that these fields exist outside our spacetime in what could be termed their own universe as part of the multiverse. Its also possible that during this superinflation they all simply canceled out in which case they would not exist anymore. A third possible solution is these fields may play a part under M-Theory is those extra dimensional reactions. In that case we are dealing with Planck scale or smaller reactions which at the present time while theory can predict them we have little to measure such by. If that was the case, since the universe is composed of many planck scale events the original bet being made would be a correct one even if we cannot measure such at this time. Eventually, such would hopefully become testable one day.

 

There are different versions of theory being utilized and the different versions do not always make the same predictions. Some versions do not make the prediction of either FTL states or Ghost fields. Those theories if they where ever experimentally shown to be the valid path would by the math of the theory alone rule out such states. However, the versions that do predict such if ever experimentally shown to be valid would by the math involved rather constitute an acceptance of such states as valid.

 

On a personal level I do believe such states are valid. So don't anyone get me wrong there. However, with the state of our present theory I'd be wrong if I did not mention the fact that such states are considered one of the first sign something is amiss in our theories. Generally speaking, by current experimental and observational evidence we have no "proof" to use that term somewhat that lorentz invariance is ever really broken in our spacetime. Most of the M-Theory based theories where FTL/Ghost states show up also predict it should be broken. That is at present where the whole debate stands. Its also true our observations/experiments at the present are limited somewhat.

 

From every article at the time M&M fully expected to discover an Aether drift. One member tried several times after the original experiment to detect such under different ways. Lorentz himself original produced his equations as an answer to how there could be an aether and one still get a null result. These guys fully believed Newton was right about the aether at that time. Any record about those experiments that one can find online or in books backs that fact up as historic record. They all thought Newton was correct untill the time of Einstein himself. Which brings up a point sometimes overlooked that Lorentz formula is actually at is origin a modification itself to Newtonian worldview. Einstein's insight was he saw that if one cannot actually measure something or properly discribe such then why have it in the first place. Call the aether of Newton the original ghost field in the proper sence of the word.

 

Another issue worth mentioning is Maxwell's original EM theory incoporated the aether into it. The equations we all use now where as many who still cling to the aether concept tend to bring up modified by Oliver Heaviside(1850-1925). He developed techniques for applying Laplace transforms to the solution of differential equations. In addition, he reformulated Maxwell's field equations in terms of electric and magnetic forces and energy flux. His ideas along with Heinrich Hertz's lead to the real birth of modern field theory. One reference of this is: Heaviside, O. Electrical Papers, 2 vols. New York: Chelsea, 1970.

 

On a personal level and some here may be old enough to remember this I can still remember growing up way after the time of Einstein and some texts still refered to the Aether, even electronics texts. Also under that issue, going back to Einstein's insight you might call him one of the first modern scienetists who tended to reject something simply because one cannot measure or observe it which is why in general lots of people have problems with FTL particles. Its also in Einstein's own writtings that prior to a point he too had believed in the Aether.

 

Who's right in all this debate only time will tell. However, given that time could be a long term expance saying we will never prove things one way or another may not be the safe bet one would assume it to be. There is an old saying about assumption I will not repeat here. But it can and does tend to in the end fit the situation.

[maddog]

It seems the need for a website as this is simply answer questions only breed more

questions. :hyper:

 

paultrr,

 

1. So would you explain in physics terms what is the significance of having negative

normed states. I understand the mathematical significance. I am having trouble seeing

the flaw in the physics.

 

2. What are "zero central charge" ?

 

3. What do you mean by "broken lorentz invariance".

 

4. Are you saying that Newton mentioned of some default medium for light in his

Principia ?

 

Maddog

[maddog]

These ghost fields pose a problem on several fronts here: ie UV divergences, Poincare invariance, no tachyons, negative norm states, and Minkowski signature. 26 dimensional theory predicts particles whose masses are imaginary numbers and which never move at less than the speed of light. They all lead to an unstable vacuum state and ghost particles and fields tend to lead to a infinite series of particles and fields. Both cases also break invariance.

Having so Tachyon fields never go slower than light does seem to violate Lorentz

Invariance to me. I admit I have done these calculations somewhat casually.

 

I might be missing something. Could you break it down why Lorentz Invariance is

violated as long as Tachyon (fields or particles) never go slower than light and no

direct method of interaction between Tachyon and Tardyon particles or fields.

 

Maddog

[paultrr]

Such a fundamental variation in the speed of light within our spacetime, say different for photons of different energies, would violate Lorentz invariance, the basic principle of the special theory of relativity. Basically, the idea is that in all reference frames the rods we use for measurment remain the same. More simply put, real equivalence of all inertial frames for the description of the physical laws involved. Processes that violate such would be observed as say photons of one energy having one speed while those of another have another speedUGhost fields). One thing Lorentz Invariance gives us is independence of the apparent average two way speed of light with respect to any direction of space and with respect to the speed v. Tachyon particles tend to violate in our spacetime the fundamental idea of C being constant in the vacuum.

 

In external or alternative spacetimes where the vacuum state is different this is not true and these type of particles would simply appear tachyonlike when one trys to compare their frame to ours. A well known example of an altered vacuum state is that found in Cashmir experiments. This type of field by theory has a lower average energy than the normal vacuum external to it. While the space being measure at the present is too small to decern a velocity difference theory in general says that such a vacuum state should have a higher local velocity of light because of the energy difference. However, lets say we could measure such differences. To our frame photons moving there would seem to be faster than light. But, in their frame they never exceed the local velocity of light in that medium. Another words Lorentz Invariance is preserved.

 

One thing that matters here is Einstein's full equation spell out why C is the way it is as do formulas we use in electronics also. As such its only with a certain state of the vacuum that C remains constant. When conditions are altered C for a local medium can be changed. But such changes do not violate relativity at all because you are not dealing with the same medium in both frames. One alternative to all the Ghost fields and tachyon particles is the idea of more than one frame of reference(Multiverse ideas). Here if the frames are different then all these odd fields and particles may simply act like they do because the measuring rods have been shifted in their frame. In our frame they appear to violate everything. But in their frame they do not, nor do they do so once the frame differences are known.

[paultrr]

One other thing. In our vacuum such FTL particles should have a detectable radiation signature. No signature like this has ever been detected and it has been searched for before. So its more an issue of missing observational and experimental evidence for them. If these same particles exist outside our spacetime say in another frame of reference then there is no real violation problem involved. The general thought at present is either these odd fields and particles are simply mathamatical artifacts or they do exist in an alternative frame of reference.

 

The idea behind some of the VSL cosmology models is more akin to differences in vacuum conditions(Past to present) than real outright violations of Lorentz Invariance. But here not all of these models are based upon Brane theory either were the problem really tends to show up. Yes, there are mainline people who support VSL modeling. One example believe it or not is Lee Smolin and some of his closer friends. Hawking while supporting M-Theory ideas tends to not support VSL. I have tended myself to support this type of cosmology model. However, with present evidence we have if C has varied in the history we can directly observe it is by only a very small amount. Another words its just as safe to assume C remains constant.

[maddog]

I read the book "Faster the Speed of Light". It was very informative on his Cosmology.

By reading it, I can really see how it could rival Inflation Theory. I have also not heard

to date of anyone finding Cherenkov Radiation as would be expected for Tachyons. Now

that I know Ghost fields are, I going to read more up on them. Thanks... :Alien:

 

Maddog

[Qfwfq]

I certainly remember texts, especially electronics texts, referring to the ether. It is still used in a figurative sense and this is common to many things which, although not considered correct, can be quite handy for some purpouses. The same goes for frequent use of Newton's mechanics rather than Einstein-Minkowski-Lorentz. Post Einstein talk of the ether is meant as a figure of speach.

 

What people at the time of Maxwell, M&M and Lorentz were truly convinced of was that something... something, must be found to save the principle of relativity. Any talk of the ether was meant as a model to work on and so were the formulae proposed by Lorentz. The very fact that these were viewed as an unsatisfactory solution to the problem, a mere patch over the tear, is what led people to strive for a better solution. This does not go toward showing that people seriously believe in ether as being a physical reality; actually they were making it more of a "whether or not". If Einstein believed in it before a certain time, it sure wasn't then that he strove to find a better solution.

 

Ether was but one example of a model in the history of electromagnetism, a friend of mine that graduated in the history branch of physics told me that, while researching for her grad thesis, she was absolutly astounded by the imaginative models discussed by those that sorted out electromagnetism. Much the same can be said for modern research into nuclear and particle physics, not to mention cosmology. Models are not something the researcher believes or disbelieves in, they are just a tool for phenomenology. You reason "as if" and you work out the consequences, to see how poorly or how well they compare with observation.

 

As for putting it in terms of "Newton being right about the ether", I find this much in contradiction with the fact that Newton based his dynamics on the principle of relativity, a fact which could hardly be denied. For one thing, back in the 16 hundreds, Newton could not have had clear enough ideas, about a few things, to know whether or not a medium for light, distinct from air, needed to be hypothesised. Actually, Newton was more inclined toward the corpuscular explanation of light, in disagreement with Hooke and Huygens. Looking up to cross-check what you say, I easlily and quickly found that his discussion of ether came in the early 17 hundreds but not concerning light (even less "electromagnetic waves"). It followed from being challenged to explain his gravitational attraction without resort to action at a distance, so much loathed by many. As Newton postulated it, ether would have consisted of particles having very strong repulsive forces, but of a very short range. Nothing in violation of Galileo's principle of relativity. It was Maxwell's equations, with that naughty little c in them, that caused all the fuss.

Who's right in all this debate only time will tell. However, given that time could be a long term expance saying we will never prove things one way or another may not be the safe bet one would assume it to be. There is an old saying about assumption I will not repeat here. But it can and does tend to in the end fit the situation.

Are you referring here to some assumption that I have made? Point out which ones, so long as you mean ones that I was making seriously. I don't even see it as a matter of who's right in this debate and I'm afraid I won't have enough time to continue such a debate much.

 

A great example of your words is the time when many were so taken with Newton's mechanics that they couldn't believe there was any chance of Newton being wrong. Before Einstein, that is. We all know this but it is also clear that Einstein did not make Newton so fundamentally wrong. Interaction with tachyons, otoh, would mean either of two things. One, Einstein is wrong in a very basic and fundamental way or, two I can still hope to find a sure fire way of winning jackpot 6 which, btw, is still above €47 million. Unless you can find some way of matching things up.

 

I don't see why a gradual variation of c through cosmic history must necessarily be a causality problem. Neither do I see why tachyons should cause Cherenkov light in the vacuum, unless they actually are able to interact with photons but that would have effects more severe than Cherenkov.

 

Are you saying that Newton mentioned of some default medium for light in his Principia ?

My answer is, obviously: No.

Could you break it down why Lorentz Invariance is violated as long as Tachyon (fields or particles) never go slower than light and no direct method of interaction between Tachyon and Tardyon particles or fields.

I regret not having more time to help you with this, sorry, I'll think about it. It's a very basic matter of SR. I'm supposing that you left out a negation due to editing, else my answer would be a lot quicker! :Alien:

[paultrr]

Yea, one older model that has resurfaced from time to time amongst those who subscribe to aether theory, and yes, there is a whole group of them out there even today(Try the organization known as the Scientists. While also dealing with the medical profession they have articles they've published on physics also), is sometimes called the waveicle theory. Found it interesting that one could come up with something simular even deriving such out of M-Theory or field theory itself without having to resort to an aether of Newton's type. In general its also true that aether can be a catchall term. One simple statement often repeated is that Einstein emptied the aether and QM rather filled the vacuum back up. The biggest difference today is when that term is used it does not imply an absolute space and time like Newton proposed.

[Qfwfq]

...without having to resort to an aether of Newton's type...

 

...it does not imply an absolute space and time like Newton proposed.

Without repeating quite all of what I already posted:

 

Newton did not propose ether in connection with light.

 

Newton recognized the distinction between inertial and other frames of reference. He sure reached a sharper focus on dynamics than Galileo had reached but he substantially held the principle of relativity. No absolute space at all.

 

Prior to Einstein, only time hadn't been recognized as being a geometrical matter, subject to coordinate transformations.

 

I don't want to blow up an argument but I don't find it right either to post misleading things, or to not criticize them. History is important too.