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[P]
CERN researchers demonstrate matter/antimatter 'loophole'

By Tatarigami in News
Tue May 15, 2001 at 09:19:14 AM EST
Tags: Science (all tags)
Science

Currently accepted scientific theories of the creation of the universe say the Big Bang should have created an equal amount of matter and anti-matter, and that the two mutually exclusive forms of stuff should be slowly wiping each other out of existance -- but astronomical observation has shown us this isn't happening. Now scientists working on the CERN particle accelerator believe they have found evidence which supports a theory that could explain why.


A BBC news report details efforts of a team of scientists working on the CERN particle accelerator have observed sub-sub-atomic particle behaviour which appears to favour the long term existance of regular matter over anti-matter.

The current most widely-support theory of the universe' creation says that an equal amount of matter and anti-matter should have been created by the Big Bang, and that interactions between the two forms should be observable as radiation sources in space. However, the expected sources don't appear to be there. Any such source within 10 billion light years should be possible to detect. Even if the matter and anti-matter were widely separated by physical distance, a total segregation seems unlikely, so science has been forced to look for other answers.

This CERN Courier article describes contenders for the General Unified Theory (a theory which would encompass all possible interactions between the various existing forces and states of matter) submitted several decades ago which does allow for this 'charge parity violation', but also require three other conditions: an expanding universe (this is accepted without question), the potential for protons to be unstable (which has been previously observed), and cases of fine-scale particle interactions which violate the mirror-image equality of matter and anti-matter. It is these interactions which have been observed at CERN.

This outcome suggests an alteration to the model for the beginning of the universe -- equal amounts of matter and anti-matter were created and proceeded to annihilate each other, but the slightly uneven relationship between them allowed a fraction of the regular matter to survive and become the sum total of observable matter in the universe today.

Luckily for us...

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CERN researchers demonstrate matter/antimatter 'loophole' | 26 comments (25 topical, 1 editorial, 0 hidden)
Wow. Nifty Stuff (3.00 / 1) (#1)
by funwithmazers on Mon May 14, 2001 at 08:01:11 PM EST

That means the whole universe as we know it, dispite being really really friggin' big, is just a small fraction of what originally existed.

Population zero (4.50 / 4) (#2)
by Tatarigami on Mon May 14, 2001 at 08:05:33 PM EST

Considering the topic, and the recent passing of a respected author who had some thoughts on the subject, I don't think this quote is out of place:

    "It is known that there are an infinite number of worlds, simply because there is an infinite amount of space for them to be in. However, not every one of them is inhabited. Therefore, there must be a finite number of inhabited worlds. Any finite number divided by infinity is as near to nothing as makes no odds, so the average population of all planets in the universe can be said to be zero. From this it follows that the population of the whole universe is zero, and that all people that you may meet from time to time are merely the products of a deranged imagination."


[ Parent ]
Finity (none / 0) (#6)
by brion on Mon May 14, 2001 at 09:14:39 PM EST

However, not every one of them is inhabited. Therefore, there must be a finite number of inhabited worlds.

Of course, the late great Mr. Adams was writing humour, not mathematics; such an assertion is demonstrably false: There are an infinite number of integers, since you can continue to count integers without ever running out. Only every second integer is an even number, but even numbers are also infinite, countable without end.

Thus, half of all integers are even and there are twice as many integers as there are even numbers, but there are an infinite number of each!

This will drive one mad until one realizes that "infinite" is not a number or quantity, but a description: literally "without end". So while there may be a finite number of inhabited planets in an infinite universe, there may still be infinite inhabited worlds and more uninhabited.

But that wouldn't have been funny, would it?



Chu vi parolas Vikipedion?
[ Parent ]
Limits. (none / 0) (#23)
by dice on Wed May 16, 2001 at 03:26:42 PM EST

Limits are wonderful ways to deal with infinity.

One of the only practical ways, at that.

So let's see, the dispersion of even numbers over the integers is n/2n (assuming you're talking about things like -2 being even, which is the only way to make sense of your post).
Since there are infinite integers, the ratio of even numbers to integers is lim n->inf n/2n. Which evaluates to 1/2.
Now, for the quote.
The quote says simply that the number of planets approach infinity. And that c is the number of inhabited planets. (c is constant). So the ratio of inhabited planets to planets is lim n->inf c/n. Which is 0. Which also happens to be the average population of each planet.

Now that we've explained that, can you point out the real logical fallacy in the quote?

[ Parent ]
The logical fallacy is assuming that <100%=fini (none / 0) (#25)
by brion on Thu May 24, 2001 at 04:09:37 PM EST

(see subject)

Chu vi parolas Vikipedion?
[ Parent ]
(Sorry, subject line cut off) (none / 0) (#26)
by brion on Thu May 24, 2001 at 04:14:31 PM EST

The logical fallacy is in assuming that less than 100% of an infinite number ('not every one of them isinhabited') results in a finite number ('therefore, there must be a finite number'). As both of us proved, a fraction of an infinite count can still be infinite.

Now, if it were a given than the number of inhabited planets were finite, then the average population of zero would indeed be correct. However, the finiteness was not given, but derived in an utterly incorrect fashion.



Chu vi parolas Vikipedion?
[ Parent ]
This doesn't sound right (2.00 / 1) (#3)
by John Milton on Mon May 14, 2001 at 08:24:42 PM EST

equal amounts of matter and anti-matter were created and proceeded to annihilate each other, but the slightly uneven relationship between them allowed a fraction of the regular matter to survive

If they were equal how could they be uneven? Do anti-protons decay faster? Is that what you were trying to say? That would make sense. I guess I'll just have to follow the links or rely on someone else to help me on this one.


"When we consider that woman are treated as property, it is degrading to women that we should Treat our children as property to be disposed of as we see fit." -Elizabeth Cady Stanton


Nah (4.50 / 4) (#4)
by spiralx on Mon May 14, 2001 at 08:35:48 PM EST

IIRC it's due to different reaction cross-sections under certain reactions that violate CP conservation with respect to matter and ant-matter. Basically in the very early universe the reactions that were producing all of this stuff from quarks took place at a slightly different rate for matter and anti-matter, and when the temperature dropped below the critical level and all such reactions stopped, we were left with approximately a billion and one protons for every billion anti-protons. These then proceeded to annihilate each other as they tend to do, leaving us with a single proton and a lot of photons.

Of course my understanding of this is somewhat fuzzy and its late, I'll look it up better tomorrow ;)

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

Equal but uneven (4.00 / 1) (#5)
by Tatarigami on Mon May 14, 2001 at 08:47:12 PM EST

If they were equal how could they be uneven? Do anti-protons decay faster? Is that what you were trying to say? That would make sense. I guess I'll just have to follow the links or rely on someone else to help me on this one.

Guess you'll have to follow those links. I couldn't find anything in those articles which stated flat out what the effect was that they observed -- but my eyes did start to glaze over when they turned up the technical language. You might be able to follow it better than I could.


[ Parent ]
Technical (and not so technical) explanations.. (5.00 / 2) (#10)
by Mad Hughagi on Tue May 15, 2001 at 10:45:51 AM EST

If you want the nitty gritty, here is a .pdf presentation that one of the groups CERN presented last year on their efforts with this experiment: LEAR at CERN

It's rather technical though, so it probably won't be of much use unless you have a fairly solid background in physics.

If you want to look at the conference (it was last years international confrence on CP violation): International CP Confrence 2000

I don't really know enough about this stuff to give a definate answer as to what it is they have actually done, but I'll try to give an explanation that isn't too abstract:

Charge/Parity conservation is centered around the observation that in a transformation of sub-atomic particles (reaction, decay, whatever) the results will obey certain conserved properties of the original entities. We are commonly taught such things as the "conservation of energy" in high-school - CP is just an extension to different properties on the sub-atomic (quantum) scale. It was originally assumed that CP was always conserved - this would lead to a certain set of laws by which the universe could evolve. In the 60's they found examples of CP violation. This shook up the situation - if something is no longer conserved on the sub-atomic level then it can have very far reaching effects on many levels (matter/antimatter in the known universe).

This experimental confirmation was not ground-breaking in the sense that it opened up the concept of CP violation - it simply pin-pointed the actual degree of CP violation in the K meson decay sequence and strongly confirmed that CP violation is a statistical reality and not just a chance occurance in the labratory.

Like I said though, this concept has implications that are very far-reaching throughout physics. I don't think I can really do it justice since I don't understand enough yet to really "get it" myself.


HUGHAGI INDUSTRIES

We don't make the products you like, we make you like the products we make.
[ Parent ]

My understanding (none / 0) (#13)
by kostya on Tue May 15, 2001 at 11:46:00 AM EST

From really elementary, explain-physics-to-morons-books, is this:

Yes, they anihilate and create equally, but not at high-energy states. At really, ultra-high energy states (ones occurring only at the briefest bit of second after the Big Bang), the reaction is the same, except an extra-proton can appear. So where you had a proton+antiproton you now get an extra proton. But at our current energy states, we don't see this. Thus, the particle accelerator.

That's how the theory goes. And it just so happens that the theory fits with the current mass of the universe. Or so I'm told by my Idiot's Guide to High Energy Physics :-)

----
Veritas otium parit. --Terence
[ Parent ]

In a sense it doesn't matter (4.00 / 1) (#7)
by SIGFPE on Mon May 14, 2001 at 10:03:35 PM EST

Do anti-protons decay faster?
In a sense it doesn't matter. The importance of this result is slightly more abstract. Suppose we found that CP violation never occurred. Then physicists would be in a fix because they would have to explain a blatantly non-CP invariant universe using CP-invariant laws - possibly an impossible task. Because we are now confident of CP-violation physicists can sleep better at night because whatever mechanism they propose isn't going to be blocked by CP symmetry. So you don't necessarily need to worry about what actually took place in the experiment because that process probably isn't the same process that caused the imbalance we see around us. What is important is that a roadblock to certain types of theories has now been opened and there is a framework in which physicsts can now look for good theories.

In summary this experiment is a kind of negative result - it doesn't show a class of theories is more likely but it removes objections to another class of theories.
SIGFPE
[ Parent ]

Questionable science (2.00 / 2) (#9)
by jd on Tue May 15, 2001 at 09:23:29 AM EST

Let's say that matter and anti-matter have an equal probability of condensing out of the energy that was created at the Big Bang.

(I'm not entirely convinved that the energy -was- created, but that's another story.)

Before we go anywhere, is this a valid assumption? The energy is being created via an assortment of processes (not least, the sudden, very rapid, expansion of the Universe seperating virtual particles, making them "real). We also know that matter and anti-matter aren't "different", but simply mirror-images. Particles have 720' of symmetry (Brief History Of Time), and a rotation of 360' will switch matter to anti-matter, and vice-versa.

Ok, I think we can see that there is some potential here for the Universe, at any given instant, to have an unequal number of particles. It's not that one is favoured over the other, it's that (statistically-speaking), the probability of all particles spinning at identical rates, with absolutely uniform starting positions, is so mindboggingly-small that non-parity is actualy inevitable. The idea that you need an entire field of physics to describe it sounds more like an effort to scrounge money for =real= cash-starved projects.

The "fine-scale" issue is the same thing, IMHO. To get a mirror-image balance, or to get a reaction which is symetrical, you need two particles which are 360' out of phase with respect to each other. If you can achieve that, by any engineering feat achievable today, repeatedly and regularly, you might want to have a little chat with Heisenberg.

Going back to parity, for a moment, you WILL have parity, but it must be parity on phase, spin, mass/energy and momentum (linear and angular). And it won't last, as the system isn't closed.

If you don't observe ALL these properties (which you can't, so there!), you cannot determine if a mirror image exists. (In physics, at this level, a mirror needn't produce an absolutely identical image, merely an image with an absolutely identical net state. At the quantum level, there really isn't any difference.)

Questionable Science? (4.00 / 1) (#11)
by Mad Hughagi on Tue May 15, 2001 at 11:17:56 AM EST

Using "A Brief History of Time" as a principle resource to make the efforts of hundreds of theoretical and experimental physicists over almost 40 years seem trivial doesn't really do things justice IMHO.

The thing that is important here is that they aren't going about trying to prove something in the sub-atomic domain simply to show the matter/antimatter distribution in the universe. This is an observable phenomenon on the sub-atomic scale and has consequences which manifest themselves on all sorts of different scales. The purpose of this field of physics is to consolidate the possibilities which should be considered for the next level of theories - an experimental confirmation showing that the "universe acts like such and such a way" is anything but a money scrounging effort.

Please don't be so rash about things - it's good to have new ideas and whatnot, but going about trashing things and spewing out discoherent ideas doesn't really help the discussion.


HUGHAGI INDUSTRIES

We don't make the products you like, we make you like the products we make.
[ Parent ]

Trashing doesn't help, but... (2.00 / 2) (#14)
by jd on Tue May 15, 2001 at 01:51:53 PM EST

...skeptisism is the essence of science. The puny little snowballs I'm capable of throwing should not bother any solid wall of theory.

(If it does, it's not much of a wall!)

What DEEPLY concerns me is the lack of any skeptitism amongst the scientific community. They =SHOULD= be hurling boulders, firing cannons, and otherwise trying to blast huge holes in that wall. Not because they're against anything new, but because any theory that's solid will shrug off any such punishment.

THAT is the essence of science. Blow holes in the theory, to find the weak points. Then, the theorists can go mend those holes, knowing the rest of the structure is sound. Repeat until impervious.

And THAT is what I am always trying to do, in my own, limited way. Again, for the simple reason that if some pathetic snowball can cause the wall to shake, never mind collapse into a pile of rubble, that theory has a serious problem.

It's not malice, but =support=, that makes the skeptic, well, skeptical. If they didn't care, they wouldn't bother!!!

Last, but not least, the stuff I'm hearing from cosmologists and physicists is revolting. Every standard concept in science -- DON'T multiply entities, DO create falsifiable theories, DON'T just add fudge factors, DO test your theories, independently of the means used to derive them -- are being broken by the modern drive to publish.

IMHO, THIS is the scary part. That scientists are so desperate, now, to be in print that they would sacrifice every principle they ever had to do so.

[ Parent ]

Sensationalist Views (5.00 / 3) (#16)
by Mad Hughagi on Tue May 15, 2001 at 02:35:42 PM EST

People are still skeptic! It's just that they arent' skeptic about the things that you see in the news. CP violation is over 40 years old! This has been beaten to death and they are still working on it's implications.

Take something like the evolution of the universe. People still argue over it's creation, how it is going to evolve, etc etc. The thing is that most scientists know what to be skeptic about in the first place! A scientific breakthrough comes about because know where to look for the answer, not what the answer actually is. There is one subtle point here and I'll explain it later though.

As for standard concepts in science, I'm afraid that you have a romantic view of how science progressed in the past. The ground-breaking theories that we take for commonplace came about by tweaking this approximation, trying this method, etc etc... It's not like someone just got up one morning and the "great theory of ____" just popped into their heads. Even Einstein found himself guilty of fudging - cosmological constant anyone? As far as I'm concerned it's better to try to modify a fairly acceptable theory than to shoot for an answer in random directions.

The point of the matter (what I was referring to earlier) is that physics is highly dependant on the mathematics that we use to describe our reality. Look at how the theory of gravitation progressed. Newtonian (calculus) -> Special Relativity (Lorentz Transformations) -> General Relativity (Riemannian Geometry). What people overlook all the time is the fact that for the most part, the ground-breaking theoretical physics is being performed by applying new mathematical methods to old problems. Unless you understand the mathematics required to construct these theories, you cannot really appreciate what the theories entail. Math is the language of physics.

Our mathematical physics professor was telling us that every year he gets about 2 or 3 papers from people that have come up with very interesting theories about gravitation. The problem is that they haven't tested their theories against the math - and that is where their theories fail. I'm not saying that math is allways the best way to understand a theory - many concepts can be understood by using a different approach - but in the end if the math doesn't work, the theory can't be right.


HUGHAGI INDUSTRIES

We don't make the products you like, we make you like the products we make.
[ Parent ]

Re: Questionable science (5.00 / 1) (#18)
by sigwinch on Tue May 15, 2001 at 04:51:54 PM EST

Particles have 720' of symmetry (Brief History Of Time), and a rotation of 360' will switch matter to anti-matter, and vice-versa.
Reader's Digest Quantum Mechanics: The behavior of a quantum is governed by its wavefunction, which evolves over time. The wavefunction is a three-dimensional field of complex numbers; the wavefunction has a specific finite complex value at each point in space. The probability of finding a particle at a particule point in space is equal to the complex conjugate of its wavefunction at that point. The sum of probabilities over all space must equal one (i.e., there is exactly 100% probability of the particle somewhere).

There are two classes of particles: fermions and bosons, and they have somewhat different behaviors. For reasons I don't understand, all half-integral-spin (+/- 0.5, +/- 1.5, ...) particles are fermions. The integral spin (0, +/- 1, +/- 2, ...) particles are bosons. The two types of particles have substantially different behaviors.

Fermions have the property that if you rotate them 360 degrees through space, you have multiplied their wavefunction by -1. This does *not* turn them into antimatter -- it just changes how the particle interferes with itself: how its wavefunction adds up over space.

Imagine the classical two-beam interference experiment with fermions. The particles come out of a source, strike a splitter that has a 50% chance of sending them down two different paths, and reflectors bring the two paths back together at a detector. Since the particles have wavelike properties, an interference pattern is formed at the detector.

Somebody actually did the 360 degree experiment with neutrons. Unlike most fermions, a neutron has a magnetic field, and you can rotate it with plain old magnets. The researchers put magnets on one path of the interferometer, rotated the neutrons through 360 degrees, and the interference pattern changed exactly as if the wavefunction for that path had been negated. They also tried 720 degrees, and the interference pattern went back to its original state.

The upshot is that the geometry you take for granted is not the same geometry that governs wavelike entities.

Going back to parity, for a moment, you WILL have parity,
Parity conservation is the idea that, if you look at a reaction in a mirror, it will still obey exactly the same laws of physics. The "mirror" is not a real reflector, but a notional device used to analyze the physics. I.e., if you reverse all the spins and invert the left-right relationships in an experiment, it will still follow the same rules. Likewise, charge conservation means that if you invert all the electric charges, the same equations will still predict the results. It has been found that both charge and parity considered separately are violated.

CP conservation says that, if you invert charges and parity, physics will stay the same. CP conservation holds pretty well in most circumstances, but there are still violations. These violations allow high-energy reactions to produce different amounts of matter and antimatter.

CP violation is interesting for cosmology because it lets you start with a big pile of balanced matter and/or energy in any form, and end up with slightly more matter than antimatter. If CP wasn't violated, the big bang would end with very little left over matter -- it would all be photons and neutrinos.

--
I don't want the world, I just want your half.
[ Parent ]

Correction (none / 0) (#24)
by sigwinch on Sat May 19, 2001 at 08:55:23 PM EST

Substitute "invariance" for "conservation" above. (Or "conjugation invariance" if you're really picky.) Don't know what I was thinking.

--
I don't want the world, I just want your half.
[ Parent ]

Proof for something accepted (1.00 / 1) (#12)
by kostya on Tue May 15, 2001 at 11:40:25 AM EST

IANAHEP. Maybe I'm showing how much of a rube I am, but in Davies God and the New Physics he cites this theory. And that book was published in 1983.

So I don't really think this is very astounding, in terms of theory. Now proving it might be cool. But I thought it was considered pretty supported by high energy physics already. But then, I'm not a high-energy physicist, so whaddaeyeno?

For those citing bad science, I think you should look up the stuff. This theory has been around for a while. It involves ultra-high energy states, and at those states things act really wacky.

I wouldn't recommend Davies book, however. It was a lot of conjecture on some fronts. On top of that, it was written in 1983 and a lot of stuff has changed. I.e. in the book it debates what it means if the universe is proven to be expanding forever or expanding with contracting coming up--but it is pretty established that it is expanding without the possibility of a big crunch (right? or do I have this wrong?).



----
Veritas otium parit. --Terence
Re: Proof for something accepted (5.00 / 2) (#22)
by Mut on Wed May 16, 2001 at 09:14:56 AM EST

Hi.

You're right that CP violation isn't a new concept; it was shown to occur experimentally back in 1964. However, there's work to be done beyond simply showing it happens - measuring the parameters that describe it has proven tricky. The kaon-based experiments have laid the foundations here and it's hoped that the numbers can be really pinned down by the next generations of CP violation experiments which work with b quarks.

These parameters are important because the Standard Model makes predictions concerning them. If we can show by experiment that these predictions are wrong, that would indicate new physics. We have hints that this will indeed be the case: calculations suggest (but only suggest) that the Standard Model values don't give enough CP violation to explain the matter-antimatter asymmetry in the universe mentioned in the article.

Obligatory plug: there's some background at the public info pages for the experiment I'm working on (LHCb, which will start taking data in a few years' time). I'm sure a quick Google search will turn up more.

Cheers,

Mat.



[ Parent ]
Well, IAAHETP, so let me help out here.... (5.00 / 9) (#15)
by krlynch on Tue May 15, 2001 at 02:10:47 PM EST

Since I am a HETP, let me try to help out here a little, and see if I can't clear up the confusion caused by this incredibly poorly written BBC article....

Modern cosmological/particle physics tells the following story: the universe started from a singularity, with physics we don't understand. For some reason, it began to expand (the big bang), and the energy that was liberated was able to split into particle/anti-particle pairs. These pairs would annihilate again into radiation, and the cycle would continue, over and over. Now, in the absence of any interesting physics (which I'll get to later), as the universe cooled down, there would come a time when the radiation was no longer energetic enough to produce new pairs, so the ones that existed at that point would (more or less) all annihilate. Since we started out with none, and they are only created in pairs, we would end up with a net concentration of zero. Hence the problem: we don't have zero particles, we have lots of them. Of course, they wouldn't ALL be able to find each other (hence, the "more or less" above). If we ended up with a few more particles over here due to random motion after pair creation, there would be a few more anti-particles over there. As the universe expanded, these "islands" would move apart. Two problems: first, no one has come up with a reasonable mechanism to produce this matter/anti-matter separation (why would electrons and protons all end up in the same islands, and not end up in overlapping, but distinct islands?), and there are predictions as to how much radiation would be coming from the "domain wall interface" that separates islands. And we don't see that radiation, despite the fact that we should be able to detect islands of approximately the size of the visible universe.

So, along comes Andrei Sakharov, and he points out that there could be a mechanism that creates more matter than anti-matter, and it requires only three ingredients: 1) baryon violating processes (processes that create, net, more baryons in the final state than in the initial state of a reaction), 2) CP violation (a difference in the properties of matter and anti-matter, and 3) regions of the universe that are not in thermal equilibrium. It turns out that it is relatively easy to produce models with all of these properties, so it is relatively easy to produce models that generate more matter than anti-matter in the universe (In particular, the Standard Model of particle physics has all of these properties). The hard part is building a model that predicts a scenario that matches the universe we observe. Notice that CP violation is a major component of this story, so understanding it in detail helps us build models that more closely approximate the universe.

So what is CP violation? The details are technical, and require lots of equations, but the simplest description is that the laws of physics would not be quite the same if time ran in the opposite direction, from future to past. "Well, Duh!!" you might say, since our everyday lives suggest that this is the case (after all, if you took a home movie and played it backwards, everyone would be able to tell that it was running backwards). But physics on the subatomic scale, was believed until the mid 60s to run both forward and backward identically. (The perceived asymetry on the macroscopic scale is a consequence of large N statistics, not microphysics. This statistical mechanics asymmetry of time exists even in a fully CP invariant theory).

Now, to what these experiments measured: there are many possible sources of CP violation, and separating them out requires exquisitely sensitive experiments...just proving that CP is violated is extremely tough! The CERN and FNAL experiments were, quite embarrasingly, far out of agreement a few years ago, owing to the difficulty of making the measurements. Although I haven't read their current papers, I suspect that after analyzing more data, they are now closer to agreement with each other. And that is a major leap forward in our understanding of the CP violation parameters and the origin of the matter/anti-matter asymmetry of the universe.

CP violation (5.00 / 2) (#17)
by spiralx on Tue May 15, 2001 at 04:36:14 PM EST

Okay, I may be wrong, but isn't CP violation where the laws aren't invariant under charge conjugation and parity reversal, not time reversal.

Or since the Standard Model is CPT invariant (IIRC) are they the same thing?

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

CP, T, and CPT (5.00 / 4) (#19)
by krlynch on Tue May 15, 2001 at 05:06:05 PM EST

Technically, you are correct. CP and T invariance are different. P (parity) is an operation which reverses the spatial components of tensors (momentum vector included!), T (time reversal) is an operation which reverses the time components of tensors (so, it reverses time and flips spins), and C (charge conjugation) converts a particle of given spin and momentum to an antiparticle of the same spin and momentum. It is called charge conjugation because it changes the sign of the electrical charge (when that doesn't equal zero!).

However, as you point out, since CPT is conserved in the Standard Model, if you have CP violation, you must have T violation (similarly, if you have CP violation, either C or P must be violated, but not both). Typically, we discuss the observations of CP violation in terms of T violation for this reason (because it is easier to visualize), but we don't typically look for T violation directly, because CP violation experiments are easier to do.

Incidentally, this conclusion is not restricted to the Standard Model. CPT must be conserved in any causal quantum field theory, so if you believe that the world is well described by some QFT model, then you have to accept CPT invariance of the universe as a whole. In fact, the world does appear to be strongly CPT invariant experimentally. Conversely, if CPT is found to be violated, all of the progress we've made in QFT in the last few decades goes out the window.

[ Parent ]

Cheers (none / 0) (#20)
by spiralx on Tue May 15, 2001 at 05:30:41 PM EST

My understanding of the subtler aspects of group theory, Noether's theorem and the transforms involved all come from my own research during my undergraduate degree. Unfortunately I never got to do my PhD and go into research as I wanted to :(

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

CPT symmetry (none / 0) (#21)
by salsaman on Tue May 15, 2001 at 07:01:22 PM EST

Is it possible that while the universe is expanding there is more matter than antimatter; the universal expansion begins to slow then stop; then it begins to collapse and during the collapse phase it is reversed and there is more antimatter than matter ?

CERN researchers demonstrate matter/antimatter 'loophole' | 26 comments (25 topical, 1 editorial, 0 hidden)
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