One can generally speculate anything about what happened before the big bang. This is due to the simple reason that our understanding of Nature breaks down at the exact time of the big bang.
However, this has never prevented physicists from trying to build new theories (coffee helps).
[image credits: Pixabay]
I have very recently read an article, which has appeared on the arxiv a couple of days ago, depicting such an attempt.
In a few words, the authors use the CPT symmetry (I will come back to this concept further in this post) to explain that the universe after the big bang and the universe before the big bang are just symmetric images of each other.
In terms of particles, the model only requires the Standard Model (see all the posts referenced here for an introduction), with extra neutrinos. I will of course also come back to that further in this post.
The interesting feature to keep in mind for the moment is that those extra neutrinos allow for explaining the problematics of dark matter. This model hence seems to cure several issues in one go! It is a 1+1 free somehow!
As usual, something stupid is hidden in this post. Can you find it? Please leave a comment.
THE CPT SYMMETRY
Let us start by providing a definition for the CPT symmetry.
First, this has nothing to do with the Committee for the Prevention of Torture (and this is not the stupidity to find in this post). In physics, this corresponds to a threefold operation: charge, parity and time-reversal, or the C, P and T operations.
[image credits: LBL ]
The P transformation reverses the spatial configuration of the system. This is equivalent to look into a mirror. Everything is flipped (left becomes right, for instance).
The C transformation implies to replace all particles by the corresponding antiparticles, and vice versa.
The T transformation reverses the course of time to make it running backwards.
Quantum field theory tells us that there are fundamental reasons that nature is CPT symmetric. Equivalently, the laws governing nature are invariant under a joint C, P and T transformation.
THE CPT SYMMETRY AND THE BIG BANG
Taking all cosmological observations, it turns out that the structure of the universe is described, a few seconds after the big bang, by a spatially-flat Friedmann-Robertson-Walker metric.
This means that we have a standard three-dimensional space (cool, we are still 3D objects that can thus be printed), a time dimension plus a so-called scaling factor describing the expansion of the universe.
[image credits: WMAP (NASA)]
At the very first moment of the universe, the scaling factor is proportional to time. The expansion of the universe is thus more and more violent with time passing during the first fractions of a second of the life of the universe.
Inversely, this also means that the scaling factor vanishes at the exact big bang moment. This is the initial singularity that many mention.
In the research paper mentioned earlier in this post, it is shown that the initial singularity can be removed by an appropriate change of units. Furthermore, this also allows time to be negative.
The authors moreover show that once negative times are included, we have an apparent T symmetry between the post-big-bang and pre-big-bang moments. What is going on before the big bang is the image of what is going on after it.
As the CPT symmetry is fundamental in quantum field theory, we can move one step further and make the universe CPT-symmetric.
This is an interesting idea, and this corresponds to see our universe as a pair of universe anti-universe merging from nothing. In the same way that an antiparticle is a particle running backwards in time, the anti-universe would correspond to what happened prior to the big bang.
AND DARK MATTER IN ALL OF THIS?
In terms of particles, the theory assumes the Standard Model of particle physics together with a weird species of neutrinos known as right-handed neutrinos.
This has nothing to do with how neutrinos are writing, but how their spin is aligned or anti-aligned with their momentum.
In more details, the spin is an intrinsic form of angular moment carried by each particle. This for instance tells us how particles react to magnetic fields. On the other hand, the momentum describes roughly how the particles moves. The handedness of the neutrinos is then the way these two quantities are aligned.
[image credits: Wikimedia]
So far, there is not any experimental sign of a right-handed neutrino, i.e. a neutrino whose spin is aligned on its momentum. But it is very easy to embed those guys in the Standard Model.
And once they are there and assuming the CPT universe hypothesis, one can calculate their properties.
It has been found that right-handed neutrinos can be very good dark matter candidates as they are stable, super heavy (200 billion times heavier than the heaviest known particle) and super-weakly interacting.
TAKE-HOME MESSAGE
The very first moments of the universe are fascinating, especially when considering big bang cosmology. The latter however suffers from an initial singularity that makes the theory breaking down at that moment. In a recent paper whose longer version is available here, it has been shown that this singularity can be removed.
As a result, our universe has to be seen as a universe/anti-universe pair and satisfies the CPT symmetry appearing in quantum field theory.
A nice feature of this theory is that it can naturally accommodate dark matter within the Standard Model through the presence of right-handed neutrinos, i.e. neutrinos with specific properties that have not been observed so far.
The problem is that these right-handed neutrinos are almost impossible to detect… This scenario has however other ways to be observed and potentially confirmed experimentally, using the left-handed neutrinos and gravitational waves.
Therefore, please stay tuned to see how this interesting model survives (or not) future data!
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That's a fascinating new theory. Thanks for breaking it down so that even I could follow - I didn't feel the need to call the committee for the prevention of torture. ;-)
You say the right-handed neutrino would be almost impossible to detect - is this because of its weak interactions with other particles?
Thanks for the nice comment.
I was also shocked when I typed CPT in google to find a few references.... (but this is not the stupidity in this post). And then I laughed... ;)
It is in fact completely decoupled and we can only track its gravitational effects to see it. Which is why no dark matter experiment will ever be able to see it...
Hi @lemouth! Really awesome way of explanation.. Learnt so many things here!
Indeed I had a question on which I don't have the clear vision that whether dark matter still exists or it's completely dead?
Since, I also keep the same taste of learning about our universe and space. What I used to know was Universe most proportion is made up of dark matter? Please correct me if I am wrong! :)
HI @star-cv!
It is far from being dead. All cosmological data points towards its existence. It helps in explaining the galaxy rotation curve, the cosmological microwave background data, the formation of structure in the universe, etc... What is missing for the moment is its direct detection. But not all options have been ruled out so far.
Note that alternatives to dark matter exist to. But IMO, data does not favor them as strongly as dark matter.
The largest fraction of the energy budget consists of dark energy. Then comes dark matter and then the visible stuff to a tiny extent (4% of the full budget).
Thanks a lot for sharing this information... Now I can confidently bring my future posts if so on this topic!! :)
I am looking forward to read it. I hope I haven't missed it in being away for traveling reason :)
Don't worry you haven't missed it as I haven't completed yet. I have started working on it and very soon I will post it. :)
Then we will find out. I liked a lot your last one by the way :)
Thanks a lot @lemouth! I hope you will share your guidance in my future articles as well so that I can learn some new facts and unfolded mystery about space!! :)
Cheers!! :)
As we know a few of antiparticles are left after that famous big clash of matter and antimatter in the universe’s first moments. Yes, today the barionic matter is dominant but there are also some anti matter somewhere else in our universe. So your post makes me think that there still be an anti-universe which corresponding to the one before the big bang. And it overlaps with our universe’s dimensions with a back flowing time. And those anti particles have barionic matter counterparts in that anti universe
I couldn’t find any stupidity in the post. Maybe this comment of me could be the most stupid thing of this post☺️
This model actually also predicts the matter-antimatter asymmetry through thermal leptogenesis, which is something I haven't mentioned. This occurs through the existence of the two other heavier right-handed neutrinos (we have 3 of those guys in total). See here for more information.
Exactly. But I would say there is no really any overlap between both universe.
For the stupidity, it has been found. Check the other comments, you may get some hints ;)
Still, have some questions in my mind:
You mean (sorry they propose) that the 20% of universe's mass is composed of those right-handed neutrinos?
But this sounds a little bit strange to me. Because as you mentioned they are not observed yet. And maybe impossible to detect. Which makes them only theoretical particles such as axions or WIMPs. And by the way, Has this theory any explanation about dark energy as well? (I've taken a quick look at the paper you've linked, however, I need to read it at a later time in detail)
Yes, this is exactly what the model predicts.
They are by no means axions or wimps because they just don't interact at all with the Standard Model. They are not thermal relics but dark matter is here produced via another mechanism connected to gravity.
PS: sorry for the disappointment. There is a second link a couple of sentences later in the post :)
Interesting hypothesis. When we say the universe before the big bang is the reflection of the universe right now, does it mean that there were humans just like us, doing the exact same thing made up of antimatter? and what about entropy? from our point of view, the entropy decreases?
Would the detection of right-handed neutrinos be enough to validate the hypothesis? These neutrinos will be sad on August 13.
The anti-universe would actually be a CPT reflection of our universe. This means that the density of particles of species X with momentum p and helicity h at time t after the bang equals the density of the corresponding anti-particle species with momentum p and helicity −h at time −t before the bang.
I would say in increase with time being more and more negative. No changes here.
Interesting one @lemouth
Well as they say about universe, it started with a big bang.... can it collase or I mean to say is the process reversible?
This theory does not say anything about the future, so that we don't know (this is another question not addressed here) :)
Hey @lemouth, nice read as always!
So does that mean that right-handed neutrinos are not electromagnetically interacting? If so, how are their properties measured?
Lmao!
No they don't. They are actually totally inert with respect to the Standard Model interactions. The only way to get to them in this model is through gravity. In other theories featuring right-handed neutrinos, there are usually other fundamental interactions in the game that could help as well).
I hope this clarifies :)
Are right-handed neutrinos allowed to celebrate International Left-Handers Day? :)
Only if they can write! Good catch ;)
...and note I went to read about right-handed neutrinos, but discovered..."Kangaroos and other macropod marsupials have a left-hand preference for everyday tasks in the wild"
Unfortunately, I cannot discuss Australian animals in every post. This would make it unfair with respect to all left-handed people on Earth :D
Hlw friend, I always waiting for your interesting scientifical post. Why you don't post more??
This is a nice comment. Thanks :)
I would love to post more. I have actually 86 ideas of articles to write. But my time is limited. I am spending most of my steemit time helping others (with the @steemstem project in particular) instead of blogging myself. Also, my job already takes 70 hours per week, and I have a family...
another hit, i have to start paying more attention, is there a certain frequence to your essays or do you just pop it out when you feel its ready ? i wouldnt want to miss one ... on the subject here (and there i could recommend a very very nice audiobook aimed at people who arent really hawking level geeks .. it's called Astrophysics for people in a hurry (i say audiobook because i have trouble focussing on lengthy amounts of text, sadly since some time) but audiobooks can run in the background and i can just put them on repeat until something clicks i think the author is someone called Neil Tyson, im sure google knows, really nice introductory work starting at the actual big bang , not really on what might have been before, thanks again for the fabulous stuff ! ! ! ! food for thought
Thanks for this nice message. I am trying to post once or twice a week about novel physics ideas (basically scientific articles connected to state-of-the-art research). As I said in one of the other comments, I am spending most of my steemit time in helping others through the steemstem project (which takes really really a lot of time...), so that I am left over with very little time for my own blog.
Don't hesitate to recommend the audiobook to others (who is the author by the way?), they may like it. I have unfortunately no time to watch movies or listen to audiobooks... but some other may. I personally prefer reading ^^
i can imagine someone who gets asked to go speak at cern doesn't really have much time, but i also imagine you do what you like, which must be quite the fulfilling life.
the book is -- Astrophysics for People in a Hurry - by Neil deGrasse Tyson -- , available in both e, paper or audio from the usual sources which i wont link i suppose anyone interested will be capable of using google. There was a version on youtube too for people who can't afford but i know thats officially not ... then again, if it's in a public library somewhere its debatable but not on your feed by off-topic ofcourse.
I really appreciate you taking the time to answer too. I wonder if you do requests ... if you could ever do a piece on time, i mean time the way a physicist sees it.
I personally feel (im by far not a scientist but im duly interested in the world of physics as well as the more analogue human psyche)
I feel time is not a force as such but , allow me to try and explain and pardon if i use some words in the wrong place, terminology has never been my forté.
Time, as i see it is a variable in mathematic formulation, just like numbers its a human construct devised to explain, but just like numbers it actually doesn't exist in a physical form. Its merely perceived as an observation of change. I mean , there's actualy forces electromagnetism, gravity, the more abstract concept of entropy over time pushing things outward and the fact that all things in existence on all levels seem to vie for a state of balance or equilibrium is actually what makes everything move, collide, what provides friction and energy (which means mass, right ?) but time actually is not a force at all, for all i know time has not even been proven to exist so , my original thing its a construct needed to explain the physical reality through mathematics, but not a physical reality (like the aforementioned forces).
I know this is probably closer to metaphysics but id seriously like your opinion and if you ever do a piece on time, much obliged :)
in short : "If mathematics is a language, then 'time'is but a word." (i'll keep that for my future ted-talk once i graduate form steemstem-academy lol) ... the things that keep bouncing around in my head ...
(i would also ofcourse recommend to anyone the classic by Carl Sagan : cosmos which taught me a lot on the world here as a whole too, explained in 'normal' language and timeless piece of literature i think)
I have heard about the book, but I have never read it. I have actually very little tie to read books. It is a shame :/
I already did it in the past. If this is connected to wha I do or what I know, I can write on a given specific topic. So feel free to suggest anything.
I am not too sure to understand what you meant in considering time as a force. Time is not a force. It is a quantity that allows us to order events. I will try to write a post on time next week, maybe, if you want, and more in particular on how time is defined (in other words, how to rely on clocks).
Très bon post, un sujet passionnant.
La matière noire me fascine..
Merci @yann85. Je le traduirai en francais... peut-etre un jour :)
Are there left handed neutrinos as well? Asking for a friend :)
Yes of course. Those are there in the Standard Model already (and we don't touch them). The model however predicts that one of these is massless and two are massive.
A common structure in the universe is a disc with two perpendicular jets at the poles. Could the universe have an analogous structure?
Are you referring to black hole and the jets of particles they emit? I don't think this image works here because of the time dimension (but I may have answered too quickly... haver to think more).
Yes, and I thought the planar rotating disc with polar jets was found in other systems as well. Remember I'm an armchair cosmologist and get my theories in that field mostly from sources aimed at the interested public ;)
No problem. I have tried to answer with what I think here. I think this image does not apply here (I have trouble to make the analogy working with this damned time axis :D).
very interesting concept @lemouth . So the new theory suggests that universe acts in the same way the AD and BC works. Is it possible to see ourselves posting something on steemit in the Anti-universe? :)
Not really. It is more like two images on both sides of a mirror.
That really is interesting..so this is implying dark matter is residual from the "mirrorverse"?
Dark matter is present in both. It is not a left over from one side into the other.
Nice theory & post, very interesting. I tell you, fractals are the key.
Fractals? They have nothing to do here. Do you mind clarifying your statement?
interesting post for my reference. thanks for sharing @lemouth
My pleasure!
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Cool! Thanks a lot!