Gravity may have saved the universe after the Big Bang, say researchers

Nov 24, 2014

Image credit: Credit: © DR / Fotolia

By Science Daily

New research by a team of European physicists could explain why the universe did not collapse immediately after the Big Bang.

Studies of the Higgs particle — discovered at CERN in 2012 and responsible for giving mass to all particles — have suggested that the production of Higgs particles during the accelerating expansion of the very early universe (inflation) should have led to instability and collapse.

Scientists have been trying to find out why this didn’t happen, leading to theories that there must be some new physics that will help explain the origins of the universe that has not yet been discovered. Physicists from Imperial College London, and the Universities of Copenhagen and Helsinki, however, believe there is a simpler explanation.

In a new study in Physical Review Letters, the team describe how the spacetime curvature — in effect, gravity — provided the stability needed for the universe to survive expansion in that early period. The team investigated the interaction between the Higgs particles and gravity, taking into account how it would vary with energy.


 

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29 comments on “Gravity may have saved the universe after the Big Bang, say researchers

  • The media has been getting this story wrong since at least February 2013 (see [12] [here]1). The Higgs problem isn’t a matter of the universe itself being in danger; it’s a matter of whether the true physical vacuum is the one predicted by “electroweak” theory (the theory of the electromagnetic and weak interactions and the Higgs fields that unifies them). A vacuum minimises a quantity called the effective potential. The resolution discussed here is to include an extra term in the formula for the effective potential. (This extra term was always legal, but had been avoided in early models because physicists prefer the simplest model that fits the facts we know.)

    The media is also muddling the way this term comes about. That extra term is proportional to a measure of spacetime’s geometry called the Ricci scalar (denoted R), so we need this to be nonzero. It’s true that gravity distorts spacetime, modifying the Ricci scalar in general. However, it doesn’t need to be gravity that gives a nonzero value for R; it can also come from the history of how quickly the universe has expanded. Almost any outcome of the Big Bang would be suitable.

    If you read their paper, it’s the term with an R in it in Equation (1), on page 2. This term is also proportional to a number denoted by the Greek letter xi (it looks like a complicated capital E). If that number is 0, the term disappears. That’s what physicists hoped for in the past, since it’s simpler than any alternative. What this paper is saying is that all we need to do is admit xi isn’t 0. (More precisely, it needs to be big enough to fix the problem. They’ve quantified it.)



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  • 2
    Light Wave says:

    The early universe expanded into what was previously a vacuum like void…I always have trouble imagining ‘nothing’ as a real concept…….I imagine the universe as an air bubble floating upwards through a fluid like substance toward the surface of something, I just cant get my head around nothing…unless it was a frozen something that since melted and left no trace if its existence…



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  • I just cant get my head around nothing…unless it was a frozen something that since melted and left no trace if its existence…

    Probably the toughest concept in physics to get our brains comprehend this concept. It messes with millions of years of brains seeing stuff. This is the erroneous thought.

    The early universe expanded into what was previously a vacuum like void…

    The universe didn’t expand into a pre-existing space. Stuff only exists, inside the universe. Stuff can’t exist outside, because the particles that make up stuff, can only be created inside. I’m probably not helping. Laurence Krauss’ book “Something from Nothing” is the best I can recommend. After reading that, I could understand the potential for something to come from nothing. It’s also discussed in a wonderful video where Krauss is interviewed by Dawkings about this “nothing” concept and then visa versa about evolution. It’s great viewing. It goes for two hours. If you want to cut to Krauss explanation about “nothing” go forward to around the one hour mark.

    https://www.youtube.com/watch?v=YUe0_4rdj0U

    The evolution explanation is also good, but I kinda got that already.



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  • Thank you. Joss.

    You have done that marvelous Feynman trick of making me think I understand it a bit, which makes me less scared of it, which means one day I may actually get to understand it a bit.



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  • 6
    NearlyNakedApe says:

    For my part I have no trouble admitting that this is way over my head.

    I think that if one isn’t intimately familiar with the underlying mathematics of advanced theoretical physics, it’s virtually impossible to really grasp any of what is discussed in this article. So those of us who don’t belong to that specific category shouldn’t worry too much if we have a hard time wrapping our brains around it. Maybe it’s just a question of not having put enough work into it.

    I am grateful however for Jos’s insight (and IQ) on the subject. Thank you.



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  • 7
    NearlyNakedApe says:

    Laurence Krauss’ book “Something from Nothing” is the best I can recommend. After reading that, I could understand the potential for something to come from nothing.

    Same here. It was a fascinating book. Particles can come in and out of existence from quantum fluctuations, I get that. But I’m assuming that (if I understand it correctly) this phenomenon occurs in time-space.

    But if the Big Bang hasn’t yet occurred therefore time-space doesn’t yet exist right? So how could quantum fluctuations occur in the absence of time-space?



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  • Light Wave Nov 24, 2014 at 9:20 pm

    I just cant get my head around nothing…unless it was a frozen something that since melted and left no trace if its existence…

    It is quite funny when creationists babble on about “nothing”, because there are no examples of “nothing” in existence!

    Everywhere in the universe there is something! –

    On Earth – an empty glass is full of air.

    In the Solar-System, between planets, in the “vacuum” of interplanetary space, there is the Solar Wind, light, gravity, magnetism, and sparse molecules.

    In interstellar space in galaxies, there are nebulae , gasses, photons, and gravity.

    In intergalactic space there are still photons – radiation and gravity pulling galaxies together.

    The “true physical vacuum”, Jos quoted, is theoretical physics, and does not match the common concepts of “nothing”!



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  • Space and time are thought to be quantized as well. Meaning they too can result from quantum fluctuations. I think it was Alexander Vilenkin that first did the calculations on a model which showed a spacetime could nucleate from nothing (a kind of quantum tunneling) and undergo inflation to create a universe.

    So for this model the only thing necessary then is that somehow the laws were set before space and time existed.



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  • 10
    inquisador says:

    physicists prefer the simplest model that fits the facts we know.

    Well then ‘God did it’.

    Obviously he bootstrapped his way into existence using his mysterious ways (in ‘wonders to perform’ mode), just as he made billions of other universes.

    No need to thank me.



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  • Needless to say, physicists have a very specific idea in mind when they say “simplest”; it refers to having the fewest possible unspecified parameters appearing in the equations. If a parameter to which a term is proportional is set to 0, that term disappears, which effectively gets rid of that parameter as well. This simpler theory is then preferable, if it also fits the data. But a comparison of the Higgs mass with that of the top quark suggests we may need to resurrect such a term we sought to avoid.



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  • I endorse Phil’s comments. Thank you Jos.

    I blame god actually. His intelligent design has created me with boundless curiosity about the life, the universe and everything, but he fitted me with a 4 cylinder brain with a dodgy spark plug such that I kinda get the overall concepts, which I enjoy, but will never be able to understand the details, which I would like. A bit nasty actually god. Sigh….



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  • But if the Big Bang hasn’t yet occurred therefore time-space doesn’t yet exist right? So how could quantum fluctuations occur in the absence of time-space?

    This is the bit that really messes with your mind. As I understand Krauss, the quantum fluctuation occurs in the nothingness, outside and before the big bang. It creates the big bang. Pass the aspirin.



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  • Alan4discussion:

    The “true physical vacuum”, Jos quoted, is theoretical physics, and does not match the common concepts of “nothing”!

    In other words the “nothing” of the philosophers and theologians is only imaginary. It has no basis in reality. Thank you.



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  • But if the Big Bang hasn’t yet occurred therefore time-space doesn’t yet exist right? So how could quantum fluctuations occur in the absence of time-space?

    Quantum mechanics is not, first and foremost, a theory of objects’ locations in spacetime and how these update as things change. It is a theory of what state reality adopts. Essentially, quantum mechanics lives not in “physical space”, but in certain mathematically similar structures called “Hilbert spaces”. (These are usually infinite-dimensional, although there are several notable exceptions.) For example, while a particle has infinitely many classical positions in a 3D space, the wave function describing how its possible positions are superposed in quantum theory is a point in an infinite-dimensional Hilbert space: one dimension per point in 3D space. But even if no space exists, nature can have properties other than “where things are”. As long as there are details one can specify, quantum mechanics has something to work with. Unfortunately, the details of how one gets a universe out of this aren’t quantum mechanics 101. Indeed, some of it is quite recent research, e.g. here.

    Note: to be more precise, the state associated with a given wave function is a point a unit distance from the Hilbert space’s equivalent of an origin. Just as the surface of a sphere has 1 fewer dimension than the space in which the sphere is placed, so the surface to which the state is confined has 1 fewer dimension… except that makes no difference, if we’re dealing with a space that’s infinite-dimensional anyway.



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  • 17
    NearlyNakedApe says:

    It is quite funny when creationists babble on about “nothing”, because there are no examples of “nothing” in existence!

    One could say the same thing about Creationists when they talk about infinity (eternal life) and yet there are no known concrete examples of infinity either. But of course there are many more things creationists talk about for which there are no examples in existence….

    Talking snakes, vegetarian felines, parthenogenesis in primates, etc….



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  • NearlyNakedApe Nov 26, 2014 at 12:17 am

    One could say the same thing about Creationists when they talk about infinity (eternal life) and yet there are no known concrete examples of infinity either.

    You can set a camera focus to infinity, – but that does not make the picture “infinite”! (A YEC would probably be unable to understand that concept!)



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  • I look after grand children, so at my age, I can legally watch kids movies like Toy Story, because that’s my job. Reminds me of the character Buzz Lightyear’s saying,

    “To infinity and beyond” Always raised a chortle with me.



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  • 20
    Light Wave says:

    Lawrence Krauss’s theory that theres nothing before the expansion of space itself….is so far only a theory…..and scientists have only just discovered Higgs Bosons – and there was a time when they didnt know bosons existed….so David Allen there may be ‘something’ undetectable……im not talking about about the visible…we can detect dark matter but cant see it….we know there must be loads of dark energy but cant see it or detect it….so I just dont accept lawrences view that theres no thing…..there is something and its small and practically undetectable….thats more plausible than nothing….



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  • .so David Allen there may be ‘something’ undetectable..

    Totally agree Light Wave. We just don’t know. Krauss’ idea appeals to me. It just seems to fit my commonsense gene, but he may be wrong. I just can’t wait to find out though. I want to fast forward to the end of the movie. We’re due for another Einstein / Newton / etc etc… I hope its in my life time.



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  • 22
    NearlyNakedApe says:

    I look after grand children, so at my age, I can legally watch kids movies like Toy Story, because that’s my job…

    For my part, I have no grandchildren and thus, I am obliged to admit, have opted for a life of crime by shamelessly reveling in such animation films. Toy Story rules… There, I said it 😉

    Reminds me of the character Buzz Lightyear’s saying,
    “To infinity and beyond” Always raised a chortle with me.

    It still makes me laugh to this day. Too bad this gem of absurd humor is probably lost on most young children and many adults.

    [a=href/blatant justification of wicked criminal activity] But this kind of demonstrates that some of the humor in those animation movies is what makes them “family oriented” rather than strictly “child oriented”.[/a]



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  • Jos’s explanation is very good and well informed, but as one of the authors of the paper (also available at http://arxiv.org/abs/arXiv:1407.3141), let me clarify something. The term describing the interaction between the Higgs field and the spacetime curvature is not an extra term whose addition makes the theory less simple. Renormalisation theory tells us that we should include all terms that are allowed by symmetries and have mass dimension of at most four. The Higgs-curvature coupling satisfies these conditions, so one cannot consistently leave it out. Rather, it is a parameter we have to measure, just like all the other parameters of the Standard Model. Setting its value to zero would not make the theory simpler and would be no better motivated than any other value. Indeed, if it actually turned out to be exactly zero, that would be fine-tuning that we would not be able to explain. (In fact, 1/6 turns out the be a “natural” value.)



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  • I hope I am not being pedantic with the following observations:

    This is not Krauss’s theory. It was shown by A. Vilenkin that a closed spacetime could tunnel from a state of no space and time in the early ’80s (he published the paper in the early ’80s, he did not find the universe was created in the early ’80s to despite what some Regan republicans might think). In what is called a false vacuum state this spacetime could undergo inflation and result in our universe.

    As Krauss has said many times, we don’t know that this happened but we do know that the laws of physics allow a universe from a state of no space and no time. Therefore, it is plausible and there is little to suggest that it more or less plausible than other serious contenders for cosmological origins.

    Also, we have detected dark energy in several ways. We’re not certain what it is. It appears to behave like a vacuum energy but if it is then we have no idea why the value of the vacuum energy is so small.



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  • Arttu, I apologise for the way I described it. You’re right that we knew all along that that term will appear with some value of xi or another, and that setting xi=0 isn’t particularly natural or “simple” in any finite spacetime dimension (and for 4 spacetime dimensions the most natural value of xi is 1/6).

    What I probably should have said is that, with your and your colleagues’ paper, we’ve gone from saying little about xi’s empirical implications for electroweak vacuum stability to noting that the two are consistent in the light of recent empirical Higgs and quark masses. That more accurate description would have made sense of the timing of this finding. It would also have emphasized that the finding is essentially conservative, in that to preserve electroweak vacuum stability we don’t need to consider an alternative to standard 1-Higgs electroweak theory to get a broader class of renormalisable terms.



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  • I have less if an issue with the concept of “nothing” than I do with the concept of “something.” Why should there be something instead of nothing? And to talk about something originating out of a quantum wave fluctuation says to me that something already existed – the quantum wave.

    To nothingness, and before.



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  • All of this dancing on the theoretical head of a quantum pin doesn’t explain how it avoids the first law of thermodynamics. Nor does it answer the question of what source of what power compressed all of the matter and energy of the universe into a point from which a “big bang” could have emerged, much less how many times this might have happened. Einstein was not alone in demanding experimental proof from spinners of mathematical theories. It is plausible that dark matter is just too low in density to have or create energy to be detectible by current means. But all of this something from nothing? That lacks credibility/gravitas. So, no Feynman effect yet.



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