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Thread: Fluctuating energy..

  1. #1
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    Fluctuating energy..

    Helloooo !


    If our universe did come into existence via a random, spontaneous quantum fluctuation, then how and why was there so much energy ?

    I mean, i can imagine small amounts of energy fluctuating out of nothingness, i'm okay with that.. But like i say, at the beginning of our universe there was a massive
    amount of it, so how can so much energy fluctuate into existence, is there a hypothesised mechanism for it ?
    Far away is close at hand in images of elsewhere...

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    Kevin1981. Nope. Empty vacuum stays that way, otherwise you are trashing Conservation of Energy. Neither is there any experimental evidence for the observed excess of matter over antimatter. Coffee table physics books on cosmology skip lightly over the issue...like doing the Shaka Zulu dance over Ash laden hot coals. Step briskly and move on. pete

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    The most common conceptual model for what could have happened uses the idea of vacuum or initial state metastability. This is often also applied to inflation too

    The basic idea is that the universe existed in a high energy state that was also metastable. Then a fluctuation or tunnelling event took it out of that state and allowed it to drop to a lower energy state. This would release a huge burst of energy, as well as changing the basic nature of the universe. A common metaphor for this is if you imagine a ball sat on a ledge on a hill. Leave the ball alone and it is stable. But give it a little push and it may roll off the ledge and down the hill. If you just look at the speed of the ball you'd be shocked that a little push apparently caused this huge acceleration and end speed, in violation of energy conservation. But what you are actually seeing is a conversion of some potential energy to kinetic energy.

    As is said, this is a conceptual model of how a small fluctuation could lead to a large effect. We don't have the theory or data to do much more than propose it at the moment. The only place that things like this and matter/antimatter asymmetry are 'skipped over' are popular science accounts usually. Scientists tend to regard these areas as open questions, interesting and active areas of research.

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    Quote Originally Posted by trinitree88 View Post
    Neither is there any experimental evidence for the observed excess of matter over antimatter.
    I am slightly confused by this sentence. I assume you mean there is no experimental evidence for any proposed explanations for the matter excess?

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    Strange. No, I am talking about associated production in pair creation. When a high energy photon causes the creation of a matter/ antimatter pair, you always see, in a particle physics lab, a proton and an antiproton, or an electron, and a positron, or kaon and an antikaon. You never see one without the other. Charge is conserved, baryons number is conserved, lepton number is conserved, spin is conserved...etc. You have seen in one set of experiments, a slight excess, in B meson production, but no experiment in any lab, or any balloon borne, rocket borne, or satellite borne equipment ( AMS exp.)...has ever seen production of matter greater than antimatter. Sam Ting chaired the effort to get the AMS up and running specifically to resolve the alleged issue of excess positrons in cosmic ray studies. It ran, it collected data, I was sitting in the hall bldg.10-250 @ MIT, when they announced the results...no excess. The hierarchy of conservation laws of physics remains intact, despite many coffee table books propounding that a " slight asymmetry in matter over antimatter production is why we are here!". It's simply proven by very careful measurements, in exquisitely designed experiments, that that is not true. With the preponderance of lies in the media in other areas of the world, I feel it is incumbent upon myself and all other scientists and academicians to see to it that fact based data, outweighs opinions in coffee table books, and classrooms and lecture halls around the world.
    We have nothing to explain why the observed excess of matter...the world we see...over antimatter...exists. It is one of the great unanswered questions in science.
    pete
    Last edited by trinitree88; 2018-May-16 at 11:16 AM.

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    Thank you Shaula.. I thought that some physicists were happy with the idea that there was complete nothingness and then energy fluctuated into existence..

    But what you are describing is that there was a high energy vacuum state that decayed into a lower energy state that started of the inflation period in the very early universe.

    So, rather than saying anything popped into existence you are saying that the energy was already there before inflation started.. Is that correct ?
    Far away is close at hand in images of elsewhere...

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    Quote Originally Posted by trinitree88 View Post
    We have nothing to explain why the observed excess of matter...the world we see...over antimatter...exists. It is one of the great unanswered questions in science.
    pete
    Yes, that's what I thought you meant. (The original sentence read as if there was no evidence for an excess of matter, whereas (obviously) we see an excess of matter.)

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    Quote Originally Posted by kevin1981 View Post
    So, rather than saying anything popped into existence you are saying that the energy was already there before inflation started.. Is that correct ?
    Yes, that is right. Even in more speculative variants of loop quantum gravity that propose spacetime generation it generally represents a reconfiguration of the system and repartition of energy rather than it magically appearing. The closest to it appearing I've seen is related to the emergence of causal structure, before which energy is poorly or undefined.

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    Quote Originally Posted by trinitree88 View Post
    We have nothing to explain why the observed excess of matter...the world we see...over antimatter...exists. It is one of the great unanswered questions in science.
    While the level of CP violation required is not observed your characterisation of the current state of knowledge overstates our level of ignorance. Symmetry is not preserved, we see weak force CP violations at quite high levels in B masons and in smaller amounts in K masons. What we have not observed are either the levels of CP violation required for indirect weak force mechanisms to generate the observed asymmetry or significant strong force CP violations that would directly lead to what we see. However we know CP violation is possible and in fact happens. So we do have something. We also know that we don't have a great handle on the very early, very high energy processes.

    So you are right it is an open mystery, and an exciting area of study. But we have related, relevant phenomenology to study and evidence that nature can be biased one way or the other.

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    I've just spent an hour reading about inflation. I didn't realise up till now that even inflation starts with a large amount of potential energy. I thought that energy just fluctuated into existence !

    What i find perplexing is where did the initial potential energy come from.. I guess some people will say that energy can not be created or destroyed so it is infinite and
    has always existed. I guess it is either that or energy just came into being from nothing..

    Quote Originally Posted by Shaula View Post
    The closest to it appearing I've seen is related to the emergence of causal structure..
    What do you mean by this, could you elaborate please..
    Far away is close at hand in images of elsewhere...

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    Quote Originally Posted by kevin1981 View Post
    What i find perplexing is where did the initial potential energy come from.. I guess some people will say that energy can not be created or destroyed so it is infinite and has always existed. I guess it is either that or energy just came into being from nothing..
    We don't know. Simple as that, I am afraid. We don't even know if the energy had to come from somewhere because we are nowhere near a theory they reached back that far. And if it did where did whatever created that come from, etc etc etc oh look, a turtle. It is not even known if it is possible to know when we have reached t=0 with a model, or whether it will always be possible there was something before our best start point. I tend not to worry about understanding 'the beginning', I just focus on how far back theories can reach.

    Quote Originally Posted by kevin1981 View Post
    What do you mean by this, could you elaborate please..
    Well, under some forms of Causal Dynamical Triangulation there are states that may have existed before spacetime did, where the causal rules (and hence time and/or space as we understand it) didn't exist. Describing that state and how it could lead to the generation of spacetime is part of the challenge of CDT. Via Noether's theorem energy conservation is linked to a particular kind of time symmetry. So if the symmetry group of time were different or non-existent under the pre-spacetime it is likely that the concept of energy or at least its conservation might not be there early on. So if this (highly speculative) extension to the SM does imply this you'd see energy move from an undefined or poorly defined concept to a conserved quantity with the emergence of spacetime.

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    Thanks Shaula, that is a very interesting post and i have been reading about Causal Dynamical Triangulation and time symmetry today, also i've been watching youtube videos on the subjects..
    Far away is close at hand in images of elsewhere...

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    So basically, inside the universe if time has a symmetry then energy must be conserved..

    However before the big bang, time may not of had any meaning so there is no need for any conservation of energy..

    So it’s plausible that a massive amount of energy could fluctuate into existence from nothingness and not break any conservation laws….
    Far away is close at hand in images of elsewhere...

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    Quote Originally Posted by kevin1981 View Post
    So basically, inside the universe if time has a symmetry then energy must be conserved..

    However before the big bang, time may not of had any meaning so there is no need for any conservation of energy..

    So it’s plausible that a massive amount of energy could fluctuate into existence from nothingness and not break any conservation laws….
    Yes, with a bunch of caveats! CDT is still not a developed theory. It is one of a bunch of alternative ideas for extending physics beyond the standard model. And both the terms nothingness and fluctuate would need to be more precisely defined in terms of a more complete CDT theory.

    But yes, apart from those caveats this is an example of how apparent issues with energy conservation might pan out. I'll also add - the fact that you went and did your own research on these topics and followed up what interested you is so refreshing! It's a really good habit to have. There is so much good material out there by people who know the topic better than me, you'll get a much more rounded answer this way.

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