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As far as I understand, it is understood that throughout the universe there exists, what is known as, a quantum field from which, due to its fluctuations, temporary (pairs of) virtual particles continuously appear in a random, unpredictable (or should I say probabilistic?) fashion.

For my idea to have any viability, I am assuming that this quantum field is an intrinsic part of reality, that existed "before" or rather at the time of the Big Bang already. Is this a correct assumption? Or is it believed that this quantum field was "formed" at the time, or perhaps even later than, the moment of the Big Bang? I hope not.

Assuming the former, and also understanding that those pairs of virtual particles typically annihilate each other almost instantaneously, but sometimes actually create real particles — for instance in Hawking radiation — is it a far stretch to think that the Big Bang was possibly started by the highly improbable (but in an "infinite" timespan of underlying reality, likely to occur), cataclysmic event of a huge amount of virtual particle all appearing, either "at the same time", or in such a sequential manner, that they couldn't annihilate each other anymore and were destined to actually form large quantities of real particles?

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I tried really hard to understand what you're asking and what's going on in your mind in general. I have no chance. First, a quantum field is a description of natural phenomena, the basic object in a theory, and of course it exists everywhere and since the beginning if the theory is right. The quantum field theory was ultimately invalid too early after the Big Bang, for a short time, and had to be replaced by string theory whose basic blocks aren't quantum fields, at least not when you calculate it exactly. –  Luboš Motl Dec 9 '12 at 5:59
    
Now, virtual particles aren't real particles, that's why we call them virtual, which is why it makes no sense to talk about their presence in the spacetime at a given moment. One may only talk about the presence of the real particles. A virtual particle is a part of a history in the middle of it, when it's not measured, and it contributes to the evolution of real particles, but one can't associate them with any "objective state" of the system or with any measurement. –  Luboš Motl Dec 9 '12 at 6:01
    
Otherwise there have been many severe, extreme, and even cataclysmic events in the history of the Universe, lots of particles almost entirely annihilated, and so on, and so on, but why do you need to mix these things with notions - such as quantum fields and virtual particles - whose meaning is totally clearly completely incomprehensible to you? Isn't it a better idea to only use words whose meaning is actually clear to you? –  Luboš Motl Dec 9 '12 at 6:03
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@LubošMotl Perhaps I'm in over my head here, but, concerning your first response: are you saying that quantum field theory is not a viable theory (anymore?) and that it is replaced by string theory? (I'm not following what you are trying to say here.) Secondly: I think I understand your remark about virtual particles vs. spacetime. But, if it is believed that virtual particles can account for the loss of mass of black holes (due to Hawking radiation) by creating real particles, why wouldn't virtual particles also be able to create real particles at the time of the Big Bang? –  fireeyedboy Dec 9 '12 at 6:23
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@fireeyedboy What Luboš means is run-of-the-mill, vanilla QFT is not the end-all, be-all of physics, and it is commonly accepted that it, like most of our theories, fails to be an accurate description of nature too close to the Big Bang; string theory may very well do better. That said, I think this is a valid question despite any potential misconceptions, though maybe it takes one person who's used to having misconceptions to understand another :) –  Chris White Dec 9 '12 at 7:30
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The idea that the universe is a vacuum flucuation has been around a long time. The first public mention of the idea I know of is from Edward Tryon in 1973, but I bet it had been discussed long before that. Do you have access to old copies of Nature? If so have a look at "Is the Universe a Vacuum Fluctuation?" by Edward Tryon, Nature 246, 396 - 397 (14 December 1973).

Alexander Vilenkin developed the idea further in 1982, and his paper is available online at http://mukto-mona.net/science/physics/a_vilinkin/universe_from_nothing.pdf.

The bottom line is that we don't understand the physics well enough to know if there is any foundation to these ideas, and no-one has come up with any experimental way to test them. I should note that the various theories of quantum gravity have come up with scenarios in which the universe wasn't created at the Big Bang but has existed (potentially at least) forever. From String Theory we have the ekpyrotic universe, and from loop quantum cosmology the idea that there might have been a Big Bounce.

I suspect most physicists would regard the question as philosophy rather than physics.

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Thank you — very interesting. This got me thinking: how does Lawrence Krauss' idea, of a universe from nothing, stack up against Tryon/Vilenkin's ideas? Are Krauss' ideas also rooted in quantum-field theory? And are they approached from a similar angle as Tryon and Vilenkin's ideas? Or is Krauss coming at it from a whole other angle? –  fireeyedboy Dec 9 '12 at 20:57
    
I actually found the answers in this talk by Lawrence Krauss already. –  fireeyedboy Dec 10 '12 at 0:00
    
Ah, thanks, that looks an interesting talk. –  John Rennie Dec 10 '12 at 7:39
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