Actually, it's not a "free lunch" and it's not classical thermodynamics.

First you need to understand the concept of a "False Vacuum."

I recommend this for historical background on the concept of vacuum in quantum field theory:

http://wlap.physics.lsa.umich.edu/umich ... l/f001.htm

And from Okun's historical paper:

Being a student of Isaak Pomeranchuk I first heard from him in 1950: “The

vacuum is filled with the most profound physical content” ...

It is paradoxical, but it took many years before the first paper appeared

in which it was proven that it should be (not in a mathematical way, but in

physical, by Yakov Zeldovich). If you have quantum mechanics, then there

must be in the framework of general relativity a cosmological term due to

virtual particles. In other words, due to zero state quantum oscillations.

Zeldovich was the first who published estimates of the cosmological term.

His first estimate was that it must be more than 120 orders of magnitude

larger than the upper limit on it.

...

What does it mean: the Universe can tunnel? Assume that at a given

place you have the upper vacuum; then you will gain energy, if you go at

that place to the lower vacuum. Thus, at first sight a simple question arises:

Why not to go to a lower vacuum here and now? The answer is that between

two vacua there is a wall which I’ve already described before: a material

wall, very heavy, very dense. You need energy to create it. Therefore there

exists a critical radius Rc at which the gain in energy in volume of a bubble

is becoming larger than the loss of energy used for creation of the surface of

the bubble.

It was a very frightening experience which I had when I first thought

about these bubbles. I thought about the possibility that at some collider

the collision of two particles would enhance the probability of creating such

a microbubble. And if a bubble of critical dimension is produced, then it

can expand infinitely, because the volume energy goes like r3 and the surface

energy – like r2. Thus, for large r volume will predominate. And very soon

the wall of the bubble would move with a velocity of light, and the bubble

would expand and destroy the whole world. I really shivered when I thought

about this. But then I somehow relaxed by thinking about the past: that

Universe was hot, there was a lot of various collisions in it. Therefore if

bubbles could be produced by collisions, then they already were produced

and we are living in a true vacuum now.

A few months later I told Andrei Sakharov about these bubbles. I vividly

remember his reaction. He said: “Such theoretical work should be forbidden.

It’s too dangerous”. I tried to persuade him with arguments about past of

the Universe and all that. And he said: “Nobody had collided two lead nuclei

in the Universe”. I took this quite seriously.

The notion of a false vacuum with large energy density (VEV) naturally led

Alan Guth [68] to the idea of inflationary universe (1980). The exponential

expansion solves the problems of flatness and the horizon as well as homogeneity

and isotropy problems. It also explains the vanishing abundance of

magnetic monopoles.

Papers:

http://arxiv.org/abs/hep-ph/0112031

http://arxiv.org/abs/hep-ph/0112032