# Neil Turok: all known physics fits into one equation

1. Jul 20, 2012

### g.lemaitre

In this lecture which is quite good in my opinion

Neil Turok claims that all known physics fits into this equation:

What is this equation's name? When was it cobbled together and by whom? How confident are you of its predictive power? Do all known physical laws reduce to this equation? Even such laws as the ideal gas equation, Bernoulli's equation and the law which causes liquid water to be denser than ice? I won't bother to understand the finer points of the equation since I barely understand QM much less QED.

Last edited by a moderator: Sep 25, 2014
2. Jul 20, 2012

### Staff: Mentor

3. Jul 21, 2012

### sheaf

The term being exponentiated is an action, containing representatives of all the currently used coupling types. You've got the Einstein-Hilbert action, plus the various component types of the SM action. He's just picked out one term of each type to illustrate the variety of couplings.

Exponentiating $\frac{i}{\hbar}$ times the action gives you the path integral.

4. Jul 21, 2012

### g.lemaitre

But this equation doesn't have a name? Is it his equation?

5. Jul 21, 2012

### Dickfore

It is the Feynman path integral for the moment-generating function Z.

6. Jul 21, 2012

### Staff: Mentor

The addition of gravity there is a bit speculative - even if it works like this, no one has an idea how to work with it.

I think that "all known physics" refers to "all known particle physics" - this equation cannot be used to explain the properties of dark matter, for example.

7. Jul 21, 2012

### w4k4b4lool4

Part of the equation you quote, i.e. all terms apart from the one containing R, is (when the terms are interpreted appropriately) the definition of the STANDARD MODEL of particle physics. The last two terms are associated to the very celebrated HIGGS, $\varphi$, and in fact there is a $\varphi$ also in most of the other terms but it is not displayed explicitly. This is the theory that has been tested to remarkable accuracy in particle accelerators and beyond .. well apart from the unexplained 96% of "our" universe (dark energy and dark matter). Theory of everything? Nah, probably not then ... but who knows, there can be surprises. The other part of the equation, the one containing R, doesn't make much sense as it stands .. at the end of the day, to make sense of it is to make sense of quantum gravity. And it's not often that you see the words sense' and quantum gravity' in the same sentence .. By the way, when you minimize the exponent of this equation, you get classical physics: Maxwell's equations, Newtonian gravity, time dilation, and .. ehmm.. I'm not sure what a classical fermion is .. what is a classical fermion? Anyway, that's the exponent. The big' integral upfront instructs one to sum over all conceivable paths when a particle goes, say, from a point A in spacetime to a point B. This big' integral is what defines it as a quantum theory, in accordance with Feynman's formulation of quantum mechanics.

8. Jul 21, 2012

### arivero

A trick to understand the equation is to be aware that h is small. If you remember delta functions, they have a very similar shape, as the limit with something goes to zero of a complex-valued exponential. In this case, the "delta function" is more of a "delta prime", and it codifies classical mechanics in its limit, while the h>0 case is quantum mechanics.