Two talks on a tentative theory of large distance physics

These talks present an overview of a tentative theory of large distance physics. For each large distance L (in dimensionless units), the theory gives two complementary descriptions of spacetime physics: quantum field theory at distances larger than L, string scattering amplitudes at distances smaller than L. The mechanism of the theory is a certain 2d nonlinear model, the λ-model, whose target manifold is the manifold of general nonlinear models of the worldsurface, the background spacetimes for string scattering. So far, the theory has only been formulated and its basic working described, in general terms. The theory’s only claims to interest at present are matters of general principle. It is a selfcontained nonperturbative theory of large distance physics, operating entirely at large distance. The λ-model constructs an actual QFT at large distance, a functional integral over spacetime fields. It constructs an effective background spacetime for string scattering at relatively small distances. It is background independent, dynamically. Nothing is adjustable in its formulation. It is a mechanical theory, not an S-matrix theory. String scattering takes place at small distances within a mechanical large distance environment. The λ-model constructs QFT in a way that offers possibilities of novel physical phenomena at large distances. The task now is to perform concrete calculations in the λ-model, to find out if it produces a physically useful QFT. These talks present an overview of a tentative theory of large distance physics [1]. This written version of the talks differs from the actual spoken version in its arrangement and in some of the content. The transparencies that were used in the actual talks are available at [2]. References can be found in [1]. No references will be given here. The need to produce QFT My goal is a theoretical machinery capable of producing a definite, specific spacetime quantum field theory. Everything, or almost everything, that is presently known about the laws of physics is summarized in the Standard Model of particle physics combined with General Relativity. General Relativity is a classical field theory, but it can just as well be regarded as a cutoff quantum field theory which we observe only in its large distance, classical regime. From this point of view, almost everything that is presently known about the laws of physics is summarized in one particular quantum field theory. An enormous body of experimental data is summarized in this amazingly successful QFT. Since the establishment of the Standard Model, theoretical speculation has lacked the guidance and correction of a rapid flow of new experimental results. Speculative exploration of large theoretical search spaces with many free parameters could drag on forever without such guidance and correction. We urgently need a theory that is definite and specific. We need a theory that gives a definite and specific explanation of the Standard Model combined with General Relativity, so its reliability will be supported securely by the body of existing experimental knowledge. To have a chance of explaining the Standard Model and General Relativity, a theory must first be capable of producing a QFT. It is not enough merely to identify a QFT, say by matching to an S-matrix. An S-matrix is not a mechanics. An actual QFT must be constructed. The theoretical machinery must produce a quantum mechanical space of states and a hamiltonian operator or, equivalently, a functional integral over spacetime fields, cut off perhaps at an unnoticeably small spacetime distance. My strategy has been to look first for a well-defined theoretical machinery that is capable of producing a specific spacetime QFT, without assuming in advance that QFT operates. The spacetime fields of the QFT should include the spacetime metric, some gauge fields, and some chiral fermion fields. The dynamics should be generally covariant and gauge invariant. But otherwise I have postponed worrying about the details of the QFT that is produced. Until now, I have only been concerned with the problems of formulating a theory. The task now is to figure out what the theory does, and eventually to check whether it does in fact produce the Standard Model plus General Relativity, in all known details. If it fails to do so, then of course the theory is wrong.