Field-Theoretic Variational Perturbation Theory
allows for the
arbitrarily precise calculations of strong-coupling
of quantum field theories.
In particular, it enables one
to find critical exponents
near second-order phase transitions
in a simple way
without using renormalization group theory.
It makes essential use of the Wegner exponent
governing the approach to scaling
(which Pade and Pade-Borel methods are unable to do)
and determines it with high accuracy.
is based on an essential extension of the original
the Peierls inequality was abandoned in order to
expansions of any order. This turns divergent weak-coupling expansions
strong-coupling expansions. The convergence is mostly exponentially
are described in Chapter 5 of my textbook
a simple trick was found to accommodate
dimensions of quantum field theory. The result is
which has led to the
reliable results of strong-coupling
of field theories so far.
most-accurately measured strong-coupling property is the critical exponent
that governs the singularity of
the specific heat of superfluid helium,
was performed with great effort in amicrogravity environment
a satellite by
and collaborators. This experiment
textbook on this subject
Properties of phi^4 Theories.