THE ANDERSON TRANSITION IN A MODEL OF COUPLED RANDOM POLYMER-CHAINS

We obtain by transfer matrix scaling methods the Anderson metal-insula tor phase diagram for a random electronic tight binding Hamiltonian, m odelling a 'spaghetti' of random polymer chains having randomly placed cross-links J with concentration c. If J is small and c is large the results depend on the product J . c as predicted by a mean-field appro ach. For large J and small c this dependence breaks down as a result o f the large off-diagonal disorder introduced by the random cross-linki ngs. The localization length critical exponent in this highly anisotro pic model takes the universal three-dimensional value v = 1.3 +/- 0.2.