Universal conductance fluctuations in noninteger dimensions

We propose an ansatz for universal conductance fluctuations in continuous dimensions from 0 up to 4. The ansatz agrees with known formulas for integer dimensions 1, 2, and 3 for both hard wall and periodic boundary conditions. The method is based solely on the knowledge of energy spectrum and standard assumptions. We also study numerically the conductance fluctuations in four-dimensional Anderson model, depending on the system size L and disorder W. We find a small plateau with a value diverging logarithmically with increasing L. Universality disappears just in four dimensions (4D).