PHYSICAL TESTS FOR RANDOM NUMBERS IN SIMULATIONS

We propose three physical tests to measure correlations in random numb ers used in Monte Carlo simulations. The first test uses autocorrelati on times of certain physical quantities when the Ising model is simula ted with the Wolff algorithm. The second test is based on random walks and the third on blocks of n successive numbers. We apply the tests t o show that recent errors in;high precision Ising simulations using ge neralized feedback shift register algorithms are due to short range co rrelations in random number sequences.