We study a particle on a ring in presence of various dissipative environments. We develop and solve a variational scheme assuming low frequency dominance. We analyze our solution within a renormalization group (RG) scheme to all orders which reproduces a 2 loop RG for the CaldeiraLegget environment. In the latter case the Aharonov-Bohm (AB) oscillation amplitude is exponential in −R 2 where R is the ring's radius. For either a charge or an electric dipole coupled to a dirty metal we find that the metal induces dissipation, however the AB amplitude is ∼ R −2 for large R, as for free particles. Cold atoms with a large electric dipole may show a crossover between these two behaviors.PACS numbers: 73.23. Ra, The problem of interference and dephasing in presence of dissipative environments is of significance for a variety of experimental systems and a fundamental theoretical issue. The experimental systems include mesoscopic rings embedded on various surfaces where Aharonov-Bohm (AB) oscillations can be measured 1,2 , and the related problem of decoherence at low temperatures 3 . A different type of experimental systems are cold atom traps created by atom chips 4,5,6 , or trapped excited atoms with huge electric dipoles 7 . The atom chip that produces a magnetic or electric trap for the cold atoms necessarily also produces noise. Our problem is then relevant for evaluating the interference amplitude of cold atoms or molecules in presence of such noise.As an efficient tool for monitoring the effect of the environment we follow a suggestion by Guinea 8 to find the AB oscillation amplitude as function of the radius R of the ring, as measured by the curvature 9,10 1/B c of the ground state energy E 0 at external flux φ x = 0, i.e. 1/B c = ∂ 2 E 0 /∂φ 2 x | 0 . For free particles of mass M this amplitude is the mean level spacing ∼ 1/M R 2 . Two types of environments were suggested to lead to an anomalous suppression, i.e. a stronger decrease of the oscillation amplitude than 1/R 2 : system (i) is that of a Caledeira Legget bath and system (ii) of a charge in a dirty metal environment.System (i) is relevant to the Coulomb blockade problem 9,10,11,12 as well as to quantum dots at a distance from metallic gates 13 . This problem has been extensively investigated by instanton methods 14,15,16,17 , by RG methods 8,9,18 , and by Monte Carlo (MC) methods 9,10,19 . All methods show that B c increases exponentially with the dissipation strength α, i.e. B c ∼ α −µ e π 2 α , with differences in the exponent µ. In 2nd order renormalization group 9 (RG) µ = 2 , real time RG gives 18 µ = 6.5, instanton methods give either 14 µ = 2 or 15,17 µ = 3, or 16 µ = 4, while MC suggests 19 µ = 5. This system was also studied by a variational approach 21 which was solved numerically showing a nonperturbative regime at strong α. Since α = γR 2 where γ is a friction coefficient, a length scale π/ √ γ is identified 8 , beyond which the AB oscillations decay.The system (ii) was investigated by RG methods 8 finding B c ∼ R 2+µ ′ with µ ′ 1 nonunivers...