We study a dynamic boundary, e.g. a mobile impurity, coupled to N independent Tomonaga-Luttinger liquids (TLLs) each with interaction parameter K. We demonstrate that for N>2 there is a quantum phase transition at K>1/2, where the TLL phases lock tog
ether at the particle position, resulting in a non-zero transconductance equal to e^2/Nh. The transition line terminates for strong coupling at K=1- 1/N, consistent with results at large N. Another type of a dynamic boundary is a superconducting (or Bose-Einstein condensate) grain coupled to N>2 TLLs, here the transition signals also the onset of a relevant Josephson coupling.
We study zero temperature spin dynamics of a particle confined to a ring in presence of spin orbit coupling and Ohmic electromagnetic fluctuations. We show that the dynamics of the angular position $theta(t)$ are decoupled from the spin dynamics and
that the latter is mapped to certain correlations of a spinless particle. We find that the spin correlations in the $z$ direction (perpendicular to the ring) are finite at long times, i.e. do not dephase. The parallel (in plane) components for spin $half$ do not dephase at weak dissipation but they probably decay as a power law with time at strong dissipation.
