Canonical basis and homology of local systems

Using the isomorphism between highest weight U_q(sl_2)-modules and homologies of certain local systems on the configuration spaces, constructed by Varchenko, we give a geometric construction of the dual of the Lusztig's canonical basis in a tensor product of irreducible finite-dimensional U_q(sl_2)-modules.Comment: 21 pages, AMSTeX; many figures, require epsf macro packag

Knapsack problems in products of groups

The classic knapsack and related problems have natural generalizations to arbitrary (non-commutative) groups, collectively called knapsack-type problems in groups. We study the effect of free and direct products on their time complexity. We show that free products in certain sense preserve time complexity of knapsack-type problems, while direct products may amplify it. Our methods allow to obtain complexity results for rational subset membership problem in amalgamated free products over finite subgroups.Comment: 15 pages, 5 figures. Updated to include more general results, mostly in Section

Entanglement Edge Modes of General Noncommutative Matrix Backgrounds

We explore the structure of entanglement edge modes on noncommutative backgrounds that arise from matrix quantum mechanics. For the fuzzy sphere, despite nonlocality and UV/IR mixing, we find area law behavior in the dominant $U(N)$ representations governing the state of the edge modes. For general noncommutative backgrounds with no global symmetry, nonlocal effects resum into a smoothly varying coupling constant that deforms the metric to a different frame. The effect is analogous to the relationship between string frame and Einstein frame in string theory.Comment: 35 pages, 11 figures, one appendi

Friction, Free Axes of Rotation and Entropy

Friction forces acting on rotators may promote their alignment and therefore eliminate degrees of freedom in their movement. The alignment of rotators by friction force was demonstrated by experiments performed with different spinners, demonstrating how friction generates negentropy in a system of rotators. A gas of rigid rotators influenced by friction force is considered. The orientational negentropy generated by a friction force was estimated with the Sackur-Tetrode equation. The minimal change in total entropy of a system of rotators, corresponding to their eventual alignment, decreases with temperature. The reported effect may be of the primary importance for a phase equilibrium and motion of ubiquitous colloidal and granular systems.Comment: 10 pages, 7 image