COLLECTIVE MOTION OF MICROORGANISMS FROM FIELD-THEORETICAL VIEWPOINT

We analyze the collective motion of micro-organisms in the fluid and c onsider the problem of the red tide. The red tide is produced by the c ondensation of the micro-organisms, which might be similar to that of the strings. We propose a model of the generation of the red tide. By considering the interaction between the micro-organisms mediated by th e velocity fields in the fluid, we derive the Van der Waals type equat ion of slate, where the generation of the red tide can be regarded as a phase transition from the gas of micro-organisms to the liquid.