(a) For the purposes of this section, “cohabiting” means the act of two adults dwelling together continually and habitually in a private heterosexual or homosexual relationship, even if the relationship is not solemnized by marriage, evidenced by the voluntary mutual assumption of those marital rights, duties, and obligations that are usually manifested by married individuals, and which include, but are not necessarily dependent on, sexual relations.
(b) Any decree of divorce providing for periodic payments of alimony shall be modified by the court to provide for the termination of the alimony upon petition of a party to the decree and proof that the spouse receiving alimony has remarried or that the spouse is cohabiting with another individual.