When Kurt Cobain was in his prime, there was little doubt what alternative music was. Twenty years after Cobain’s death, Wall Street is in the midst of its own alternative craze, and almost any asset can be called alternative, as long as it’s not a traditional stock or bond. Almost half of the mutual funds called “alternative” by Bloomberg have launched since 2011, and Boston Consulting Group estimates alternative assets have risen from $2 trillion to $7 trillion in the last decade. Regulators have asked big alternative asset managers including BlackRock Inc.