Wormholes connecting more than two universes: new exact solutions

Using a mathematical technique called the Harrison transformation, the authors built exact wormhole solutions in Einstein-Maxwell theory that stitch together 2, 4, 6, or any even number of asymptotically flat universes — far beyond the usual two-mouth picture. Each solution is pinned down by mass, two types of charge, scalar charge, and sheet count, with the throat size fixed by regularity. Regular solutions survive even outside the parameter region the construction method naively requires, hinting at a richer solution space than previously known.