Within the realms of metal, few bands are more esoteric and left-brained than Meshuggah.

These Swedes make music for clinically minded deconstructionists, and one really has to reduce Meshuggah's sound to its individual elements before seeing the overall picture.

Nothing, their fourth full-length slab, only further cements their place as masterminds of cosmic calculus metal -- call it Einstein metal if you want -- and, to their credit, they're really the only ones to fall into said sub-subgenre.

When odd riff cycles, robotic death vocals, neo-jazz chromatics, and mathematical songwriting are your primary weapons, it would seem easy to paint yourself into a corner creatively -- so where is Meshuggah to go after Destroy Erase Improve, the band's powerful statement of intent, and its follow-up, the suffocatingly violent and clattery Chaosphere? Well, besides being heavier -- guitarists Marten Hagstrom and Fredrik Thordendal used eight-string guitars to give extra growl to their off-kilter, occasionally dissonant chording -- the appropriately titled Nothing boasts more spacious arrangements, the jarring tempo and time shifts colliding with each other until the songs collapse on themselves like black holes (see "Glints Collide" and the seven-plus minutes of "Closed Eye Visual").

From there, light bends into "Nothing," the theme of the record rooted in existentialism and the psychic trauma it causes on the brain -- and so goes the cranium stretching, through "Straws Pulled at Random," "Spasm," and the creepily invigorating lunar strains of "Obsidian," all being anti-melodic, teeth-grinding jaunts into opaque mathematical regions, importing small amounts of Tool's psychedelia into the group's Death-by-way-of-Gang of Four sonic maelstrom.

Nothing truly gives new meaning to the word heavy, redefining boundaries by pushing metal into the realms of abstract science; for those lucky enough to be tuned into Meshuggah's unique wavelength, the album, like all good art, tickles the subconscious while probing both the internal (the mind) and the external (space).

And when Meshuggah explores, it's into uncharted territory.

If only more metal bands could be so daring.