[Vijay writes to say that Paul McAuley's novel Eternal Light (1993) has similar themes, but may not deserve its own separate listing here. In particular, he says]: This hard-SF novel describes a million-year old war between the survivors of an ancient civilization and the "marauders"; caught in the cross-fire are all the budding civilizations in the galaxy [Fermi's paradox is given special treatment in the novel]. And then there are the "Angels" - enigmatic, transcendental beings who want to stop the marauders from using the Angel-technology left behind in the corporeal universe since the technology enables "contginuous creation", the art of creating new matter using energy siphoned off from other universes of the multiverse. Their weapon of choice for this? Mathematics, of course. Here're some descriptions of these weapons (quite reminsicent of the language in Schachner's "The Living Equation"):

“[The weapons were] a little like the infolded dimensionless webs which had wrapped suns before they had flared, stuff that intersected at odd angles with the familiar dimensions of the quotidian universe, weapons stripped down to pure mathematics, idea become word become deed…[…] the abstract weapon of the angels”

“I wish I knew more about the weapon they gave you. Always I have dreamed of being able to see an equation…” [The weapon looks] like burning diamond dust. Like Light. […] The ultimate machine, a mathematical equation that operates on the virtual universe.”