Exceptional Cones from an Indefinite Bogoliubov Metric in Hyperbolic Polariton Condensates
Long-wavelength Bogoliubov phonons in an ordinary condensate realize the standard acoustic Lorentz metric. We show that a condensate formed in a hyperbolic polariton band realizes a different collective geometry with an indefinite Bogoliubov metric whose spatial signature is inherited from the opposite signs of the band curvatures. This metric converts the acoustic light cone into a hyperbolic stability wedge, separating propagating quasiparticles from dynamically unstable ones. In a driven-dissipative condensate, gain saturation turns this metric relation into a non-Hermitian Bogoliubov dispersion. The zero-discriminant surface becomes an exceptional cone in the parametric space $(q_x,q_y,Δ_{\rm NH})$, appearing as an exceptional hyperbola at fixed gain saturation. Across this surface the Bogoliubov branches coalesce, the biorthogonal phase rigidity collapses, and the spectrum changes from propagation to amplified or overdamped dynamics. Our results identify hyperbolic polariton condensates as a controllable setting where non-Hermitian exceptional degeneracies are organized by an effective Bogoliubov metric.