My primary research activities belong to the general fields of Theoretical Astrophysics and Cosmology, Theory of Gravitation,
Statistical Mechanics. They may be summarized as follows: statistical mechanics and thermodynamics of gravitational interaction, Newtonian and relativistic; stability, structure, and dynamics of relativistic compact stars; stellar and galaxy clusters, black hole subclusters, and the dark sector.
 Selected Publications

 Zacharias Roupas, "Gravitational Brownian motion as inhomogeneous diffusion: black hole populations in globular clusters", Astronomy and Astrophysics, 646, A20 (2021)
 Zacharias Roupas, "Relativistic Gravothermal Instabilities", Classical and Quantum Gravity, 32, 135023 (2015)
 Zacharias Roupas and Demosthenes Kazanas, "Generation of massive stellar black holes by rapid gas accretion in primordial dense clusters", Astronomy and Astrophysics, 632, L8 (2019)
 Zacharias Roupas, "Statistical Mechanics of Gravitational Systems with Regular Orbits: Rigid Body Model of Vector Resonant Relaxation", Journal of Physics A: Mathematical and Theoretical, 53, 045002 (2020)
 Zacharias Roupas, Bence Kocsis and Scott Tremaine, "Isotropic–Nematic Phase Transitions in Gravitational Systems", The Astrophysical Journal, 842, 90 (2017)
 Zacharias Roupas, "Thermodynamical instabilities of perfect fluid spheres in General Relativity", Classical and Quantum Gravity, 30, 115018 (2013)
 Zacharias Roupas, "Thermal Mass Limit of Neutron Cores", Physical Review D, 91, 023001 (2015)
 Zacharias Roupas, “Gravitational Potential from Maximum Entropy Principle”, Classical and Quantum Gravity, 37, 097001, (2020)
 Zacharias Roupas, Minos Axenides, George Georgiou, and Emmanuel N. Saridakis, "Galaxy clusters and structure formation in quintessence versus phantom dark energy Universe", Physical Review D, 89, 083002 (2014)
 Zacharias Roupas, "Phase space geometry and chaotic attractors in dissipative Nambu mechanics", Journal of Physics A: Mathematical and Theoretical, 45, 195101 (2012)