My research spans across theoretical physics, currently focusing on the intersection of mesoscopic quantum many-body physics, open quantum systems, and the foundations of quantum mechanics. I am fundamentally driven by a unifying theme: the physics of emergence. Whether exploring how robust classical-like behavior arises from a unitary quantum substrate or how macroscopic spacetime phenomena emerge from extra-dimensional physics, my goal is to understand how collective effects and symmetries shape complexity across widely different scales.
Current Focus: Mesoscopic Quantum Physics and Coherence
My recent work addresses a central question in quantum foundations: under what precise, quantitative conditions can a collective quantum system exhibit signatures of coherence that are irreducibly non-classical, and how do such signatures degrade under realistic environmental noise?
Much of this research is anchored in the Lipkin-Meshkov-Glick (LMG) model, a paradigmatic exactly solvable system capturing the essential physics of a quantum phase transition with a discrete Z_2 symmetry. Realized experimentally in platforms like spinor Bose-Einstein condensates, this model provides a clean theoretical laboratory to test the limits of macrorealism and develop falsifiable quantum-classical discriminators. My recent contributions have established several key results.
First, regarding basis-dependent decoherence in symmetry-broken phases, I have shown that in the ordered phase of a Z_2-symmetric collective spin system, Lindblad dephasing rates differ fundamentally depending on the basis. The coherence between energy eigenstates decays more slowly than the coherence between localized pointer states by a universal factor approaching 2 (and reaching up to roughly 2.42 near the quantum-critical crossover). This discrepancy has a strict algebraic origin, as parity forces the cross-term to zero, providing distinct protection factors over classical mean-field estimates.
Second, I explored violations of macrorealism by deriving strict, level-by-level dephasing thresholds for Leggett-Garg inequality violations in mesoscopic systems. This revealed a three-tier hierarchy culminating in a robust, experimentally accessible violation (K_3 approximately equal to 1.32) that is immune to T_1 population mixing and protected by an emergent parity symmetry.
These results carry direct implications for quantum metrology, spin squeezing, and experimental protocols operating within symmetry-protected ground-state doublets.
Stavros Mouslopoulos (May 1, 2026) e-Print: 2605.00952 [quant-ph]
Classically Forbidden Signatures of Quantum Coherence in the Mesoscopic Lipkin-Meshkov-Glick Model
Stavros Mouslopoulos (Apr 19, 2026) e-Print: 2604.18638 [quant-ph]
Foundational Past Work: Brane-World Cosmologies and Modified Gravity
This deep interest in emergent multi-vacua structures, phase transitions, and symmetries has its roots in my early, extensive work in high-energy theoretical physics at Oxford University, under the supervision of Graham Ross and Ian Kogan. There, our research explored the phenomenological consequences of string-theory-inspired brane-world scenarios, multilocalization, and the modification of gravity at large scales. A significant portion of my past research involved the theoretical consistency of massive gravity and multi-gravity (bigravity) systems. A notable breakthrough was circumventing the vDVZ discontinuity. One of the most severe obstacles in massive gravity was the van Dam-Veltman-Zakharov theorem, which dictates that the extra polarization states of a massive graviton do not decouple in the massless limit in flat space, conflicting with General Relativity. We proved that by considering gravity in a constantly curved spacetime background, specifically de Sitter or Anti-de Sitter space, one can smoothly circumvent this theorem. We established that the massless limit is restored if the Hubble parameter tends to zero slower than the mass of the graviton.
Ian I. Kogan(Oxford U.), Stavros Mouslopoulos(Oxford U.), Antonios Papazoglou(Oxford U.) (Nov, 2000)
Published in: Phys.Lett.B 503 (2001) 173-180 e-Print: hep-th/0011138 [hep-th]
A New bigravity model with exclusively positive branes
Ian I. Kogan(Oxford U.), Stavros Mouslopoulos(Oxford U.), Antonios Papazoglou(Oxford U.) (Nov, 2000)
Published in: Phys.Lett.B 501 (2001) 140-149 e-Print: hep-th/0011141 [hep-th]
Teaching
I’ve had the opportunity to study and teach in a variety of academic environments across different countries. I completed my PhD in Theoretical High Energy Particle Physics at Oxford University, which set the foundation for my academic career. Alongside this, I hold a Bachelor's degree in Physics from the University of Ioannina, Greece, and a Diploma in Education from the University of New South Wales, Australia. Over the years, I’ve taught mathematics and physics in various international settings, including foundation colleges like Kaplan International College London, ONCAMPUS University of Southampton, and now the University of Nottingham Ningbo, China. My exposure to different educational systems—such as those in Greece, the UK, the USA, Australia, and international programs has helped me adapt to a wide range of student and curriculum needs. Before transitioning into teaching, I worked as a researcher at Los Alamos National Laboratory and Lawrence Berkeley National Laboratory in the USA, focusing on theoretical particle physics. This research experience has greatly influenced the way I teach, encouraging a deep, analytical approach to learning.