Publications

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In Preparation

1. Unifying deterministic and stochastic thermodynamic speed limits on observables
   Swetamber Das and Jason R. Green
2. Classical-mechanical advantage in parameter estimation
   Mohamed Sahbani, Swetamber Das, and Jason R. Green

In Review

1. Force Geometry and Irreversibility in Nonequilibrium Dynamics
   Erez Aghion and Swetamber Das (2026)
   Abstract

   Recent experiments have revealed heterogeneous dissipation in optically trapped systems, often anticorrelated with local positional fluctuations, exposing a structural gap in the scalar stochastic thermodynamic description. While the conventional scalar framework successfully quantifies dissipation through currents and entropy production rates, it does not reveal the underlying vectorial force geometry that shapes spatial dissipation patterns. Here, we bridge this gap by identifying force geometry as an organizing principle for nonequilibrium thermodynamics and introducing force alignment as a geometric determinant of irreversibility. We show that entropy production depends not only on force magnitudes but also on the relative orientation between deterministic driving forces and entropic gradients, vanishing only under exact anti-alignment with matched magnitudes. We formalize this geometric alignment through a time-dependent force-correlation coefficient, quantifying the relative orientation between the forces. This yields an instantaneous geometric lower bound on entropy production that remains valid even when force magnitudes are matched. For overdamped dynamics, perfect anti-alignment defines a thermodynamic stall where net transport vanishes and the lower bound on entropy production is saturated. This force-level perspective provides a structural explanation for the experimentally observed fluctuation-dissipation anticorrelation and nonuniform dissipation. We construct geometric control charts for both constant dragging and sinusoidal driving protocols, explicitly locating experimental operating points within this force-space representation. Together, these results position force geometry as a unifying structural perspective on irreversibility, spanning active biological systems, microrheology, and naturally extending to underdamped dynamics.

   [arXiv:2603.29416]
2. Geometry- and inertia-limited chaotic growth in classical many-body systems
   Swetamber Das (2026)
   Abstract

   Chaotic instability in many-body systems is commonly quantified by the largest Lyapunov exponent, yet general constraints on its magnitude in classical interacting systems remain poorly understood. Here we establish explicit, Hamiltonian-specific upper bounds on the largest Lyapunov exponent for classical many-body systems with local interactions. These bounds arise from instantaneous stability constraints on the Hamiltonian flow and are expressed in terms of inertial scales and the curvature of the interaction potential. We show that they naturally separate into two qualitatively distinct classes: non-violable bounds, controlled by worst-case local curvature scales and inertia and insensitive to spatial structure, and ergodic ceilings, which retain spectral information and encode collective modes and finite-size effects under generic dynamical evolution. For a paradigmatic one-dimensional coupled-rotor chain (Josephson junction array), the ergodic ceiling admits a closed analytic form and produces a dynamically inaccessible region for sustained chaotic growth in the Lyapunov exponent--energy plane, which we confirm numerically. In contrast to non-violable estimates, the ergodic ceiling yields a sharper constraint on chaotic growth by capturing collective suppression mechanisms absent at the level of local curvature alone. Remarkably, in the thermodynamic limit the ergodic ceiling asymptotically approaches an inertial ceiling that limits sustained Lyapunov growth, becoming independent of temperature and interaction strength. While classical systems do not admit universal chaos bounds, our results identify a broad class of natural Hamiltonian systems in which chaotic growth is inherently limited by inertia and interaction geometry, thereby setting a minimal microscopic timescale for long-time loss of memory of initial conditions.

   [arXiv:2602.21149]
3. Dynamical system analysis of quantum tunneling in an asymmetric double-well potential
   Swetamber Das and Arghya Dutta (2025)
   [arXiv:2510.24100]

Published/Accepted

1. Phase space volume preserving dynamics for non-Hamiltonian systems
   Swetamber Das and Jason R. Green (2026)
   Chaos 36, 043120 (2026). [arXiv:2511.04960]
2. Phase-space contraction rate for classical mixed states
   Mohamed Sahbani, Swetamber Das, and Jason R. Green (2025)
   Phys. Rev. E 111, 054130.
3. Spectral bounds on Lyapunov exponents and entropy production in differentiable dynamical systems
   Swetamber Das and Jason R. Green (2025)
   J. Phys. A: Math. Theor. 2025 58(3) 035003.
4. Maximum speed of dissipation
   Swetamber Das and Jason R. Green (2024)
   Phys. Rev. E (Letter) 109, L052104.
5. Observing the dynamics of an electrochemically driven active material with liquid electron microscopy
   Wyeth S. Gibson, Justin T. Mulvey, Swetamber Das, Serxho Selmani, Jovany G. Merham, Alex Rakowski, Eric Schwartz, Allon I. Hochbaum, Zhibin Guan, Jason R. Green, and Joseph P. Patterson (2024)
   ACS Nano 18 (18), 11898–11909. (theory support)
6. Classical Fisher information for differentiable dynamical systems
   Mohamed Sahbani, Swetamber Das, and Jason R. Green (2023)
   Chaos 33, 103139. Featured Article.
7. Speed limits on deterministic chaos and dissipation
   Swetamber Das and Jason R. Green (2023)
   Phys. Rev. Res. (Letter) 5(1):L012016.
8. Density matrix formulation of dynamical systems
   Swetamber Das and Jason R. Green (2022)
   Phys. Rev. E 106, 054135.
9. Tunability enhancement of gene regulatory motifs through competition for regulatory protein resources
   Swetamber Das and Sandeep Choubey (2020)
   Phys. Rev. E 102, 052410.
10. Power-law trapping in the volume-preserving Arnold-Beltrami-Childress Map
    Swetamber Das and Arnd Bäcker (2020)
    Phys. Rev. E 101, 032201.
11. Controlling synchronization in coupled area-preserving maps using stickiness
    Swetamber Das (2019)
    Accepted in AIP Advances.
12. Transport, diffusion, and energy studies in the Arnold-Beltrami-Childress map
    Swetamber Das and Neelima Gupte (2017)
    Phys. Rev. E 96, 032210.
13. Synchronization, phase slips and coherent structures in area-preserving maps
    Swetamber Das, Sasibhusan Mahata, and Neelima Gupte (2017)
    Indian Academy of Sciences Conference Series 1, 205-212.
14. Synchronization in area-preserving maps: Effects of mixed phase space and coherent structures
    Sasibhushan Mahata, Swetamber Das, and Neelima Gupte (2016)
    Phys. Rev. E 93, 062212.
15. Dynamics of impurities in three-dimensional-volume preserving map
    Swetamber Das and Neelima Gupte (2014)
    Phys. Rev. E 90, 012906.
16. On an Asymptotic Case of the Complex Lorenz Model
    Swetamber Das (2010)
    Proceedings of International Conference on Applied Physics & Mathematics, Kuala Lumpur, Malaysia (May 7–10, 2010), 579-583.
    Published by IEEE