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Yikun Ren

Publications and source records attributed to Yikun Ren.

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Mesoscopic MCT theory resolves Giant Non-Gaussian Parameter and Flory's conjecture

Extending Prigogine's ideas to the interior of the system, we generalize mode-coupling theory from a microscopic to a mesoscopic formulation by incorporating the non-equilibrium eigen-phase. The resulting framework resolves two long-standing puzzles in glass transition physics with an error less than 0.01 against experiments: (i) the giant non-Gaussian parameter $\alpha_{2} \sim 1-10$ which exceeds standard MCT predictions (only 0.1) by two orders of magnitude; (ii) the universal WLF constant $C_{1}=17 \ln 10 /(3 \sqrt{42}-19) \approx 16.7$, empirically observed for seven decades but never derived from first principles(e.g. Adam-Gibbs $C_{1}=8.5$, while other theories are off by more than a factor of two). These results establish mesoscopic MCT as a measurable foundation for non-equilibrium thermodynamics, unifying dynamic heterogeneity and thermodynamic universality in glass-forming systems.

cond-mat.stat-mech

Non-Equilibrium Thermodynamics Framework to Address the Glass Transition

When the center of fluctuations, i.e., the nonequilibrium eigenphase, undergoes transformation, there emerge critical parameters that demonstrate insensitivity to fluctuation perturbations and even independence from the molecular physical properties of the system, while exhibiting pronounced efficacy in governing phase transition dynamics.In the context of polymer glass transitions, Flory's conjecture (or C1 in the WLF equation) represents such a longstanding yet unresolved critical parameter. To address this issue, we replace entropy variation with a sequence of microstates and provide an analytically tractable statistical description of non-ergodicity. Our theory rigorously demonstrates that reaching the critical parameter is a necessary condition for non-equilibrium transitions to occur. Due to correlations between the eigenphase's entropy and energy in non-equilibrium systems, any system with a given intrinsic structure inherently possesses a critical parameter that represents the limiting deviation from equilibrium at any temperature. Flory's conjecture exemplifies this, with our new theoretical critical void ratio at the glass transition boundary calculated to be 2.6%, which closely matches experimental observations of 2.5%-2.6% over the past 50 years.

cond-mat.stat-mech