Browsing by Author "Rudra, Sumitra"

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    Critical behavior of magnetic polymers on the three-dimensional Sierpi?ski Gasket
    (American Physical Society, 2023) Rudra, Sumitra; Foster, Damien Paul; Kumar, Sanjay
    We present the (numerically) exact phase diagram of a magnetic polymer on the Sierpi?sky gasket embedded in three dimensions using the renormalization group method. We report distinct phases of the magnetic polymer, including paramagnetic swollen, ferromagnetic swollen, paramagnetic collapsed, and ferromagnetic collapsed states. By evaluating critical exponents associated with phase transitions, we located the phase boundaries between different phases. If the model is extended to include a four-site interaction which disfavors configurations with a single spin of a given type, we find a rich variety of critical behaviors. Notably, we uncovered a phenomenon of reentrance, where the system transitions from a collapsed (paramagnetic) state to a swollen (paramagnetic) state followed by another collapse (paramagnetic) and ultimately reaching a ferromagnetic collapsed state. These findings shed new light on the complex behavior of (lattice) magnetic polymers. � 2023 American Physical Society.
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    Force-induced melting of DNA hairpin: Unfolding pathways and phase diagrams
    (American Physical Society, 2023) Rudra, Sumitra; Chauhan, Keerti; Singh, Amit Raj; Kumar, Sanjay
    Using the exact enumeration technique, we have studied the force-induced melting of a DNA hairpin on the face centered cubic lattice for two different sequences which differ in terms of loop closing base pairs. The melting profiles obtained from the exact enumeration technique is consistent with the Gaussian network model and Langevin dynamics simulations. Probability distribution analysis based on the exact density of states revealed the microscopic details of the opening of the hairpin. We showed the existence of intermediate states near the melting temperature. We further showed that different ensembles used to model single-molecule force spectroscopy setups may give different force-temperature diagrams. We delineate the possible reasons for the observed discrepancies. � 2023 American Physical Society.