http://hdl.handle.net/2289/22 2026-04-04T12:45:50Z http://hdl.handle.net/2289/8686 Title: Anisotropic active Brownian particle in two dimensions under stochastic resetting Authors: Ghosh, Anirban; Mandal, Sudipta; Chaki, Subhasish Abstract: We study the dynamical behavior of an anisotropic active Brownian particle subjected to various stochastic resetting protocols in two dimensions. The motion of shape-asymmetric active Brownian particles in two dimensions leads to anisotropic diffusion at short times, whereas rotational diffusion causes the transport to become isotropic at longer times. We have considered three different resetting protocols: (1) complete resetting, when both position and orientation are reset to their initial states, (2) only the position is reset to its initial state, and (3) only orientation is reset to its initial state. We reveal that orientational resetting sustains anisotropy even at late times. When both the spatial position and orientation are subject to resetting, a complex position probability distribution forms in the steady state. This distribution is shaped by factors such as the initial orientation angle, the anisotropy of the particle, and the resetting rate. We have calculated the exact expressions for mean-square displacements using a renewal approach for different resetting protocols and numerically verified the analytical results. When only the translational degrees of freedom are reset, while the particle's orientation evolves naturally, the steady state no longer depends on particle asymmetry. In contrast, if only the orientation is reset, the long-term probability distribution becomes Gaussian, using an effective diffusion tensor—containing nondiagonal elements—defined by the resetting rate. More broadly, the interaction between translational and rotational dynamics, in combination with stochastic resetting, produces distinct behaviors at late times that are absent in symmetric particles. Given recent progress in experimental resetting techniques, these results could be highly useful for controlling asymmetric active colloids, such as in self-assembly applications. Description: Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations) 2026-01-29T00:00:00Z http://hdl.handle.net/2289/8678 Title: From chiral topological dynamics to chiral topological amplification: Real versus imaginary parameters in a Hermitian bosonic chain Authors: Estake, Kiran Babasaheb; Vishnu, T R; Roy, Dibyendu Abstract: We propose a Hermitian quadratic bosonic model (QBH) whose dynamical matrix exhibits distinct topological and dynamical phenomena depending on whether the hopping and pairing amplitudes are real or purely imaginary. In the real-parameter regime, the dynamical matrix is unitarily equivalent to four decoupled copies of the sublattice-symmetric non-Hermitian Su-Schrieffer-Heeger (nSSH2) model, thereby inheriting its topological phases and energy spectrum, including the Möbius phase, a gapless topological phase with fractional winding number, having no Hermitian counterpart. We show that the dynamics generated by the QBH Hamiltonian naturally reproduces non-Hermitian time evolution, without invoking nonlinear Schrödinger dynamics or ad hoc normalization. It is demonstrated by analytically calculating the Loschmidt amplitude and computing the dynamical topological order parameter under periodic boundary conditions, which displays a distinct chiral response in the Möbius phase. In contrast, when the hopping and pairing terms are taken to be purely imaginary, the dynamical matrix becomes unitarily equivalent to a different version of the sublattice-symmetric non-Hermitian Su-Schrieffer-Heeger (nSSH1) model that supports only two topological phases, trivial and nontrivial, and the Möbius phase disappears. The latter system exhibits sublattice-dependent chiral amplification under open boundary conditions. We show that this amplification arises from the nontrivial topology of the dynamical matrix, establishing a clear link between topological phase and amplification behavior in the imaginary-parameter regime. Description: Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations) 2025-12-16T00:00:00Z http://hdl.handle.net/2289/8676 Title: Dynamically generated correlations in a trapped bosonic gas via frequency quenches Authors: Mesquita, Nikhil; Kulkarni, Manas; Majumdar, Satya N; Sabhapandit, Sanjib Abstract: We study a system of N noninteracting bosons in a harmonic trap subjected to repeated quantum quenches, where the trap frequency is switched from one value to another after a random time duration drawn from an exponential distribution. Each cycle contains two steps: (i) changing the trap frequency to enable unitary evolution under a Hamiltonian, and (ii) reapplying the original trap at stochastic times to cool the gas back to its initial state. This protocol effectively makes it an open quantum system and drives it into a unique nonequilibrium steady state (NESS). We analytically and numerically characterize the NESS, uncovering a conditionally independent and identically distributed (CIID) structure in the joint probability density function (JPDF) of the positions. The JPDF in the CIID structure is a product of Gaussians with a common random variance, which is then averaged with respect to its distribution, making the JPDF non-factorizable, giving rise to long-range emergent dynamical correlations. The average density profile of the gas shows significant deviations from the initial Gaussian shape. We further compute the order and the gap statistics, revealing universal scaling in both bulk and edge regimes. We also analyze the full counting statistics, exposing rich parameter-dependent structure. Our results demonstrate how stochastic quenches can generate nontrivial correlations in quantum many-body systems Description: Open Access. Also available at arXiv.org (one of the alternative locations) 2025-12-05T00:00:00Z http://hdl.handle.net/2289/8666 Title: Radiation Reaction in Electrodynamics and General Relativity Authors: Iyer, B R Abstract: It is a privilege and pleasure to be invited to contribute an article to the JVN Fest. When I received this invitation, I tried to go back along my world-line and look for intersections with Jayant. A popular article by Jayant Narlikar entitled ’The Arrow of Time’ [1] mystified and fascinated me. It roused an almost romantic longing and an urge to appreciate, if not investigate, such basic problems. Probably it was these subconscious fantasies that propelled me towards physics and eventually, general relativity. I still remember the first time I heard a public talk by Narlikar on Cosmology after his return to India. It was at the Homi Bhabha auditorium of TIFR in 1972. The hall was overflowing and I heard his (favorite?) joke on the mathematician, physicist and astronomer for the first time. I heard it again this year in his talk at the Academy and was impressed by his un-apologetic use of it to make his point! I met Jayant Narlikar at the Einstein centenary symposium in Ahmedabad in 1979 and his interests then included scale invariant cosmology (with Ajit Kembhavi) and black holes as tachyon detectors (with Sanjeev Dhurandhar). He carried his fame lightly, was unassuming and though he was not very talkative, he felt very approachable. When I finished my Ph.D. with Arvind Kumar at the Bombay University, I could not get a post doc at TIFR or work with Jayant, since he was away that particular year. Over the last sixteen years, I have had much overlap with Jayant in the organization of Relativity related activities in India. There is much to admire in Jayant and emulate. His time management, missionary zeal to the popularization of science, vision and hard work, pedagogic skills, fervor for the non-standard and ability to play devil’s advocate in his research almost as a point of faith. In addition to the above, personally, I also admire him for his ability to take criticism and his democratic mode of functioning. Description: Restricted Access 2000-01-01T00:00:00Z