Seminars

Neutrophils representing major cell types of the innate immune system are the most abundant leukocytes in circulation and combat pathogens through distinctly regulated processes such as a) degranulation and oxidative burst; b) phagocytosis and c) producing extracellular traps. Neutrophils upon activation with a wide variety of pathogens expel DNA bound with histones and granular proteins to form extracellular traps (NETs). High concentrations of antimicrobial effectors within these DNA lattices serve as a platform to activate pro-inflammatory mediators, immobilize and kill the pathogens and simultaneously clear the infection. Neutrophil recruitment at inflammatory sites and failure undergoing apoptosis and impaired clearance of dead neutrophils along with NETs components results in host tissue damage and release of pro-inflammatory cytokines. This indicates the existence of checkpoints that regulate neutrophil kinetics and fate and inability to regulate these checkpoints overt in extensive host tissue damage leading to organ dysfunction and diseases. Neutrophil mediated inflammation has been described in various diseases including Type 2 Diabetes (T2D), obesity, atherosclerosis, cancer, autoimmune diseases and inter alia. Exploring systems biology approaches using cell culture, rodent and clinical models of T2D, sepsis and stroke, our team aims to understand how NETs and associated mechanisms play significant role in T2D induced recurrent infections and vascular complications.

The use of quantum resources in the work extraction from a quantum system is an emerging research topic. Recently, [arXiv:2602.22893] established the necessity of measurement coherence for obtaining advantage in work extraction from an unknown isolated quantum system. However, a quantitative relation between the magnitude of this advantage and established measures of measurement coherence is missing. Here, we establish such a connection by introducing a faithful operational quantifier of the work advantage provided by a measurement. We show that measurement coherence is necessary and sufficient for a positive advantage, and derive upper and lower bounds in terms of the robustness of measurement coherence and an l∞ norm based coherence measure respectively. Finally, we examine this quantifier of advantage from the resource theoretic perspective. Our results provide an operational characterisation of measurement coherence as a resource for work extraction and reveal a nontrivial relation between its resource content and thermodynamic value. Paper link: https://arxiv.org/abs/2609.18735 Join Zoom Meeting https://zoom.us/j/91431488789 Meeting ID: 914 3148 8789 Passcode: 009545

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Quantum many-body scars (QMBS) provide a route to weak ergodicity breaking in isolated many-body systems. Unlike conventional mechanisms for the failure of thermalization, such as integrability or many-body localization, where atypical behavior pervades the entire spectrum, QMBS systems harbor only a small, measure-zero set of nonthermal eigenstates embedded within an otherwise thermalizing bulk. Conventionally, these atypical states ($scar$ states) are distinguished by their anomalously low entanglement entropy relative to nearby thermal eigenstates. When a system is initialized in a state with significant overlap onto this scarred subspace, its subsequent dynamics evade rapid thermalization, instead producing long-lived coherent oscillations in local observables. QMBS have now been identified across a diverse range of platforms, including lattice models, Floquet systems, and various quantum simulators. Nevertheless, a systematic microscopic understanding of how scar eigenstates arise and how they can be analytically constructed remains incomplete. The central aim of this dissertation is to use interacting spin models as a concrete setting to investigate the explicit construction, algebraic organization, and entanglement structure of a hierarchy of QMBS, including states that lie well beyond the low-entanglement paradigm. The first part of this thesis studies the spin-$1$ Kitaev chain, where conserved bond parity operators fragment the Hilbert space into exponentially many dynamically disconnected sectors. Beyond the previously identified sector that maps exactly onto the paradigmatic PXP model, we show that pronounced scarred dynamics also occur in other sectors. Suitably chosen product states in these sectors display strong and long-lived fidelity revivals, which we analyze using the forward-scattering approximation, revealing how constrained Hilbert spaces give rise to robust non-ergodic dynamics. We then develop a general algebraic construction of exact zero-energy eigenstates with volume-law entanglement in a large class of spin chains with periodic boundary conditions. These states are formed by entangled dimers on antipodal sites and arise in the middle of the spectrum for models including the transverse-field Ising model, the PXP model, and spin-$S$ $XY$ and Kitaev chains. Although they exhibit thermal expectation values for all local observables, they remain atypical under suitable nonlocal few-body probes, thereby extending the notion of scar-like eigenstates decisively beyond the low-entanglement paradigm. The construction generalizes to spin models on arbitrary graphs in higher dimensions. Finally, we revisit the spin-$1$ $XY$ chain and construct new families of exact scars within its extensively degenerate zero-energy manifolds, arising from the interplay between $U(1)$ magnetization conservation and chiral symmetries. These include interference-protected Fock-space-cage-like states, volume-entangled towers, and mirror-dimer states. Using the commutant algebra framework, we show that these states are simultaneous eigenstates of non-commuting local operators, providing a unifying algebraic organizing principle and systematic routes to identifying and classifying QMBS in generic many-body systems.

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A common envelope (CE) event occurs when a giant star, consisting of a dense core and bloated envelope, engulfs a much smaller binary companion. This leads to the core and companion inspiralling inside a shared envelope, to which they transfer orbital energy and angular momentum via gravitational drag (gas dynamical friction). This can result in a merger between the core and companion, which may produce a luminous red nova, or the ejection of the envelope, resulting in a stable short-period `post-CE' binary. Global three-dimensional hydrodynamical simulations can be used to better understand the key physical processes that govern CE evolution. We are currently focusing on evaluating the applicability of various drag force models from the literature by comparing their predictions with the drag force measured from the simulations. We find that certain analytic drag models can reproduce the simulation results with remarkable accuracy. Due to their much lower computational cost, one-dimensional spherically symmetric simulations may be better suited for certain science goals, but should reliably reproduce key outcomes of the 3D simulations. I will discuss our ongoing effort to develop global 1D hydrodynamical CE simulations, which involves deploying the analytic models mentioned above in the 1D simulations and comparing 1D and 3D simulations at each stage of model development.

TBA