Ultracold Bose gases are many-body systems with well-defined particle interactions that may serve as models for interacting quantum fields. The impact of virtual excitations is studied in the spatial transition zone created by a soft confinement potential that separates a degenerate ideal gas from a dense quasi-condensate. We compute within Bogoliubov theory the contribution of quasi-particles to the surface energy at zero temperature.

Bacterial cells exhibit a diverse array of shapes and sizes, largely influenced by their cell walls in conjunction with cytoskeletal proteins and internal turgor pressure. The present study develops a theoretical framework for modeling the shape dynamics of actively expanding bacterial cell walls, grounded in the concept of minimal energy dissipation. In the context of a bacterial cell wall, dissipative forces are generated through the insertion of peptidoglycan (PG) strands, while driving forces stem from alterations in mechanochemical energy, crucial for sustaining the cell wall's shape. The interplay between mechanical and chemical energies facilitates the evaluation of the free energy landscape and helps in predicting the homeostasis of the bacterial cell size. The size limit derived through linear stability analysis (LSA) of a model system accurately mirrors the phase diagram produced by the theoretical model. Nonetheless, given the cell wall's intricate molecular architecture, a more detailed constitutive model is expected to provide more precise quantitative insights.

Defining low-dimensional reaction coordinates is crucial for analyzing the dynamics of complex systems and for comparison with experiments. The maximal value of the transition-path probability along the reaction coordinate , is a common estimator for reaction-coordinate quality by comparing to the theoretical maximal value of 1/2 in the overdamped Markovian limit. We show by analytical arguments and simulations that for non-Markovian dynamics is non-monotonic as a function of the memory time and exceeds 1/2 for long memory time. This disqualifies as a criterion for reaction coordinate quality.

In this work, we propose a theoretical model and validate it with finite element simulations for voltage-controlled hydrogel lenses made from soft materials. The model is built by examining the force equilibrium between the dielectric elastomer membrane and the hydrogel layer, allowing us to predict changes in focal length under applied voltage. Finite element simulations are used to corroborate the model, with results closely matching theoretical predictions. To ensure real-world applicability, the simulation data is also compared with experimental measurements. We observed slight deviations between the experimental lens shapes and the theoretical model due to gravitational effects on the hydrogel. To account for this, we developed a refined finite element model that accurately simulates the experimental conditions, showing strong alignment with both experimental data and theoretical predictions.

We discuss, at leading order in ℏ, the quantum mechanics of a specific realization in phase space of the Yang model describing noncommutative geometry in a curved background. In particular, we show how the deformation of the Heisenberg uncertainty relation crucially depends on the signs of the coupling constants of the model. We also discuss the dynamics of the free particle and of the harmonic oscillator. Also in this case the results depend on the signs of the coupling constants.

The dependence of the equilibrium contact separation for a nanoswitch operated by the van der Waals (Casimir), exchange repulsive, electric and elastic forces on the surface roughness and the parameters of a transmitted signal is investigated. The involved forces are calculated using the Lifshitz theory and the method of additive summation of the interatomic potentials for three different models of surface roughness. It is shown that the depth of the minimum in the sum of the van der Waals and exchange forces decreases with increasing roughness amplitudes. According to our results, in the presence of the transmitted signal the nanoswitch with the appropriately chosen operation voltage preserves its functionality with minor shifts in the equilibrium positions of contact separation.

Measurement of the Casimir forces at distances smaller than 50 nm is a complicated problem. The method of adhered cantilever does not suffer from loss of stability at short distances and was used recently to measure the adhesion energy due to the dispersion forces with a precision of 10%. In this paper the most important source of errors related to inhomogeneity of the thickness of the cantilevers is discussed. Analytical expressions for the shape of an inhomogeneous cantilever and the adhesion energy are derived. It is demonstrated that monitoring of the cantilever thickness along its length allows five times improvement of the precision. A small twisting of the cantilevers is indicated as an additional source of important errors. This parameter controls the precision of equilibrium average distance between the surfaces and the true adhesion energy between parallel plates.

This paper investigates the Heisenberg model across diverse network topologies, and studying the variation of entanglement measures across these network topologies. Various network types are introduced along with their properties. An algorithm for generating networks using the Watts-Strogatz small world model is presented, focusing on the transition from regular to random networks via the small-world regime. The objective is to explore the entanglement landscape of the Heisenberg model across these network configurations, using extensive numerics. Insights into entanglement behaviour using graph theoretic properties such as local average clustering coefficient and the number of edge cuts during bipartitioning are provided. This opens up ways to analyze such complicated network topologies using entanglement.

Unlike Newtonian fluids, which typically favour the squeezing mode for droplet formation, in this work, we unveil that this mode is entirely absent for shear-thinning fluids. Following experimental observations as well as numerical investigations, we establish the reason for this absence by analyzing the evolution of viscous shear stress at the droplet interface. We identify a threshold flow ratio of (where and Q c represent the flow rates of the dispersed and continuous phases), below which any subtle variations in favour the dripping mode. However, beyond this threshold, increases sharply, shifting the flow mode directly to jetting and bypassing squeezing mode. Our study further reveals how varying shear-thinning degree influences jet development and flow transitions, as illustrated through a flow regime map. We believe these insights will offer valuable guidance for developing lab-on-a-chip platforms for shear-thinning droplet formation, largely used in applications, including biochemistry, material synthesis, and emulsification.

Modelling fluid turbulence using a “skeleton” of coherent structures has traditionally progressed by focusing on a few canonical laboratory experiments such as pipe flow and Taylor-Couette flow. We here consider the stratified inclined duct, a sustained shear flow whose density stratification allows for the exploration of a wealth of new coherent and intermittent states at significantly higher Reynolds numbers than in unstratified flows. We automatically identify the underlying turbulent skeleton of this experiment with a data-driven method combining dimensionality reduction and unsupervised clustering of shadowgraph visualisations. We demonstrate the existence of multiple types of turbulence across parameter space and intermittent cycling between them, revealing distinct transition pathways. With a cluster-based network model of intermittency we uncover patterns in the transition probabilities and residence times under increasing levels of turbulent dissipation. Our method and results pave the way for new reduced-order models of multi-physics turbulence.