Galaxies

This paper proposes a non-smooth controller optimization method and shows the results of ongoing research on the implementation of this method for gravitational-wave applications. Typical performance requirements concerning these type of suspensions are defined in terms of both ${\mathcal{H}}_2$- and ${\mathcal{H}}_{\infty }$-type constraints. A non-smooth optimization approach is investigated, which allows the use of non-convex cost functions that are often a result of mixed ${\mathcal{H}}_2/{\mathcal{H}}_{\infty }$ optimization problems. Besides the controller, the distribution of the actuation is integrated with the optimization to investigate the feasibility of simultaneous controller and actuator optimization. The results demonstrate that the proposed non-smooth optimization method is able to find suitable solutions for the control and actuator distribution that satisfy all required performance and design constraints.

We continue scientific scrutiny of the DESI dynamical dark energy (DE) claim by explicitly demonstrating that the result depends on the analysis pipeline. Concretely, we define a likelihood that converts the $w_0{w}_a$CDM model back into the (flat) $\Lambda$CDM model, which we fit to DESI constraints on the $\Lambda$CDM model from DR1 Full-Shape (FS) modeling and BAO. We further incorporate CMB constraints. Throughout, we find that $w_0$ and $w_a$ are within $1\sigma$ of the $\Lambda$CDM model. Our work makes it explicit that, in contrast to DR1 and DR2 BAO, there is no dynamical DE signal in FS modeling, even when combined with BAO and CMB. Moreover, one confirms late-time accelerated expansion today at ≳3.4$\sigma$ in FS modeling + BAO. On the contrary, DR1 and DR2 BAO fail to confirm $q_0<0$ under similar assumptions. Our analysis highlights the fact that trustable scientific results should be independent of the analysis pipeline.

Grand-design spiral structures typically emerge in N-body simulations of disk galaxies as barred-spiral configurations forming during the early evolutionary stages of the system. In this study, we explore the dynamical conditions that allow for the formation and sustained presence of a non-barred, bisymmetric grand-design spiral pattern in fully self-consistent N-body models over considerable time periods. We present a model in which such non-barred morphologies persist for approximately 2.5 Gyr. The simulation is carried out using a standard implementation of the GADGET-3 code, incorporating both stellar and gaseous components in the disk and embedding them within a live dark matter halo. A characteristic feature of the simulation is that during its normal spiral grand-design phase the disk remains submaximal. Star formation is active throughout the model’s evolution. Analysis of the resulting morphology indicates that dominant inner, symmetric spiral arms extend between the inner Lindblad resonance (ILR) and the radial inner 4:1 resonance. This structure is evident in both the stellar and gaseous components, exhibiting extensions and bifurcations consistent with predictions from orbital theory.