A geometrically controlled rigidity transition in a model for confluent 3D tissues

The origin of rigidity in disordered materials is an outstanding open problem in statistical physics. Previously, a class of 2D cellular models has been shown to undergo a rigidity transition controlled by a mechanical parameter that specifies cell shapes. Here, we generalize this model to 3D and find a rigidity transition that is similarly controlled by the preferred surface area: the model is solid-like below a dimensionless surface area of $s_0^\ast\approx5.413$, and fluid-like above this value. We demonstrate that, unlike jamming in soft spheres, residual stresses are necessary to create rigidity. These stresses occur precisely when cells are unable to obtain their desired geometry, and we conjecture that there is a well-defined minimal surface area possible for disordered cellular structures. We show that the behavior of this minimal surface induces a linear scaling of the shear modulus with the control parameter at the transition point, which is different from the scaling observed in particulate matter. The existence of such a minimal surface may be relevant for biological tissues and foams, and helps explain why cell shapes are a good structural order parameter for rigidity transitions in biological tissues.Comment: 6 pages main text + 13 pages appendix, 3 main text figures + 6 appendix figure

India and South Asia in Germany : the world according to GNARP: prospects for transatlantic library partnership in the digital age ; 6th scientific symposium Frankfurt a. M.

Seit 2005 ist die Bibliothek des Südasien-Instituts in Kooperation mit der UB Heidelberg Trägerin des DFG-geförderten Sondersammelgebiets Südasien. Damit hat sie von der UB Tübingen ein traditionsreiches Sondersammelgebiet übernommen, dessen Geschichte bis ins Jahr 1949 zurückreicht. Der Vortrag wird zum Einen einen kurzen Überblick über den historischen Kontext des SSG Südasien geben und zum Anderen über Neuentwicklungen, wie z.B. die Virtuelle Fachbibliothek Südasien, die in den letzten zwei Jahren an der Bibliothek des Südasien-Instituts aufgebaut wurde. Vor diesem Hintergrund soll vor allem das Kooperationspotential im Bereich digitaler Informationsressourcen beleuchtet werden

Dynamical decoupling of spin ensembles with strong anisotropic interactions

Ensembles of dopants have widespread applications in quantum technology. The miniaturization of corresponding devices is however hampered by dipolar interactions that reduce the coherence at increased dopant density. We theoretically and experimentally investigate this limitation. We find that dynamical decoupling can alleviate, but not fully eliminate, the decoherence in crystals with strong anisotropic spin-spin interactions. Our findings can be generalized to all quantum systems with anisotropic g-factor used for quantum sensing, microwave-to-optical conversion, and quantum memory.Comment: Second version of the manuscript contains additional measurements, in which dynamical decoupling in the absence of strong spin-spin interactions is demonstrate