Quasi-Normal Modes of a Natural AdS Wormhole in Einstein-Born-Infeld Gravity

We study the matter perturbations of a new AdS wormhole in (3+1)-dimensional Einstein-Born-Infeld gravity, called "natural wormhole", which does not require exotic matters. We discuss the stability of the perturbations by numerically computing the quasi-normal modes (QNMs) of a massive scalar field in the wormhole background. We investigate the dependence of quasi-normal frequencies on the mass of scalar field as well as other parameters of the wormhole. It is found that the perturbations are always stable for the wormhole geometry which has the general relativity (GR) limit when the scalar field mass m satisfies a certain, tachyonic mass bound m^2 > m^2_* with m^2_* < 0, analogous to the Breitenlohner-Freedman (BF) bound in the global-AdS space, m^2_BF = 3 Lambda/4. It is also found that the BF-like bound m^2_* shifts by the changes of the cosmological constant Lambda or angular-momentum number l, with a level crossing between the lowest complex and pure-imaginary modes for zero angular momentum l = 0. Furthermore, it is found that the unstable modes can also have oscillatory parts as well as non-oscillatory parts depending on whether the real and imaginary parts of frequencies are dependent on each other or not, contrary to arguments in the literature. For wormhole geometries which do not have the GR limit, the BF-like bound does not occur and the perturbations are stable for arbitrary tachyonic and non-tachyonic masses, up to a critical mass m^2_c > 0 where the perturbations are completely frozen.Comment: Added comments and references, Accepted in EPJ

Computational and Analytical Modelling of Droplet-Macroion Interactions

Charged droplets involving macromolecules undergo distinct disintegration mechanisms and shape deformations as a consequence of droplet-macroion interactions. Three general classes of droplet-macroion interactions that have been identified in the Consta group are: contiguous extrusion of a linear macroion from a droplet, pearl-necklace droplet conformations, and star -shaped droplets. This dissertation probes in a systematic manner the onset and various outcomes of macroion-droplet interactions, using atomistic molecular dynamics and realistic examples of solvent and macromolecules. When the charge-squared-to-volume ratio of a droplet is below but near a threshold value, certain flexible macromolecules, such as poly(ethylene glycol), extrude from a droplet, induced by the charging of the macromolecules. An analytical model is constructed based on the simulation data to suggest that the droplet surface electric field may play a role in the extrusion of the macroion. The effect of different solvents is studied to show that the final charge state of the macroion is determined by complicated macromolecule-ion-solvent interactions. Beyond this threshold, the charge-induced instability evolves to certain droplet deformations that lead to new stable states. These include pear-shaped lobes of solvent at the termini of a linear macroion, such as unstructured proteins, and conical protrusions of dielectric solvent surrounding a macroion regardless of its shape. In the former, such droplet conformation may emerge due to the interplay of a number of factors, subject to the constraint that each sub-droplet should be below a certain charge-squared-to-volume ratio. In the latter, the overall star geometry is determined by the amount of the macroion charge. As the next level of system complexity, different factors that affect the stability of weak transient protein complexes in droplets are examined. A multiscale approach is devised to model a protein in an evaporating droplet where its acidity constantly changes. A methodology is then developed to compute the dissociation rate and the error in the dissociation constant measured in mass spectrometry experiments. A possible charging mechanism of the macroion due to the star structure of solvent is also proposed

Symplectic Reduction and Symmetry Algebra in Boundary Chern-Simons theory

We derive the Kac-Moody algebra and Virasoro algebra in Chern-Simons theory with boundary by using the symplectic reduction method and the Noether procedures.Comment: References are adde

Phytate degradation by Leuconostoc mesenteroides KC51 cultivation in soymilk

The phytate-degrading activity of Leuconostoc mesenteroides KC51 isolated from Kimchi was evaluated. When the phytase activity was measured in cultured broth on Lactobacilli MRS medium, theactivity was detected in harvested cell suspension but not in the extracellular medium. The optimum pH was determined to be pH 5.5. L. mesenteroides KC51 cultivation in autoclaved soymilk resulted in asignificant reduction of phytate content. After 9 h, around 47% of phytate had disappeared, and phytate content tended to stabilize around 50% of its initial value at the end of the 18 h fermentation. And decrease of phytate content was associated with L. mesenteroides KC51 cell growth duringfermentation