Gaussian expansion analysis of a matrix model with the spontaneous breakdown of rotational symmetry

Recently the gaussian expansion method has been applied to investigate the dynamical generation of 4d space-time in the IIB matrix model, which is a conjectured nonperturbative definition of type IIB superstring theory in 10 dimensions. Evidence for such a phenomenon, which is associated with the spontaneous breaking of the SO(10) symmetry down to SO(4), has been obtained up to the 7-th order calculations. Here we apply the same method to a simplified model, which is expected to exhibit an analogous spontaneous symmetry breaking via the same mechanism as conjectured for the IIB matrix model. The results up to the 9-th order demonstrate a clear convergence, which allows us to unambiguously identify the actual symmetry breaking pattern by comparing the free energy of possible vacua and to calculate the extent of ``space-time'' in each direction.Comment: 23 pages, 20 figures, LaTe

Ionic Liquid Electrospray Thruster with Two-Stage Electrodes On Glass Substrate

2023 IEEE 36th International Conference on Micro Electro Mechanical Systems (MEMS), 15-19 Jan. 2023.This paper reports ion emission of an ionic liquid electrospray thrustor with two-stage electrodes made on glass substrate having through hole for low-cost micro/nano satellites. By using the two-stage electrodes, one for ion extraction and the other for acceleration, high and stable ion emission and propulsion force is obtained. The emitter array was fabricated on a silicon wafer and the electrodes were fabricated on both sides of a glass substrate. The ion emission test was conducted, and the emission current was observed successfully. Almost no ions were collected on the accelerator electrode and reached to the collector electrode, which demonstrates the advantage of the two-stage configuration

Formation of Si Nanowires by Direct Electrolytic Reduction of Porous SiO₂ Pellets in Molten CaCl₂

The effects of starting material and catalyst on the morphology of produced Si have been investigated for the direct electrolytic reduction of porous SiO₂ pellets in molten CaCl₂ at 1123 K. The Si nanowires (SiNWs) were produced using amorphous SiO₂ pellets with a tetrapod-like microstructure as the starting material, whereas plate-like Si was obtained from pellets made of spherical fumed SiO₂. The SiNWs showed irregular branching and a wide distribution of diameters as the electrolysis proceeded. On the other hand, elongated SiNWs were formed during the electrolysis of pellets comprised of Au nanoparticles (AuNPs) and tetrapod-like microstructured SiO₂ powder. This suggests that AuNPs work as catalysts for longitudinal nanowire growth in the present electrolytic process

Simple Fabrication of Silicon Nanowires by Zinc-Thermal Reduction of Silicon Tetrachloride at 773 K

This paper reports a simple Si nanowire (SiNW) production process based on zinc-thermal reduction of SiCl₄ in a sealed Pyrex® tube at 773 K. SiNWs with a diameter of about 300 nm were produced without any catalysts. The SiNWs consisted mainly of an amorphous phase, but also including a minor microcrystalline component. The introduction of Au nanoparticles to the reaction tube wall facilitated crystallization and resulted in the growth of thinner SiNWs. The typical diameter of these SiNWs was 10–20 nm. The simple apparatus and low operating temperature of this new process are advantageous in producing SiNWs on both industrial and laboratory scales

Preparation and electrical properties of Li–Si–Al–O–N ceramics

AbstractCeramic samples were synthesized by hot pressing mixtures of Li3N, Si3N4, AlN, Al2O3, and Li2CO3 with nominal compositions of LiSi2−xAlxOxN3−x (x=0–0.75) at 20MPa and 1773–2073K in a N2 atmosphere of 0.10MPa. The samples prepared with nominal compositions, x=0.25 and 0.50, showed electronic conductivities of 2.2 and 4.2Sm−1 at room temperature with activation energies of 3.8 and 3.9kJmol−1, respectively. Electronic conductive parts were detected in the sample of x=0.50 by conductive atomic force microscopy (AFM). In this sample, a glassy thin layer, having a Si/Al atomic ratio of 3.8, was observed between the grains of LiSi2−xAlxOxN3−x solid solution by high-resolution transmission electron microscopy (HRTEM). It was expected that the glassy phase of grain boundaries is an electronic conductive pathway besides the conductive parts observed by AFM

Convergence of the Gaussian Expansion Method in Dimensionally Reduced Yang-Mills Integrals

We advocate a method to improve systematically the self-consistent harmonic approximation (or the Gaussian approximation), which has been employed extensively in condensed matter physics and statistical mechanics. We demonstrate the {\em convergence} of the method in a model obtained from dimensional reduction of SU($N$) Yang-Mills theory in $D$ dimensions. Explicit calculations have been carried out up to the 7th order in the large-N limit, and we do observe a clear convergence to Monte Carlo results. For $D \gtrsim 10$ the convergence is already achieved at the 3rd order, which suggests that the method is particularly useful for studying the IIB matrix model, a conjectured nonperturbative definition of type IIB superstring theory.Comment: LaTeX, 4 pages, 5 figures; title slightly changed, explanations added (16 pages, 14 figures), final version published in JHE

Ultralow radiant exposure of a short-pulsed laser to disrupt melanosomes with localized thermal damage through a turbid medium

Shimojo Y., Nishimura T., Tsuruta D., et al. Ultralow radiant exposure of a short-pulsed laser to disrupt melanosomes with localized thermal damage through a turbid medium. Scientific Reports 14, 20112 (2024); https://doi.org/10.1038/s41598-024-70807-7.Short-pulsed lasers can treat dermal pigmented lesions through selective photothermolysis. The irradiated light experiences multiple scattering by the skin and is absorbed by abnormal melanosomes as well as by normal blood vessels above the target. Because the fluence is extremely high, the absorbed light can cause thermal damage to the adjacent tissue components, leading to complications. To minimize radiant exposure and reduce the risk of burns, a model of the melanosome-disruption threshold fluence (MDTF) has been developed that accounts for the light-propagation efficiency in the skin. However, the light-propagation efficiency is attenuated because of multiple scattering, which limits the extent to which the radiant exposure required for treatment can be reduced. Here, this study demonstrates the principle of melanosome disruption with localized thermal damage through a turbid medium by ultralow radiant exposure of a short-pulsed laser. The MDTF model was combined with a wavefront-shaping technique to design an irradiation condition that can increase the light-propagation efficiency to the target. Under this irradiation condition, melanosomes were disrupted at a radiant exposure 25 times lower than the minimal value used in conventional laser treatments. Furthermore, almost no thermal damage to the skin was confirmed through a numerical simulation. These experimental and numerical results show the potential for noninvasive melanosome disruption and may lead to the improvement of the safety of short-pulsed laser treatment